lima: ppir: add compactification pass

If we have a single instruction that uses only combiner unit and previous
instruction doesn't use this unit, two instructions can be safely merged.

Implement compactification pass to do that.

The pass doesn't update instruction dependencies, so it should be run
right before codegen.

Reviewed-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33570>

src/gallium/drivers/lima/ir/pp/compact.c

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2025 Lima Project
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sub license,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#include "ppir.h"
+
+static bool instr_has_single_slot(ppir_instr *instr)
+{
+   int count = 0;
+   for (int i = 0; i < PPIR_INSTR_SLOT_NUM; i++) {
+      if (instr->slots[i])
+         count++;
+   }
+
+   if (instr->constant[0].num || instr->constant[1].num)
+      count++;
+
+   return count == 1;
+}
+
+bool ppir_compact_prog(ppir_compiler *comp)
+{
+   list_for_each_entry(ppir_block, block, &comp->block_list, list) {
+      /* Walk block in reverse order.
+       * If current instruction have a single instruction in combiner,
+       * try moving it into previous instruction.
+       */
+      ppir_instr *next_instr = NULL;
+      ppir_node *node = NULL;
+      list_for_each_entry_safe_rev(ppir_instr, instr, &block->instr_list, list) {
+         if (node && !instr->slots[PPIR_INSTR_SLOT_ALU_COMBINE]) {
+            instr->slots[node->instr_pos] = node;
+            list_del(&next_instr->list);
+            comp->cur_instr_index--;
+         }
+         node = NULL;
+         if (instr_has_single_slot(instr)) {
+            if (instr->slots[PPIR_INSTR_SLOT_ALU_COMBINE]) {
+               node = instr->slots[PPIR_INSTR_SLOT_ALU_COMBINE];
+               break;
+            }
+         }
+         next_instr = instr;
+      }
+   }
+
+   return true;
+}

src/gallium/drivers/lima/ir/pp/nir.c

@@ -1090,6 +1090,10 @@ bool ppir_compile_nir(struct lima_fs_compiled_shader *prog, struct nir_shader *n
    if (!ppir_regalloc_prog(comp))
       goto err_out0;
 
+   /* all the deps are invalid after compacting */
+   if (!ppir_compact_prog(comp))
+      goto err_out0;
+
    if (!ppir_codegen_prog(comp))
       goto err_out0;
 

src/gallium/drivers/lima/ir/pp/ppir.h

@@ -772,6 +772,7 @@ bool ppir_lower_prog(ppir_compiler *comp);
 bool ppir_node_to_instr(ppir_compiler *comp);
 bool ppir_schedule_prog(ppir_compiler *comp);
 bool ppir_regalloc_prog(ppir_compiler *comp);
+bool ppir_compact_prog(ppir_compiler *comp);
 bool ppir_codegen_prog(ppir_compiler *comp);
 void ppir_liveness_analysis(ppir_compiler *comp);
 bool ppir_opt_prog(ppir_compiler *comp);

src/gallium/drivers/lima/meson.build

@@ -28,6 +28,7 @@ files_lima = files(
   'ir/pp/node_to_instr.c',
   'ir/pp/disasm.c',
   'ir/pp/opt.c',
+  'ir/pp/compact.c',
 
   'ir/lima_nir_duplicate_consts.c',
   'ir/lima_nir_duplicate_intrinsic.c',