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executable file
·1965 lines (1853 loc) · 62.8 KB
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#!/usr/bin/env node
import * as acorn from 'acorn';
import importPhases from 'acorn-import-phases';
import {minify_sync} from 'terser';
import * as fs from 'node:fs';
import assert from 'node:assert';
import {parseArgs} from 'node:util';
// Extend acorn to understand source-phase import syntax
// (`import source foo from './bar.wasm'`) emitted under -sSOURCE_PHASE_IMPORTS.
// The plugin annotates ImportDeclaration nodes with a `phase` field; terser
// carries this through from_mozilla_ast / to_mozilla_ast and emits it back on
// output.
const parser = acorn.Parser.extend(importPhases());
// Utilities
function read(x) {
return fs.readFileSync(x, 'utf-8');
}
function assertAt(condition, node, message = '') {
if (!condition) {
if (!process.env.EMCC_DEBUG_SAVE) {
message += ' (use EMCC_DEBUG_SAVE=1 to preserve temporary inputs)';
}
let err = new Error(message);
err['loc'] = acorn.getLineInfo(input, node.start);
throw err;
}
}
// Visits and walks
// (We don't use acorn-walk because it ignores x in 'x = y'.)
function visitChildren(node, c) {
// emptyOut() and temporary ignoring may mark nodes as empty,
// while they have properties with children we should ignore.
if (node.type === 'EmptyStatement') {
return;
}
function maybeChild(child) {
if (typeof child?.type === 'string') {
c(child);
return true;
}
return false;
}
for (const child of Object.values(node)) {
// Check for a child.
if (!maybeChild(child)) {
// Check for an array of children.
if (Array.isArray(child)) {
child.forEach(maybeChild);
}
}
}
}
// Simple post-order walk, calling properties on an object by node type,
// if the type exists.
function simpleWalk(node, cs) {
visitChildren(node, (child) => simpleWalk(child, cs));
if (node.type in cs) {
cs[node.type](node);
}
}
// Full post-order walk, calling a single function for all types. If |pre| is
// provided, it is called in pre-order (before children). If |pre| returns
// `false`, the node and its children will be skipped.
function fullWalk(node, c, pre) {
if (pre?.(node) !== false) {
visitChildren(node, (child) => fullWalk(child, c, pre));
c(node);
}
}
// Recursive post-order walk, calling properties on an object by node type,
// if the type exists, and if so leaving recursion to that function.
function recursiveWalk(node, cs) {
(function c(node) {
if (!(node.type in cs)) {
visitChildren(node, (child) => recursiveWalk(child, cs));
} else {
cs[node.type](node, c);
}
})(node);
}
// AST Utilities
function emptyOut(node) {
node.type = 'EmptyStatement';
}
function setLiteralValue(item, value) {
item.value = value;
item.raw = null;
}
function isLiteralString(node) {
return node.type === 'Literal' && typeof node.value === 'string';
}
function dump(node) {
console.log(JSON.stringify(node, null, ' '));
}
// Traverse a pattern node (identifier, object/array pattern, etc) invoking onExpr on any nested expressions and onBoundIdent on any bound identifiers.
function walkPattern(node, onExpr, onBoundIdent) {
recursiveWalk(node, {
AssignmentPattern(node, c) {
c(node.left);
onExpr(node.right);
},
Property(node, c) {
if (node.computed) {
onExpr(node.key);
}
c(node.value);
},
Identifier({name}) {
onBoundIdent(name);
},
});
}
function hasSideEffects(node) {
// Conservative analysis.
