[dxil2spv] Read file directly into llvm::MemoryBuffer

[sudonatalie]

Read DXIL file directly into llvm::MemoryBuffer rather than through an
IDxcBlobEncoding. This also allows support for supplying file by STDIN
(not yet with dedicated CLI).

Also clean up some CMake LLVM dependencies.

[AppVeyorBot]

✅ Build DirectXShaderCompiler 1.0.1328 completed (commit 23d2c8e16c by @sudonatalie)

[jaebaek]

I am not versed on the output of llvm::MemoryBuffer::getFileOrSTDIN(..) but I am curious about the side effect of referencing the MemoryBuffer after calling release(). Is it ok in terms of the use-after-free?

[sudonatalie]

There's no use-after-free risk, but moving the std::unique_ptr is preferable to releasing the raw pointer so I've switched it.

[jaebaek]

If it has invalid DXIL program header, I think we have to print an error, don't we?

[sudonatalie]

If the DXIL program header is invalid, this will fall through to emitError("Could not parse DXIL module")

[jaebaek]

Is diagStr just used by hlsl::dxilutil::LoadModuleFromBitcode(..) or is it used to return a string?
If it somehow contains an error message, we have to print it and handle the error case.

[sudonatalie]

There's actually just some recent unfinished cleanup here:

DirectXShaderCompiler/lib/DXIL/DxilUtilDbgInfoAndMisc.cpp

Line 154 in 54924ce

// Note: the DiagStr is not used.

I've propagated the note for now.

[jaebaek]

Can we print the error message using err here (if module == nullptr)?

[sudonatalie]

Done

[jaebaek]

How does LLVM_LINK_COMPONENTS work?
I guess somehow the llvm cmake build uses static/dynamic linking with the listed libraries.
You removed LLVM_LINK_COMPONENTS from tools/clang/tools/dxil2spv/CMakeLists.txt. I am curious how the listed libraries here linked with what target library.

Another concern is building it in Windows. Do we only target Linux build?

[sudonatalie]

It's just a helper variable that does the same llvm_map_components_to_libnames later on in CMake functions:

DirectXShaderCompiler/cmake/modules/AddLLVM.cmake

Line 476 in 54924ce

${LLVM_LINK_COMPONENTS}

Just a cleanup that follows the last PR where I introduced a clang library layer, since it's how the rest of the codebase's CMake files link LLVM components (both for windows and Linux builds).

[jaebaek]

LGTM!

[AppVeyorBot]

✅ Build DirectXShaderCompiler 1.0.1354 completed (commit f9d78268b5 by @sudonatalie)