1	//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===//
2	//
3	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4	// See https://llvm.org/LICENSE.txt for license information.
5	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6	//
7	//===----------------------------------------------------------------------===//
8	//
9	// This contains code to emit Constant Expr nodes as LLVM code.
10	//
11	//===----------------------------------------------------------------------===//
12
13	#include "CGCXXABI.h"
14	#include "CGObjCRuntime.h"
15	#include "CGRecordLayout.h"
16	#include "CodeGenFunction.h"
17	#include "CodeGenModule.h"
18	#include "ConstantEmitter.h"
19	#include "TargetInfo.h"
20	#include "clang/AST/APValue.h"
21	#include "clang/AST/ASTContext.h"
22	#include "clang/AST/Attr.h"
23	#include "clang/AST/RecordLayout.h"
24	#include "clang/AST/StmtVisitor.h"
25	#include "clang/Basic/Builtins.h"
26	#include "llvm/ADT/STLExtras.h"
27	#include "llvm/ADT/Sequence.h"
28	#include "llvm/Analysis/ConstantFolding.h"
29	#include "llvm/IR/Constants.h"
30	#include "llvm/IR/DataLayout.h"
31	#include "llvm/IR/Function.h"
32	#include "llvm/IR/GlobalVariable.h"
33	#include <optional>
34	using namespace clang;
35	using namespace CodeGen;
36
37	//===----------------------------------------------------------------------===//
38	// ConstantAggregateBuilder
39	//===----------------------------------------------------------------------===//
40
41	namespace {
42	class ConstExprEmitter;
43
44	struct ConstantAggregateBuilderUtils {
45	CodeGenModule &CGM;
46
47	ConstantAggregateBuilderUtils(CodeGenModule &CGM) : CGM(CGM) {}
48
49	CharUnits getAlignment(const llvm::Constant *C) const {
50	return CharUnits::fromQuantity(
51	Quantity: CGM.getDataLayout().getABITypeAlign(Ty: C->getType()));
52	}
53
54	CharUnits getSize(llvm::Type *Ty) const {
55	return CharUnits::fromQuantity(Quantity: CGM.getDataLayout().getTypeAllocSize(Ty));
56	}
57
58	CharUnits getSize(const llvm::Constant *C) const {
59	return getSize(Ty: C->getType());
60	}
61
62	llvm::Constant *getPadding(CharUnits PadSize) const {
63	llvm::Type *Ty = CGM.CharTy;
64	if (PadSize > CharUnits::One())
65	Ty = llvm::ArrayType::get(ElementType: Ty, NumElements: PadSize.getQuantity());
66	return llvm::UndefValue::get(T: Ty);
67	}
68
69	llvm::Constant *getZeroes(CharUnits ZeroSize) const {
70	llvm::Type *Ty = llvm::ArrayType::get(ElementType: CGM.CharTy, NumElements: ZeroSize.getQuantity());
71	return llvm::ConstantAggregateZero::get(Ty);
72	}
73	};
74
75	/// Incremental builder for an llvm::Constant* holding a struct or array
76	/// constant.
77	class ConstantAggregateBuilder : private ConstantAggregateBuilderUtils {
78	/// The elements of the constant. These two arrays must have the same size;
79	/// Offsets[i] describes the offset of Elems[i] within the constant. The
80	/// elements are kept in increasing offset order, and we ensure that there
81	/// is no overlap: Offsets[i+1] >= Offsets[i] + getSize(Elemes[i]).
82	///
83	/// This may contain explicit padding elements (in order to create a
84	/// natural layout), but need not. Gaps between elements are implicitly
85	/// considered to be filled with undef.
86	llvm::SmallVector<llvm::Constant*, 32> Elems;
87	llvm::SmallVector<CharUnits, 32> Offsets;
88
89	/// The size of the constant (the maximum end offset of any added element).
90	/// May be larger than the end of Elems.back() if we split the last element
91	/// and removed some trailing undefs.
92	CharUnits Size = CharUnits::Zero();
93
94	/// This is true only if laying out Elems in order as the elements of a
95	/// non-packed LLVM struct will give the correct layout.
96	bool NaturalLayout = true;
97
98	bool split(size_t Index, CharUnits Hint);
99	std::optional<size_t> splitAt(CharUnits Pos);
100
101	static llvm::Constant *buildFrom(CodeGenModule &CGM,
102	ArrayRef<llvm::Constant *> Elems,
103	ArrayRef<CharUnits> Offsets,
104	CharUnits StartOffset, CharUnits Size,
105	bool NaturalLayout, llvm::Type *DesiredTy,
106	bool AllowOversized);
107
108	public:
109	ConstantAggregateBuilder(CodeGenModule &CGM)
110	: ConstantAggregateBuilderUtils(CGM) {}
111
112	/// Update or overwrite the value starting at \p Offset with \c C.
113	///
114	/// \param AllowOverwrite If \c true, this constant might overwrite (part of)
115	/// a constant that has already been added. This flag is only used to
116	/// detect bugs.
117	bool add(llvm::Constant *C, CharUnits Offset, bool AllowOverwrite);
118
119	/// Update or overwrite the bits starting at \p OffsetInBits with \p Bits.
120	bool addBits(llvm::APInt Bits, uint64_t OffsetInBits, bool AllowOverwrite);
121
122	/// Attempt to condense the value starting at \p Offset to a constant of type
123	/// \p DesiredTy.
124	void condense(CharUnits Offset, llvm::Type *DesiredTy);
125
126	/// Produce a constant representing the entire accumulated value, ideally of
127	/// the specified type. If \p AllowOversized, the constant might be larger
128	/// than implied by \p DesiredTy (eg, if there is a flexible array member).
129	/// Otherwise, the constant will be of exactly the same size as \p DesiredTy
130	/// even if we can't represent it as that type.
131	llvm::Constant *build(llvm::Type *DesiredTy, bool AllowOversized) const {
132	return buildFrom(CGM, Elems, Offsets, StartOffset: CharUnits::Zero(), Size,
133	NaturalLayout, DesiredTy, AllowOversized);
134	}
135	};
136
137	template<typename Container, typename Range = std::initializer_list<
138	typename Container::value_type>>
139	static void replace(Container &C, size_t BeginOff, size_t EndOff, Range Vals) {
140	assert(BeginOff <= EndOff && "invalid replacement range");
141	llvm::replace(C, C.begin() + BeginOff, C.begin() + EndOff, Vals);
142	}
143
144	bool ConstantAggregateBuilder::add(llvm::Constant *C, CharUnits Offset,
145	bool AllowOverwrite) {
146	// Common case: appending to a layout.
147	if (Offset >= Size) {
148	CharUnits Align = getAlignment(C);
149	CharUnits AlignedSize = Size.alignTo(Align);
150	if (AlignedSize > Offset || Offset.alignTo(Align) != Offset)
151	NaturalLayout = false;
152	else if (AlignedSize < Offset) {
153	Elems.push_back(Elt: getPadding(PadSize: Offset - Size));
154	Offsets.push_back(Elt: Size);
155	}
156	Elems.push_back(Elt: C);
157	Offsets.push_back(Elt: Offset);
158	Size = Offset + getSize(C);
159	return true;
160	}
161
162	// Uncommon case: constant overlaps what we've already created.
163	std::optional<size_t> FirstElemToReplace = splitAt(Pos: Offset);
164	if (!FirstElemToReplace)
165	return false;
166
167	CharUnits CSize = getSize(C);
168	std::optional<size_t> LastElemToReplace = splitAt(Pos: Offset + CSize);
169	if (!LastElemToReplace)
170	return false;
171
172	assert((FirstElemToReplace == LastElemToReplace || AllowOverwrite) &&
173	"unexpectedly overwriting field");
174
175	replace(C&: Elems, BeginOff: *FirstElemToReplace, EndOff: *LastElemToReplace, Vals: {C});
176	replace(C&: Offsets, BeginOff: *FirstElemToReplace, EndOff: *LastElemToReplace, Vals: {Offset});
177	Size = std::max(a: Size, b: Offset + CSize);
178	NaturalLayout = false;
179	return true;
180	}
181
182	bool ConstantAggregateBuilder::addBits(llvm::APInt Bits, uint64_t OffsetInBits,
183	bool AllowOverwrite) {
184	const ASTContext &Context = CGM.getContext();
185	const uint64_t CharWidth = CGM.getContext().getCharWidth();
186
187	// Offset of where we want the first bit to go within the bits of the
188	// current char.
189	unsigned OffsetWithinChar = OffsetInBits % CharWidth;
190
191	// We split bit-fields up into individual bytes. Walk over the bytes and
192	// update them.
193	for (CharUnits OffsetInChars =
194	Context.toCharUnitsFromBits(BitSize: OffsetInBits - OffsetWithinChar);
195	/**/; ++OffsetInChars) {
196	// Number of bits we want to fill in this char.
197	unsigned WantedBits =
198	std::min(a: (uint64_t)Bits.getBitWidth(), b: CharWidth - OffsetWithinChar);
199
200	// Get a char containing the bits we want in the right places. The other
201	// bits have unspecified values.
202	llvm::APInt BitsThisChar = Bits;
203	if (BitsThisChar.getBitWidth() < CharWidth)
204	BitsThisChar = BitsThisChar.zext(width: CharWidth);
205	if (CGM.getDataLayout().isBigEndian()) {
206	// Figure out how much to shift by. We may need to left-shift if we have
207	// less than one byte of Bits left.
208	int Shift = Bits.getBitWidth() - CharWidth + OffsetWithinChar;
209	if (Shift > 0)
210	BitsThisChar.lshrInPlace(ShiftAmt: Shift);
211	else if (Shift < 0)
212	BitsThisChar = BitsThisChar.shl(shiftAmt: -Shift);
213	} else {
214	BitsThisChar = BitsThisChar.shl(shiftAmt: OffsetWithinChar);
215	}
216	if (BitsThisChar.getBitWidth() > CharWidth)
217	BitsThisChar = BitsThisChar.trunc(width: CharWidth);
218
219	if (WantedBits == CharWidth) {
220	// Got a full byte: just add it directly.
221	add(C: llvm::ConstantInt::get(Context&: CGM.getLLVMContext(), V: BitsThisChar),
222	Offset: OffsetInChars, AllowOverwrite);
223	} else {
224	// Partial byte: update the existing integer if there is one. If we
225	// can't split out a 1-CharUnit range to update, then we can't add
226	// these bits and fail the entire constant emission.
227	std::optional<size_t> FirstElemToUpdate = splitAt(Pos: OffsetInChars);
228	if (!FirstElemToUpdate)
229	return false;
230	std::optional<size_t> LastElemToUpdate =
231	splitAt(Pos: OffsetInChars + CharUnits::One());
232	if (!LastElemToUpdate)
233	return false;
234	assert(*LastElemToUpdate - *FirstElemToUpdate < 2 &&
235	"should have at most one element covering one byte");
236
237	// Figure out which bits we want and discard the rest.
238	llvm::APInt UpdateMask(CharWidth, 0);
239	if (CGM.getDataLayout().isBigEndian())
240	UpdateMask.setBits(loBit: CharWidth - OffsetWithinChar - WantedBits,
241	hiBit: CharWidth - OffsetWithinChar);
242	else
243	UpdateMask.setBits(loBit: OffsetWithinChar, hiBit: OffsetWithinChar + WantedBits);
244	BitsThisChar &= UpdateMask;
245
246	if (*FirstElemToUpdate == *LastElemToUpdate ||
247	Elems[*FirstElemToUpdate]->isNullValue() ||
248	isa<llvm::UndefValue>(Val: Elems[*FirstElemToUpdate])) {
249	// All existing bits are either zero or undef.
250	add(C: llvm::ConstantInt::get(Context&: CGM.getLLVMContext(), V: BitsThisChar),
251	Offset: OffsetInChars, /*AllowOverwrite*/ true);
252	} else {
253	llvm::Constant *&ToUpdate = Elems[*FirstElemToUpdate];
254	// In order to perform a partial update, we need the existing bitwise
255	// value, which we can only extract for a constant int.
256	auto *CI = dyn_cast<llvm::ConstantInt>(Val: ToUpdate);
257	if (!CI)
258	return false;
259	// Because this is a 1-CharUnit range, the constant occupying it must
260	// be exactly one CharUnit wide.
261	assert(CI->getBitWidth() == CharWidth && "splitAt failed");
262	assert((!(CI->getValue() & UpdateMask) || AllowOverwrite) &&
263	"unexpectedly overwriting bitfield");
264	BitsThisChar |= (CI->getValue() & ~UpdateMask);
265	ToUpdate = llvm::ConstantInt::get(Context&: CGM.getLLVMContext(), V: BitsThisChar);
266	}
267	}
268
269	// Stop if we've added all the bits.
270	if (WantedBits == Bits.getBitWidth())
271	break;
272
273	// Remove the consumed bits from Bits.
274	if (!CGM.getDataLayout().isBigEndian())
275	Bits.lshrInPlace(ShiftAmt: WantedBits);
276	Bits = Bits.trunc(width: Bits.getBitWidth() - WantedBits);
277
278	// The remanining bits go at the start of the following bytes.
279	OffsetWithinChar = 0;
280	}
281
282	return true;
283	}
284
285	/// Returns a position within Elems and Offsets such that all elements
286	/// before the returned index end before Pos and all elements at or after
287	/// the returned index begin at or after Pos. Splits elements as necessary
288	/// to ensure this. Returns std::nullopt if we find something we can't split.
