Fix NormalizeToSubset creating duplicate decomp_N symbols #216

Copilot · 2025-11-05T02:37:35Z

NormalizeToSubset generates duplicate decomp_N variable names when (1) the function already contains variables matching this pattern, or (2) normalization is applied multiple times to the same AST region.

Changes

Symbol table tracking

StatementDecomposer now builds a symbol table of existing variable/parameter names per function
Skips decomp_N names already in use, incrementing until finding an available name
Symbol table is cached per function and rebuilt when crossing function boundaries

Global ID generation option

Added useGlobalIds parameter (default: false) to use IdGenerator.next("decomp_")
Ensures unique names across multiple normalization passes without symbol table lookups
Exposed via NormalizeToSubset options parameter

Usage

Default behavior prevents duplicates within a single normalization:

NormalizeToSubset(functionJp);  // Avoids existing decomp_N variables

For multiple normalization passes, use global IDs:

NormalizeToSubset(functionJp, { useGlobalIds: true });
NormalizeToSubset(functionJp, { useGlobalIds: true });  // No conflicts

Original prompt

This section details on the original issue you should resolve

<issue_title>NormalizeToSubset is creating duplicated symbols</issue_title>
<issue_description>NormalizeToSubset, whenever it needs to create a new variable, assigns names based on the pattern "decomp_N", where N is the Nth variable created for that function.

The problem, however, is that if the function already contains variables that follow this pattern, e.g., decomp_0, the transformation will create another variable called decomp_0, as it doesn't check for clashing names. I think the fix here is two-fold:

Create a symbol table of variable decls and params of the function before normalizing, and skip generating a decomp_N symbol if they already exist in the table;

As this problem arises predominantly (but not always) from applying normalization multiple times over the same AST region, I suggest adding an option to use a global N, instead of having it be local to the function. That way, the transform will never generate two clashing decomp_N symbols, no matter how many times it's called over any part of the AST. Using IdGenerator.next("decomp_") would take care of this.</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes NormalizeToSubset is creating duplicated symbols #215

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- Add symbol table to StatementDecomposer to track existing variable names - Check symbol table before generating new decomp_N variable names - Add useGlobalIds option to use global IdGenerator for unique names across multiple normalizations - Update NormalizeToSubset to support useGlobalIds option - Add test cases for duplicate symbol detection Co-authored-by: tiagolascasas <[email protected]>

Co-authored-by: tiagolascasas <[email protected]>

- Track current function to avoid rebuilding symbol table unnecessarily - Rebuild symbol table when moving to a different function - This prevents stale symbol tables when the same decomposer is used across different function scopes Co-authored-by: tiagolascasas <[email protected]>

lm-sousa · 2025-11-06T14:26:22Z

Clava-JS/src-api/clava/opt/NormalizeToSubset.ts

+import type { Joinpoint } from "../../Joinpoints.js";
+import { BinaryOp } from "../../Joinpoints.js";


Suggested change

import type { Joinpoint } from "../../Joinpoints.js";

import { BinaryOp } from "../../Joinpoints.js";

import type { BinaryOp, type Joinpoint } from "../../Joinpoints.js";

lm-sousa · 2025-11-06T14:27:04Z

Clava-JS/src-api/clava/opt/NormalizeToSubset.example.md

Don't add random docs.

Copilot

Pull Request Overview

This pull request adds symbol table management to the StatementDecomposer to prevent duplicate variable names when normalizing code. The changes introduce a useGlobalIds option and improve variable name generation to avoid conflicts with existing variables.

Adds symbol table tracking to detect existing variable names before generating new ones
Introduces useGlobalIds option for globally unique name generation across multiple normalizations
Updates documentation and adds tests for duplicate symbol prevention

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
Clava-JS/src-api/clava/opt/NormalizeToSubset.ts	Adds `useGlobalIds` option and passes it to `StatementDecomposer` constructor
Clava-JS/src-api/clava/opt/NormalizeToSubset.example.md	New documentation file with usage examples for the normalization function
Clava-JS/src-api/clava/code/StatementDecomposer.ts	Implements symbol table building and duplicate name checking logic
Clava-JS/src-api/clava/code/StatementDecomposer.test.ts	New test file verifying no duplicate symbols are created during normalization

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Copilot · 2025-11-06T14:32:30Z

Clava-JS/src-api/clava/code/StatementDecomposer.ts

+    // If we're in the same function as before, reuse the symbol table
+    if ($function === this.currentFunction && this.symbolTable !== undefined) {
+      return;
+    }
+


The symbol table caching logic has a bug. When the same StatementDecomposer instance is used to process the same function multiple times (e.g., by different passes in NormalizeToSubset), the symbol table is cached and reused. However, since variables are added to the AST during processing, the cached symbol table becomes stale and doesn't include newly added variables. This can lead to duplicate variable names being generated.

The condition if ($function === this.currentFunction && this.symbolTable !== undefined) should be removed, and the symbol table should be rebuilt on every call to ensure it accurately reflects the current state of the AST.

