3 files changed, 136 insertions, 1 deletions

diff --git a/source/core/slang-shared-library.cpp b/source/core/slang-shared-library.cpp
index 746e14e4c..8d362fd89 100644
--- a/source/core/slang-shared-library.cpp
+++ b/source/core/slang-shared-library.cpp
@@ -5,6 +5,18 @@
 #include "slang-io.h"
 #include "slang-string-util.h"
 
+#if defined(_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#elif defined(__linux__)
+#include <dlfcn.h>
+#endif
+#include <sys/stat.h>
+#include <sys/types.h>
+#ifndef WIN32
+#    include <unistd.h>
+#endif
+
 namespace Slang
 {
 
@@ -87,4 +99,50 @@ void* DefaultSharedLibrary::findSymbolAddressByName(char const* name)
     return SharedLibrary::findSymbolAddressByName(m_sharedLibraryHandle, name);
 }
 
+
+String SharedLibraryUtils::getSharedLibraryFileName(void* symbolInLib)
+{
+#if defined(_WIN32)
+    HMODULE moduleHandle;
+    GetModuleHandleExA(
+        GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+        (LPCSTR)symbolInLib,
+        &moduleHandle);
+    const int maxLength = 1024;
+    wchar_t filenameBuffer[maxLength];
+    auto length = GetModuleFileNameW(moduleHandle, filenameBuffer, maxLength);
+    if (length == maxLength)
+    {
+        // Insufficient buffer, return empty.
+        return String();
+    }
+    return String::fromWString(filenameBuffer);
+
+#elif defined(__linux__)
+    Dl_info dllInfo;
+    if (!dladdr(symbolInLib, &dllInfo))
+    {
+        return String();
+    }
+    return dllInfo.dli_fname;
+
+#else
+    return String();
+#endif
+}
+
+uint64_t SharedLibraryUtils::getSharedLibraryTimestamp(void* symbolInLib)
+{
+    auto fileName = getSharedLibraryFileName(symbolInLib);
+    if (fileName.getLength() == 0)
+        return 0;
+    struct stat result;
+    if (stat(fileName.getBuffer(), &result) == 0)
+    {
+        auto mod_time = result.st_mtime;
+        return (uint64_t)mod_time;
+    }
+    return 0;
+}
+
 } 
diff --git a/source/core/slang-shared-library.h b/source/core/slang-shared-library.h
index c29f16289..c33f1f41b 100644
--- a/source/core/slang-shared-library.h
+++ b/source/core/slang-shared-library.h
@@ -94,6 +94,13 @@ protected:
     String m_path;
 };
 
+class SharedLibraryUtils
+{
+public:
+    static String getSharedLibraryFileName(void* symbolInLib);
+    static uint64_t getSharedLibraryTimestamp(void* symbolInLib);
+};
+
 }
 
 #endif // SLANG_SHARED_LIBRARY_H_INCLUDED
diff --git a/source/slang/slang-api.cpp b/source/slang/slang-api.cpp
index 56dc44c04..251a3980b 100644
--- a/source/slang/slang-api.cpp
+++ b/source/slang/slang-api.cpp
@@ -4,6 +4,8 @@
 
 #include "slang-repro.h"
 
+#include "../core/slang-shared-library.h"
+
 // implementation of C interface
 
 SLANG_API SlangSession* spCreateSession(const char*)
@@ -17,6 +19,65 @@ SLANG_API SlangSession* spCreateSession(const char*)
     return globalSession.detach();
 }
 
+// Attempt to load a previously compiled stdlib from the same file system location as the slang dll.
+// Returns SLANG_OK when the cache is sucessfully loaded.
+// Also returns the filename to the stdlib cache and the timestamp of current slang dll.
+SlangResult tryLoadStdLibFromCache(
+    slang::IGlobalSession* globalSession,
+    Slang::String& outCachePath,
+    uint64_t& outTimestamp)
+{
+    auto fileName =
+        Slang::SharedLibraryUtils::getSharedLibraryFileName((void*)slang_createGlobalSession);
+    uint64_t currentLibTimestamp =
+        Slang::SharedLibraryUtils::getSharedLibraryTimestamp((void*)slang_createGlobalSession);
+    auto dirName = Slang::Path::getParentDirectory(fileName);
+    auto cacheFileName = Slang::Path::combine(dirName, "slang-stdlib.bin");
+    outTimestamp = currentLibTimestamp;
+    outCachePath = cacheFileName;
+    if (currentLibTimestamp == 0)
+    {
+        return SLANG_FAIL;
+    }
+    Slang::ScopedAllocation cacheData;
+    SLANG_RETURN_ON_FAIL(Slang::File::readAllBytes(cacheFileName, cacheData));
+
+    // The first 8 bytes stores the timestamp of the slang dll that created this stdlib cache.
+    if (cacheData.getSizeInBytes() < sizeof(uint64_t))
+        return SLANG_FAIL;
+    auto cacheTimestamp = *(uint64_t*)(cacheData.getData());
+    if (cacheTimestamp != currentLibTimestamp)
+        return SLANG_FAIL;
+    SLANG_RETURN_ON_FAIL(globalSession->loadStdLib(
+        (uint8_t*)cacheData.getData() + sizeof(uint64_t),
+        cacheData.getSizeInBytes() - sizeof(uint64_t)));
+    return SLANG_OK;
+}
+
+SlangResult trySaveStdLibToCache(
+    slang::IGlobalSession* globalSession,
+    const Slang::String& cacheFilename,
+    uint64_t dllTimestamp)
+{
+    if (dllTimestamp != 0 && cacheFilename.getLength() != 0)
+    {
+        Slang::ComPtr<ISlangBlob> stdLibBlobPtr;
+        SLANG_RETURN_ON_FAIL(
+            globalSession->saveStdLib(SLANG_ARCHIVE_TYPE_RIFF_LZ4, stdLibBlobPtr.writeRef()));
+        try
+        {
+            Slang::FileStream fileStream(cacheFilename, Slang::FileMode::Create);
+            fileStream.write(&dllTimestamp, sizeof(dllTimestamp));
+            fileStream.write(stdLibBlobPtr->getBufferPointer(), stdLibBlobPtr->getBufferSize());
+            return SLANG_OK;
+        }
+        catch (...)
+        {
+        }
+    }
+    return SLANG_FAIL;
+}
+
 SLANG_API SlangResult slang_createGlobalSession(
     SlangInt                apiVersion,
     slang::IGlobalSession** outGlobalSession)
@@ -32,7 +93,16 @@ SLANG_API SlangResult slang_createGlobalSession(
     }
     else
     {
-        SLANG_RETURN_ON_FAIL(globalSession->compileStdLib());
+        Slang::String cacheFilename;
+        uint64_t dllTimestamp = 0;
+        if (tryLoadStdLibFromCache(globalSession, cacheFilename, dllTimestamp) != SLANG_OK)
+        {
+            // Compile std lib from embeded source.
+            SLANG_RETURN_ON_FAIL(globalSession->compileStdLib());
+
+            // Store the compiled stdlib to cache file.
+            trySaveStdLibToCache(globalSession, cacheFilename, dllTimestamp);
+        }
     }
 
     *outGlobalSession = globalSession.detach();