[NFC][DO NOT MERGE] Add scratch design for sycl-non-rdc- mode in NewOffloadModel#21858
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maksimsab wants to merge 1 commit intointel:syclfrom
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[NFC][DO NOT MERGE] Add scratch design for sycl-non-rdc- mode in NewOffloadModel#21858maksimsab wants to merge 1 commit intointel:syclfrom
maksimsab wants to merge 1 commit intointel:syclfrom
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bader
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Apr 23, 2026
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| The new SYCL offload model (`--offload-new-driver`) currently treats all device code as RDC (Relocatable Device Code): all TUs are merged in `clang-linker-wrapper` before post-link. `-fno-sycl-rdc` is a high-priority gap (P0) that enables per-TU self-contained device images, important for reducing link time, shipping precompiled device libraries, and scenarios where `SYCL_EXTERNAL` is not used. | ||
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| The old model implements this via `shouldDoPerObjectFileLinking()` + per-TU device link steps during the compile phase in the driver. This plan implements the **linker-wrapper-side approach** as it is simpler, consistent with the new model's architecture, and can be done incrementally. |
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The driver changes are not covered by this proposal but based on the provided information I conclude that you propose clang-linker-wrapper to perform offload code linking during "link step". I might be wrong, but I think one of the requirements for -fno-gpu-rdc is to perform offload code linking at compile step. Please, check if this such requirement.
Anyway, this is big step away from the current SYCL workflow and upstream driver workflow for non-SYCL mode. -fno-gpu-rdc always links offload executable at compile step, not at the link step.
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| **Implementation note:** | ||
| * Refactor the existing codegen loop (per-split SPIR-V/AOT) into a helper lambda/function so it can be reused for both RDC and non-RDC paths without duplication. | ||
| * clang-linker-wrapper already contains a suitable command line flag `--relocatable` from upstream which should be reused. It means that Clang Driver should start pass `--relocatable` for the existing RDC mode. Later, an absence of `--relocatable` flag will imply non-rdc sycl mode. |
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- --relocatable is not about RDC vs non-RDC compilation at all. It is about whether the output of the link needs its sections renamed for safe re-linking — an OpenMP static-library concern.
- When --relocatable is present, linkAndWrapDeviceFiles still runs (all TUs merged, the current RDC behavior for SYCL). The only change is the section renaming post-step. It cannot be used as a signal to
switch to per-TU processing inside the wrapper.
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