aarch64: Failure to handle PSTATE.SM & ZA for tlsdesc calls

[pinskia]

Turns out LLVM has the same issue as GCC here (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121415).
For:

extern __thread int x;
int f() __arm_streaming_compatible { return x; }

compiled with -O2 -fPIC, we get:

f():                                  // @f()
        .cfi_startproc
// %bb.0:
        stp     x29, x30, [sp, #-16]!           // 16-byte Folded Spill
        .cfi_def_cfa_offset 16
        mov     x29, sp
        .cfi_def_cfa w29, 16
        .cfi_offset w30, -8
        .cfi_offset w29, -16
        adrp    x0, :tlsdesc:x
        ldr     x1, [x0, :tlsdesc_lo12:x]
        add     x0, x0, :tlsdesc_lo12:x
        .tlsdesccall x
        blr     x1
        mrs     x8, TPIDR_EL0
        ldr     w0, [x8, x0]
        .cfi_def_cfa wsp, 16
        ldp     x29, x30, [sp], #16             // 16-byte Folded Reload
        .cfi_def_cfa_offset 0
        .cfi_restore w30
        .cfi_restore w29
        ret

which fails to force non-streaming mode around the call. A function with ZA or ZT0 state would also need to handle that.

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: Andrew Pinski (pinskia)

Turns out LLVM has the same issue as GCC here (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121415). For: ``` extern __thread int x; int f() __arm_streaming_compatible { return x; } ``` compiled with -O2 -fPIC, we get: ``` f(): // @f() .cfi_startproc // %bb.0: stp x29, x30, [sp, #-16]! // 16-byte Folded Spill .cfi_def_cfa_offset 16 mov x29, sp .cfi_def_cfa w29, 16 .cfi_offset w30, -8 .cfi_offset w29, -16 adrp x0, :tlsdesc:x ldr x1, [x0, :tlsdesc_lo12:x] add x0, x0, :tlsdesc_lo12:x .tlsdesccall x blr x1 mrs x8, TPIDR_EL0 ldr w0, [x8, x0] .cfi_def_cfa wsp, 16 ldp x29, x30, [sp], #16 // 16-byte Folded Reload .cfi_def_cfa_offset 0 .cfi_restore w30 .cfi_restore w29 ret ``` which fails to force non-streaming mode around the call. A function with ZA or ZT0 state would also need to handle that.

[efriedma-quic]

CC @MacDue

[MacDue]

Thanks for the ping, I'll take a look at this tomorrow.