SelectionDAG: Make sure stores are always added to the LegalizedNodes list

When truncated vector stores were being custom lowered in
VectorLegalizer::LegalizeOp(), the old (illegal) and new (legal) node pair
was not being added to LegalizedNodes list.  Instead of the legalized
result being passed to VectorLegalizer::TranslateLegalizeResult(),
the result was being passed back into VectorLegalizer::LegalizeOp(),
which ended up adding a (new, new) pair to the list instead.

This was causing an assertion failure when a custom lowered truncated
vector store was the last instruction a basic block and the VectorLegalizer
was unable to find it in the LegalizedNodes list when updating the
DAG root.

llvm-svn: 188953

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

@@ -171,7 +171,7 @@ SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
         return TranslateLegalizeResults(Op, Result);
       case TargetLowering::Custom:
         Changed = true;
-        return LegalizeOp(TLI.LowerOperation(Result, DAG));
+        return TranslateLegalizeResults(Op, TLI.LowerOperation(Result, DAG));
       case TargetLowering::Expand:
         Changed = true;
         return LegalizeOp(ExpandStore(Op));

llvm/test/CodeGen/R600/trunc-vector-store-assertion-failure.ll

@@ -0,0 +1,20 @@
+; RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck %s
+
+; This tests for a bug in the SelectionDAG where custom lowered truncated
+; vector stores at the end of a basic block were not being added to the
+; LegalizedNodes list, which triggered an assertion failure.
+
+; CHECK-LABEL: @test
+; CHECK: MEM_RAT_CACHELESS STORE_RAW
+define void @test(<4 x i8> addrspace(1)* %out, i32 %cond, <4 x i8> %in) {
+entry:
+  %0 = icmp eq i32 %cond, 0
+  br i1 %0, label %if, label %done
+
+if:
+  store <4 x i8> %in, <4 x i8> addrspace(1)* %out
+  br label %done
+
+done:
+  ret void
+}