Simple test profiling (#1062)

* First pass support for performance profiling

* Test across all elements

* Fix bug - sourceContents is not used, should use rawSource.

* * Add ability to get prelude from API.
* Allow specifying source language for render-test
* Made it possible to compile a test input file as C++
  * Special handling for reflection
* Added C++ impl to performance-profile.slang

* Remove some clang warnings.

* Output profile timings on appveyor and other TC.

* Remove passing around of StdWriters (can use global).
Small comment improvements.

1 files changed, 8 insertions, 0 deletions

diff --git a/slang.h b/slang.h
index c4e62f01e..e31689200 100644
--- a/slang.h
+++ b/slang.h
@@ -2670,6 +2670,14 @@ namespace slang
             SlangPassThrough passThrough,
             const char* preludeText) = 0;
 
+            /** Get the 'prelude' for generated code for a 'downstream compiler'.
+            @param passThrough The downstream compiler for generated code that will have the prelude applied to it. 
+            @param outPrelude  On exit holds a blob that holds the string of the prelude.
+            */
+        virtual SLANG_NO_THROW void SLANG_MCALL getDownstreamCompilerPrelude(
+            SlangPassThrough passThrough,
+            ISlangBlob** outPrelude) = 0;
+
             /** Get the build version 'tag' string. The string is the same as produced via `git describe --tags`
             for the project. If Slang is built separately from the automated build scripts
             the contents will by default be 'unknown'. Any string can be set by changing the