attempt 2

Author: bob80905

include/dxc/Support/dxcapi.use.h

@@ -36,12 +36,7 @@ class DxcDllSupport {
     m_dll = LoadLibraryA(dllName);
     if (m_dll == nullptr)
       return HRESULT_FROM_WIN32(GetLastError());
-    // load dxil.dll too
-    HMODULE dxildllModule =
-        LoadLibraryA(DxilDLLPath == "" ? "dxil.dll" : GetDxilDLLPath());
-    if (dxildllModule == nullptr) {
-      return HRESULT_FROM_WIN32(GetLastError());
-    }
+
     m_createFn = (DxcCreateInstanceProc)GetProcAddress(m_dll, fnName);
 
     if (m_createFn == nullptr) {

lib/DxcSupport/dxcapi.use.cpp

@@ -75,7 +75,6 @@ void IFT_Data(HRESULT hr, LPCWSTR data) {
 
 void EnsureEnabled(DxcDllSupport &dxcSupport) {
   if (!dxcSupport.IsEnabled()) {
-    // first initialize Dxil.dll
     IFT(dxcSupport.Initialize());
   }
 }

tools/clang/tools/dxclib/dxc.cpp

@@ -1448,7 +1448,7 @@ int dxc::main(int argc, const char **argv_) {
       SetUnhandledExceptionFilter(ExceptionFilter);
 #endif
 
-    // Setup a helper DLL.
+    // Setup dxcompiler DLL.
     {
       std::string dllErrorString;
       llvm::raw_string_ostream dllErrorStream(dllErrorString);
@@ -1462,6 +1462,7 @@ int dxc::main(int argc, const char **argv_) {
     }
 
     EnsureEnabled(dxcSupport);
+
     DxcContext context(dxcOpts, dxcSupport);
     // Handle help request, which overrides any other processing.
     if (dxcOpts.ShowHelp) {

tools/clang/tools/dxcompiler/dxcutil.cpp

@@ -62,8 +62,10 @@ bool CreateValidator(CComPtr<IDxcValidator> &pValidator,
   // otherwise, use the external validator provided by the dxil_dll_path
   // argument
   else {
-    // if a valid absolute path was given, but the DXIL.dll
-    // is invalid, then error
+    // this code loads the dll path on an as-needed basis.
+    // if a request to initialize the dxil lib arrives more than once
+    // then DxilLibInitialize does nothing.
+    IFT(DxilLibInitialize(DxilDLLPath));
     IFTBOOL(DxilLibIsEnabled(DxilDLLPath), DXC_E_VALIDATOR_MISSING);
     IFT(DxilLibCreateInstance(CLSID_DxcValidator, &pValidator));