Re: Broadcom BCM2709, ARMv8, and missing CPU features

[Jeffrey Walton <noloader@gmail.com>]

On Thu, Jul 28, 2016 at 3:06 AM, Tixy <tixy@yxit.co.uk> wrote:
> On Thu, 2016-07-28 at 02:38 -0400, Jeffrey Walton wrote:
> [...]
>> >>     // AES (aese)
>> >>     ".byte 0x4e, 0x28, 0x48, 0x20;\n"
>> >
>> > So as instructions are little-endian that's 0x2048284e for a 32-bit
>> > instruction, or 0x284e2048 if it's a Thumb2 instruction (I'm showing
>> > that the same way as the ARM ARM does).
>>
>> I pulled the encodings from a known good machine that used intrinsics.
>> I did not hand encode them (too much work).
>>
>> > According to my copy of the ARM ARM, the AESE instruction has these
>> > encodings:
>> >
>> > For Thumb:
>> >
>> > 1 1 1 1 1 1 1 1 1 D 1 1 size 0 0 Vd 0 0 1 1 0 0 M 0 Vm
>> >
>> > For ARM
>> >
>> > 1 1 1 1 0 0 1 1 1 D 1 1 size 0 0 Vd 0 0 1 1 0 0 M 0 Vm
>> >
>> > For AArch64
>> >
>> > 0 1 0 0 1 1 1 0 size 1 0 1 0 0 0 0 1 0 0 1 0 Rn Rd
>> >
>> > So it looks like you've used the AArch64 encoding (for something
>> > compiled and presumably run as AArch32?!) and gotten the byte order the
>> > wrong way around.
>>
>> I'm not sure if it matters, but this is an ARMv8 device running a 32-bit OS.
>
> So it's running in AArch32 mode, and you want the encodings for that,
> not the AArch64 version. I.e. the second encoding I mentioned, which
> would be
>
> .inst 0xf3b00300

OK, thanks. I *think* what may have happened is the disassembly
occurred on host machine, not the target machine.

> or better, find a compiler version and options that knows about the
> instructions you want to test (which I see you already asked about
> below). Sorry I can't help with that, I know little about toolchains,
> and have also never used the newer ARM instruction features like VFP,
> SIMD, crytpo etc.

Yeah, this is quite painful at the moment. I think there's a
disconnect between what's advertised to work, and what works in
practice.

Let me see if GCC 6.0 is available; or if Clang has better success.
I'm doing my best to avoid building GCC myself. I have very bad
memories from that experience.

Jeff