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RegisterCoalescer: Don't rematerialize subregister definitions.

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We cannot simply rematerialize instructions which only defining a
subregister, as the final value also depends on the previous
instructions.

This fixes test/CodeGen/R600/subreg-coalescer-bug.ll with subreg
liveness enabled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229444 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun 2015-02-16 22:05:17 +00:00
parent 1f67650f77
commit 2a43652f3b
1 changed files with 18 additions and 0 deletions
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18
lib/CodeGen/RegisterCoalescer.cpp
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@ -815,6 +815,22 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
return true;
}
/// Returns true if @p MI defines the full vreg @p Reg, as opposed to just
/// defining a subregister.
static bool definesFullReg(const MachineInstr &MI, unsigned Reg) {
assert(!TargetRegisterInfo::isPhysicalRegister(Reg) &&
"This code cannot handle physreg aliasing");
for (const MachineOperand &Op : MI.operands()) {
if (!Op.isReg() || !Op.isDef() || Op.getReg() != Reg)
continue;
// Return true if we define the full register or don't care about the value
// inside other subregisters.
if (Op.getSubReg() == 0 || Op.isUndef())
return true;
}
return false;
}
bool RegisterCoalescer::reMaterializeTrivialDef(CoalescerPair &CP,
MachineInstr *CopyMI,
bool &IsDefCopy) {
@ -843,6 +859,8 @@ bool RegisterCoalescer::reMaterializeTrivialDef(CoalescerPair &CP,
return false;
if (!TII->isTriviallyReMaterializable(DefMI, AA))
return false;
if (!definesFullReg(*DefMI, SrcReg))
return false;
bool SawStore = false;
if (!DefMI->isSafeToMove(TII, AA, SawStore))
return false;