From 64649a7dc718206641b8b6bb436d4cdd3c836d04 Mon Sep 17 00:00:00 2001 From: Junmo Park Date: Fri, 4 Dec 2015 02:29:25 +0000 Subject: [PATCH] [BranchFolding] Merge MMOs during tail merge Summary: If we remove the MMOs from Load/Store instructions, they are treated as volatile. This makes other optimization passes unhappy. eg. Load/Store Optimization So, it looks better to merge, not remove. Reviewers: gberry, mcrosier Subscribers: gberry, llvm-commits Differential Revision: http://reviews.llvm.org/D14797 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254694 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/BranchFolding.cpp | 42 ++++++++++++++++++++++------------- 1 file changed, 26 insertions(+), 16 deletions(-) diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp index e41926a819c..3878281a4fe 100644 --- a/lib/CodeGen/BranchFolding.cpp +++ b/lib/CodeGen/BranchFolding.cpp @@ -744,24 +744,35 @@ bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, return true; } -static bool hasIdenticalMMOs(const MachineInstr *MI1, const MachineInstr *MI2) { +// Add MI1's MMOs to MI2's MMOs while excluding any duplicates. The MI scheduler +// currently doesn't handle multiple MMOs, so duplicates would likely pessimize +// the scheduler. +static void mergeMMOs(MachineInstr *MI1, MachineInstr *MI2) { auto I1 = MI1->memoperands_begin(), E1 = MI1->memoperands_end(); auto I2 = MI2->memoperands_begin(), E2 = MI2->memoperands_end(); - if ((E1 - I1) != (E2 - I2)) - return false; - for (; I1 != E1; ++I1, ++I2) { - if (**I1 != **I2) - return false; + MachineFunction *MF = MI1->getParent()->getParent(); + + // Mostly, MI1's MMO count is 1 or zero. So we don't have to use + // SmallSet. + for (; I1 != E1; ++I1) { + bool IsDupMMO = false; + for (I2 = MI2->memoperands_begin(); I2 != E2; ++I2) { + if (**I1 == **I2) { + IsDupMMO = true; + break; + } + } + if (IsDupMMO == false) { + MI2->addMemOperand(*MF, *I1); + E2 = MI2->memoperands_end(); + } } - return true; } static void -removeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos, - MachineBasicBlock &MBBCommon) { - // Remove MMOs from memory operations in the common block - // when they do not match the ones from the block being tail-merged. - // This ensures later passes conservatively compute dependencies. +mergeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos, + MachineBasicBlock &MBBCommon) { + // Merge MMOs from memory operations in the common block MachineBasicBlock *MBB = MBBIStartPos->getParent(); // Note CommonTailLen does not necessarily matches the size of // the common BB nor all its instructions because of debug @@ -792,8 +803,7 @@ removeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos, assert(MBBICommon->isIdenticalTo(&*MBBI) && "Expected matching MIIs!"); if (MBBICommon->mayLoad() || MBBICommon->mayStore()) - if (!hasIdenticalMMOs(&*MBBI, &*MBBICommon)) - MBBICommon->clearMemRefs(); + mergeMMOs(&*MBBI, &*MBBICommon); ++MBBI; ++MBBICommon; @@ -913,8 +923,8 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, continue; DEBUG(dbgs() << "BB#" << SameTails[i].getBlock()->getNumber() << (i == e-1 ? "" : ", ")); - // Remove MMOs from memory operations as needed. - removeMMOsFromMemoryOperations(SameTails[i].getTailStartPos(), *MBB); + // Merge MMOs from memory operations as needed. + mergeMMOsFromMemoryOperations(SameTails[i].getTailStartPos(), *MBB); // Hack the end off BB i, making it jump to BB commonTailIndex instead. ReplaceTailWithBranchTo(SameTails[i].getTailStartPos(), MBB); // BB i is no longer a predecessor of SuccBB; remove it from the worklist. -- 2.34.1