> -----Original Message-----
> From: Wang, Hongyu <hongyu.w...@intel.com>
> Sent: Saturday, November 19, 2022 2:26 PM
> To: gcc-patches@gcc.gnu.org
> Cc: richard.guent...@gmail.com; ubiz...@gmail.com; Liu, Hongtao
> <hongtao....@intel.com>
> Subject: [PATCH] i386: Only enable small loop unrolling in backend [PR 107602]
>
> Hi,
>
> Followed by the discussion in pr107602, -munroll-only-small-loops Does not
PR107692?
> turns on/off -funroll-loops, and current check in pass_rtl_unroll_loops::gate
> would cause -funroll-loops do not take effect. Revert the change about
> targetm.loop_unroll_adjust and apply the backend option change to strictly
> follow the rule that -funroll-loops takes full control of loop unrolling, and
> munroll-only-small-loops just change its behavior to unroll small size loops.
>
> Bootstrapped and regtested on x86-64-pc-linux-gnu.
>
> Ok for trunk?
>
> gcc/ChangeLog:
>
> PR target/107602
> * common/config/i386/i386-common.cc (ix86_optimization_table):
> Enable loop unroll O2, disable -fweb and -frename-registers
> by default.
> * config/i386/i386-options.cc
> (ix86_override_options_after_change):
> Disable small loop unroll when funroll-loops enabled, reset
> cunroll_grow_size when it is not explicitly enabled.
> (ix86_option_override_internal): Call
> ix86_override_options_after_change instead of calling
> ix86_recompute_optlev_based_flags and ix86_default_align
> separately.
> * config/i386/i386.cc (ix86_loop_unroll_adjust): Adjust unroll
> factor if -munroll-only-small-loops enabled.
> * loop-init.cc (pass_rtl_unroll_loops::gate): Do not enable
> loop unrolling for -O2-speed.
> (pass_rtl_unroll_loops::execute): Rmove
> targetm.loop_unroll_adjust check.
>
> gcc/testsuite/ChangeLog:
>
> PR target/107602
> * gcc.target/i386/pr86270.c: Add -fno-unroll-loops.
> * gcc.target/i386/pr93002.c: Likewise.
> ---
> gcc/common/config/i386/i386-common.cc | 8 ++++++
> gcc/config/i386/i386-options.cc | 34 ++++++++++++++++++++++---
> gcc/config/i386/i386.cc | 18 ++++---------
> gcc/loop-init.cc | 11 +++-----
> gcc/testsuite/gcc.target/i386/pr86270.c | 2 +-
> gcc/testsuite/gcc.target/i386/pr93002.c | 2 +-
> 6 files changed, 49 insertions(+), 26 deletions(-)
>
> diff --git a/gcc/common/config/i386/i386-common.cc
> b/gcc/common/config/i386/i386-common.cc
> index 6ce2a588adc..660a977b68b 100644
> --- a/gcc/common/config/i386/i386-common.cc
> +++ b/gcc/common/config/i386/i386-common.cc
> @@ -1808,7 +1808,15 @@ static const struct default_options
> ix86_option_optimization_table[] =
> /* The STC algorithm produces the smallest code at -Os, for x86. */
> { OPT_LEVELS_2_PLUS, OPT_freorder_blocks_algorithm_, NULL,
> REORDER_BLOCKS_ALGORITHM_STC },
> +
> + /* Turn on -funroll-loops with -munroll-only-small-loops to enable small
> + loop unrolling at -O2. */
> + { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_funroll_loops, NULL, 1 },
> { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_munroll_only_small_loops, NULL,
> 1 },
> + /* Turns off -frename-registers and -fweb which are enabled by
> + funroll-loops. */
> + { OPT_LEVELS_ALL, OPT_frename_registers, NULL, 0 },
> + { OPT_LEVELS_ALL, OPT_fweb, NULL, 0 },
> /* Turn off -fschedule-insns by default. It tends to make the
> problem with not enough registers even worse. */
> { OPT_LEVELS_ALL, OPT_fschedule_insns, NULL, 0 }, diff --git
> a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-options.cc index
> e5c77f3a84d..bc1d36e36a8 100644
> --- a/gcc/config/i386/i386-options.cc
> +++ b/gcc/config/i386/i386-options.cc
> @@ -1838,8 +1838,37 @@ ix86_recompute_optlev_based_flags (struct
> gcc_options *opts, void ix86_override_options_after_change (void) {
> + /* Default align_* from the processor table. */
> ix86_default_align (&global_options);
> +
> ix86_recompute_optlev_based_flags (&global_options, &global_options_set);
> +
> + /* Disable unrolling small loops when there's explicit
> + -f{,no}unroll-loop. */
> + if ((OPTION_SET_P (flag_unroll_loops))
> + || (OPTION_SET_P (flag_unroll_all_loops)
> + && flag_unroll_all_loops))
> + {
> + if (!OPTION_SET_P (ix86_unroll_only_small_loops))
> + ix86_unroll_only_small_loops = 0;
> + /* Re-enable -frename-registers and -fweb if funroll-loops
> + enabled. */
> + if (!OPTION_SET_P (flag_web))
> + flag_web = flag_unroll_loops;
> + if (!OPTION_SET_P (flag_rename_registers))
> + flag_rename_registers = flag_unroll_loops;
> + /* -fcunroll-grow-size default follws -f[no]-unroll-loops. */
> + if (!OPTION_SET_P (flag_cunroll_grow_size))
> + flag_cunroll_grow_size = flag_unroll_loops
> + || flag_peel_loops
> + || optimize >= 3;
> + }
> + else
> + {
> + if (!OPTION_SET_P (flag_cunroll_grow_size))
> + flag_cunroll_grow_size = flag_peel_loops || optimize >= 3;
> + }
> +
> }
>
> /* Clear stack slot assignments remembered from previous functions.
