From 56366601765c1ff43f8796c271a818f8c272af27 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Sat, 19 May 2012 20:54:03 +0000 Subject: [PATCH] Fix an ancient bug in removeCopyByCommutingDef(). Before rewriting uses of one value in A to register B, check that there are no tied uses. That would require multiple A values to be rewritten. This bug can't bite in the current version of the code for a fairly subtle reason: A tied use would have caused 2-addr to insert a copy before the use. If the copy has been coalesced, it will be found by the same loop changed by this patch, and the optimization is aborted. This was exposed by 400.perlbench and lua after applying a patch that deletes joined copies aggressively. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157130 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/RegisterCoalescer.cpp | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp index dbd2cdd8d38..5e876df8662 100644 --- a/lib/CodeGen/RegisterCoalescer.cpp +++ b/lib/CodeGen/RegisterCoalescer.cpp @@ -687,9 +687,12 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP, MachineInstr *UseMI = &*UI; SlotIndex UseIdx = LIS->getInstructionIndex(UseMI); LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx); - if (ULR == IntA.end()) + if (ULR == IntA.end() || ULR->valno != AValNo) continue; - if (ULR->valno == AValNo && JoinedCopies.count(UseMI)) + if (JoinedCopies.count(UseMI)) + return false; + // If this use is tied to a def, we can't rewrite the register. + if (UseMI->isRegTiedToDefOperand(UI.getOperandNo())) return false; }