From ce17b1c1f8761f5fabb4b0531b7127254cdc89de Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Mon, 16 Jul 2007 23:34:39 +0000
Subject: [PATCH] Take advantage of undefined behavior if the source program
 tries to GEP beyond the end of an alloca to make FastDSE faster and more
 aggressive.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39945 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/FastDSE.cpp | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/lib/Transforms/Scalar/FastDSE.cpp b/lib/Transforms/Scalar/FastDSE.cpp
index 45985ba7175..72857b9c47a 100644
--- a/lib/Transforms/Scalar/FastDSE.cpp
+++ b/lib/Transforms/Scalar/FastDSE.cpp
@@ -61,17 +61,10 @@ namespace {
       
       // See through pointer-to-pointer bitcasts
       while (isa<BitCastInst>(v) || isa<GetElementPtrInst>(v))
-        if (BitCastInst* C = dyn_cast<BitCastInst>(v)) {
-          if (isa<PointerType>(C->getSrcTy()))
-            v = C->getOperand(0);
-          else
-            break;
-        } else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(v)) {
-          if (G->hasAllZeroIndices())
-            v = G->getOperand(0);
-          else
-            break;
-        }
+        if (BitCastInst* C = dyn_cast<BitCastInst>(v))
+          v = C->getOperand(0);
+        else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(v))
+          v = G->getOperand(0);
     }
 
     // getAnalysisUsage - We require post dominance frontiers (aka Control