[llvm] [AArch64][CodeGen] Add patterns for small negative VScale const (PR #89607)

[Paul Walker via llvm-commits]

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@@ -2583,6 +2583,27 @@ let Predicates = [HasSVEorSME] in {
                                sub_32)>;
   }
 
+  // Add NoUseScalarIncVL to avoid affecting for patterns with UseScalarIncVL
+  let Predicates = [NoUseScalarIncVL] in {
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paulwalker-arm wrote:

This will replace the predicate and thus lose the original feature flag protection.  You likely want `[HasSVEorSME, NoUseScalarIncVL]`.

Also, please can you place the new block directly below the block that implements the negated patterns (i.e. the one with `SUBXrs XZR`) because they're related and better show why these new patterns exist.

https://github.com/llvm/llvm-project/pull/89607