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[InlineSpiller] Only account for real spills in the hoisting logic

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Spills of undef values shouldn't impact the placement of the relevant
spills. Drive by review.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304850 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Quentin Colombet 2017-06-07 00:22:07 +00:00
parent 756819c52a
commit e8e2b8ae7b
1 changed files with 6 additions and 3 deletions
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9
lib/CodeGen/InlineSpiller.cpp
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@ -877,14 +877,16 @@ void InlineSpiller::insertSpill(unsigned NewVReg, bool isKill,
MachineBasicBlock &MBB = *MI->getParent();
MachineInstrSpan MIS(MI);
if (isFullUndefDef(*MI))
bool IsRealSpill = true;
if (isFullUndefDef(*MI)) {
// Don't spill undef value.
// Anything works for undef, in particular keeping the memory
// uninitialized is a viable option and it saves code size and
// run time.
BuildMI(MBB, std::next(MI), MI->getDebugLoc(), TII.get(TargetOpcode::KILL))
.addReg(NewVReg, getKillRegState(isKill));
else
IsRealSpill = false;
} else
TII.storeRegToStackSlot(MBB, std::next(MI), NewVReg, isKill, StackSlot,
MRI.getRegClass(NewVReg), &TRI);
@ -893,7 +895,8 @@ void InlineSpiller::insertSpill(unsigned NewVReg, bool isKill,
DEBUG(dumpMachineInstrRangeWithSlotIndex(std::next(MI), MIS.end(), LIS,
"spill"));
++NumSpills;
HSpiller.addToMergeableSpills(*std::next(MI), StackSlot, Original);
if (IsRealSpill)
HSpiller.addToMergeableSpills(*std::next(MI), StackSlot, Original);
}
/// spillAroundUses - insert spill code around each use of Reg.