ir3: Calculate physical edges correctly

A block can have more than one extra physical successor, a fact that I
missed initially. Now that we've fixed up RA to handle it, we can
finally handle this correctly.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22072>

src/freedreno/ir3/ir3.c

@@ -515,10 +515,11 @@ ir3_block_add_predecessor(struct ir3_block *block, struct ir3_block *pred)
 }
 
 void
-ir3_block_add_physical_predecessor(struct ir3_block *block,
-                                   struct ir3_block *pred)
+ir3_block_link_physical(struct ir3_block *pred,
+                        struct ir3_block *succ)
 {
-   array_insert(block, block->physical_predecessors, pred);
+   array_insert(pred, pred->physical_successors, succ);
+   array_insert(succ, succ->physical_predecessors, pred);
 }
 
 void
@@ -537,22 +538,6 @@ ir3_block_remove_predecessor(struct ir3_block *block, struct ir3_block *pred)
    }
 }
 
-void
-ir3_block_remove_physical_predecessor(struct ir3_block *block, struct ir3_block *pred)
-{
-   for (unsigned i = 0; i < block->physical_predecessors_count; i++) {
-      if (block->physical_predecessors[i] == pred) {
-         if (i < block->physical_predecessors_count - 1) {
-            block->physical_predecessors[i] =
-               block->physical_predecessors[block->physical_predecessors_count - 1];
-         }
-
-         block->physical_predecessors_count--;
-         return;
-      }
-   }
-}
-
 unsigned
 ir3_block_get_pred_index(struct ir3_block *block, struct ir3_block *pred)
 {

src/freedreno/ir3/ir3.h

@@ -653,10 +653,10 @@ struct ir3_block {
     */
    struct ir3_instruction *condition;
    struct ir3_block *successors[2];
-   struct ir3_block *physical_successors[2];
 
    DECLARE_ARRAY(struct ir3_block *, predecessors);
    DECLARE_ARRAY(struct ir3_block *, physical_predecessors);
+   DECLARE_ARRAY(struct ir3_block *, physical_successors);
 
    uint16_t start_ip, end_ip;
 
@@ -724,12 +724,9 @@ ir3_after_preamble(struct ir3 *ir)
 }
 
 void ir3_block_add_predecessor(struct ir3_block *block, struct ir3_block *pred);
-void ir3_block_add_physical_predecessor(struct ir3_block *block,
-                                        struct ir3_block *pred);
+void ir3_block_link_physical(struct ir3_block *pred, struct ir3_block *succ);
 void ir3_block_remove_predecessor(struct ir3_block *block,
                                   struct ir3_block *pred);
-void ir3_block_remove_physical_predecessor(struct ir3_block *block,
-                                           struct ir3_block *pred);
 unsigned ir3_block_get_pred_index(struct ir3_block *block,
                                   struct ir3_block *pred);
 

src/freedreno/ir3/ir3_compiler_nir.c

@@ -3647,7 +3647,6 @@ emit_block(struct ir3_context *ctx, nir_block *nblock)
       if (nblock->successors[i]) {
          ctx->block->successors[i] =
             get_block_or_continue(ctx, nblock->successors[i]);
-         ctx->block->physical_successors[i] = ctx->block->successors[i];
       }
    }
 
@@ -3687,20 +3686,6 @@ emit_if(struct ir3_context *ctx, nir_if *nif)
 
    emit_cf_list(ctx, &nif->then_list);
    emit_cf_list(ctx, &nif->else_list);
-
-   struct ir3_block *last_then = get_block(ctx, nir_if_last_then_block(nif));
-   struct ir3_block *first_else = get_block(ctx, nir_if_first_else_block(nif));
-   assert(last_then->physical_successors[0] &&
-          !last_then->physical_successors[1]);
-   last_then->physical_successors[1] = first_else;
-
-   struct ir3_block *last_else = get_block(ctx, nir_if_last_else_block(nif));
-   struct ir3_block *after_if =
-      get_block(ctx, nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node)));
-   assert(last_else->physical_successors[0] &&
-          !last_else->physical_successors[1]);
-   if (after_if != last_else->physical_successors[0])
-      last_else->physical_successors[1] = after_if;
 }
 
 static void
@@ -3728,7 +3713,6 @@ emit_loop(struct ir3_context *ctx, nir_loop *nloop)
    if (continue_blk) {
       struct ir3_block *start = get_block(ctx, nstart);
       continue_blk->successors[0] = start;
-      continue_blk->physical_successors[0] = start;
       continue_blk->loop_id = ctx->loop_id;
       continue_blk->loop_depth = ctx->loop_depth;
       list_addtail(&continue_blk->node, &ctx->ir->block_list);
@@ -3814,13 +3798,8 @@ emit_stream_out(struct ir3_context *ctx)
    orig_end_block->successors[0] = stream_out_block;
    orig_end_block->successors[1] = new_end_block;
 
