Don't shrink atomic ops to bool in GlobalOpt.

LLVM IR doesn't currently allow atomic bool load/store operations, and the
transformation is dubious anyway because it isn't profitable on all platforms.

PR17163.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190357 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 4 deletions

diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index 4659271..29c1b6a 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2046,11 +2046,14 @@ bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
 
     // Otherwise, if the global was not a boolean, we can shrink it to be a
     // boolean.
-    if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
-      if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
-        ++NumShrunkToBool;
-        return true;
+    if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) {
+      if (GS.Ordering == NotAtomic) {
+        if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
+          ++NumShrunkToBool;
+          return true;
+        }
       }
+    }
   }
 
   return false;