> @@ -2351,7 +2380,7 @@ ix86_option_override_internal (bool main_args_p,
>
> set_ix86_tune_features (opts, ix86_tune, opts->x_ix86_dump_tunes);
>
> - ix86_recompute_optlev_based_flags (opts, opts_set);
> + ix86_override_options_after_change ();
>
> ix86_tune_cost = processor_cost_table[ix86_tune];
> /* TODO: ix86_cost should be chosen at instruction or function granuality
> @@ -2382,9 +2411,6 @@ ix86_option_override_internal (bool main_args_p,
> || TARGET_64BIT_P (opts->x_ix86_isa_flags))
> opts->x_ix86_regparm = REGPARM_MAX;
>
> - /* Default align_* from the processor table. */
> - ix86_default_align (opts);
> -
> /* Provide default for -mbranch-cost= value. */
> SET_OPTION_IF_UNSET (opts, opts_set, ix86_branch_cost,
> ix86_tune_cost->branch_cost);
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index
> 292b32c5e99..10f8b4e91a5 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -23829,20 +23829,12 @@ ix86_loop_unroll_adjust (unsigned nunroll,
> class loop *loop)
>
> /* Unroll small size loop when unroll factor is not explicitly
> specified. */
> - if (!(flag_unroll_loops
> - || flag_unroll_all_loops
> - || loop->unroll))
> + if (ix86_unroll_only_small_loops && !loop->unroll)
> {
> - nunroll = 1;
> -
> - /* Any explicit -f{no-}unroll-{all-}loops turns off
> - -munroll-only-small-loops. */
> - if (ix86_unroll_only_small_loops
> - && !OPTION_SET_P (flag_unroll_loops)
> - && loop->ninsns <= ix86_cost->small_unroll_ninsns)
> - nunroll = ix86_cost->small_unroll_factor;
> -
> - return nunroll;
> + if (loop->ninsns <= ix86_cost->small_unroll_ninsns)
> + return MIN (nunroll, ix86_cost->small_unroll_factor);
> + else
> + return 1;
> }
>
> if (!TARGET_ADJUST_UNROLL)
> diff --git a/gcc/loop-init.cc b/gcc/loop-init.cc index
> 9789efa1e11..f03c077cae1
> 100644
> --- a/gcc/loop-init.cc
> +++ b/gcc/loop-init.cc
> @@ -565,12 +565,10 @@ public:
> {}
>
> /* opt_pass methods: */
> - bool gate (function *fun) final override
> + bool gate (function *) final override
> {
> - return (flag_unroll_loops || flag_unroll_all_loops || cfun->has_unroll
> - || (targetm.loop_unroll_adjust
> - && optimize >= 2
> - && optimize_function_for_speed_p (fun)));
> + return (flag_unroll_loops || flag_unroll_all_loops
> + || cfun->has_unroll);
> }
>
> unsigned int execute (function *) final override; @@ -586,8 +584,7 @@
> pass_rtl_unroll_loops::execute (function *fun)
> if (dump_file)
> df_dump (dump_file);
>
> - if (flag_unroll_loops
> - || targetm.loop_unroll_adjust)
> + if (flag_unroll_loops)
> flags |= UAP_UNROLL;
> if (flag_unroll_all_loops)
> flags |= UAP_UNROLL_ALL;
> diff --git a/gcc/testsuite/gcc.target/i386/pr86270.c
> b/gcc/testsuite/gcc.target/i386/pr86270.c
> index cbc9fbb0450..98b012caf23 100644
> --- a/gcc/testsuite/gcc.target/i386/pr86270.c
> +++ b/gcc/testsuite/gcc.target/i386/pr86270.c
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-O2 -mno-unroll-only-small-loops" } */
> +/* { dg-options "-O2 -fno-unroll-loops" } */
>
> int *a;
> long len;
> diff --git a/gcc/testsuite/gcc.target/i386/pr93002.c
> b/gcc/testsuite/gcc.target/i386/pr93002.c
> index f75a847f75d..7e2d869e17b 100644
> --- a/gcc/testsuite/gcc.target/i386/pr93002.c
> +++ b/gcc/testsuite/gcc.target/i386/pr93002.c
> @@ -1,6 +1,6 @@
> /* PR target/93002 */
> /* { dg-do compile } */
> -/* { dg-options "-O2 -mno-unroll-only-small-loops" } */
> +/* { dg-options "-O2 -fno-unroll-loops" } */
> /* { dg-final { scan-assembler-not "cmp\[^\n\r]*-1" } } */
>
> volatile int sink;
> --
> 2.18.1
RE: [PATCH] i386: Only enable small loop unrolling in backend [PR 107602]
Liu, Hongtao via Gcc-patches Sun, 20 Nov 2022 17:01:47 -0800
- [PATCH] i386: Only enable small loop unrollin... Hongyu Wang via Gcc-patches
- RE: [PATCH] i386: Only enable small loop... Liu, Hongtao via Gcc-patches
- Re: [PATCH] i386: Only enable small ... Hongtao Liu via Gcc-patches
- Re: [PATCH] i386: Only enable sm... Hongyu Wang via Gcc-patches
- Re: [PATCH] i386: Only enable small loop... Jeff Law via Gcc-patches
- Re: [PATCH] i386: Only enable small ... Hongtao Liu via Gcc-patches
- Re: [PATCH] i386: Only enable small ... Hongyu Wang via Gcc-patches