-   orig_end_block->physical_successors[0] = stream_out_block;
-   orig_end_block->physical_successors[1] = new_end_block;
-
    stream_out_block->successors[0] = new_end_block;
 
-   stream_out_block->physical_successors[0] = new_end_block;
-
    /* setup 'if (vtxcnt < maxvtxcnt)' condition: */
    cond = ir3_CMPS_S(ctx->block, vtxcnt, 0, maxvtxcnt, 0);
    cond->dsts[0]->num = regid(REG_P0, 0);
@@ -3886,9 +3865,6 @@ setup_predecessors(struct ir3 *ir)
       for (int i = 0; i < ARRAY_SIZE(block->successors); i++) {
          if (block->successors[i])
             ir3_block_add_predecessor(block->successors[i], block);
-         if (block->physical_successors[i])
-            ir3_block_add_physical_predecessor(block->physical_successors[i],
-                                               block);
       }
    }
 }

src/freedreno/ir3/ir3_legalize.c

@@ -580,7 +580,7 @@ opt_jump(struct ir3 *ir)
       /* This pass destroys the physical CFG so don't keep it around to avoid
        * validation errors.
        */
-      block->physical_successors[0] = block->physical_successors[1] = NULL;
+      block->physical_successors_count = 0;
       block->physical_predecessors_count = 0;
 
       foreach_instr (instr, &block->instr_list) {

src/freedreno/ir3/ir3_lower_subgroups.c

@@ -22,6 +22,7 @@
  */
 
 #include "ir3.h"
+#include "util/ralloc.h"
 
 /* Lower several macro-instructions needed for shader subgroup support that
  * must be turned into if statements. We do this after RA and post-RA
@@ -178,18 +179,21 @@ split_block(struct ir3 *ir, struct ir3_block *before_block,
          replace_pred(after_block->successors[i], before_block, after_block);
    }
 
-   for (unsigned i = 0; i < ARRAY_SIZE(before_block->physical_successors);
-        i++) {
-      after_block->physical_successors[i] =
-         before_block->physical_successors[i];
-      if (after_block->physical_successors[i]) {
-         replace_physical_pred(after_block->physical_successors[i],
-                               before_block, after_block);
-      }
+   for (unsigned i = 0; i < before_block->physical_successors_count; i++) {
+      replace_physical_pred(before_block->physical_successors[i],
+                            before_block, after_block);
    }
 
+   ralloc_steal(after_block, before_block->physical_successors);
+   after_block->physical_successors = before_block->physical_successors;
+   after_block->physical_successors_sz = before_block->physical_successors_sz;
+   after_block->physical_successors_count =
+      before_block->physical_successors_count;
+
    before_block->successors[0] = before_block->successors[1] = NULL;
-   before_block->physical_successors[0] = before_block->physical_successors[1] = NULL;
+   before_block->physical_successors = NULL;
+   before_block->physical_successors_count = 0;
+   before_block->physical_successors_sz = 0;
 
    foreach_instr_from_safe (rem_instr, &instr->node,
                             &before_block->instr_list) {
@@ -204,20 +208,12 @@ split_block(struct ir3 *ir, struct ir3_block *before_block,
    return after_block;
 }
 
-static void
-link_blocks_physical(struct ir3_block *pred, struct ir3_block *succ,
-                     unsigned index)
-{
-   pred->physical_successors[index] = succ;
-   ir3_block_add_physical_predecessor(succ, pred);
-}
-
 static void
 link_blocks(struct ir3_block *pred, struct ir3_block *succ, unsigned index)
 {
    pred->successors[index] = succ;
    ir3_block_add_predecessor(succ, pred);
-   link_blocks_physical(pred, succ, index);
+   ir3_block_link_physical(pred, succ);
 }
 
 static struct ir3_block *
@@ -292,7 +288,7 @@ lower_instr(struct ir3 *ir, struct ir3_block **block, struct ir3_instruction *in
       header->brtype = IR3_BRANCH_GETONE;
 
       link_blocks(exit, after_block, 0);
-      link_blocks_physical(exit, footer, 1);
+      ir3_block_link_physical(exit, footer);
 
       link_blocks(footer, header, 0);
 

src/freedreno/ir3/ir3_print.c

@@ -560,13 +560,14 @@ print_block(struct ir3_block *block, int lvl)
       mesa_log_stream_printf(stream, "/* succs: block%u; */\n",
                              block_id(block->successors[0]));
    }
-   if (block->physical_successors[0]) {
+   if (block->physical_successors_count > 0) {
       tab(stream, lvl + 1);
-      mesa_log_stream_printf(stream, "/* physical succs: block%u",
-                             block_id(block->physical_successors[0]));
-      if (block->physical_successors[1]) {
-         mesa_log_stream_printf(stream, ", block%u",
-                                block_id(block->physical_successors[1]));
+      mesa_log_stream_printf(stream, "/* physical succs: ");
+      for (unsigned i = 0; i < block->physical_successors_count; i++) {
+         mesa_log_stream_printf(stream, "block%u",
+                                block_id(block->physical_successors[i]));
+         if (i < block->physical_successors_count - 1)
+            mesa_log_stream_printf(stream, ", ");
       }
       mesa_log_stream_printf(stream, " */\n");
    }

