Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses

[Richard Henderson]

On 04/08/2016 05:29 PM, Thomas Hanson wrote:
> Looking at tcg_out_tlb_load():
> If I'm reading the pseudo-assembler of the function names correctly, it looks
> like in the i386 code we're already masking the address being checked:
>      tgen_arithi(s, ARITH_AND + trexw, r1, TARGET_PAGE_MASK | (aligned ? s_mask
> : 0), 0);
> where  TARGET_PAGE_MASK is a simple all-1's mask in the appropriate upper bits.
>
> Can we just poke some 0's into that mask in the tag locations?

No, because we'd no longer have a sign-extended 32-bit value, as fits in that 
immediate operand field.  To load the constant you're asking for, we'd need a 
64-bit move insn and another register.


r~