[llvm-commits] [llvm] r47281 - /llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp

[Evan Cheng]

Author: evancheng
Date: Mon Feb 18 12:56:31 2008
New Revision: 47281

URL: http://llvm.org/viewvc/llvm-project?rev=47281&view=rev
Log:
- Remove the previous check which broke coalescer-commute3.ll
- For now, conservatively ignore copy MI whose source is a physical register. Commuting its def MI can cause a physical register live interval to be live through a loop (since we know it's live coming into the def MI).

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=47281&r1=47280&r2=47281&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp (original)
+++ llvm/trunk/lib/CodeGen/SimpleRegisterCoalescing.cpp Mon Feb 18 12:56:31 2008
@@ -247,11 +247,11 @@
 
   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)
+  // FIXME: For now, only eliminate the copy by commuting its def when the
+  // source register is a virtual register. We want to guard against cases
+  // where the copy is a back edge copy and commuting the def lengthen the
+  // live interval of the source register to the entire loop.
+  if (TargetRegisterInfo::isPhysicalRegister(IntA.reg))
     return false;
 
   // BValNo is a value number in B that is defined by a copy from A. 'B3' in