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//===------ CGGPUBuiltin.cpp - Codegen for GPU builtins -------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Generates code for built-in GPU calls which are not runtime-specific.
// (Runtime-specific codegen lives in programming model specific files.)
//
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
#include "clang/Basic/Builtins.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Instruction.h"
#include "llvm/Support/MathExtras.h"
using namespace clang;
using namespace CodeGen;
static llvm::Function *GetVprintfDeclaration(llvm::Module &M) {
llvm::Type *ArgTypes[] = {llvm::Type::getInt8PtrTy(M.getContext()),
llvm::Type::getInt8PtrTy(M.getContext())};
llvm::FunctionType *VprintfFuncType = llvm::FunctionType::get(
llvm::Type::getInt32Ty(M.getContext()), ArgTypes, false);
if (auto* F = M.getFunction("vprintf")) {
// Our CUDA system header declares vprintf with the right signature, so
// nobody else should have been able to declare vprintf with a bogus
// signature.
assert(F->getFunctionType() == VprintfFuncType);
return F;
}
// vprintf doesn't already exist; create a declaration and insert it into the
// module.
return llvm::Function::Create(
VprintfFuncType, llvm::GlobalVariable::ExternalLinkage, "vprintf", &M);
}
// Transforms a call to printf into a call to the NVPTX vprintf syscall (which
// isn't particularly special; it's invoked just like a regular function).
// vprintf takes two args: A format string, and a pointer to a buffer containing
// the varargs.
//
// For example, the call
//
// printf("format string", arg1, arg2, arg3);
//
// is converted into something resembling
//
// struct Tmp {
// Arg1 a1;
// Arg2 a2;
// Arg3 a3;
// };
// char* buf = alloca(sizeof(Tmp));
// *(Tmp*)buf = {a1, a2, a3};
// vprintf("format string", buf);
//
// buf is aligned to the max of {alignof(Arg1), ...}. Furthermore, each of the
// args is itself aligned to its preferred alignment.
//
// Note that by the time this function runs, E's args have already undergone the
// standard C vararg promotion (short -> int, float -> double, etc.).
RValue
CodeGenFunction::EmitNVPTXDevicePrintfCallExpr(const CallExpr *E,
ReturnValueSlot ReturnValue) {
assert(getTarget().getTriple().isNVPTX());
assert(E->getBuiltinCallee() == Builtin::BIprintf);
assert(E->getNumArgs() >= 1); // printf always has at least one arg.
const llvm::DataLayout &DL = CGM.getDataLayout();
llvm::LLVMContext &Ctx = CGM.getLLVMContext();
CallArgList Args;
EmitCallArgs(Args,
E->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
E->arguments(), E->getDirectCallee(),
/* ParamsToSkip = */ 0);
// We don't know how to emit non-scalar varargs.
if (std::any_of(Args.begin() + 1, Args.end(), [&](const CallArg &A) {
return !A.getRValue(*this).isScalar();
})) {
CGM.ErrorUnsupported(E, "non-scalar arg to printf");
return RValue::get(llvm::ConstantInt::get(IntTy, 0));
}
// Construct and fill the args buffer that we'll pass to vprintf.
llvm::Value *BufferPtr;
if (Args.size() <= 1) {
// If there are no args, pass a null pointer to vprintf.
BufferPtr = llvm::ConstantPointerNull::get(llvm::Type::getInt8PtrTy(Ctx));
} else {
llvm::SmallVector<llvm::Type *, 8> ArgTypes;
for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I)
ArgTypes.push_back(Args[I].getRValue(*this).getScalarVal()->getType());
// Using llvm::StructType is correct only because printf doesn't accept
// aggregates. If we had to handle aggregates here, we'd have to manually
// compute the offsets within the alloca -- we wouldn't be able to assume
// that the alignment of the llvm type was the same as the alignment of the
// clang type.
llvm::Type *AllocaTy = llvm::StructType::create(ArgTypes, "printf_args");
llvm::Value *Alloca = CreateTempAlloca(AllocaTy);
for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I) {
llvm::Value *P = Builder.CreateStructGEP(AllocaTy, Alloca, I - 1);
llvm::Value *Arg = Args[I].getRValue(*this).getScalarVal();
Builder.CreateAlignedStore(Arg, P, DL.getPrefTypeAlignment(Arg->getType()));
}
BufferPtr = Builder.CreatePointerCast(Alloca, llvm::Type::getInt8PtrTy(Ctx));
}
// Invoke vprintf and return.
llvm::Function* VprintfFunc = GetVprintfDeclaration(CGM.getModule());
return RValue::get(Builder.CreateCall(
VprintfFunc, {Args[0].getRValue(*this).getScalarVal(), BufferPtr}));
}
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