[llvm] [SCEV] Split collecting and applying rewrite info from loop guards (NFC) (PR #97316)

[Nikita Popov via llvm-commits]

================
@@ -1299,8 +1299,26 @@ class ScalarEvolution {
   /// sharpen it.
   void setNoWrapFlags(SCEVAddRecExpr *AddRec, SCEV::NoWrapFlags Flags);
 
+  class LoopGuards {
+    DenseMap<const SCEV *, const SCEV *> RewriteMap;
+    bool PreserveNUW = false;
+    bool PreserveNSW = false;
+    ScalarEvolution &SE;
+
+    LoopGuards(ScalarEvolution &SE) : SE(SE) {}
+
+  public:
+    /// Collect rewrite map for loop guards for loop \p L, together with flags
+    /// indidcating if NUW and NSW can be preserved during rewriting.
----------------
nikic wrote:

```suggestion
    /// indidcating if NUW and NSW can be preserved during rewriting.
```
```suggestion
    /// indicating if NUW and NSW can be preserved during rewriting.
```

https://github.com/llvm/llvm-project/pull/97316