On Tue, Jul 23, 2024 at 10:07 AM Sam James <s...@gentoo.org> wrote:
>
> At -O1, the intention is that we compile things in a "reasonable" amount
> of time (ditto memory use). In particular, we try to especially avoid
> optimizations which scale poorly on pathological cases, as is the case
> for large machine-generated code.
>
> Recommend -O1 for large machine-generated code, as has been informally
> done on bugs for a while now.
>
> This applies (broadly speaking) for both large machine-generated functions
> but also to a lesser extent repetitive small-but-still-not-tiny functions
> from a generator program.
>
> gcc/ChangeLog:
> PR middle-end/114855
> * doc/invoke.texi (Optimize options): Mention machine-generated
> code for -O1.
> ---
> richi, does this accurately reflect the discussion we had on IRC a little
> while ago?
>
> Please push if OK, thanks.
>
> gcc/doc/invoke.texi | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index e0a641213ae4..9fb0925ed292 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -12560,6 +12560,11 @@ With @option{-O}, the compiler tries to reduce code
> size and execution
> time, without performing any optimizations that take a great deal of
> compilation time.
>
> +@option{-O} is the recommended optimization level for large machine-generated
> +code as a sensible balance between time taken to compile and memory use:
> +higher optimization levels perform optimizations with greater algorithmic
> +complexity than at @option{-O}.
> +
Personally, I get confused when "-O1" is written as just "-O"...
> @c Note that in addition to the default_options_table list in opts.cc,
> @c several optimization flags default to true but control optimization
> @c passes that are explicitly disabled at -O0.
>
> --
> 2.45.2
>
