Re: [PATCH] Mention that some options are turned on by `-Ofast` in their descriptions [PR97263]

[Richard Biener <richard.guenther@gmail.com>]

On Mon, May 6, 2024 at 11:28 PM Andrew Pinski <quic_apinski@quicinc.com> wrote:
>
> Like was done for -ffast-math in r0-105946-ga570fc16fa8056, we should
> document that -Ofast enables -fmath-errno, -funsafe-math-optimizations,
> -finite-math-only, -fno-trapping-math in their documentation.
>
> Note this changes the stronger "must not" to be "is not" for -fno-trapping-math
> since we do enable it for -Ofast already.
>
> OK?

OK

> gcc/ChangeLog:
>
>         PR middle-end/97263
>         * doc/invoke.texi(fmath-errno): Document it is turned on
>         with -Ofast.
>         (funsafe-math-optimizations): Likewise.
>         (ffinite-math-only): Likewise.
>         (fno-trapping-math): Likewise and use less strong language.
>
> Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
> ---
>  gcc/doc/invoke.texi | 41 ++++++++++++++++++++++-------------------
>  1 file changed, 22 insertions(+), 19 deletions(-)
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 9456ced468a..14ff4d25da7 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -14996,11 +14996,12 @@ with a single instruction, e.g., @code{sqrt}.  A program that relies on
>  IEEE exceptions for math error handling may want to use this flag
>  for speed while maintaining IEEE arithmetic compatibility.
>
> -This option is not turned on by any @option{-O} option since
> -it can result in incorrect output for programs that depend on
> -an exact implementation of IEEE or ISO rules/specifications for
> -math functions. It may, however, yield faster code for programs
> -that do not require the guarantees of these specifications.
> +This option is not turned on by any @option{-O} option  besides
> +@option{-Ofast} since it can result in incorrect output for
> +programs that depend on an exact implementation of IEEE or
> +ISO rules/specifications for math functions. It may, however,
> +yield faster code for programs that do not require the guarantees
> +of these specifications.
>
>  The default is @option{-fmath-errno}.
>
> @@ -15017,11 +15018,12 @@ ANSI standards.  When used at link time, it may include libraries
>  or startup files that change the default FPU control word or other
>  similar optimizations.
>
> -This option is not turned on by any @option{-O} option since
> -it can result in incorrect output for programs that depend on
> -an exact implementation of IEEE or ISO rules/specifications for
> -math functions. It may, however, yield faster code for programs
> -that do not require the guarantees of these specifications.
> +This option is not turned on by any @option{-O} option besides
> +@option{-Ofast} since it can result in incorrect output
> +for programs that depend on an exact implementation of IEEE
> +or ISO rules/specifications for math functions. It may, however,
> +yield faster code for programs that do not require the guarantees
> +of these specifications.
>  Enables @option{-fno-signed-zeros}, @option{-fno-trapping-math},
>  @option{-fassociative-math} and @option{-freciprocal-math}.
>
> @@ -15061,11 +15063,12 @@ The default is @option{-fno-reciprocal-math}.
>  Allow optimizations for floating-point arithmetic that assume
>  that arguments and results are not NaNs or +-Infs.
>
> -This option is not turned on by any @option{-O} option since
> -it can result in incorrect output for programs that depend on
> -an exact implementation of IEEE or ISO rules/specifications for
> -math functions. It may, however, yield faster code for programs
> -that do not require the guarantees of these specifications.
> +This option is not turned on by any @option{-O} option besides
> +@option{-Ofast} since it can result in incorrect output
> +for programs that depend on an exact implementation of IEEE or
> +ISO rules/specifications for math functions. It may, however,
> +yield faster code for programs that do not require the guarantees
> +of these specifications.
>
>  The default is @option{-fno-finite-math-only}.
>
> @@ -15089,10 +15092,10 @@ underflow, inexact result and invalid operation.  This option requires
>  that @option{-fno-signaling-nans} be in effect.  Setting this option may
>  allow faster code if one relies on ``non-stop'' IEEE arithmetic, for example.
>
> -This option should never be turned on by any @option{-O} option since
> -it can result in incorrect output for programs that depend on
> -an exact implementation of IEEE or ISO rules/specifications for
> -math functions.
> +This option is not turned on by any @option{-O} option besides
> +@option{-Ofast} since it can result in incorrect output for programs
> +that depend on an exact implementation of IEEE or ISO rules/specifications
> +for math functions.
>
>  The default is @option{-ftrapping-math}.
>
> --
> 2.43.0
>