[OpenMP] Lower printf to __llvm_omp_vprintf

Extension of D112504. Lower amdgpu printf to `__llvm_omp_vprintf`
which takes the same const char*, void* arguments as cuda vprintf and also
passes the size of the void* alloca which will be needed by a non-stub
implementation of `__llvm_omp_vprintf` for amdgpu.

This removes the amdgpu link error on any printf in a target region in favour
of silently compiling code that doesn't print anything to stdout.

The exact set of changes to check-openmp probably needs revision before commit

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D112680

clang/lib/CodeGen/CGBuiltin.cpp

@@ -5106,11 +5106,16 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     return RValue::get(Builder.CreateFPExt(HalfVal, Builder.getFloatTy()));
   }
   case Builtin::BIprintf:
-    if (getTarget().getTriple().isNVPTX())
-      return EmitNVPTXDevicePrintfCallExpr(E, ReturnValue);
-    if (getTarget().getTriple().getArch() == Triple::amdgcn &&
-        getLangOpts().HIP)
-      return EmitAMDGPUDevicePrintfCallExpr(E, ReturnValue);
+    if (getTarget().getTriple().isNVPTX() ||
+        getTarget().getTriple().isAMDGCN()) {
+      if (getLangOpts().OpenMPIsDevice)
+        return EmitOpenMPDevicePrintfCallExpr(E);
+      if (getTarget().getTriple().isNVPTX())
+        return EmitNVPTXDevicePrintfCallExpr(E);
+      if (getTarget().getTriple().isAMDGCN() && getLangOpts().HIP)
+        return EmitAMDGPUDevicePrintfCallExpr(E);
+    }
+
     break;
   case Builtin::BI__builtin_canonicalize:
   case Builtin::BI__builtin_canonicalizef:

clang/lib/CodeGen/CGGPUBuiltin.cpp

@@ -21,13 +21,14 @@
 using namespace clang;
 using namespace CodeGen;
 
-static llvm::Function *GetVprintfDeclaration(llvm::Module &M) {
+namespace {
+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")) {
+  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.
@@ -41,6 +42,28 @@ static llvm::Function *GetVprintfDeclaration(llvm::Module &M) {
       VprintfFuncType, llvm::GlobalVariable::ExternalLinkage, "vprintf", &M);
 }
 
+llvm::Function *GetOpenMPVprintfDeclaration(CodeGenModule &CGM) {
+  const char *Name = "__llvm_omp_vprintf";
+  llvm::Module &M = CGM.getModule();
+  llvm::Type *ArgTypes[] = {llvm::Type::getInt8PtrTy(M.getContext()),
+                            llvm::Type::getInt8PtrTy(M.getContext()),
+                            llvm::Type::getInt32Ty(M.getContext())};
+  llvm::FunctionType *VprintfFuncType = llvm::FunctionType::get(
+      llvm::Type::getInt32Ty(M.getContext()), ArgTypes, false);
+
+  if (auto *F = M.getFunction(Name)) {
+    if (F->getFunctionType() != VprintfFuncType) {
+      CGM.Error(SourceLocation(),
+                "Invalid type declaration for __llvm_omp_vprintf");
+      return nullptr;
+    }
+    return F;
+  }
+
+  return llvm::Function::Create(
+      VprintfFuncType, llvm::GlobalVariable::ExternalLinkage, Name, &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
@@ -67,17 +90,17 @@ static llvm::Function *GetVprintfDeclaration(llvm::Module &M) {
 // Note that by the time this function runs, E's args have already undergone the
 // standard C vararg promotion (short -> int, float -> double, etc.).
 
-namespace {
-llvm::Value *packArgsIntoNVPTXFormatBuffer(CodeGenFunction *CGF,
-                                           const CallArgList &Args) {
+std::pair<llvm::Value *, llvm::TypeSize>
+packArgsIntoNVPTXFormatBuffer(CodeGenFunction *CGF, const CallArgList &Args) {
   const llvm::DataLayout &DL = CGF->CGM.getDataLayout();
   llvm::LLVMContext &Ctx = CGF->CGM.getLLVMContext();
   CGBuilderTy &Builder = CGF->Builder;
 
