Change PHINode::hasConstantValue to have a DominatorTree argument
instead of a bool argument, and to do the dominator check itself.
This makes it eaiser to use when DominatorTree information is
available.
llvm-svn: 80920
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index a12075f..2d4ab55 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -17,6 +17,7 @@
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Operator.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/ConstantRange.h"
@@ -226,7 +227,12 @@
/// hasConstantValue - If the specified PHI node always merges together the same
/// value, return the value, otherwise return null.
///
-Value *PHINode::hasConstantValue(bool AllowNonDominatingInstruction) const {
+/// If the PHI has undef operands, but all the rest of the operands are
+/// some unique value, return that value if it can be proved that the
+/// value dominates the PHI. If DT is null, use a conservative check,
+/// otherwise use DT to test for dominance.
+///
+Value *PHINode::hasConstantValue(DominatorTree *DT) const {
// If the PHI node only has one incoming value, eliminate the PHI node...
if (getNumIncomingValues() == 1) {
if (getIncomingValue(0) != this) // not X = phi X
@@ -260,12 +266,19 @@
// instruction, we cannot always return X as the result of the PHI node. Only
// do this if X is not an instruction (thus it must dominate the PHI block),
// or if the client is prepared to deal with this possibility.
- if (HasUndefInput && !AllowNonDominatingInstruction)
- if (Instruction *IV = dyn_cast<Instruction>(InVal))
- // If it's in the entry block, it dominates everything.
- if (IV->getParent() != &IV->getParent()->getParent()->getEntryBlock() ||
- isa<InvokeInst>(IV))
- return 0; // Cannot guarantee that InVal dominates this PHINode.
+ if (HasUndefInput)
+ if (Instruction *IV = dyn_cast<Instruction>(InVal)) {
+ if (DT) {
+ // We have a DominatorTree. Do a precise test.
+ if (!DT->dominates(IV, this))
+ return 0;
+ } else {
+ // If it's in the entry block, it dominates everything.
+ if (IV->getParent() != &IV->getParent()->getParent()->getEntryBlock() ||
+ isa<InvokeInst>(IV))
+ return 0; // Cannot guarantee that InVal dominates this PHINode.
+ }
+ }
// All of the incoming values are the same, return the value now.
return InVal;