freedreno/ir3/sched: try to avoid syncs

Similar to what we do in postsched.  It is useful for pre-RA sched to be
a bit aware of things that would cause syncs.  In particular for the tex
fetches, since the vecN src/dst tends to limit postsched's ability to
re-order them.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4923>

diff --git a/src/freedreno/ir3/ir3_sched.c b/src/freedreno/ir3/ir3_sched.c
index b4f1bc0a18721846cdac8f23bd049ef46e4ffff6..57567555fd4ab75f00fa9d32bab3302c5d403f5d 100644 (file)
--- a/src/freedreno/ir3/ir3_sched.c
+++ b/src/freedreno/ir3/ir3_sched.c
@@ -93,8 +93,12 @@ struct ir3_sched_ctx {
        struct ir3_instruction *pred;      /* current p0.x user, if any */
 
        int remaining_kills;
+       int remaining_tex;
 
        bool error;
+
+       int sfu_delay;
+       int tex_delay;
 };
 
 struct ir3_sched_node {
@@ -181,6 +185,7 @@ schedule(struct ir3_sched_ctx *ctx, struct ir3_instruction *instr)
        ctx->scheduled = instr;
 
        if (is_kill(instr)){
+               assert(ctx->remaining_kills > 0);
                ctx->remaining_kills--;
        }
 
@@ -200,6 +205,32 @@ schedule(struct ir3_sched_ctx *ctx, struct ir3_instruction *instr)
        }
 
        dag_prune_head(ctx->dag, &n->dag);
+
+       if (is_meta(instr) && (instr->opc != OPC_META_TEX_PREFETCH))
+               return;
+
+       if (is_sfu(instr)) {
+               ctx->sfu_delay = 8;
+       } else if (check_src_cond(instr, is_sfu)) {
+               ctx->sfu_delay = 0;
+       } else if (ctx->sfu_delay > 0) {
+               ctx->sfu_delay--;
+       }
+
+       if (is_tex_or_prefetch(instr)) {
+               /* NOTE that this isn't an attempt to hide texture fetch latency,
+                * but an attempt to hide the cost of switching to another warp.
+                * If we can, we'd like to try to schedule another texture fetch
+                * before scheduling something that would sync.
+                */
+               ctx->tex_delay = 10;
+               assert(ctx->remaining_tex > 0);
+               ctx->remaining_tex--;
+       } else if (check_src_cond(instr, is_tex_or_prefetch)) {
+               ctx->tex_delay = 0;
+       } else if (ctx->tex_delay > 0) {
+               ctx->tex_delay--;
+       }
 }
 
 struct ir3_sched_notes {
@@ -406,8 +437,35 @@ live_effect(struct ir3_instruction *instr)
        return new_live - freed_live;
 }
 
-static struct ir3_sched_node * choose_instr_inc(struct ir3_sched_ctx *ctx,
-               struct ir3_sched_notes *notes, bool avoid_output);
+/* Determine if this is an instruction that we'd prefer not to schedule
+ * yet, in order to avoid an (ss)/(sy) sync.  This is limited by the
+ * sfu_delay/tex_delay counters, ie. the more cycles it has been since
+ * the last SFU/tex, the less costly a sync would be.
+ */
+static bool
+would_sync(struct ir3_sched_ctx *ctx, struct ir3_instruction *instr)
+{
+       if (ctx->sfu_delay) {
+               if (check_src_cond(instr, is_sfu))
+                       return true;
+       }
+
+       /* We mostly just want to try to schedule another texture fetch
+        * before scheduling something that would (sy) sync, so we can
+        * limit this rule to cases where there are remaining texture
+        * fetches
+        */
+       if (ctx->tex_delay && ctx->remaining_tex) {
+               if (check_src_cond(instr, is_tex_or_prefetch))
+                       return true;
+       }
+
+       return false;
+}
+
+static struct ir3_sched_node *
+choose_instr_inc(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
+               bool avoid_sync, bool avoid_output);
 
 /**
  * Chooses an instruction to schedule using the Goodman/Hsu (1988) CSR (Code
@@ -417,12 +475,17 @@ static struct ir3_sched_node * choose_instr_inc(struct ir3_sched_ctx *ctx,
  * or are even.
  */
 static struct ir3_sched_node *
-choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
+choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
+               bool avoid_sync)
 {
+       const char *mode = avoid_sync ? "-as" : "";
        struct ir3_sched_node *chosen = NULL;
 
        /* Find a ready inst with regs freed and pick the one with max cost. */
        foreach_sched_node (n, &ctx->dag->heads) {
+               if (avoid_sync && would_sync(ctx, n->instr))
+                       continue;
+
                unsigned d = ir3_delay_calc(ctx->block, n->instr, false, false);
 
                if (d > 0)
@@ -440,12 +503,15 @@ choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
        }
 
        if (chosen) {
-               di(chosen->instr, "dec: chose (freed+ready)");
+               di(chosen->instr, "dec%s: chose (freed+ready)", mode);
                return chosen;
        }
 
