Revert "[OpenMP][libc] Remove special handling for OpenMP printf (llv…

…m#98940)"

This reverts commit 069e8bc.

Summary:
Some tests failing, revert this for now.

clang/lib/CodeGen/CGBuiltin.cpp

@@ -5986,6 +5986,8 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
         getTarget().getTriple().isAMDGCN() ||
         (getTarget().getTriple().isSPIRV() &&
          getTarget().getTriple().getVendor() == Triple::VendorType::AMD)) {
+      if (getLangOpts().OpenMPIsTargetDevice)
+        return EmitOpenMPDevicePrintfCallExpr(E);
       if (getTarget().getTriple().isNVPTX())
         return EmitNVPTXDevicePrintfCallExpr(E);
       if ((getTarget().getTriple().isAMDGCN() ||

clang/lib/CodeGen/CGGPUBuiltin.cpp

@@ -42,6 +42,28 @@ 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::PointerType::getUnqual(M.getContext()),
+                            llvm::PointerType::getUnqual(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
@@ -191,3 +213,10 @@ RValue 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

@@ -4536,6 +4536,7 @@ class CodeGenFunction : public CodeGenTypeCache {
 
   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);

libc/config/gpu/entrypoints.txt

@@ -226,6 +226,7 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # gpu/rpc.h entrypoints
     libc.src.gpu.rpc_host_call
+    libc.src.gpu.rpc_fprintf
 )
 
 set(TARGET_LIBM_ENTRYPOINTS

libc/spec/gpu_ext.td

@@ -10,6 +10,14 @@ def GPUExtensions : StandardSpec<"GPUExtensions"> {
             RetValSpec<VoidType>,
             [ArgSpec<VoidPtr>, ArgSpec<VoidPtr>, ArgSpec<SizeTType>]
         >,
+        FunctionSpec<
+            "rpc_fprintf",
+            RetValSpec<IntType>,
+            [ArgSpec<FILERestrictedPtr>,
+             ArgSpec<ConstCharRestrictedPtr>,
+             ArgSpec<VoidPtr>,
+             ArgSpec<SizeTType>]
+        >,
     ]
   >;
   let Headers = [

libc/src/gpu/CMakeLists.txt

@@ -8,3 +8,15 @@ add_entrypoint_object(
     libc.src.__support.RPC.rpc_client
     libc.src.__support.GPU.utils
 )
+
+add_entrypoint_object(
+  rpc_fprintf
+  SRCS
+    rpc_fprintf.cpp
+  HDRS
+    rpc_fprintf.h
+  DEPENDS
+    libc.src.stdio.gpu.gpu_file
+    libc.src.__support.RPC.rpc_client
+    libc.src.__support.GPU.utils
+)

libc/src/gpu/rpc_fprintf.cpp

@@ -0,0 +1,75 @@
+//===-- GPU implementation of fprintf -------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "rpc_fprintf.h"
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/GPU/utils.h"
+#include "src/__support/RPC/rpc_client.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/stdio/gpu/file.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+template <uint16_t opcode>
+int fprintf_impl(::FILE *__restrict file, const char *__restrict format,
+                 size_t format_size, void *args, size_t args_size) {
+  uint64_t mask = gpu::get_lane_mask();
+  rpc::Client::Port port = rpc::client.open<opcode>();
+
+  if constexpr (opcode == RPC_PRINTF_TO_STREAM) {
+    port.send([&](rpc::Buffer *buffer) {
+      buffer->data[0] = reinterpret_cast<uintptr_t>(file);
+    });
+  }
+
+  port.send_n(format, format_size);
+  port.recv([&](rpc::Buffer *buffer) {
+    args_size = static_cast<size_t>(buffer->data[0]);
+  });
+  port.send_n(args, args_size);
+
+  uint32_t ret = 0;
+  for (;;) {
+    const char *str = nullptr;
+    port.recv([&](rpc::Buffer *buffer) {
+      ret = static_cast<uint32_t>(buffer->data[0]);
+      str = reinterpret_cast<const char *>(buffer->data[1]);
+    });
+    // If any lanes have a string argument it needs to be copied back.
+    if (!gpu::ballot(mask, str))
+      break;
+
+    uint64_t size = str ? internal::string_length(str) + 1 : 0;
+    port.send_n(str, size);
+  }
+
+  port.close();
+  return ret;
+}
+
+// TODO: Delete this and port OpenMP to use `printf`.
+// place of varargs. Once varargs support is added we will use that to
+// implement the real version.
+LLVM_LIBC_FUNCTION(int, rpc_fprintf,
+                   (::FILE *__restrict stream, const char *__restrict format,
+                    void *args, size_t size)) {
+  cpp::string_view str(format);
+  if (stream == stdout)
+    return fprintf_impl<RPC_PRINTF_TO_STDOUT>(stream, format, str.size() + 1,
+                                              args, size);
+  else if (stream == stderr)
+    return fprintf_impl<RPC_PRINTF_TO_STDERR>(stream, format, str.size() + 1,
+                                              args, size);
+  else
+    return fprintf_impl<RPC_PRINTF_TO_STREAM>(stream, format, str.size() + 1,
+                                              args, size);
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/gpu/rpc_fprintf.h