289	std::optional<size_t> ConstantAggregateBuilder::splitAt(CharUnits Pos) {
290	if (Pos >= Size)
291	return Offsets.size();
292
293	while (true) {
294	auto FirstAfterPos = llvm::upper_bound(Range&: Offsets, Value&: Pos);
295	if (FirstAfterPos == Offsets.begin())
296	return 0;
297
298	// If we already have an element starting at Pos, we're done.
299	size_t LastAtOrBeforePosIndex = FirstAfterPos - Offsets.begin() - 1;
300	if (Offsets[LastAtOrBeforePosIndex] == Pos)
301	return LastAtOrBeforePosIndex;
302
303	// We found an element starting before Pos. Check for overlap.
304	if (Offsets[LastAtOrBeforePosIndex] +
305	getSize(C: Elems[LastAtOrBeforePosIndex]) <= Pos)
306	return LastAtOrBeforePosIndex + 1;
307
308	// Try to decompose it into smaller constants.
309	if (!split(Index: LastAtOrBeforePosIndex, Hint: Pos))
310	return std::nullopt;
311	}
312	}
313
314	/// Split the constant at index Index, if possible. Return true if we did.
315	/// Hint indicates the location at which we'd like to split, but may be
316	/// ignored.
317	bool ConstantAggregateBuilder::split(size_t Index, CharUnits Hint) {
318	NaturalLayout = false;
319	llvm::Constant *C = Elems[Index];
320	CharUnits Offset = Offsets[Index];
321
322	if (auto *CA = dyn_cast<llvm::ConstantAggregate>(Val: C)) {
323	// Expand the sequence into its contained elements.
324	// FIXME: This assumes vector elements are byte-sized.
325	replace(C&: Elems, BeginOff: Index, EndOff: Index + 1,
326	Vals: llvm::map_range(C: llvm::seq(Begin: 0u, End: CA->getNumOperands()),
327	F: [&](unsigned Op) { return CA->getOperand(i_nocapture: Op); }));
328	if (isa<llvm::ArrayType>(Val: CA->getType()) ||
329	isa<llvm::VectorType>(Val: CA->getType())) {
330	// Array or vector.
331	llvm::Type *ElemTy =
332	llvm::GetElementPtrInst::getTypeAtIndex(Ty: CA->getType(), Idx: (uint64_t)0);
333	CharUnits ElemSize = getSize(Ty: ElemTy);
334	replace(
335	C&: Offsets, BeginOff: Index, EndOff: Index + 1,
336	Vals: llvm::map_range(C: llvm::seq(Begin: 0u, End: CA->getNumOperands()),
337	F: [&](unsigned Op) { return Offset + Op * ElemSize; }));
338	} else {
339	// Must be a struct.
340	auto *ST = cast<llvm::StructType>(Val: CA->getType());
341	const llvm::StructLayout *Layout =
342	CGM.getDataLayout().getStructLayout(Ty: ST);
343	replace(C&: Offsets, BeginOff: Index, EndOff: Index + 1,
344	Vals: llvm::map_range(
345	C: llvm::seq(Begin: 0u, End: CA->getNumOperands()), F: [&](unsigned Op) {
346	return Offset + CharUnits::fromQuantity(
347	Quantity: Layout->getElementOffset(Idx: Op));
348	}));
349	}
350	return true;
351	}
352
353	if (auto *CDS = dyn_cast<llvm::ConstantDataSequential>(Val: C)) {
354	// Expand the sequence into its contained elements.
355	// FIXME: This assumes vector elements are byte-sized.
356	// FIXME: If possible, split into two ConstantDataSequentials at Hint.
357	CharUnits ElemSize = getSize(Ty: CDS->getElementType());
358	replace(C&: Elems, BeginOff: Index, EndOff: Index + 1,
359	Vals: llvm::map_range(C: llvm::seq(Begin: 0u, End: CDS->getNumElements()),
360	F: [&](unsigned Elem) {
361	return CDS->getElementAsConstant(i: Elem);
362	}));
363	replace(C&: Offsets, BeginOff: Index, EndOff: Index + 1,
364	Vals: llvm::map_range(
365	C: llvm::seq(Begin: 0u, End: CDS->getNumElements()),
366	F: [&](unsigned Elem) { return Offset + Elem * ElemSize; }));
367	return true;
368	}
369
370	if (isa<llvm::ConstantAggregateZero>(Val: C)) {
371	// Split into two zeros at the hinted offset.
372	CharUnits ElemSize = getSize(C);
373	assert(Hint > Offset && Hint < Offset + ElemSize && "nothing to split");
374	replace(C&: Elems, BeginOff: Index, EndOff: Index + 1,
375	Vals: {getZeroes(ZeroSize: Hint - Offset), getZeroes(ZeroSize: Offset + ElemSize - Hint)});
376	replace(C&: Offsets, BeginOff: Index, EndOff: Index + 1, Vals: {Offset, Hint});
377	return true;
378	}
379
380	if (isa<llvm::UndefValue>(Val: C)) {
381	// Drop undef; it doesn't contribute to the final layout.
382	replace(C&: Elems, BeginOff: Index, EndOff: Index + 1, Vals: {});
383	replace(C&: Offsets, BeginOff: Index, EndOff: Index + 1, Vals: {});
384	return true;
385	}
386
387	// FIXME: We could split a ConstantInt if the need ever arose.
388	// We don't need to do this to handle bit-fields because we always eagerly
389	// split them into 1-byte chunks.
390
391	return false;
392	}
393
394	static llvm::Constant *
395	EmitArrayConstant(CodeGenModule &CGM, llvm::ArrayType *DesiredType,
396	llvm::Type *CommonElementType, unsigned ArrayBound,
397	SmallVectorImpl<llvm::Constant *> &Elements,
398	llvm::Constant *Filler);
399
400	llvm::Constant *ConstantAggregateBuilder::buildFrom(
401	CodeGenModule &CGM, ArrayRef<llvm::Constant *> Elems,
402	ArrayRef<CharUnits> Offsets, CharUnits StartOffset, CharUnits Size,
403	bool NaturalLayout, llvm::Type *DesiredTy, bool AllowOversized) {
404	ConstantAggregateBuilderUtils Utils(CGM);
405
406	if (Elems.empty())
407	return llvm::UndefValue::get(T: DesiredTy);
408
409	auto Offset = [&](size_t I) { return Offsets[I] - StartOffset; };
410
411	// If we want an array type, see if all the elements are the same type and
412	// appropriately spaced.
413	if (llvm::ArrayType *ATy = dyn_cast<llvm::ArrayType>(Val: DesiredTy)) {
414	assert(!AllowOversized && "oversized array emission not supported");
415
416	bool CanEmitArray = true;
417	llvm::Type *CommonType = Elems[0]->getType();
418	llvm::Constant *Filler = llvm::Constant::getNullValue(Ty: CommonType);
419	CharUnits ElemSize = Utils.getSize(Ty: ATy->getElementType());
420	SmallVector<llvm::Constant*, 32> ArrayElements;
421	for (size_t I = 0; I != Elems.size(); ++I) {
422	// Skip zeroes; we'll use a zero value as our array filler.
423	if (Elems[I]->isNullValue())
424	continue;
425
426	// All remaining elements must be the same type.
427	if (Elems[I]->getType() != CommonType ||
428	Offset(I) % ElemSize != 0) {
429	CanEmitArray = false;
430	break;
431	}
432	ArrayElements.resize(N: Offset(I) / ElemSize + 1, NV: Filler);
433	ArrayElements.back() = Elems[I];
434	}
435
436	if (CanEmitArray) {
437	return EmitArrayConstant(CGM, DesiredType: ATy, CommonElementType: CommonType, ArrayBound: ATy->getNumElements(),
438	Elements&: ArrayElements, Filler);
439	}
440
441	// Can't emit as an array, carry on to emit as a struct.
442	}
443
444	// The size of the constant we plan to generate. This is usually just
445	// the size of the initialized type, but in AllowOversized mode (i.e.
446	// flexible array init), it can be larger.
447	CharUnits DesiredSize = Utils.getSize(Ty: DesiredTy);
448	if (Size > DesiredSize) {
449	assert(AllowOversized && "Elems are oversized");
450	DesiredSize = Size;
451	}
452
453	// The natural alignment of an unpacked LLVM struct with the given elements.
454	CharUnits Align = CharUnits::One();
455	for (llvm::Constant *C : Elems)
456	Align = std::max(a: Align, b: Utils.getAlignment(C));
457
458	// The natural size of an unpacked LLVM struct with the given elements.
459	CharUnits AlignedSize = Size.alignTo(Align);
460
461	bool Packed = false;
462	ArrayRef<llvm::Constant*> UnpackedElems = Elems;
463	llvm::SmallVector<llvm::Constant*, 32> UnpackedElemStorage;
464	if (DesiredSize < AlignedSize || DesiredSize.alignTo(Align) != DesiredSize) {
465	// The natural layout would be too big; force use of a packed layout.
466	NaturalLayout = false;
467	Packed = true;
468	} else if (DesiredSize > AlignedSize) {
469	// The natural layout would be too small. Add padding to fix it. (This
470	// is ignored if we choose a packed layout.)
471	UnpackedElemStorage.assign(in_start: Elems.begin(), in_end: Elems.end());
472	UnpackedElemStorage.push_back(Elt: Utils.getPadding(PadSize: DesiredSize - Size));
473	UnpackedElems = UnpackedElemStorage;
474	}
475
476	// If we don't have a natural layout, insert padding as necessary.
477	// As we go, double-check to see if we can actually just emit Elems
478	// as a non-packed struct and do so opportunistically if possible.
479	llvm::SmallVector<llvm::Constant*, 32> PackedElems;
480	if (!NaturalLayout) {
481	CharUnits SizeSoFar = CharUnits::Zero();
482	for (size_t I = 0; I != Elems.size(); ++I) {
483	CharUnits Align = Utils.getAlignment(C: Elems[I]);
484	CharUnits NaturalOffset = SizeSoFar.alignTo(Align);
485	CharUnits DesiredOffset = Offset(I);
486	assert(DesiredOffset >= SizeSoFar && "elements out of order");
487
488	if (DesiredOffset != NaturalOffset)
489	Packed = true;
490	if (DesiredOffset != SizeSoFar)
491	PackedElems.push_back(Elt: Utils.getPadding(PadSize: DesiredOffset - SizeSoFar));
492	PackedElems.push_back(Elt: Elems[I]);
493	SizeSoFar = DesiredOffset + Utils.getSize(C: Elems[I]);
494	}
495	// If we're using the packed layout, pad it out to the desired size if
496	// necessary.
497	if (Packed) {
498	assert(SizeSoFar <= DesiredSize &&
499	"requested size is too small for contents");
500	if (SizeSoFar < DesiredSize)
501	PackedElems.push_back(Elt: Utils.getPadding(PadSize: DesiredSize - SizeSoFar));
502	}
503	}
504
505	llvm::StructType *STy = llvm::ConstantStruct::getTypeForElements(
506	Ctx&: CGM.getLLVMContext(), V: Packed ? PackedElems : UnpackedElems, Packed);
507
508	// Pick the type to use. If the type is layout identical to the desired
509	// type then use it, otherwise use whatever the builder produced for us.
510	if (llvm::StructType *DesiredSTy = dyn_cast<llvm::StructType>(Val: DesiredTy)) {
511	if (DesiredSTy->isLayoutIdentical(Other: STy))
512	STy = DesiredSTy;
513	}
514
515	return llvm::ConstantStruct::get(T: STy, V: Packed ? PackedElems : UnpackedElems);
516	}
517
518	void ConstantAggregateBuilder::condense(CharUnits Offset,
519	llvm::Type *DesiredTy) {
520	CharUnits Size = getSize(Ty: DesiredTy);
521
522	std::optional<size_t> FirstElemToReplace = splitAt(Pos: Offset);
523	if (!FirstElemToReplace)
524	return;
525	size_t First = *FirstElemToReplace;
526
527	std::optional<size_t> LastElemToReplace = splitAt(Pos: Offset + Size);
528	if (!LastElemToReplace)
529	return;
530	size_t Last = *LastElemToReplace;
531
532	size_t Length = Last - First;
533	if (Length == 0)
534	return;
535
536	if (Length == 1 && Offsets[First] == Offset &&
537	getSize(C: Elems[First]) == Size) {
538	// Re-wrap single element structs if necessary. Otherwise, leave any single
539	// element constant of the right size alone even if it has the wrong type.
