[PATCH] Disable loop2_invariant for -Os
Zhenqiang Chen
zhenqiang.chen@arm.com
Wed Jun 27 08:48:00 GMT 2012
Hi,
In general, invariant motion itself can not reduce code size. But it will
change the liverange of the invariant, which might lead to more spilling.
The patch disables loop2_invariant when optimizing for size.
I measured the code size benefit for four targets based on CSiBE benchmark:
ARM: 0.33%
MIPS: 1.15%
PPC: 0.24%
X86: 0.45%
Is it OK for trunk?
Thanks!
-Zhenqiang
ChangeLog:
2012-06-27 Zhenqiang Chen <zhenqiang.chen@arm.com>
* loop-init.c (gate_rtl_move_loop_invariants): Disable
loop2_invariant
when optimizing function for size.
diff --git a/gcc/loop-init.c b/gcc/loop-init.c
index 03f8f61..5d8cf73 100644
--- a/gcc/loop-init.c
+++ b/gcc/loop-init.c
@@ -273,6 +273,12 @@ struct rtl_opt_pass pass_rtl_loop_done =
static bool
gate_rtl_move_loop_invariants (void)
{
+ /* In general, invariant motion can not reduce code size. But it will
+ change the liverange of the invariant, which increases the register
+ pressure and might lead to more spilling. */
+ if (optimize_function_for_size_p (cfun))
+ return false;
+
return flag_move_loop_invariants;
}
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