let has = false;
fullWalk(
node,
(node) => {
switch (node.type) {
case 'ExpressionStatement':
if (node.directive) {
has = true;
}
break;
// TODO: go through all the ESTree spec
case 'Literal':
case 'Identifier':
case 'UnaryExpression':
case 'BinaryExpression':
case 'LogicalExpression':
case 'UpdateOperator':
case 'ConditionalExpression':
case 'VariableDeclaration':
case 'VariableDeclarator':
case 'ObjectExpression':
case 'Property':
case 'SpreadElement':
case 'BlockStatement':
case 'ArrayExpression':
case 'EmptyStatement': {
break; // safe
}
case 'MemberExpression': {
// safe if on Math (or other familiar objects, TODO)
if (node.object.type !== 'Identifier' || node.object.name !== 'Math') {
// console.error('because member on ' + node.object.name);
has = true;
}
break;
}
case 'NewExpression': {
// default to unsafe, but can be safe on some familiar objects
if (node.callee.type === 'Identifier') {
const name = node.callee.name;
if (
name === 'TextDecoder' ||
name === 'ArrayBuffer' ||
name === 'Int8Array' ||
name === 'Uint8Array' ||
name === 'Int16Array' ||
name === 'Uint16Array' ||
name === 'Int32Array' ||
name === 'Uint32Array' ||
name === 'Float32Array' ||
name === 'Float64Array'
) {
// no side effects, but the arguments might (we walk them in
// full walk as well)
break;
}
}
// not one of the safe cases
has = true;
break;
}
default: {
has = true;
}
}
},
(node) =>
// Ignore inner scopes.
!['FunctionDeclaration', 'FunctionExpression', 'ArrowFunctionExpression'].includes(node.type),
);
return has;
}
// Passes
// Removes obviously-unused code. Similar to closure compiler in its rules -
// export e.g. by Module['..'] = theThing; , or use it somewhere, otherwise
// it goes away.
//
// Note that this is somewhat conservative, since the ESTree AST does not
// have a simple separation between definitions and uses, e.g.
// Identifier is used both for the x in function foo(x) {
// and for y = x + 1 . That means we need to consider new ES6+ constructs
// as they appear (like ArrowFunctionExpression). Instead, we do a conservative
// analysis here.
function JSDCE(ast, aggressive) {
function iteration() {
let removed = 0;
const scopes = [{}]; // begin with empty toplevel scope
function ensureData(scope, name) {
if (Object.prototype.hasOwnProperty.call(scope, name)) return scope[name];
scope[name] = {
def: 0,
use: 0,
param: 0, // true for function params, which cannot be eliminated
};
return scope[name];
}
function cleanUp(ast, names) {
recursiveWalk(ast, {
ForStatement(node, c) {
visitChildren(node, c);
// If we had `for (var x = ...; ...)` and we removed `x`, we need to change to `for (; ...)`.
if (node.init?.type === 'EmptyStatement') {
node.init = null;
}
},
ForInStatement(node, c) {
// We can't remove the var in a for-in, as that would result in an invalid syntax. Skip the LHS.
c(node.right);
c(node.body);
},
ForOfStatement(node, c) {
// We can't remove the var in a for-of, as that would result in an invalid syntax. Skip the LHS.
c(node.right);
c(node.body);
},
VariableDeclaration(node, _c) {
let removedHere = 0;
node.declarations = node.declarations.filter((node) => {
assert(node.type === 'VariableDeclarator');
let keep = node.init && hasSideEffects(node.init);
walkPattern(
node.id,
(value) => {
keep ||= hasSideEffects(value);
},
(boundName) => {
keep ||= !names.has(boundName);
},
);
if (!keep) removedHere = 1;
return keep;
});
removed += removedHere;
if (node.declarations.length === 0) {
emptyOut(node);
}
},
ExpressionStatement(node, _c) {
if (aggressive && !hasSideEffects(node)) {
emptyOut(node);
removed++;
}
},
FunctionDeclaration(node, _c) {
if (names.has(node.id.name)) {
removed++;
emptyOut(node);
return;
}
// do not recurse into other scopes
},
// do not recurse into other scopes
FunctionExpression() {},
ArrowFunctionExpression() {},
});
}
function handleFunction(node, c, defun) {
// defun names matter - function names (the y in var x = function y() {..}) are just for stack traces.
