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Remove dead code in SimplifyCFG

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Summary: UsedByBranch is always true according to how BonusInst is defined.

Test Plan:
Passes check-all, and also verified 

if (BonusInst && !UsedByBranch) {
  ...
}

is never entered during check-all.

Reviewers: resistor, nadav, jingyue

Reviewed By: jingyue

Subscribers: llvm-commits, eliben, meheff

Differential Revision: http://reviews.llvm.org/D5324

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217824 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jingyue Wu 2014-09-15 20:48:13 +00:00
parent 86bdc1efbe
commit 5e49dcf79a
1 changed files with 0 additions and 43 deletions
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43
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -2096,49 +2096,6 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, const DataLayout *DL) {
continue;
}
// Ensure that any values used in the bonus instruction are also used
// by the terminator of the predecessor. This means that those values
// must already have been resolved, so we won't be inhibiting the
// out-of-order core by speculating them earlier. We also allow
// instructions that are used by the terminator's condition because it
// exposes more merging opportunities.
bool UsedByBranch = (BonusInst && BonusInst->hasOneUse() &&
BonusInst->user_back() == Cond);
if (BonusInst && !UsedByBranch) {
// Collect the values used by the bonus inst
SmallPtrSet<Value*, 4> UsedValues;
for (Instruction::op_iterator OI = BonusInst->op_begin(),
OE = BonusInst->op_end(); OI != OE; ++OI) {
Value *V = *OI;
if (!isa<Constant>(V) && !isa<Argument>(V))
UsedValues.insert(V);
}
SmallVector<std::pair<Value*, unsigned>, 4> Worklist;
Worklist.push_back(std::make_pair(PBI->getOperand(0), 0));
// Walk up to four levels back up the use-def chain of the predecessor's
// terminator to see if all those values were used. The choice of four
// levels is arbitrary, to provide a compile-time-cost bound.
while (!Worklist.empty()) {
std::pair<Value*, unsigned> Pair = Worklist.back();
Worklist.pop_back();
if (Pair.second >= 4) continue;
UsedValues.erase(Pair.first);
if (UsedValues.empty()) break;
if (Instruction *I = dyn_cast<Instruction>(Pair.first)) {
for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
OI != OE; ++OI)
Worklist.push_back(std::make_pair(OI->get(), Pair.second+1));
}
}
if (!UsedValues.empty()) return false;
}
DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
IRBuilder<> Builder(PBI);