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Try to place hoisted instructions befoe icmp instruction.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56315 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2008-09-18 22:50:42 +00:00
parent 841ee1a12b
commit 3d0a9a371c
1 changed files with 23 additions and 2 deletions
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25
lib/Transforms/Utils/SimplifyCFG.cpp
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@@ -1046,8 +1046,29 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
return false; return false;
} }
// If we get here, we can hoist the instruction. // If we get here, we can hoist the instruction. Try to place it
BIParent->getInstList().splice(BI, BB1->getInstList(), I); // before the icmp instruction preceeding the conditional branch.
BasicBlock::iterator InsertPos = BI;
if (InsertPos != BIParent->begin())
--InsertPos;
if (InsertPos == BrCond) {
SmallPtrSet<Instruction *, 4> BB1Insns;
for(BasicBlock::iterator BB1I = BB1->begin(), BB1E = BB1->end();
BB1I != BB1E; ++BB1I)
BB1Insns.insert(BB1I);
for(Value::use_iterator UI = BrCond->use_begin(), UE = BrCond->use_end();
UI != UE; ++UI) {
Instruction *Use = cast<Instruction>(*UI);
if (BB1Insns.count(Use)) {
// If BrCond uses the instruction that place it just before
// branch instruction.
InsertPos = BI;
break;
}
}
} else
InsertPos = BI;
BIParent->getInstList().splice(InsertPos, BB1->getInstList(), I);
// Create a select whose true value is the speculatively executed value and // Create a select whose true value is the speculatively executed value and
// false value is the previously determined FalseV. // false value is the previously determined FalseV.