[GVN] PRE of unordered loads

Again, fairly simple.  Only change is ensuring that we actually copy the property of the load correctly.  The aliasing legality constraints were already handled by the FRE patches.  There's nothing special about unorder atomics from the perspective of the PRE algorithm itself.

llvm-svn: 268804

1 files changed, 4 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 7e937bf954a..97ec1eab654 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1552,9 +1552,10 @@ bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
     BasicBlock *UnavailablePred = PredLoad.first;
     Value *LoadPtr = PredLoad.second;
 
-    Instruction *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
-                                        LI->getAlignment(),
-                                        UnavailablePred->getTerminator());
+    auto *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre",
+                                 LI->isVolatile(), LI->getAlignment(),
+                                 LI->getOrdering(), LI->getSynchScope(),
+                                 UnavailablePred->getTerminator());
 
     // Transfer the old load's AA tags to the new load.
     AAMDNodes Tags;
@@ -1664,11 +1665,6 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
     return true;
   }
 
-  // This code hasn't been audited for atomic, ordered, or volatile memory
-  // access.
-  if (!LI->isSimple())
-    return false;
-
   // Step 4: Eliminate partial redundancy.
   if (!EnablePRE || !EnableLoadPRE)
     return false;