540	auto *STy = dyn_cast<llvm::StructType>(Val: DesiredTy);
541	if (STy && STy->getNumElements() == 1 &&
542	STy->getElementType(N: 0) == Elems[First]->getType())
543	Elems[First] = llvm::ConstantStruct::get(T: STy, Vs: Elems[First]);
544	return;
545	}
546
547	llvm::Constant *Replacement = buildFrom(
548	CGM, Elems: ArrayRef(Elems).slice(N: First, M: Length),
549	Offsets: ArrayRef(Offsets).slice(N: First, M: Length), StartOffset: Offset, Size: getSize(Ty: DesiredTy),
550	/*known to have natural layout=*/NaturalLayout: false, DesiredTy, AllowOversized: false);
551	replace(C&: Elems, BeginOff: First, EndOff: Last, Vals: {Replacement});
552	replace(C&: Offsets, BeginOff: First, EndOff: Last, Vals: {Offset});
553	}
554
555	//===----------------------------------------------------------------------===//
556	// ConstStructBuilder
557	//===----------------------------------------------------------------------===//
558
559	class ConstStructBuilder {
560	CodeGenModule &CGM;
561	ConstantEmitter &Emitter;
562	ConstantAggregateBuilder &Builder;
563	CharUnits StartOffset;
564
565	public:
566	static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
567	InitListExpr *ILE, QualType StructTy);
568	static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
569	const APValue &Value, QualType ValTy);
570	static bool UpdateStruct(ConstantEmitter &Emitter,
571	ConstantAggregateBuilder &Const, CharUnits Offset,
572	InitListExpr *Updater);
573
574	private:
575	ConstStructBuilder(ConstantEmitter &Emitter,
576	ConstantAggregateBuilder &Builder, CharUnits StartOffset)
577	: CGM(Emitter.CGM), Emitter(Emitter), Builder(Builder),
578	StartOffset(StartOffset) {}
579
580	bool AppendField(const FieldDecl *Field, uint64_t FieldOffset,
581	llvm::Constant *InitExpr, bool AllowOverwrite = false);
582
583	bool AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst,
584	bool AllowOverwrite = false);
585
586	bool AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
587	llvm::ConstantInt *InitExpr, bool AllowOverwrite = false);
588
589	bool Build(InitListExpr *ILE, bool AllowOverwrite);
590	bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
591	const CXXRecordDecl *VTableClass, CharUnits BaseOffset);
592	llvm::Constant *Finalize(QualType Ty);
593	};
594
595	bool ConstStructBuilder::AppendField(
596	const FieldDecl *Field, uint64_t FieldOffset, llvm::Constant *InitCst,
597	bool AllowOverwrite) {
598	const ASTContext &Context = CGM.getContext();
599
600	CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(BitSize: FieldOffset);
601
602	return AppendBytes(FieldOffsetInChars, InitCst, AllowOverwrite);
603	}
604
605	bool ConstStructBuilder::AppendBytes(CharUnits FieldOffsetInChars,
606	llvm::Constant *InitCst,
607	bool AllowOverwrite) {
608	return Builder.add(C: InitCst, Offset: StartOffset + FieldOffsetInChars, AllowOverwrite);
609	}
610
611	bool ConstStructBuilder::AppendBitField(
612	const FieldDecl *Field, uint64_t FieldOffset, llvm::ConstantInt *CI,
613	bool AllowOverwrite) {
614	const CGRecordLayout &RL =
615	CGM.getTypes().getCGRecordLayout(Field->getParent());
616	const CGBitFieldInfo &Info = RL.getBitFieldInfo(FD: Field);
617	llvm::APInt FieldValue = CI->getValue();
618
619	// Promote the size of FieldValue if necessary
620	// FIXME: This should never occur, but currently it can because initializer
621	// constants are cast to bool, and because clang is not enforcing bitfield
622	// width limits.
623	if (Info.Size > FieldValue.getBitWidth())
624	FieldValue = FieldValue.zext(width: Info.Size);
625
626	// Truncate the size of FieldValue to the bit field size.
627	if (Info.Size < FieldValue.getBitWidth())
628	FieldValue = FieldValue.trunc(width: Info.Size);
629
630	return Builder.addBits(Bits: FieldValue,
631	OffsetInBits: CGM.getContext().toBits(CharSize: StartOffset) + FieldOffset,
632	AllowOverwrite);
633	}
634
635	static bool EmitDesignatedInitUpdater(ConstantEmitter &Emitter,
636	ConstantAggregateBuilder &Const,
637	CharUnits Offset, QualType Type,
638	InitListExpr *Updater) {
639	if (Type->isRecordType())
640	return ConstStructBuilder::UpdateStruct(Emitter, Const, Offset, Updater);
641
642	auto CAT = Emitter.CGM.getContext().getAsConstantArrayType(T: Type);
643	if (!CAT)
644	return false;
645	QualType ElemType = CAT->getElementType();
646	CharUnits ElemSize = Emitter.CGM.getContext().getTypeSizeInChars(T: ElemType);
647	llvm::Type *ElemTy = Emitter.CGM.getTypes().ConvertTypeForMem(T: ElemType);
648
649	llvm::Constant *FillC = nullptr;
650	if (Expr *Filler = Updater->getArrayFiller()) {
651	if (!isa<NoInitExpr>(Val: Filler)) {
652	FillC = Emitter.tryEmitAbstractForMemory(E: Filler, T: ElemType);
653	if (!FillC)
654	return false;
655	}
656	}
657
658	unsigned NumElementsToUpdate =
659	FillC ? CAT->getSize().getZExtValue() : Updater->getNumInits();
660	for (unsigned I = 0; I != NumElementsToUpdate; ++I, Offset += ElemSize) {
661	Expr *Init = nullptr;
662	if (I < Updater->getNumInits())
663	Init = Updater->getInit(Init: I);
664
665	if (!Init && FillC) {
666	if (!Const.add(C: FillC, Offset, AllowOverwrite: true))
667	return false;
668	} else if (!Init || isa<NoInitExpr>(Val: Init)) {
669	continue;
670	} else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Val: Init)) {
671	if (!EmitDesignatedInitUpdater(Emitter, Const, Offset, Type: ElemType,
672	Updater: ChildILE))
673	return false;
674	// Attempt to reduce the array element to a single constant if necessary.
675	Const.condense(Offset, DesiredTy: ElemTy);
676	} else {
677	llvm::Constant *Val = Emitter.tryEmitPrivateForMemory(E: Init, T: ElemType);
678	if (!Const.add(C: Val, Offset, AllowOverwrite: true))
679	return false;
680	}
681	}
682
683	return true;
684	}
685
686	bool ConstStructBuilder::Build(InitListExpr *ILE, bool AllowOverwrite) {
687	RecordDecl *RD = ILE->getType()->castAs<RecordType>()->getDecl();
688	const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(D: RD);
689
690	unsigned FieldNo = -1;
691	unsigned ElementNo = 0;
692
693	// Bail out if we have base classes. We could support these, but they only
694	// arise in C++1z where we will have already constant folded most interesting
695	// cases. FIXME: There are still a few more cases we can handle this way.
696	if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
697	if (CXXRD->getNumBases())
698	return false;
699
700	for (FieldDecl *Field : RD->fields()) {
701	++FieldNo;
702
703	// If this is a union, skip all the fields that aren't being initialized.
704	if (RD->isUnion() &&
705	!declaresSameEntity(ILE->getInitializedFieldInUnion(), Field))
706	continue;
707
708	// Don't emit anonymous bitfields.
709	if (Field->isUnnamedBitfield())
710	continue;
711
712	// Get the initializer. A struct can include fields without initializers,
713	// we just use explicit null values for them.
714	Expr *Init = nullptr;
715	if (ElementNo < ILE->getNumInits())
716	Init = ILE->getInit(ElementNo++);
717	if (Init && isa<NoInitExpr>(Init))
718	continue;
719
720	// Zero-sized fields are not emitted, but their initializers may still
721	// prevent emission of this struct as a constant.
722	if (Field->isZeroSize(CGM.getContext())) {
723	if (Init->HasSideEffects(CGM.getContext()))
724	return false;
725	continue;
726	}
727
728	// When emitting a DesignatedInitUpdateExpr, a nested InitListExpr
729	// represents additional overwriting of our current constant value, and not
730	// a new constant to emit independently.
731	if (AllowOverwrite &&
732	(Field->getType()->isArrayType() || Field->getType()->isRecordType())) {
733	if (auto *SubILE = dyn_cast<InitListExpr>(Init)) {
734	CharUnits Offset = CGM.getContext().toCharUnitsFromBits(
735	Layout.getFieldOffset(FieldNo));
736	if (!EmitDesignatedInitUpdater(Emitter, Builder, StartOffset + Offset,
737	Field->getType(), SubILE))
738	return false;
739	// If we split apart the field's value, try to collapse it down to a
740	// single value now.
741	Builder.condense(StartOffset + Offset,
742	CGM.getTypes().ConvertTypeForMem(Field->getType()));
743	continue;
744	}
745	}
746
747	llvm::Constant *EltInit =
748	Init ? Emitter.tryEmitPrivateForMemory(Init, Field->getType())
749	: Emitter.emitNullForMemory(Field->getType());
750	if (!EltInit)
751	return false;
752
753	if (!Field->isBitField()) {
754	// Handle non-bitfield members.
755	if (!AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit,
756	AllowOverwrite))
757	return false;
758	// After emitting a non-empty field with [[no_unique_address]], we may
759	// need to overwrite its tail padding.
760	if (Field->hasAttr<NoUniqueAddressAttr>())
761	AllowOverwrite = true;
762	} else {
763	// Otherwise we have a bitfield.
764	if (auto *CI = dyn_cast<llvm::ConstantInt>(EltInit)) {
765	if (!AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI,
766	AllowOverwrite))
767	return false;
768	} else {
769	// We are trying to initialize a bitfield with a non-trivial constant,
770	// this must require run-time code.
771	return false;
772	}
773	}
774	}
775
776	return true;
777	}
778
779	namespace {
780	struct BaseInfo {
781	BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index)
782	: Decl(Decl), Offset(Offset), Index(Index) {
783	}
784
785	const CXXRecordDecl *Decl;
786	CharUnits Offset;
787	unsigned Index;
788
789	bool operator<(const BaseInfo &O) const { return Offset < O.Offset; }
790	};
791	}
792
793	bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
794	bool IsPrimaryBase,
795	const CXXRecordDecl *VTableClass,
796	CharUnits Offset) {
797	const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(D: RD);
798
799	if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(Val: RD)) {
800	// Add a vtable pointer, if we need one and it hasn't already been added.
801	if (Layout.hasOwnVFPtr()) {
802	llvm::Constant *VTableAddressPoint =
803	CGM.getCXXABI().getVTableAddressPointForConstExpr(
804	Base: BaseSubobject(CD, Offset), VTableClass);
805	if (!AppendBytes(FieldOffsetInChars: Offset, InitCst: VTableAddressPoint))
806	return false;
807	}
808
809	// Accumulate and sort bases, in order to visit them in address order, which
810	// may not be the same as declaration order.
811	SmallVector<BaseInfo, 8> Bases;
812	Bases.reserve(N: CD->getNumBases());
813	unsigned BaseNo = 0;
814	for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(),
815	BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) {
816	assert(!Base->isVirtual() && "should not have virtual bases here");
817	const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl();
818	CharUnits BaseOffset = Layout.getBaseClassOffset(Base: BD);
819	Bases.push_back(Elt: BaseInfo(BD, BaseOffset, BaseNo));
820	}
821	llvm::stable_sort(Range&: Bases);
822
823	for (unsigned I = 0, N = Bases.size(); I != N; ++I) {
824	BaseInfo &Base = Bases[I];
825
826	bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl;
827	Build(Val.getStructBase(i: Base.Index), Base.Decl, IsPrimaryBase,
828	VTableClass, Offset + Base.Offset);
829	}
830	}
831
832	unsigned FieldNo = 0;
833	uint64_t OffsetBits = CGM.getContext().toBits(CharSize: Offset);
834
835	bool AllowOverwrite = false;
836	for (RecordDecl::field_iterator Field = RD->field_begin(),
837	FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
838	// If this is a union, skip all the fields that aren't being initialized.
839	if (RD->isUnion() && !declaresSameEntity(Val.getUnionField(), *Field))
840	continue;
841
842	// Don't emit anonymous bitfields or zero-sized fields.
843	if (Field->isUnnamedBitfield() || Field->isZeroSize(Ctx: CGM.getContext()))
844	continue;
845
846	// Emit the value of the initializer.
847	const APValue &FieldValue =
848	RD->isUnion() ? Val.getUnionValue() : Val.getStructField(i: FieldNo);
849	llvm::Constant *EltInit =
850	Emitter.tryEmitPrivateForMemory(FieldValue, Field->getType());
851	if (!EltInit)
852	return false;
853
854	if (!Field->isBitField()) {
855	// Handle non-bitfield members.
856	if (!AppendField(Field: *Field, FieldOffset: Layout.getFieldOffset(FieldNo) + OffsetBits,
857	InitCst: EltInit, AllowOverwrite))
858	return false;
859	// After emitting a non-empty field with [[no_unique_address]], we may
860	// need to overwrite its tail padding.
861	if (Field->hasAttr<NoUniqueAddressAttr>())
862	AllowOverwrite = true;
863	} else {
864	// Otherwise we have a bitfield.
