1//===-- llvm/CodeGen/GlobalISel/CSEMIRBuilder.cpp - MIBuilder--*- C++ -*-==//
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/// \file
9/// This file implements the CSEMIRBuilder class which CSEs as it builds
10/// instructions.
11//===----------------------------------------------------------------------===//
12//
13
14#include "llvm/CodeGen/GlobalISel/CSEMIRBuilder.h"
15#include "llvm/CodeGen/GlobalISel/CSEInfo.h"
16#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
17#include "llvm/CodeGen/GlobalISel/Utils.h"
18#include "llvm/CodeGen/MachineInstrBuilder.h"
19#include "llvm/IR/DebugInfoMetadata.h"
20
21using namespace llvm;
22
23bool CSEMIRBuilder::dominates(MachineBasicBlock::const_iterator A,
24 MachineBasicBlock::const_iterator B) const {
25 auto MBBEnd = getMBB().end();
26 if (B == MBBEnd)
27 return true;
28 assert(A->getParent() == B->getParent() &&
29 "Iterators should be in same block");
30 const MachineBasicBlock *BBA = A->getParent();
31 MachineBasicBlock::const_iterator I = BBA->begin();
32 for (; &*I != A && &*I != B; ++I)
33 ;
34 return &*I == A;
35}
36
37MachineInstrBuilder
38CSEMIRBuilder::getDominatingInstrForID(FoldingSetNodeID &ID,
39 void *&NodeInsertPos) {
40 GISelCSEInfo *CSEInfo = getCSEInfo();
41 assert(CSEInfo && "Can't get here without setting CSEInfo");
42 MachineBasicBlock *CurMBB = &getMBB();
43 MachineInstr *MI =
44 CSEInfo->getMachineInstrIfExists(ID, MBB: CurMBB, InsertPos&: NodeInsertPos);
45 if (MI) {
46 CSEInfo->countOpcodeHit(Opc: MI->getOpcode());
47 auto CurrPos = getInsertPt();
48 auto MII = MachineBasicBlock::iterator(MI);
49 if (MII == CurrPos) {
50 // Move the insert point ahead of the instruction so any future uses of
51 // this builder will have the def ready.
52 setInsertPt(MBB&: *CurMBB, II: std::next(x: MII));
53 } else if (!dominates(A: MI, B: CurrPos)) {
54 CurMBB->splice(Where: CurrPos, Other: CurMBB, From: MI);
55 }
56 return MachineInstrBuilder(getMF(), MI);
57 }
58 return MachineInstrBuilder();
59}
60
61bool CSEMIRBuilder::canPerformCSEForOpc(unsigned Opc) const {
62 const GISelCSEInfo *CSEInfo = getCSEInfo();
63 if (!CSEInfo || !CSEInfo->shouldCSE(Opc))
64 return false;
65 return true;
66}
67
68void CSEMIRBuilder::profileDstOp(const DstOp &Op,
69 GISelInstProfileBuilder &B) const {
70 switch (Op.getDstOpKind()) {
71 case DstOp::DstType::Ty_RC:
72 B.addNodeIDRegType(RC: Op.getRegClass());
73 break;
74 case DstOp::DstType::Ty_Reg: {
75 // Regs can have LLT&(RB|RC). If those exist, profile them as well.
76 B.addNodeIDReg(Reg: Op.getReg());
77 break;
78 }
79 default:
80 B.addNodeIDRegType(Ty: Op.getLLTTy(MRI: *getMRI()));
81 break;
82 }
83}
84
85void CSEMIRBuilder::profileSrcOp(const SrcOp &Op,
86 GISelInstProfileBuilder &B) const {
87 switch (Op.getSrcOpKind()) {
88 case SrcOp::SrcType::Ty_Imm:
89 B.addNodeIDImmediate(Imm: static_cast<int64_t>(Op.getImm()));
90 break;
91 case SrcOp::SrcType::Ty_Predicate:
92 B.addNodeIDImmediate(Imm: static_cast<int64_t>(Op.getPredicate()));
93 break;
94 default:
95 B.addNodeIDRegType(Op.getReg());
96 break;
97 }
98}
99
100void CSEMIRBuilder::profileMBBOpcode(GISelInstProfileBuilder &B,
101 unsigned Opc) const {
102 // First add the MBB (Local CSE).
