perf(linter/plugins): use shift over multiply for powers of 2 (#27536)

Follow on after #27393.

After that PR, `Comment` is now 24 bytes, whereas `Token` is 16 bytes. In Oxlint plugins code, this change required using multiplication to convert from comment index to position in buffer. But `Token`'s size is still a power of 2, so can still use shift for that (faster).

Also, the shift required for these conversions for the tokens/comments/tokens-and-comments buffers were hardcoded in various places. Replace them all with constants - `<< 2` -> `<< TOKEN_SIZE32_SHIFT` - to make is clearer what's going on.

apps/oxlint/src-js/plugins/comments_methods.ts

@@ -12,6 +12,8 @@ import {
   initComments,
   initCommentsBuffer,
 } from "./comments.ts";
+// oxlint-disable-next-line no-unused-vars -- used in inlined `firstTokenAtOrAfter`
+import { TOKEN_SIZE32_SHIFT } from "./tokens.ts";
 import {
   initTokensAndCommentsBuffer,
   tokensAndCommentsInt32,

apps/oxlint/src-js/plugins/tokens.ts

@@ -267,6 +267,8 @@ const TOKEN_DESERIALIZED_FLAG_OFFSET = TOKEN_SIZE - 1;
 
 const TOKEN_SIZE_SHIFT = 4;
 debugAssert(TOKEN_SIZE === 1 << TOKEN_SIZE_SHIFT);
+export const TOKEN_SIZE32_SHIFT = TOKEN_SIZE_SHIFT - 2;
+debugAssert(TOKEN_SIZE32 === 1 << TOKEN_SIZE32_SHIFT);
 
 const KIND_FIELD_OFFSET = 8;
 const IS_ESCAPED_FIELD_OFFSET = 10;
@@ -350,7 +352,7 @@ export function initTokensBuffer(): void {
   const arrayBuffer = buffer.buffer,
     absolutePos = buffer.byteOffset + tokensPos;
   tokensUint8 = new Uint8Array(arrayBuffer, absolutePos, tokensLen << TOKEN_SIZE_SHIFT);
-  tokensInt32 = new Int32Array(arrayBuffer, absolutePos, tokensLen << (TOKEN_SIZE_SHIFT - 2));
+  tokensInt32 = new Int32Array(arrayBuffer, absolutePos, tokensLen << TOKEN_SIZE32_SHIFT);
 
   // Grow caches if needed. After first few files, caches should have grown large enough to service all files.
   // Later files will skip this step, and allocations stop.
@@ -514,7 +516,7 @@ function debugCheckValidRanges(): void {
 
   let lastEnd = 0;
   for (let i = 0; i < tokensLen; i++) {
-    const pos32 = i << 2;
+    const pos32 = i << TOKEN_SIZE32_SHIFT;
     const start = tokensInt32![pos32];
     const end = tokensInt32![pos32 + 1];
     if (end <= start) throw new Error(`Invalid token range: ${start}-${end}`);

apps/oxlint/src-js/plugins/tokens_and_comments.ts

@@ -25,6 +25,7 @@ import {
   tokensLen,
   tokensInt32,
   TOKEN_SIZE32,
+  TOKEN_SIZE32_SHIFT,
 } from "./tokens.ts";
 import { EMPTY_INT32_ARRAY } from "../utils/typed_arrays.ts";
 import { debugAssert, debugAssertIsNonNull } from "../utils/asserts.ts";
@@ -196,7 +197,7 @@ function mergeTokensAndComments(tokensInt32: Int32Array, commentsInt32: Int32Arr
         );
         return;
       }
-      tokenStart = tokensInt32[tokenIndex * TOKEN_SIZE32];
+      tokenStart = tokensInt32[tokenIndex << TOKEN_SIZE32_SHIFT];
     } while (tokenStart < commentStart);
 
     // Process run of comments
@@ -297,7 +298,7 @@ export function getTokenOrCommentEnd(entryIndex: number): number {
   const pos32 = entryIndex << MERGED_SIZE32_SHIFT;
   const originalIndex = tokensAndCommentsInt32![pos32 + MERGED_ORIGINAL_INDEX_OFFSET32];
   return tokensAndCommentsInt32![pos32 + MERGED_TYPE_OFFSET32] === MERGED_TYPE_TOKEN
-    ? tokensInt32![originalIndex * TOKEN_SIZE32 + 1]
+    ? tokensInt32![(originalIndex << TOKEN_SIZE32_SHIFT) + 1]
     : commentsInt32![originalIndex * COMMENT_SIZE32 + 1];
 }
 

apps/oxlint/src-js/plugins/tokens_methods.ts

@@ -2,13 +2,21 @@
  * `SourceCode` methods related to tokens.
  */
 
-import { cachedTokens, tokensInt32, tokensLen, initTokensBuffer, getToken } from "./tokens.ts";
+import {
+  cachedTokens,
+  tokensInt32,
+  tokensLen,
+  initTokensBuffer,
+  getToken,
+  TOKEN_SIZE32_SHIFT,
+} from "./tokens.ts";
 import {
   tokensAndCommentsInt32,
   tokensAndCommentsLen,
   getTokenOrComment,
   getTokenOrCommentEnd,
   initTokensAndCommentsBuffer,
+  MERGED_SIZE32_SHIFT,
 } from "./tokens_and_comments.ts";
 import { debugAssertIsNonNull } from "../utils/asserts.ts";
 