   // Construct and fill the args buffer that we'll pass to vprintf.
   if (Args.size() <= 1) {
-    // If there are no args, pass a null pointer to vprintf.
-    return llvm::ConstantPointerNull::get(llvm::Type::getInt8PtrTy(Ctx));
+    // If there are no args, pass a null pointer and size 0
+    llvm::Value * BufferPtr = llvm::ConstantPointerNull::get(llvm::Type::getInt8PtrTy(Ctx));
+    return {BufferPtr, llvm::TypeSize::Fixed(0)};
   } else {
     llvm::SmallVector<llvm::Type *, 8> ArgTypes;
     for (unsigned I = 1, NumArgs = Args.size(); I < NumArgs; ++I)
@@ -96,43 +119,64 @@ llvm::Value *packArgsIntoNVPTXFormatBuffer(CodeGenFunction *CGF,
       llvm::Value *Arg = Args[I].getRValue(*CGF).getScalarVal();
       Builder.CreateAlignedStore(Arg, P, DL.getPrefTypeAlign(Arg->getType()));
     }
-    return Builder.CreatePointerCast(Alloca, llvm::Type::getInt8PtrTy(Ctx));
+    llvm::Value *BufferPtr =
+        Builder.CreatePointerCast(Alloca, llvm::Type::getInt8PtrTy(Ctx));
+    return {BufferPtr, DL.getTypeAllocSize(AllocaTy)};
   }
 }
-} // namespace
 
-RValue
-CodeGenFunction::EmitNVPTXDevicePrintfCallExpr(const CallExpr *E,
-                                               ReturnValueSlot ReturnValue) {
-  assert(getTarget().getTriple().isNVPTX());
+bool containsNonScalarVarargs(CodeGenFunction *CGF, CallArgList Args) {
+  return llvm::any_of(llvm::drop_begin(Args), [&](const CallArg &A) {
+    return !A.getRValue(*CGF).isScalar();
+  });
+}
+
+RValue EmitDevicePrintfCallExpr(const CallExpr *E, CodeGenFunction *CGF,
+                                llvm::Function *Decl, bool WithSizeArg) {
+  CodeGenModule &CGM = CGF->CGM;
+  CGBuilderTy &Builder = CGF->Builder;
   assert(E->getBuiltinCallee() == Builtin::BIprintf);
   assert(E->getNumArgs() >= 1); // printf always has at least one arg.
 
+  // Uses the same format as nvptx for the argument packing, but also passes
+  // an i32 for the total size of the passed pointer
   CallArgList Args;
-  EmitCallArgs(Args,
-               E->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
-               E->arguments(), E->getDirectCallee(),
-               /* ParamsToSkip = */ 0);
+  CGF->EmitCallArgs(Args,
+                    E->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
+                    E->arguments(), E->getDirectCallee(),
+                    /* ParamsToSkip = */ 0);
 
   // We don't know how to emit non-scalar varargs.
-  if (llvm::any_of(llvm::drop_begin(Args), [&](const CallArg &A) {
-        return !A.getRValue(*this).isScalar();
-      })) {
+  if (containsNonScalarVarargs(CGF, Args)) {
     CGM.ErrorUnsupported(E, "non-scalar arg to printf");
-    return RValue::get(llvm::ConstantInt::get(IntTy, 0));
+    return RValue::get(llvm::ConstantInt::get(CGF->IntTy, 0));
   }
 
-  llvm::Value *BufferPtr = packArgsIntoNVPTXFormatBuffer(this, Args);
+  auto r = packArgsIntoNVPTXFormatBuffer(CGF, Args);
+  llvm::Value *BufferPtr = r.first;
+
+  llvm::SmallVector<llvm::Value *, 3> Vec = {
+      Args[0].getRValue(*CGF).getScalarVal(), BufferPtr};
+  if (WithSizeArg) {
+    // Passing > 32bit of data as a local alloca doesn't work for nvptx or
+    // amdgpu
+    llvm::Constant *Size =
+        llvm::ConstantInt::get(llvm::Type::getInt32Ty(CGM.getLLVMContext()),
+                               static_cast<uint32_t>(r.second.getFixedSize()));
 
-  // Invoke vprintf and return.
-  llvm::Function* VprintfFunc = GetVprintfDeclaration(CGM.getModule());
-  return RValue::get(Builder.CreateCall(
-      VprintfFunc, {Args[0].getRValue(*this).getScalarVal(), BufferPtr}));
+    Vec.push_back(Size);
+  }
+  return RValue::get(Builder.CreateCall(Decl, Vec));
 }
+} // namespace
 
-RValue
-CodeGenFunction::EmitAMDGPUDevicePrintfCallExpr(const CallExpr *E,
-                                                ReturnValueSlot ReturnValue) {
+RValue CodeGenFunction::EmitNVPTXDevicePrintfCallExpr(const CallExpr *E) {
+  assert(getTarget().getTriple().isNVPTX());
+  return EmitDevicePrintfCallExpr(
+      E, this, GetVprintfDeclaration(CGM.getModule()), false);
+}
+
+RValue CodeGenFunction::EmitAMDGPUDevicePrintfCallExpr(const CallExpr *E) {
   assert(getTarget().getTriple().getArch() == llvm::Triple::amdgcn);
   assert(E->getBuiltinCallee() == Builtin::BIprintf ||
          E->getBuiltinCallee() == Builtin::BI__builtin_printf);
@@ -162,3 +206,10 @@ CodeGenFunction::EmitAMDGPUDevicePrintfCallExpr(const CallExpr *E,
   Builder.SetInsertPoint(IRB.GetInsertBlock(), IRB.GetInsertPoint());
   return RValue::get(Printf);
 }
+
+RValue CodeGenFunction::EmitOpenMPDevicePrintfCallExpr(const CallExpr *E) {
+  assert(getTarget().getTriple().isNVPTX() ||
+         getTarget().getTriple().isAMDGCN());
+  return EmitDevicePrintfCallExpr(E, this, GetOpenMPVprintfDeclaration(CGM),
+                                  true);
+}

