[llvm] [LSR] Recognize vscale-relative immediates (PR #88124)

[Paul Walker via llvm-commits]

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@@ -1308,9 +1390,9 @@ void Cost::RateRegister(const Formula &F, const SCEV *Reg,
 
       // If the step size matches the base offset, we could use pre-indexed
       // addressing.
-      if (AMK == TTI::AMK_PreIndexed) {
+      if (AMK == TTI::AMK_PreIndexed && !F.BaseOffset.isScalable()) {
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paulwalker-arm wrote:

I'm suggesting to add the new function because they're not logically equivalent. It's just the "zero" support is incomplete and my worry is that once that's fixed, code like this will silently break.

https://github.com/llvm/llvm-project/pull/88124