[OpenCL] Support for inline asm

[XChy]

Currently, we don't support inline asm and asm goto in OpenCL: https://godbolt.org/z/ea5oeP8K3
But it's a widely used feature in NVPTX and AMDGCN. Do we have a plan to support it?
If it's not forbidden on purpose, I would post a PR for it.

[llvmbot]

@llvm/issue-subscribers-opencl

Author: Hongyu Chen (XChy)

Currently, we don't support inline asm and asm goto in OpenCL: https://godbolt.org/z/ea5oeP8K3 But it's a widely used feature in NVPTX and AMDGCN. Do we have a plan to support it? If it's not forbidden on purpose, I would post a PR for it.

[svenvh]

If it's not forbidden on purpose

Just checked the OpenCL C Specification, which says:

The following names are reserved for use as keywords in OpenCL C and shall not be used otherwise.

• Names reserved as keywords by C99.

And the asm keyword is under "J.5 Common Extensions" in the C99 spec; so exposing asm in OpenCL looks fine to me.