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[RegisterCoalescer] Moving the RegisterCoalescer subtarget hook onto the TargetRegisterInfo instead of the TargetSubtargetInfo.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213188 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Bieneman
2014-07-16 20:13:31 +00:00
parent a1535e3b9b
commit ec7a144603
7 changed files with 80 additions and 75 deletions
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57
lib/Target/ARM/ARMSubtarget.cpp
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@@ -438,60 +438,3 @@ bool ARMSubtarget::useMovt(const MachineFunction &MF) const {
!MF.getFunction()->getAttributes().hasAttribute(
AttributeSet::FunctionIndex, Attribute::MinSize));
}
bool ARMSubtarget::shouldCoalesce(MachineInstr *MI,
const TargetRegisterClass *SrcRC,
unsigned SubReg,
const TargetRegisterClass *DstRC,
unsigned DstSubReg,
const TargetRegisterClass *NewRC) const {
auto MBB = MI->getParent();
auto MF = MBB->getParent();
const MachineRegisterInfo &MRI = MF->getRegInfo();
// If not copying into a sub-register this should be ok because we shouldn't
// need to split the reg.
if (!DstSubReg)
return true;
// Small registers don't frequently cause a problem, so we can coalesce them.
if (NewRC->getSize() < 32 && DstRC->getSize() < 32 && SrcRC->getSize() < 32)
return true;
auto NewRCWeight =
MRI.getTargetRegisterInfo()->getRegClassWeight(NewRC);
auto SrcRCWeight =
MRI.getTargetRegisterInfo()->getRegClassWeight(SrcRC);
auto DstRCWeight =
MRI.getTargetRegisterInfo()->getRegClassWeight(DstRC);
// If the source register class is more expensive than the destination, the
// coalescing is probably profitable.
if (SrcRCWeight.RegWeight > NewRCWeight.RegWeight)
return true;
if (DstRCWeight.RegWeight > NewRCWeight.RegWeight)
return true;
// If the register allocator isn't constrained, we can always allow coalescing
// unfortunately we don't know yet if we will be constrained.
// The goal of this heuristic is to restrict how many expensive registers
// we allow to coalesce in a given basic block.
auto AFI = MF->getInfo<ARMFunctionInfo>();
auto It = AFI->getCoalescedWeight(MBB);
DEBUG(dbgs() << "\tARM::shouldCoalesce - Coalesced Weight: "
<< It->second << "\n");
DEBUG(dbgs() << "\tARM::shouldCoalesce - Reg Weight: "
<< NewRCWeight.RegWeight << "\n");
// This number is the largest round number that which meets the criteria:
// (1) addresses PR18825
// (2) generates better code in some test cases (like vldm-shed-a9.ll)
// (3) Doesn't regress any test cases (in-tree, test-suite, and SPEC)
// In practice the SizeMultiplier will only factor in for straight line code
// that uses a lot of NEON vectors, which isn't terribly common.
unsigned SizeMultiplier = MBB->size()/100;
SizeMultiplier = SizeMultiplier ? SizeMultiplier : 1;
if (It->second < NewRCWeight.WeightLimit * SizeMultiplier) {
It->second += NewRCWeight.RegWeight;
return true;
}
return false;
}