* RFA: RL78: Fix multiply costs when optimizing for size
@ 2015-08-05 13:52 Nick Clifton
2015-08-05 17:10 ` DJ Delorie
0 siblings, 1 reply; 2+ messages in thread
From: Nick Clifton @ 2015-08-05 13:52 UTC (permalink / raw)
To: dj; +Cc: gcc-patches
Hi DJ,
The patch below fixes a small problem with the RL78 backend. When
optimizing for size it is better to use a slow multiply instruction
than a faster, but larger, shift sequence. So the patch tweaks the
rtx costs for MULT insns when speed is not a priority.
Tested with no regressions on an rl78-elf toolchain.
OK to apply ?
Cheers
Nick
gcc/ChangeLog
2015-08-05 Nick Clifton <nickc@redhat.com>
* config/rl78/rl78.c (rl78_rtx_costs): Treat MULT insns as cheap
if optimizing for size.
Index: gcc/config/rl78/rl78.c
===================================================================
RCS file: /cvs/cvsfiles/gnupro/gcc/config/rl78/rl78.c,v
retrieving revision 1.12.6.15
diff -u -3 -p -r1.12.6.15 rl78.c
--- gcc/config/rl78/rl78.c 29 Jul 2015 12:24:04 -0000 1.12.6.15
+++ gcc/config/rl78/rl78.c 30 Jul 2015 15:20:10 -0000
@@ -4161,7 +4161,9 @@ static bool rl78_rtx_costs (rtx x,
switch (code)
{
case MULT:
- if (RL78_MUL_G14)
+ if (! speed)
+ * total = COSTS_N_INSNS (5);
+ else if (RL78_MUL_G14)
*total = COSTS_N_INSNS (14);
else if (RL78_MUL_G13)
*total = COSTS_N_INSNS (29);
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: RFA: RL78: Fix multiply costs when optimizing for size
2015-08-05 13:52 RFA: RL78: Fix multiply costs when optimizing for size Nick Clifton
@ 2015-08-05 17:10 ` DJ Delorie
0 siblings, 0 replies; 2+ messages in thread
From: DJ Delorie @ 2015-08-05 17:10 UTC (permalink / raw)
To: Nick Clifton; +Cc: gcc-patches
> OK to apply ?
Ok. Thanks!
> gcc/ChangeLog
> 2015-08-05 Nick Clifton <nickc@redhat.com>
>
> * config/rl78/rl78.c (rl78_rtx_costs): Treat MULT insns as cheap
> if optimizing for size.
>
> Index: gcc/config/rl78/rl78.c
> ===================================================================
> RCS file: /cvs/cvsfiles/gnupro/gcc/config/rl78/rl78.c,v
> retrieving revision 1.12.6.15
> diff -u -3 -p -r1.12.6.15 rl78.c
> --- gcc/config/rl78/rl78.c 29 Jul 2015 12:24:04 -0000 1.12.6.15
> +++ gcc/config/rl78/rl78.c 30 Jul 2015 15:20:10 -0000
> @@ -4161,7 +4161,9 @@ static bool rl78_rtx_costs (rtx x,
> switch (code)
> {
> case MULT:
> - if (RL78_MUL_G14)
> + if (! speed)
> + * total = COSTS_N_INSNS (5);
> + else if (RL78_MUL_G14)
> *total = COSTS_N_INSNS (14);
> else if (RL78_MUL_G13)
> *total = COSTS_N_INSNS (29);
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2015-08-05 13:52 RFA: RL78: Fix multiply costs when optimizing for size Nick Clifton
2015-08-05 17:10 ` DJ Delorie
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