On 10/26/14 19:53, Zhenqiang Chen wrote:
Hi,
Function noce_try_store_flag_mask converts "if (test) x = 0;" to "x &=
-(test == 0);"
But from code size view, "x &= -(test == 0);" might have more instructions
than "if (test) x = 0;". The patch checks the cost to determine the
conversion is valuable or not.
Bootstrap and no make check regression on X86-64.
No make check regression with Cortex-M0 qemu.
For CSiBE, ARM Cortex-m0 result is a little better. A little regression for
MIPS. Roughly no change for PowerPC.
OK for trunk?
Thanks!
-Zhenqiang
ChangeLog:
2014-10-27 Zhenqiang Chen <zhenqiang.c...@arm.com>
* ifcvt.c (noce_try_store_flag_mask): Check rtx cost.
testsuite/ChangeLog:
2014-10-27 Zhenqiang Chen <zhenqiang.c...@arm.com>
* gcc.target/arm/ifcvt-size-check.c: New test.
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index 949d2b4..3abd518 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -1393,6 +1393,14 @@ noce_try_store_flag_mask (struct noce_if_info
*if_info)
if (!seq)
return FALSE;
+ if (optimize_function_for_size_p (cfun))
+ {
+ int old_cost = COSTS_N_INSNS (if_info->branch_cost + 1);
+ int new_cost = seq_cost (seq, 0);
+ if (new_cost > old_cost)
+ return FALSE;
+ }
+
As Andrew pointed out, there's really no reason to limit this to cases
where we're optimizing for size. So that check should be removed.
You should also engage with Michael to determine if the MIPS regressions
are significant enough to warrant deeper investigation. My gut tells me
that if MIPS is regressing because of this, then that's going to be an
issue in the MIPS costing model that the MIPS folks will ultimately need
to fix.
jeff
