v3d: handle tlb read dependency tracking as if they were writes
[mesa.git] / src / broadcom / compiler / qpu_schedule.c
index b404390a799879d8e4b359490eaf69de2d1be64c..b8e04f6ea1303c07d8c7dd723c86ebc60bbc6590 100644 (file)
 #include "qpu/qpu_disasm.h"
 #include "v3d_compiler.h"
 #include "util/ralloc.h"
+#include "util/dag.h"
 
 static bool debug;
 
 struct schedule_node_child;
 
 struct schedule_node {
+        struct dag_node dag;
         struct list_head link;
         struct qinst *inst;
-        struct schedule_node_child *children;
-        uint32_t child_count;
-        uint32_t child_array_size;
-        uint32_t parent_count;
 
         /* Longest cycles + instruction_latency() of any parent of this node. */
         uint32_t unblocked_time;
@@ -67,11 +65,6 @@ struct schedule_node {
         uint32_t latency;
 };
 
-struct schedule_node_child {
-        struct schedule_node *node;
-        bool write_after_read;
-};
-
 /* When walking the instructions in reverse, we need to swap before/after in
  * add_dep().
  */
@@ -79,6 +72,7 @@ enum direction { F, R };
 
 struct schedule_state {
         const struct v3d_device_info *devinfo;
+        struct dag *dag;
         struct schedule_node *last_r[6];
         struct schedule_node *last_rf[64];
         struct schedule_node *last_sf;
@@ -101,37 +95,17 @@ add_dep(struct schedule_state *state,
         bool write)
 {
         bool write_after_read = !write && state->dir == R;
+        void *edge_data = (void *)(uintptr_t)write_after_read;
 
         if (!before || !after)
                 return;
 
         assert(before != after);
 
-        if (state->dir == R) {
-                struct schedule_node *t = before;
-                before = after;
-                after = t;
-        }
-
-        for (int i = 0; i < before->child_count; i++) {
-                if (before->children[i].node == after &&
-                    (before->children[i].write_after_read == write_after_read)) {
-                        return;
-                }
-        }
-
-        if (before->child_array_size <= before->child_count) {
-                before->child_array_size = MAX2(before->child_array_size * 2, 16);
-                before->children = reralloc(before, before->children,
-                                            struct schedule_node_child,
-                                            before->child_array_size);
-        }
-
-        before->children[before->child_count].node = after;
-        before->children[before->child_count].write_after_read =
-                write_after_read;
-        before->child_count++;
-        after->parent_count++;
+        if (state->dir == F)
+                dag_add_edge(&before->dag, &after->dag, edge_data);
+        else
+                dag_add_edge(&after->dag, &before->dag, edge_data);
 }
 
 static void
@@ -154,6 +128,9 @@ add_write_dep(struct schedule_state *state,
 static bool
 qpu_inst_is_tlb(const struct v3d_qpu_instr *inst)
 {
+        if (inst->sig.ldtlb || inst->sig.ldtlbu)
+                return true;
+
         if (inst->type != V3D_QPU_INSTR_TYPE_ALU)
                 return false;
 
@@ -179,7 +156,10 @@ process_mux_deps(struct schedule_state *state, struct schedule_node *n,
                 add_read_dep(state, state->last_rf[n->inst->qpu.raddr_a], n);
                 break;
         case V3D_QPU_MUX_B:
-                add_read_dep(state, state->last_rf[n->inst->qpu.raddr_b], n);
+                if (!n->inst->qpu.sig.small_imm) {
+                        add_read_dep(state,
+                                     state->last_rf[n->inst->qpu.raddr_b], n);
+                }
                 break;
         default:
                 add_read_dep(state, state->last_r[mux - V3D_QPU_MUX_R0], n);
@@ -195,6 +175,9 @@ process_waddr_deps(struct schedule_state *state, struct schedule_node *n,
         if (!magic) {
                 add_write_dep(state, &state->last_rf[waddr], n);
         } else if (v3d_qpu_magic_waddr_is_tmu(waddr)) {
+                /* XXX perf: For V3D 4.x, we could reorder TMU writes other
+                 * than the TMUS/TMUD/TMUA to improve scheduling flexibility.
+                 */
                 add_write_dep(state, &state->last_tmu_write, n);
                 switch (waddr) {
                 case V3D_QPU_WADDR_TMUS:
@@ -233,6 +216,16 @@ process_waddr_deps(struct schedule_state *state, struct schedule_node *n,
                         add_write_dep(state, &state->last_tlb, n);
                         break;
 
