Fix a problem with incomplete equality testing of PHINodes in

Instruction::IsIdenticalToWhenDefined.

This manifested itself when inlining two calls to the same function.  The 
inlined function had a switch statement that returned one of a set of 
global variables.  Without this modification, the two phi instructions that 
chose values from the branches of the switch instruction inlined from the 
callee were considered equivalent and jump-threading replaced a load for the 
first switch value with a phi selecting from the second switch, thereby 
producing incorrect code.

This patch has been tested with "make check-all", "lnt runteste nt", and 
llvm self-hosted, and on the original program that had this problem, 
wireshark.

<rdar://problem/11025519>

llvm-svn: 156548

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/VMCore/Instruction.cpp b/llvm/lib/VMCore/Instruction.cpp
index 5449714280d..c1d63877575 100644
--- a/llvm/lib/VMCore/Instruction.cpp
+++ b/llvm/lib/VMCore/Instruction.cpp
@@ -226,7 +226,14 @@ bool Instruction::isIdenticalToWhenDefined(const Instruction *I) const {
            RMWI->isVolatile() == cast<AtomicRMWInst>(I)->isVolatile() &&
            RMWI->getOrdering() == cast<AtomicRMWInst>(I)->getOrdering() &&
            RMWI->getSynchScope() == cast<AtomicRMWInst>(I)->getSynchScope();
-
+  if (const PHINode *thisPHI = dyn_cast<PHINode>(this)) {
+    const PHINode *otherPHI = cast<PHINode>(I);
+    for (unsigned i = 0, e = thisPHI->getNumOperands(); i != e; ++i) {
+      if (thisPHI->getIncomingBlock(i) != otherPHI->getIncomingBlock(i))
+        return false;
+    }
+    return true;
+  }
   return true;
 }