From d896a400f1d1c4ff7bedf3ea3c2f13a15bce0476 Mon Sep 17 00:00:00 2001
From: Nuno Lopes <nunoplopes@sapo.pt>
Date: Mon, 31 Dec 2012 20:45:10 +0000
Subject: recommit r171298 (add support for PHI nodes to
 ObjectSizeOffsetVisitor). Hopefully with bugs corrected now.

llvm-svn: 171325
---
 llvm/lib/Analysis/MemoryBuiltins.cpp | 37 +++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

(limited to 'llvm/lib/Analysis/MemoryBuiltins.cpp')

diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
index 14815801d1e..2eebaad495a 100644
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -385,16 +385,21 @@ ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout *TD,
 
 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   V = V->stripPointerCasts();
-  if (Instruction *I = dyn_cast<Instruction>(V)) {
-    // If we have already seen this instruction, bail out. Cycles can happen in
-    // unreachable code after constant propagation.
-    if (!SeenInsts.insert(I))
+
+  if (isa<Instruction>(V) || isa<GEPOperator>(V)) {
+    // If we have already seen this instruction, bail out.
+    if (!SeenInsts.insert(V))
       return unknown();
 
+    SizeOffsetType Ret;
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
-      return visitGEPOperator(*GEP);
-    return visit(*I);
+      Ret = visitGEPOperator(*GEP);
+    else
+      Ret = visit(cast<Instruction>(*V));
+    SeenInsts.erase(V);
+    return Ret;
   }
+
   if (Argument *A = dyn_cast<Argument>(V))
     return visitArgument(*A);
   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
@@ -408,8 +413,6 @@ SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (CE->getOpcode() == Instruction::IntToPtr)
       return unknown(); // clueless
-    if (CE->getOpcode() == Instruction::GetElementPtr)
-      return visitGEPOperator(cast<GEPOperator>(*CE));
   }
 
   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
@@ -543,9 +546,21 @@ 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) {
+    SizeOffsetType EdgeData = compute(PHI.getIncomingValue(i));
+    if (!bothKnown(EdgeData) || EdgeData != Ret)
+      return unknown();
+  }
+  return Ret;
 }
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
-- 
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