From 8f90724a5334cfe5d1039cab3d0b7ad9b59aef7f Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Mon, 18 Feb 2008 08:40:53 +0000 Subject: [PATCH] For now, avoid commuting def MI for copy MI's whose source is not killed. That simply trade a live interval for another and because only the non-two-address operands can be folded into loads, may end up pessimising code. llvm-svn: 47262 --- llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp index 17a89086bb6b..199c89ef55ae 100644 --- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp +++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp @@ -247,6 +247,13 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA, unsigned CopyIdx = li_->getDefIndex(li_->getInstructionIndex(CopyMI)); + // FIXME: For now, only eliminate the copy by commuting its def is the source + // does not live pass the move. Coalescing those copies may end up may simply + // end up swapping a live interval for another. That and because usually only + // the non-two address operand can be folded can end up pessimizing the code. + if (CopyMI->findRegisterUseOperandIdx(IntA.reg, true) != -1) + return false; + // BValNo is a value number in B that is defined by a copy from A. 'B3' in // the example above. LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);