CGGPUBuiltin.cpp revision 1.1.1.2 
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