Vulkan: Optimize DescriptorSetLayoutDesc layout

Separate out immutable samplers into its own array so we can remove
padding from PackedDescriptorSetBinding which reduces the size of that
struct from 16 bytes to 4 bytes.

Bug: angleproject:2462
Change-Id: I79d1ab584178202c9b7f34b0c7926edced4e21a8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5464162
Commit-Queue: mohan maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>

4 files changed, 26 insertions, 37 deletions

diff --git a/src/libANGLE/renderer/vulkan/UtilsVk.cpp b/src/libANGLE/renderer/vulkan/UtilsVk.cpp
index 0c53c7bb00..306a40ec28 100644
--- a/src/libANGLE/renderer/vulkan/UtilsVk.cpp
+++ b/src/libANGLE/renderer/vulkan/UtilsVk.cpp
@@ -1453,8 +1453,7 @@ angle::Result UtilsVk::ensureResourcesInitialized(ContextVk *contextVk,
         &mDescriptorSetLayouts[function][DescriptorSetIndex::Internal]));
 
     vk::DescriptorSetLayoutBindingVector bindingVector;
-    std::vector<VkSampler> immutableSamplers;
-    descriptorSetDesc.unpackBindings(&bindingVector, &immutableSamplers);
+    descriptorSetDesc.unpackBindings(&bindingVector);
     std::vector<VkDescriptorPoolSize> descriptorPoolSizes;
 
     for (const VkDescriptorSetLayoutBinding &binding : bindingVector)
diff --git a/src/libANGLE/renderer/vulkan/vk_cache_utils.cpp b/src/libANGLE/renderer/vulkan/vk_cache_utils.cpp
index 74a3c87798..3061a76631 100644
--- a/src/libANGLE/renderer/vulkan/vk_cache_utils.cpp
+++ b/src/libANGLE/renderer/vulkan/vk_cache_utils.cpp
@@ -4275,7 +4275,9 @@ bool operator==(const AttachmentOpsArray &lhs, const AttachmentOpsArray &rhs)
 // DescriptorSetLayoutDesc implementation.
 DescriptorSetLayoutDesc::DescriptorSetLayoutDesc()
     : mPackedDescriptorSetLayout{}, mValidDescriptorSetLayoutIndexMask()
-{}
+{
+    mImmutableSamplers.fill(VK_NULL_HANDLE);
+}
 
 DescriptorSetLayoutDesc::~DescriptorSetLayoutDesc() = default;
 
@@ -4286,13 +4288,20 @@ DescriptorSetLayoutDesc &DescriptorSetLayoutDesc::operator=(const DescriptorSetL
 
 size_t DescriptorSetLayoutDesc::hash() const
 {
-    return angle::ComputeGenericHash(mPackedDescriptorSetLayout);
+    size_t genericHash = angle::ComputeGenericHash(mValidDescriptorSetLayoutIndexMask);
+    for (size_t bindingIndex : mValidDescriptorSetLayoutIndexMask)
+    {
+        genericHash ^= angle::ComputeGenericHash(mPackedDescriptorSetLayout[bindingIndex]) ^
+                       angle::ComputeGenericHash(mImmutableSamplers[bindingIndex]);
+    }
+    return genericHash;
 }
 
 bool DescriptorSetLayoutDesc::operator==(const DescriptorSetLayoutDesc &other) const
 {
     return memcmp(&mPackedDescriptorSetLayout, &other.mPackedDescriptorSetLayout,
-                  sizeof(mPackedDescriptorSetLayout)) == 0;
+                  sizeof(mPackedDescriptorSetLayout)) == 0 &&
+           memcmp(&mImmutableSamplers, &other.mImmutableSamplers, sizeof(mImmutableSamplers)) == 0;
 }
 
 void DescriptorSetLayoutDesc::update(uint32_t bindingIndex,
@@ -4309,20 +4318,19 @@ void DescriptorSetLayoutDesc::update(uint32_t bindingIndex,
     SetBitField(packedBinding.type, descriptorType);
     SetBitField(packedBinding.count, count);
     SetBitField(packedBinding.stages, stages);
-    packedBinding.immutableSampler = VK_NULL_HANDLE;
-    packedBinding.pad              = 0;
 
     if (immutableSampler)
     {
         ASSERT(count == 1);
-        packedBinding.immutableSampler = immutableSampler->getHandle();
+        ASSERT(bindingIndex < gl::IMPLEMENTATION_MAX_ACTIVE_TEXTURES);
+
+        mImmutableSamplers[bindingIndex] = immutableSampler->getHandle();
     }
 
