From 2a27389edc504ba4f933b8042d8cc5b0cca53248 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 14 Jul 2015 06:19:58 +0000
Subject: [PATCH] [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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242126 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SROA.cpp    | 21 +++++++++++++++------
 test/Transforms/SROA/basictest.ll | 11 +++++++++++
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp
index 056dd11b5ab..d1a0a82b9b0 100644
--- a/lib/Transforms/Scalar/SROA.cpp
+++ b/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/test/Transforms/SROA/basictest.ll b/test/Transforms/SROA/basictest.ll
index a59192d718c..7c8955b28fa 100644
--- a/test/Transforms/SROA/basictest.ll
+++ b/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
+}
-- 
2.34.1