On Wed, Jul 31, 2024 at 10:11:44AM +0200, Uros Bizjak wrote:
> OK. Richard, can you please mention the above in the comment why
> XFmode is rejected in the hook?
>
> Later, we can perhaps benchmark XFmode move vs. generic memory copy to
> get some hard data.
My (limited) understanding was that the hook would be used only for cases
where we'd like to e.g. value number some SF/DF/XF etc. mode loads and some
subsequent loads from the same address with different mode but same size
the same and replace say int or long long later load with VIEW_CONVERT_EXPR
of the result of the SF/SF mode load. That is what was incorrect, because
the load didn't preserve all the bits. The patch would still keep doing
normal SF/DF/XF etc. mode copies if that is all that happens in the program,
load some floating point value and store it elsewhere or as part of larger
aggregate copy.
Jakub
