add support for PHI nodes to ObjectSizeOffsetVisitor

llvm-svn: 171298

1 files changed, 14 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
index cfd8fcfdb71..2503bfa2161 100644
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -535,9 +535,20 @@ SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
   return unknown();
 }
 
-SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
-  // too complex to analyze statically.
-  return unknown();
+SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PHI) {
+  if (PHI.getNumIncomingValues() == 0)
+    return unknown();
+
+  SizeOffsetType Ret = compute(PHI.getIncomingValue(0));
+  if (!bothKnown(Ret))
+    return unknown();
+
+  // verify that all PHI incoming pointers have the same size and offset
+  for (unsigned i = 1, e = PHI.getNumIncomingValues(); i != e; ++i) {
+    if (compute(PHI.getIncomingValue(i)) != Ret)
+      return unknown();
+  }
+  return Ret;
 }
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {