[DAGCombiner] Do not generate ISD::ADDE node if adde is not legal for the target when combine ISD::TRUNC node

Do not combine (trunc adde(X, Y, Carry)) into (adde trunc(X), trunc(Y), Carry), 
if adde is not legal for the target. Even it's at type-legalize phase. 
Because adde is special and will not be legalized at operation-legalize phase later.

This fixes: PR40922
https://bugs.llvm.org/show_bug.cgi?id=40922

Differential Revision: https://reviews.llvm.org//D60854

llvm-svn: 359532

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index df1929bf36b..aeab54d65a8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10257,7 +10257,9 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
   // When the adde's carry is not used.
   if ((N0.getOpcode() == ISD::ADDE || N0.getOpcode() == ISD::ADDCARRY) &&
       N0.hasOneUse() && !N0.getNode()->hasAnyUseOfValue(1) &&
-      (!LegalOperations || TLI.isOperationLegal(N0.getOpcode(), VT))) {
+      // We only do for addcarry before legalize operation
+      ((!LegalOperations && N0.getOpcode() == ISD::ADDCARRY) ||
+       TLI.isOperationLegal(N0.getOpcode(), VT))) {
     SDLoc SL(N);
     auto X = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
     auto Y = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(1));