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Re: [PATCH V2 0/2] Split tdesc_(amd64|i386)_mpx into tdesc(amd64|i386)_mpx_* and tdesc(amd64|i386)_avx_mpx_*
- From: Pedro Alves <palves at redhat dot com>
- To: Yao Qi <qiyaoltc at gmail dot com>, Walfred Tedeschi <walfred dot tedeschi at intel dot com>
- Cc: brobecker at adacore dot com, gdb-patches at sourceware dot org
- Date: Thu, 14 Apr 2016 12:33:45 +0100
- Subject: Re: [PATCH V2 0/2] Split tdesc_(amd64|i386)_mpx into tdesc(amd64|i386)_mpx_* and tdesc(amd64|i386)_avx_mpx_*
- Authentication-results: sourceware.org; auth=none
- References: <1457025942-23711-1-git-send-email-walfred dot tedeschi at intel dot com> <864mb4mqkm dot fsf at gmail dot com>
On 04/14/2016 11:29 AM, Yao Qi wrote:
> Walfred Tedeschi <email@example.com> writes:
>> CPU features can occur in any combination. The current assumption that
>> feature "A" implies in feature "B" does not necessarily hold.
>> This patch series construct an additional combination of the Intel(R)
>> Memory Protection Extensions (MPX) with Intel(R) Advanced Vector
>> Extensions (AVX).
> First of all, I am not against your patches. Just think a little more
> after reading them...
> This reveals a problem in gdb target description. It doesn't scale very
> well if processors have multiple different features, and features can be
> combined differently. A processor family has three features A, B, and
> C, and each processor implementation may have one, two or three of these
> features. In gdb target description, we need to have many *.xml and *.c
> files, for these combinations like, A, B, C, AB, AC, BC, and ABC.
> The root cause is that target description are static and pre-generated.
> If the target description can be generated dynamically according to the
> cpuid or AT_HWCAP, that would be simpler. In this way, we only have to
> define target descriptions for feature A, B, and C, and GDB/GDBserver
> combine them together in the runtime.
I agree. This is not the first time this is suggested. If someone were
to do it, I'd be in favor too.