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freedreno/ir3: try to avoid syncs 

Update postsched to be better aware of where costly (ss) syncs would
result.  Sometimes it is better to allow a nop or two, to avoid a
sync quickly after an SFU.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4071>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4071>
This commit is contained in:
Rob Clark 2020-03-04 09:06:51 -08:00 committed by Marge Bot
parent cc82521de4
commit 3c96e25de7
1 changed files with 55 additions and 1 deletions
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56
src/freedreno/ir3/ir3_postsched.c
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@ -62,6 +62,8 @@ struct ir3_postsched_ctx {
struct ir3_instruction *pred; /* current p0.x user, if any */
bool error;
int sfu_delay;
};
struct ir3_postsched_node {
@ -97,6 +99,12 @@ schedule(struct ir3_postsched_ctx *ctx, struct ir3_instruction *instr)
list_addtail(&instr->node, &instr->block->instr_list);
ctx->scheduled = instr;
if (is_sfu(instr)) {
ctx->sfu_delay = 8;
} else if (ctx->sfu_delay > 0) {
ctx->sfu_delay--;
}
struct ir3_postsched_node *n = instr->data;
dag_prune_head(ctx->dag, &n->dag);
}
@ -119,6 +127,24 @@ dump_state(struct ir3_postsched_ctx *ctx)
}
}
/* Determine if this is an instruction that we'd prefer not to schedule
* yet, in order to avoid an (ss) sync. This is limited by the sfu_delay
* counter, ie. the more cycles it has been since the last SFU, the less
* costly a sync would be.
*/
static bool
would_sync(struct ir3_postsched_ctx *ctx, struct ir3_instruction *instr)
{
if (ctx->sfu_delay) {
struct ir3_register *reg;
foreach_src (reg, instr)
if (reg->instr && is_sfu(reg->instr))
return true;
}
return false;
}
/* find instruction to schedule: */
static struct ir3_instruction *
choose_instr(struct ir3_postsched_ctx *ctx)
@ -195,7 +221,35 @@ choose_instr(struct ir3_postsched_ctx *ctx)
return chosen->instr;
}
/* First try to find a ready leader w/ soft delay (ie. including extra
/*
* Sometimes be better to take a nop, rather than scheduling an
* instruction that would require an (ss) shortly after another
* SFU.. ie. if last SFU was just one or two instr ago, and we
* could choose between taking a nop and then scheduling
* something else, vs scheduling the immed avail instruction that
* would require (ss), we are better with the nop.
*/
for (unsigned delay = 0; delay < 4; delay++) {
foreach_sched_node (n, &ctx->dag->heads) {
if (would_sync(ctx, n->instr))
continue;
unsigned d = ir3_delay_calc(ctx->block, n->instr, true, false);
if (d > delay)
continue;
if (!chosen || (chosen->max_delay < n->max_delay))
chosen = n;
}
if (chosen) {
di(chosen->instr, "csp: chose (soft ready, delay=%u)", delay);
return chosen->instr;
}
}
/* Next try to find a ready leader w/ soft delay (ie. including extra
* delay for things like tex fetch which can be synchronized w/ sync
* bit (but we probably do want to schedule some other instructions
* while we wait)