From 077b25007cf8af3c3673d017625ea255bda87620 Mon Sep 17 00:00:00 2001 From: Dibyendu Majumdar Date: Sun, 5 Nov 2023 17:50:21 +0000 Subject: Link to parseIf. (#36) * Link to parseIf. Reorder the table of nodes. Fix example. * Replace code with links --- chapter05/README.md | 156 ++++++---------------------------------------------- 1 file changed, 18 insertions(+), 138 deletions(-) diff --git a/chapter05/README.md b/chapter05/README.md index 78a8b1fe..f0a59fa0 100644 --- a/chapter05/README.md +++ b/chapter05/README.md @@ -8,6 +8,17 @@ In this chapter we extend the language grammar with the following features: Here is the [complete language grammar](docs/05-grammar.md) for this chapter. +## New Nodes + +The following new nodes are introduced in this chapter: + +| Node Name | Type | Chapter | Description | Inputs | Value | +|-----------|---------|---------|----------------------------------------------------|------------------------------------------------|----------------------------------------------------| +| If | Control | 5 | A branching test, sub type of `MultiNode` | A control node and a data predicate node | A tuple of two values: one for true, one for false | +| Region | Control | 5 | A merge point for multiple control flows | An input for each control flow that is merging | Merged control | +| Phi | Data | 5 | A phi function picks a value based on control flow | A Region, and data nodes for each control path | Depends on control flow path taken | +| Stop | Control | 5 | Termination of the program | All return nodes of the function | None | + ## Recap Here is a recap of the nodes introduced in previous chapters: @@ -27,17 +38,6 @@ Here is a recap of the nodes introduced in previous chapters: | Minus | Data | 2 | Negate a value | One data node which value is negated | Result of the negation | | Scope | ? | 3 | Represents scopes in the graph | Nodes that represent the current value of variables | None | -## New Nodes - -The following new nodes are introduced in this chapter: - -| Node Name | Type | Chapter | Description | Inputs | Value | -|-----------|---------|---------|----------------------------------------------------|------------------------------------------------|----------------------------------------------------| -| If | Control | 5 | A branching test, sub type of `MultiNode` | A control node and a data predicate node | A tuple of two values: one for true, one for false | -| Region | Control | 5 | A merge point for multiple control flows | An input for each control flow that is merging | Merged control | -| Phi | Data | 5 | A phi function picks a value based on control flow | A Region, and data nodes for each control path | Depends on control flow path taken | -| Stop | Control | 5 | Termination of the program | All return nodes of the function | None | - ## `If` Nodes `If` node takes in both control and data (predicate expression) and routes the @@ -112,51 +112,7 @@ This involves following: updated to point to the `Phi` node. 10. Finally, we set the `Region` node as the control token, and discard the duplicated `ScopeNode`. -Here is the implementing code. - -```java -/** - * Parses a statement - * - * 
- *     if ( expression ) statement [else statement]
- *
- * @return a {@link Node}, never {@code null} - */ -private Node parseIf() { - require("("); - // Parse predicate - var pred = require(parseExpression(), ")"); - // IfNode takes current control and predicate - IfNode ifNode = (IfNode)new IfNode(ctrl(), pred).peephole(); - // Setup projection nodes - Node ifT = new ProjNode(ifNode, 0, "True" ).peephole(); - Node ifF = new ProjNode(ifNode, 1, "False").peephole(); - // In if true branch, the ifT proj node becomes the ctrl - // But first clone the scope and set it as current - int ndefs = _scope.nIns(); - ScopeNode fScope = _scope.dup(); // Duplicate current scope - _allScopes.push(fScope); // For graph visualization we need all scopes - - // Parse the true side - ctrl(ifT); // set ctrl token to ifTrue projection - parseStatement(); // Parse true-side - ScopeNode tScope = _scope; - - // Parse the false side - _scope = fScope; // Restore scope, then parse else block if any - ctrl(ifF); // Ctrl token is now set to ifFalse projection - if (matchx("else")) parseStatement(); - - if( tScope.nIns() != ndefs || fScope.nIns() != ndefs ) - throw error("Cannot define a new name on one arm of an if"); - - // Merge results - _scope = tScope; - _allScopes.pop(); // Discard pushed from graph display - return ctrl(tScope.mergeScopes(fScope)); -} -``` +Implementation is in [`parseIf` method in `Parser`](https://github.com/SeaOfNodes/Simple/blob/main/chapter05/src/main/java/com/seaofnodes/simple/Parser.java#L146-L186). ## Operations on ScopeNodes @@ -172,24 +128,7 @@ Our goals are: 2) Make the new ScopeNode a user of all the bound nodes 3) Ensure that the order of defs in the duplicate is the same to allow easy merging -```java -/** - * Duplicate a ScopeNode; including all levels, up to Nodes. So this is - * neither shallow (would dup the Scope but not the internal HashMap - * tables), nor deep (would dup the Scope, the HashMap tables, but then - * also the program Nodes). - *

- * The new Scope is a full-fledged Node with proper use<->def edges. - */ -public ScopeNode dup() { - ScopeNode dup = new ScopeNode(); - for( HashMap tab : _scopes ) - dup._scopes.push(new HashMap<>(tab)); - for( int i=0; i