https://github.com/s-perron created https://github.com/llvm/llvm-project/pull/140292
Implements https://github.com/llvm/wg-hlsl/blob/main/proposals/0026-symbol-visibility.md. The change is to stop using the `hlsl.export` attribute. Instead, symbols with "program linkage" in HLSL will have export linkage with default visibility, and symbols with "external linkage" in HLSL will have export linkage with hidden visibility. >From 7738afa7780b0db19139eb25a71cd213d0f7fec6 Mon Sep 17 00:00:00 2001 From: Steven Perron <stevenper...@google.com> Date: Fri, 16 May 2025 14:21:01 -0400 Subject: [PATCH] [HLSL] Use hidden visibility for external linkage. Implements https://github.com/llvm/wg-hlsl/blob/main/proposals/0026-symbol-visibility.md. The change is to stop using the `hlsl.export` attribute. Instead, symbols with "program linkage" in HLSL will have export linkage with default visibility, and symbols with "external linkage" in HLSL will have export linkage with hidden visibility. --- clang/lib/CodeGen/CGHLSLRuntime.cpp | 8 -------- clang/lib/CodeGen/CGHLSLRuntime.h | 1 - clang/lib/CodeGen/CodeGenFunction.cpp | 1 - clang/lib/CodeGen/CodeGenModule.cpp | 5 +++++ llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp | 4 +++- llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp | 4 +++- llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp | 4 +++- llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp | 3 ++- 8 files changed, 16 insertions(+), 14 deletions(-) diff --git a/clang/lib/CodeGen/CGHLSLRuntime.cpp b/clang/lib/CodeGen/CGHLSLRuntime.cpp index a708b3aea129d..f441e4b3177c7 100644 --- a/clang/lib/CodeGen/CGHLSLRuntime.cpp +++ b/clang/lib/CodeGen/CGHLSLRuntime.cpp @@ -444,14 +444,6 @@ void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD, } } -void CGHLSLRuntime::setHLSLFunctionAttributes(const FunctionDecl *FD, - llvm::Function *Fn) { - if (FD->isInExportDeclContext()) { - const StringRef ExportAttrKindStr = "hlsl.export"; - Fn->addFnAttr(ExportAttrKindStr); - } -} - static void gatherFunctions(SmallVectorImpl<Function *> &Fns, llvm::Module &M, bool CtorOrDtor) { const auto *GV = diff --git a/clang/lib/CodeGen/CGHLSLRuntime.h b/clang/lib/CodeGen/CGHLSLRuntime.h index e40864d8ed854..621d6f66a76ca 100644 --- a/clang/lib/CodeGen/CGHLSLRuntime.h +++ b/clang/lib/CodeGen/CGHLSLRuntime.h @@ -151,7 +151,6 @@ class CGHLSLRuntime { void setHLSLEntryAttributes(const FunctionDecl *FD, llvm::Function *Fn); void emitEntryFunction(const FunctionDecl *FD, llvm::Function *Fn); - void setHLSLFunctionAttributes(const FunctionDecl *FD, llvm::Function *Fn); llvm::Instruction *getConvergenceToken(llvm::BasicBlock &BB); diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp index ac40aab97820d..601b521fc5cef 100644 --- a/clang/lib/CodeGen/CodeGenFunction.cpp +++ b/clang/lib/CodeGen/CodeGenFunction.cpp @@ -1274,7 +1274,6 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy, if (FD->hasAttr<HLSLShaderAttr>()) { CGM.getHLSLRuntime().emitEntryFunction(FD, Fn); } - CGM.getHLSLRuntime().setHLSLFunctionAttributes(FD, Fn); } EmitFunctionProlog(*CurFnInfo, CurFn, Args); diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 16e010adbeb5f..4d4cac4980108 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -1655,6 +1655,11 @@ void CodeGenModule::setGlobalVisibility(llvm::GlobalValue *GV, return; } + if (Context.getLangOpts().HLSL && !D->isInExportDeclContext()) { + GV->setVisibility(llvm::GlobalValue::HiddenVisibility); + return; + } + if (GV->hasDLLExportStorageClass() || GV->hasDLLImportStorageClass()) { // Reject incompatible dlllstorage and visibility annotations. if (!LV.isVisibilityExplicit()) diff --git a/llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp b/llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp index 035899205bf8c..94b2dbe78c4f7 100644 --- a/llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp +++ b/llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp @@ -24,7 +24,9 @@ static bool finalizeLinkage(Module &M) { for (Function &EF : M.functions()) { if (EF.isIntrinsic()) continue; - if (EF.hasFnAttribute("hlsl.shader") || EF.hasFnAttribute("hlsl.export")) + if (EF.hasExternalLinkage() && EF.hasDefaultVisibility()) + continue; + if (EF.hasFnAttribute("hlsl.shader")) continue; Funcs.push_back(&EF); } diff --git a/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp b/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp index 5991a9af6364d..dff6ae1f3de8d 100644 --- a/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp +++ b/llvm/lib/Target/SPIRV/SPIRVCallLowering.cpp @@ -444,7 +444,8 @@ bool SPIRVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder, .addUse(FuncVReg); addStringImm(F.getName(), MIB); } else if (F.getLinkage() != GlobalValue::InternalLinkage && - F.getLinkage() != GlobalValue::PrivateLinkage) { + F.getLinkage() != GlobalValue::PrivateLinkage && + F.getVisibility() != GlobalValue::HiddenVisibility) { SPIRV::LinkageType::LinkageType LnkTy = F.isDeclaration() ? SPIRV::LinkageType::Import @@ -453,6 +454,7 @@ bool SPIRVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder, SPIRV::Extension::SPV_KHR_linkonce_odr) ? SPIRV::LinkageType::LinkOnceODR : SPIRV::LinkageType::Export); + dbgs() << "(Call) Setting linkage attribute for " << F.getName() << "\n"; buildOpDecorate(FuncVReg, MIRBuilder, SPIRV::Decoration::LinkageAttributes, {static_cast<uint32_t>(LnkTy)}, F.getName()); } diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp index ac397fc486e19..efd1aa58667bc 100644 --- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp +++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp @@ -775,9 +775,11 @@ Register SPIRVGlobalRegistry::buildGlobalVariable( buildOpDecorate(Reg, MIRBuilder, SPIRV::Decoration::Alignment, {Alignment}); } - if (HasLinkageTy) + if (HasLinkageTy) { + dbgs() << "Setting linkage attribute for " << Name << "\n"; buildOpDecorate(Reg, MIRBuilder, SPIRV::Decoration::LinkageAttributes, {static_cast<uint32_t>(LinkageType)}, Name); + } SPIRV::BuiltIn::BuiltIn BuiltInId; if (getSpirvBuiltInIdByName(Name, BuiltInId)) diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp index 0db60c068bdff..bd6a3dd6a68b6 100644 --- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp +++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp @@ -3895,7 +3895,8 @@ bool SPIRVInstructionSelector::selectGlobalValue( if (hasInitializer(GlobalVar) && !Init) return true; - bool HasLnkTy = !GV->hasInternalLinkage() && !GV->hasPrivateLinkage(); + bool HasLnkTy = !GV->hasInternalLinkage() && !GV->hasPrivateLinkage() && + !GV->hasHiddenVisibility(); SPIRV::LinkageType::LinkageType LnkType = GV->isDeclarationForLinker() ? 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