tree 066eab7beadcc76a917e05a5fbadd0dd6329c26f
parent 2ef01048624dc2a564d5925d082a72a51bb97c48
author Arvind Sudarsanam <arvind.sudarsanam@intel.com> 1744908488 -0400
committer GitHub <noreply@github.com> 1744908488 +0000
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[SYCL] Add clang-linker-wrapper changes to call clang-sycl-linker for SYCL offloads (#135683)

This PR is one of the many PRs in the SYCL upstreaming effort focusing
on device code linking during the SYCL offload compilation process. RFC:
https://discourse.llvm.org/t/rfc-offloading-design-for-sycl-offload-kind-and-spir-targets/74088

Approved PRs so far:
1. [Clang][SYCL] Introduce clang-sycl-linker to link SYCL offloading
device code (Part 1 of many) -
[Link](https://github.com/llvm/llvm-project/pull/112245)
2. [clang-sycl-linker] Replace llvm-link with API calls -
[Link](https://github.com/llvm/llvm-project/pull/133797)
3. [SYCL][SPIR-V Backend][clang-sycl-linker] Add SPIR-V backend support
inside clang-sycl-linker -
[Link](https://github.com/llvm/llvm-project/pull/133967)

This PR adds SYCL device code linking support to clang-linker-wrapper.

### Summary for this PR

Device code linking happens inside clang-linker-wrapper. In the current
implementation, clang-linker-wrapper does the following:

1. Extracts device code. Input_1, Input_2,.....
5. Group device code according to target devices Inputs[triple_1] = ....
Inputs[triple_2] = ....
6. For each group, i.e. Inputs[triple_i], a. Gather all the offload
kinds found inside those inputs in ActiveOffloadKinds b. Link all images
inside Inputs[triple_i] by calling clang --target=triple_i .... c.
Create a copy of that linked image for each offload kind and add it to
Output[Kind] list.

In SYCL compilation flow, there is a deviation in Step 3b. We call
device code splitting inside the 'clang --target=triple_i ....' call and
the output is now a 'packaged' file containing multiple device images.
This deviation requires us to capture the OffloadKind during the linking
stage and pass it along to the linking function (clang), so that clang
can be called with a unique option '--sycl-link' that will help us to
call 'clang-sycl-linker' under the hood (clang-sycl-linker will do SYCL
specific linking).

Our current objective is to implement an end-to-end SYCL offloading flow
and get it working. We will eventually merge our approach with the
community flow.

Thanks

---------

Signed-off-by: Arvind Sudarsanam <arvind.sudarsanam@intel.com>