Shader cache index implementation (#2452)

1 files changed, 79 insertions, 0 deletions

diff --git a/tools/gfx/persistent-shader-cache.h b/tools/gfx/persistent-shader-cache.h
new file mode 100644
index 000000000..55738a9af
--- /dev/null
+++ b/tools/gfx/persistent-shader-cache.h
@@ -0,0 +1,79 @@
+// slang-shader-cache-index.h
+#pragma once
+#include "../../slang.h"
+#include "../../slang-com-ptr.h"
+
+#include "../../source/core/slang-string.h"
+#include "../../source/core/slang-dictionary.h"
+#include "../../source/core/slang-linked-list.h"
+
+namespace Slang
+{
+
+struct ShaderCacheEntry
+{
+    slang::Digest dependencyBasedDigest;
+    slang::Digest astBasedDigest;
+};
+
+class PersistentShaderCache
+{
+public:
+    // TODO: Remove in integration PR in favor of new ShaderCacheDesc in slang-gfx.h
+    struct Desc
+    {
+        String cacheFilename;
+        String shaderCachePath;
+        SlangInt entryCountLimit = 1000;
+        ISlangFileSystem* shaderCacheFileSystem = nullptr;
+    };
+
+    PersistentShaderCache(const Desc& inDesc);
+
+    // Fetch the cache entry corresponding to the provided key. If found, move the entry to
+    // the front of entries and return the entry and the corresponding compiled code in
+    // outCompiledCode. Else, return nullptr.
+    LinkedNode<ShaderCacheEntry>* findEntry(const slang::Digest& key, ISlangBlob** outCompiledCode);
+
+    // Add an entry to the cache with the provided key and contents hashes. If
+    // adding an entry causes the cache to exceed size limitations, this will also
+    // delete the least recently used entry.
+    void addEntry(const slang::Digest& dependencyDigest, const slang::Digest& astDigest, ISlangBlob* compiledCode);
+
+    // Update the contents hash for the specified entry in the cache and update the
+    // corresponding file on disk.
+    void updateEntry(
+        LinkedNode<ShaderCacheEntry>* entryNode,
+        const slang::Digest& dependencyDigest,
+        const slang::Digest& astDigest,
+        ISlangBlob* updatedCode);
+
+private:
+    // Load a previous cache index saved to disk. If not found, create a new cache index
+    // and save it to disk as filename.
+    void loadCacheFromFile();
+
+    // Update the cache index on disk. This should be called any time an entry changes.
+    void saveCacheToFile();
+
+    // Delete the last entry (the least recently used) from entries, remove its key/value pair
+    // from keyToEntry, and remove the corresponding file on disk. This should only be called
+    // by addEntry() when the cache reaches maximum capacity.
+    void deleteLRUEntry();
+
+    // The shader cache's description.
+    Desc desc;
+
+    // Dictionary mapping each shader's key to its corresponding node (entry) in the list
+    // of entries.
+    Dictionary<slang::Digest, LinkedNode<ShaderCacheEntry>*> keyToEntry;
+
+    // Linked list containing the entries stored in the shader cache in order
+    // of most to least recently used.
+    LinkedList<ShaderCacheEntry> entries;
+
+    // The underlying file system used for the shader cache.
+    ComPtr<ISlangMutableFileSystem> mutableShaderCacheFileSystem = nullptr;
+};
+
+}