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Change the heuristics used in the coalescer, register allocator, and within

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live intervals itself to use an instruction count approximation that is 
not affected by inserting empty indices.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53937 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2008-07-22 22:46:49 +00:00
parent 38bcec13e8
commit a1566f2e12
5 changed files with 29 additions and 14 deletions
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16
lib/CodeGen/SimpleRegisterCoalescing.cpp
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@ -851,8 +851,8 @@ SimpleRegisterCoalescing::isProfitableToCoalesceToSubRC(unsigned SrcReg,
// Then make sure the intervals are *short*.
LiveInterval &SrcInt = li_->getInterval(SrcReg);
LiveInterval &DstInt = li_->getInterval(DstReg);
unsigned SrcSize = SrcInt.getSize() / InstrSlots::NUM;
unsigned DstSize = DstInt.getSize() / InstrSlots::NUM;
unsigned SrcSize = li_->getApproximateInstructionCount(SrcInt);
unsigned DstSize = li_->getApproximateInstructionCount(DstInt);
const TargetRegisterClass *RC = mri_->getRegClass(DstReg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
return (SrcSize + DstSize) <= Threshold;
@ -1011,10 +1011,10 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
if (SubIdx) {
unsigned LargeReg = isExtSubReg ? SrcReg : DstReg;
unsigned SmallReg = isExtSubReg ? DstReg : SrcReg;
unsigned LargeRegSize =
li_->getInterval(LargeReg).getSize() / InstrSlots::NUM;
unsigned SmallRegSize =
li_->getInterval(SmallReg).getSize() / InstrSlots::NUM;
unsigned LargeRegSize =
li_->getApproximateInstructionCount(li_->getInterval(LargeReg));
unsigned SmallRegSize =
li_->getApproximateInstructionCount(li_->getInterval(SmallReg));
const TargetRegisterClass *RC = mri_->getRegClass(SmallReg);
unsigned Threshold = allocatableRCRegs_[RC].count();
// Be conservative. If both sides are virtual registers, do not coalesce
@ -1081,7 +1081,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
// If the virtual register live interval is long but it has low use desity,
// do not join them, instead mark the physical register as its allocation
// preference.
unsigned Length = JoinVInt.getSize() / InstrSlots::NUM;
unsigned Length = li_->getApproximateInstructionCount(JoinVInt);
if (Length > Threshold &&
(((float)std::distance(mri_->use_begin(JoinVReg),
mri_->use_end()) / Length) < (1.0 / Threshold))) {
@ -2196,7 +2196,7 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
// Divide the weight of the interval by its size. This encourages
// spilling of intervals that are large and have few uses, and
// discourages spilling of small intervals with many uses.
LI.weight /= LI.getSize();
LI.weight /= li_->getApproximateInstructionCount(LI);
}
}