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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89381 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index b3802ed..53ab8b0 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -439,21 +439,21 @@
++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();