From 0b875a0c29d5f97c8a5e09404e0de79c4fe49858 Mon Sep 17 00:00:00 2001
From: Duncan Sands <baldrick@free.fr>
Date: Wed, 25 Jul 2012 09:14:54 +0000
Subject: When folding a load from a global constant, if the load started in
 the middle of an array element (rather than at the beginning of the element)
 and extended into the next element, then the load from the second element was
 being handled wrong due to incorrect updating of the notion of which byte to
 load next.  This fixes PR13442.  Thanks to Chris Smowton for reporting the
 problem, analyzing it and providing a fix.

llvm-svn: 160711
---
 llvm/lib/Analysis/ConstantFolding.cpp | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

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

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 7ced848aa1b..a7c9e550432 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -358,17 +358,20 @@ static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset,
       NumElts = AT->getNumElements();
     else
       NumElts = cast<VectorType>(C->getType())->getNumElements();
-    
+
     for (; Index != NumElts; ++Index) {
       if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr,
                               BytesLeft, TD))
         return false;
-      if (EltSize >= BytesLeft)
+
+      uint64_t BytesWritten = EltSize - Offset;
+      assert(BytesWritten <= EltSize && "Not indexing into this element?");
+      if (BytesWritten >= BytesLeft)
         return true;
-      
+
       Offset = 0;
-      BytesLeft -= EltSize;
-      CurPtr += EltSize;
+      BytesLeft -= BytesWritten;
+      CurPtr += BytesWritten;
     }
     return true;
   }
-- 
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