[DAGCombiner] Don't allow addcarry if the carry producer is illegal.

getAsCarry() checks that the input argument is a carry-producing node before
allowing a transformation to addcarry. This patch adds a check to make sure
that the carry-producing node is legal. If it is not, it may not remain in a
form that is manageable by the target backend. The test case caused a
compilation failure during instruction selection for this reason on SystemZ.

Patch by Ulrich Weigand.

Review: Sanjay Patel
https://reviews.llvm.org/D59822

llvm-svn: 357052

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 498e6fdcc7a..b0ad8c0c989 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2336,6 +2336,10 @@ static SDValue getAsCarry(const TargetLowering &TLI, SDValue V) {
       V.getOpcode() != ISD::UADDO && V.getOpcode() != ISD::USUBO)
     return SDValue();
 
+  EVT VT = V.getNode()->getValueType(0);
+  if (!TLI.isOperationLegalOrCustom(V.getOpcode(), VT))
+    return SDValue();
+
   // If the result is masked, then no matter what kind of bool it is we can
   // return. If it isn't, then we need to make sure the bool type is either 0 or
   // 1 and not other values.