+                case V3D_QPU_WADDR_SYNC:
+                case V3D_QPU_WADDR_SYNCB:
+                case V3D_QPU_WADDR_SYNCU:
+                        /* For CS barrier(): Sync against any other memory
+                         * accesses.  There doesn't appear to be any need for
+                         * barriers to affect ALU operations.
+                         */
+                        add_write_dep(state, &state->last_tmu_write, n);
+                        break;
+
                 case V3D_QPU_WADDR_NOP:
                         break;
 
@@ -243,30 +236,6 @@ process_waddr_deps(struct schedule_state *state, struct schedule_node *n,
         }
 }
 
-static void
-process_cond_deps(struct schedule_state *state, struct schedule_node *n,
-                  enum v3d_qpu_cond cond)
-{
-        if (cond != V3D_QPU_COND_NONE)
-                add_read_dep(state, state->last_sf, n);
-}
-
-static void
-process_pf_deps(struct schedule_state *state, struct schedule_node *n,
-                enum v3d_qpu_pf pf)
-{
-        if (pf != V3D_QPU_PF_NONE)
-                add_write_dep(state, &state->last_sf, n);
-}
-
-static void
-process_uf_deps(struct schedule_state *state, struct schedule_node *n,
-                enum v3d_qpu_uf uf)
-{
-        if (uf != V3D_QPU_UF_NONE)
-                add_write_dep(state, &state->last_sf, n);
-}
-
 /**
  * Common code for dependencies that need to be tracked both forward and
  * backward.
@@ -280,6 +249,11 @@ calculate_deps(struct schedule_state *state, struct schedule_node *n)
         const struct v3d_device_info *devinfo = state->devinfo;
         struct qinst *qinst = n->inst;
         struct v3d_qpu_instr *inst = &qinst->qpu;
+        /* If the input and output segments are shared, then all VPM reads to
+         * a location need to happen before all writes.  We handle this by
+         * serializing all VPM operations for now.
+         */
+        bool separate_vpm_segment = false;
 
         if (inst->type == V3D_QPU_INSTR_TYPE_BRANCH) {
                 if (inst->branch.cond != V3D_QPU_BRANCH_COND_ALWAYS)
@@ -321,6 +295,14 @@ calculate_deps(struct schedule_state *state, struct schedule_node *n)
                 add_write_dep(state, &state->last_vpm, n);
                 break;
 
+        case V3D_QPU_A_LDVPMV_IN:
+        case V3D_QPU_A_LDVPMD_IN:
+        case V3D_QPU_A_LDVPMG_IN:
+        case V3D_QPU_A_LDVPMP:
+                if (!separate_vpm_segment)
+                        add_write_dep(state, &state->last_vpm, n);
+                break;
+
         case V3D_QPU_A_VPMWT:
                 add_read_dep(state, state->last_vpm, n);
                 break;
@@ -334,19 +316,6 @@ calculate_deps(struct schedule_state *state, struct schedule_node *n)
                 add_write_dep(state, &state->last_tlb, n);
                 break;
 
-        case V3D_QPU_A_FLAPUSH:
-        case V3D_QPU_A_FLBPUSH:
-        case V3D_QPU_A_VFLA:
-        case V3D_QPU_A_VFLNA:
-        case V3D_QPU_A_VFLB:
-        case V3D_QPU_A_VFLNB:
-                add_read_dep(state, state->last_sf, n);
-                break;
-
-        case V3D_QPU_A_FLBPOP:
-                add_write_dep(state, &state->last_sf, n);
-                break;
-
         default:
                 break;
         }
@@ -392,6 +361,7 @@ calculate_deps(struct schedule_state *state, struct schedule_node *n)
                 for (int i = 0; i < ARRAY_SIZE(state->last_r); i++)
                         add_write_dep(state, &state->last_r[i], n);
                 add_write_dep(state, &state->last_sf, n);
+                add_write_dep(state, &state->last_rtop, n);
 
                 /* Scoreboard-locking operations have to stay after the last
                  * thread switch.
@@ -402,7 +372,7 @@ calculate_deps(struct schedule_state *state, struct schedule_node *n)
                 add_write_dep(state, &state->last_tmu_config, n);
         }
 
