xref: /freebsd/contrib/llvm-project/clang/lib/CodeGen/CGGPUBuiltin.cpp (revision 6966ac055c3b7a39266fb982493330df7a097997)
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 
20 using namespace clang;
21 using namespace CodeGen;
22 
23 static llvm::Function *GetVprintfDeclaration(llvm::Module &M) {
24   llvm::Type *ArgTypes[] = {llvm::Type::getInt8PtrTy(M.getContext()),
25                             llvm::Type::getInt8PtrTy(M.getContext())};
26   llvm::FunctionType *VprintfFuncType = llvm::FunctionType::get(
27       llvm::Type::getInt32Ty(M.getContext()), ArgTypes, false);
28 
29   if (auto* F = M.getFunction("vprintf")) {
30     // Our CUDA system header declares vprintf with the right signature, so
31     // nobody else should have been able to declare vprintf with a bogus
32     // signature.
33     assert(F->getFunctionType() == VprintfFuncType);
34     return F;
35   }
36 
37   // vprintf doesn't already exist; create a declaration and insert it into the
38   // module.
39   return llvm::Function::Create(
40       VprintfFuncType, llvm::GlobalVariable::ExternalLinkage, "vprintf", &M);
41 }
42 
43 // Transforms a call to printf into a call to the NVPTX vprintf syscall (which
44 // isn't particularly special; it's invoked just like a regular function).
45 // vprintf takes two args: A format string, and a pointer to a buffer containing
46 // the varargs.
47 //
48 // For example, the call
49 //
50 //   printf("format string", arg1, arg2, arg3);
51 //
52 // is converted into something resembling
53 //
54 //   struct Tmp {
55 //     Arg1 a1;
56 //     Arg2 a2;
57 //     Arg3 a3;
58 //   };
59 //   char* buf = alloca(sizeof(Tmp));
60 //   *(Tmp*)buf = {a1, a2, a3};
61 //   vprintf("format string", buf);
62 //
63 // buf is aligned to the max of {alignof(Arg1), ...}.  Furthermore, each of the
64 // args is itself aligned to its preferred alignment.
65 //
66 // Note that by the time this function runs, E's args have already undergone the
67 // standard C vararg promotion (short -> int, float -> double, etc.).
68 RValue
69 CodeGenFunction::EmitNVPTXDevicePrintfCallExpr(const CallExpr *E,
70                                                ReturnValueSlot ReturnValue) {
71   assert(getTarget().getTriple().isNVPTX());
72   assert(E->getBuiltinCallee() == Builtin::BIprintf);
73   assert(E->getNumArgs() >= 1); // printf always has at least one arg.
74 
75   const llvm::DataLayout &DL = CGM.getDataLayout();
76   llvm::LLVMContext &Ctx = CGM.getLLVMContext();
77 
78   CallArgList Args;
79   EmitCallArgs(Args,
80                E->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
81                E->arguments(), E->getDirectCallee(),
82                /* ParamsToSkip = */ 0);
83 
84   // We don't know how to emit non-scalar varargs.
85   if (std::any_of(Args.begin() + 1, Args.end(), [&](const CallArg &A) {
86         return !A.getRValue(*this).isScalar();
87       })) {
88     CGM.ErrorUnsupported(E, "non-scalar arg to printf");
89     return RValue::get(llvm::ConstantInt::get(IntTy, 0));
90   }
91 
92   // Construct and fill the args buffer that we'll pass to vprintf.
93   llvm::Value *BufferPtr;
94   if (Args.size() <= 1) {
95     // If there are no args, pass a null pointer to vprintf.
96     BufferPtr = llvm::ConstantPointerNull::get(llvm::Type::getInt8PtrTy(Ctx));
97   } else {
98     llvm::SmallVector<llvm::Type *, 8> ArgTypes;
99     for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I)
100       ArgTypes.push_back(Args[I].getRValue(*this).getScalarVal()->getType());
101 
102     // Using llvm::StructType is correct only because printf doesn't accept
103     // aggregates.  If we had to handle aggregates here, we'd have to manually
104     // compute the offsets within the alloca -- we wouldn't be able to assume
105     // that the alignment of the llvm type was the same as the alignment of the
106     // clang type.
107     llvm::Type *AllocaTy = llvm::StructType::create(ArgTypes, "printf_args");
108     llvm::Value *Alloca = CreateTempAlloca(AllocaTy);
109 
110     for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I) {
111       llvm::Value *P = Builder.CreateStructGEP(AllocaTy, Alloca, I - 1);
112       llvm::Value *Arg = Args[I].getRValue(*this).getScalarVal();
113       Builder.CreateAlignedStore(Arg, P, DL.getPrefTypeAlignment(Arg->getType()));
114     }
115     BufferPtr = Builder.CreatePointerCast(Alloca, llvm::Type::getInt8PtrTy(Ctx));
116   }
117 
118   // Invoke vprintf and return.
119   llvm::Function* VprintfFunc = GetVprintfDeclaration(CGM.getModule());
120   return RValue::get(Builder.CreateCall(
121       VprintfFunc, {Args[0].getRValue(*this).getScalarVal(), BufferPtr}));
122 }
123