[X86] Fix chains update when lowering BUILD_VECTOR to a vector load

The code which lowers BUILD_VECTOR of consecutive loads into a single vector
load doesn't update chains properly. As a result the vector load can be
reordered with the store to the same location.

The current code in EltsFromConsecutiveLoads only updates the chain following
the first load. The fix is to update the chains following all the loads
comprising the vector.

This is a fix for PR10114.

Reviewed By: niravd

Differential Revision: https://reviews.llvm.org/D38547

llvm-svn: 314988

1 files changed, 10 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9aae58b5555..b0e0b439257 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6540,14 +6540,20 @@ static SDValue EltsFromConsecutiveLoads(EVT VT, ArrayRef<SDValue> Elts,
     }
   }
 
-  auto CreateLoad = [&DAG, &DL](EVT VT, LoadSDNode *LDBase) {
+  SmallVector<LoadSDNode *, 8> Loads;
+  for (int i = FirstLoadedElt; i <= LastLoadedElt; ++i)
+    if (LoadMask[i])
+      Loads.push_back(cast<LoadSDNode>(peekThroughBitcasts(Elts[i])));
+
+  auto CreateLoad = [&DAG, &DL, &Loads](EVT VT, LoadSDNode *LDBase) {
     auto MMOFlags = LDBase->getMemOperand()->getFlags();
     assert(!(MMOFlags & MachineMemOperand::MOVolatile) &&
            "Cannot merge volatile loads.");
     SDValue NewLd =
         DAG.getLoad(VT, DL, LDBase->getChain(), LDBase->getBasePtr(),
                     LDBase->getPointerInfo(), LDBase->getAlignment(), MMOFlags);
-    DAG.makeEquivalentMemoryOrdering(LDBase, NewLd);
+    for (auto *LD : Loads)
+      DAG.makeEquivalentMemoryOrdering(LD, NewLd);
     return NewLd;
   };
 
@@ -6612,7 +6618,8 @@ static SDValue EltsFromConsecutiveLoads(EVT VT, ArrayRef<SDValue> Elts,
                                   LDBase->getAlignment(),
                                   false/*isVolatile*/, true/*ReadMem*/,
                                   false/*WriteMem*/);
-      DAG.makeEquivalentMemoryOrdering(LDBase, ResNode);
+      for (auto *LD : Loads)
+        DAG.makeEquivalentMemoryOrdering(LD, ResNode);
       return DAG.getBitcast(VT, ResNode);
     }
   }