-        if (inst->sig.ldtmu) {
+        if (v3d_qpu_waits_on_tmu(inst)) {
                 /* TMU loads are coming from a FIFO, so ordering is important.
                  */
                 add_write_dep(state, &state->last_tmu_write, n);
@@ -412,29 +382,36 @@ calculate_deps(struct schedule_state *state, struct schedule_node *n)
                 add_write_dep(state, &state->last_tmu_config, n);
 
         if (inst->sig.ldtlb | inst->sig.ldtlbu)
-                add_read_dep(state, state->last_tlb, n);
+                add_write_dep(state, &state->last_tlb, n);
 
-        if (inst->sig.ldvpm)
+        if (inst->sig.ldvpm) {
                 add_write_dep(state, &state->last_vpm_read, n);
 
+                /* At least for now, we're doing shared I/O segments, so queue
+                 * all writes after all reads.
+                 */
+                if (!separate_vpm_segment)
+                        add_write_dep(state, &state->last_vpm, n);
+        }
+
         /* inst->sig.ldunif or sideband uniform read */
-        if (qinst->uniform != ~0)
+        if (vir_has_uniform(qinst))
                 add_write_dep(state, &state->last_unif, n);
 
-        process_cond_deps(state, n, inst->flags.ac);
-        process_cond_deps(state, n, inst->flags.mc);
-        process_pf_deps(state, n, inst->flags.apf);
-        process_pf_deps(state, n, inst->flags.mpf);
-        process_uf_deps(state, n, inst->flags.auf);
-        process_uf_deps(state, n, inst->flags.muf);
+        if (v3d_qpu_reads_flags(inst))
+                add_read_dep(state, state->last_sf, n);
+        if (v3d_qpu_writes_flags(inst))
+                add_write_dep(state, &state->last_sf, n);
 }
 
 static void
-calculate_forward_deps(struct v3d_compile *c, struct list_head *schedule_list)
+calculate_forward_deps(struct v3d_compile *c, struct dag *dag,
+                       struct list_head *schedule_list)
 {
         struct schedule_state state;
 
         memset(&state, 0, sizeof(state));
+        state.dag = dag;
         state.devinfo = c->devinfo;
         state.dir = F;
 
@@ -443,26 +420,29 @@ calculate_forward_deps(struct v3d_compile *c, struct list_head *schedule_list)
 }
 
 static void
-calculate_reverse_deps(struct v3d_compile *c, struct list_head *schedule_list)
+calculate_reverse_deps(struct v3d_compile *c, struct dag *dag,
+                       struct list_head *schedule_list)
 {
-        struct list_head *node;
         struct schedule_state state;
 
         memset(&state, 0, sizeof(state));
+        state.dag = dag;
         state.devinfo = c->devinfo;
         state.dir = R;
 
-        for (node = schedule_list->prev; schedule_list != node; node = node->prev) {
+        list_for_each_entry_rev(struct schedule_node, node, schedule_list,
+                                link) {
                 calculate_deps(&state, (struct schedule_node *)node);
         }
 }
 
 struct choose_scoreboard {
+        struct dag *dag;
         int tick;
-        int last_sfu_write_tick;
+        int last_magic_sfu_write_tick;
         int last_ldvary_tick;
         int last_uniforms_reset_tick;
-        uint32_t last_waddr_add, last_waddr_mul;
+        int last_thrsw_tick;
         bool tlb_locked;
 };
 
@@ -471,22 +451,8 @@ mux_reads_too_soon(struct choose_scoreboard *scoreboard,
                    const struct v3d_qpu_instr *inst, enum v3d_qpu_mux mux)
 {
         switch (mux) {
-        case V3D_QPU_MUX_A:
-                if (scoreboard->last_waddr_add == inst->raddr_a ||
-                    scoreboard->last_waddr_mul == inst->raddr_a) {
-                        return true;
-                }
-                break;
-
-        case V3D_QPU_MUX_B:
-                if (scoreboard->last_waddr_add == inst->raddr_b ||
-                    scoreboard->last_waddr_mul == inst->raddr_b) {
-                        return true;
-                }
-                break;
-
         case V3D_QPU_MUX_R4:
-                if (scoreboard->tick - scoreboard->last_sfu_write_tick <= 2)
+                if (scoreboard->tick - scoreboard->last_magic_sfu_write_tick <= 2)
                         return true;
                 break;
 
