[llvm] [polly] [SCEV] Refactor SCEV flags, in preparation to extend (NFC) (PR #225179)

[David Sherwood via llvm-commits]

================
@@ -427,7 +422,7 @@ class SCEVMinMaxExpr : public SCEVCommutativeExpr {
       : SCEVCommutativeExpr(ID, T, O, N, O[0]->getType()) {
     assert(isMinMaxType(T));
     // Min and max never overflow
-    setNoWrapFlags(FlagNUW | FlagNSW);
+    setFlags(FlagNUW | FlagNSW);
----------------
david-arm wrote:

Is there any value in keeping a `setNoWrapFlags` interface that would let you only override the wrap-flags bitfield and leave the other flags (e.g. exact) as is? Otherwise for cases like this you'd have to or this with existing flags, i.e.

```
  setFlags(FlagNUW | FlagNSW | getOtherFlags());
```

Keeping the `setNoWrapFlags` interface would also reduce the diff. What do you think?

https://github.com/llvm/llvm-project/pull/225179