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It is always good to do a cross-class join when the large register has a tiny interval. 

Also avoid division by zero.

llvm-svn: 95917
This commit is contained in:
Jakob Stoklund Olesen 2010-02-11 20:58:45 +00:00
parent af88c0a84d
commit 28139f0043
1 changed files with 11 additions and 6 deletions
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17
llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
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@ -1148,12 +1148,14 @@ SimpleRegisterCoalescing::isWinToJoinCrossClass(unsigned LargeReg,
LiveInterval &SmallInt = li_->getInterval(SmallReg);
unsigned LargeSize = li_->getApproximateInstructionCount(LargeInt);
unsigned SmallSize = li_->getApproximateInstructionCount(SmallInt);
if (SmallSize > Threshold || LargeSize > Threshold)
if ((float)std::distance(mri_->use_nodbg_begin(SmallReg),
mri_->use_nodbg_end()) / SmallSize <
(float)std::distance(mri_->use_nodbg_begin(LargeReg),
mri_->use_nodbg_end()) / LargeSize)
if (LargeSize > Threshold) {
unsigned SmallUses = std::distance(mri_->use_nodbg_begin(SmallReg),
mri_->use_nodbg_end());
unsigned LargeUses = std::distance(mri_->use_nodbg_begin(LargeReg),
mri_->use_nodbg_end());
if (SmallUses*LargeSize < LargeUses*SmallSize)
return false;
}
return true;
}
@ -1561,7 +1563,10 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
(isExtSubReg || DstRC->isASubClass()) &&
!isWinToJoinCrossClass(LargeReg, SmallReg,
allocatableRCRegs_[NewRC].count())) {
DEBUG(dbgs() << "\tSrc/Dest are different register classes.\n");
DEBUG(dbgs() << "\tSrc/Dest are different register classes: "
<< SrcRC->getName() << "/"
<< DstRC->getName() << " -> "
<< NewRC->getName() << ".\n");
// Allow the coalescer to try again in case either side gets coalesced to
// a physical register that's compatible with the other side. e.g.
// r1024 = MOV32to32_ r1025