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[AMDGPU] Update AMDGPUUsage.rst to document two intrinsics #123816

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Jan 24, 2025
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[AMDGPU] Update AMDGPUUsage.rst to document two intrinsics #123816

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[AMDGPU] Update AMDGPUUsage.rst to document two intrinsics
jwanggit86 Jan 21, 2025
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Mention supported data types.
jwanggit86 Jan 23, 2025
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13 changes: 13 additions & 0 deletions llvm/docs/AMDGPUUsage.rst
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Expand Up @@ -1422,6 +1422,19 @@ The AMDGPU backend implements the following LLVM IR intrinsics.
Returns a pair for the swapped registers. The first element of the return
corresponds to the swapped element of the first argument.

llvm.amdgcn.mov.dpp The llvm.amdgcn.mov.dpp.`<type>` intrinsic represents the mov.dpp operation in AMDGPU.
This operation is being deprecated and can be replaced with llvm.amdgcn.update.dpp.

llvm.amdgcn.update.dpp The llvm.amdgcn.update.dpp.`<type>` intrinsic represents the update.dpp operation in AMDGPU.
It takes an old value, a source operand, a DPP control operand, a row mask, a bank mask, and a bound control.
Various data types are supported, including, bf16, f16, f32, f64, i16, i32, i64, p0, p3, p5, v2f16, v2f32, v2i16, v2i32, v2p0, v3i32, v4i32, v8f16.
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@arsenm arsenm Jan 22, 2025

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This is misleading, it's not a mere v_mov_b32.

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@jayfoad jayfoad Jan 22, 2025

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Looks like this was copied directly from the comments in IntrinsicsAMDGPU.td so fixes to the description should go there first (or as well).

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@jwanggit86 jwanggit86 Jan 23, 2025

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Yes, it was copied from the .td file. @arsenm How should this be changed?

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@arsenm arsenm Jan 23, 2025 •
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Should mention it's v_mov_b32 with DPP, and mention the types it supports. It's not just i32 anymore

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@jayfoad jayfoad Jan 23, 2025

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Just remove this line? It already says below exactly what v_mov_b32 instructions it is equivalent to.

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@jwanggit86 jwanggit86 Jan 23, 2025

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Added a line to mention supported data types. Previously missed ".i32" suffix has been changed to ".".

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@jwanggit86 jwanggit86 Jan 23, 2025

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Will update the .td file correspondingly once this file is done.

This operation is equivalent to a sequence of v_mov_b32 operations.
It is preferred over llvm.amdgcn.mov.dpp.`<type>` for future use.
`llvm.amdgcn.update.dpp.<type> <old> <src> <dpp_ctrl> <row_mask> <bank_mask> <bound_ctrl>`
Should be equivalent to:
- `v_mov_b32 <dest> <old>`
- `v_mov_b32 <dest> <src> <dpp_ctrl> <row_mask> <bank_mask> <bound_ctrl>`

============================================== ==========================================================

.. TODO::
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