44 lines
1.8 KiB
Markdown
44 lines
1.8 KiB
Markdown
The EmitC dialect allows to convert operations from other MLIR dialects to EmitC
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ops. Those can be translated to C/C++ via the Cpp emitter.
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The following convention is followed:
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* If template arguments are passed to an `emitc.call_opaque` operation, C++ is
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generated.
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* If tensors are used, C++ is generated.
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* If multiple return values are used within in a functions or an
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`emitc.call_opaque` operation, C++11 is required.
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* If floating-point type template arguments are passed to an `emitc.call_opaque`
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operation, C++20 is required.
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* If `ssize_t` is used, then the code requires the POSIX header `sys/types.h`
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or any of the C++ headers in which the type is defined.
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* If `_Float16` is used, the code requires the support of C additional
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floating types.
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* If `__bf16` is used, the code requires a compiler that supports it, such as
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GCC or Clang.
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* Else the generated code is compatible with C99.
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These restrictions are neither inherent to the EmitC dialect itself nor to the
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Cpp emitter and therefore need to be considered while implementing conversions.
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Type conversions are provided for the MLIR type `index` into the unsigned `size_t`
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type and its signed counterpart `ptrdiff_t`. Conversions between these two types
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are only valid if the `index`-typed values are within
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`[PTRDIFF_MIN, PTRDIFF_MAX]`.
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After the conversion, C/C++ code can be emitted with `mlir-translate`. The tool
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supports translating MLIR to C/C++ by passing `-mlir-to-cpp`. Furthermore, code
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with variables declared at top can be generated by passing the additional
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argument `-declare-variables-at-top`.
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Besides operations part of the EmitC dialect, the Cpp targets supports
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translating the following operations:
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* 'cf' Dialect
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* `cf.br`
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* `cf.cond_br`
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* 'func' Dialect
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* `func.call`
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* `func.func`
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* `func.return`
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