freedreno/ir3: track register usage in first RA pass

We'll use the feedback from the first pass to select a target register
usage in the second pass.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4071>

diff --git a/src/freedreno/ir3/ir3_ra.c b/src/freedreno/ir3/ir3_ra.c
index 35a95fd1050ddb27977a858d4bd7a718d9bbfb25..39507184105a2a86a47c81ea9d9ffbb5bdc024c7 100644 (file)
--- a/src/freedreno/ir3/ir3_ra.c
+++ b/src/freedreno/ir3/ir3_ra.c
@@ -345,6 +345,15 @@ struct ir3_ra_ctx {
        unsigned instr_cnt;
        unsigned *def, *use;     /* def/use table */
        struct ir3_ra_instr_data *instrd;
+
+       /* Tracking for max half/full register assigned.  We don't need to
+        * track high registers.
+        *
+        * The feedback about registers used in first pass is used to choose
+        * a target register usage to round-robin between in the 2nd pass.
+        */
+       unsigned max_assigned;
+       unsigned max_half_assigned;
 };
 
 /* does it conflict? */
@@ -1203,6 +1212,35 @@ reg_assign(struct ir3_ra_ctx *ctx, struct ir3_register *reg,
        }
 }
 
+static void
+account_assignment(struct ir3_ra_ctx *ctx, struct ir3_instruction *instr)
+{
+       struct ir3_ra_instr_data *id;
+       struct ir3_register *dst = instr->regs[0];
+       unsigned max;
+
+       if (is_high(instr))
+               return;
+
+       if (dst->flags & IR3_REG_ARRAY) {
+               struct ir3_array *arr =
+                       ir3_lookup_array(ctx->ir, dst->array.id);
+               max = arr->reg + arr->length;
+       } else if ((id = &ctx->instrd[instr->ip]) && id->defn) {
+               unsigned name = scalar_name(ctx, id->defn, 0);
+               unsigned r = ra_get_node_reg(ctx->g, name);
+               max = ctx->set->ra_reg_to_gpr[r] + id->off;
+       } else {
+               return;
+       }
+
+       if (is_half(instr)) {
+               ctx->max_half_assigned = MAX2(ctx->max_half_assigned, max);
+       } else {
+               ctx->max_assigned = MAX2(ctx->max_assigned, max);
+       }
+}
+
 /* helper to determine which regs to assign in which pass: */
 static bool
 should_assign(struct ir3_ra_ctx *ctx, struct ir3_instruction *instr)
@@ -1220,6 +1258,7 @@ ra_block_alloc(struct ir3_ra_ctx *ctx, struct ir3_block *block)
                struct ir3_register *reg;
 
                if (writes_gpr(instr)) {
+                       account_assignment(ctx, instr);
                        if (should_assign(ctx, instr)) {
                                reg_assign(ctx, instr->regs[0], instr);
                                if (instr->regs[0]->flags & IR3_REG_HALF)
@@ -1517,6 +1556,8 @@ ir3_ra_pass(struct ir3_shader_variant *v, struct ir3_instruction **precolor,
        ret = ra_alloc(&ctx);
        ra_destroy(&ctx);
 
+       printf("#### max_assigned=%u, max_half_assigned=%u\n", ctx.max_assigned, ctx.max_half_assigned);
+
        return ret;
 }