108 lines
4.7 KiB
Markdown
108 lines
4.7 KiB
Markdown
# Tint Architecture
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```
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+--------+ +------+
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| SPIR-V | | WGSL |
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+----|---+ +---|--+
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+---------|---------------------------|--------+
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| | Reader | |
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| | | |
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| +-------|------+ +------|------+ |
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| | SPIRV-Reader | | WGSL-Reader | |
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| +--------------+ +-------------+ |
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+-----------------------|----------------------+
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+--|--+ +---------+
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| AST |------| IsValid |
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+--|--+ +---------+
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+--------|--------+
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| Type Determiner |
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+--------|--------+
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+-----|-----+
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| Validator |
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+-----|-----+
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+-----|-----+
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| Inspector |
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+-----|-----+
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+------|-----+
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| Transforms |
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+------|-----+
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+-------------------------------------|------------------------------------+
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| Writer |
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| +--------------+ +-------------+ +-------------+ +------------+ |
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| | SPIRV-Writer | | WGSL-Writer | | HLSL-Writer | | MSL-Writer | |
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| +-------|------+ +------|------+ +------|------+ +------|-----+ |
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+---------|------------------|------------------|------------------|-------+
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| | | |
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+----|---+ +---|--+ +---|--+ +--|--+
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| SPIR-V | | WGSL | | HLSL | | MSL |
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+--------+ +------+ +------+ +-----+
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```
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## WGSL Reader
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The WGSL reader is a recursive descent parser. It closely follows the WGSL
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grammar in the naming of the parse methods.
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## AST
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The Abstract Syntax Tree is a directed acyclic graph of nodes encoding
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the structure of the WGSL program.
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Many AST nodes have numeric parameters. For example, the ast::StrideDecoration
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node has numeric stride parameter, which is a count of the number of bytes from
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the start of one array element to the start of the next. The AST node itself
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does not constrain the set of stride values that you can set, aside from storing
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it as an unsigned integer.
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After creating the AST for the whole WGSL program, Tint will run an `IsValid`
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method which verifies that the produced AST is structurally correct. This
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means that things like `if` statements have a condition and body attached.
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A later phase of processing, Validation, will check properties such as whether
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array strides satisfy all the requirements in the WGSL specification.
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## Type Determiner
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The type determination stage assigns a result type to each node in the AST. It
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will do the minimal amount of validation required in order to always be
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accessing valid nodes, but that doesn't mean the overall AST is valid. (e.g. a
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4 component vector type constructor with 5 components will pass type
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determination but is invalid.)
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## Validation
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After the validation step the AST should be a known valid WGSL program.
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## Inspector
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The inspectors job is to go through the AST and pull out various pieces of
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information. The information may be used to pass information into the downstream
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compilers (things like specialization constants) or may be used to pass into
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transforms to update the AST before generating the resulting code.
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## Transforms
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There maybe various transforms we want to run over the AST. This is for things
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like Vertex Pulling or Robust Buffer Access. These transforms will modify the
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AST and must produce valid AST after their execution.
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Currently the transforms are run individually but we should consider adding
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a transform manager to maintain and execute the list of transforms.
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## Writers
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The writers should be thread safe, we maybe generating the HLSL and MLS output
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at the same time on different threads. (The writer portion is the only one
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that needs to be thread safe.)
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