From 7e4e142aaebd2a5169ac73cb1a91b6c8d6fe2a7f Mon Sep 17 00:00:00 2001
From: nmzik <Nmzik@mail.ru>
Date: Sun, 11 Oct 2026 00:00:23 +0200
Subject: [PATCH] gpu: enable native R8 SNORM texture sampling

---
 src/graphics/guest_gpu/gpu_format.cpp  |  2 +-
 tests/ShaderRecompilerComputeTests.cpp | 52 ++++++++++++++++----------
 2 files changed, 34 insertions(+), 20 deletions(-)

diff --git a/src/graphics/guest_gpu/gpu_format.cpp b/src/graphics/guest_gpu/gpu_format.cpp
index 44f11ffe..8a89bdbe 100644
--- a/src/graphics/guest_gpu/gpu_format.cpp
+++ b/src/graphics/guest_gpu/gpu_format.cpp
@@ -21,7 +21,7 @@ struct FormatInfo {
 constexpr FormatInfo kFormatInfo[] = {
 	{BufferFormat::k8UNorm, 1, 0, 1, true, false},
 	{BufferFormat::k8UScaled, 1, 0, 0, true, false},
-	{BufferFormat::k8SNorm, 1, 0, 1, false, false},
+	{BufferFormat::k8SNorm, 1, 0, 1, true, false},
 	{BufferFormat::k8UInt, 1, 0, 1, true, true},
 	{BufferFormat::k16UNorm, 2, 0, 2, true, false},
 	{BufferFormat::k16SNorm, 2, 0, 2, true, false},
diff --git a/tests/ShaderRecompilerComputeTests.cpp b/tests/ShaderRecompilerComputeTests.cpp
index bb6d3339..6b77f72b 100644
--- a/tests/ShaderRecompilerComputeTests.cpp
+++ b/tests/ShaderRecompilerComputeTests.cpp
@@ -34170,10 +34170,11 @@ TestCase ImageSamplePackedUintConvertsSampleAndGather() {
   return test;
 }
 
