From 04236b39124264d6b9d969de6cfefbe35ad6b598 Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com>
Date: Wed, 27 May 2026 09:41:29 -0400
Subject: [PATCH] jay: merge partition blocks

The way we construct partitions, it is tricky to avoid empty blocks sometimes
leading to mergeable adjacent blocks. Simplify this at runtime.

Stats are kind of a mixed bag but this is the obvious right thing to do.

simd16:

   Totals:
   Instrs: 2752919 -> 2752284 (-0.02%); split: -0.03%, +0.01%
   CodeSize: 41105312 -> 41096640 (-0.02%); split: -0.03%, +0.01%

   Totals from 236 (8.92% of 2647) affected shaders:
   Instrs: 740015 -> 739380 (-0.09%); split: -0.12%, +0.04%
   CodeSize: 11076496 -> 11067824 (-0.08%); split: -0.11%, +0.04%

simd32:

   Totals:
   Instrs: 4121085 -> 4121638 (+0.01%); split: -0.01%, +0.02%
   CodeSize: 61394672 -> 61404720 (+0.02%); split: -0.00%, +0.02%

   Totals from 145 (5.48% of 2647) affected shaders:
   Instrs: 1104897 -> 1105450 (+0.05%); split: -0.02%, +0.07%
   CodeSize: 16845728 -> 16855776 (+0.06%); split: -0.02%, +0.08%

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41808>
---
 src/intel/compiler/jay/jay_partition.c | 49 +++++++++++++++++---------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/src/intel/compiler/jay/jay_partition.c b/src/intel/compiler/jay/jay_partition.c
index 6d489f42170..629d22a1795 100644
--- a/src/intel/compiler/jay/jay_partition.c
+++ b/src/intel/compiler/jay/jay_partition.c
@@ -36,25 +36,42 @@ build_partition(jay_shader *shader, struct jay_partition_builder *b, unsigned n)
       .units_x16[MEM] = 16 / jay_grf_per_gpr(shader),
    };
 
+   /* Drop empty blocks and merge the resulting neighbours. This avoids needless
+    * partition boundaries that would unnecessarily constrain RA, while allowing
+    * the caller the convenience of passing in holes sometimes.
+    */
+   signed j = -1;
    for (unsigned i = 0; i < n; ++i) {
-      if (b[i].len_grf) {
-         enum jay_file file = b[i].file;
-         unsigned len_gpr = (b[i].len_grf * p->units_x16[file]) / 16;
-         bool grf = file < JAY_NUM_GRF_FILES;
-         assert(p->nr_blocks[file] < JAY_PARTITION_BLOCKS);
+      struct jay_partition_builder B = b[i];
+      if (j >= 0 &&
+          B.file == b[j].file &&
+          B.stride == b[j].stride &&
+          B.type == b[j].type) {
 
-         p->blocks[file][p->nr_blocks[file]++] = (struct jay_register_block) {
-            .start_grf = grf ? base_grf : 0,
-            .start_gpr = base_gpr[file],
-            .len_gpr = (b[i].len_grf * p->units_x16[file]) / 16,
-            .stride = b[i].stride,
-            .type = b[i].type,
-         };
+         b[j].len_grf += B.len_grf;
+      } else if (B.len_grf) {
+         b[++j] = B;
+      }
+   }
 
-         if (file < JAY_NUM_GRF_FILES) {
-            base_grf += b[i].len_grf;
-            base_gpr[file] += len_gpr;
-         }
+   /* Translate to jay_register_block */
+   for (signed i = 0; i <= j; ++i) {
+      enum jay_file file = b[i].file;
+      unsigned len_gpr = (b[i].len_grf * p->units_x16[file]) / 16;
+      bool grf = file < JAY_NUM_GRF_FILES;
+      assert(p->nr_blocks[file] < JAY_PARTITION_BLOCKS);
+
+      p->blocks[file][p->nr_blocks[file]++] = (struct jay_register_block) {
+         .start_grf = grf ? base_grf : 0,
+         .start_gpr = base_gpr[file],
+         .len_gpr = (b[i].len_grf * p->units_x16[file]) / 16,
+         .stride = b[i].stride,
+         .type = b[i].type,
+      };
+
+      if (file < JAY_NUM_GRF_FILES) {
+         base_grf += b[i].len_grf;
+         base_gpr[file] += len_gpr;
       }
    }