[llvm] [AArch64] Disable FastISel/GlobalISel for ZT0 state (PR #82768)

[Kerry McLaughlin via llvm-commits]

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@@ -447,3 +447,64 @@ define float @frem_call_sm_compat(float %a, float %b) "aarch64_pstate_sm_compati
   %res = frem float %a, %b
   ret float %res
 }
+
+;
+; Check ZT0 State
+;
+
+declare double @zt0_shared_callee(double) "aarch64_inout_zt0"
+
+define double  @zt0_new_caller_to_zt0_shared_callee(double %x) nounwind noinline optnone "aarch64_new_zt0" {
+; CHECK-COMMON-LABEL: zt0_new_caller_to_zt0_shared_callee:
+; CHECK-COMMON:       // %bb.0: // %prelude
+; CHECK-COMMON-NEXT:    sub sp, sp, #80
+; CHECK-COMMON-NEXT:    str x30, [sp, #64] // 8-byte Folded Spill
+; CHECK-COMMON-NEXT:    mrs x8, TPIDR2_EL0
+; CHECK-COMMON-NEXT:    cbz x8, .LBB13_2
+; CHECK-COMMON-NEXT:    b .LBB13_1
+; CHECK-COMMON-NEXT:  .LBB13_1: // %save.za
+; CHECK-COMMON-NEXT:    mov x8, sp
+; CHECK-COMMON-NEXT:    str zt0, [x8]
+; CHECK-COMMON-NEXT:    bl __arm_tpidr2_save
+; CHECK-COMMON-NEXT:    ldr zt0, [x8]
+; CHECK-COMMON-NEXT:    msr TPIDR2_EL0, xzr
+; CHECK-COMMON-NEXT:    b .LBB13_2
+; CHECK-COMMON-NEXT:  .LBB13_2: // %entry
+; CHECK-COMMON-NEXT:    smstart za
+; CHECK-COMMON-NEXT:    zero { zt0 }
+; CHECK-COMMON-NEXT:    bl zt0_shared_callee
+; CHECK-COMMON-NEXT:    mov x8, #4631107791820423168 // =0x4045000000000000
+; CHECK-COMMON-NEXT:    fmov d1, x8
+; CHECK-COMMON-NEXT:    fadd d0, d0, d1
+; CHECK-COMMON-NEXT:    smstop za
+; CHECK-COMMON-NEXT:    ldr x30, [sp, #64] // 8-byte Folded Reload
+; CHECK-COMMON-NEXT:    add sp, sp, #80
+; CHECK-COMMON-NEXT:    ret
+entry:
+  %call = call double @zt0_shared_callee(double %x)
+  %add = fadd double %call, 4.200000e+01
+  ret double %add;
+}
+
+define double  @zt0_new_caller_to_normal_callee(double %x) nounwind noinline optnone "aarch64_inout_zt0" {
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kmclaughlin-arm wrote:

Should this be called `zt0_shared_caller_to_normal_callee` since the caller has the `inout` attribute?

https://github.com/llvm/llvm-project/pull/82768