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Rollup merge of #117247 - kjetilkjeka:nvptx_direct_passmode_exception, r=workingjubilee,RalfJung

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NVPTX: Allow PassMode::Direct for ptx kernels for now

Upgrading the nvptx toolchain to the newest nightly makes it hit the assert that links to https://github.com/rust-lang/rust/issues/115666

It seems like most targets get around this by using `PassMode::Indirect`. That is impossible for the kernel as it's not a normal call, but instead the arguments are copied from CPU to GPU and the passed pointer would be invalid when it reached the GPU.

I also made an experiment with `PassMode::Cast` but at least the most simple version of this broke the assembly API tests.

I added  fixing the pass mode in my unofficial tracking issue list (I do not have the necessary permissions to update to official one). https://github.com/rust-lang/rust/issues/38788#issuecomment-1079021853

Since the ptx_abi is currently unstable and have been working with `PassMode::Direct` for more than a year now, the steps above is hopefully sufficient to enable it as an exception until I can prioritize to fix it. I'm currently looking at steps to enable the CI for nvptx64 again and would prefer to finish that first.
This commit is contained in:
Matthias Krüger 2023-10-27 19:46:09 +02:00 committed by GitHub
commit c3d56be6b6
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9
compiler/rustc_codegen_llvm/src/abi.rs
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@ -362,9 +362,14 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
// currently use this mode so we have to allow it -- but we absolutely
// shouldn't let any more targets do that.
// (Also see <https://github.com/rust-lang/rust/issues/115666>.)
//
// The unstable abi `PtxKernel` also uses Direct for now.
// It needs to switch to something else before stabilization can happen.
// (See issue: https://github.com/rust-lang/rust/issues/117271)
assert!(
matches!(&*cx.tcx.sess.target.arch, "wasm32" | "wasm64"),
"`PassMode::Direct` for aggregates only allowed on wasm targets\nProblematic type: {:#?}",
matches!(&*cx.tcx.sess.target.arch, "wasm32" | "wasm64")
|| self.conv == Conv::PtxKernel,
"`PassMode::Direct` for aggregates only allowed on wasm and `extern \"ptx-kernel\"` fns\nProblematic type: {:#?}",
arg.layout,
);
}