[llvm] [AArch64][SME] Remove unused ZA lazy-save (PR #81648)

[Sander de Smalen via llvm-commits]

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@@ -46,13 +47,14 @@ define void @test_lazy_save_2_callees() nounwind "aarch64_inout_za" {
 ; CHECK-NEXT:    mov x29, sp
 ; CHECK-NEXT:    sub sp, sp, #16
 ; CHECK-NEXT:    rdsvl x19, #1
-; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    msub x8, x19, x19, x8
+; CHECK-NEXT:    mov x9, sp
+; CHECK-NEXT:    mul x8, x19, x19
+; CHECK-NEXT:    sub x8, x9, x8
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sdesmalen-arm wrote:

This is an unfortunate regression. If you pass `SVL` to the ExpandZA pseudo, rather than SVL * SVL, you can do the multiply and subtract using MSUB.

https://github.com/llvm/llvm-project/pull/81648