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Constrain regclasses in PeepholeOptimizer.

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It can be necessary to restrict to a sub-class before accessing
sub-registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157164 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2012-05-20 18:42:55 +00:00
parent 0fda545c2c
commit 418a3638ac
1 changed files with 10 additions and 1 deletions
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11
lib/CodeGen/PeepholeOptimizer.cpp
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@ -150,6 +150,13 @@ optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
// No other uses.
return false;
// Ensure DstReg can get a register class that actually supports
// sub-registers. Don't change the class until we commit.
const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
DstRC = TM->getRegisterInfo()->getSubClassWithSubReg(DstRC, SubIdx);
if (!DstRC)
return false;
// The source has other uses. See if we can replace the other uses with use of
// the result of the extension.
SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs;
@ -247,8 +254,10 @@ optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
continue;
// About to add uses of DstReg, clear DstReg's kill flags.
if (!Changed)
if (!Changed) {
MRI->clearKillFlags(DstReg);
MRI->constrainRegClass(DstReg, DstRC);
}
unsigned NewVR = MRI->createVirtualRegister(RC);
BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),