1 files changed, 15 insertions, 3 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index 7446a51a4d..fa68000df5 100644
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -379,10 +379,22 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
     unsigned EffectiveStoreAlign = StoreAlign != 0 ? StoreAlign :
       TD->getABITypeAlignment(Val->getType());
 
-    if (KnownAlign > EffectiveStoreAlign)
+    if (KnownAlign > EffectiveStoreAlign) {
       SI.setAlignment(KnownAlign);
-    else if (StoreAlign == 0)
-      SI.setAlignment(EffectiveStoreAlign);
+    } else if (StoreAlign == 0) {
+      unsigned PtrAlign = 0;
+      if (GlobalValue *GV = dyn_cast<GlobalValue>(Ptr->stripPointerCasts()))
+        PtrAlign = GV->getAlignment();
+
+      if (PtrAlign != 0 && PtrAlign < EffectiveStoreAlign)
+        // The pointer alignment may be less than the effective store
+        // alignment. If so, then we don't want to increase the alignment here,
+        // since that could lead to code-gen using instructions which require a
+        // higher alignment than the pointer guarantees.
+        SI.setAlignment(PtrAlign);
+      else
+        SI.setAlignment(EffectiveStoreAlign);
+    }
   }
 
   // Don't hack volatile/atomic stores.