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Construct new stack tables with the correct column lengths #5906

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Merged
canova merged 2 commits into from
Mar 24, 2026
+115 −42
Merged

Construct new stack tables with the correct column lengths #5906

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d3302f4
Construct new stack tables with the correct column lengths.
mstange Mar 23, 2026
a6bf146
Merge branch 'main' into push-qvywvmzzsttt
canova Mar 24, 2026
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15 changes: 0 additions & 15 deletions src/profile-logic/data-structures.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,6 @@ import type {
RawSamplesTable,
FrameTable,
RawStackTable,
StackTable,
FuncTable,
RawMarkerTable,
JsAllocationsTable,
Expand All @@ -33,20 +32,6 @@ import type {
* This module collects all of the creation of new empty profile data structures.
*/

export function getEmptyStackTable(): StackTable {
return {
// Important!
// If modifying this structure, please update all callers of this function to ensure
// that they are pushing on correctly to the data structure. These pushes may not
// be caught by the type system.
frame: [],
prefix: [],
category: new Uint8Array(),
subcategory: new Uint8Array(),
length: 0,
};
}

export function getEmptySamplesTable(): RawSamplesTable {
return {
// Important!
Expand Down
29 changes: 29 additions & 0 deletions src/profile-logic/profile-data.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2714,6 +2714,34 @@ export function createThreadFromDerivedTables(
return thread;
}

/**
* Throws if the column lengths of a StackTable don't match stackTable.length.
* Call this after constructing a new StackTable to catch bugs early.
*/
export function validateStackTableShape(stackTable: StackTable): void {
const { length, frame, prefix, category, subcategory } = stackTable;
if (frame.length !== length) {
throw new Error(
`StackTable frame column length ${frame.length} does not match stackTable.length ${length}`
);
}
if (prefix.length !== length) {
throw new Error(
`StackTable prefix column length ${prefix.length} does not match stackTable.length ${length}`
);
}
if (category.length !== length) {
throw new Error(
`StackTable category column length ${category.length} does not match stackTable.length ${length}`
);
}
if (subcategory.length !== length) {
throw new Error(
`StackTable subcategory column length ${subcategory.length} does not match stackTable.length ${length}`
);
}
}

/**
* Sometimes we want to update the stacks for a thread, for instance while searching
* for a text string, or doing a call tree transformation. This function abstracts
Expand All @@ -2738,6 +2766,7 @@ export function updateThreadStacksByGeneratingNewStackColumns(
markerData: Array<MarkerPayload | null>
) => Array<MarkerPayload | null>
): Thread {
validateStackTableShape(newStackTable);
const { jsAllocations, nativeAllocations, samples, markers } = thread;

const newSamples = {
Expand Down
113 changes: 86 additions & 27 deletions src/profile-logic/transforms.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,6 @@ import {
getSearchFilteredMarkerIndexes,
stringsToMarkerRegExps,
} from '../profile-logic/marker-data';
import { getEmptyStackTable } from './data-structures';
import { getFunctionName } from './function-info';
import { splitSearchString } from '../utils/string';

Expand Down Expand Up @@ -766,7 +765,11 @@ export function mergeCallNode(
// A root stack's prefix will be null. Maintain that relationship from old to new
// stacks by mapping from null to null.
oldStackToNewStack.set(null, null);
const newStackTable = getEmptyStackTable();
const newFrameCol = [];
const newPrefixCol = [];
const newCategoryCol = [];
const newSubcategoryCol = [];
let newLength = 0;
// Provide two arrays to efficiently cache values for the algorithm. This probably
// could be refactored to use only one array here.
const stackDepths = [];
Expand Down Expand Up @@ -822,17 +825,28 @@ export function mergeCallNode(
newStackPrefix === undefined ? null : newStackPrefix
);
} else {
const newStackIndex = newStackTable.length++;
const newStackIndex = newLength++;
const newStackPrefix = oldStackToNewStack.get(prefix);
newStackTable.prefix[newStackIndex] =
newPrefixCol[newStackIndex] =
newStackPrefix === undefined ? null : newStackPrefix;
newStackTable.frame[newStackIndex] = frameIndex;
newStackTable.category[newStackIndex] = category;
newStackTable.subcategory[newStackIndex] = subcategory;
newFrameCol[newStackIndex] = frameIndex;
newCategoryCol[newStackIndex] = category;
newSubcategoryCol[newStackIndex] = subcategory;
oldStackToNewStack.set(stackIndex, newStackIndex);
}
}

const newStackTable = {
frame: newFrameCol,
prefix: newPrefixCol,
category: new Uint8Array(newCategoryCol),
subcategory:
stackTable.subcategory instanceof Uint8Array
? new Uint8Array(newSubcategoryCol)
: new Uint16Array(newSubcategoryCol),
length: newLength,
};

