[AArch64] Do not abort if overflow check does not use EQ or NE.

[jgalenson]

Summary

As suggested by Eli Friedman, instead of aborting if an overflow check uses something other than SETEQ or SETNE, simply do not apply the optimization.

[efriedma]

LGTM. (I'm pretty sure it's possible to come up with a testcase, but it's not worth the time to figure out what exact legalization sequence would trigger this.)

[jgalenson]

Thanks. Could you commit this for me?

lib/Target/AArch64/AArch64ISelLowering.cpp

if (LHS.getValueType() == MVT::f128) {
     if (!RHS.getNode()) {
       RHS = DAG.getConstant(0, dl, LHS.getValueType());
       CC = ISD::SETNE;
     }
   }
 
   // Optimize {s|u}{add|sub|mul}.with.overflow feeding into a branch
   // instruction.
-  if (isOverflowIntrOpRes(LHS) && isOneConstant(RHS)) {
-    assert((CC == ISD::SETEQ || CC == ISD::SETNE) &&
-           "Unexpected condition code.");
+  if (isOverflowIntrOpRes(LHS) && isOneConstant(RHS) &&
+      (CC == ISD::SETEQ || CC == ISD::SETNE)) {
     // Only lower legal XALUO ops.
     if (!DAG.getTargetLoweringInfo().isTypeLegal(LHS->getValueType(0)))
       return SDValue();
 
     // The actual operation with overflow check.
     AArch64CC::CondCode OFCC;
     SDValue Value, Overflow;
     std::tie(Value, Overflow) = getAArch64XALUOOp(OFCC, LHS.getValue(0), DAG);