103 B.addNodeIDMBB(MBB: &getMBB());
104 // Then add the opcode.
105 B.addNodeIDOpcode(Opc);
106}
107
108void CSEMIRBuilder::profileEverything(unsigned Opc, ArrayRef<DstOp> DstOps,
109 ArrayRef<SrcOp> SrcOps,
110 std::optional<unsigned> Flags,
111 GISelInstProfileBuilder &B) const {
112
113 profileMBBOpcode(B, Opc);
114 // Then add the DstOps.
115 profileDstOps(Ops: DstOps, B);
116 // Then add the SrcOps.
117 profileSrcOps(Ops: SrcOps, B);
118 // Add Flags if passed in.
119 if (Flags)
120 B.addNodeIDFlag(Flag: *Flags);
121}
122
123MachineInstrBuilder CSEMIRBuilder::memoizeMI(MachineInstrBuilder MIB,
124 void *NodeInsertPos) {
125 assert(canPerformCSEForOpc(MIB->getOpcode()) &&
126 "Attempting to CSE illegal op");
127 MachineInstr *MIBInstr = MIB;
128 getCSEInfo()->insertInstr(MI: MIBInstr, InsertPos: NodeInsertPos);
129 return MIB;
130}
131
132bool CSEMIRBuilder::checkCopyToDefsPossible(ArrayRef<DstOp> DstOps) {
133 if (DstOps.size() == 1)
134 return true; // always possible to emit copy to just 1 vreg.
135
136 return llvm::all_of(Range&: DstOps, P: [](const DstOp &Op) {
137 DstOp::DstType DT = Op.getDstOpKind();
138 return DT == DstOp::DstType::Ty_LLT || DT == DstOp::DstType::Ty_RC;
139 });
140}
141
142MachineInstrBuilder
143CSEMIRBuilder::generateCopiesIfRequired(ArrayRef<DstOp> DstOps,
144 MachineInstrBuilder &MIB) {
145 assert(checkCopyToDefsPossible(DstOps) &&
146 "Impossible return a single MIB with copies to multiple defs");
147 if (DstOps.size() == 1) {
148 const DstOp &Op = DstOps[0];
149 if (Op.getDstOpKind() == DstOp::DstType::Ty_Reg)
150 return buildCopy(Res: Op.getReg(), Op: MIB.getReg(Idx: 0));
151 }
152
153 // If we didn't generate a copy then we're re-using an existing node directly
154 // instead of emitting any code. Merge the debug location we wanted to emit
155 // into the instruction we're CSE'ing with. Debug locations arent part of the
156 // profile so we don't need to recompute it.
157 if (getDebugLoc()) {
158 GISelChangeObserver *Observer = getState().Observer;
159 if (Observer)
160 Observer->changingInstr(MI&: *MIB);
161 MIB->setDebugLoc(
162 DILocation::getMergedLocation(LocA: MIB->getDebugLoc(), LocB: getDebugLoc()));
163 if (Observer)
164 Observer->changedInstr(MI&: *MIB);
165 }
166
167 return MIB;
168}
169
170MachineInstrBuilder CSEMIRBuilder::buildInstr(unsigned Opc,
171 ArrayRef<DstOp> DstOps,
172 ArrayRef<SrcOp> SrcOps,
173 std::optional<unsigned> Flag) {
174 switch (Opc) {
175 default:
176 break;
177 case TargetOpcode::G_ADD:
178 case TargetOpcode::G_PTR_ADD:
179 case TargetOpcode::G_AND:
180 case TargetOpcode::G_ASHR:
181 case TargetOpcode::G_LSHR:
182 case TargetOpcode::G_MUL:
183 case TargetOpcode::G_OR:
184 case TargetOpcode::G_SHL:
185 case TargetOpcode::G_SUB:
186 case TargetOpcode::G_XOR:
187 case TargetOpcode::G_UDIV:
188 case TargetOpcode::G_SDIV:
189 case TargetOpcode::G_UREM:
190 case TargetOpcode::G_SREM:
191 case TargetOpcode::G_SMIN:
192 case TargetOpcode::G_SMAX:
193 case TargetOpcode::G_UMIN:
194 case TargetOpcode::G_UMAX: {
195 // Try to constant fold these.