src/freedreno/ir3/ir3_ra_validate.c

@@ -477,10 +477,8 @@ propagate_block(struct ra_val_ctx *ctx, struct ir3_block *block)
       progress |=
          merge_state(ctx, &ctx->block_reaching[succ->index], &ctx->reaching);
    }
-   for (unsigned i = 0; i < 2; i++) {
+   for (unsigned i = 0; i < block->physical_successors_count; i++) {
       struct ir3_block *succ = block->physical_successors[i];
-      if (!succ)
-         continue;
       progress |= merge_state_physical(ctx, &ctx->block_reaching[succ->index],
                                        &ctx->reaching);
    }

src/freedreno/ir3/ir3_reconvergence.c

@@ -139,6 +139,8 @@ ir3_calc_reconvergence(struct ir3_shader_variant *so)
       blocks[block->index].first_processed_divergent_pred = UINT_MAX;
       for (unsigned i = 0; i < ARRAY_SIZE(block->successors); i++) {
          if (block->successors[i]) {
+            ir3_block_link_physical(block, block->successors[i]);
+
             if (block->successors[i]->index > block->index + 1) {
                edges[edge] = (struct logical_edge) {
                   .node = {
@@ -196,6 +198,7 @@ ir3_calc_reconvergence(struct ir3_shader_variant *so)
 
       /* Iterate over all edges stepping over the block. */
       struct uinterval interval = { block->index, block->index };
+      struct logical_edge *prev = NULL;
       uinterval_tree_foreach (struct logical_edge, edge, interval, &forward_edges,
                               node) {
          /* If "block" definitely isn't outstanding when the branch
@@ -249,6 +252,19 @@ ir3_calc_reconvergence(struct ir3_shader_variant *so)
                }
             }
          }
+
+         if (!prev || prev->start_block != edge->start_block) {
+            /* We should only process this edge + block combination once, and
+             * we use the fact that edges are sorted by start point to avoid
+             * adding redundant physical edges in case multiple edges have the
+             * same start point by comparing with the previous edge. Therefore
+             * we should only add the physical edge once.
+             */
+            for (unsigned i = 0; i < block->physical_predecessors_count; i++)
+               assert(block->physical_predecessors[i] != edge->start_block);
+            ir3_block_link_physical(edge->start_block, block);
+         }
+         prev = edge;
       }
 
       blocks[block->index].first_processed_divergent_pred =

src/freedreno/ir3/ir3_remove_unreachable.c

@@ -81,29 +81,6 @@ delete_block(struct ir3 *ir, struct ir3_block *block)
       }
       succ->predecessors_count--;
    }
-
-   for (unsigned i = 0; i < 2; i++) {
-      struct ir3_block *succ = block->physical_successors[i];
-      if (!succ)
-         continue;
-
-      ir3_block_remove_physical_predecessor(succ, block);
-   }
-
-   if (block->physical_predecessors_count != 0) {
-      /* There should be only one physical predecessor, for the fallthrough
-       * edge.
-       */
-      assert(block->physical_predecessors_count == 1);
-      struct ir3_block *pred = block->physical_predecessors[0];
-      assert(block->node.next != &ir->block_list);
-      struct ir3_block *next = list_entry(block->node.next, struct ir3_block, node);
-      if (pred->physical_successors[1] == block)
-         pred->physical_successors[1] = next;
-      else
-         pred->physical_successors[0] = next;
-      ir3_block_add_physical_predecessor(next, pred);
-   }
 }
 
 bool

src/freedreno/ir3/ir3_validate.c

@@ -372,7 +372,7 @@ validate_instr(struct ir3_validate_ctx *ctx, struct ir3_instruction *instr)
 static bool
 is_physical_successor(struct ir3_block *block, struct ir3_block *succ)
 {
-   for (unsigned i = 0; i < ARRAY_SIZE(block->physical_successors); i++)
+   for (unsigned i = 0; i < block->physical_successors_count; i++)
       if (block->physical_successors[i] == succ)
          return true;
    return false;
@@ -426,13 +426,12 @@ ir3_validate(struct ir3 *ir)
             ctx->current_instr = NULL;
 
             /* Each logical successor should also be a physical successor: */
-            if (block->physical_successors[0])
+            if (block->physical_successors_count > 0)
                validate_assert(ctx, is_physical_successor(block, block->successors[i]));
          }
       }
 
       validate_assert(ctx, block->successors[0] || !block->successors[1]);
-      validate_assert(ctx, block->physical_successors[0] || !block->physical_successors[1]);
    }
 
    ralloc_free(ctx);