1//===------ CGGPUBuiltin.cpp - Codegen for GPU builtins -------------------===//
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// Generates code for built-in GPU calls which are not runtime-specific.
10// (Runtime-specific codegen lives in programming model specific files.)
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "clang/Basic/Builtins.h"
16#include "llvm/IR/DataLayout.h"
17#include "llvm/IR/Instruction.h"
18#include "llvm/Support/MathExtras.h"
19#include "llvm/Transforms/Utils/AMDGPUEmitPrintf.h"
20
21using namespace clang;
22using namespace CodeGen;
23
24static llvm::Function *GetVprintfDeclaration(llvm::Module &M) {
25 llvm::Type *ArgTypes[] = {llvm::Type::getInt8PtrTy(M.getContext()),
26 llvm::Type::getInt8PtrTy(M.getContext())};
27 llvm::FunctionType *VprintfFuncType = llvm::FunctionType::get(
28 llvm::Type::getInt32Ty(M.getContext()), ArgTypes, false);
29
30 if (auto* F = M.getFunction("vprintf")) {
31 // Our CUDA system header declares vprintf with the right signature, so
32 // nobody else should have been able to declare vprintf with a bogus
33 // signature.
34 assert(F->getFunctionType() == VprintfFuncType);
35 return F;
36 }
37
38 // vprintf doesn't already exist; create a declaration and insert it into the
39 // module.
40 return llvm::Function::Create(
41 VprintfFuncType, llvm::GlobalVariable::ExternalLinkage, "vprintf", &M);
42}
43
44// Transforms a call to printf into a call to the NVPTX vprintf syscall (which
45// isn't particularly special; it's invoked just like a regular function).
46// vprintf takes two args: A format string, and a pointer to a buffer containing
47// the varargs.
48//
49// For example, the call
50//
51// printf("format string", arg1, arg2, arg3);
52//
53// is converted into something resembling
54//
55// struct Tmp {
56// Arg1 a1;
57// Arg2 a2;
58// Arg3 a3;
59// };
60// char* buf = alloca(sizeof(Tmp));
61// *(Tmp*)buf = {a1, a2, a3};
62// vprintf("format string", buf);
63//
64// buf is aligned to the max of {alignof(Arg1), ...}. Furthermore, each of the
65// args is itself aligned to its preferred alignment.
66//
67// Note that by the time this function runs, E's args have already undergone the
68// standard C vararg promotion (short -> int, float -> double, etc.).
69RValue
70CodeGenFunction::EmitNVPTXDevicePrintfCallExpr(const CallExpr *E,
71 ReturnValueSlot ReturnValue) {
72 assert(getTarget().getTriple().isNVPTX());
73 assert(E->getBuiltinCallee() == Builtin::BIprintf);
74 assert(E->getNumArgs() >= 1); // printf always has at least one arg.
75
76 const llvm::DataLayout &DL = CGM.getDataLayout();
77 llvm::LLVMContext &Ctx = CGM.getLLVMContext();
78
79 CallArgList Args;
80 EmitCallArgs(Args,
81 E->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
82 E->arguments(), E->getDirectCallee(),
83 /* ParamsToSkip = */ 0);
84
85 // We don't know how to emit non-scalar varargs.
86 if (std::any_of(Args.begin() + 1, Args.end(), [&](const CallArg &A) {
87 return !A.getRValue(*this).isScalar();
88 })) {
89 CGM.ErrorUnsupported(E, "non-scalar arg to printf");
90 return RValue::get(llvm::ConstantInt::get(IntTy, 0));
91 }
92
93 // Construct and fill the args buffer that we'll pass to vprintf.
94 llvm::Value *BufferPtr;
95 if (Args.size() <= 1) {
96 // If there are no args, pass a null pointer to vprintf.
97 BufferPtr = llvm::ConstantPointerNull::get(llvm::Type::getInt8PtrTy(Ctx));
98 } else {
99 llvm::SmallVector<llvm::Type *, 8> ArgTypes;
100 for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I)
101 ArgTypes.push_back(Args[I].getRValue(*this).getScalarVal()->getType());
102
103 // Using llvm::StructType is correct only because printf doesn't accept
104 // aggregates. If we had to handle aggregates here, we'd have to manually
105 // compute the offsets within the alloca -- we wouldn't be able to assume
106 // that the alignment of the llvm type was the same as the alignment of the
107 // clang type.
108 llvm::Type *AllocaTy = llvm::StructType::create(ArgTypes, "printf_args");
109 llvm::Value *Alloca = CreateTempAlloca(AllocaTy);
110
111 for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I) {
112 llvm::Value *P = Builder.CreateStructGEP(AllocaTy, Alloca, I - 1);
113 llvm::Value *Arg = Args[I].getRValue(*this).getScalarVal();
114 Builder.CreateAlignedStore(Arg, P, DL.getPrefTypeAlign(Arg->getType()));
115 }
116 BufferPtr = Builder.CreatePointerCast(Alloca, llvm::Type::getInt8PtrTy(Ctx));
117 }
118
119 // Invoke vprintf and return.
120 llvm::Function* VprintfFunc = GetVprintfDeclaration(CGM.getModule());
121 return RValue::get(Builder.CreateCall(
122 VprintfFunc, {Args[0].getRValue(*this).getScalarVal(), BufferPtr}));
123}
124
125RValue
126CodeGenFunction::EmitAMDGPUDevicePrintfCallExpr(const CallExpr *E,
127 ReturnValueSlot ReturnValue) {
128 assert(getTarget().getTriple().getArch() == llvm::Triple::amdgcn);
129 assert(E->getBuiltinCallee() == Builtin::BIprintf ||
130 E->getBuiltinCallee() == Builtin::BI__builtin_printf);
131 assert(E->getNumArgs() >= 1); // printf always has at least one arg.
132
133 CallArgList CallArgs;
134 EmitCallArgs(CallArgs,
135 E->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
136 E->arguments(), E->getDirectCallee(),
137 /* ParamsToSkip = */ 0);
138
139 SmallVector<llvm::Value *, 8> Args;
140 for (auto A : CallArgs) {
141 // We don't know how to emit non-scalar varargs.
142 if (!A.getRValue(*this).isScalar()) {
143 CGM.ErrorUnsupported(E, "non-scalar arg to printf");
144 return RValue::get(llvm::ConstantInt::get(IntTy, -1));
145 }
146
147 llvm::Value *Arg = A.getRValue(*this).getScalarVal();
148 Args.push_back(Arg);
149 }
150
151 llvm::IRBuilder<> IRB(Builder.GetInsertBlock(), Builder.GetInsertPoint());
152 IRB.SetCurrentDebugLocation(Builder.getCurrentDebugLocation());
153 auto Printf = llvm::emitAMDGPUPrintfCall(IRB, Args);
154 Builder.SetInsertPoint(IRB.GetInsertBlock(), IRB.GetInsertPoint());
155 return RValue::get(Printf);
156}
157