[llvm] [NVPTX] Widen sub-byte and non-power-of-two integers to a legal PTX type (PR #226113)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-nvptx

Author: Samarth Narang (snarang181)

<details>
<summary>Changes</summary>

`getPTXFundamentalTypeStr()` prints integers as `.u<N>` for their exact bit width, but PTX has no sub-byte or non-power-of-two integer types. An `i4` kernel parameter becomes `.param .u4`, which ptxas rejects (`Parsing error near '.u4': syntax error`); every non-power-of-two width up to 64 is affected, as are globals printed through the same path. The output is also self-inconsistent: ISel already loads such a parameter with `max(8, PowerOf2Ceil(N))` bits, so the same kernel declares `.param .u4` and reads it with `ld.param.b8`. Round the printed type up to that width. `i1` keeps its existing `pred`/`.u8` handling; the `i65`–`i127` `llvm_unreachable` is a separate pre-existing issue and is left alone.

Tested with `LLVM_PTXAS_EXECUTABLE` set (ptxas 13.4): NVPTX suite 614/614, and the new test's `%ptxas-verify` fails before this change.

Fixes #<!-- -->225261

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Full diff: https://github.com/llvm/llvm-project/pull/226113.diff


2 Files Affected:

- (modified) llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp (+3-2) 
- (added) llvm/test/CodeGen/NVPTX/non-power-of-two-int-param.ll (+46) 


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https://github.com/llvm/llvm-project/pull/226113