Re: [PATCH] libgccjit: Fix ira cost segfault

[David Malcolm <dmalcolm@redhat.com>]

On Thu, 2023-11-16 at 17:28 -0500, Antoni Boucher wrote:
> Hi.
> This patch fixes a segfault that happens when compiling librsvg (more
> specifically its dependency aho-corasick) with rustc_codegen_gcc (bug
> 112575).
> I was not able to create a reproducer for this bug: I'm assuming I
> might need to concat all the reproducers together in the same file in
> order to be able to reproduce the issue.

Hi Antoni

Thanks for the patch; sorry for missing it before.

CCing the i386 maintainers; quoting the patch here to give them
context:

> From e0f4f51682266bc9f507afdb64908ed3695a2f5e Mon Sep 17 00:00:00 2001
> From: Antoni Boucher <bouanto@zoho.com>
> Date: Thu, 2 Nov 2023 17:18:35 -0400
> Subject: [PATCH] libgccjit: Fix ira cost segfault
> 
> gcc/ChangeLog:
> 	PR jit/112575
> 	* config/i386/i386-options.cc (ix86_option_override_internal):
> 	Cleanup target_attribute_cache.
> ---
>  gcc/config/i386/i386-options.cc | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-options.cc
> index df7d24352d1..f596c0fb53c 100644
> --- a/gcc/config/i386/i386-options.cc
> +++ b/gcc/config/i386/i386-options.cc
> @@ -3070,6 +3070,12 @@ ix86_option_override_internal (bool main_args_p,
>  	= opts->x_flag_unsafe_math_optimizations;
>        target_option_default_node = target_option_current_node
>          = build_target_option_node (opts, opts_set);
> +      /* TODO: check if this is the correct location.  It should probably be in
> +	 some finalizer function, but I don't
> +	 know if there's one.  */
> +      target_attribute_cache[0] = NULL;
> +      target_attribute_cache[1] = NULL;
> +      target_attribute_cache[2] = NULL;
>      }
>  
>    if (opts->x_flag_cf_protection != CF_NONE)
> -- 
> 2.42.1
> 

Presumably this happens when there's more than one in-process
invocation of the compiler code (via libgccjit).

> 
> I'm also not sure I put the cleanup in the correct location.
> Is there any finalizer function for target specific code?

As you know (but the i386 maintainers might not), to allow multiple in-
process invocations of the compiler code (for libgccjit) we've been
putting code to reset global state in various {filename_cc}_finalize
functions called from toplev::finalize (see the end of toplev.cc).

There doesn't seem to be any kind of hook at this time for calling
target-specific cleanups from toplev::finalize.

However, as of r14-4003-geaa8e8541349df ggc_common_finalize zeroes
everything marked with GTY.  The array target_attribute_cache does have
a GTY marking, so perhaps as of that commit this patch isn't necessary?

Otherwise, if special-casing this is required, sorry: I'm not familiar
enough with i386-options.cc to know if the patch is correct.

> 
> Thanks to fix this issue.

Dave