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Make vk::literal a target type.
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@s-perron
s-perron committed Nov 28, 2024
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25 changes: 15 additions & 10 deletions proposals/NNNN-inline-spirv-function-attributes.md
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Expand Up @@ -48,8 +48,13 @@ The `vk::ext_instruction`, `vk:spvexecutionmode`, `vk::ext_capability`, and
`vk::ext_extension` will become target attributes on the functions to which they
apply. Then the backend can generate the appropriate SPIR-V. Note that
`vk::ext_capability` and `vk::ext_extension` can apply to variables and type
aliases, but that will be part of another proposal. The `vk::literal` attribute
will be turned in to a target attribute on the function parameter.
aliases, but that will be part of another proposal.

In Sema, paramters with the `vk::literal` attribute will be converted to a
parameter of type `target(spirv.inline.literal, <N>)`, and the parameter passed
it is `zeroinitializer`. The SPIR-V backend will set the corresponding operand
in the `vk::ext_instruction` with the literal `N`. The value of the parameter is
ignored.

The `vk::ext_reference` attribute can be handled in Clang but changing the type
in the AST to a reference type. TODO: Need to figure out how address spaces work
Expand All @@ -58,14 +63,14 @@ with this.
The following table explains which target attribute each HLSL attribute will
correspond to, and how it will be interpreted in the backend.

HLSL Attribute | Applicable to | llvm-ir target attribute | Attribute Description
--------------------------------------------------------------------- | ----------------------------------------------------------------------------- | ------------------------------------------------------------ | ---------------------
`vk::ext_instruction(uint opcode, [string extended_instruction_set])` | Function declarations with no definition. | `"spv.ext_instruction"="<opcode>,<instruction set>"` | Calls to functions with this attribute are replaced by a single SPIR-V instruction.<br>If `<instruction set>` is the empty string, then it will generate the core SPIR-V instruction with the given opcode.<br>Otherwise, it will create an `OpExtInst` instruction, where the instruction is `<opcode>` in the given instruction set.
`vk::spvexecutionmode(uint execution_mode, ...)` | Entry point functions | `"spv.executionmode"="<mode>:<op>..."` | For each execution mode, a separate `OpExecuteMode` instruction is generated with the given operands. The operands are interpreted as literal integers.
`vk::ext_extension(string extension_name)` | Applicable to entry point functions and functions with `vk::ext_instruction`. | `"spv.extextension"="<extension name>,<extension name>,..."` | A separate `OpExtension` instruction is added for each extension name. The extension is added to the list of allowed extensions in the SPIR-V backend.
`vk::ext_capability(uint capability)` | Applicable to entry point functions and functions with `vk::ext_instruction`. | `"spv.extcapability"="<capability id>: <capability id>..."` | A separate `OpCapability` instruction is added for each capability. The capability is added to the list of allowed capabilities in the SPIR-V backend.
`vk::ext_literal` | Parameters of functions with `vk::ext_instruction` | `"spv.literal"` | The parameter is encoded as a literal in the SPIR-V instruction instead of generating an `OpConstant`.
`vk::ext_reference` | Parameters of functions with `vk::ext_instruction` | N/A (handled in Clang) | The parameter's type is modified to a reference type in the Clang AST. (Address space handling needs further investigation.)
HLSL Attribute | Applicable to | llvm-ir | Attribute Description
--------------------------------------------------------------------- | ----------------------------------------------------------------------------- | ----------------------------------------------------------------------------- | ---------------------
`vk::ext_instruction(uint opcode, [string extended_instruction_set])` | Function declarations with no definition. | Target attribute `"spv.ext_instruction"="<opcode>,<instruction set>"` | Calls to functions with this attribute are replaced by a single SPIR-V instruction.<br>If `<instruction set>` is the empty string, then it will generate the core SPIR-V instruction with the given opcode.<br>Otherwise, it will create an `OpExtInst` instruction, where the instruction is `<opcode>` in the given instruction set.
`vk::spvexecutionmode(uint execution_mode, ...)` | Entry point functions | Target attribute `"spv.executionmode"="<mode>:<op>..."` | For each execution mode, a separate `OpExecuteMode` instruction is generated with the given operands. The operands are interpreted as literal integers.
`vk::ext_extension(string extension_name)` | Applicable to entry point functions and functions with `vk::ext_instruction`. | Target attribute `"spv.extextension"="<extension name>,<extension name>,..."` | A separate `OpExtension` instruction is added for each extension name. The extension is added to the list of allowed extensions in the SPIR-V backend.
`vk::ext_capability(uint capability)` | Applicable to entry point functions and functions with `vk::ext_instruction`. | Target attribute `"spv.extcapability"="<capability id>: <capability id>..."` | A separate `OpCapability` instruction is added for each capability. The capability is added to the list of allowed capabilities in the SPIR-V backend.
`vk::ext_literal` | Parameters of functions with `vk::ext_instruction` | Target type `"spirv.inline.literal"` | The parameter's type becomes the `spirv.inline.literal` target type where the value of the target type is the value of the parameter.
`vk::ext_reference` | Parameters of functions with `vk::ext_instruction` | N/A (handled in Clang) | The parameter's type is modified to a reference type in the Clang AST. (Address space handling needs further investigation.)

TODO: Discuss optimizations.

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