shader/texture: Join separate image and sampler pairs offline

Games using D3D idioms can join images and samplers when a shader
executes, instead of baking them into a combined sampler image. This is
also possible on Vulkan.

One approach to this solution would be to use separate samplers on
Vulkan and leave this unimplemented on OpenGL, but we can't do this
because there's no consistent way of determining which constant buffer
holds a sampler and which one an image. We could in theory find the
first bit and if it's in the TIC area, it's an image; but this falls
apart when an image or sampler handle use an index of zero.

The used approach is to track for a LOP.OR operation (this is done at an
IR level, not at an ISA level), track again the constant buffers used as
source and store this pair. Then, outside of shader execution, join
the sample and image pair with a bitwise or operation.

This approach won't work on games that truly use separate samplers in a
meaningful way. For example, pooling textures in a 2D array and
determining at runtime what sampler to use.

This invalidates OpenGL's disk shader cache :)

- Used mostly by D3D ports to Switch

1 files changed, 37 insertions, 18 deletions

diff --git a/src/video_core/shader/decode/texture.cpp b/src/video_core/shader/decode/texture.cpp
index 8f0bb996e..29ebf65ba 100644
--- a/src/video_core/shader/decode/texture.cpp
+++ b/src/video_core/shader/decode/texture.cpp
@@ -357,13 +357,11 @@ u32 ShaderIR::DecodeTexture(NodeBlock& bb, u32 pc) {
     return pc;
 }
 
-ShaderIR::SamplerInfo ShaderIR::GetSamplerInfo(SamplerInfo info, u32 offset,
-                                               std::optional<u32> buffer) {
+ShaderIR::SamplerInfo ShaderIR::GetSamplerInfo(
+    SamplerInfo info, std::optional<Tegra::Engines::SamplerDescriptor> sampler) {
     if (info.IsComplete()) {
         return info;
     }
-    const auto sampler = buffer ? registry.ObtainBindlessSampler(*buffer, offset)
-                                : registry.ObtainBoundSampler(offset);
     if (!sampler) {
         LOG_WARNING(HW_GPU, "Unknown sampler info");
         info.type = info.type.value_or(Tegra::Shader::TextureType::Texture2D);
@@ -381,8 +379,8 @@ ShaderIR::SamplerInfo ShaderIR::GetSamplerInfo(SamplerInfo info, u32 offset,
 
 std::optional<Sampler> ShaderIR::GetSampler(Tegra::Shader::Sampler sampler,
                                             SamplerInfo sampler_info) {
-    const auto offset = static_cast<u32>(sampler.index.Value());
-    const auto info = GetSamplerInfo(sampler_info, offset);
+    const u32 offset = static_cast<u32>(sampler.index.Value());
+    const auto info = GetSamplerInfo(sampler_info, registry.ObtainBoundSampler(offset));
 
     // If this sampler has already been used, return the existing mapping.
     const auto it = std::find_if(used_samplers.begin(), used_samplers.end(),
@@ -404,20 +402,19 @@ std::optional<Sampler> ShaderIR::GetBindlessSampler(Tegra::Shader::Register reg,
     const Node sampler_register = GetRegister(reg);
     const auto [base_node, tracked_sampler_info] =
         TrackBindlessSampler(sampler_register, global_code, static_cast<s64>(global_code.size()));
-    ASSERT(base_node != nullptr);
-    if (base_node == nullptr) {
+    if (!base_node) {
+        UNREACHABLE();
         return std::nullopt;
     }
 
-    if (const auto bindless_sampler_info =
-            std::get_if<BindlessSamplerNode>(&*tracked_sampler_info)) {
-        const u32 buffer = bindless_sampler_info->GetIndex();
-        const u32 offset = bindless_sampler_info->GetOffset();
-        info = GetSamplerInfo(info, offset, buffer);
+    if (const auto sampler_info = std::get_if<BindlessSamplerNode>(&*tracked_sampler_info)) {
+        const u32 buffer = sampler_info->index;
+        const u32 offset = sampler_info->offset;
+        info = GetSamplerInfo(info, registry.ObtainBindlessSampler(buffer, offset));
 
         // If this sampler has already been used, return the existing mapping.
         const auto it = std::find_if(used_samplers.begin(), used_samplers.end(),
-                                     [buffer = buffer, offset = offset](const Sampler& entry) {
+                                     [buffer, offset](const Sampler& entry) {
                                          return entry.buffer == buffer && entry.offset == offset;
                                      });
         if (it != used_samplers.end()) {
@@ -431,10 +428,32 @@ std::optional<Sampler> ShaderIR::GetBindlessSampler(Tegra::Shader::Register reg,
         return used_samplers.emplace_back(next_index, offset, buffer, *info.type, *info.is_array,
                                           *info.is_shadow, *info.is_buffer, false);
     }
-    if (const auto array_sampler_info = std::get_if<ArraySamplerNode>(&*tracked_sampler_info)) {
-        const u32 base_offset = array_sampler_info->GetBaseOffset() / 4;
-        index_var = GetCustomVariable(array_sampler_info->GetIndexVar());
-        info = GetSamplerInfo(info, base_offset);
+    if (const auto sampler_info = std::get_if<SeparateSamplerNode>(&*tracked_sampler_info)) {
+        const std::pair indices = sampler_info->indices;
+        const std::pair offsets = sampler_info->offsets;
+        info = GetSamplerInfo(info, registry.ObtainSeparateSampler(indices, offsets));
+
+        // Try to use an already created sampler if it exists
+        const auto it = std::find_if(
+            used_samplers.begin(), used_samplers.end(), [indices, offsets](const Sampler& entry) {
+                return offsets == std::pair{entry.offset, entry.secondary_offset} &&
+                       indices == std::pair{entry.buffer, entry.secondary_buffer};
+            });
+        if (it != used_samplers.end()) {
+            ASSERT(it->is_separated && it->type == info.type && it->is_array == info.is_array &&
+                   it->is_shadow == info.is_shadow && it->is_buffer == info.is_buffer);
+            return *it;
+        }
+
+        // Otherwise create a new mapping for this sampler
+        const u32 next_index = static_cast<u32>(used_samplers.size());
+        return used_samplers.emplace_back(next_index, offsets, indices, *info.type, *info.is_array,
+                                          *info.is_shadow, *info.is_buffer);
+    }
+    if (const auto sampler_info = std::get_if<ArraySamplerNode>(&*tracked_sampler_info)) {
+        const u32 base_offset = sampler_info->base_offset / 4;
+        index_var = GetCustomVariable(sampler_info->bindless_var);
+        info = GetSamplerInfo(info, registry.ObtainBoundSampler(base_offset));
 
         // If this sampler has already been used, return the existing mapping.
         const auto it = std::find_if(