Fix a fixme in CondPropagate.cpp by moving a PhiNode optimization into
BasicBlock's removePredecessor routine. This requires shuffling around
the definition and implementation of hasContantValue from Utils.h,cpp into
Instructions.h,cpp
llvm-svn: 22664
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index 68b685e..e454d6b 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -132,6 +132,36 @@
OperandList = NewOps;
}
+/// hasConstantValue - If the specified PHI node always merges together the same
+/// value, return the value, otherwise return null.
+///
+Value *PHINode::hasConstantValue() {
+ // If the PHI node only has one incoming value, eliminate the PHI node...
+ if (getNumIncomingValues() == 1)
+ return 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 = getNumIncomingValues(); i != e; ++i)
+ if (getIncomingValue(i) != this && // Not the PHI node itself...
+ !isa<UndefValue>(getIncomingValue(i)))
+ if (InVal && getIncomingValue(i) != InVal)
+ return 0; // Not the same, bail out.
+ else
+ InVal = 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(getType());
+
+ // All of the incoming values are the same, return the value now.
+ return InVal;
+}
+
//===----------------------------------------------------------------------===//
// CallInst Implementation