Re: [Qemu-devel] [PATCH 26/60] AArch64: Add ADR instruction emulation

[Peter Maydell]

On 19 November 2013 18:03, Peter Maydell <address@hidden> wrote:
> On 19 November 2013 17:52, Claudio Fontana <address@hidden> wrote:
>> static void disas_pc_rel_adr(DisasContext *s, uint32_t insn)
>> {
>>     /*
>>      * 31 30 29 28 27 26 25 24 23     5 4  0
>>      * op immlo  1  0  0  0  0   immhi   Rd
>>      */
>>     unsigned int page, imm, rd, len; /* op -> page, immhi:immlo -> imm */
>>     uint64_t base;
>>     sint64_t offset; /* SignExtend(imm) -> offset */
>>
>>     page = insn & (1 << 31) ? 1 : 0;
>>     imm = extract32(insn, 29, 2) + extract32(insn, 5, 19) << 2;
>>     rd = extract32(insn, 0, 5);
>
> Claiming you want sign extension and not using sextract32()
> is a bit odd.

...to be a bit more specific, you can get the immediate
into a signed 64 bit variable like this:

      int64_t imm = (sextract32(insn, 5, 19) << 2)
          | extract32(insn, 29, 2);
      if (page) {
          imm <<= 12;
      }

which is exactly what Alex's original patch does, except
it's not using the standard sextract/extract functions
(probably because they weren't in master at the point he
wrote it).

thanks
-- PMM