https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124901
--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Drea Pinski from comment #4)
> You have to add a clone method to cprop_hardreg. After that it should just
> work :).
Cutting some corners and just moving pass_cprop_hardreg after
pass_reorder_blocks:
diff --git a/gcc/passes.def b/gcc/passes.def
index cdddb87302f..673bf3ebe46 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -540,9 +540,9 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_dep_fusion);
NEXT_PASS (pass_regrename);
NEXT_PASS (pass_fold_mem_offsets);
- 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);
results in:
.L4:
- movl %eax, %ecx
cmpl %esi, (%eax)
jne .L11
- movl %ecx, %eax
popl %ebx
But the pass *does not* perform the trivial propagation of %ecx to %eax in the
final BB. The change even slightly regresses linux code size:
$ size *.o
text data bss dec hex filename
29434169 4932443 754228 35120840 217e6c8 vmlinux-cprop.o
29415516 4932443 754228 35102187 2179deb vmlinux-new.o
29432351 4932443 754228 35119022 217dfae vmlinux-old.o