        /* Find a leader with regs freed and pick the one with max cost. */
        foreach_sched_node (n, &ctx->dag->heads) {
+               if (avoid_sync && would_sync(ctx, n->instr))
+                       continue;
+
                if (live_effect(n->instr) > -1)
                        continue;
 
@@ -458,7 +524,7 @@ choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
        }
 
        if (chosen) {
-               di(chosen->instr, "dec: chose (freed)");
+               di(chosen->instr, "dec%s: chose (freed)", mode);
                return chosen;
        }
 
@@ -470,6 +536,9 @@ choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
         * XXX: Should this prioritize ready?
         */
        foreach_sched_node (n, &ctx->dag->heads) {
+               if (avoid_sync && would_sync(ctx, n->instr))
+                       continue;
+
                unsigned d = ir3_delay_calc(ctx->block, n->instr, false, false);
 
                if (d > 0)
@@ -486,11 +555,14 @@ choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
        }
 
        if (chosen) {
-               di(chosen->instr, "dec: chose (neutral+ready)");
+               di(chosen->instr, "dec%s: chose (neutral+ready)", mode);
                return chosen;
        }
 
        foreach_sched_node (n, &ctx->dag->heads) {
+               if (avoid_sync && would_sync(ctx, n->instr))
+                       continue;
+
                if (live_effect(n->instr) > 0)
                        continue;
 
@@ -502,11 +574,11 @@ choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
        }
 
        if (chosen) {
-               di(chosen->instr, "dec: chose (neutral)");
+               di(chosen->instr, "dec%s: chose (neutral)", mode);
                return chosen;
        }
 
-       return choose_instr_inc(ctx, notes, true);
+       return choose_instr_inc(ctx, notes, avoid_sync, true);
 }
 
 /**
@@ -515,8 +587,9 @@ choose_instr_dec(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
  */
 static struct ir3_sched_node *
 choose_instr_inc(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
-               bool avoid_output)
+               bool avoid_sync, bool avoid_output)
 {
+       const char *mode = avoid_sync ? "-as" : "";
        struct ir3_sched_node *chosen = NULL;
 
        /*
@@ -531,6 +604,9 @@ choose_instr_inc(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
                if (avoid_output && n->output)
                        continue;
 
+               if (avoid_sync && would_sync(ctx, n->instr))
+                       continue;
+
                unsigned d = ir3_delay_calc(ctx->block, n->instr, false, false);
 
                if (d > 0)
@@ -548,7 +624,7 @@ choose_instr_inc(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
        }
 
        if (chosen) {
-               di(chosen->instr, "inc: chose (distance+ready)");
+               di(chosen->instr, "inc%s: chose (distance+ready)", mode);
                return chosen;
        }
 
@@ -557,6 +633,9 @@ choose_instr_inc(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
                if (avoid_output && n->output)
                        continue;
 
+               if (avoid_sync && would_sync(ctx, n->instr))
+                       continue;
+
                if (!check_instr(ctx, notes, n->instr))
                        continue;
 
@@ -569,7 +648,7 @@ choose_instr_inc(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes,
        }
 
        if (chosen) {
-               di(chosen->instr, "inc: chose (distance)");
+               di(chosen->instr, "inc%s: chose (distance)", mode);
                return chosen;
        }
 
@@ -631,11 +710,15 @@ choose_instr(struct ir3_sched_ctx *ctx, struct ir3_sched_notes *notes)
        if (chosen)
                return chosen->instr;
 
-       chosen = choose_instr_dec(ctx, notes);
+       chosen = choose_instr_dec(ctx, notes, true);
+       if (chosen)
+               return chosen->instr;
+
+       chosen = choose_instr_dec(ctx, notes, false);
        if (chosen)
                return chosen->instr;
 
-       chosen = choose_instr_inc(ctx, notes, false);
+       chosen = choose_instr_inc(ctx, notes, false, false);
        if (chosen)
                return chosen->instr;
 
@@ -912,9 +995,12 @@ sched_block(struct ir3_sched_ctx *ctx, struct ir3_block *block)
        sched_dag_init(ctx);
 
        ctx->remaining_kills = 0;
+       ctx->remaining_tex = 0;
        foreach_instr_safe (instr, &ctx->unscheduled_list) {
                if (is_kill(instr))
                        ctx->remaining_kills++;
+               if (is_tex_or_prefetch(instr))
+                       ctx->remaining_tex++;
        }
 
        /* First schedule all meta:input instructions, followed by