196 assert(SrcOps.size() == 2 && "Invalid sources");
197 assert(DstOps.size() == 1 && "Invalid dsts");
198 LLT SrcTy = SrcOps[0].getLLTTy(MRI: *getMRI());
199
200 if (Opc == TargetOpcode::G_PTR_ADD &&
201 getDataLayout().isNonIntegralAddressSpace(AddrSpace: SrcTy.getAddressSpace()))
202 break;
203
204 if (SrcTy.isVector()) {
205 // Try to constant fold vector constants.
206 SmallVector<APInt> VecCst = ConstantFoldVectorBinop(
207 Opcode: Opc, Op1: SrcOps[0].getReg(), Op2: SrcOps[1].getReg(), MRI: *getMRI());
208 if (!VecCst.empty())
209 return buildBuildVectorConstant(Res: DstOps[0], Ops: VecCst);
210 break;
211 }
212
213 if (std::optional<APInt> Cst = ConstantFoldBinOp(
214 Opcode: Opc, Op1: SrcOps[0].getReg(), Op2: SrcOps[1].getReg(), MRI: *getMRI()))
215 return buildConstant(Res: DstOps[0], Val: *Cst);
216 break;
217 }
218 case TargetOpcode::G_FADD:
219 case TargetOpcode::G_FSUB:
220 case TargetOpcode::G_FMUL:
221 case TargetOpcode::G_FDIV:
222 case TargetOpcode::G_FREM:
223 case TargetOpcode::G_FMINNUM:
224 case TargetOpcode::G_FMAXNUM:
225 case TargetOpcode::G_FMINNUM_IEEE:
226 case TargetOpcode::G_FMAXNUM_IEEE:
227 case TargetOpcode::G_FMINIMUM:
228 case TargetOpcode::G_FMAXIMUM:
229 case TargetOpcode::G_FCOPYSIGN: {
230 // Try to constant fold these.
231 assert(SrcOps.size() == 2 && "Invalid sources");
232 assert(DstOps.size() == 1 && "Invalid dsts");
233 if (std::optional<APFloat> Cst = ConstantFoldFPBinOp(
234 Opcode: Opc, Op1: SrcOps[0].getReg(), Op2: SrcOps[1].getReg(), MRI: *getMRI()))
235 return buildFConstant(Res: DstOps[0], Val: *Cst);
236 break;
237 }
238 case TargetOpcode::G_SEXT_INREG: {
239 assert(DstOps.size() == 1 && "Invalid dst ops");
240 assert(SrcOps.size() == 2 && "Invalid src ops");
241 const DstOp &Dst = DstOps[0];
242 const SrcOp &Src0 = SrcOps[0];
243 const SrcOp &Src1 = SrcOps[1];
244 if (auto MaybeCst =
245 ConstantFoldExtOp(Opcode: Opc, Op1: Src0.getReg(), Imm: Src1.getImm(), MRI: *getMRI()))
246 return buildConstant(Res: Dst, Val: *MaybeCst);
247 break;
248 }
249 case TargetOpcode::G_SITOFP:
250 case TargetOpcode::G_UITOFP: {
251 // Try to constant fold these.
252 assert(SrcOps.size() == 1 && "Invalid sources");
253 assert(DstOps.size() == 1 && "Invalid dsts");
254 if (std::optional<APFloat> Cst = ConstantFoldIntToFloat(
255 Opcode: Opc, DstTy: DstOps[0].getLLTTy(MRI: *getMRI()), Src: SrcOps[0].getReg(), MRI: *getMRI()))
256 return buildFConstant(Res: DstOps[0], Val: *Cst);
257 break;
258 }
259 case TargetOpcode::G_CTLZ: {
260 assert(SrcOps.size() == 1 && "Expected one source");
261 assert(DstOps.size() == 1 && "Expected one dest");
262 auto MaybeCsts = ConstantFoldCTLZ(Src: SrcOps[0].getReg(), MRI: *getMRI());
263 if (!MaybeCsts)
264 break;
265 if (MaybeCsts->size() == 1)
266 return buildConstant(Res: DstOps[0], Val: (*MaybeCsts)[0]);
267 // This was a vector constant. Build a G_BUILD_VECTOR for them.
