Re: [PATCH] LoongArch: Set 4 * (issue rate) as the default for -falign-functions and -falign-loops

[Xi Ruoyao <xry111@xry111.site>]

On Tue, 2023-04-18 at 21:06 +0800, Lulu Cheng wrote:
> Hi, ruoyao:
> 
> Thank you so much for making this submission. But we are testing the 
> impact of these two alignment parameters
> 
> (also including -falign-jumps and -falign-lables ) on performance. So 
> before the result comes out, this patch will
> 
> not be merged into the main branch for the time being.

Ok, I'll wait for the result.

> 
> Thanks!
> 
> 在 2023/4/18 下午8:17, Xi Ruoyao 写道:
> > According to Xuerui's LLVM changeset [1], doing so can make a
> > significant performace gain.
> > 
> > Bootstrapped and regtested on loongarch64-linux-gnu.  Ok for GCC 14?
> > 
> > [1]:https://reviews.llvm.org/D148622
> > 
> > gcc/ChangeLog:
> > 
> >         * config/loongarch/loongarch.cc
> >         (loongarch_option_override_internal): If -falign-functions
> > is
> >         used but the alignment is not explicitly specified, set it
> > to
> >         4 * loongarch_issue_rate ().  Likewise for -falign-loops.
> > ---
> >   gcc/config/loongarch/loongarch.cc | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> > 
> > diff --git a/gcc/config/loongarch/loongarch.cc
> > b/gcc/config/loongarch/loongarch.cc
> > index 06fc1cd0604..6552484de7c 100644
> > --- a/gcc/config/loongarch/loongarch.cc
> > +++ b/gcc/config/loongarch/loongarch.cc
> > @@ -6236,6 +6236,17 @@ loongarch_option_override_internal (struct
> > gcc_options *opts)
> >         && !opts->x_optimize_size)
> >       opts->x_flag_prefetch_loop_arrays = 1;
> >   
> > +  /* Align functions and loops to (issue rate) * (insn size) to
> > improve
> > +     the throughput of the fetching units.  */
> > +  char *align = XNEWVEC (char, 16);
> > +  sprintf (align, "%d", loongarch_issue_rate () * 4);
> > +
> > +  if (opts->x_flag_align_functions && !opts->x_str_align_functions)
> > +    opts->x_str_align_functions = align;
> > +
> > +  if (opts->x_flag_align_loops && !opts->x_str_align_loops)
> > +    opts->x_str_align_loops = align;
> > +
> >     if (TARGET_DIRECT_EXTERN_ACCESS && flag_shlib)
> >       error ("%qs cannot be used for compiling a shared library",
> >            "-mdirect-extern-access");
> 

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University