merian: SamplerPool: fix duplicate sampler creation

include/merian/utils/hash.hpp

@@ -15,7 +15,7 @@ template <typename T, typename... Types> void hash_combine(std::size_t& seed, co
     hash_combine(seed, args...);
 }
 // Optional auxiliary generic functions to support hash_val() without arguments
-inline void hashCombine(std::size_t&) {}
+inline void hash_combine(std::size_t& /*unused*/) {}
 
 // Generic function to create a hash value out of a heterogeneous list of arguments
 template <typename... Types> std::size_t hash_val(const Types&... args) {
@@ -25,12 +25,22 @@ template <typename... Types> std::size_t hash_val(const Types&... args) {
 }
 //--------------
 
+template <typename T> std::size_t hash_aligned_8(const T& v) {
+    const std::size_t size = sizeof(T) / sizeof(uint8_t);
+    const uint8_t* v_bits = reinterpret_cast<const uint8_t*>(&v);
+    std::size_t seed = 0;
+    for (std::size_t i = 0u; i < size; i++) {
+        hash_combine(seed, v_bits[i]);
+    }
+    return seed;
+}
+
 template <typename T> std::size_t hash_aligned_32(const T& v) {
-    const uint32_t size = sizeof(T) / sizeof(uint32_t);
-    const uint32_t* vBits = reinterpret_cast<const uint32_t*>(&v);
+    const std::size_t size = sizeof(T) / sizeof(uint32_t);
+    const uint32_t* v_bits = reinterpret_cast<const uint32_t*>(&v);
     std::size_t seed = 0;
-    for (uint32_t i = 0u; i < size; i++) {
-        hash_combine(seed, vBits[i]);
+    for (std::size_t i = 0u; i < size; i++) {
+        hash_combine(seed, v_bits[i]);
     }
     return seed;
 }
@@ -44,4 +54,13 @@ template <typename T> struct HashAligned32 {
     }
 };
 
+// Generic hash function to use when using a struct aligned to 8-bit as std::map-like container key
+// Important: this only works if the struct contains integral types, as it will not
+// do any pointer chasing
+template <typename T> struct HashAligned8 {
+    std::size_t operator()(const T& s) const {
+        return hash_aligned_8(s);
+    }
+};
+
 } // namespace merian

include/merian/vk/sampler/sampler_pool.hpp

@@ -6,6 +6,7 @@
 
 #include <spdlog/spdlog.h>
 #include <vulkan/vulkan.hpp>
+#include <vulkan/vulkan_hash.hpp>
 
 #include <unordered_map>
 
@@ -59,14 +60,26 @@ class SamplerPool : public std::enable_shared_from_this<SamplerPool> {
         auto operator<=>(const SamplerState&) const = default;
     };
 
+    struct SamplerStateHash {
+        std::size_t operator()(const SamplerState& s) const {
+            return hash_val(create_hash(s.createInfo), reduction_hash(s.reduction),
+                            ycbcr_conversion_hash(s.ycbr));
+        }
+
+      private:
+        std::hash<vk::SamplerCreateInfo> create_hash;
+        std::hash<vk::SamplerReductionModeCreateInfo> reduction_hash;
+        std::hash<vk::SamplerYcbcrConversionCreateInfo> ycbcr_conversion_hash;
+    };
+
     struct Chain {
         VkStructureType sType;
         const Chain* pNext;
     };
 
     const ContextHandle context;
 
-    std::unordered_map<SamplerState, std::weak_ptr<Sampler>, HashAligned32<SamplerState>> state_map;
+    std::unordered_map<SamplerState, std::weak_ptr<Sampler>, SamplerStateHash> state_map;
 };
 
 using SamplerPoolHandle = std::shared_ptr<SamplerPool>;