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[MLIR][SPIRVToLLVM] Updated the documentation for type conversion 

This patch updates the type conversion section of the documentation.
It includes the modelling of array strides and the mapping of the
naturally padded structs.

Reviewed By: mravishankar

Differential Revision: https://reviews.llvm.org/D86674
This commit is contained in:
George Mitenkov 2020-08-27 07:47:13 +03:00
parent df182eb2d5
commit 9c224fd48a
1 changed files with 5 additions and 4 deletions
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9
mlir/docs/SPIRVToLLVMDialectConversion.md
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@ -54,8 +54,9 @@ which is not known at compile time. In LLVM, it is possible to index beyond the
end of the array. Therfore, runtime array can be implemented as a zero length
array type.
Moreover, SPIR-V supports the notion of array stride. Note that this is **not**
supported by type conversion at the moment.
Moreover, SPIR-V supports the notion of array stride. Currently only natural
strides (based on [`VulkanLayoutUtils`](VulkanLayoutUtils)) are supported. They
are also mapped to LLVM array.
SPIR-V Dialect | LLVM Dialect
:-----------------------------------: | :-----------------------------------:
@ -77,8 +78,7 @@ at the moment. Hence, we adhere to the following mapping:
* Structs with natural offset (*i.e.* offset that equals to cumulative size of
the previous struct elements or is a natural alignment) are mapped to
naturally padded structs. Nested structs with offset and structs with offset
containing arrays are **not** supported.
naturally padded structs.
* Structs with unnatural offset (*i.e.* offset that is not equal to cumulative
size of the previous struct elements) are **not** supported. In this case,
@ -783,3 +783,4 @@ to LLVM ops. At the moment, SPIR-V module attributes are ignored.
[LLVMFunctionAttributes]: https://llvm.org/docs/LangRef.html#function-attributes
[SPIRVFunctionAttributes]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#_a_id_function_control_a_function_control
[VulkanLayoutUtils]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/LayoutUtils.h