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⚡ Bolt: [performance improvement] Replace indexOf with inline equality checks #32

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⚡ Bolt: [performance improvement] Replace indexOf with inline equality checks #32

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
## 2024-05-25 - Replace indexOf with charCodeAt for Parsing Performance
**Learning:** In the core parsing loops (e.g. `luaparse.js`), using `String.prototype.indexOf` to check if a character matches a small set of options (like checking if a character is 'e' or 'E') creates significant overhead because it is executed millions of times. Inline checking using `charCodeAt` or direct equality (`===`) is much faster and avoids function call and string operations overhead.
**Action:** When working on lexer/parser performance optimizations under "Bolt" persona, prioritize converting single-character `indexOf` string checks into inline strict equality operations (`charCodeAt` or `===`) for parsing tight loops.
39 changes: 26 additions & 13 deletions luaparse.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1011,7 +1011,7 @@
var character = input.charAt(index)
, next = input.charAt(index + 1);

var literal = ('0' === character && 'xX'.indexOf(next || null) >= 0) ?
var literal = ('0' === character && (next === 'x' || next === 'X')) ?
readHexLiteral() : readDecLiteral();

var foundImaginaryUnit = readImaginaryUnitSuffix()
Expand All @@ -1035,7 +1035,8 @@

// Imaginary unit number suffix is optional.
// See http://luajit.org/ext_ffi_api.html#literals
if ('iI'.indexOf(input.charAt(index) || null) >= 0) {
var c = input.charCodeAt(index);
if (c === 105 || c === 73) {
++index;
return true;
} else {
Expand All @@ -1049,11 +1050,14 @@
// Int64/uint64 number suffix is optional.
// See http://luajit.org/ext_ffi_api.html#literals

if ('uU'.indexOf(input.charAt(index) || null) >= 0) {
var c1 = input.charCodeAt(index);
if (c1 === 117 || c1 === 85) {
++index;
if ('lL'.indexOf(input.charAt(index) || null) >= 0) {
var c2 = input.charCodeAt(index);
if (c2 === 108 || c2 === 76) {
++index;
if ('lL'.indexOf(input.charAt(index) || null) >= 0) {
var c3 = input.charCodeAt(index);
if (c3 === 108 || c3 === 76) {
++index;
return 'ULL';
} else {
Expand All @@ -1064,9 +1068,10 @@
// U but no L
raise(null, errors.malformedNumber, input.slice(tokenStart, index));
}
} else if ('lL'.indexOf(input.charAt(index) || null) >= 0) {
} else if (c1 === 108 || c1 === 76) {
++index;
if ('lL'.indexOf(input.charAt(index) || null) >= 0) {
var c2 = input.charCodeAt(index);
if (c2 === 108 || c2 === 76) {
++index;
Comment on lines +1071 to 1075
return 'LL';
} else {
Expand Down Expand Up @@ -1119,13 +1124,17 @@

// Binary exponents are optional
var foundBinaryExponent = false;
if ('pP'.indexOf(input.charAt(index) || null) >= 0) {
var c = input.charCodeAt(index);
if (c === 112 || c === 80) {
foundBinaryExponent = true;
++index;

// Sign part is optional and defaults to 1 (positive).
if ('+-'.indexOf(input.charAt(index) || null) >= 0)
binarySign = ('+' === input.charAt(index++)) ? 1 : -1;
var signC = input.charCodeAt(index);
if (signC === 43 || signC === 45) {
binarySign = (signC === 43) ? 1 : -1;
++index;
}

exponentStart = index;

Expand Down Expand Up @@ -1163,11 +1172,15 @@

// Exponent part is optional.
var foundExponent = false;
if ('eE'.indexOf(input.charAt(index) || null) >= 0) {
var c = input.charCodeAt(index);
if (c === 101 || c === 69) {
foundExponent = true;
++index;
// Sign part is optional.
if ('+-'.indexOf(input.charAt(index) || null) >= 0) ++index;
var signC = input.charCodeAt(index);
if (signC === 43 || signC === 45) {
++index;
}
// An exponent is required to contain at least one decimal digit.
if (!isDecDigit(input.charCodeAt(index)))
raise(null, errors.malformedNumber, input.slice(tokenStart, index));
Expand Down Expand Up @@ -1491,7 +1504,7 @@
}

function isUnary(token) {
if (Punctuator === token.type) return '#-~'.indexOf(token.value) >= 0;
if (Punctuator === token.type) return token.value === '#' || token.value === '-' || token.value === '~';
if (Keyword === token.type) return 'not' === token.value;
return false;
}
Expand Down