Re: [PATCH] IPA: support -flto + -flive-patching=inline-clone

[Qing Zhao <qing.zhao@oracle.com>]

Hi, Martin:


I have two questions on this:

1.  What’s the motivation to enable -flive-patching with -flto? Is there any application that will try -flive-patching with -flto now?

2. Why only enable -flive-patching=inline-clone with -flto?

thanks.

Qing

> On Oct 5, 2022, at 7:41 AM, Martin Liška <mliska@suse.cz> wrote:
> 
> There's no fundamental reason why -flive-patching=inline-clone can't
> coexist with -flto. Yes, one can theoretically have many more clone
> function that includes a live patch. It is pretty much the same
> as in-module inlining.
> 
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> 
> Ready to be installed?
> Thanks,
> Martin
> 
> gcc/ChangeLog:
> 
> 	* opts.cc (finish_options): Print sorry message only
> 	for -flive-patching=inline-only-static.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.dg/live-patching-2.c: Update scanned pattern.
> 	* gcc.dg/live-patching-5.c: New test.
> ---
> gcc/opts.cc                            | 5 +++--
> gcc/testsuite/gcc.dg/live-patching-2.c | 4 ++--
> gcc/testsuite/gcc.dg/live-patching-5.c | 8 ++++++++
> 3 files changed, 13 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/live-patching-5.c
> 
> diff --git a/gcc/opts.cc b/gcc/opts.cc
> index eb5db01de17..ae079fcd20e 100644
> --- a/gcc/opts.cc
> +++ b/gcc/opts.cc
> @@ -1288,8 +1288,9 @@ finish_options (struct gcc_options *opts, struct gcc_options *opts_set,
> 	   "%<-fsanitize=kernel-address%>");
> 
>   /* Currently live patching is not support for LTO.  */
> -  if (opts->x_flag_live_patching && opts->x_flag_lto)
> -    sorry ("live patching is not supported with LTO");
> +  if (opts->x_flag_live_patching == LIVE_PATCHING_INLINE_ONLY_STATIC && opts->x_flag_lto)
> +    sorry ("live patching (with %qs) is not supported with LTO",
> +	   "inline-only-static");
> 
>   /* Currently vtable verification is not supported for LTO */
>   if (opts->x_flag_vtable_verify && opts->x_flag_lto)
> diff --git a/gcc/testsuite/gcc.dg/live-patching-2.c b/gcc/testsuite/gcc.dg/live-patching-2.c
> index 0dde4e9e0c0..1c4f9229b82 100644
> --- a/gcc/testsuite/gcc.dg/live-patching-2.c
> +++ b/gcc/testsuite/gcc.dg/live-patching-2.c
> @@ -1,10 +1,10 @@
> /* { dg-do compile } */
> /* { dg-require-effective-target lto } */
> -/* { dg-options "-O2 -flive-patching -flto" } */
> +/* { dg-options "-O2 -flive-patching=inline-only-static -flto" } */
> 
> int main()
> {
>   return 0;
> }
> 
> -/* { dg-message "sorry, unimplemented: live patching is not supported with LTO" "-flive-patching and -flto together" { target *-*-* } 0 } */
> +/* { dg-message "sorry, unimplemented: live patching \\(with 'inline-only-static'\\) is not supported with LTO" "-flive-patching and -flto together" { target *-*-* } 0 } */
> diff --git a/gcc/testsuite/gcc.dg/live-patching-5.c b/gcc/testsuite/gcc.dg/live-patching-5.c
> new file mode 100644
> index 00000000000..098047a36cd
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/live-patching-5.c
> @@ -0,0 +1,8 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target lto } */
> +/* { dg-options "-O2 -flive-patching -flto" } */
> +
> +int main()
> +{
> +  return 0;
> +}
> -- 
> 2.37.3
>