[gcc r15-7871] AArch64: Enable early scheduling for -O3 and higher (PR118351)

[Wilco Dijkstra via Gcc-cvs]

https://gcc.gnu.org/g:f870302515d5fcf7355f0108c3ead0038ff326fd

commit r15-7871-gf870302515d5fcf7355f0108c3ead0038ff326fd
Author: Wilco Dijkstra <wilco.dijks...@arm.com>
Date:   Mon Mar 3 16:47:32 2025 +0000

    AArch64: Enable early scheduling for -O3 and higher (PR118351)
    
    Enable the early scheduler on AArch64 for O3/Ofast.  This means GCC15 
benefits
    from much faster build times with -O2, but avoids the regressions in lbm 
which
    is very sensitive to minor scheduling changes due to long FMA chains.
    
    gcc:
            PR target/118351
            PR other/38768
            * common/config/aarch64/aarch64-common.cc: Enable early scheduling 
with
            -O3 and higher.
            * doc/invoke.texi (-fschedule-insns): Update comment.

Diff:
---
 gcc/common/config/aarch64/aarch64-common.cc | 4 +++-
 gcc/doc/invoke.texi                         | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/gcc/common/config/aarch64/aarch64-common.cc 
b/gcc/common/config/aarch64/aarch64-common.cc
index 500bf784983d..b9ed83642ade 100644
--- a/gcc/common/config/aarch64/aarch64-common.cc
+++ b/gcc/common/config/aarch64/aarch64-common.cc
@@ -53,8 +53,10 @@ static const struct default_options 
aarch_option_optimization_table[] =
     { OPT_LEVELS_ALL, OPT_fomit_frame_pointer, NULL, 0 },
     /* Enable -fsched-pressure by default when optimizing.  */
     { OPT_LEVELS_1_PLUS, OPT_fsched_pressure, NULL, 1 },
-    /* Disable early scheduling due to high compile-time overheads.  */
+    /* Except for -O3 and higher, disable early scheduling due to high
+       compile-time overheads.  */
     { OPT_LEVELS_ALL, OPT_fschedule_insns, NULL, 0 },
+    { OPT_LEVELS_3_PLUS, OPT_fschedule_insns, NULL, 1 },
     /* Enable redundant extension instructions removal at -O2 and higher.  */
     { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_mearly_ra_, NULL, AARCH64_EARLY_RA_ALL },
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 6f0779b900cb..304de88db07c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -13507,7 +13507,9 @@ helps machines that have slow floating point or memory 
load instructions
 by allowing other instructions to be issued until the result of the load
 or floating-point instruction is required.
 
-Enabled at levels @option{-O2}, @option{-O3}.
+Conventionally enabled at optimization levels @option{-O2} and @option{-O3}.
+However, many targets override this behavior.  For example, on x86, it is
+disabled at all levels, while on AArch64, it is enabled only at @option{-O3}.
 
 @opindex fschedule-insns2
 @item -fschedule-insns2