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Now that we use an ilist of machine instructions, iterators are more robust

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than before.  Because this is the case, we can compute the first non-phi
instruction once when de-phi'ing a block.  This shaves ~4s off of
phielimination of _Z7yyparsev in kimwitu++ from 109s -> 105s.  There are
still much more important gains to come.

llvm-svn: 13452
This commit is contained in:
Chris Lattner 2004-05-10 18:47:18 +00:00
parent a407338e12
commit 8b57a31ff4
1 changed files with 8 additions and 5 deletions
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13
lib/CodeGen/PHIElimination.cpp
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@ -68,6 +68,13 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
const TargetInstrInfo &MII = MF.getTarget().getInstrInfo();
const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
// Get an iterator to the first instruction after the last PHI node (this may
// allso be the end of the basic block).
MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
while (AfterPHIsIt != MBB.end() &&
AfterPHIsIt->getOpcode() == TargetInstrInfo::PHI)
++AfterPHIsIt; // Skip over all of the PHI nodes...
while (MBB.front().getOpcode() == TargetInstrInfo::PHI) {
// Unlink the PHI node from the basic block... but don't delete the PHI yet
MachineInstr *MI = MBB.remove(MBB.begin());
@ -85,15 +92,11 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
// after any remaining phi nodes) which copies the new incoming register
// into the phi node destination.
//
MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
while (AfterPHIsIt != MBB.end() &&
AfterPHIsIt->getOpcode() == TargetInstrInfo::PHI)
++AfterPHIsIt; // Skip over all of the PHI nodes...
RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
// Update live variable information if there is any...
if (LV) {
MachineInstr *PHICopy = --AfterPHIsIt;
MachineInstr *PHICopy = prior(AfterPHIsIt);
// Add information to LiveVariables to know that the incoming value is
// killed. Note that because the value is defined in several places (once