DAG: Ignore call site attributes when emitting target intrinsic

A target intrinsic may be defined as possibly reading memory,
but the call site may have additional knowledge that it doesn't read
memory. The intrinsic lowering will expect the pessimistic
assumption of the intrinsic definition, so the chain should
still be used.

llvm-svn: 287593

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4bb3cd2055e..4594f92317c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4061,8 +4061,12 @@ void SelectionDAGBuilder::visitAtomicStore(const StoreInst &I) {
 /// node.
 void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I,
                                                unsigned Intrinsic) {
-  bool HasChain = !I.doesNotAccessMemory();
-  bool OnlyLoad = HasChain && I.onlyReadsMemory();
+  // Ignore the callsite's attributes. A specific call site may be marked with
+  // readnone, but the lowering code will expect the chain based on the
+  // definition.
+  const Function *F = I.getCalledFunction();
+  bool HasChain = !F->doesNotAccessMemory();
+  bool OnlyLoad = HasChain && F->onlyReadsMemory();
 
   // Build the operand list.
   SmallVector<SDValue, 8> Ops;