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Change coalescer complexity from N^2 to N logN by changing one letter.

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Remove ugly hack that aborted the coalescer before using N^2 time.

This affects functions with very complicated live intervals for physical
registers, i.e. functions with thousands of function calls.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98776 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-03-17 23:21:58 +00:00
parent b675e255d0
commit 0427b2ac45
1 changed files with 1 additions and 12 deletions
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13
lib/CodeGen/SimpleRegisterCoalescing.cpp
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@ -1682,20 +1682,9 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
// density, do not join them, instead mark the physical register as its
// allocation preference.
LiveInterval &JoinVInt = SrcIsPhys ? DstInt : SrcInt;
LiveInterval &JoinPInt = SrcIsPhys ? SrcInt : DstInt;
unsigned JoinVReg = SrcIsPhys ? DstReg : SrcReg;
unsigned JoinPReg = SrcIsPhys ? SrcReg : DstReg;
// Don't join with physregs that have a ridiculous number of live
// ranges. The data structure performance is really bad when that
// happens.
if (JoinPInt.ranges.size() > 1000) {
mri_->setRegAllocationHint(JoinVInt.reg, 0, JoinPReg);
++numAborts;
DEBUG(dbgs() << "\tPhysical register too complicated, abort!\n");
return false;
}
const TargetRegisterClass *RC = mri_->getRegClass(JoinVReg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
unsigned Length = li_->getApproximateInstructionCount(JoinVInt);
@ -2170,7 +2159,7 @@ bool SimpleRegisterCoalescing::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS){
// Update the liveintervals of sub-registers.
if (TargetRegisterInfo::isPhysicalRegister(LHS.reg))
for (const unsigned *AS = tri_->getSubRegisters(LHS.reg); *AS; ++AS)
li_->getOrCreateInterval(*AS).MergeInClobberRanges(*li_, LHS,
li_->getOrCreateInterval(*AS).MergeInClobberRanges(*li_, RHS,
li_->getVNInfoAllocator());
return true;