clang/lib/CodeGen/CodeGenFunction.h

@@ -4070,10 +4070,9 @@ class CodeGenFunction : public CodeGenTypeCache {
   RValue EmitCUDAKernelCallExpr(const CUDAKernelCallExpr *E,
                                 ReturnValueSlot ReturnValue);
 
-  RValue EmitNVPTXDevicePrintfCallExpr(const CallExpr *E,
-                                       ReturnValueSlot ReturnValue);
-  RValue EmitAMDGPUDevicePrintfCallExpr(const CallExpr *E,
-                                        ReturnValueSlot ReturnValue);
+  RValue EmitNVPTXDevicePrintfCallExpr(const CallExpr *E);
+  RValue EmitAMDGPUDevicePrintfCallExpr(const CallExpr *E);
+  RValue EmitOpenMPDevicePrintfCallExpr(const CallExpr *E);
 
   RValue EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                          const CallExpr *E, ReturnValueSlot ReturnValue);

openmp/libomptarget/DeviceRTL/include/Debug.h

@@ -34,23 +34,15 @@ void __assert_fail(const char *assertion, const char *file, unsigned line,
 ///}
 
 /// Print
-/// TODO: For now we have to use macros to guard the code because Clang lowers
-/// `printf` to different function calls on NVPTX and AMDGCN platforms, and it
-/// doesn't work for AMDGCN. After it can work on AMDGCN, we will remove the
-/// macro.
+/// printf() calls are rewritten by CGGPUBuiltin to __llvm_omp_vprintf
 /// {
 
-#ifndef __AMDGCN__
 extern "C" {
 int printf(const char *format, ...);
 }
 
-#define PRINTF(fmt, ...) (void)printf(fmt, __VA_ARGS__);
+#define PRINTF(fmt, ...) (void)printf(fmt, ##__VA_ARGS__);
 #define PRINT(str) PRINTF("%s", str)
-#else
-#define PRINTF(fmt, ...)
-#define PRINT(str)
-#endif
 
 ///}
 

openmp/libomptarget/DeviceRTL/src/Debug.cpp

@@ -29,6 +29,29 @@ void __assert_fail(const char *assertion, const char *file, unsigned line,
          assertion);
   __builtin_trap();
 }
+
+#pragma omp begin declare variant match(                                       \
+    device = {arch(nvptx, nvptx64)}, implementation = {extension(match_any)})
+int32_t vprintf(const char *, void *);
+namespace impl {
+static int32_t omp_vprintf(const char *Format, void *Arguments, uint32_t) {
+  return vprintf(Format, Arguments);
+}
+} // namespace impl
+#pragma omp end declare variant
+
+// We do not have a vprintf implementation for AMD GPU yet so we use a stub.
+#pragma omp begin declare variant match(device = {arch(amdgcn)})
+namespace impl {
+static int32_t omp_vprintf(const char *Format, void *Arguments, uint32_t) {
+  return -1;
+}
+} // namespace impl
+#pragma omp end declare variant
+
+int32_t __llvm_omp_vprintf(const char *Format, void *Arguments, uint32_t Size) {
+  return impl::omp_vprintf(Format, Arguments, Size);
+}
 }
 
 /// Current indentation level for the function trace. Only accessed by thread 0.

openmp/libomptarget/deviceRTLs/amdgcn/src/target_impl.hip

@@ -184,6 +184,11 @@ __attribute__((weak)) EXTERN void *__kmpc_impl_malloc(size_t) {
 }
 __attribute__((weak)) EXTERN void __kmpc_impl_free(void *) {}
 
+EXTERN
+int32_t __llvm_omp_vprintf(const char *Format, void *Arguments, uint32_t) {
+  return -1;
+}
+
 EXTERN void __kmpc_impl_unpack(uint64_t val, uint32_t &lo, uint32_t &hi) {
   lo = (uint32_t)(val & UINT64_C(0x00000000FFFFFFFF));
   hi = (uint32_t)((val & UINT64_C(0xFFFFFFFF00000000)) >> 32);

openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.cu

@@ -184,9 +184,15 @@ EXTERN int __kmpc_impl_test_lock(omp_lock_t *lock) {
 extern "C" {
 void *malloc(size_t);
 void free(void *);
+int32_t vprintf(const char *, void *);
 }
 
