Shader cache index header (#2448)

* checkpoint

* Added shaderCachePath field to IDevice desc in gfx.slang, gfx-smoke.slang should be functional

* ran premake

* Revert erroneous commits from rebasing

* Added ShaderCacheIndex class header with design details

* Header edits

* more header edits

* Post-rebase premake.bat run to fix solution weirdness; Initialize commitHash to nullptr and check that a commitHash is successfully returned

2 files changed, 70 insertions, 7 deletions

diff --git a/source/compiler-core/slang-dxc-compiler.cpp b/source/compiler-core/slang-dxc-compiler.cpp
index 6619d000c..52933eaa7 100644
--- a/source/compiler-core/slang-dxc-compiler.cpp
+++ b/source/compiler-core/slang-dxc-compiler.cpp
@@ -599,16 +599,19 @@ SlangResult DXCDownstreamCompiler::getVersionString(slang::IBlob** outVersionStr
             versionString.append(".");
             versionString.append(minor);
 
-            char* commitHash;
+            char* commitHash = nullptr;
             uint32_t unused;
             versionInfo2->GetCommitInfo(&unused, &commitHash);
+            if (commitHash)
+            {
+                // Successfully queried the commit hash, append to the version and return.
+                versionString.append(commitHash);
+                CoTaskMemFree(commitHash);
 
-            versionString.append(commitHash);
-            CoTaskMemFree(commitHash);
-
-            version = StringBlob::create(versionString.getBuffer());
-            *outVersionString = version.detach();
-            return SLANG_OK;
+                version = StringBlob::create(versionString.getBuffer());
+                *outVersionString = version.detach();
+                return SLANG_OK;
+            }
         }
     }
 
diff --git a/source/slang/slang-shader-cache-index.h b/source/slang/slang-shader-cache-index.h
new file mode 100644
index 000000000..530aacf11
--- /dev/null
+++ b/source/slang/slang-shader-cache-index.h
@@ -0,0 +1,60 @@
+#pragma once
+#include "../../slang.h"
+
+#include "../core/slang-string.h"
+#include "../core/slang-linked-list.h"
+#include "../core/slang-dictionary.h"
+
+namespace Slang
+{
+    class ShaderCacheIndex
+    {
+    public:
+        struct ShaderCacheEntry
+        {
+            slang::Digest dependencyBasedDigest;
+            slang::Digest astBasedDigest;
+        };
+
+        ShaderCacheIndex(SlangInt size)
+            : entryCountLimit(size)
+        {}
+
+        // Load a previous cache index saved to disk. If not found, create a new cache index
+        // and save it to disk as filename.
+        SlangResult loadCacheIndexFromFile(String filename);
+
+        // Fetch the cache entry corresponding to the provided key. If found, move the entry to
+        // the front of entries and return the entry. Else, return nullptr.
+        ShaderCacheEntry* findEntry(const slang::Digest& key);
+
+        // 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);
+
+        // Update the contents hash for the specified entry in the cache and update the
+        // corresponding file on disk.
+        void updateEntry(const slang::Digest& dependencyDigest, const slang::Digest& astDigest);
+
+    private:
+        // Update the cache index on disk. This should be called any time an entry changes.
+        SlangResult saveCacheIndexToFile();
+
+        // Delete the last entry from entries and remove its key/value pair from keyToContents
+        // as well as remove the corresponding file on disk. This should only be used when the
+        // cache has reached the size limit specified by entryLimit to create space for a new entry.
+        void deleteEntry();
+
+        // 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 maximum number of cache entries allowed.
+        SlangInt entryCountLimit = -1;
+    }
+}