Mesa (staging/21.1): radeonsi: don't create an infinite number of variants

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Module: Mesa
Branch: staging/21.1
Commit: e6c725a44be73e3b168cd5a475de104fcbbaf476
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e6c725a44be73e3b168cd5a475de104fcbbaf476

Author: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Date:   Fri Jul 30 11:48:28 2021 +0200

radeonsi: don't create an infinite number of variants

If a shader has code like this:

   uniform float timestamp;
   ...
   if (timestamp > 0.0)
      do_something()

And timestamp is modified each frame, we'll end up generating a new
variant per frame.

This commit introduces a hard limit on the number of variants we generate
for a single shader.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5121
Fixes: b7501184b90 ("radeonsi: implement inlinable uniforms")
Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12138>
(cherry picked from commit 9fe8ae3fcde8d7608d5b03ace51a4a3cebf18fee)

---

 .pick_status.json                               |  2 +-
 src/gallium/drivers/radeonsi/si_shader.h        |  3 +++
 src/gallium/drivers/radeonsi/si_state_shaders.c | 25 +++++++++++++++++++++++--
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index eec1cba2f3a..2714a799e7e 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -400,7 +400,7 @@
         "description": "radeonsi: don't create an infinite number of variants",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "b7501184b90a20015885b3f2276a7a5ceaef31a7"
     },
diff --git a/src/gallium/drivers/radeonsi/si_shader.h b/src/gallium/drivers/radeonsi/si_shader.h
index c58388ee325..ab11a185216 100644
--- a/src/gallium/drivers/radeonsi/si_shader.h
+++ b/src/gallium/drivers/radeonsi/si_shader.h
@@ -694,6 +694,9 @@ struct si_shader_key {
 
       unsigned inline_uniforms:1;
 
+      /* This must be kept last to limit the number of variants
+       * depending only on the uniform values.
+       */
       uint32_t inlined_uniform_values[MAX_INLINABLE_UNIFORMS];
    } opt;
 };
diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c b/src/gallium/drivers/radeonsi/si_state_shaders.c
index addea7a61d0..e5e5f1a6546 100644
--- a/src/gallium/drivers/radeonsi/si_state_shaders.c
+++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
@@ -2232,10 +2232,31 @@ current_not_ready:
 
    simple_mtx_lock(&sel->mutex);
 
+   /* Compute the size of the key without the uniform values. */
+   size_t s = (void*)&key->opt.inlined_uniform_values - (void*)key;
+   int variant_count = 0;
+   const int max_inline_uniforms_variants = 5;
+
    /* Find the shader variant. */
    for (iter = sel->first_variant; iter; iter = iter->next_variant) {
-      /* Don't check the "current" shader. We checked it above. */
-      if (current != iter && memcmp(&iter->key, key, sizeof(*key)) == 0) {
+      if (memcmp(&iter->key, key, s) == 0) {
+         /* Check the inlined uniform values separatly, and count
+          * the number of variants based on them.
+          */
+         if (key->opt.inline_uniforms &&
+             memcmp(iter->key.opt.inlined_uniform_values,
+                    key->opt.inlined_uniform_values,
+                    MAX_INLINABLE_UNIFORMS * 4) != 0) {
+            if (variant_count++ > max_inline_uniforms_variants) {
+               /* Too many variants. Disable inlining for this shader. */
+               key->opt.inline_uniforms = 0;
+               memset(key->opt.inlined_uniform_values, 0, MAX_INLINABLE_UNIFORMS * 4);
+               simple_mtx_unlock(&sel->mutex);
+               goto again;
+            }
+            continue;
+         }
+
          simple_mtx_unlock(&sel->mutex);
 
          if (unlikely(!util_queue_fence_is_signalled(&iter->ready))) {