X86: when constructing VZEXT_LOAD from other loads, makes sure its output
chain is correctly setup.
As an example, if the original load must happen before later stores, we need
to make sure the constructed VZEXT_LOAD is constrained to be before the stores.
rdar://12684358
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167859 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index b35fb51..0259703 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -14203,6 +14203,18 @@
Ld->getAlignment(),
false/*isVolatile*/, true/*ReadMem*/,
false/*WriteMem*/);
+
+ // Make sure the newly-created LOAD is in the same position as Ld in
+ // terms of dependency. We create a TokenFactor for Ld and ResNode,
+ // and update uses of Ld's output chain to use the TokenFactor.
+ if (Ld->hasAnyUseOfValue(1)) {
+ SDValue NewChain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
+ SDValue(Ld, 1), SDValue(ResNode.getNode(), 1));
+ DAG.ReplaceAllUsesOfValueWith(SDValue(Ld, 1), NewChain);
+ DAG.UpdateNodeOperands(NewChain.getNode(), SDValue(Ld, 1),
+ SDValue(ResNode.getNode(), 1));
+ }
+
return DAG.getNode(ISD::BITCAST, dl, VT, ResNode);
}
}