[llvm] r213497 - Fix for regression: [Bug 20369] wrong code at -O3 on x86_64-linux-gnu in 64-bit mode

[Gerolf Hoflehner]

Author: ghoflehner
Date: Sun Jul 20 22:02:46 2014
New Revision: 213497

URL: http://llvm.org/viewvc/llvm-project?rev=213497&view=rev
Log:
Fix for regression: [Bug 20369] wrong code at -O3 on x86_64-linux-gnu in 64-bit mode

Prevents hoisting of loads above stores and sinking of stores below loads
in MergedLoadStoreMotion.cpp (rdar://15991737)


Modified:
    llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp?rev=213497&r1=213496&r2=213497&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp Sun Jul 20 22:02:46 2014
@@ -243,6 +243,10 @@ bool MergedLoadStoreMotion::isLoadHoistB
     return true;
   if (isa<TerminatorInst>(Inst))
     return true;
+  // FIXME: Conservatively let a store instruction block the load.
+  // Use alias analysis instead.
+  if (isa<StoreInst>(Inst))
+    return true;
   // Note: mayHaveSideEffects covers all instructions that could
   // trigger a change to state. Eg. in-flight stores have to be executed
   // before ordered loads or fences, calls could invoke functions that store
@@ -411,8 +415,12 @@ bool MergedLoadStoreMotion::mergeLoads(B
 
 ///
 /// \brief True when instruction is sink barrier for a store
-///
+/// 
 bool MergedLoadStoreMotion::isStoreSinkBarrier(Instruction *Inst) {
+  // FIXME: Conservatively let a load instruction block the store.
+  // Use alias analysis instead.
+  if (isa<LoadInst>(Inst))
+    return true;
   if (isa<CallInst>(Inst))
     return true;
   if (isa<TerminatorInst>(Inst) && !isa<BranchInst>(Inst))