-template <bool rg> TestCase ImageSampleUScaled8() {
+template <bool rg, bool snorm = false> TestCase ImageSamplePacked8() {
   using O = ShaderOpcode;
   TestCase test;
-  test.name = rg ? "ImageSampleRG8UScaled" : "ImageSampleR8UScaled";
+  test.name = snorm ? "ImageSampleR8SNorm"
+                   : rg ? "ImageSampleRG8UScaled" : "ImageSampleR8UScaled";
   AppendVMovLiteral(&test.code, 20, std::bit_cast<u32>(0.375f));
   AppendVMovLiteral(&test.code, 21, std::bit_cast<u32>(0.375f));
   test.code.push_back(EncodeMimg0(0x20, 0xf));
@@ -34186,26 +34187,37 @@ template <bool rg> TestCase ImageSampleUScaled8() {
     AppendStoreVgpr(&test.code, component, component);
   }
   AppendEnd(&test.code);
-  // R varies horizontally; G varies vertically in the opposite direction.
-  // Bilinear samples must retain fractions despite host UNorm filter precision.
   test.image_width = test.image_height = 2;
-  test.sampled_image_rgba = rg ? std::vector<u32>{0xffffff00u, 0x00ff0000u}
-                               : std::vector<u32>{0xff00ff00u};
-  test.sampled_image_format = rg ? vk::Format::eR8G8Unorm : vk::Format::eR8Unorm;
+  test.sampled_image_rgba =
+      snorm ? std::vector<u32>{0x7fc08180u}
+            : rg ? std::vector<u32>{0xffffff00u, 0x00ff0000u}
+                 : std::vector<u32>{0xff00ff00u};
+  test.sampled_image_format =
+      snorm ? vk::Format::eR8Snorm
+            : rg ? vk::Format::eR8G8Unorm : vk::Format::eR8Unorm;
   test.sampled_image_dwords_per_pixel = 1;
-  test.sampler_filter = vk::Filter::eLinear;
-  test.expected_float_tolerance = 0.01f;
-  test.user_data = MakeSampledTextureData(rg ? Prospero::BufferFormat::k8_8UScaled
-                                            : Prospero::BufferFormat::k8UScaled);
+  test.sampler_filter = snorm ? vk::Filter::eNearest : vk::Filter::eLinear;
+  test.expected_float_tolerance = snorm ? 0.00002f : 0.01f;
+  test.user_data = MakeSampledTextureData(
+      snorm ? Prospero::BufferFormat::k8SNorm
+            : rg ? Prospero::BufferFormat::k8_8UScaled
+                 : Prospero::BufferFormat::k8UScaled);
   test.user_data[1] |= 1u << 30u;
   test.user_data[2] = 1u << 14u;
   test.user_data[50] = 12u * sizeof(u32);
   test.user_data[51] = 3u << 28u;
   test.has_user_data = true;
-  test.image_descriptor_swizzle = DstSel(rg ? 5 : 4, 4, 0, 1);
-  for (float value : {rg ? 191.25f : 63.75f, 63.75f, 0.0f, 1.0f,
-                      0.0f, rg ? 0.0f : 255.0f, 255.0f, rg ? 255.0f : 0.0f,
-                      1.0f, 1.0f, 1.0f, 1.0f}) {
+  test.image_descriptor_swizzle = snorm ? DstSel(4, 5, 6, 7)
+                                      : DstSel(rg ? 5 : 4, 4, 0, 1);
+  constexpr float midpoint = -64.0f / 127.0f;
+  const std::array<float, 12> expected = snorm
+      // -128 and -127 both clamp to -1; the interior signed value normalizes by 127.
+      ? std::array<float, 12>{-1, 0, 0, 1, midpoint, 1, -1, -1, 1, 1, 1, 1}
+      // R varies horizontally; G varies vertically in the opposite direction.
+      : std::array<float, 12>{rg ? 191.25f : 63.75f, 63.75f, 0.0f, 1.0f,
+                             0.0f, rg ? 0.0f : 255.0f, 255.0f, rg ? 255.0f : 0.0f,
+                             1.0f, 1.0f, 1.0f, 1.0f};
+  for (float value : expected) {
     test.expected.push_back(std::bit_cast<u32>(value));
   }
   test.opcodes = {O::V_MOV_B32, O::IMAGE_SAMPLE, O::IMAGE_GATHER4_LZ,
@@ -37565,8 +37577,9 @@ std::vector<TestCase> MakeCases() {
   AddCase(ImageLoadR32SintUsesSignedSampledImage);
   AddCase(ImageLoadPackedUintUnpacksAndSwizzles);
   AddCase(ImageSamplePackedUintConvertsSampleAndGather);
-  AddCase(ImageSampleUScaled8<false>);
-  AddCase(ImageSampleUScaled8<true>);
+  AddCase(ImageSamplePacked8<false>);
+  AddCase(ImageSamplePacked8<true>);
+  AddCase(ImageSamplePacked8<false, true>);
   AddCase(ImageLoadR128IgnoresAdjacentMaskSgprs);
   AddCase(ImageLoad1DUsesScalarCoordinate);
   AddCase(ImageGather2DInstructionWith1DDescriptor);
@@ -43136,8 +43149,9 @@ int main(int argc, char **argv) {
   }
   if (argc == 2 && std::strcmp(argv[1], "--scaled-texture-only") == 0) {
     VulkanHarness vulkan;
-    RunCase(&vulkan, ImageSampleUScaled8<false>());
-    RunCase(&vulkan, ImageSampleUScaled8<true>());
+    RunCase(&vulkan, ImageSamplePacked8<false>());
+    RunCase(&vulkan, ImageSamplePacked8<true>());
+    RunCase(&vulkan, ImageSamplePacked8<false, true>());
     return 0;
   }
   if (argc == 2 && std::strcmp(argv[1], "--packed-texture-only") == 0) {