Mesa (master): freedreno/ir3: try to avoid syncs
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Tue Mar 10 16:21:57 UTC 2020
Module: Mesa
Branch: master
Commit: 3c96e25de77b4879f54ef5727378dacf13e7e398
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=3c96e25de77b4879f54ef5727378dacf13e7e398
Author: Rob Clark <robdclark at chromium.org>
Date: Wed Mar 4 09:06:51 2020 -0800
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 at 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>
---
src/freedreno/ir3/ir3_postsched.c | 56 ++++++++++++++++++++++++++++++++++++++-
1 file changed, 55 insertions(+), 1 deletion(-)
diff --git a/src/freedreno/ir3/ir3_postsched.c b/src/freedreno/ir3/ir3_postsched.c
index 1e706f75a24..b283af486fb 100644
--- a/src/freedreno/ir3/ir3_postsched.c
+++ b/src/freedreno/ir3/ir3_postsched.c
@@ -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)
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