change default validation behavior

Author: bob80905

include/dxc/Support/HLSLOptions.h

@@ -115,7 +115,7 @@ struct RewriterOpts {
 };
 
 enum class ValidatorSelection : int {
-  Auto,        // Try DXIL.dll; fallback to internal validator
+  Auto,        // Try internal validator; fallback to DXIL.dll
   Internal,    // Force internal validator (even if DXIL.dll is present)
   External,    // Use DXIL.dll, failing compilation if not available
   Invalid = -1 // Invalid

tools/clang/tools/dxcompiler/dxcutil.cpp

@@ -52,19 +52,20 @@ namespace {
 bool CreateValidator(CComPtr<IDxcValidator> &pValidator,
                      hlsl::options::ValidatorSelection SelectValidator =
                          hlsl::options::ValidatorSelection::Auto) {
+  bool bInternalValidator = false;
   bool bInternal =
       SelectValidator == hlsl::options::ValidatorSelection::Internal;
   bool bExternal =
       SelectValidator == hlsl::options::ValidatorSelection::External;
-  if (!bInternal && DxilLibIsEnabled())
-    DxilLibCreateInstance(CLSID_DxcValidator, &pValidator);
 
-  bool bInternalValidator = false;
-  if (pValidator == nullptr) {
-    IFTBOOL(!bExternal, DXC_E_VALIDATOR_MISSING);
+  if (!bExternal)
     IFT(CreateDxcValidator(IID_PPV_ARGS(&pValidator)));
-    bInternalValidator = true;
+
+  if (pValidator == nullptr && DxilLibIsEnabled()) {
+    IFTBOOL(!bInternal, DXC_E_VALIDATOR_MISSING);
+    DxilLibCreateInstance(CLSID_DxcValidator, &pValidator);
   }
+
   return bInternalValidator;
 }