Simple architecture document
This CL adds the start of an architecture document which can be expanded
as needed. The document is mostly an architecture diagram of how the
various pieces fit together.
Change-Id: I49b6509b9178928d100aece3c284199060969b6c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/28660
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
diff --git a/docs/arch.md b/docs/arch.md
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+# Tint Architecture
+
+```
+ +--------+ +------+
+ | SPIR-V | | WGSL |
+ +----|---+ +---|--+
+ | |
+ | |
+ +---------|---------------------------|--------+
+ | | Reader | |
+ | | | |
+ | +-------|------+ +------|------+ |
+ | | SPIRV-Reader | | WGSL-Reader | |
+ | +--------------+ +-------------+ |
+ +-----------------------|----------------------+
+ |
+ |
+ +--|--+ +---------+
+ | AST |------| IsValid |
+ +--|--+ +---------+
+ |
+ |
+ +--------|--------+
+ | Type Determiner |
+ +--------|--------+
+ |
+ |
+ +-----|-----+
+ | Validator |
+ +-----|-----+
+ |
+ |
+ +------|-----+
+ | Transforms |
+ +------|-----+
+ |
+ |
++-------------------------------------|------------------------------------+
+| Writer |
+| |
+| +--------------+ +-------------+ +-------------+ +------------+ |
+| | SPIRV-Writer | | WGSL-Writer | | HLSL-Writer | | MSL-Writer | |
+| +-------|------+ +------|------+ +------|------+ +------|-----+ |
++---------|------------------|------------------|------------------|-------+
+ | | | |
+ | | | |
+ | | | |
+ +----|---+ +---|--+ +---|--+ +--|--+
+ | SPIR-V | | WGSL | | HLSL | | MSL |
+ +--------+ +------+ +------+ +-----+
+```
+
+## WGSL Reader
+
+The WGSL reader is a recursive descent parser. It closely follows the WGSL
+grammar in the naming of the parse methods.
+
+
+## AST
+
+After generation the AST will run an `IsValid` method which verifies that the
+produced AST is structurally correct. This means that things like `if`
+statements have a condition and body attached.
+
+
+## Type Determiner
+
+The type determination stage assigns a result type to each node in the AST. It
+will do the minimal amount of validation required in order to always be
+accessing valid nodes, but that doesn't mean the overall AST is valid. (e.g. a
+4 component vector type constructor with 5 components will pass type
+determination but is invalid.)
+
+
+## Validation
+
+After the validation step the AST should be a known valid WGSL program.
+
+
+## Transforms
+
+There maybe various transforms we want to run over the AST. This is for things
+like Vertex Pulling or Robust Buffer Access. These transforms will modify the
+AST and must produce valid AST after their execution.
+
+Currently the transforms are run individually but we should consider adding
+a transform manager to maintain and execute the list of transforms.
+
+
+## Writers
+
+The writers should be thread safe, we maybe generating the HLSL and MLS output
+at the same time on different threads. (The writer portion is the only one
+that needs to be thread safe.)
