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Fix a fixme in CondPropagate.cpp by moving a PhiNode optimization into

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BasicBlock's removePredecessor routine.  This requires shuffling around
the definition and implementation of hasContantValue from Utils.h,cpp into
Instructions.h,cpp


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22664 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman
2005-08-04 23:24:19 +00:00
parent f065f05397
commit a83ba0f5c9
9 changed files with 48 additions and 62 deletions
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34
lib/Transforms/Utils/Local.cpp
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@ -406,37 +406,3 @@ bool llvm::dceInstruction(BasicBlock::iterator &BBI) {
}
return false;
}
//===----------------------------------------------------------------------===//
// PHI Instruction Simplification
//
/// hasConstantValue - If the specified PHI node always merges together the same
/// value, return the value, otherwise return null.
///
Value *llvm::hasConstantValue(PHINode *PN) {
// If the PHI node only has one incoming value, eliminate the PHI node...
if (PN->getNumIncomingValues() == 1)
return PN->getIncomingValue(0);
// Otherwise if all of the incoming values are the same for the PHI, replace
// the PHI node with the incoming value.
//
Value *InVal = 0;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) != PN && // Not the PHI node itself...
!isa<UndefValue>(PN->getIncomingValue(i)))
if (InVal && PN->getIncomingValue(i) != InVal)
return 0; // Not the same, bail out.
else
InVal = PN->getIncomingValue(i);
// The only case that could cause InVal to be null is if we have a PHI node
// that only has entries for itself. In this case, there is no entry into the
// loop, so kill the PHI.
//
if (InVal == 0) InVal = UndefValue::get(PN->getType());
// All of the incoming values are the same, return the value now.
return InVal;
}