268 SmallVector<Register> ConstantRegs;
269 LLT VecTy = DstOps[0].getLLTTy(MRI: *getMRI());
270 for (unsigned Cst : *MaybeCsts)
271 ConstantRegs.emplace_back(
272 Args: buildConstant(Res: VecTy.getScalarType(), Val: Cst).getReg(Idx: 0));
273 return buildBuildVector(Res: DstOps[0], Ops: ConstantRegs);
274 }
275 }
276 bool CanCopy = checkCopyToDefsPossible(DstOps);
277 if (!canPerformCSEForOpc(Opc))
278 return MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flags: Flag);
279 // If we can CSE this instruction, but involves generating copies to multiple
280 // regs, give up. This frequently happens to UNMERGEs.
281 if (!CanCopy) {
282 auto MIB = MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flags: Flag);
283 // CSEInfo would have tracked this instruction. Remove it from the temporary
284 // insts.
285 getCSEInfo()->handleRemoveInst(MI: &*MIB);
286 return MIB;
287 }
288 FoldingSetNodeID ID;
289 GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
290 void *InsertPos = nullptr;
291 profileEverything(Opc, DstOps, SrcOps, Flags: Flag, B&: ProfBuilder);
292 MachineInstrBuilder MIB = getDominatingInstrForID(ID, NodeInsertPos&: InsertPos);
293 if (MIB) {
294 // Handle generating copies here.
295 return generateCopiesIfRequired(DstOps, MIB);
296 }
297 // This instruction does not exist in the CSEInfo. Build it and CSE it.
298 MachineInstrBuilder NewMIB =
299 MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flags: Flag);
300 return memoizeMI(MIB: NewMIB, NodeInsertPos: InsertPos);
301}
302
303MachineInstrBuilder CSEMIRBuilder::buildConstant(const DstOp &Res,
304 const ConstantInt &Val) {
305 constexpr unsigned Opc = TargetOpcode::G_CONSTANT;
306 if (!canPerformCSEForOpc(Opc))
307 return MachineIRBuilder::buildConstant(Res, Val);
308
309 // For vectors, CSE the element only for now.
310 LLT Ty = Res.getLLTTy(MRI: *getMRI());
311 if (Ty.isVector())
312 return buildSplatVector(Res, Src: buildConstant(Res: Ty.getElementType(), Val));
313
314 FoldingSetNodeID ID;
315 GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
316 void *InsertPos = nullptr;
317 profileMBBOpcode(B&: ProfBuilder, Opc);
318 profileDstOp(Op: Res, B&: ProfBuilder);
319 ProfBuilder.addNodeIDMachineOperand(MO: MachineOperand::CreateCImm(CI: &Val));
320 MachineInstrBuilder MIB = getDominatingInstrForID(ID, NodeInsertPos&: InsertPos);
321 if (MIB) {
322 // Handle generating copies here.
323 return generateCopiesIfRequired(DstOps: {Res}, MIB);
324 }
325
326 MachineInstrBuilder NewMIB = MachineIRBuilder::buildConstant(Res, Val);
327 return memoizeMI(MIB: NewMIB, NodeInsertPos: InsertPos);
328}
329
330MachineInstrBuilder CSEMIRBuilder::buildFConstant(const DstOp &Res,
331 const ConstantFP &Val) {
332 constexpr unsigned Opc = TargetOpcode::G_FCONSTANT;
333 if (!canPerformCSEForOpc(Opc))
334 return MachineIRBuilder::buildFConstant(Res, Val);
335
336 // For vectors, CSE the element only for now.
337 LLT Ty = Res.getLLTTy(MRI: *getMRI());
338 if (Ty.isVector())
339 return buildSplatVector(Res, Src: buildFConstant(Res: Ty.getElementType(), Val));
340
341 FoldingSetNodeID ID;
342 GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
343 void *InsertPos = nullptr;
344 profileMBBOpcode(B&: ProfBuilder, Opc);
345 profileDstOp(Op: Res, B&: ProfBuilder);
346 ProfBuilder.addNodeIDMachineOperand(MO: MachineOperand::CreateFPImm(CFP: &Val));
347 MachineInstrBuilder MIB = getDominatingInstrForID(ID, NodeInsertPos&: InsertPos);
348 if (MIB) {
349 // Handle generating copies here.
350 return generateCopiesIfRequired(DstOps: {Res}, MIB);
351 }
352 MachineInstrBuilder NewMIB = MachineIRBuilder::buildFConstant(Res, Val);
353 return memoizeMI(MIB: NewMIB, NodeInsertPos: InsertPos);
354}
355

source code of llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp