Fix an issue with the IR sink pass found by inspection. (I'm not sure anyone is actually using this, but might as well fix it since I found the issue.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138965 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 22 insertions, 7 deletions

diff --git a/lib/Transforms/Scalar/Sink.cpp b/lib/Transforms/Scalar/Sink.cpp
index 705f442049..c83f56c4d2 100644
--- a/lib/Transforms/Scalar/Sink.cpp
+++ b/lib/Transforms/Scalar/Sink.cpp
@@ -153,9 +153,13 @@ bool Sinking::ProcessBlock(BasicBlock &BB) {
 
 static bool isSafeToMove(Instruction *Inst, AliasAnalysis *AA,
                          SmallPtrSet<Instruction *, 8> &Stores) {
-  if (LoadInst *L = dyn_cast<LoadInst>(Inst)) {
-    if (L->isVolatile()) return false;
 
+  if (Inst->mayWriteToMemory()) {
+    Stores.insert(Inst);
+    return false;
+  }
+
+  if (LoadInst *L = dyn_cast<LoadInst>(Inst)) {
     AliasAnalysis::Location Loc = AA->getLocation(L);
     for (SmallPtrSet<Instruction *, 8>::iterator I = Stores.begin(),
          E = Stores.end(); I != E; ++I)
@@ -163,11 +167,6 @@ static bool isSafeToMove(Instruction *Inst, AliasAnalysis *AA,
         return false;
   }
 
-  if (Inst->mayWriteToMemory()) {
-    Stores.insert(Inst);
-    return false;
-  }
-
   if (isa<TerminatorInst>(Inst) || isa<PHINode>(Inst))
     return false;
 
diff --git a/test/Transforms/Sink/basic.ll b/test/Transforms/Sink/basic.ll
index 54b7f1369d..81782e9d42 100644
--- a/test/Transforms/Sink/basic.ll
+++ b/test/Transforms/Sink/basic.ll
@@ -20,3 +20,19 @@ true:
 false:
   ret i32 0
 }
+
+; But don't sink volatile loads...
+
+;      CHECK: @foo2
+;      CHECK: volatile load
+; CHECK-NEXT: store i32
+
+define i32 @foo2(i1 %z) {
+  %l = volatile load i32* @A
+  store i32 0, i32* @B
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}