@@ -1290,7 +1298,7 @@ export function getTokenByRangeStart<Options extends RangeOptions | null | undef
   // This makes it safe to use `>> 1` for division by 2 (which is faster than `>>> 1`).
   for (let lo = 0, hi = len; lo < hi;) {
     const mid = (lo + hi) >> 1;
-    const tokenStart = int32[mid << 2];
+    const tokenStart = int32[mid << TOKEN_SIZE32_SHIFT];
     if (tokenStart < offset) {
       lo = mid + 1;
     } else if (tokenStart > offset) {
@@ -1357,7 +1365,7 @@ export function isSpaceBetween(first: NodeOrToken, second: NodeOrToken): boolean
   let index = firstTokenAtOrAfter(tokensAndCommentsInt32, rangeStart, 0, tokensAndCommentsLen);
 
   for (let lastTokenEnd = rangeStart; index < tokensAndCommentsLen; index++) {
-    const tokenStart = tokensAndCommentsInt32[index << 2];
+    const tokenStart = tokensAndCommentsInt32[index << MERGED_SIZE32_SHIFT];
     // The first token of the later node should undergo the check in the second branch
     if (tokenStart > rangeEnd) break;
     if (tokenStart !== lastTokenEnd) return true;
@@ -1413,7 +1421,7 @@ export function isSpaceBetweenTokens(first: NodeOrToken, second: NodeOrToken): b
   let index = firstTokenAtOrAfter(tokensAndCommentsInt32, rangeStart, 0, tokensAndCommentsLen);
 
   for (let lastTokenEnd = rangeStart; index < tokensAndCommentsLen; index++) {
-    const tokenStart = tokensAndCommentsInt32[index << 2];
+    const tokenStart = tokensAndCommentsInt32[index << MERGED_SIZE32_SHIFT];
 
     // The first token of the later node should undergo the check in the second branch
     if (tokenStart > rangeEnd) break;
@@ -1471,7 +1479,7 @@ function getEntry(index: number, includeComments: boolean): TokenOrComment {
  * @returns Start offset in source text
  */
 function entryStart(index: number, int32: Int32Array): number {
-  return int32[index << 2];
+  return int32[index << TOKEN_SIZE32_SHIFT];
 }
 
 /**
@@ -1483,7 +1491,9 @@ function entryStart(index: number, int32: Int32Array): number {
  * @returns End offset in source text
  */
 function entryEnd(index: number, includeComments: boolean): number {
-  return includeComments === true ? getTokenOrCommentEnd(index) : tokensInt32![(index << 2) + 1];
+  return includeComments === true
+    ? getTokenOrCommentEnd(index)
+    : tokensInt32![(index << TOKEN_SIZE32_SHIFT) + 1];
 }
 
 /**
@@ -1550,7 +1560,7 @@ export function firstTokenAtOrAfter(
 ): number {
   for (let endIndex = length; startIndex < endIndex;) {
     const mid = (startIndex + endIndex) >> 1;
-    if (int32[mid << 2] < offset) {
+    if (int32[mid << TOKEN_SIZE32_SHIFT] < offset) {
       startIndex = mid + 1;
     } else {
       endIndex = mid;

apps/oxlint/tsdown_plugins/inline_search.ts

@@ -30,6 +30,8 @@ const { fnParams, returnParamIndex, fnBodySource } = extractInlinedFunction(
  *
  * The function is inlined into all call sites in `FILES` list above.
  *
+ * `TOKEN_SIZE32_SHIFT` constant must be in scope at all call sites.
+ *
  * ```ts
  * // Original code
  * const index = firstTokenAtOrAfter(int32, rangeStart, searchFromIndex, length);
@@ -38,7 +40,7 @@ const { fnParams, returnParamIndex, fnBodySource } = extractInlinedFunction(
  * let index = searchFromIndex;
  * for (let endIndex = length; index < endIndex; ) {
  *   const mid = (index + endIndex) >> 1;
- *   if (int32[mid << 2] < rangeStart) {
+ *   if (int32[mid << TOKEN_SIZE32_SHIFT] < rangeStart) {
  *     index = mid + 1;
  *   } else {
  *     endIndex = mid;