865	if (!AppendBitField(Field: *Field, FieldOffset: Layout.getFieldOffset(FieldNo) + OffsetBits,
866	CI: cast<llvm::ConstantInt>(Val: EltInit), AllowOverwrite))
867	return false;
868	}
869	}
870
871	return true;
872	}
873
874	llvm::Constant *ConstStructBuilder::Finalize(QualType Type) {
875	Type = Type.getNonReferenceType();
876	RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
877	llvm::Type *ValTy = CGM.getTypes().ConvertType(T: Type);
878	return Builder.build(DesiredTy: ValTy, AllowOversized: RD->hasFlexibleArrayMember());
879	}
880
881	llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
882	InitListExpr *ILE,
883	QualType ValTy) {
884	ConstantAggregateBuilder Const(Emitter.CGM);
885	ConstStructBuilder Builder(Emitter, Const, CharUnits::Zero());
886
887	if (!Builder.Build(ILE, /*AllowOverwrite*/false))
888	return nullptr;
889
890	return Builder.Finalize(Type: ValTy);
891	}
892
893	llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
894	const APValue &Val,
895	QualType ValTy) {
896	ConstantAggregateBuilder Const(Emitter.CGM);
897	ConstStructBuilder Builder(Emitter, Const, CharUnits::Zero());
898
899	const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl();
900	const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(Val: RD);
901	if (!Builder.Build(Val, RD, IsPrimaryBase: false, VTableClass: CD, Offset: CharUnits::Zero()))
902	return nullptr;
903
904	return Builder.Finalize(Type: ValTy);
905	}
906
907	bool ConstStructBuilder::UpdateStruct(ConstantEmitter &Emitter,
908	ConstantAggregateBuilder &Const,
909	CharUnits Offset, InitListExpr *Updater) {
910	return ConstStructBuilder(Emitter, Const, Offset)
911	.Build(ILE: Updater, /*AllowOverwrite*/ true);
912	}
913
914	//===----------------------------------------------------------------------===//
915	// ConstExprEmitter
916	//===----------------------------------------------------------------------===//
917
918	static ConstantAddress
919	tryEmitGlobalCompoundLiteral(ConstantEmitter &emitter,
920	const CompoundLiteralExpr *E) {
921	CodeGenModule &CGM = emitter.CGM;
922	CharUnits Align = CGM.getContext().getTypeAlignInChars(E->getType());
923	if (llvm::GlobalVariable *Addr =
924	CGM.getAddrOfConstantCompoundLiteralIfEmitted(E))
925	return ConstantAddress(Addr, Addr->getValueType(), Align);
926
927	LangAS addressSpace = E->getType().getAddressSpace();
928	llvm::Constant *C = emitter.tryEmitForInitializer(E->getInitializer(),
929	addressSpace, E->getType());
930	if (!C) {
931	assert(!E->isFileScope() &&
932	"file-scope compound literal did not have constant initializer!");
933	return ConstantAddress::invalid();
934	}
935
936	auto GV = new llvm::GlobalVariable(
937	CGM.getModule(), C->getType(),
938	E->getType().isConstantStorage(CGM.getContext(), true, false),
939	llvm::GlobalValue::InternalLinkage, C, ".compoundliteral", nullptr,
940	llvm::GlobalVariable::NotThreadLocal,
941	CGM.getContext().getTargetAddressSpace(AS: addressSpace));
942	emitter.finalize(global: GV);
943	GV->setAlignment(Align.getAsAlign());
944	CGM.setAddrOfConstantCompoundLiteral(CLE: E, GV: GV);
945	return ConstantAddress(GV, GV->getValueType(), Align);
946	}
947
948	static llvm::Constant *
949	EmitArrayConstant(CodeGenModule &CGM, llvm::ArrayType *DesiredType,
950	llvm::Type *CommonElementType, unsigned ArrayBound,
951	SmallVectorImpl<llvm::Constant *> &Elements,
952	llvm::Constant *Filler) {
953	// Figure out how long the initial prefix of non-zero elements is.
954	unsigned NonzeroLength = ArrayBound;
955	if (Elements.size() < NonzeroLength && Filler->isNullValue())
956	NonzeroLength = Elements.size();
957	if (NonzeroLength == Elements.size()) {
958	while (NonzeroLength > 0 && Elements[NonzeroLength - 1]->isNullValue())
959	--NonzeroLength;
960	}
961
962	if (NonzeroLength == 0)
963	return llvm::ConstantAggregateZero::get(Ty: DesiredType);
964
965	// Add a zeroinitializer array filler if we have lots of trailing zeroes.
966	unsigned TrailingZeroes = ArrayBound - NonzeroLength;
967	if (TrailingZeroes >= 8) {
968	assert(Elements.size() >= NonzeroLength &&
969	"missing initializer for non-zero element");
970
971	// If all the elements had the same type up to the trailing zeroes, emit a
972	// struct of two arrays (the nonzero data and the zeroinitializer).
973	if (CommonElementType && NonzeroLength >= 8) {
974	llvm::Constant *Initial = llvm::ConstantArray::get(
975	T: llvm::ArrayType::get(ElementType: CommonElementType, NumElements: NonzeroLength),
976	V: ArrayRef(Elements).take_front(N: NonzeroLength));
977	Elements.resize(N: 2);
978	Elements[0] = Initial;
979	} else {
980	Elements.resize(N: NonzeroLength + 1);
981	}
982
983	auto *FillerType =
984	CommonElementType ? CommonElementType : DesiredType->getElementType();
985	FillerType = llvm::ArrayType::get(ElementType: FillerType, NumElements: TrailingZeroes);
986	Elements.back() = llvm::ConstantAggregateZero::get(Ty: FillerType);
987	CommonElementType = nullptr;
988	} else if (Elements.size() != ArrayBound) {
989	// Otherwise pad to the right size with the filler if necessary.
990	Elements.resize(N: ArrayBound, NV: Filler);
991	if (Filler->getType() != CommonElementType)
992	CommonElementType = nullptr;
993	}
994
995	// If all elements have the same type, just emit an array constant.
996	if (CommonElementType)
997	return llvm::ConstantArray::get(
998	T: llvm::ArrayType::get(ElementType: CommonElementType, NumElements: ArrayBound), V: Elements);
999
1000	// We have mixed types. Use a packed struct.
1001	llvm::SmallVector<llvm::Type *, 16> Types;
1002	Types.reserve(N: Elements.size());
1003	for (llvm::Constant *Elt : Elements)
1004	Types.push_back(Elt: Elt->getType());
1005	llvm::StructType *SType =
1006	llvm::StructType::get(Context&: CGM.getLLVMContext(), Elements: Types, isPacked: true);
1007	return llvm::ConstantStruct::get(T: SType, V: Elements);
1008	}
1009
1010	// This class only needs to handle arrays, structs and unions. Outside C++11
1011	// mode, we don't currently constant fold those types. All other types are
1012	// handled by constant folding.
1013	//
1014	// Constant folding is currently missing support for a few features supported
1015	// here: CK_ToUnion, CK_ReinterpretMemberPointer, and DesignatedInitUpdateExpr.
1016	class ConstExprEmitter :
1017	public StmtVisitor<ConstExprEmitter, llvm::Constant*, QualType> {
1018	CodeGenModule &CGM;
1019	ConstantEmitter &Emitter;
1020	llvm::LLVMContext &VMContext;
1021	public:
1022	ConstExprEmitter(ConstantEmitter &emitter)
1023	: CGM(emitter.CGM), Emitter(emitter), VMContext(CGM.getLLVMContext()) {
1024	}
1025
1026	//===--------------------------------------------------------------------===//
1027	// Visitor Methods
1028	//===--------------------------------------------------------------------===//
1029
1030	llvm::Constant *VisitStmt(Stmt *S, QualType T) {
1031	return nullptr;
1032	}
1033
1034	llvm::Constant *VisitConstantExpr(ConstantExpr *CE, QualType T) {
1035	if (llvm::Constant *Result = Emitter.tryEmitConstantExpr(CE))
1036	return Result;
1037	return Visit(CE->getSubExpr(), T);
1038	}
1039
1040	llvm::Constant *VisitParenExpr(ParenExpr *PE, QualType T) {
1041	return Visit(PE->getSubExpr(), T);
1042	}
1043
1044	llvm::Constant *
1045	VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE,
1046	QualType T) {
1047	return Visit(PE->getReplacement(), T);
1048	}
1049
1050	llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE,
1051	QualType T) {
1052	return Visit(GE->getResultExpr(), T);
1053	}
1054
1055	llvm::Constant *VisitChooseExpr(ChooseExpr *CE, QualType T) {
1056	return Visit(CE->getChosenSubExpr(), T);
1057	}
1058
1059	llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E, QualType T) {
1060	return Visit(E->getInitializer(), T);
1061	}
1062
1063	llvm::Constant *VisitCastExpr(CastExpr *E, QualType destType) {
1064	if (const auto *ECE = dyn_cast<ExplicitCastExpr>(Val: E))
1065	CGM.EmitExplicitCastExprType(E: ECE, CGF: Emitter.CGF);
1066	Expr *subExpr = E->getSubExpr();
1067
1068	switch (E->getCastKind()) {
1069	case CK_ToUnion: {
1070	// GCC cast to union extension
1071	assert(E->getType()->isUnionType() &&
1072	"Destination type is not union type!");
1073
1074	auto field = E->getTargetUnionField();
1075
1076	auto C = Emitter.tryEmitPrivateForMemory(subExpr, field->getType());
1077	if (!C) return nullptr;
1078
1079	auto destTy = ConvertType(T: destType);
1080	if (C->getType() == destTy) return C;
1081
1082	// Build a struct with the union sub-element as the first member,
1083	// and padded to the appropriate size.
1084	SmallVector<llvm::Constant*, 2> Elts;
1085	SmallVector<llvm::Type*, 2> Types;
1086	Elts.push_back(Elt: C);
1087	Types.push_back(Elt: C->getType());
1088	unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(Ty: C->getType());
1089	unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(Ty: destTy);
1090
1091	assert(CurSize <= TotalSize && "Union size mismatch!");
1092	if (unsigned NumPadBytes = TotalSize - CurSize) {
1093	llvm::Type *Ty = CGM.CharTy;
1094	if (NumPadBytes > 1)
1095	Ty = llvm::ArrayType::get(ElementType: Ty, NumElements: NumPadBytes);
1096
1097	Elts.push_back(Elt: llvm::UndefValue::get(T: Ty));
1098	Types.push_back(Elt: Ty);
1099	}
1100
1101	llvm::StructType *STy = llvm::StructType::get(Context&: VMContext, Elements: Types, isPacked: false);
1102	return llvm::ConstantStruct::get(T: STy, V: Elts);
1103	}
1104
1105	case CK_AddressSpaceConversion: {
1106	auto C = Emitter.tryEmitPrivate(E: subExpr, T: subExpr->getType());
1107	if (!C) return nullptr;
1108	LangAS destAS = E->getType()->getPointeeType().getAddressSpace();
1109	LangAS srcAS = subExpr->getType()->getPointeeType().getAddressSpace();
1110	llvm::Type *destTy = ConvertType(T: E->getType());
1111	return CGM.getTargetCodeGenInfo().performAddrSpaceCast(CGM, V: C, SrcAddr: srcAS,
1112	DestAddr: destAS, DestTy: destTy);
1113	}
1114
1115	case CK_LValueToRValue: {
1116	// We don't really support doing lvalue-to-rvalue conversions here; any
1117	// interesting conversions should be done in Evaluate(). But as a
1118	// special case, allow compound literals to support the gcc extension
1119	// allowing "struct x {int x;} x = (struct x) {};".
1120	if (auto *E = dyn_cast<CompoundLiteralExpr>(Val: subExpr->IgnoreParens()))
1121	return Visit(E->getInitializer(), destType);
1122	return nullptr;
1123	}
1124
1125	case CK_AtomicToNonAtomic:
1126	case CK_NonAtomicToAtomic:
1127	case CK_NoOp:
1128	case CK_ConstructorConversion:
1129	return Visit(subExpr, destType);
1130
1131	case CK_ArrayToPointerDecay:
1132	if (const auto *S = dyn_cast<StringLiteral>(Val: subExpr))
1133	return CGM.GetAddrOfConstantStringFromLiteral(S).getPointer();
1134	return nullptr;
1135	case CK_NullToPointer:
1136	if (Visit(subExpr, destType))
1137	return CGM.EmitNullConstant(T: destType);
1138	return nullptr;
1139
1140	case CK_IntToOCLSampler:
1141	llvm_unreachable("global sampler variables are not generated");
1142
1143	case CK_IntegralCast: {
1144	QualType FromType = subExpr->getType();
1145	// See also HandleIntToIntCast in ExprConstant.cpp
1146	if (FromType->isIntegerType())
1147	if (llvm::Constant *C = Visit(subExpr, FromType))
1148	if (auto *CI = dyn_cast<llvm::ConstantInt>(C)) {
1149	unsigned SrcWidth = CGM.getContext().getIntWidth(T: FromType);
1150	unsigned DstWidth = CGM.getContext().getIntWidth(T: destType);
1151	if (DstWidth == SrcWidth)
1152	return CI;
1153	llvm::APInt A = FromType->isSignedIntegerType()
1154	? CI->getValue().sextOrTrunc(DstWidth)
1155	: CI->getValue().zextOrTrunc(DstWidth);
1156	return llvm::ConstantInt::get(Context&: CGM.getLLVMContext(), V: A);
1157	}
1158	return nullptr;
1159	}
1160
1161	case CK_Dependent: llvm_unreachable("saw dependent cast!");
1162
1163	case CK_BuiltinFnToFnPtr:
1164	llvm_unreachable("builtin functions are handled elsewhere");
1165
1166	case CK_ReinterpretMemberPointer:
1167	case CK_DerivedToBaseMemberPointer:
1168	case CK_BaseToDerivedMemberPointer: {
1169	auto C = Emitter.tryEmitPrivate(E: subExpr, T: subExpr->getType());
1170	if (!C) return nullptr;
1171	return CGM.getCXXABI().EmitMemberPointerConversion(E, Src: C);
1172	}
1173
1174	// These will never be supported.
1175	case CK_ObjCObjectLValueCast:
1176	case CK_ARCProduceObject:
1177	case CK_ARCConsumeObject:
1178	case CK_ARCReclaimReturnedObject:
1179	case CK_ARCExtendBlockObject:
1180	case CK_CopyAndAutoreleaseBlockObject:
1181	return nullptr;
1182
1183	// These don't need to be handled here because Evaluate knows how to
1184	// evaluate them in the cases where they can be folded.