@@ -551,7 +517,7 @@ writes_too_soon_after_write(const struct v3d_device_info *devinfo,
          * This would normally be prevented by dependency tracking, but might
          * occur if a dead SFU computation makes it to scheduling.
          */
-        if (scoreboard->tick - scoreboard->last_sfu_write_tick < 2 &&
+        if (scoreboard->tick - scoreboard->last_magic_sfu_write_tick < 2 &&
             v3d_qpu_writes_r4(devinfo, inst))
                 return true;
 
@@ -579,10 +545,14 @@ get_instruction_priority(const struct v3d_qpu_instr *inst)
         next_score++;
 
         /* Schedule texture read results collection late to hide latency. */
-        if (inst->sig.ldtmu)
+        if (v3d_qpu_waits_on_tmu(inst))
                 return next_score;
         next_score++;
 
+        /* XXX perf: We should schedule SFU ALU ops so that the reader is 2
+         * instructions after the producer if possible, not just 1.
+         */
+
         /* Default score for things that aren't otherwise special. */
         baseline_score = next_score;
         next_score++;
@@ -610,6 +580,8 @@ qpu_accesses_peripheral(const struct v3d_qpu_instr *inst)
 {
         if (v3d_qpu_uses_vpm(inst))
                 return true;
+        if (v3d_qpu_uses_sfu(inst))
+                return true;
 
         if (inst->type == V3D_QPU_INSTR_TYPE_ALU) {
                 if (inst->alu.add.op != V3D_QPU_A_NOP &&
@@ -618,6 +590,9 @@ qpu_accesses_peripheral(const struct v3d_qpu_instr *inst)
                         return true;
                 }
 
+                if (inst->alu.add.op == V3D_QPU_A_TMUWT)
+                        return true;
+
                 if (inst->alu.mul.op != V3D_QPU_M_NOP &&
                     inst->alu.mul.magic_write &&
                     qpu_magic_waddr_is_periph(inst->alu.mul.waddr)) {
@@ -632,6 +607,37 @@ qpu_accesses_peripheral(const struct v3d_qpu_instr *inst)
                 inst->sig.wrtmuc);
 }
 
+static bool
+qpu_compatible_peripheral_access(const struct v3d_device_info *devinfo,
+                                 const struct v3d_qpu_instr *a,
+                                 const struct v3d_qpu_instr *b)
+{
+        const bool a_uses_peripheral = qpu_accesses_peripheral(a);
+        const bool b_uses_peripheral = qpu_accesses_peripheral(b);
+
+        /* We can always do one peripheral access per instruction. */
+        if (!a_uses_peripheral || !b_uses_peripheral)
+                return true;
+
+        if (devinfo->ver < 41)
+                return false;
+
+        /* V3D 4.1 and later allow TMU read along with a VPM read or write, and
+         * WRTMUC with a TMU magic register write (other than tmuc).
+         */
+        if ((a->sig.ldtmu && v3d_qpu_uses_vpm(b)) ||
+            (b->sig.ldtmu && v3d_qpu_uses_vpm(a))) {
+                return true;
+        }
+
+        if ((a->sig.wrtmuc && v3d_qpu_writes_tmu_not_tmuc(b)) ||
+            (b->sig.wrtmuc && v3d_qpu_writes_tmu_not_tmuc(a))) {
+                return true;
+        }
+
+        return false;
+}
+
 static bool
 qpu_merge_inst(const struct v3d_device_info *devinfo,
                struct v3d_qpu_instr *result,
@@ -643,12 +649,7 @@ qpu_merge_inst(const struct v3d_device_info *devinfo,
                 return false;
         }
 
-        /* Can't do more than one peripheral access in an instruction.
-         *
-         * XXX: V3D 4.1 allows TMU read along with a VPM read or write, and
-         * WRTMUC with a TMU magic register write (other than tmuc).
-         */
-        if (qpu_accesses_peripheral(a) && qpu_accesses_peripheral(b))
+        if (!qpu_compatible_peripheral_access(devinfo, a, b))
                 return false;
 
         struct v3d_qpu_instr merge = *a;
@@ -683,7 +684,8 @@ qpu_merge_inst(const struct v3d_device_info *devinfo,
 
