From 7eba054c5ba82b8a2366e5a340ec0b6376cc314c Mon Sep 17 00:00:00 2001
From: Christoph Neuhauser <christoph.neuhauser@intel.com>
Date: Mon, 18 May 2026 19:42:26 +0200
Subject: [PATCH] anv: Add compute only divergent atomics fusion optimization
 for Blender Blender uses atomic operations as part of its virtual shadow
 mapping implementation. Virtual shadow mapping page tagging in compute
 shaders benefits from divergent atomics fusion, while fragment shaders doing
 the atomic raster step in general have worse performance with this
 optimization turned on. Thus, an option is added to only apply divergent
 atomics fusion to compute shaders in ANV, and this option is enabled for
 Blender.

Initial support for divergent atomics fusion optimization in ANV was added
in https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40631.

Signed-off-by: Christoph Neuhauser <christoph.neuhauser@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41706>
---
 src/intel/vulkan/anv_instance.c       | 3 +++
 src/intel/vulkan/anv_private.h        | 1 +
 src/intel/vulkan/anv_shader_compile.c | 7 +++++++
 src/util/00-mesa-defaults.conf        | 7 +++++++
 src/util/driconf.h                    | 4 ++++
 5 files changed, 22 insertions(+)

diff --git a/src/intel/vulkan/anv_instance.c b/src/intel/vulkan/anv_instance.c
index 431e724643f..8fe85d7e1e2 100644
--- a/src/intel/vulkan/anv_instance.c
+++ b/src/intel/vulkan/anv_instance.c
@@ -43,6 +43,7 @@ static const driOptionDescription anv_dri_options[] = {
       DRI_CONF_ANV_FORCE_INDIRECT_DESCRIPTORS(false)
       DRI_CONF_ANV_DISABLE_LINK_TIME_OPTIMIZATION(false)
       DRI_CONF_ANV_ENABLE_OPT_DIVERGENT_ATOMICS(0)
+      DRI_CONF_ANV_ENABLE_OPT_DIVERGENT_ATOMICS_COMPUTE_ONLY(0)
       DRI_CONF_ANV_BRW_DISABLE_SUBGROUP_SIZE_CONTROL(false)
       DRI_CONF_SHADER_SPILLING_RATE(11)
       DRI_CONFIG_INTEL_FORCE_COMPUTE_SURFACE_PREFETCH(true)
@@ -318,6 +319,8 @@ anv_init_dri_options(struct anv_instance *instance)
         driQueryOptionb(&instance->dri_options, "anv_disable_link_time_optimization");
     instance->enable_opt_divergent_atomics =
         driQueryOptioni(&instance->dri_options, "anv_enable_opt_divergent_atomics");
+    instance->enable_opt_divergent_atomics_compute_only =
+        driQueryOptioni(&instance->dri_options, "anv_enable_opt_divergent_atomics_compute_only");
 
     instance->stack_ids = driQueryOptioni(&instance->dri_options, "intel_stack_id");
     switch (instance->stack_ids) {
diff --git a/src/intel/vulkan/anv_private.h b/src/intel/vulkan/anv_private.h
index c39695398a3..4f632340ac3 100644
--- a/src/intel/vulkan/anv_private.h
+++ b/src/intel/vulkan/anv_private.h
@@ -1813,6 +1813,7 @@ struct anv_instance {
     bool                                        disable_lto;
     bool                                        disable_push_constant_alloc;
     enum brw_divergent_atomics_flags            enable_opt_divergent_atomics;
+    enum brw_divergent_atomics_flags            enable_opt_divergent_atomics_compute_only;
     bool                                        force_sampler_prefetch;
     bool                                        force_compute_surface_prefetch;
     unsigned                                    generated_indirect_threshold;
diff --git a/src/intel/vulkan/anv_shader_compile.c b/src/intel/vulkan/anv_shader_compile.c
index c2422110562..498d7e3ac89 100644
--- a/src/intel/vulkan/anv_shader_compile.c
+++ b/src/intel/vulkan/anv_shader_compile.c
@@ -665,7 +665,14 @@ populate_cs_prog_key(struct brw_cs_prog_key *key,
                      const struct vk_physical_device *device,
                      const struct vk_pipeline_robustness_state *rs)
 {
+
+   const struct anv_physical_device *pdevice =
+      container_of(device, const struct anv_physical_device, vk);
+
    populate_base_prog_key(&key->base, device, rs);
+
+   key->base.divergent_atomics_flags |=
+      pdevice->instance->enable_opt_divergent_atomics_compute_only;
 }
 
 static void
diff --git a/src/util/00-mesa-defaults.conf b/src/util/00-mesa-defaults.conf
index 53a0e46f2f3..544517e0505 100644
--- a/src/util/00-mesa-defaults.conf
+++ b/src/util/00-mesa-defaults.conf
@@ -1157,6 +1157,13 @@ TODO: document the other workarounds.
             -->
             <option name="anv_barrier_post_untyped_clear_shader" value="true" />
         </application>
+        <application name="Blender" executable="blender">
+            <!-- Virtual shadow mapping page tagging in compute shaders
+                 benefits from divergent atomics fusion, while fragment
+                 shaders doing the atomic raster step in general have worse
+                 performance with this optimization turned on. -->
+            <option name="anv_enable_opt_divergent_atomics_compute_only" value="1" />
+        </application>
         <!-- Source2 games seem confused by the CCS-only memory type being
              restricted to images, so allow it for buffers. More details on
              the issue:
diff --git a/src/util/driconf.h b/src/util/driconf.h
index a3289c202bc..4d53abfffd0 100644
--- a/src/util/driconf.h
+++ b/src/util/driconf.h
@@ -980,6 +980,10 @@
    DRI_CONF_OPT_I(anv_enable_opt_divergent_atomics, def, 0, 3,\
                   "Enable fusion of divergent atomics (see brw_divergent_atomics_flags)")
 
+#define DRI_CONF_ANV_ENABLE_OPT_DIVERGENT_ATOMICS_COMPUTE_ONLY(def) \
+   DRI_CONF_OPT_I(anv_enable_opt_divergent_atomics_compute_only, def, 0, 3,\
+                  "Enable fusion of divergent atomics for compute shaders only (see brw_divergent_atomics_flags)")
+
 #define DRI_CONF_ANV_BRW_DISABLE_SUBGROUP_SIZE_CONTROL(def) \
    DRI_CONF_OPT_B(anv_brw_disable_subgroup_size_control, def, \
                   "Disable EXT_subgroup_size_control support when using brw compiler.")