Allow use of dxc compiler for DXIL generation (#241)

- Add shader model 6.0, 6.1, and 6.2 targets

- Add DXIL and DXIL assembly as output formats

- Add header for DXC API to `external/`

- Add `dxc-support.cpp` that wraps usage of the API

- Add `-pass-through dxc` option, equivalent to what we have for `fxc`

Notes:
* This does *not* include any logic to add `dxcompiler.dll` to our build process; that is way out of scope for the build complexity I'm ready to deal with
* For right now, the use of `dxcompiler.dll` is hard-coded, and it must be discoverable in the current executable's search path; options to customize can come later
* The `-pass-through` option is kind of silly because the code doesn't actually pay attention to the value (just whether it is set). If you set it to `fxc` but ask for DXIL, we pass through `dxc` anyway.

1 files changed, 3 insertions, 0 deletions

diff --git a/source/slang/options.cpp b/source/slang/options.cpp
index 971d17b51..7eea3fecc 100644
--- a/source/slang/options.cpp
+++ b/source/slang/options.cpp
@@ -317,6 +317,8 @@ struct OptionsParser
 
                     CASE(spirv, SPIRV);
                     CASE(spirv-assembly, SPIRV_ASM);
+                    CASE(dxil, DXIL);
+                    CASE(dxil-assembly, DXIL_ASM);
                     CASE(none, TARGET_NONE);
 
                 #undef CASE
@@ -390,6 +392,7 @@ struct OptionsParser
                     String name = tryReadCommandLineArgument(arg, &argCursor, argEnd);
                     SlangPassThrough passThrough = SLANG_PASS_THROUGH_NONE;
                     if (name == "fxc") { passThrough = SLANG_PASS_THROUGH_FXC; }
+                    else if (name == "dxc") { passThrough = SLANG_PASS_THROUGH_DXC; }
                     else if (name == "glslang") { passThrough = SLANG_PASS_THROUGH_GLSLANG; }
                     else
                     {