@@ -0,0 +1,23 @@
+//===-- Implementation header for RPC functions -----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_GPU_RPC_HOST_CALL_H
+#define LLVM_LIBC_SRC_GPU_RPC_HOST_CALL_H
+
+#include "hdr/types/FILE.h"
+#include "src/__support/macros/config.h"
+#include <stddef.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+int rpc_fprintf(::FILE *__restrict stream, const char *__restrict format,
+                void *argc, size_t size);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_GPU_RPC_HOST_CALL_H

llvm/lib/Target/AMDGPU/AMDGPUPrintfRuntimeBinding.cpp

@@ -437,8 +437,7 @@ bool AMDGPUPrintfRuntimeBindingImpl::run(Module &M) {
     return false;
 
   auto PrintfFunction = M.getFunction("printf");
-  if (!PrintfFunction || !PrintfFunction->isDeclaration() ||
-      M.getModuleFlag("openmp"))
+  if (!PrintfFunction || !PrintfFunction->isDeclaration())
     return false;
 
   for (auto &U : PrintfFunction->uses()) {

offload/DeviceRTL/include/LibC.h

@@ -18,6 +18,7 @@ extern "C" {
 
 int memcmp(const void *lhs, const void *rhs, size_t count);
 void memset(void *dst, int C, size_t count);
+
 int printf(const char *format, ...);
 }
 

offload/DeviceRTL/src/LibC.cpp

@@ -11,33 +11,44 @@
 #pragma omp begin declare target device_type(nohost)
 
 namespace impl {
-int32_t omp_vprintf(const char *Format, __builtin_va_list vlist);
+int32_t omp_vprintf(const char *Format, void *Arguments, uint32_t);
 }
 
-#ifndef OMPTARGET_HAS_LIBC
-namespace impl {
 #pragma omp begin declare variant match(                                       \
         device = {arch(nvptx, nvptx64)},                                       \
             implementation = {extension(match_any)})
-extern "C" int vprintf(const char *format, ...);
-int omp_vprintf(const char *Format, __builtin_va_list vlist) {
-  return vprintf(Format, vlist);
+extern "C" int32_t vprintf(const char *, void *);
+namespace impl {
+int32_t omp_vprintf(const char *Format, void *Arguments, uint32_t) {
+  return vprintf(Format, Arguments);
 }
+} // namespace impl
 #pragma omp end declare variant
 
 #pragma omp begin declare variant match(device = {arch(amdgcn)})
-int omp_vprintf(const char *Format, __builtin_va_list) { return -1; }
-#pragma omp end declare variant
-} // namespace impl
 
-extern "C" int printf(const char *Format, ...) {
-  __builtin_va_list vlist;
-  __builtin_va_start(vlist, Format);
-  return impl::omp_vprintf(Format, vlist);
+#ifdef OMPTARGET_HAS_LIBC
+// TODO: Remove this handling once we have varargs support.
+extern "C" struct FILE *stdout;
+extern "C" int32_t rpc_fprintf(FILE *, const char *, void *, uint64_t);
+
+namespace impl {
+int32_t omp_vprintf(const char *Format, void *Arguments, uint32_t Size) {
+  return rpc_fprintf(stdout, Format, Arguments, Size);
 }
-#endif // OMPTARGET_HAS_LIBC
+} // namespace impl
+#else
+// We do not have a vprintf implementation for AMD GPU so we use a stub.
+namespace impl {
+int32_t omp_vprintf(const char *Format, void *Arguments, uint32_t) {
+  return -1;
+}
+} // namespace impl
+#endif
+#pragma omp end declare variant
 
 extern "C" {
+
 [[gnu::weak]] int memcmp(const void *lhs, const void *rhs, size_t count) {
   auto *L = reinterpret_cast<const unsigned char *>(lhs);
   auto *R = reinterpret_cast<const unsigned char *>(rhs);
@@ -54,6 +65,11 @@ extern "C" {
   for (size_t I = 0; I < count; ++I)
     dstc[I] = C;
 }
+
+/// printf() calls are rewritten by CGGPUBuiltin to __llvm_omp_vprintf
+int32_t __llvm_omp_vprintf(const char *Format, void *Arguments, uint32_t Size) {
+  return impl::omp_vprintf(Format, Arguments, Size);
+}
 }
 
 #pragma omp end declare target