[LegalizeTypes] Avoid creating an unused node in ExpandIntRes_ADDSUB.…

… NFC The Hi result is sometimes calculated a different way and this node goes unused. Defer creation until we know for sure it is neeeded. The test changes is because the node creation order changed the names in the debug output.
llvm · Sep 10, 2024 · d2f25e5 · d2f25e5
1 parent ae5f1a7
commit d2f25e5
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Showing 2 changed files with 6 additions and 5 deletions.
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -3496,7 +3496,6 @@ void DAGTypeLegalizer::ExpandIntRes_ADDSUB(SDNode *N,
 
   if (N->getOpcode() == ISD::ADD) {
     Lo = DAG.getNode(ISD::ADD, dl, NVT, LoOps);
-    Hi = DAG.getNode(ISD::ADD, dl, NVT, ArrayRef(HiOps, 2));
     SDValue Cmp;
     // Special case: X+1 has a carry out if X+1==0. This may reduce the live
     // range of X. We assume comparing with 0 is cheap.
@@ -3521,10 +3520,12 @@ void DAGTypeLegalizer::ExpandIntRes_ADDSUB(SDNode *N,
       Carry = DAG.getSelect(dl, NVT, Cmp, DAG.getConstant(1, dl, NVT),
                              DAG.getConstant(0, dl, NVT));
 
-    if (isAllOnesConstant(LoOps[1]) && isAllOnesConstant(HiOps[1]))
+    if (isAllOnesConstant(LoOps[1]) && isAllOnesConstant(HiOps[1])) {
       Hi = DAG.getNode(ISD::SUB, dl, NVT, HiOps[0], Carry);
-    else
+    } else {
+      Hi = DAG.getNode(ISD::ADD, dl, NVT, ArrayRef(HiOps, 2));
       Hi = DAG.getNode(ISD::ADD, dl, NVT, Hi, Carry);
+    }
   } else {
     Lo = DAG.getNode(ISD::SUB, dl, NVT, LoOps);
     Hi = DAG.getNode(ISD::SUB, dl, NVT, ArrayRef(HiOps, 2));

diff --git a/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/lanai_isel.ll.expected b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/lanai_isel.ll.expected
@@ -12,10 +12,10 @@ define i64 @i64_test(i64 %i) nounwind readnone {
 ; CHECK-NEXT:    t24: i32 = ADD_R t5, t22, TargetConstant:i32<0>
 ; CHECK-NEXT:    t3: i32,ch = LDW_RI<Mem:(load (s32) from %fixed-stack.1, align 8)> TargetFrameIndex:i32<-1>, TargetConstant:i32<0>, TargetConstant:i32<0>, t0
 ; CHECK-NEXT:    t19: i32,ch = LDW_RI<Mem:(dereferenceable load (s32) from %ir.loc, align 8)> TargetFrameIndex:i32<0>, TargetConstant:i32<0>, TargetConstant:i32<0>, t0
-; CHECK-NEXT:    t25: i32 = ADD_R t3, t19, TargetConstant:i32<0>
+; CHECK-NEXT:    t27: i32 = ADD_R t3, t19, TargetConstant:i32<0>
 ; CHECK-NEXT:    t30: i32,glue = SFSUB_F_RR t24, t5
 ; CHECK-NEXT:    t31: i32 = SCC TargetConstant:i32<4>, t30:1
-; CHECK-NEXT:    t28: i32 = ADD_R t25, t31, TargetConstant:i32<0>
+; CHECK-NEXT:    t28: i32 = ADD_R t27, t31, TargetConstant:i32<0>
 ; CHECK-NEXT:    t15: ch,glue = CopyToReg t0, Register:i32 $rv, t28
 ; CHECK-NEXT:    t17: ch,glue = CopyToReg t15, Register:i32 $r9, t24, t15:1
 ; CHECK-NEXT:    t18: ch = RET Register:i32 $rv, Register:i32 $r9, t17, t17:1