         if (v3d_qpu_uses_mux(b, V3D_QPU_MUX_B)) {
                 if (v3d_qpu_uses_mux(a, V3D_QPU_MUX_B) &&
-                    a->raddr_b != b->raddr_b) {
+                    (a->raddr_b != b->raddr_b ||
+                     a->sig.small_imm != b->sig.small_imm)) {
                         return false;
                 }
                 merge.raddr_b = b->raddr_b;
@@ -723,7 +725,6 @@ qpu_merge_inst(const struct v3d_device_info *devinfo,
 static struct schedule_node *
 choose_instruction_to_schedule(const struct v3d_device_info *devinfo,
                                struct choose_scoreboard *scoreboard,
-                               struct list_head *schedule_list,
                                struct schedule_node *prev_inst)
 {
         struct schedule_node *chosen = NULL;
@@ -737,7 +738,8 @@ choose_instruction_to_schedule(const struct v3d_device_info *devinfo,
                         return NULL;
         }
 
-        list_for_each_entry(struct schedule_node, n, schedule_list, link) {
+        list_for_each_entry(struct schedule_node, n, &scoreboard->dag->heads,
+                            dag.link) {
                 const struct v3d_qpu_instr *inst = &n->inst->qpu;
 
                 /* Don't choose the branch instruction until it's the last one
@@ -745,7 +747,7 @@ choose_instruction_to_schedule(const struct v3d_device_info *devinfo,
                  * choose it.
                  */
                 if (inst->type == V3D_QPU_INSTR_TYPE_BRANCH &&
-                    !list_is_singular(schedule_list)) {
+                    !list_is_singular(&scoreboard->dag->heads)) {
                         continue;
                 }
 
@@ -771,6 +773,12 @@ choose_instruction_to_schedule(const struct v3d_device_info *devinfo,
                  * sooner.  If the ldvary's r5 wasn't used, then ldunif might
                  * otherwise get scheduled so ldunif and ldvary try to update
                  * r5 in the same tick.
+                 *
+                 * XXX perf: To get good pipelining of a sequence of varying
+                 * loads, we need to figure out how to pair the ldvary signal
+                 * up to the instruction before the last r5 user in the
+                 * previous ldvary sequence.  Currently, it usually pairs with
+                 * the last r5 user.
                  */
                 if ((inst->sig.ldunif || inst->sig.ldunifa) &&
                     scoreboard->tick == scoreboard->last_ldvary_tick + 1) {
@@ -840,16 +848,13 @@ update_scoreboard_for_magic_waddr(struct choose_scoreboard *scoreboard,
                                   enum v3d_qpu_waddr waddr)
 {
         if (v3d_qpu_magic_waddr_is_sfu(waddr))
-                scoreboard->last_sfu_write_tick = scoreboard->tick;
+                scoreboard->last_magic_sfu_write_tick = scoreboard->tick;
 }
 
 static void
 update_scoreboard_for_chosen(struct choose_scoreboard *scoreboard,
                              const struct v3d_qpu_instr *inst)
 {
-        scoreboard->last_waddr_add = ~0;
-        scoreboard->last_waddr_mul = ~0;
-
         if (inst->type == V3D_QPU_INSTR_TYPE_BRANCH)
                 return;
 
@@ -859,8 +864,6 @@ update_scoreboard_for_chosen(struct choose_scoreboard *scoreboard,
                 if (inst->alu.add.magic_write) {
                         update_scoreboard_for_magic_waddr(scoreboard,
                                                           inst->alu.add.waddr);
-                } else {
-                        scoreboard->last_waddr_add = inst->alu.add.waddr;
                 }
         }
 
@@ -868,8 +871,6 @@ update_scoreboard_for_chosen(struct choose_scoreboard *scoreboard,
                 if (inst->alu.mul.magic_write) {
                         update_scoreboard_for_magic_waddr(scoreboard,
                                                           inst->alu.mul.waddr);
-                } else {
-                        scoreboard->last_waddr_mul = inst->alu.mul.waddr;
                 }
         }
 
@@ -881,24 +882,24 @@ update_scoreboard_for_chosen(struct choose_scoreboard *scoreboard,
 }
 
 static void
-dump_state(const struct v3d_device_info *devinfo,
-           struct list_head *schedule_list)
+dump_state(const struct v3d_device_info *devinfo, struct dag *dag)
 {
-        list_for_each_entry(struct schedule_node, n, schedule_list, link) {
+        list_for_each_entry(struct schedule_node, n, &dag->heads, dag.link) {
                 fprintf(stderr, "         t=%4d: ", n->unblocked_time);
                 v3d_qpu_dump(devinfo, &n->inst->qpu);
                 fprintf(stderr, "\n");
 
