https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124901
Drea Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |pinskia at gcc dot gnu.org
--- Comment #9 from Drea Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Uroš Bizjak from comment #8)
> FTR: Adding *another* pass_cprop_hardreg after pass_reorder_blocks with:
>
> --cut here--
> diff --git a/gcc/passes.def b/gcc/passes.def
> index cdddb87302f..b5c6e99974b 100644
> --- a/gcc/passes.def
> +++ b/gcc/passes.def
> @@ -543,6 +543,7 @@ along with GCC; see the file COPYING3. If not see
> NEXT_PASS (pass_cprop_hardreg);
> NEXT_PASS (pass_fast_rtl_dce);
> NEXT_PASS (pass_reorder_blocks);
> + NEXT_PASS (pass_cprop_hardreg);
> NEXT_PASS (pass_leaf_regs);
> NEXT_PASS (pass_split_before_sched2);
> NEXT_PASS (pass_sched2);
> diff --git a/gcc/regcprop.cc b/gcc/regcprop.cc
> index 2a9956353cc..806dc944b97 100644
> --- a/gcc/regcprop.cc
> +++ b/gcc/regcprop.cc
> @@ -1358,6 +1358,7 @@ public:
> {}
>
> /* opt_pass methods: */
> + opt_pass *clone () override { return new pass_cprop_hardreg (m_ctxt); }
> bool gate (function *) final override
> {
> return (optimize > 0 && (flag_cprop_registers));
> --cut here--
>
> also shows some code size improvements with x86_64 default linux kernel:
>
> $ size *.o
> text data bss dec hex filename
> 29378531 4929075 744820 35052426 216db8a vmlinux-add.o
> 29382751 4929075 744820 35056646 216ec06 vmlinux-baseline.o
> 29384459 4929075 744820 35058354 216f2b2 vmlinux-moved.o
>
> where vmlinux-baseline.o is compiled with vanilla GCC, vmlinux-add.o is
> compiled with additional pass_cprop_hardreg after pass_reorder_blocks, and
> vmlinux-moved.o is compiled with pass_cprop_hardreg moved from its current
> position to after pass_reorder_blocks.
>
> The code size changes are:
>
> vmlinux-moved.o: +1708 bytes
> vmlinux-add.o : -4220 bytes
>
> So, it looks there is some benefit by adding another pass_cprop_hardreg
> after pass_reorder_blocks.
Maybe only enabling this pass at -O2+ and not for -Os (because bb reorder for
-Os should not be duplicating the bb).
