[compiler-rt] [Compiler-rt] Add AArch64 routines for __arm_agnostic("sme_za_state") (PR #120059)

[Kerry McLaughlin via llvm-commits]

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@@ -204,6 +206,161 @@ DEFINE_COMPILERRT_FUNCTION(__arm_get_current_vg)
   ret
 END_COMPILERRT_FUNCTION(__arm_get_current_vg)
 
+DEFINE_COMPILERRT_FUNCTION(__arm_sme_state_size)
+  .variant_pcs __arm_sme_state_size
+  BTI_C
+
+  // Test if SME is available and PSTATE = 1.
+  adrp    x16, CPU_FEATS_SYMBOL
+  ldr     x16, [x16, CPU_FEATS_SYMBOL_OFFSET]
+  tbz     x16, #FEAT_SME_BIT, 0f
+  mrs     x16, SVCR
+  tbz     x16, #1, 0f
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kmclaughlin-arm wrote:

Does this routine also need to check that TPIDR2_EL0 is null?

https://github.com/llvm/llvm-project/pull/120059