[llvm] r242126 - [SROA] Don't de-atomic volatile loads and stores

[David Majnemer]

Author: majnemer
Date: Tue Jul 14 01:19:58 2015
New Revision: 242126

URL: http://llvm.org/viewvc/llvm-project?rev=242126&view=rev
Log:
[SROA] Don't de-atomic volatile loads and stores

Volatile loads and stores are made visible in global state regardless of
what memory is involved.  It is not correct to disregard the ordering
and synchronization scope because it is possible to synchronize with
memory operations performed by hardware.

This partially addresses PR23737.

Modified:
    llvm/trunk/lib/Transforms/Scalar/SROA.cpp
    llvm/trunk/test/Transforms/SROA/basictest.ll

Modified: llvm/trunk/lib/Transforms/Scalar/SROA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SROA.cpp?rev=242126&r1=242125&r2=242126&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SROA.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SROA.cpp Tue Jul 14 01:19:58 2015
@@ -2593,13 +2593,21 @@ private:
       V = rewriteIntegerLoad(LI);
     } else if (NewBeginOffset == NewAllocaBeginOffset &&
                canConvertValue(DL, NewAllocaTy, LI.getType())) {
-      V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), LI.isVolatile(),
-                                LI.getName());
+      LoadInst *NewLI = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
+                                              LI.isVolatile(), LI.getName());
+      if (LI.isVolatile())
+        NewLI->setAtomic(LI.getOrdering(), LI.getSynchScope());
+
+      V = NewLI;
     } else {
       Type *LTy = TargetTy->getPointerTo();
-      V = IRB.CreateAlignedLoad(getNewAllocaSlicePtr(IRB, LTy),
-                                getSliceAlign(TargetTy), LI.isVolatile(),
-                                LI.getName());
+      LoadInst *NewLI = IRB.CreateAlignedLoad(getNewAllocaSlicePtr(IRB, LTy),
+                                              getSliceAlign(TargetTy),
+                                              LI.isVolatile(), LI.getName());
+      if (LI.isVolatile())
+        NewLI->setAtomic(LI.getOrdering(), LI.getSynchScope());
+
+      V = NewLI;
       IsPtrAdjusted = true;
     }
     V = convertValue(DL, IRB, V, TargetTy);
@@ -2722,7 +2730,8 @@ private:
       NewSI = IRB.CreateAlignedStore(V, NewPtr, getSliceAlign(V->getType()),
                                      SI.isVolatile());
     }
-    (void)NewSI;
+    if (SI.isVolatile())
+      NewSI->setAtomic(SI.getOrdering(), SI.getSynchScope());
     Pass.DeadInsts.insert(&SI);
     deleteIfTriviallyDead(OldOp);
 

Modified: llvm/trunk/test/Transforms/SROA/basictest.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SROA/basictest.ll?rev=242126&r1=242125&r2=242126&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SROA/basictest.ll (original)
+++ llvm/trunk/test/Transforms/SROA/basictest.ll Tue Jul 14 01:19:58 2015
@@ -1595,3 +1595,14 @@ entry:
   store i32 %load, i32* %a.gep1
   ret void
 }
+
+define void @PR23737() {
+; CHECK-LABEL: @PR23737(
+; CHECK: store atomic volatile {{.*}} seq_cst
+; CHECK: load atomic volatile {{.*}} seq_cst
+entry:
+  %ptr = alloca i64, align 8
+  store atomic volatile i64 0, i64* %ptr seq_cst, align 8
+  %load = load atomic volatile i64, i64* %ptr seq_cst, align 8
+  ret void
+}