-                for (int i = 0; i < n->child_count; i++) {
-                        struct schedule_node *child = n->children[i].node;
+                util_dynarray_foreach(&n->dag.edges, struct dag_edge, edge) {
+                        struct schedule_node *child =
+                                (struct schedule_node *)edge->child;
                         if (!child)
                                 continue;
 
                         fprintf(stderr, "                 - ");
                         v3d_qpu_dump(devinfo, &child->inst->qpu);
                         fprintf(stderr, " (%d parents, %c)\n",
-                                child->parent_count,
-                                n->children[i].write_after_read ? 'w' : 'r');
+                                child->dag.parent_count,
+                                edge->data ? 'w' : 'r');
                 }
         }
 }
@@ -929,7 +930,7 @@ static uint32_t magic_waddr_latency(enum v3d_qpu_waddr waddr,
          *
          * because we associate the first load_tmu0 with the *second* tmu0_s.
          */
-        if (v3d_qpu_magic_waddr_is_tmu(waddr) && after->sig.ldtmu)
+        if (v3d_qpu_magic_waddr_is_tmu(waddr) && v3d_qpu_waits_on_tmu(after))
                 return 100;
 
         /* Assume that anything depending on us is consuming the SFU result. */
@@ -967,59 +968,56 @@ instruction_latency(struct schedule_node *before, struct schedule_node *after)
 
 /** Recursive computation of the delay member of a node. */
 static void
-compute_delay(struct schedule_node *n)
+compute_delay(struct dag_node *node, void *state)
 {
-        if (!n->child_count) {
-                n->delay = 1;
-        } else {
-                for (int i = 0; i < n->child_count; i++) {
-                        if (!n->children[i].node->delay)
-                                compute_delay(n->children[i].node);
-                        n->delay = MAX2(n->delay,
-                                        n->children[i].node->delay +
-                                        instruction_latency(n, n->children[i].node));
-                }
+        struct schedule_node *n = (struct schedule_node *)node;
+
+        n->delay = 1;
+
+        util_dynarray_foreach(&n->dag.edges, struct dag_edge, edge) {
+                struct schedule_node *child =
+                        (struct schedule_node *)edge->child;
+
+                n->delay = MAX2(n->delay, (child->delay +
+                                           instruction_latency(n, child)));
         }
 }
 
+/* Removes a DAG head, but removing only the WAR edges. (dag_prune_head()
+ * should be called on it later to finish pruning the other edges).
+ */
 static void
-mark_instruction_scheduled(struct list_head *schedule_list,
+pre_remove_head(struct dag *dag, struct schedule_node *n)
+{
+        list_delinit(&n->dag.link);
+
+        util_dynarray_foreach(&n->dag.edges, struct dag_edge, edge) {
+                if (edge->data)
+                        dag_remove_edge(dag, edge);
+        }
+}
+
+static void
+mark_instruction_scheduled(struct dag *dag,
                            uint32_t time,
-                           struct schedule_node *node,
-                           bool war_only)
+                           struct schedule_node *node)
 {
         if (!node)
                 return;
 
-        for (int i = node->child_count - 1; i >= 0; i--) {
+        util_dynarray_foreach(&node->dag.edges, struct dag_edge, edge) {
                 struct schedule_node *child =
-                        node->children[i].node;
+                        (struct schedule_node *)edge->child;
 
                 if (!child)
                         continue;
 
-                if (war_only && !node->children[i].write_after_read)
-                        continue;
-
-                /* If the requirement is only that the node not appear before
-                 * the last read of its destination, then it can be scheduled
-                 * immediately after (or paired with!) the thing reading the
-                 * destination.
-                 */
-                uint32_t latency = 0;
-                if (!war_only) {
-                        latency = instruction_latency(node,
-                                                      node->children[i].node);
-                }
+                uint32_t latency = instruction_latency(node, child);
 
                 child->unblocked_time = MAX2(child->unblocked_time,
                                              time + latency);
-                child->parent_count--;
-                if (child->parent_count == 0)
-                        list_add(&child->link, schedule_list);
-
-                node->children[i].node = NULL;
         }
+        dag_prune_head(dag, &node->dag);
 }
 
