Re: [Valgrind-users] Question about Valgrind tool in Intel new platform

[John R. <jr...@bi...>]

On 4/20/22 05:18, Yang Zhong wrote:

>    The AMX is the NEW feature in Intel new platform and from host, we can
>    find below cpu flags:
> 
>    amx_bf16, amx_tile, amx_int8
> 
>    The SPEC can be found in:
>    https://software.intel.com/content/dam/develop/external/us/en/documents/architecture-instruction-set-extensions-programming-reference.pdf
> 
>    The issue I mentioned should be related with AMX features missed in
>    valgrind emulated CPU. If someone will implement this feature on valgrind,
>    I can help verify. Thanks!

If you really want to help, then start today by collecting and/or writing actual code
that emulates the hardware that implements the feature.  Collect (or find, or write)
the code from Chapter 3, "INTEL® AMX INSTRUCTION SET REFERENCE, A-Z", of that .pdf.
Create actual subroutines and data declarations, and *test* it against your apps.
Put the code into a public repository such as GitHub.

The top-level function should be something like

    unsigned char const *emulate_amx(  // returns next instruction pointer
       unsigned char const *ip,  // pointer to first byte of instruction stream
       unsigned long *general_registers[16],  // hardware state
       unsigned long long *zmm_registers[16],  // zmm (ymm, xmm) registers
       struct Xsave *xsave_area,  // tile registers etc.
       ...
    }

which if successful returns a pointer to the next instruction, else an error code
which is the negative of a small positive integer.

Such code will go a long way towards getting AMX supported by valgrind,
because it will enable valgrind-developers to focus on implementing valgrind
instead of on finding, de-ciphering, and mentally interpreting documentation.