[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.

llvm-svn: 242126

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index 056dd11..d1a0a82 100644 (file)
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -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);
 

diff --git a/llvm/test/Transforms/SROA/basictest.ll b/llvm/test/Transforms/SROA/basictest.ll
index a59192d..7c8955b 100644 (file)
--- a/llvm/test/Transforms/SROA/basictest.ll
+++ b/llvm/test/Transforms/SROA/basictest.ll
@@ -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
+}