 static void
@@ -1038,7 +1036,7 @@ insert_scheduled_instruction(struct v3d_compile *c,
 static struct qinst *
 vir_nop()
 {
-        struct qreg undef = { QFILE_NULL, 0 };
+        struct qreg undef = vir_nop_reg();
         struct qinst *qinst = vir_add_inst(V3D_QPU_A_NOP, undef, undef, undef);
 
         return qinst;
@@ -1073,6 +1071,10 @@ qpu_instruction_valid_in_thrend_slot(struct v3d_compile *c,
                 return false;
 
         if (inst->type == V3D_QPU_INSTR_TYPE_ALU) {
+                /* GFXH-1625: TMUWT not allowed in the final instruction. */
+                if (slot == 2 && inst->alu.add.op == V3D_QPU_A_TMUWT)
+                        return false;
+
                 /* No writing physical registers at the end. */
                 if (!inst->alu.add.magic_write ||
                     !inst->alu.mul.magic_write) {
@@ -1107,10 +1109,16 @@ qpu_instruction_valid_in_thrend_slot(struct v3d_compile *c,
 }
 
 static bool
-valid_thrsw_sequence(struct v3d_compile *c,
+valid_thrsw_sequence(struct v3d_compile *c, struct choose_scoreboard *scoreboard,
                      struct qinst *qinst, int instructions_in_sequence,
                      bool is_thrend)
 {
+        /* No emitting our thrsw while the previous thrsw hasn't happened yet. */
+        if (scoreboard->last_thrsw_tick + 3 >
+            scoreboard->tick - instructions_in_sequence) {
+                return false;
+        }
+
         for (int slot = 0; slot < instructions_in_sequence; slot++) {
                 /* No scheduling SFU when the result would land in the other
                  * thread.  The simulator complains for safety, though it
@@ -1171,7 +1179,8 @@ emit_thrsw(struct v3d_compile *c,
                 if (!v3d_qpu_sig_pack(c->devinfo, &sig, &packed_sig))
                         break;
 
-                if (!valid_thrsw_sequence(c, prev_inst, slots_filled + 1,
+                if (!valid_thrsw_sequence(c, scoreboard,
+                                          prev_inst, slots_filled + 1,
                                           is_thrend)) {
                         break;
                 }
@@ -1185,7 +1194,9 @@ emit_thrsw(struct v3d_compile *c,
         if (merge_inst) {
                 merge_inst->qpu.sig.thrsw = true;
                 needs_free = true;
+                scoreboard->last_thrsw_tick = scoreboard->tick - slots_filled;
         } else {
+                scoreboard->last_thrsw_tick = scoreboard->tick;
                 insert_scheduled_instruction(c, block, scoreboard, inst);
                 time++;
                 slots_filled++;
@@ -1220,7 +1231,6 @@ static uint32_t
 schedule_instructions(struct v3d_compile *c,
                       struct choose_scoreboard *scoreboard,
                       struct qblock *block,
-                      struct list_head *schedule_list,
                       enum quniform_contents *orig_uniform_contents,
                       uint32_t *orig_uniform_data,
                       uint32_t *next_uniform)
@@ -1228,23 +1238,10 @@ schedule_instructions(struct v3d_compile *c,
         const struct v3d_device_info *devinfo = c->devinfo;
         uint32_t time = 0;
 
-        if (debug) {
-                fprintf(stderr, "initial deps:\n");
-                dump_state(devinfo, schedule_list);
-                fprintf(stderr, "\n");
-        }
-
-        /* Remove non-DAG heads from the list. */
-        list_for_each_entry_safe(struct schedule_node, n, schedule_list, link) {
-                if (n->parent_count != 0)
-                        list_del(&n->link);
-        }
-
-        while (!list_empty(schedule_list)) {
+        while (!list_empty(&scoreboard->dag->heads)) {
                 struct schedule_node *chosen =
                         choose_instruction_to_schedule(devinfo,
                                                        scoreboard,
-                                                       schedule_list,
                                                        NULL);
                 struct schedule_node *merge = NULL;
 
