Author: Joseph Huber Date: 2023-07-28T11:52:05-05:00 New Revision: 141c4e7a9403fed46d84c7f0429295bd28c89368
URL: https://github.com/llvm/llvm-project/commit/141c4e7a9403fed46d84c7f0429295bd28c89368 DIFF: https://github.com/llvm/llvm-project/commit/141c4e7a9403fed46d84c7f0429295bd28c89368.diff LOG: [OpenMP] Do not always emit unused extern variables Currently, the precense of the OpenMP target declare metadata requires that we always codegen a global declaration. This is undesirable in the case that we could defer or omit this declaration as is common with unused extern variables. This is important as it allows us, in the runtime, to rely on static linking semantics to omit unused symbols so they are not included when the user links it in. This patch changes the check for always emitting these variables. Because of this we also need to extend this logic to the generation of the offloading entries. This has the result of derring the offload entry generation to the canonical definitoin. So we are effectively assuming whoever owns the storage for this variable will perform that operation. This makes an exception for `link` attributes as those require their own special handling. Let me know if this is sound in the implementation, I do not have the largest view of the standards here. Fixes: https://github.com/llvm/llvm-project/issues/64133 Reviewed By: tianshilei1992 Differential Revision: https://reviews.llvm.org/D156368 Added: openmp/libomptarget/test/offloading/extern.c Modified: clang/lib/CodeGen/CGOpenMPRuntime.cpp clang/lib/CodeGen/CodeGenModule.cpp clang/test/OpenMP/declare_target_codegen.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp index a4f7eb96c0d9bc..02410c4d2b4250 100644 --- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp +++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp @@ -10166,6 +10166,13 @@ void CGOpenMPRuntime::registerTargetGlobalVariable(const VarDecl *VD, std::optional<OMPDeclareTargetDeclAttr::MapTypeTy> Res = OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(VD); + + // If this is an 'extern' declaration we defer to the canonical definition and + // do not emit an offloading entry. + if (Res && *Res != OMPDeclareTargetDeclAttr::MT_Link && + VD->hasExternalStorage()) + return; + if (!Res) { if (CGM.getLangOpts().OpenMPIsTargetDevice) { // Register non-target variables being emitted in device code (debug info diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 908dec42afabeb..332a879349cfc2 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -3605,6 +3605,13 @@ void CodeGenModule::EmitGlobal(GlobalDecl GD) { // Emit declaration of the must-be-emitted declare target variable. if (std::optional<OMPDeclareTargetDeclAttr::MapTypeTy> Res = OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(VD)) { + + // If this variable has external storage and doesn't require special + // link handling we defer to its canonical definition. + if (VD->hasExternalStorage() && + Res != OMPDeclareTargetDeclAttr::MT_Link) + return; + bool UnifiedMemoryEnabled = getOpenMPRuntime().hasRequiresUnifiedSharedMemory(); if ((*Res == OMPDeclareTargetDeclAttr::MT_To || diff --git a/clang/test/OpenMP/declare_target_codegen.cpp b/clang/test/OpenMP/declare_target_codegen.cpp index 14f5f5c096893a..71c742198af6bf 100644 --- a/clang/test/OpenMP/declare_target_codegen.cpp +++ b/clang/test/OpenMP/declare_target_codegen.cpp @@ -29,7 +29,6 @@ // CHECK-DAG: @flag = protected global i8 undef, // CHECK-DAG: @dx = {{protected | }}global i32 0, // CHECK-DAG: @dy = {{protected | }}global i32 0, -// CHECK-DAG: @aaa = external global i32, // CHECK-DAG: @bbb = {{protected | }}global i32 0, // CHECK-DAG: weak constant %struct.__tgt_offload_entry { ptr @bbb, // CHECK-DAG: @ccc = external global i32, @@ -80,7 +79,7 @@ extern int bbb; extern int aaa; int bbb = 0; extern int ccc; -int ddd = 0; +int ddd = ccc; #pragma omp end declare target #pragma omp declare target @@ -260,8 +259,6 @@ struct TTT { // CHECK-NOT: define {{.*}}{{baz1|baz4|maini1|Base|virtual_}} -// CHECK-DAG: !{i32 1, !"aaa", i32 0, i32 {{[0-9]+}}} -// CHECK-DAG: !{i32 1, !"ccc", i32 0, i32 {{[0-9]+}}} // CHECK-DAG: !{{{.+}}virtual_foo #ifdef OMP5 diff --git a/openmp/libomptarget/test/offloading/extern.c b/openmp/libomptarget/test/offloading/extern.c new file mode 100644 index 00000000000000..35cf905ee0cd41 --- /dev/null +++ b/openmp/libomptarget/test/offloading/extern.c @@ -0,0 +1,27 @@ +// RUN: %libomptarget-compile-generic -DVAR -c -o %t.o +// RUN: %libomptarget-compile-generic %t.o && %libomptarget-run-generic | %fcheck-generic + +#ifdef VAR +int x = 1; +#else +#include <stdio.h> +#include <assert.h> +extern int x; + +int main() { + int value = 0; +#pragma omp target map(from : value) + value = x; + assert(value == 1); + + x = 999; +#pragma omp target update to(x) + +#pragma omp target map(from : value) + value = x; + assert(value == 999); + + // CHECK: PASS + printf ("PASS\n"); +} +#endif _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits