[HLSL] clang-dxc emits dxv related warnings and errors when compiling to textual DXIL

[bogner]

Running something like clang-dxc.exe -T cs_6_2 x.hlsl does one of two silly things, depending on whether dxv is on your path:

• warning: dxv not found; resulting DXIL will not be validated
• error: dxv command failed with exit code 1

The former makes sense when generating a binary (ie, with -Fo out.dxil), but it doesn't really make sense when we're generating text since the validator needs a binary anyway. The latter is even sillier, and results in all compiles to textual IR to fail if dxv is on your path.

We should only attempt to run dxv from the driver when emitting an object.

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: Justin Bogner (bogner)

Running something like `clang-dxc.exe -T cs_6_2 x.hlsl` does one of two silly things, depending on whether `dxv` is on your path: - warning: dxv not found; resulting DXIL will not be validated - error: dxv command failed with exit code 1

The former makes sense when generating a binary (ie, with -Fo out.dxil), but it doesn't really make sense when we're generating text since the validator needs a binary anyway. The latter is even sillier, and results in all compiles to textual IR to fail if dxv is on your path.

We should only attempt to run dxv from the driver when emitting an object.