1185	case CK_BitCast:
1186	case CK_ToVoid:
1187	case CK_Dynamic:
1188	case CK_LValueBitCast:
1189	case CK_LValueToRValueBitCast:
1190	case CK_NullToMemberPointer:
1191	case CK_UserDefinedConversion:
1192	case CK_CPointerToObjCPointerCast:
1193	case CK_BlockPointerToObjCPointerCast:
1194	case CK_AnyPointerToBlockPointerCast:
1195	case CK_FunctionToPointerDecay:
1196	case CK_BaseToDerived:
1197	case CK_DerivedToBase:
1198	case CK_UncheckedDerivedToBase:
1199	case CK_MemberPointerToBoolean:
1200	case CK_VectorSplat:
1201	case CK_FloatingRealToComplex:
1202	case CK_FloatingComplexToReal:
1203	case CK_FloatingComplexToBoolean:
1204	case CK_FloatingComplexCast:
1205	case CK_FloatingComplexToIntegralComplex:
1206	case CK_IntegralRealToComplex:
1207	case CK_IntegralComplexToReal:
1208	case CK_IntegralComplexToBoolean:
1209	case CK_IntegralComplexCast:
1210	case CK_IntegralComplexToFloatingComplex:
1211	case CK_PointerToIntegral:
1212	case CK_PointerToBoolean:
1213	case CK_BooleanToSignedIntegral:
1214	case CK_IntegralToPointer:
1215	case CK_IntegralToBoolean:
1216	case CK_IntegralToFloating:
1217	case CK_FloatingToIntegral:
1218	case CK_FloatingToBoolean:
1219	case CK_FloatingCast:
1220	case CK_FloatingToFixedPoint:
1221	case CK_FixedPointToFloating:
1222	case CK_FixedPointCast:
1223	case CK_FixedPointToBoolean:
1224	case CK_FixedPointToIntegral:
1225	case CK_IntegralToFixedPoint:
1226	case CK_ZeroToOCLOpaqueType:
1227	case CK_MatrixCast:
1228	return nullptr;
1229	}
1230	llvm_unreachable("Invalid CastKind");
1231	}
1232
1233	llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE, QualType T) {
1234	// No need for a DefaultInitExprScope: we don't handle 'this' in a
1235	// constant expression.
1236	return Visit(DIE->getExpr(), T);
1237	}
1238
1239	llvm::Constant *VisitExprWithCleanups(ExprWithCleanups *E, QualType T) {
1240	return Visit(E->getSubExpr(), T);
1241	}
1242
1243	llvm::Constant *VisitIntegerLiteral(IntegerLiteral *I, QualType T) {
1244	return llvm::ConstantInt::get(CGM.getLLVMContext(), I->getValue());
1245	}
1246
1247	llvm::Constant *EmitArrayInitialization(InitListExpr *ILE, QualType T) {
1248	auto *CAT = CGM.getContext().getAsConstantArrayType(T: ILE->getType());
1249	assert(CAT && "can't emit array init for non-constant-bound array");
1250	unsigned NumInitElements = ILE->getNumInits();
1251	unsigned NumElements = CAT->getSize().getZExtValue();
1252
1253	// Initialising an array requires us to automatically
1254	// initialise any elements that have not been initialised explicitly
1255	unsigned NumInitableElts = std::min(a: NumInitElements, b: NumElements);
1256
1257	QualType EltType = CAT->getElementType();
1258
1259	// Initialize remaining array elements.
1260	llvm::Constant *fillC = nullptr;
1261	if (Expr *filler = ILE->getArrayFiller()) {
1262	fillC = Emitter.tryEmitAbstractForMemory(E: filler, T: EltType);
1263	if (!fillC)
1264	return nullptr;
1265	}
1266
1267	// Copy initializer elements.
1268	SmallVector<llvm::Constant*, 16> Elts;
1269	if (fillC && fillC->isNullValue())
1270	Elts.reserve(N: NumInitableElts + 1);
1271	else
1272	Elts.reserve(N: NumElements);
1273
1274	llvm::Type *CommonElementType = nullptr;
1275	for (unsigned i = 0; i < NumInitableElts; ++i) {
1276	Expr *Init = ILE->getInit(Init: i);
1277	llvm::Constant *C = Emitter.tryEmitPrivateForMemory(E: Init, T: EltType);
1278	if (!C)
1279	return nullptr;
1280	if (i == 0)
1281	CommonElementType = C->getType();
1282	else if (C->getType() != CommonElementType)
1283	CommonElementType = nullptr;
1284	Elts.push_back(Elt: C);
1285	}
1286
1287	llvm::ArrayType *Desired =
1288	cast<llvm::ArrayType>(CGM.getTypes().ConvertType(T: ILE->getType()));
1289	return EmitArrayConstant(CGM, DesiredType: Desired, CommonElementType, ArrayBound: NumElements, Elements&: Elts,
1290	Filler: fillC);
1291	}
1292
1293	llvm::Constant *EmitRecordInitialization(InitListExpr *ILE, QualType T) {
1294	return ConstStructBuilder::BuildStruct(Emitter, ILE, ValTy: T);
1295	}
1296
1297	llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E,
1298	QualType T) {
1299	return CGM.EmitNullConstant(T);
1300	}
1301
1302	llvm::Constant *VisitInitListExpr(InitListExpr *ILE, QualType T) {
1303	if (ILE->isTransparent())
1304	return Visit(ILE->getInit(Init: 0), T);
1305
1306	if (ILE->getType()->isArrayType())
1307	return EmitArrayInitialization(ILE, T);
1308
1309	if (ILE->getType()->isRecordType())
1310	return EmitRecordInitialization(ILE, T);
1311
1312	return nullptr;
1313	}
1314
1315	llvm::Constant *VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E,
1316	QualType destType) {
1317	auto C = Visit(E->getBase(), destType);
1318	if (!C)
1319	return nullptr;
1320
1321	ConstantAggregateBuilder Const(CGM);
1322	Const.add(C: C, Offset: CharUnits::Zero(), AllowOverwrite: false);
1323
1324	if (!EmitDesignatedInitUpdater(Emitter, Const, Offset: CharUnits::Zero(), Type: destType,
1325	Updater: E->getUpdater()))
1326	return nullptr;
1327
1328	llvm::Type *ValTy = CGM.getTypes().ConvertType(T: destType);
1329	bool HasFlexibleArray = false;
1330	if (auto *RT = destType->getAs<RecordType>())
1331	HasFlexibleArray = RT->getDecl()->hasFlexibleArrayMember();
1332	return Const.build(DesiredTy: ValTy, AllowOversized: HasFlexibleArray);
1333	}
1334
1335	llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E, QualType Ty) {
1336	if (!E->getConstructor()->isTrivial())
1337	return nullptr;
1338
1339	// Only default and copy/move constructors can be trivial.
1340	if (E->getNumArgs()) {
1341	assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
1342	assert(E->getConstructor()->isCopyOrMoveConstructor() &&
1343	"trivial ctor has argument but isn't a copy/move ctor");
1344
1345	Expr *Arg = E->getArg(Arg: 0);
1346	assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
1347	"argument to copy ctor is of wrong type");
1348
1349	// Look through the temporary; it's just converting the value to an
1350	// lvalue to pass it to the constructor.
1351	if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Val: Arg))
1352	return Visit(MTE->getSubExpr(), Ty);
1353	// Don't try to support arbitrary lvalue-to-rvalue conversions for now.
1354	return nullptr;
1355	}
1356
1357	return CGM.EmitNullConstant(T: Ty);
1358	}
1359
1360	llvm::Constant *VisitStringLiteral(StringLiteral *E, QualType T) {
1361	// This is a string literal initializing an array in an initializer.
1362	return CGM.GetConstantArrayFromStringLiteral(E);
1363	}
1364
1365	llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E, QualType T) {
1366	// This must be an @encode initializing an array in a static initializer.
1367	// Don't emit it as the address of the string, emit the string data itself
1368	// as an inline array.
1369	std::string Str;
1370	CGM.getContext().getObjCEncodingForType(T: E->getEncodedType(), S&: Str);
1371	const ConstantArrayType *CAT = CGM.getContext().getAsConstantArrayType(T);
1372	assert(CAT && "String data not of constant array type!");
1373
1374	// Resize the string to the right size, adding zeros at the end, or
1375	// truncating as needed.
1376	Str.resize(n: CAT->getSize().getZExtValue(), c: '\0');
1377	return llvm::ConstantDataArray::getString(Context&: VMContext, Initializer: Str, AddNull: false);
1378	}
1379
1380	llvm::Constant *VisitUnaryExtension(const UnaryOperator *E, QualType T) {
1381	return Visit(E->getSubExpr(), T);
1382	}
1383
1384	llvm::Constant *VisitUnaryMinus(UnaryOperator *U, QualType T) {
1385	if (llvm::Constant *C = Visit(U->getSubExpr(), T))
1386	if (auto *CI = dyn_cast<llvm::ConstantInt>(C))
1387	return llvm::ConstantInt::get(CGM.getLLVMContext(), -CI->getValue());
1388	return nullptr;
1389	}
1390
1391	llvm::Constant *VisitPackIndexingExpr(PackIndexingExpr *E, QualType T) {
1392	return Visit(E->getSelectedExpr(), T);
1393	}
1394
1395	// Utility methods
1396	llvm::Type *ConvertType(QualType T) {
1397	return CGM.getTypes().ConvertType(T);
1398	}
1399	};
1400
1401	} // end anonymous namespace.
1402
1403	llvm::Constant *ConstantEmitter::validateAndPopAbstract(llvm::Constant *C,
1404	AbstractState saved) {
1405	Abstract = saved.OldValue;
1406
1407	assert(saved.OldPlaceholdersSize == PlaceholderAddresses.size() &&
1408	"created a placeholder while doing an abstract emission?");
1409
1410	// No validation necessary for now.
1411	// No cleanup to do for now.
1412	return C;
1413	}
1414
1415	llvm::Constant *
1416	ConstantEmitter::tryEmitAbstractForInitializer(const VarDecl &D) {
1417	auto state = pushAbstract();
1418	auto C = tryEmitPrivateForVarInit(D);
1419	return validateAndPopAbstract(C, saved: state);
1420	}
1421
1422	llvm::Constant *
1423	ConstantEmitter::tryEmitAbstract(const Expr *E, QualType destType) {
1424	auto state = pushAbstract();
1425	auto C = tryEmitPrivate(E, T: destType);
1426	return validateAndPopAbstract(C, saved: state);
1427	}
1428
1429	llvm::Constant *
1430	ConstantEmitter::tryEmitAbstract(const APValue &value, QualType destType) {
1431	auto state = pushAbstract();
1432	auto C = tryEmitPrivate(value, T: destType);
1433	return validateAndPopAbstract(C, saved: state);
1434	}
1435
1436	llvm::Constant *ConstantEmitter::tryEmitConstantExpr(const ConstantExpr *CE) {
1437	if (!CE->hasAPValueResult())
1438	return nullptr;
1439
1440	QualType RetType = CE->getType();
1441	if (CE->isGLValue())
1442	RetType = CGM.getContext().getLValueReferenceType(T: RetType);
1443
1444	return emitAbstract(loc: CE->getBeginLoc(), value: CE->getAPValueResult(), T: RetType);
1445	}
1446
1447	llvm::Constant *
1448	ConstantEmitter::emitAbstract(const Expr *E, QualType destType) {
1449	auto state = pushAbstract();
1450	auto C = tryEmitPrivate(E, T: destType);
1451	C = validateAndPopAbstract(C, saved: state);
1452	if (!C) {
1453	CGM.Error(loc: E->getExprLoc(),
1454	error: "internal error: could not emit constant value \"abstractly\"");
1455	C = CGM.EmitNullConstant(T: destType);
1456	}
1457	return C;
1458	}
1459
1460	llvm::Constant *
1461	ConstantEmitter::emitAbstract(SourceLocation loc, const APValue &value,
1462	QualType destType) {
1463	auto state = pushAbstract();
1464	auto C = tryEmitPrivate(value, T: destType);
1465	C = validateAndPopAbstract(C, saved: state);
1466	if (!C) {
1467	CGM.Error(loc,
1468	error: "internal error: could not emit constant value \"abstractly\"");
1469	C = CGM.EmitNullConstant(T: destType);
1470	}
1471	return C;
1472	}
1473
1474	llvm::Constant *ConstantEmitter::tryEmitForInitializer(const VarDecl &D) {
1475	initializeNonAbstract(destAS: D.getType().getAddressSpace());
1476	return markIfFailed(init: tryEmitPrivateForVarInit(D));
1477	}
1478
1479	llvm::Constant *ConstantEmitter::tryEmitForInitializer(const Expr *E,
1480	LangAS destAddrSpace,
1481	QualType destType) {
1482	initializeNonAbstract(destAS: destAddrSpace);
1483	return markIfFailed(init: tryEmitPrivateForMemory(E, T: destType));
1484	}
1485
1486	llvm::Constant *ConstantEmitter::emitForInitializer(const APValue &value,
1487	LangAS destAddrSpace,
1488	QualType destType) {
1489	initializeNonAbstract(destAS: destAddrSpace);
1490	auto C = tryEmitPrivateForMemory(value, T: destType);
1491	assert(C && "couldn't emit constant value non-abstractly?");
1492	return C;
1493	}
1494
1495	llvm::GlobalValue *ConstantEmitter::getCurrentAddrPrivate() {
1496	assert(!Abstract && "cannot get current address for abstract constant");
1497
1498
1499
1500	// Make an obviously ill-formed global that should blow up compilation
1501	// if it survives.
