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Place new basic blocks immediately after their predecessor when splitting 

critical edges in PHIElimination.

This has a huge impact on regalloc performance, and we recover almost all of
the 10% compile time regression that edge splitting introduced.

llvm-svn: 89381
This commit is contained in:
Jakob Stoklund Olesen 2009-11-19 19:42:16 +00:00
parent 31c74dbb10
commit 331e6880a5
1 changed files with 7 additions and 7 deletions
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14
llvm/lib/CodeGen/PHIElimination.cpp
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@ -439,21 +439,21 @@ MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
++NumSplits;
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
MF->push_back(NMBB);
MF->insert(next(MachineFunction::iterator(A)), NMBB);
DEBUG(errs() << "PHIElimination splitting critical edge:"
" BB#" << A->getNumber()
<< " -- BB#" << NMBB->getNumber()
<< " -- BB#" << B->getNumber() << '\n');
A->ReplaceUsesOfBlockWith(B, NMBB);
// If A may fall through to B, we may have to insert a branch.
if (A->isLayoutSuccessor(B))
A->updateTerminator();
A->updateTerminator();
// Insert unconditional "jump B" instruction in NMBB.
// Insert unconditional "jump B" instruction in NMBB if necessary.
NMBB->addSuccessor(B);
Cond.clear();
MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond);
if (!NMBB->isLayoutSuccessor(B)) {
Cond.clear();
MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond);
}
// Fix PHI nodes in B so they refer to NMBB instead of A
for (MachineBasicBlock::iterator i = B->begin(), e = B->end();