From 8207641251706ea808df6d2a1ea8f87b8ee04c6d Mon Sep 17 00:00:00 2001 From: Ahmed Bougacha Date: Thu, 4 Jun 2015 20:39:23 +0000 Subject: [GlobalMerge] Take into account minsize on Global users' parents. Now that we can look at users, we can trivially do this: when we would have otherwise disabled GlobalMerge (currently -O<3), we can just run it for minsize functions, as it's usually a codesize win. Differential Revision: http://reviews.llvm.org/D10054 llvm-svn: 239087 --- llvm/lib/CodeGen/GlobalMerge.cpp | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'llvm/lib/CodeGen/GlobalMerge.cpp') diff --git a/llvm/lib/CodeGen/GlobalMerge.cpp b/llvm/lib/CodeGen/GlobalMerge.cpp index 79de17567f7..df54a9c6916 100644 --- a/llvm/lib/CodeGen/GlobalMerge.cpp +++ b/llvm/lib/CodeGen/GlobalMerge.cpp @@ -124,6 +124,12 @@ namespace { // for more information. unsigned MaxOffset; + /// Whether we should try to optimize for size only. + /// Currently, this applies a dead simple heuristic: only consider globals + /// used in minsize functions for merging. + /// FIXME: This could learn about optsize, and be used in the cost model. + bool OnlyOptimizeForSize; + bool doMerge(SmallVectorImpl &Globals, Module &M, bool isConst, unsigned AddrSpace) const; /// \brief Merge everything in \p Globals for which the corresponding bit @@ -152,9 +158,10 @@ namespace { public: static char ID; // Pass identification, replacement for typeid. explicit GlobalMerge(const TargetMachine *TM = nullptr, - unsigned MaximalOffset = 0) + unsigned MaximalOffset = 0, + bool OnlyOptimizeForSize = false) : FunctionPass(ID), TM(TM), DL(TM->getDataLayout()), - MaxOffset(MaximalOffset) { + MaxOffset(MaximalOffset), OnlyOptimizeForSize(OnlyOptimizeForSize) { initializeGlobalMergePass(*PassRegistry::getPassRegistry()); } @@ -290,6 +297,12 @@ bool GlobalMerge::doMerge(SmallVectorImpl &Globals, continue; Function *ParentFn = I->getParent()->getParent(); + + // If we're only optimizing for size, ignore non-minsize functions. + if (OnlyOptimizeForSize && + !ParentFn->hasFnAttribute(Attribute::MinSize)) + continue; + size_t UGSIdx = GlobalUsesByFunction[ParentFn]; // If this is the first global the basic block uses, map it to the set @@ -585,6 +598,7 @@ bool GlobalMerge::doFinalization(Module &M) { return false; } -Pass *llvm::createGlobalMergePass(const TargetMachine *TM, unsigned Offset) { - return new GlobalMerge(TM, Offset); +Pass *llvm::createGlobalMergePass(const TargetMachine *TM, unsigned Offset, + bool OnlyOptimizeForSize) { + return new GlobalMerge(TM, Offset, OnlyOptimizeForSize); } -- cgit v1.2.3