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This change introduces sem::CompoundStatement, a new base class for statements that can hold other statements. sem::BlockStatements now derives from sem::CompoundStatement, and this change introduces the following new CompoundStatements: * `sem::IfStatement` * `sem::ElseStatement` * `sem::ForLoopStatement` * `sem::LoopStatement` * `sem::SwitchStatement`. These new CompoundStatements are now inserted into the semantic tree as now documented in `docs/compound_statements.md`. The `sem::BlockStatement::FindFirstParent()` methods have been moved down to `sem::Statement`. The `Resolver::BlockScope()` method has been replaced with `Resolver::Scope()` which now maintains the `current_statement_`, `current_compound_statement_ ` and `current_block_`. This simplifies statement nesting. The most significant change in behavior is that statements now always have a parent, so calling Block() on the initializer or continuing of a for-loop statement will now return the BlockStatement that holds the for-loop. Before this would return nullptr. Fixed: tint:979 Change-Id: I90e38fd719da2a281ed9210e975ab96171cb6842 Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/57707 Kokoro: Kokoro <noreply+kokoro@google.com> Commit-Queue: Ben Clayton <bclayton@google.com> Reviewed-by: James Price <jrprice@google.com>
116 lines
1.6 KiB
Markdown
116 lines
1.6 KiB
Markdown
# Compound Statements
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Compound statements are statements that can hold other statements.
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This document maps the WGSL compound statements to their semantic tree representations.
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## if statement
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WGSL:
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```
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if (condition_a) {
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statement_a;
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} else if (condition_b) {
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statement_b;
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} else {
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statement_c;
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}
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```
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Semantic tree:
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```
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sem::IfStatement {
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condition_a
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sem::BlockStatement {
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statement_a
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}
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sem::ElseStatement {
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condition_b
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sem::BlockStatement {
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statement_b
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}
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}
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sem::ElseStatement {
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sem::BlockStatement {
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statement_c
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}
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}
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}
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```
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## for loop
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WGSL:
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```
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for (initializer; condition; continuing) {
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statement;
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}
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```
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Semantic tree:
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```
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sem::ForLoopStatement {
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sem::Statement initializer
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sem::Expression condition
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sem::Statement continuing
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sem::LoopBlockStatement {
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sem::Statement statement
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}
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}
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```
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## loop
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WGSL:
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```
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loop (condition) {
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statement_a;
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continuing {
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statement_b;
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}
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}
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```
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Semantic tree:
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```
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sem::LoopStatement {
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sem::Expression condition
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sem::LoopBlockStatement {
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sem::Statement statement_a
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sem::LoopContinuingBlockStatement {
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sem::Statement statement_b
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}
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}
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}
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```
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## switch statement
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WGSL:
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```
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switch (condition) {
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case literal_a, literal_b: {
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statement_a;
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}
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default {
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statement_b;
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}
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}
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```
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Semantic tree:
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```
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sem::SwitchStatement {
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sem::Expression condition
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sem::SwitchCaseBlockStatement {
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sem::Statement statement_a
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}
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sem::SwitchCaseBlockStatement {
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sem::Statement statement_b
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}
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}
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```
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