Author: evancheng
Date: Mon Feb 18 02:40:53 2008
New Revision: 47262
URL: http://llvm.org/viewvc/llvm-project?rev=47262&view=rev
Log:
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.
Modified:
llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp
Modified: llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp?rev=47262&r1=47261&r2=47262&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp (original)
+++ llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp Mon Feb 18 02:40:53 2008
@@ -247,6 +247,13 @@
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);
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