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refactor the speculative execution logic to be factored into the cond branch code instead of

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doing a cfg search for every block simplified.

llvm-svn: 121686
This commit is contained in:
Chris Lattner 2010-12-13 05:26:52 +00:00
parent 4b9e3a31b0
commit 1eb2e235c8
1 changed files with 22 additions and 26 deletions
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48
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -2150,10 +2150,28 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
// from BI. We know that the condbr dominates the two blocks, so see if
// there is any identical code in the "then" and "else" blocks. If so, we
// can hoist it up to the branching block.
if (BI->getSuccessor(0)->getSinglePredecessor() != 0 &&
BI->getSuccessor(1)->getSinglePredecessor() != 0)
if (HoistThenElseCodeToIf(BI))
return SimplifyCFG(BB) | true;
if (BI->getSuccessor(0)->getSinglePredecessor() != 0) {
if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
if (HoistThenElseCodeToIf(BI))
return SimplifyCFG(BB) | true;
} else {
// If Successor #1 has multiple preds, we may be able to conditionally
// execute Successor #0 if it branches to successor #1.
TerminatorInst *Succ0TI = BI->getSuccessor(0)->getTerminator();
if (Succ0TI->getNumSuccessors() == 1 &&
Succ0TI->getSuccessor(0) == BI->getSuccessor(1))
if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0)))
return SimplifyCFG(BB) | true;
}
} else if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
// If Successor #0 has multiple preds, we may be able to conditionally
// execute Successor #1 if it branches to successor #0.
TerminatorInst *Succ1TI = BI->getSuccessor(1)->getTerminator();
if (Succ1TI->getNumSuccessors() == 1 &&
Succ1TI->getSuccessor(0) == BI->getSuccessor(0))
if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1)))
return SimplifyCFG(BB) | true;
}
// If this is a branch on a phi node in the current block, thread control
// through this block if any PHI node entries are constants.
@ -2326,28 +2344,6 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
}
}
// Otherwise, if this block only has a single predecessor, and if that block
// is a conditional branch, see if we can hoist any code from this block up
// into our predecessor.
if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) {
BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator());
if (BI && BI->isConditional()) {
// Get the other block.
BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
if (OtherBB->getSinglePredecessor() == 0) {
TerminatorInst *BBTerm = BB->getTerminator();
if (BBTerm->getNumSuccessors() == 1 &&
BBTerm->getSuccessor(0) == OtherBB) {
// If BB's only successor is the other successor of the predecessor,
// i.e. a triangle, see if we can hoist any code from this block up
// to the "if" block.
Changed |= SpeculativelyExecuteBB(BI, BB);
}
}
}
}
return Changed;
}