pco: add helpers for finding non-empty blocks, apply

Signed-off-by: Simon Perretta <simon.perretta@imgtec.com>
Acked-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36412>

src/imagination/pco/pco_internal.h

@@ -1351,6 +1351,42 @@ PCO_DEFINE_CF_ITER(loop, PCO_CF_NODE_TYPE_LOOP)
 
 #undef PCO_DEFINE_CF_ITER
 
+/**
+ * \brief Returns the next non-empty block.
+ *
+ * \param[in] block The current block.
+ * \return The next non-empty block, or NULL if the end of the function has been
+ *         reached.
+ */
+static inline pco_block *pco_next_block_nonempty(pco_block *block)
+{
+   block = pco_next_block(block);
+
+   /* Skip over empty blocks. */
+   while (block && exec_list_is_empty(&block->instrs))
+      block = pco_next_block(block);
+
+   return block;
+}
+
+/**
+ * \brief Returns the previous non-empty block.
+ *
+ * \param[in] block The current block.
+ * \return The previous non-empty block, or NULL if the end of the function has
+ *         been reached.
+ */
+static inline pco_block *pco_prev_block_nonempty(pco_block *block)
+{
+   block = pco_prev_block(block);
+
+   /* Skip over empty blocks. */
+   while (block && exec_list_is_empty(&block->instrs))
+      block = pco_prev_block(block);
+
+   return block;
+}
+
 /**
  * \brief Returns the first instruction in a block.
  *
@@ -1389,12 +1425,7 @@ static inline pco_instr *pco_next_instr(pco_instr *instr)
    if (next_instr)
       return next_instr;
 
-   pco_block *block = pco_next_block(instr->parent_block);
-
-   /* Skip over empty blocks. */
-   while (block && exec_list_is_empty(&block->instrs))
-      block = pco_next_block(block);
-
+   pco_block *block = pco_next_block_nonempty(instr->parent_block);
    return !block ? NULL : pco_first_instr(block);
 }
 
@@ -1414,12 +1445,7 @@ static inline pco_instr *pco_prev_instr(pco_instr *instr)
    if (prev_instr)
       return prev_instr;
 
-   pco_block *block = pco_prev_block(instr->parent_block);
-
-   /* Skip over empty blocks. */
-   while (block && exec_list_is_empty(&block->instrs))
-      block = pco_prev_block(block);
-
+   pco_block *block = pco_prev_block_nonempty(instr->parent_block);
    return !block ? NULL : pco_last_instr(block);
 }
 

src/imagination/pco/pco_trans_nir.c

@@ -1536,6 +1536,12 @@ static unsigned try_collate_vec_srcs(trans_ctx *tctx,
    bool collated_vector = false;
    unsigned num_srcs_collated = 0;
    pco_instr *from = pco_cursor_instr(tctx->b.cursor);
+   if (!from) {
+      from = pco_last_instr(
+         pco_prev_block_nonempty(pco_cursor_block(tctx->b.cursor)));
+   }
+
+   assert(from);
 
    for (unsigned s = 0; s < num_srcs; ++s) {
       pco_instr *parent_instr = find_parent_instr_from(src[s], from);