From fe1d84e08372e021bbde92bd9d69b4dcbfc0421e Mon Sep 17 00:00:00 2001
From: Sushma Venkatesh Reddy <sushma.venkatesh.reddy@intel.com>
Date: Fri, 15 Aug 2025 03:06:24 +0000
Subject: [PATCH] intel/compiler: apply sqrt workaround for Horizon Forbidden
 West shader
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Added a workaround for a known shader in Horizon Forbidden West that causes
visual corruption on Intel anv driver. The fix clamps fsqrt inputs using
fmax(x, 1e-12) to avoid invalid values. Integrated the workaround via
brw_nir_apply_sqrt_workarounds() and applied it conditionally in the Vulkan
pipeline based on the shader's BLAKE3 hash.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12555

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36990>
---
 src/intel/compiler/brw_nir.h                  |  2 +
 .../compiler/brw_nir_trig_workarounds.py      |  6 +++
 src/intel/vulkan/anv_shader_compile.c         | 54 +++++++++++++++++++
 3 files changed, 62 insertions(+)

diff --git a/src/intel/compiler/brw_nir.h b/src/intel/compiler/brw_nir.h
index 90bf060dd91..aaff0f97256 100644
--- a/src/intel/compiler/brw_nir.h
+++ b/src/intel/compiler/brw_nir.h
@@ -239,6 +239,8 @@ bool brw_nir_apply_trig_workarounds(nir_shader *nir);
 
 bool brw_nir_limit_trig_input_range_workaround(nir_shader *nir);
 
+bool brw_nir_apply_sqrt_workarounds(nir_shader *nir);
+
 bool brw_nir_lower_fsign(nir_shader *nir);
 
 bool brw_nir_opt_fsat(nir_shader *);
diff --git a/src/intel/compiler/brw_nir_trig_workarounds.py b/src/intel/compiler/brw_nir_trig_workarounds.py
index 5d6a7601d31..06eb15a5448 100644
--- a/src/intel/compiler/brw_nir_trig_workarounds.py
+++ b/src/intel/compiler/brw_nir_trig_workarounds.py
@@ -45,6 +45,10 @@ LIMIT_TRIG_INPUT_RANGE_WORKAROUND = [
     (('fcos', 'x(is_not_const)'), ('fcos', ('fmod', 'x', 2.0 * pi))),
 ]
 
+SQRT_WORKAROUND = [
+    (('fsqrt', 'x(is_not_const)'), ('fsqrt', ('fmax', 'x', 1e-12))),
+]
+
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument('-p', '--import-path', required=True)
@@ -61,6 +65,8 @@ def run():
                                       TRIG_WORKAROUNDS).render())
     print(nir_algebraic.AlgebraicPass("brw_nir_limit_trig_input_range_workaround",
                                       LIMIT_TRIG_INPUT_RANGE_WORKAROUND).render())
+    print(nir_algebraic.AlgebraicPass("brw_nir_apply_sqrt_workarounds",
+                                      SQRT_WORKAROUND).render())
 
 
 if __name__ == '__main__':
diff --git a/src/intel/vulkan/anv_shader_compile.c b/src/intel/vulkan/anv_shader_compile.c
index e4b583a688f..8978238a6e7 100644
--- a/src/intel/vulkan/anv_shader_compile.c
+++ b/src/intel/vulkan/anv_shader_compile.c
@@ -16,6 +16,58 @@
 #include "compiler/brw_nir_rt.h"
 #include "compiler/intel_nir.h"
 
+typedef void (*game_wa_callback)(nir_shader *nir);
+
+/* Structure to hold a game-specific workaround entry */
+struct game_wa_entry {
+   game_wa_callback cb;
+   uint32_t shader_blake3s[16][BLAKE3_OUT_LEN32];
+};
+
+/* Workaround for a shader in Horizon Forbidden West that causes
+ * visual corruption.  The shader writes the result of fsqrt to
+ * storage images with a 16-bit image format and misrendering
+ * occurs when those values are denormal for an unknown reason.
+ *
+ * This clamps the image writes to the smallest fp16 normalized
+ * value.  (Pattern matching against fsqrt is easy to do in a one
+ * line algebraic pass, while matching image stores is harder.)
+ *
+ * See https://gitlab.freedesktop.org/mesa/mesa/-/issues/12555
+ */
+static void
+wa_forbidden_west(nir_shader *nir)
+{
+   NIR_PASS(_, nir, brw_nir_apply_sqrt_workarounds);
+}
+
+/* List of game-specific workarounds identified by BLAKE3 hash of the shader.
+ * Add new workarounds here as needed.
+ */
+static const struct game_wa_entry game_was[] = {
+   {
+      .cb = wa_forbidden_west,
+      .shader_blake3s = {
+         {0x51683151, 0xe044f0ce, 0xc210a762, 0xb12b2da4, 0x4e69ddc0, 0x237b1cc1, 0xc84bcf09, 0x31cfe883},
+      },
+   },
+};
+
+/* Apply game-specific workarounds based on the shader's BLAKE3 hash */
+static void
+anv_nir_apply_shader_workarounds(nir_shader *nir)
+{
+   for (unsigned i = 0; i < ARRAY_SIZE(game_was); i++) {
+      const struct game_wa_entry *wa = &game_was[i];
+      for (unsigned j = 0; j < ARRAY_SIZE(wa->shader_blake3s); j++) {
+         if (_mesa_printed_blake3_equal(nir->info.source_blake3, wa->shader_blake3s[j])) {
+            wa->cb(nir);
+            return;
+         }
+      }
+   }
+}
+
 static enum brw_robustness_flags
 anv_get_robust_flags(const struct vk_pipeline_robustness_state *rstate)
 {
@@ -1742,6 +1794,8 @@ anv_shader_compile(struct vk_device *vk_device,
 
       anv_fixup_subgroup_size(device->physical->instance,
                               &shader_data->info->nir->info);
+
+      anv_nir_apply_shader_workarounds(shader_data->info->nir);
    }
 
    /* Combine intersection & any-hit before lowering */