return updateThreadStacks(
thread,
newStackTable,
Expand Down Expand Up @@ -1247,7 +1261,11 @@ export function focusSubtree(
// A root stack's prefix will be null. Maintain that relationship from old to new
// stacks by mapping from null to null.
oldStackToNewStack.set(null, null);
const newStackTable = getEmptyStackTable();
const newFrameCol = [];
const newPrefixCol = [];
const newCategoryCol = [];
const newSubcategoryCol = [];
let newLength = 0;
for (let stackIndex = 0; stackIndex < stackTable.length; stackIndex++) {
const prefix = stackTable.prefix[stackIndex];
const prefixMatchesUpTo = prefix !== null ? stackMatches[prefix] : 0;
Expand All @@ -1267,18 +1285,29 @@ export function focusSubtree(
}
}
if (stackMatchesUpTo === prefixDepth) {
const newStackIndex = newStackTable.length++;
const newStackIndex = newLength++;
const newStackPrefix = oldStackToNewStack.get(prefix);
newStackTable.prefix[newStackIndex] = newStackPrefix ?? null;
newStackTable.frame[newStackIndex] = frame;
newStackTable.category[newStackIndex] = category;
newStackTable.subcategory[newStackIndex] = subcategory;
newPrefixCol[newStackIndex] = newStackPrefix ?? null;
newFrameCol[newStackIndex] = frame;
newCategoryCol[newStackIndex] = category;
newSubcategoryCol[newStackIndex] = subcategory;
oldStackToNewStack.set(stackIndex, newStackIndex);
}
}
stackMatches[stackIndex] = stackMatchesUpTo;
}

const newStackTable = {
frame: newFrameCol,
prefix: newPrefixCol,
category: new Uint8Array(newCategoryCol),
subcategory:
stackTable.subcategory instanceof Uint8Array
? new Uint8Array(newSubcategoryCol)
: new Uint16Array(newSubcategoryCol),
length: newLength,
};

return updateThreadStacks(thread, newStackTable, (oldStack) => {
if (oldStack === null || stackMatches[oldStack] !== prefixDepth) {
return null;
Expand Down Expand Up @@ -1359,7 +1388,12 @@ export function focusFunction(
// Typed arrays are initialized to zero, which we interpret as null.
const oldStackToNewStackPlusOne = new Uint32Array(stackTable.length);

const newStackTable = getEmptyStackTable();
const newFrameCol = [];
const newPrefixCol = [];
const newCategoryCol = [];
const newSubcategoryCol = [];
let newLength = 0;

for (let stackIndex = 0; stackIndex < stackTable.length; stackIndex++) {
const prefix = stackTable.prefix[stackIndex];
const frameIndex = stackTable.frame[stackIndex];
Expand All @@ -1369,16 +1403,26 @@ export function focusFunction(
prefix === null ? 0 : oldStackToNewStackPlusOne[prefix];
const newPrefix = newPrefixPlusOne === 0 ? null : newPrefixPlusOne - 1;
if (newPrefix !== null || funcIndex === funcIndexToFocus) {
const newStackIndex = newStackTable.length++;
newStackTable.prefix[newStackIndex] = newPrefix;
newStackTable.frame[newStackIndex] = frameIndex;
newStackTable.category[newStackIndex] = stackTable.category[stackIndex];
newStackTable.subcategory[newStackIndex] =
stackTable.subcategory[stackIndex];
const newStackIndex = newLength++;
newPrefixCol[newStackIndex] = newPrefix;
newFrameCol[newStackIndex] = frameIndex;
newCategoryCol[newStackIndex] = stackTable.category[stackIndex];
newSubcategoryCol[newStackIndex] = stackTable.subcategory[stackIndex];
oldStackToNewStackPlusOne[stackIndex] = newStackIndex + 1;
}
}

const newStackTable = {
frame: newFrameCol,
prefix: newPrefixCol,
category: new Uint8Array(newCategoryCol),
subcategory:
stackTable.subcategory instanceof Uint8Array
? new Uint8Array(newSubcategoryCol)
: new Uint16Array(newSubcategoryCol),
length: newLength,
};

return updateThreadStacks(thread, newStackTable, (oldStack) => {
if (oldStack === null) {
return null;
Expand Down Expand Up @@ -1445,7 +1489,11 @@ export function focusCategory(thread: Thread, category: IndexIntoCategoryList) {
> = new Map();
oldStackToNewStack.set(null, null);

const newStackTable = getEmptyStackTable();
const newFrameCol = [];
const newPrefixCol = [];
const newCategoryCol = [];
const newSubcategoryCol = [];
let newLength = 0;

// fill the new stack table with the kept frames
for (let stackIndex = 0; stackIndex < stackTable.length; stackIndex++) {
Expand All @@ -1460,14 +1508,25 @@ export function focusCategory(thread: Thread, category: IndexIntoCategoryList) {
continue;
}

const newStackIndex = newStackTable.length++;
newStackTable.prefix[newStackIndex] = newPrefix;
newStackTable.frame[newStackIndex] = stackTable.frame[stackIndex];
newStackTable.category[newStackIndex] = stackTable.category[stackIndex];
newStackTable.subcategory[newStackIndex] =
stackTable.subcategory[stackIndex];
const newStackIndex = newLength++;
newPrefixCol[newStackIndex] = newPrefix;
newFrameCol[newStackIndex] = stackTable.frame[stackIndex];
newCategoryCol[newStackIndex] = stackTable.category[stackIndex];
newSubcategoryCol[newStackIndex] = stackTable.subcategory[stackIndex];
oldStackToNewStack.set(stackIndex, newStackIndex);
}

const newStackTable = {
frame: newFrameCol,
prefix: newPrefixCol,
category: new Uint8Array(newCategoryCol),
subcategory:
stackTable.subcategory instanceof Uint8Array
? new Uint8Array(newSubcategoryCol)
: new Uint16Array(newSubcategoryCol),
length: newLength,
};

const updated = updateThreadStacks(
thread,
newStackTable,
Expand Down