Suggested change

// If we're in the same function as before, reuse the symbol table

if ($function === this.currentFunction && this.symbolTable !== undefined) {

return;

}

// Always rebuild the symbol table to reflect the current state of the AST

Copilot · 2025-11-06T14:32:31Z

Clava-JS/src-api/clava/opt/NormalizeToSubset.ts

+    simplifyLoops: { forToWhile: true },
+    useGlobalIds: false,
+    ...options


The options merging logic doesn't properly handle partial simplifyLoops objects. If a user passes { simplifyLoops: {} }, the spread operator will completely overwrite the default { forToWhile: true }, resulting in { forToWhile: undefined } instead of keeping the default value.

Consider using a deeper merge strategy:

const _options = { simplifyLoops: { forToWhile: true, ...options.simplifyLoops }, useGlobalIds: options.useGlobalIds ?? false, };

Suggested change

simplifyLoops: { forToWhile: true },

useGlobalIds: false,

...options

simplifyLoops: { forToWhile: true, ...(options.simplifyLoops ?? {}) },

useGlobalIds: options.useGlobalIds ?? false,

Copilot · 2025-11-06T14:32:31Z

Clava-JS/src-api/clava/code/StatementDecomposer.ts

-    const varName = `${this.tempPrefix}${this.startIndex}`;
+    if (this.useGlobalIds) {
+      // Use global IdGenerator to ensure unique names across multiple normalizations
+      return IdGenerator.next(this.tempPrefix);


When useGlobalIds is true, the newTempVarname() method uses IdGenerator.next() but doesn't check the generated name against existing variables in the symbol table. This could create naming conflicts if the source code already contains variables like decomp_N that happen to match names generated by the IdGenerator.

Consider adding a check against the symbol table even when using global IDs:

if (this.useGlobalIds) { let varName = IdGenerator.next(this.tempPrefix); // Ensure uniqueness against existing variables if (this.symbolTable !== undefined) { while (this.symbolTable.has(varName)) { varName = IdGenerator.next(this.tempPrefix); } this.symbolTable.add(varName); } return varName; }

Suggested change

return IdGenerator.next(this.tempPrefix);

let varName = IdGenerator.next(this.tempPrefix);

// Ensure uniqueness against existing variables in the symbol table

if (this.symbolTable !== undefined) {

while (this.symbolTable.has(varName)) {

varName = IdGenerator.next(this.tempPrefix);

}

this.symbolTable.add(varName);

}

return varName;

Copilot · 2025-11-06T14:32:32Z

Clava-JS/src-api/clava/code/StatementDecomposer.test.ts

+      }
+    }
+
+    for (const [varName, count] of Object.entries(decompCounts)) {


Unused variable varName.

Suggested change

for (const [varName, count] of Object.entries(decompCounts)) {

for (const [, count] of Object.entries(decompCounts)) {

lm-sousa · 2025-11-07T16:43:44Z

@tiagolascasas Tens aqui muita coisa para ver. Mesmo que não se ande para a frente com este PR, o Copilot encontrou vários bugs na implementação que devem ser corrigidos.

Initial plan

be36240

Copilot AI assigned Copilot and tiagolascasas Nov 5, 2025

Copilot started work on behalf of tiagolascasas November 5, 2025 02:37 View session

Copilot AI and others added 3 commits November 5, 2025 02:47

Add documentation and examples for NormalizeToSubset changes

7af746e

Co-authored-by: tiagolascasas <[email protected]>

Copilot AI changed the title ~~[WIP] Fix duplicated symbols in NormalizeToSubset~~ Fix NormalizeToSubset creating duplicate decomp_N symbols Nov 5, 2025

Copilot AI requested a review from tiagolascasas November 5, 2025 02:54

Copilot finished work on behalf of tiagolascasas November 5, 2025 02:54

lm-sousa requested changes Nov 6, 2025

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lm-sousa requested a review from Copilot November 6, 2025 14:28

Copilot AI reviewed Nov 6, 2025

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Fix NormalizeToSubset creating duplicate decomp_N symbols #216

Fix NormalizeToSubset creating duplicate decomp_N symbols #216

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Copilot AI commented Nov 5, 2025 •

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		import type { Joinpoint } from "../../Joinpoints.js";
		import { BinaryOp } from "../../Joinpoints.js";

	import type { Joinpoint } from "../../Joinpoints.js";
	import { BinaryOp } from "../../Joinpoints.js";
	import type { BinaryOp, type Joinpoint } from "../../Joinpoints.js";

-      return IdGenerator.next(this.tempPrefix);
+      let varName = IdGenerator.next(this.tempPrefix);
+      // Ensure uniqueness against existing variables in the symbol table
+      if (this.symbolTable !== undefined) {
+        while (this.symbolTable.has(varName)) {
+          varName = IdGenerator.next(this.tempPrefix);
+        }
+        this.symbolTable.add(varName);
+      }
+      return varName;

	for (const [varName, count] of Object.entries(decompCounts)) {
	for (const [, count] of Object.entries(decompCounts)) {

Fix NormalizeToSubset creating duplicate decomp_N symbols #216

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Fix NormalizeToSubset creating duplicate decomp_N symbols #216

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Changes

Symbol table tracking

Global ID generation option

Usage

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