[SelectionDAG] Fixup type usage of CondCodeAction table (#116082)

Ensure that all uses of CondCodeAction table are checking the compared
types, not the produced type. This is a prerequisite to landing #115035

Author: AlexMaclean

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -1618,13 +1618,14 @@ class TargetLoweringBase {
     return Action;
   }
 
-  /// Return true if the specified condition code is legal on this target.
+  /// Return true if the specified condition code is legal for a comparison of
+  /// the specified types on this target.
   bool isCondCodeLegal(ISD::CondCode CC, MVT VT) const {
     return getCondCodeAction(CC, VT) == Legal;
   }
 
-  /// Return true if the specified condition code is legal or custom on this
-  /// target.
+  /// Return true if the specified condition code is legal or custom for a
+  /// comparison of the specified types on this target.
   bool isCondCodeLegalOrCustom(ISD::CondCode CC, MVT VT) const {
     return getCondCodeAction(CC, VT) == Legal ||
            getCondCodeAction(CC, VT) == Custom;

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -4975,7 +4975,7 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
         APInt C = C1 - 1;
         ISD::CondCode NewCC = (Cond == ISD::SETGE) ? ISD::SETGT : ISD::SETUGT;
         if ((DCI.isBeforeLegalizeOps() ||
-             isCondCodeLegal(NewCC, VT.getSimpleVT())) &&
+             isCondCodeLegal(NewCC, OpVT.getSimpleVT())) &&
             (!N1C->isOpaque() || (C.getBitWidth() <= 64 &&
                                   isLegalICmpImmediate(C.getSExtValue())))) {
           return DAG.getSetCC(dl, VT, N0,
@@ -4995,7 +4995,7 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
         APInt C = C1 + 1;
         ISD::CondCode NewCC = (Cond == ISD::SETLE) ? ISD::SETLT : ISD::SETULT;
         if ((DCI.isBeforeLegalizeOps() ||
-             isCondCodeLegal(NewCC, VT.getSimpleVT())) &&
+             isCondCodeLegal(NewCC, OpVT.getSimpleVT())) &&
             (!N1C->isOpaque() || (C.getBitWidth() <= 64 &&
                                   isLegalICmpImmediate(C.getSExtValue())))) {
           return DAG.getSetCC(dl, VT, N0,