     mValidDescriptorSetLayoutIndexMask.set(bindingIndex, count > 0);
 }
 
-void DescriptorSetLayoutDesc::unpackBindings(DescriptorSetLayoutBindingVector *bindings,
-                                             std::vector<VkSampler> *immutableSamplers) const
+void DescriptorSetLayoutDesc::unpackBindings(DescriptorSetLayoutBindingVector *bindings) const
 {
     for (size_t bindingIndex : mValidDescriptorSetLayoutIndexMask)
     {
@@ -4334,28 +4342,15 @@ void DescriptorSetLayoutDesc::unpackBindings(DescriptorSetLayoutBindingVector *b
         binding.descriptorCount              = packedBinding.count;
         binding.descriptorType               = static_cast<VkDescriptorType>(packedBinding.type);
         binding.stageFlags = static_cast<VkShaderStageFlags>(packedBinding.stages);
-        if (packedBinding.immutableSampler != VK_NULL_HANDLE)
+        if (mImmutableSamplers[bindingIndex] != VK_NULL_HANDLE)
         {
             ASSERT(packedBinding.count == 1);
-            immutableSamplers->push_back(packedBinding.immutableSampler);
-            binding.pImmutableSamplers = reinterpret_cast<const VkSampler *>(angle::DirtyPointer);
+            ASSERT(bindingIndex < gl::IMPLEMENTATION_MAX_ACTIVE_TEXTURES);
+            binding.pImmutableSamplers = &mImmutableSamplers[bindingIndex];
         }
 
         bindings->push_back(binding);
     }
-    if (!immutableSamplers->empty())
-    {
-        // Patch up pImmutableSampler addresses now that the vector is stable
-        int immutableIndex = 0;
-        for (VkDescriptorSetLayoutBinding &binding : *bindings)
-        {
-            if (binding.pImmutableSamplers)
-            {
-                binding.pImmutableSamplers = &(*immutableSamplers)[immutableIndex];
-                immutableIndex++;
-            }
-        }
-    }
 }
 
 // PipelineLayoutDesc implementation.
@@ -7476,8 +7471,7 @@ angle::Result DescriptorSetLayoutCache::getDescriptorSetLayout(
     mCacheStats.missAndIncrementSize();
     // We must unpack the descriptor set layout description.
     vk::DescriptorSetLayoutBindingVector bindingVector;
-    std::vector<VkSampler> immutableSamplers;
-    desc.unpackBindings(&bindingVector, &immutableSamplers);
+    desc.unpackBindings(&bindingVector);
 
     VkDescriptorSetLayoutCreateInfo createInfo = {};
     createInfo.sType        = VK_STRUCTURE_TYPE_DESCRIPTOR_SET_LAYOUT_CREATE_INFO;
diff --git a/src/libANGLE/renderer/vulkan/vk_cache_utils.h b/src/libANGLE/renderer/vulkan/vk_cache_utils.h
index 8ca6de50e6..4db163d9de 100644
--- a/src/libANGLE/renderer/vulkan/vk_cache_utils.h
+++ b/src/libANGLE/renderer/vulkan/vk_cache_utils.h
@@ -1016,8 +1016,7 @@ class DescriptorSetLayoutDesc final
                 VkShaderStageFlags stages,
                 const Sampler *immutableSampler);
 
-    void unpackBindings(DescriptorSetLayoutBindingVector *bindings,
-                        std::vector<VkSampler> *immutableSamplers) const;
+    void unpackBindings(DescriptorSetLayoutBindingVector *bindings) const;
 
     bool empty() const { return !mValidDescriptorSetLayoutIndexMask.any(); }
 
@@ -1030,16 +1029,15 @@ class DescriptorSetLayoutDesc final
         uint8_t type;    // Stores a packed VkDescriptorType descriptorType.
         uint8_t stages;  // Stores a packed VkShaderStageFlags.
         uint16_t count;  // Stores a packed uint32_t descriptorCount.
-        uint32_t pad;
-        VkSampler immutableSampler;
     };
 
-    // 4x 32bit
-    static_assert(sizeof(PackedDescriptorSetBinding) == 16, "Unexpected size");
+    // 1x 32bit
+    static_assert(sizeof(PackedDescriptorSetBinding) == 4, "Unexpected size");
 
     // This is a compact representation of a descriptor set layout.
     std::array<PackedDescriptorSetBinding, kMaxDescriptorSetLayoutBindings>
         mPackedDescriptorSetLayout;
+    gl::ActiveTextureArray<VkSampler> mImmutableSamplers;
 
     DescriptorSetLayoutIndexMask mValidDescriptorSetLayoutIndexMask;
 };
diff --git a/src/libANGLE/renderer/vulkan/vk_helpers.cpp b/src/libANGLE/renderer/vulkan/vk_helpers.cpp
index 0ccbd0b11c..cb33abe6ae 100644
--- a/src/libANGLE/renderer/vulkan/vk_helpers.cpp
+++ b/src/libANGLE/renderer/vulkan/vk_helpers.cpp
@@ -1035,9 +1035,7 @@ angle::Result InitDynamicDescriptorPool(Context *context,
 {
     std::vector<VkDescriptorPoolSize> descriptorPoolSizes;
     DescriptorSetLayoutBindingVector bindingVector;
-    std::vector<VkSampler> immutableSamplers;
-
-    descriptorSetLayoutDesc.unpackBindings(&bindingVector, &immutableSamplers);
+    descriptorSetLayoutDesc.unpackBindings(&bindingVector);
 
     for (const VkDescriptorSetLayoutBinding &binding : bindingVector)
     {