On Mon, Aug 19, 2013 at 8:47 AM, Alan Modra wrote:
> gcc/
...
> * doc/tm.texi.in (TARGET_INIT_LOWER_SUBREG): Document.
ChangeLog update needed here, the new hook is documented in target.def.
> +static void
> +rs6000_init_lower_subreg (void *data)
> +{
Functions should start with a leading comment.
> Index: gcc/target.def
> ===================================================================
> --- gcc/target.def (revision 201834)
> +++ gcc/target.def (working copy)
> @@ -5110,6 +5110,14 @@ comparison code or operands.",
> void, (int *code, rtx *op0, rtx *op1, bool op0_preserve_value),
> default_canonicalize_comparison)
>
> +/* Allow modification of subreg choices. */
> +DEFHOOK
> +(init_lower_subreg,
> + "This hook allows modification of the choices the lower_subreg pass \
> +will make for particular subreg modes. @var{data} is a pointer to a \
> +@code{struct target_lower_subreg}.",
> + void, (void *data), NULL)
> +
Bah, another void* pointer...
I would have preferred a hook that takes a machine_mode and let it be
called in the first loop of compute_costs, something like the code
below.
Your solution gives the target a lot more power to control the split
decisions (adjust individual costs, review overall choice of modes to
split, etc.) but I don't think any target really needs that. Do you
think the target should have more control over splitting than just on
per machine_mode basis?
Ciao!
Steven
Index: lower-subreg.c
===================================================================
--- lower-subreg.c (revision 201887)
+++ lower-subreg.c (working copy)
@@ -208,7 +208,18 @@ compute_costs (bool speed_p, struct cost_rtxes *rt
if (factor > 1)
{
int mode_move_cost;
-
+ bool split_profitable_mode = true;
+
+ if (targetm.split_profitable_mode
+ && ! targetm.split_profitable_mode ((mode)))
+ {
+ split_profitable_mode = false;
+ if (LOG_COSTS)
+ fprintf (stderr,
+ "%s move: target signals splitting is not
profitable%s\n",
+ GET_MODE_NAME (mode), FORCE_LOWERING ? "
(forcing)" : "");
+ }
+
PUT_MODE (rtxes->target, mode);
PUT_MODE (rtxes->source, mode);
mode_move_cost = set_rtx_cost (rtxes->set, speed_p);
@@ -218,7 +229,9 @@ compute_costs (bool speed_p, struct cost_rtxes *rt
GET_MODE_NAME (mode), mode_move_cost,
word_move_cost, factor);
- if (FORCE_LOWERING || mode_move_cost >= word_move_cost * factor)
+ if (FORCE_LOWERING
+ || ((mode_move_cost >= word_move_cost * factor)
+ && split_profitable_mode))
{
choices[speed_p].move_modes_to_split[i] = true;
choices[speed_p].something_to_do = true;