1502	auto global = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty, true,
1503	llvm::GlobalValue::PrivateLinkage,
1504	/*init*/ nullptr,
1505	/*name*/ "",
1506	/*before*/ nullptr,
1507	llvm::GlobalVariable::NotThreadLocal,
1508	CGM.getContext().getTargetAddressSpace(AS: DestAddressSpace));
1509
1510	PlaceholderAddresses.push_back(Elt: std::make_pair(x: nullptr, y&: global));
1511
1512	return global;
1513	}
1514
1515	void ConstantEmitter::registerCurrentAddrPrivate(llvm::Constant *signal,
1516	llvm::GlobalValue *placeholder) {
1517	assert(!PlaceholderAddresses.empty());
1518	assert(PlaceholderAddresses.back().first == nullptr);
1519	assert(PlaceholderAddresses.back().second == placeholder);
1520	PlaceholderAddresses.back().first = signal;
1521	}
1522
1523	namespace {
1524	struct ReplacePlaceholders {
1525	CodeGenModule &CGM;
1526
1527	/// The base address of the global.
1528	llvm::Constant *Base;
1529	llvm::Type *BaseValueTy = nullptr;
1530
1531	/// The placeholder addresses that were registered during emission.
1532	llvm::DenseMap<llvm::Constant*, llvm::GlobalVariable*> PlaceholderAddresses;
1533
1534	/// The locations of the placeholder signals.
1535	llvm::DenseMap<llvm::GlobalVariable*, llvm::Constant*> Locations;
1536
1537	/// The current index stack. We use a simple unsigned stack because
1538	/// we assume that placeholders will be relatively sparse in the
1539	/// initializer, but we cache the index values we find just in case.
1540	llvm::SmallVector<unsigned, 8> Indices;
1541	llvm::SmallVector<llvm::Constant*, 8> IndexValues;
1542
1543	ReplacePlaceholders(CodeGenModule &CGM, llvm::Constant *base,
1544	ArrayRef<std::pair<llvm::Constant*,
1545	llvm::GlobalVariable*>> addresses)
1546	: CGM(CGM), Base(base),
1547	PlaceholderAddresses(addresses.begin(), addresses.end()) {
1548	}
1549
1550	void replaceInInitializer(llvm::Constant *init) {
1551	// Remember the type of the top-most initializer.
1552	BaseValueTy = init->getType();
1553
1554	// Initialize the stack.
1555	Indices.push_back(Elt: 0);
1556	IndexValues.push_back(Elt: nullptr);
1557
1558	// Recurse into the initializer.
1559	findLocations(init);
1560
1561	// Check invariants.
1562	assert(IndexValues.size() == Indices.size() && "mismatch");
1563	assert(Indices.size() == 1 && "didn't pop all indices");
1564
1565	// Do the replacement; this basically invalidates 'init'.
1566	assert(Locations.size() == PlaceholderAddresses.size() &&
1567	"missed a placeholder?");
1568
1569	// We're iterating over a hashtable, so this would be a source of
1570	// non-determinism in compiler output *except* that we're just
1571	// messing around with llvm::Constant structures, which never itself
1572	// does anything that should be visible in compiler output.
1573	for (auto &entry : Locations) {
1574	assert(entry.first->getParent() == nullptr && "not a placeholder!");
1575	entry.first->replaceAllUsesWith(V: entry.second);
1576	entry.first->eraseFromParent();
1577	}
1578	}
1579
1580	private:
1581	void findLocations(llvm::Constant *init) {
1582	// Recurse into aggregates.
1583	if (auto agg = dyn_cast<llvm::ConstantAggregate>(Val: init)) {
1584	for (unsigned i = 0, e = agg->getNumOperands(); i != e; ++i) {
1585	Indices.push_back(Elt: i);
1586	IndexValues.push_back(Elt: nullptr);
1587
1588	findLocations(init: agg->getOperand(i_nocapture: i));
1589
1590	IndexValues.pop_back();
1591	Indices.pop_back();
1592	}
1593	return;
1594	}
1595
1596	// Otherwise, check for registered constants.
1597	while (true) {
1598	auto it = PlaceholderAddresses.find(Val: init);
1599	if (it != PlaceholderAddresses.end()) {
1600	setLocation(it->second);
1601	break;
1602	}
1603
1604	// Look through bitcasts or other expressions.
1605	if (auto expr = dyn_cast<llvm::ConstantExpr>(Val: init)) {
1606	init = expr->getOperand(i_nocapture: 0);
1607	} else {
1608	break;
1609	}
1610	}
1611	}
1612
1613	void setLocation(llvm::GlobalVariable *placeholder) {
1614	assert(!Locations.contains(placeholder) &&
1615	"already found location for placeholder!");
1616
1617	// Lazily fill in IndexValues with the values from Indices.
1618	// We do this in reverse because we should always have a strict
1619	// prefix of indices from the start.
1620	assert(Indices.size() == IndexValues.size());
1621	for (size_t i = Indices.size() - 1; i != size_t(-1); --i) {
1622	if (IndexValues[i]) {
1623	#ifndef NDEBUG
1624	for (size_t j = 0; j != i + 1; ++j) {
1625	assert(IndexValues[j] &&
1626	isa<llvm::ConstantInt>(IndexValues[j]) &&
1627	cast<llvm::ConstantInt>(IndexValues[j])->getZExtValue()
1628	== Indices[j]);
1629	}
1630	#endif
1631	break;
1632	}
1633
1634	IndexValues[i] = llvm::ConstantInt::get(Ty: CGM.Int32Ty, V: Indices[i]);
1635	}
1636
1637	llvm::Constant *location = llvm::ConstantExpr::getInBoundsGetElementPtr(
1638	Ty: BaseValueTy, C: Base, IdxList: IndexValues);
1639
1640	Locations.insert(KV: {placeholder, location});
1641	}
1642	};
1643	}
1644
1645	void ConstantEmitter::finalize(llvm::GlobalVariable *global) {
1646	assert(InitializedNonAbstract &&
1647	"finalizing emitter that was used for abstract emission?");
1648	assert(!Finalized && "finalizing emitter multiple times");
1649	assert(global->getInitializer());
1650
1651	// Note that we might also be Failed.
1652	Finalized = true;
1653
1654	if (!PlaceholderAddresses.empty()) {
1655	ReplacePlaceholders(CGM, global, PlaceholderAddresses)
1656	.replaceInInitializer(init: global->getInitializer());
1657	PlaceholderAddresses.clear(); // satisfy
1658	}
1659	}
1660
1661	ConstantEmitter::~ConstantEmitter() {
1662	assert((!InitializedNonAbstract || Finalized || Failed) &&
1663	"not finalized after being initialized for non-abstract emission");
1664	assert(PlaceholderAddresses.empty() && "unhandled placeholders");
1665	}
1666
1667	static QualType getNonMemoryType(CodeGenModule &CGM, QualType type) {
1668	if (auto AT = type->getAs<AtomicType>()) {
1669	return CGM.getContext().getQualifiedType(T: AT->getValueType(),
1670	Qs: type.getQualifiers());
1671	}
1672	return type;
1673	}
1674
1675	llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
1676	// Make a quick check if variable can be default NULL initialized
1677	// and avoid going through rest of code which may do, for c++11,
1678	// initialization of memory to all NULLs.
1679	if (!D.hasLocalStorage()) {
1680	QualType Ty = CGM.getContext().getBaseElementType(D.getType());
1681	if (Ty->isRecordType())
1682	if (const CXXConstructExpr *E =
1683	dyn_cast_or_null<CXXConstructExpr>(Val: D.getInit())) {
1684	const CXXConstructorDecl *CD = E->getConstructor();
1685	if (CD->isTrivial() && CD->isDefaultConstructor())
1686	return CGM.EmitNullConstant(T: D.getType());
1687	}
1688	}
1689	InConstantContext = D.hasConstantInitialization();
1690
1691	QualType destType = D.getType();
1692	const Expr *E = D.getInit();
1693	assert(E && "No initializer to emit");
1694
1695	if (!destType->isReferenceType()) {
1696	QualType nonMemoryDestType = getNonMemoryType(CGM, type: destType);
1697	if (llvm::Constant *C = ConstExprEmitter(*this).Visit(const_cast<Expr *>(E),
1698	nonMemoryDestType))
1699	return emitForMemory(C, T: destType);
1700	}
1701
1702	// Try to emit the initializer. Note that this can allow some things that
1703	// are not allowed by tryEmitPrivateForMemory alone.
1704	if (APValue *value = D.evaluateValue())
1705	return tryEmitPrivateForMemory(value: *value, T: destType);
1706
1707	return nullptr;
1708	}
1709
1710	llvm::Constant *
1711	ConstantEmitter::tryEmitAbstractForMemory(const Expr *E, QualType destType) {
1712	auto nonMemoryDestType = getNonMemoryType(CGM, type: destType);
1713	auto C = tryEmitAbstract(E, destType: nonMemoryDestType);
1714	return (C ? emitForMemory(C, T: destType) : nullptr);
1715	}
1716
1717	llvm::Constant *
1718	ConstantEmitter::tryEmitAbstractForMemory(const APValue &value,
1719	QualType destType) {
1720	auto nonMemoryDestType = getNonMemoryType(CGM, type: destType);
1721	auto C = tryEmitAbstract(value, destType: nonMemoryDestType);
1722	return (C ? emitForMemory(C, T: destType) : nullptr);
1723	}
1724
1725	llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const Expr *E,
1726	QualType destType) {
1727	auto nonMemoryDestType = getNonMemoryType(CGM, type: destType);
1728	llvm::Constant *C = tryEmitPrivate(E, T: nonMemoryDestType);
1729	return (C ? emitForMemory(C, T: destType) : nullptr);
1730	}
1731
1732	llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const APValue &value,
1733	QualType destType) {
1734	auto nonMemoryDestType = getNonMemoryType(CGM, type: destType);
1735	auto C = tryEmitPrivate(value, T: nonMemoryDestType);
1736	return (C ? emitForMemory(C, T: destType) : nullptr);
1737	}
1738
1739	llvm::Constant *ConstantEmitter::emitForMemory(CodeGenModule &CGM,
1740	llvm::Constant *C,
1741	QualType destType) {
1742	// For an _Atomic-qualified constant, we may need to add tail padding.
1743	if (auto AT = destType->getAs<AtomicType>()) {
1744	QualType destValueType = AT->getValueType();
1745	C = emitForMemory(CGM, C, destType: destValueType);
1746
1747	uint64_t innerSize = CGM.getContext().getTypeSize(T: destValueType);
1748	uint64_t outerSize = CGM.getContext().getTypeSize(T: destType);
1749	if (innerSize == outerSize)
1750	return C;
1751
1752	assert(innerSize < outerSize && "emitted over-large constant for atomic");
1753	llvm::Constant *elts[] = {
1754	C,
1755	llvm::ConstantAggregateZero::get(
1756	Ty: llvm::ArrayType::get(ElementType: CGM.Int8Ty, NumElements: (outerSize - innerSize) / 8))
1757	};
1758	return llvm::ConstantStruct::getAnon(V: elts);
1759	}
1760
1761	// Zero-extend bool.
1762	if (C->getType()->isIntegerTy(Bitwidth: 1) && !destType->isBitIntType()) {
1763	llvm::Type *boolTy = CGM.getTypes().ConvertTypeForMem(T: destType);
1764	llvm::Constant *Res = llvm::ConstantFoldCastOperand(
1765	Opcode: llvm::Instruction::ZExt, C, DestTy: boolTy, DL: CGM.getDataLayout());
1766	assert(Res && "Constant folding must succeed");
1767	return Res;
1768	}
1769
1770	return C;
1771	}
1772
1773	llvm::Constant *ConstantEmitter::tryEmitPrivate(const Expr *E,
1774	QualType destType) {
1775	assert(!destType->isVoidType() && "can't emit a void constant");
1776
1777	if (!destType->isReferenceType())
1778	if (llvm::Constant *C =
1779	ConstExprEmitter(*this).Visit(const_cast<Expr *>(E), destType))
1780	return C;
1781
1782	Expr::EvalResult Result;
1783
1784	bool Success = false;
1785
1786	if (destType->isReferenceType())
1787	Success = E->EvaluateAsLValue(Result, Ctx: CGM.getContext());
1788	else
1789	Success = E->EvaluateAsRValue(Result, Ctx: CGM.getContext(), InConstantContext);
1790
1791	if (Success && !Result.HasSideEffects)
1792	return tryEmitPrivate(value: Result.Val, T: destType);
1793
1794	return nullptr;
1795	}
1796
1797	llvm::Constant *CodeGenModule::getNullPointer(llvm::PointerType *T, QualType QT) {
1798	return getTargetCodeGenInfo().getNullPointer(CGM: *this, T, QT);
1799	}
1800
1801	namespace {
1802	/// A struct which can be used to peephole certain kinds of finalization
1803	/// that normally happen during l-value emission.
1804	struct ConstantLValue {
1805	llvm::Constant *Value;
1806	bool HasOffsetApplied;
1807
1808	/*implicit*/ ConstantLValue(llvm::Constant *value,
1809	bool hasOffsetApplied = false)
1810	: Value(value), HasOffsetApplied(hasOffsetApplied) {}
1811
1812	/*implicit*/ ConstantLValue(ConstantAddress address)
1813	: ConstantLValue(address.getPointer()) {}
1814	};
1815
1816	/// A helper class for emitting constant l-values.
