From 19a8adc9bd2785698c1d5429503fd406d95b6c53 Mon Sep 17 00:00:00 2001 From: Erich Keane Date: Thu, 25 Oct 2018 18:57:19 +0000 Subject: Implement Function Multiversioning for Non-ELF Systems. Similar to how ICC handles CPU-Dispatch on Windows, this patch uses the resolver function directly to forward the call to the proper function. This is not nearly as efficient as IFuncs of course, but is still quite useful for large functions specifically developed for certain processors. This is unfortunately still limited to x86, since it depends on __builtin_cpu_supports and __builtin_cpu_is, which are x86 builtins. The naming for the resolver/forwarding function for cpu-dispatch was taken from ICC's implementation, which uses the unmodified name for this (no mangling additions). This is possible, since cpu-dispatch uses '.A' for the 'default' version. In 'target' multiversioning, this function keeps the '.resolver' extension in order to keep the default function keeping the default mangling. Change-Id: I4731555a39be26c7ad59a2d8fda6fa1a50f73284 Differential Revision: https://reviews.llvm.org/D53586 llvm-svn: 345298 --- clang/lib/CodeGen/CodeGenFunction.cpp | 34 +++++++++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-) (limited to 'clang/lib/CodeGen/CodeGenFunction.cpp') diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp index 700723189ed..84d7b9e6111 100644 --- a/clang/lib/CodeGen/CodeGenFunction.cpp +++ b/clang/lib/CodeGen/CodeGenFunction.cpp @@ -2392,6 +2392,29 @@ CodeGenFunction::FormResolverCondition(const MultiVersionResolverOption &RO) { return Condition; } +static void CreateMultiVersionResolverReturn(CodeGenModule &CGM, + llvm::Function *Resolver, + CGBuilderTy &Builder, + llvm::Function *FuncToReturn, + bool SupportsIFunc) { + if (SupportsIFunc) { + Builder.CreateRet(FuncToReturn); + return; + } + + llvm::SmallVector Args; + llvm::for_each(Resolver->args(), + [&](llvm::Argument &Arg) { Args.push_back(&Arg); }); + + llvm::CallInst *Result = Builder.CreateCall(FuncToReturn, Args); + Result->setTailCallKind(llvm::CallInst::TCK_MustTail); + + if (Resolver->getReturnType()->isVoidTy()) + Builder.CreateRetVoid(); + else + Builder.CreateRet(Result); +} + void CodeGenFunction::EmitMultiVersionResolver( llvm::Function *Resolver, ArrayRef Options) { assert((getContext().getTargetInfo().getTriple().getArch() == @@ -2399,6 +2422,9 @@ void CodeGenFunction::EmitMultiVersionResolver( getContext().getTargetInfo().getTriple().getArch() == llvm::Triple::x86_64) && "Only implemented for x86 targets"); + + bool SupportsIFunc = getContext().getTargetInfo().supportsIFunc(); + // Main function's basic block. llvm::BasicBlock *CurBlock = createBasicBlock("resolver_entry", Resolver); Builder.SetInsertPoint(CurBlock); @@ -2412,13 +2438,15 @@ void CodeGenFunction::EmitMultiVersionResolver( if (!Condition) { assert(&RO == Options.end() - 1 && "Default or Generic case must be last"); - Builder.CreateRet(RO.Function); + CreateMultiVersionResolverReturn(CGM, Resolver, Builder, RO.Function, + SupportsIFunc); return; } llvm::BasicBlock *RetBlock = createBasicBlock("resolver_return", Resolver); - llvm::IRBuilder<> RetBuilder(RetBlock); - RetBuilder.CreateRet(RO.Function); + CGBuilderTy RetBuilder(*this, RetBlock); + CreateMultiVersionResolverReturn(CGM, Resolver, RetBuilder, RO.Function, + SupportsIFunc); CurBlock = createBasicBlock("resolver_else", Resolver); Builder.CreateCondBr(Condition, RetBlock, CurBlock); } -- cgit v1.2.3