[clang] [llvm] [AArch64][SME] Save VG for unwind info when changing streaming-mode (PR #83301)

[Kerry McLaughlin via cfe-commits]

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@@ -214,7 +232,8 @@ declare double @za_shared_callee(double) "aarch64_inout_za"
 define double  @za_new_caller_to_za_shared_callee(double %x) nounwind noinline optnone "aarch64_new_za"{
 ; CHECK-COMMON-LABEL: za_new_caller_to_za_shared_callee:
 ; CHECK-COMMON:       // %bb.0: // %prelude
-; CHECK-COMMON-NEXT:    stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
+; CHECK-COMMON-NEXT:    stp x29, x30, [sp, #-32]! // 16-byte Folded Spill
+; CHECK-COMMON-NEXT:    str x19, [sp, #16] // 8-byte Folded Spill
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kmclaughlin-arm wrote:

The base pointer x19 is added to the list of saved registers in `determineCalleeSaves` if the function is in streaming mode or has SVE. The spill was introduced here when I enabled SVE for this test.

https://github.com/llvm/llvm-project/pull/83301