On Mon, Apr 12, 2021 at 4:55 PM Martin Sebor <mse...@gmail.com> wrote:
>
> On 4/12/21 3:53 PM, H.J. Lu via Gcc-patches wrote:
> > On Mon, Apr 12, 2021 at 2:21 AM Richard Biener
> > <richard.guent...@gmail.com> wrote:
> >>
> >> On Sat, Apr 10, 2021 at 5:11 PM H.J. Lu via Gcc-patches
> >> <gcc-patches@gcc.gnu.org> wrote:
> >>>
> >>> Add inline_ignore_target function attribute to inform the compiler that
> >>> target specific option mismatch on functions with the always_inline
> >>> attribute may be ignored. On x86 targets, this attribute can be used on
> >>> integer functions to ignore target non-integer option mismatch.
> >>
> >> I'm not sure I like such attribute but please adjust
> >> default_target_can_inline_p
> >> accordingly (only few targets override this hook).
> >>
> >> Richard.
> >>
> >
> > Like this?
> >
> > Thanks.
>
> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 1ddafb3ff2c..44588566f2d 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -3187,6 +3187,14 @@ int S::interface (int) __attribute__ ((ifunc
> ("_ZN1S8resolverEv")));
> Indirect functions cannot be weak. Binutils version 2.20.1 or higher
> and GNU C Library version 2.11.1 are required to use this feature.
>
> +@item inline_ignore_target
> +@cindex @code{inline_ignore_target} function attribute
> +The @code{inline_ignore_target} attribute on functions is used to
> +inform the compiler that target specific option mismatch on functions
> +with the @code{always_inline} attribute may be ignored. On x86 targets,
> +this attribute can be used on integer functions to ignore target
> +non-integer option mismatch.
> +
> @item interrupt
> @itemx interrupt_handler
> Many GCC back ends support attributes to indicate that a function is
>
> I'm having a hard time understanding the description above (or
> the attribute's name for that matter).
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99744
has a testcase.
> The inline_ignore_target function attribute informs the compiler
> that "target specific option mismatch on functions with the
> @code{always_inline} attribute" may be ignored.
>
> What does "target specific option mismatch" mean? Is it a mismatch
This refers to the message from GCC:
/usr/gcc-11.0.0-x32/lib/gcc/x86_64-pc-linux-gnu/11.0.0/include/ia32intrin.h:112:1:
error: inlining failed in call to ‘always_inline’ ‘__rdtsc’: target
specific option mismatch
112 | __rdtsc (void)
| ^~~~~~~
> between target-specific optimization options added to a function by
> attribute optimize vs other target-specific optimization options of
> the function callers (e.g., added to them by another instance of
> attribue optimize, or by #pragma GCC optimize), into which a function
> with the attribute may be inlined, and where the conflict between
> the two sets of options needs to be reconciled? And if so, should
It is added to support integer functions with always_inline attribute.
Currently x86 integer functions with always_inline attribute fail to
compile when caller has general-regs-only target attribute and
SSE is enabled by default.
> it be provided as a generic attribute for all targets?
Different targets can have different sets of conflict target specific
options.
> Also, what's "integer functions" supposed to mean? Functions that
> return integers?
An integer function can be compiled with -mgeneral-regs-only.
> This new attribute seems sufficiently specialized that I think
> the description ought to be expanded to make it clearer what it's
> for, why it's needed, and when and how to use it. Adding an example
> or two might help, as would using more precise terminology.
>
> Separately, seeing no tests for it in the patch, I wonder how
There are 2 existing tests: gcc.target/i386/pr99744-1.c and
gcc.target/i386/pr99744-2.c. If we want to go with this approach,
I will add inline_ignore_target to all x86 integer intrinsics with
tests.
> the new attribute interacts (or should interact) with other
> attributes or other kinds of functions than the ones it's tested
> with. For example, what happens when the attribute is added to
> a function that's not declared inline, or that's declared with
> the noinline attribute.
>
This attribute should be used together with always_inline attribute.
--
H.J.