@@ -1257,7 +1254,7 @@ schedule_instructions(struct v3d_compile *c,
                 if (debug) {
                         fprintf(stderr, "t=%4d: current list:\n",
                                 time);
-                        dump_state(devinfo, schedule_list);
+                        dump_state(devinfo, scoreboard->dag);
                         fprintf(stderr, "t=%4d: chose:   ", time);
                         v3d_qpu_dump(devinfo, inst);
                         fprintf(stderr, "\n");
@@ -1275,17 +1272,14 @@ schedule_instructions(struct v3d_compile *c,
                  */
                 if (chosen) {
                         time = MAX2(chosen->unblocked_time, time);
-                        list_del(&chosen->link);
-                        mark_instruction_scheduled(schedule_list, time,
-                                                   chosen, true);
+                        pre_remove_head(scoreboard->dag, chosen);
 
                         while ((merge =
                                 choose_instruction_to_schedule(devinfo,
                                                                scoreboard,
-                                                               schedule_list,
                                                                chosen))) {
                                 time = MAX2(merge->unblocked_time, time);
-                                list_del(&merge->link);
+                                pre_remove_head(scoreboard->dag, chosen);
                                 list_addtail(&merge->link, &merged_list);
                                 (void)qpu_merge_inst(devinfo, inst,
                                                      inst, &merge->inst->qpu);
@@ -1331,11 +1325,10 @@ schedule_instructions(struct v3d_compile *c,
                  * be scheduled.  Update the children's unblocked time for this
                  * DAG edge as we do so.
                  */
-                mark_instruction_scheduled(schedule_list, time, chosen, false);
+                mark_instruction_scheduled(scoreboard->dag, time, chosen);
                 list_for_each_entry(struct schedule_node, merge, &merged_list,
                                     link) {
-                        mark_instruction_scheduled(schedule_list, time, merge,
-                                                   false);
+                        mark_instruction_scheduled(scoreboard->dag, time, merge);
 
                         /* The merged VIR instruction doesn't get re-added to the
                          * block, so free it now.
@@ -1377,9 +1370,10 @@ qpu_schedule_instructions_block(struct v3d_compile *c,
                                 uint32_t *next_uniform)
 {
         void *mem_ctx = ralloc_context(NULL);
-        struct list_head schedule_list;
+        scoreboard->dag = dag_create(mem_ctx);
+        struct list_head setup_list;
 
-        list_inithead(&schedule_list);
+        list_inithead(&setup_list);
 
         /* Wrap each instruction in a scheduler structure. */
         while (!list_empty(&block->instructions)) {
@@ -1387,26 +1381,25 @@ qpu_schedule_instructions_block(struct v3d_compile *c,
                 struct schedule_node *n =
                         rzalloc(mem_ctx, struct schedule_node);
 
+                dag_init_node(scoreboard->dag, &n->dag);
                 n->inst = qinst;
 
                 list_del(&qinst->link);
-                list_addtail(&n->link, &schedule_list);
+                list_addtail(&n->link, &setup_list);
         }
 
-        calculate_forward_deps(c, &schedule_list);
-        calculate_reverse_deps(c, &schedule_list);
+        calculate_forward_deps(c, scoreboard->dag, &setup_list);
+        calculate_reverse_deps(c, scoreboard->dag, &setup_list);
 
-        list_for_each_entry(struct schedule_node, n, &schedule_list, link) {
-                compute_delay(n);
-        }
+        dag_traverse_bottom_up(scoreboard->dag, compute_delay, NULL);
 
         uint32_t cycles = schedule_instructions(c, scoreboard, block,
-                                                &schedule_list,
                                                 orig_uniform_contents,
                                                 orig_uniform_data,
                                                 next_uniform);
 
         ralloc_free(mem_ctx);
+        scoreboard->dag = NULL;
 
         return cycles;
 }
@@ -1484,11 +1477,10 @@ v3d_qpu_schedule_instructions(struct v3d_compile *c)
 
         struct choose_scoreboard scoreboard;
         memset(&scoreboard, 0, sizeof(scoreboard));
-        scoreboard.last_waddr_add = ~0;
-        scoreboard.last_waddr_mul = ~0;
         scoreboard.last_ldvary_tick = -10;
-        scoreboard.last_sfu_write_tick = -10;
+        scoreboard.last_magic_sfu_write_tick = -10;
         scoreboard.last_uniforms_reset_tick = -10;
+        scoreboard.last_thrsw_tick = -10;
 
         if (debug) {
                 fprintf(stderr, "Pre-schedule instructions\n");