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Fix a bug in the local spiller, where we could take code like this:

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store r12 -> [ss#2]
  R3 = load [ss#1]
  use R3
  R3 = load [ss#2]
  R4 = load [ss#1]

and turn it into this code:

  store R12 -> [ss#2]
  R3 = load [ss#1]
  use R3
  R3 = R12
  R4 = R3    <- oops!

The problem was that promoting R3 = load[ss#2] to a copy missed the fact that
the instruction invalidated R3 at that point.

llvm-svn: 23638
This commit is contained in:
Chris Lattner 2005-10-05 18:30:19 +00:00
parent e4feaa3bea
commit 5afc88fe07
1 changed files with 5 additions and 5 deletions
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10
lib/CodeGen/VirtRegMap.cpp
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@ -490,11 +490,11 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) {
if (DestReg != It->second) {
MRI->copyRegToReg(MBB, &MI, DestReg, It->second,
MF.getSSARegMap()->getRegClass(VirtReg));
// Revisit the copy if the destination is a vreg.
if (MRegisterInfo::isVirtualRegister(DestReg)) {
NextMII = &MI;
--NextMII; // backtrack to the copy.
}
// Revisit the copy so we make sure to notice the effects of the
// operation on the destreg (either needing to RA it if it's
// virtual or needing to clobber any values if it's physical).
NextMII = &MI;
--NextMII; // backtrack to the copy.
}
MBB.erase(&MI);
goto ProcessNextInst;