1817	class ConstantLValueEmitter : public ConstStmtVisitor<ConstantLValueEmitter,
1818	ConstantLValue> {
1819	CodeGenModule &CGM;
1820	ConstantEmitter &Emitter;
1821	const APValue &Value;
1822	QualType DestType;
1823
1824	// Befriend StmtVisitorBase so that we don't have to expose Visit*.
1825	friend StmtVisitorBase;
1826
1827	public:
1828	ConstantLValueEmitter(ConstantEmitter &emitter, const APValue &value,
1829	QualType destType)
1830	: CGM(emitter.CGM), Emitter(emitter), Value(value), DestType(destType) {}
1831
1832	llvm::Constant *tryEmit();
1833
1834	private:
1835	llvm::Constant *tryEmitAbsolute(llvm::Type *destTy);
1836	ConstantLValue tryEmitBase(const APValue::LValueBase &base);
1837
1838	ConstantLValue VisitStmt(const Stmt *S) { return nullptr; }
1839	ConstantLValue VisitConstantExpr(const ConstantExpr *E);
1840	ConstantLValue VisitCompoundLiteralExpr(const CompoundLiteralExpr *E);
1841	ConstantLValue VisitStringLiteral(const StringLiteral *E);
1842	ConstantLValue VisitObjCBoxedExpr(const ObjCBoxedExpr *E);
1843	ConstantLValue VisitObjCEncodeExpr(const ObjCEncodeExpr *E);
1844	ConstantLValue VisitObjCStringLiteral(const ObjCStringLiteral *E);
1845	ConstantLValue VisitPredefinedExpr(const PredefinedExpr *E);
1846	ConstantLValue VisitAddrLabelExpr(const AddrLabelExpr *E);
1847	ConstantLValue VisitCallExpr(const CallExpr *E);
1848	ConstantLValue VisitBlockExpr(const BlockExpr *E);
1849	ConstantLValue VisitCXXTypeidExpr(const CXXTypeidExpr *E);
1850	ConstantLValue VisitMaterializeTemporaryExpr(
1851	const MaterializeTemporaryExpr *E);
1852
1853	bool hasNonZeroOffset() const {
1854	return !Value.getLValueOffset().isZero();
1855	}
1856
1857	/// Return the value offset.
1858	llvm::Constant *getOffset() {
1859	return llvm::ConstantInt::get(Ty: CGM.Int64Ty,
1860	V: Value.getLValueOffset().getQuantity());
1861	}
1862
1863	/// Apply the value offset to the given constant.
1864	llvm::Constant *applyOffset(llvm::Constant *C) {
1865	if (!hasNonZeroOffset())
1866	return C;
1867
1868	return llvm::ConstantExpr::getGetElementPtr(Ty: CGM.Int8Ty, C, Idx: getOffset());
1869	}
1870	};
1871
1872	}
1873
1874	llvm::Constant *ConstantLValueEmitter::tryEmit() {
1875	const APValue::LValueBase &base = Value.getLValueBase();
1876
1877	// The destination type should be a pointer or reference
1878	// type, but it might also be a cast thereof.
1879	//
1880	// FIXME: the chain of casts required should be reflected in the APValue.
1881	// We need this in order to correctly handle things like a ptrtoint of a
1882	// non-zero null pointer and addrspace casts that aren't trivially
1883	// represented in LLVM IR.
1884	auto destTy = CGM.getTypes().ConvertTypeForMem(DestType);
1885	assert(isa<llvm::IntegerType>(destTy) || isa<llvm::PointerType>(destTy));
1886
1887	// If there's no base at all, this is a null or absolute pointer,
1888	// possibly cast back to an integer type.
1889	if (!base) {
1890	return tryEmitAbsolute(destTy: destTy);
1891	}
1892
1893	// Otherwise, try to emit the base.
1894	ConstantLValue result = tryEmitBase(base);
1895
1896	// If that failed, we're done.
1897	llvm::Constant *value = result.Value;
1898	if (!value) return nullptr;
1899
1900	// Apply the offset if necessary and not already done.
1901	if (!result.HasOffsetApplied) {
1902	value = applyOffset(C: value);
1903	}
1904
1905	// Convert to the appropriate type; this could be an lvalue for
1906	// an integer. FIXME: performAddrSpaceCast
1907	if (isa<llvm::PointerType>(destTy))
1908	return llvm::ConstantExpr::getPointerCast(C: value, Ty: destTy);
1909
1910	return llvm::ConstantExpr::getPtrToInt(C: value, Ty: destTy);
1911	}
1912
1913	/// Try to emit an absolute l-value, such as a null pointer or an integer
1914	/// bitcast to pointer type.
1915	llvm::Constant *
1916	ConstantLValueEmitter::tryEmitAbsolute(llvm::Type *destTy) {
1917	// If we're producing a pointer, this is easy.
1918	auto destPtrTy = cast<llvm::PointerType>(Val: destTy);
1919	if (Value.isNullPointer()) {
1920	// FIXME: integer offsets from non-zero null pointers.
1921	return CGM.getNullPointer(destPtrTy, DestType);
1922	}
1923
1924	// Convert the integer to a pointer-sized integer before converting it
1925	// to a pointer.
1926	// FIXME: signedness depends on the original integer type.
1927	auto intptrTy = CGM.getDataLayout().getIntPtrType(destPtrTy);
1928	llvm::Constant *C;
1929	C = llvm::ConstantFoldIntegerCast(C: getOffset(), DestTy: intptrTy, /*isSigned*/ IsSigned: false,
1930	DL: CGM.getDataLayout());
1931	assert(C && "Must have folded, as Offset is a ConstantInt");
1932	C = llvm::ConstantExpr::getIntToPtr(C, Ty: destPtrTy);
1933	return C;
1934	}
1935
1936	ConstantLValue
1937	ConstantLValueEmitter::tryEmitBase(const APValue::LValueBase &base) {
1938	// Handle values.
1939	if (const ValueDecl *D = base.dyn_cast<const ValueDecl*>()) {
1940	// The constant always points to the canonical declaration. We want to look
1941	// at properties of the most recent declaration at the point of emission.
1942	D = cast<ValueDecl>(D->getMostRecentDecl());
1943
1944	if (D->hasAttr<WeakRefAttr>())
1945	return CGM.GetWeakRefReference(VD: D).getPointer();
1946
1947	if (auto FD = dyn_cast<FunctionDecl>(Val: D))
1948	return CGM.GetAddrOfFunction(GD: FD);
1949
1950	if (auto VD = dyn_cast<VarDecl>(Val: D)) {
1951	// We can never refer to a variable with local storage.
1952	if (!VD->hasLocalStorage()) {
1953	if (VD->isFileVarDecl() || VD->hasExternalStorage())
1954	return CGM.GetAddrOfGlobalVar(D: VD);
1955
1956	if (VD->isLocalVarDecl()) {
1957	return CGM.getOrCreateStaticVarDecl(
1958	D: *VD, Linkage: CGM.getLLVMLinkageVarDefinition(VD));
1959	}
1960	}
1961	}
1962
1963	if (auto *GD = dyn_cast<MSGuidDecl>(Val: D))
1964	return CGM.GetAddrOfMSGuidDecl(GD);
1965
1966	if (auto *GCD = dyn_cast<UnnamedGlobalConstantDecl>(Val: D))
1967	return CGM.GetAddrOfUnnamedGlobalConstantDecl(GCD);
1968
1969	if (auto *TPO = dyn_cast<TemplateParamObjectDecl>(Val: D))
1970	return CGM.GetAddrOfTemplateParamObject(TPO);
1971
1972	return nullptr;
1973	}
1974
1975	// Handle typeid(T).
1976	if (TypeInfoLValue TI = base.dyn_cast<TypeInfoLValue>())
1977	return CGM.GetAddrOfRTTIDescriptor(Ty: QualType(TI.getType(), 0));
1978
1979	// Otherwise, it must be an expression.
1980	return Visit(base.get<const Expr*>());
1981	}
1982
1983	ConstantLValue
1984	ConstantLValueEmitter::VisitConstantExpr(const ConstantExpr *E) {
1985	if (llvm::Constant *Result = Emitter.tryEmitConstantExpr(CE: E))
1986	return Result;
1987	return Visit(E->getSubExpr());
1988	}
1989
1990	ConstantLValue
1991	ConstantLValueEmitter::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
1992	ConstantEmitter CompoundLiteralEmitter(CGM, Emitter.CGF);
1993	CompoundLiteralEmitter.setInConstantContext(Emitter.isInConstantContext());
1994	return tryEmitGlobalCompoundLiteral(emitter&: CompoundLiteralEmitter, E);
1995	}
1996
1997	ConstantLValue
1998	ConstantLValueEmitter::VisitStringLiteral(const StringLiteral *E) {
1999	return CGM.GetAddrOfConstantStringFromLiteral(S: E);
2000	}
2001
2002	ConstantLValue
2003	ConstantLValueEmitter::VisitObjCEncodeExpr(const ObjCEncodeExpr *E) {
2004	return CGM.GetAddrOfConstantStringFromObjCEncode(E);
2005	}
2006
2007	static ConstantLValue emitConstantObjCStringLiteral(const StringLiteral *S,
2008	QualType T,
2009	CodeGenModule &CGM) {
2010	auto C = CGM.getObjCRuntime().GenerateConstantString(S);
2011	return C.withElementType(ElemTy: CGM.getTypes().ConvertTypeForMem(T));
2012	}
2013
2014	ConstantLValue
2015	ConstantLValueEmitter::VisitObjCStringLiteral(const ObjCStringLiteral *E) {
2016	return emitConstantObjCStringLiteral(E->getString(), E->getType(), CGM);
2017	}
2018
2019	ConstantLValue
2020	ConstantLValueEmitter::VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
2021	assert(E->isExpressibleAsConstantInitializer() &&
2022	"this boxed expression can't be emitted as a compile-time constant");
2023	auto *SL = cast<StringLiteral>(Val: E->getSubExpr()->IgnoreParenCasts());
2024	return emitConstantObjCStringLiteral(SL, E->getType(), CGM);
2025	}
2026
2027	ConstantLValue
2028	ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) {
2029	return CGM.GetAddrOfConstantStringFromLiteral(S: E->getFunctionName());
2030	}
2031
2032	ConstantLValue
2033	ConstantLValueEmitter::VisitAddrLabelExpr(const AddrLabelExpr *E) {
2034	assert(Emitter.CGF && "Invalid address of label expression outside function");
2035	llvm::Constant *Ptr = Emitter.CGF->GetAddrOfLabel(L: E->getLabel());
2036	return Ptr;
2037	}
2038
2039	ConstantLValue
2040	ConstantLValueEmitter::VisitCallExpr(const CallExpr *E) {
2041	unsigned builtin = E->getBuiltinCallee();
2042	if (builtin == Builtin::BI__builtin_function_start)
2043	return CGM.GetFunctionStart(
2044	Decl: E->getArg(Arg: 0)->getAsBuiltinConstantDeclRef(Context: CGM.getContext()));
2045	if (builtin != Builtin::BI__builtin___CFStringMakeConstantString &&
2046	builtin != Builtin::BI__builtin___NSStringMakeConstantString)
2047	return nullptr;
2048
2049	auto literal = cast<StringLiteral>(Val: E->getArg(Arg: 0)->IgnoreParenCasts());
2050	if (builtin == Builtin::BI__builtin___NSStringMakeConstantString) {
2051	return CGM.getObjCRuntime().GenerateConstantString(literal);
2052	} else {
2053	// FIXME: need to deal with UCN conversion issues.
2054	return CGM.GetAddrOfConstantCFString(Literal: literal);
2055	}
2056	}
2057
2058	ConstantLValue
2059	ConstantLValueEmitter::VisitBlockExpr(const BlockExpr *E) {
2060	StringRef functionName;
2061	if (auto CGF = Emitter.CGF)
2062	functionName = CGF->CurFn->getName();
2063	else
2064	functionName = "global";
2065
2066	return CGM.GetAddrOfGlobalBlock(BE: E, Name: functionName);
2067	}
2068
2069	ConstantLValue
2070	ConstantLValueEmitter::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
2071	QualType T;
2072	if (E->isTypeOperand())
2073	T = E->getTypeOperand(Context&: CGM.getContext());
2074	else
2075	T = E->getExprOperand()->getType();
2076	return CGM.GetAddrOfRTTIDescriptor(Ty: T);
2077	}
2078
2079	ConstantLValue
2080	ConstantLValueEmitter::VisitMaterializeTemporaryExpr(
2081	const MaterializeTemporaryExpr *E) {
2082	assert(E->getStorageDuration() == SD_Static);
2083	const Expr *Inner = E->getSubExpr()->skipRValueSubobjectAdjustments();
2084	return CGM.GetAddrOfGlobalTemporary(E, Inner);
2085	}
2086
2087	llvm::Constant *ConstantEmitter::tryEmitPrivate(const APValue &Value,
2088	QualType DestType) {
2089	switch (Value.getKind()) {
2090	case APValue::None:
2091	case APValue::Indeterminate:
2092	// Out-of-lifetime and indeterminate values can be modeled as 'undef'.
2093	return llvm::UndefValue::get(T: CGM.getTypes().ConvertType(T: DestType));
2094	case APValue::LValue:
2095	return ConstantLValueEmitter(*this, Value, DestType).tryEmit();
2096	case APValue::Int:
2097	return llvm::ConstantInt::get(Context&: CGM.getLLVMContext(), V: Value.getInt());
2098	case APValue::FixedPoint:
2099	return llvm::ConstantInt::get(Context&: CGM.getLLVMContext(),
2100	V: Value.getFixedPoint().getValue());
2101	case APValue::ComplexInt: {
2102	llvm::Constant *Complex[2];
2103
2104	Complex[0] = llvm::ConstantInt::get(Context&: CGM.getLLVMContext(),
2105	V: Value.getComplexIntReal());
2106	Complex[1] = llvm::ConstantInt::get(Context&: CGM.getLLVMContext(),
2107	V: Value.getComplexIntImag());
2108
2109	// FIXME: the target may want to specify that this is packed.
