Optimize alignment of loads and stores.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40102 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 816a1c6..33fd843 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -8790,6 +8790,11 @@ static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
   Value *Op = LI.getOperand(0);
 
+  // Attempt to improve the alignment.
+  unsigned KnownAlign = GetKnownAlignment(Op, TD);
+  if (KnownAlign > LI.getAlignment())
+    LI.setAlignment(KnownAlign);
+
   // load (cast X) --> cast (load X) iff safe
   if (isa<CastInst>(Op))
     if (Instruction *Res = InstCombineLoadCast(*this, LI))
@@ -8985,6 +8990,11 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
       }
   }
 
+  // Attempt to improve the alignment.
+  unsigned KnownAlign = GetKnownAlignment(Ptr, TD);
+  if (KnownAlign > SI.getAlignment())
+    SI.setAlignment(KnownAlign);
+
   // Do really simple DSE, to catch cases where there are several consequtive
   // stores to the same location, separated by a few arithmetic operations. This
   // situation often occurs with bitfield accesses.