[llvm-commits] [llvm] r139781 - /llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Wed Sep 14 23:52:06 2011
New Revision: 139781

URL: http://llvm.org/viewvc/llvm-project?rev=139781&view=rev
Log:
It is safe to remat a value killed by phis.

The source live range is recomputed using shrinkToUses() which does
handle phis correctly.  The hasPHIKill() condition was relevant in the
old days when ReMaterializeTrivialDef() tried to recompute the live
range itself.

The shrinkToUses() function will mark the original def as dead when no
more uses and phi kills remain.  It is then removed by
runOnMachineFunction().

Modified:
    llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp

Modified: llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp?rev=139781&r1=139780&r2=139781&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp Wed Sep 14 23:52:06 2011
@@ -805,9 +805,7 @@
   LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
   assert(SrcLR != SrcInt.end() && "Live range not found!");
   VNInfo *ValNo = SrcLR->valno;
-  // If other defs can reach uses of this def, then it's not safe to perform
-  // the optimization.
-  if (ValNo->isPHIDef() || ValNo->isUnused() || ValNo->hasPHIKill())
+  if (ValNo->isPHIDef() || ValNo->isUnused())
     return false;
   MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
   if (!DefMI)