2110	llvm::StructType *STy =
2111	llvm::StructType::get(elt1: Complex[0]->getType(), elts: Complex[1]->getType());
2112	return llvm::ConstantStruct::get(T: STy, V: Complex);
2113	}
2114	case APValue::Float: {
2115	const llvm::APFloat &Init = Value.getFloat();
2116	if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf() &&
2117	!CGM.getContext().getLangOpts().NativeHalfType &&
2118	CGM.getContext().getTargetInfo().useFP16ConversionIntrinsics())
2119	return llvm::ConstantInt::get(Context&: CGM.getLLVMContext(),
2120	V: Init.bitcastToAPInt());
2121	else
2122	return llvm::ConstantFP::get(Context&: CGM.getLLVMContext(), V: Init);
2123	}
2124	case APValue::ComplexFloat: {
2125	llvm::Constant *Complex[2];
2126
2127	Complex[0] = llvm::ConstantFP::get(Context&: CGM.getLLVMContext(),
2128	V: Value.getComplexFloatReal());
2129	Complex[1] = llvm::ConstantFP::get(Context&: CGM.getLLVMContext(),
2130	V: Value.getComplexFloatImag());
2131
2132	// FIXME: the target may want to specify that this is packed.
2133	llvm::StructType *STy =
2134	llvm::StructType::get(elt1: Complex[0]->getType(), elts: Complex[1]->getType());
2135	return llvm::ConstantStruct::get(T: STy, V: Complex);
2136	}
2137	case APValue::Vector: {
2138	unsigned NumElts = Value.getVectorLength();
2139	SmallVector<llvm::Constant *, 4> Inits(NumElts);
2140
2141	for (unsigned I = 0; I != NumElts; ++I) {
2142	const APValue &Elt = Value.getVectorElt(I);
2143	if (Elt.isInt())
2144	Inits[I] = llvm::ConstantInt::get(Context&: CGM.getLLVMContext(), V: Elt.getInt());
2145	else if (Elt.isFloat())
2146	Inits[I] = llvm::ConstantFP::get(Context&: CGM.getLLVMContext(), V: Elt.getFloat());
2147	else if (Elt.isIndeterminate())
2148	Inits[I] = llvm::UndefValue::get(T: CGM.getTypes().ConvertType(
2149	T: DestType->castAs<VectorType>()->getElementType()));
2150	else
2151	llvm_unreachable("unsupported vector element type");
2152	}
2153	return llvm::ConstantVector::get(V: Inits);
2154	}
2155	case APValue::AddrLabelDiff: {
2156	const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS();
2157	const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS();
2158	llvm::Constant *LHS = tryEmitPrivate(LHSExpr, LHSExpr->getType());
2159	llvm::Constant *RHS = tryEmitPrivate(RHSExpr, RHSExpr->getType());
2160	if (!LHS || !RHS) return nullptr;
2161
2162	// Compute difference
2163	llvm::Type *ResultType = CGM.getTypes().ConvertType(T: DestType);
2164	LHS = llvm::ConstantExpr::getPtrToInt(C: LHS, Ty: CGM.IntPtrTy);
2165	RHS = llvm::ConstantExpr::getPtrToInt(C: RHS, Ty: CGM.IntPtrTy);
2166	llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(C1: LHS, C2: RHS);
2167
2168	// LLVM is a bit sensitive about the exact format of the
2169	// address-of-label difference; make sure to truncate after
2170	// the subtraction.
2171	return llvm::ConstantExpr::getTruncOrBitCast(C: AddrLabelDiff, Ty: ResultType);
2172	}
2173	case APValue::Struct:
2174	case APValue::Union:
2175	return ConstStructBuilder::BuildStruct(Emitter&: *this, Val: Value, ValTy: DestType);
2176	case APValue::Array: {
2177	const ArrayType *ArrayTy = CGM.getContext().getAsArrayType(T: DestType);
2178	unsigned NumElements = Value.getArraySize();
2179	unsigned NumInitElts = Value.getArrayInitializedElts();
2180
2181	// Emit array filler, if there is one.
2182	llvm::Constant *Filler = nullptr;
2183	if (Value.hasArrayFiller()) {
2184	Filler = tryEmitAbstractForMemory(value: Value.getArrayFiller(),
2185	destType: ArrayTy->getElementType());
2186	if (!Filler)
2187	return nullptr;
2188	}
2189
2190	// Emit initializer elements.
2191	SmallVector<llvm::Constant*, 16> Elts;
2192	if (Filler && Filler->isNullValue())
2193	Elts.reserve(N: NumInitElts + 1);
2194	else
2195	Elts.reserve(N: NumElements);
2196
2197	llvm::Type *CommonElementType = nullptr;
2198	for (unsigned I = 0; I < NumInitElts; ++I) {
2199	llvm::Constant *C = tryEmitPrivateForMemory(
2200	value: Value.getArrayInitializedElt(I), destType: ArrayTy->getElementType());
2201	if (!C) return nullptr;
2202
2203	if (I == 0)
2204	CommonElementType = C->getType();
2205	else if (C->getType() != CommonElementType)
2206	CommonElementType = nullptr;
2207	Elts.push_back(Elt: C);
2208	}
2209
2210	llvm::ArrayType *Desired =
2211	cast<llvm::ArrayType>(Val: CGM.getTypes().ConvertType(T: DestType));
2212
2213	// Fix the type of incomplete arrays if the initializer isn't empty.
2214	if (DestType->isIncompleteArrayType() && !Elts.empty())
2215	Desired = llvm::ArrayType::get(ElementType: Desired->getElementType(), NumElements: Elts.size());
2216
2217	return EmitArrayConstant(CGM, DesiredType: Desired, CommonElementType, ArrayBound: NumElements, Elements&: Elts,
2218	Filler);
2219	}
2220	case APValue::MemberPointer:
2221	return CGM.getCXXABI().EmitMemberPointer(MP: Value, MPT: DestType);
2222	}
2223	llvm_unreachable("Unknown APValue kind");
2224	}
2225
2226	llvm::GlobalVariable *CodeGenModule::getAddrOfConstantCompoundLiteralIfEmitted(
2227	const CompoundLiteralExpr *E) {
2228	return EmittedCompoundLiterals.lookup(Val: E);
2229	}
2230
2231	void CodeGenModule::setAddrOfConstantCompoundLiteral(
2232	const CompoundLiteralExpr *CLE, llvm::GlobalVariable *GV) {
2233	bool Ok = EmittedCompoundLiterals.insert(KV: std::make_pair(x&: CLE, y&: GV)).second;
2234	(void)Ok;
2235	assert(Ok && "CLE has already been emitted!");
2236	}
2237
2238	ConstantAddress
2239	CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) {
2240	assert(E->isFileScope() && "not a file-scope compound literal expr");
2241	ConstantEmitter emitter(*this);
2242	return tryEmitGlobalCompoundLiteral(emitter, E);
2243	}
2244
2245	llvm::Constant *
2246	CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
2247	// Member pointer constants always have a very particular form.
2248	const MemberPointerType *type = cast<MemberPointerType>(uo->getType());
2249	const ValueDecl *decl = cast<DeclRefExpr>(Val: uo->getSubExpr())->getDecl();
2250
2251	// A member function pointer.
2252	if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(Val: decl))
2253	return getCXXABI().EmitMemberFunctionPointer(MD: method);
2254
2255	// Otherwise, a member data pointer.
2256	uint64_t fieldOffset = getContext().getFieldOffset(FD: decl);
2257	CharUnits chars = getContext().toCharUnitsFromBits(BitSize: (int64_t) fieldOffset);
2258	return getCXXABI().EmitMemberDataPointer(MPT: type, offset: chars);
2259	}
2260
2261	static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
2262	llvm::Type *baseType,
2263	const CXXRecordDecl *base);
2264
2265	static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
2266	const RecordDecl *record,
2267	bool asCompleteObject) {
2268	const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
2269	llvm::StructType *structure =
2270	(asCompleteObject ? layout.getLLVMType()
2271	: layout.getBaseSubobjectLLVMType());
2272
2273	unsigned numElements = structure->getNumElements();
2274	std::vector<llvm::Constant *> elements(numElements);
2275
2276	auto CXXR = dyn_cast<CXXRecordDecl>(Val: record);
2277	// Fill in all the bases.
2278	if (CXXR) {
2279	for (const auto &I : CXXR->bases()) {
2280	if (I.isVirtual()) {
2281	// Ignore virtual bases; if we're laying out for a complete
2282	// object, we'll lay these out later.
2283	continue;
2284	}
2285
2286	const CXXRecordDecl *base =
2287	cast<CXXRecordDecl>(Val: I.getType()->castAs<RecordType>()->getDecl());
2288
2289	// Ignore empty bases.
2290	if (base->isEmpty() ||
2291	CGM.getContext().getASTRecordLayout(base).getNonVirtualSize()
2292	.isZero())
2293	continue;
2294
2295	unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(RD: base);
2296	llvm::Type *baseType = structure->getElementType(N: fieldIndex);
2297	elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
2298	}
2299	}
2300
2301	// Fill in all the fields.
2302	for (const auto *Field : record->fields()) {
2303	// Fill in non-bitfields. (Bitfields always use a zero pattern, which we
2304	// will fill in later.)
2305	if (!Field->isBitField() && !Field->isZeroSize(Ctx: CGM.getContext())) {
2306	unsigned fieldIndex = layout.getLLVMFieldNo(FD: Field);
2307	elements[fieldIndex] = CGM.EmitNullConstant(T: Field->getType());
2308	}
2309
2310	// For unions, stop after the first named field.
2311	if (record->isUnion()) {
2312	if (Field->getIdentifier())
2313	break;
2314	if (const auto *FieldRD = Field->getType()->getAsRecordDecl())
2315	if (FieldRD->findFirstNamedDataMember())
2316	break;
2317	}
2318	}
2319
2320	// Fill in the virtual bases, if we're working with the complete object.
2321	if (CXXR && asCompleteObject) {
2322	for (const auto &I : CXXR->vbases()) {
2323	const CXXRecordDecl *base =
2324	cast<CXXRecordDecl>(Val: I.getType()->castAs<RecordType>()->getDecl());
2325
2326	// Ignore empty bases.
2327	if (base->isEmpty())
2328	continue;
2329
2330	unsigned fieldIndex = layout.getVirtualBaseIndex(base);
2331
2332	// We might have already laid this field out.
2333	if (elements[fieldIndex]) continue;
2334
2335	llvm::Type *baseType = structure->getElementType(N: fieldIndex);
2336	elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
2337	}
2338	}
2339
2340	// Now go through all other fields and zero them out.
2341	for (unsigned i = 0; i != numElements; ++i) {
2342	if (!elements[i])
2343	elements[i] = llvm::Constant::getNullValue(Ty: structure->getElementType(N: i));
2344	}
2345
2346	return llvm::ConstantStruct::get(T: structure, V: elements);
2347	}
2348
2349	/// Emit the null constant for a base subobject.
2350	static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
2351	llvm::Type *baseType,
2352	const CXXRecordDecl *base) {
2353	const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
2354
2355	// Just zero out bases that don't have any pointer to data members.
2356	if (baseLayout.isZeroInitializableAsBase())
2357	return llvm::Constant::getNullValue(Ty: baseType);
2358
2359	// Otherwise, we can just use its null constant.
2360	return EmitNullConstant(CGM, base, /*asCompleteObject=*/false);
2361	}
2362
2363	llvm::Constant *ConstantEmitter::emitNullForMemory(CodeGenModule &CGM,
2364	QualType T) {
2365	return emitForMemory(CGM, C: CGM.EmitNullConstant(T), destType: T);
2366	}
2367
2368	llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
2369	if (T->getAs<PointerType>())
2370	return getNullPointer(
2371	T: cast<llvm::PointerType>(Val: getTypes().ConvertTypeForMem(T)), QT: T);
2372
2373	if (getTypes().isZeroInitializable(T))
2374	return llvm::Constant::getNullValue(Ty: getTypes().ConvertTypeForMem(T));
2375
2376	if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
2377	llvm::ArrayType *ATy =
2378	cast<llvm::ArrayType>(Val: getTypes().ConvertTypeForMem(T));
2379
2380	QualType ElementTy = CAT->getElementType();
2381
2382	llvm::Constant *Element =
2383	ConstantEmitter::emitNullForMemory(CGM&: *this, T: ElementTy);
2384	unsigned NumElements = CAT->getSize().getZExtValue();
2385	SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
2386	return llvm::ConstantArray::get(T: ATy, V: Array);
2387	}
2388
2389	if (const RecordType *RT = T->getAs<RecordType>())
2390	return ::EmitNullConstant(CGM&: *this, record: RT->getDecl(), /*complete object*/ asCompleteObject: true);
2391
2392	assert(T->isMemberDataPointerType() &&
2393	"Should only see pointers to data members here!");
2394
2395	return getCXXABI().EmitNullMemberPointer(MPT: T->castAs<MemberPointerType>());
2396	}
2397
2398	llvm::Constant *
2399	CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
2400	return ::EmitNullConstant(*this, Record, false);
2401	}
2402