https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113613
--- Comment #6 from Alex Coplan <acoplan at gcc dot gnu.org> ---
FWIW, if I move ldp_fusion1 before early_ra, with:
diff --git a/gcc/config/aarch64/aarch64-passes.def
b/gcc/config/aarch64/aarch64-passes.def
index 769d48f4faa..3853f6bf7a4 100644
--- a/gcc/config/aarch64/aarch64-passes.def
+++ b/gcc/config/aarch64/aarch64-passes.def
@@ -18,6 +18,7 @@
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
+INSERT_PASS_BEFORE (pass_sched, 1, pass_ldp_fusion);
INSERT_PASS_BEFORE (pass_sched, 1, pass_aarch64_early_ra);
INSERT_PASS_AFTER (pass_regrename, 1, pass_fma_steering);
INSERT_PASS_BEFORE (pass_reorder_blocks, 1, pass_track_speculation);
@@ -25,5 +26,4 @@ INSERT_PASS_BEFORE (pass_late_thread_prologue_and_epilogue,
1, pass_switch_pstat
INSERT_PASS_AFTER (pass_machine_reorg, 1, pass_tag_collision_avoidance);
INSERT_PASS_BEFORE (pass_shorten_branches, 1, pass_insert_bti);
INSERT_PASS_AFTER (pass_if_after_combine, 1, pass_cc_fusion);
-INSERT_PASS_BEFORE (pass_early_remat, 1, pass_ldp_fusion);
INSERT_PASS_BEFORE (pass_peephole2, 1, pass_ldp_fusion);
we get:
f:
.LFB0:
.cfi_startproc
adrp x0, .LANCHOR0
add x0, x0, :lo12:.LANCHOR0
ldp d31, d30, [x0]
ldp d29, d28, [x0, 32]
fadd v29.2s, v31.2s, v29.2s
fadd v28.2s, v30.2s, v28.2s
stp d29, d28, [x0]
ret
note that this does use more registers, though, so it's not necessarily a clear
win in the general case (particularly if register pressure is already high).