 EXTERN void *__kmpc_impl_malloc(size_t x) { return malloc(x); }
 EXTERN void __kmpc_impl_free(void *x) { free(x); }
 
+EXTERN int32_t __llvm_omp_vprintf(const char *Format, void *Arguments,
+                                  uint32_t) {
+  return vprintf(Format, Arguments);
+}
+
 #pragma omp end declare target

openmp/libomptarget/test/mapping/data_member_ref.cpp

@@ -1,6 +1,6 @@
 // RUN: %libomptarget-compilexx-run-and-check-generic
 
-// amdgcn does not have printf definition
+// Wrong results on amdgpu
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/mapping/declare_mapper_nested_default_mappers.cpp

@@ -1,6 +1,6 @@
 // RUN: %libomptarget-compilexx-run-and-check-generic
 
-// amdgcn does not have printf definition
+// Wrong results on amdgpu
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/mapping/declare_mapper_nested_mappers.cpp

@@ -1,6 +1,6 @@
 // RUN: %libomptarget-compilexx-run-and-check-generic
 
-// amdgcn does not have printf definition
+// Wrong results on amdgpu
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/mapping/lambda_by_value.cpp

@@ -1,6 +1,6 @@
 // RUN: %libomptarget-compilexx-run-and-check-generic
 
-// amdgcn does not have printf definition
+// Wrong results on amdgpu
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/mapping/ompx_hold/struct.c

@@ -1,7 +1,7 @@
 // RUN: %libomptarget-compile-generic -fopenmp-extensions
 // RUN: %libomptarget-run-generic | %fcheck-generic -strict-whitespace
 
-// amdgcn does not have printf definition
+// Wrong results on amdgpu
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/mapping/ptr_and_obj_motion.c

@@ -1,9 +1,5 @@
 // RUN: %libomptarget-compile-run-and-check-generic
 
-// amdgcn does not have printf definition
-// XFAIL: amdgcn-amd-amdhsa
-// XFAIL: amdgcn-amd-amdhsa-newRTL
-
 #include <stdio.h>
 
 typedef struct {

openmp/libomptarget/test/mapping/reduction_implicit_map.cpp

@@ -1,8 +1,8 @@
 // RUN: %libomptarget-compilexx-run-and-check-generic
 
-// amdgcn does not have printf definition
-// UNSUPPORTED: amdgcn-amd-amdhsa
-// UNSUPPORTED: amdgcn-amd-amdhsa-newRTL
+// Wrong results on amdgpu
+// XFAIL: amdgcn-amd-amdhsa
+// XFAIL: amdgcn-amd-amdhsa-newRTL
 
 #include <stdio.h>
 

openmp/libomptarget/test/offloading/bug49021.cpp

@@ -1,8 +1,7 @@
 // RUN: %libomptarget-compilexx-generic -O3 && %libomptarget-run-generic
 
-// Wrong results on amdgcn
-// UNSUPPORTED: amdgcn-amd-amdhsa
-// UNSUPPORTED: amdgcn-amd-amdhsa-newRTL
+// Wrong results on amdgpu
+// XFAIL: amdgcn-amd-amdhsa
 
 #include <iostream>
 

openmp/libomptarget/test/offloading/bug50022.cpp

@@ -1,8 +1,5 @@
 // RUN: %libomptarget-compilexx-and-run-generic
 
-// UNSUPPORTED: amdgcn-amd-amdhsa
-// UNSUPPORTED: amdgcn-amd-amdhsa-newRTL
-
 #include <cassert>
 #include <iostream>
 #include <stdexcept>

openmp/libomptarget/test/offloading/host_as_target.c

@@ -7,7 +7,7 @@
 
 // RUN: %libomptarget-compile-run-and-check-generic
 
-// amdgcn does not have printf definition
+// amdgpu does not have a working printf definition
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/unified_shared_memory/api.c

@@ -2,7 +2,7 @@
 // XFAIL: nvptx64-nvidia-cuda
 // XFAIL: nvptx64-nvidia-cuda-newRTL
 
-// Fails on amdgcn with error: GPU Memory Error
+// Fails on amdgpu with error: GPU Memory Error
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL
 

openmp/libomptarget/test/unified_shared_memory/close_enter_exit.c

@@ -3,7 +3,7 @@
 // REQUIRES: unified_shared_memory
 // UNSUPPORTED: clang-6, clang-7, clang-8, clang-9
 
-// Fails on amdgcn with error: GPU Memory Error
+// Fails on amdgpu with error: GPU Memory Error
 // XFAIL: amdgcn-amd-amdhsa
 // XFAIL: amdgcn-amd-amdhsa-newRTL