Hi! On 2024-06-20T14:34:18+0100, Richard Sandiford <richard.sandif...@arm.com> wrote: > This patch adds a combine pass that runs late in the pipeline. > [...]
Nice! > The patch [...] disables the pass by default on i386, rs6000 > and xtensa. Like here: > --- a/gcc/config/i386/i386-options.cc > +++ b/gcc/config/i386/i386-options.cc > @@ -1942,6 +1942,10 @@ ix86_override_options_after_change (void) > flag_cunroll_grow_size = flag_peel_loops || optimize >= 3; > } > > + /* Late combine tends to undo some of the effects of STV and RPAD, > + by combining instructions back to their original form. */ > + if (!OPTION_SET_P (flag_late_combine_instructions)) > + flag_late_combine_instructions = 0; > } ..., I think also here: > --- a/gcc/config/rs6000/rs6000.cc > +++ b/gcc/config/rs6000/rs6000.cc > @@ -4768,6 +4768,14 @@ rs6000_option_override_internal (bool global_init_p) > targetm.expand_builtin_va_start = NULL; > } > > + /* One of the late-combine passes runs after register allocation > + and can match define_insn_and_splits that were previously used > + only before register allocation. Some of those define_insn_and_splits > + use gen_reg_rtx unconditionally. Disable late-combine by default > + until the define_insn_and_splits are fixed. */ > + if (!OPTION_SET_P (flag_late_combine_instructions)) > + flag_late_combine_instructions = 0; > + > rs6000_override_options_after_change (); ..., this needs to be done in 'rs6000_override_options_after_change' instead of 'rs6000_option_override_internal', to address the PRs under discussion. I'm testing such a patch. Grüße Thomas