if (defun) {
ensureData(scopes[scopes.length - 1], node.id.name).def = 1;
}
const scope = {};
scopes.push(scope);
for (const param of node.params) {
walkPattern(param, c, (name) => {
ensureData(scope, name).def = 1;
scope[name].param = 1;
});
}
c(node.body);
// we can ignore self-references, i.e., references to ourselves inside
// ourselves, for named defined (defun) functions
const ownName = defun ? node.id.name : '';
const names = new Set();
for (const name in scopes.pop()) {
if (name === ownName) continue;
const data = scope[name];
if (data.use && !data.def) {
// this is used from a higher scope, propagate the use down
ensureData(scopes[scopes.length - 1], name).use = 1;
continue;
}
if (data.def && !data.use && !data.param) {
// this is eliminatable!
names.add(name);
}
}
cleanUp(node.body, names);
}
recursiveWalk(ast, {
VariableDeclarator(node, c) {
walkPattern(node.id, c, (name) => {
ensureData(scopes[scopes.length - 1], name).def = 1;
});
if (node.init) c(node.init);
},
ObjectExpression(node, c) {
// ignore the property identifiers
node.properties.forEach((node) => {
if (node.value) {
c(node.value);
} else if (node.argument) {
c(node.argument);
}
});
},
MemberExpression(node, c) {
c(node.object);
// Ignore a property identifier (a.X), but notice a[X] (computed props).
if (node.computed) {
c(node.property);
}
},
FunctionDeclaration(node, c) {
handleFunction(node, c, true /* defun */);
},
FunctionExpression(node, c) {
handleFunction(node, c);
},
ArrowFunctionExpression(node, c) {
handleFunction(node, c);
},
Identifier(node, _c) {
const name = node.name;
ensureData(scopes[scopes.length - 1], name).use = 1;
},
ExportDefaultDeclaration(node, c) {
const name = node.declaration.id.name;
ensureData(scopes[scopes.length - 1], name).use = 1;
c(node.declaration);
},
ExportNamedDeclaration(node, c) {
if (node.declaration) {
if (node.declaration.type == 'FunctionDeclaration') {
const name = node.declaration.id.name;
ensureData(scopes[scopes.length - 1], name).use = 1;
} else {
assert(node.declaration.type == 'VariableDeclaration');
for (const decl of node.declaration.declarations) {
const name = decl.id.name;
ensureData(scopes[scopes.length - 1], name).use = 1;
}
}
c(node.declaration);
} else {
for (const specifier of node.specifiers) {
const name = specifier.local.name;
ensureData(scopes[scopes.length - 1], name).use = 1;
}
}
},
});
// toplevel
const scope = scopes.pop();
assert(scopes.length === 0);
const names = new Set();
for (const [name, data] of Object.entries(scope)) {
if (data.def && !data.use) {
assert(!data.param); // can't be
// this is eliminatable!
names.add(name);
}
}
cleanUp(ast, names);
return removed;
}
while (iteration() && aggressive) {} // eslint-disable-line no-empty
}
// Aggressive JSDCE - multiple iterations
function AJSDCE(ast) {
JSDCE(ast, /* aggressive= */ true);
}
function isWasmImportsAssign(node) {
// var wasmImports = ..
// or
// wasmImports = ..
if (
node.type === 'AssignmentExpression' &&
node.left.name == 'wasmImports' &&
node.right.type == 'ObjectExpression'
) {
return true;
}
return (
node.type === 'VariableDeclaration' &&
node.declarations.length === 1 &&
node.declarations[0].id.name === 'wasmImports' &&
node.declarations[0].init &&
node.declarations[0].init.type === 'ObjectExpression'
);
}
function getWasmImportsValue(node) {
if (node.declarations) {
return node.declarations[0].init;
} else {
return node.right;
}
}
// Under WASM_ESM_INTEGRATION the wasm exports are received as a native ES
// import from the wasm module itself:
// import { malloc as _malloc, memory } from './a.out.wasm';
function isImportFromWasm(node) {
return (
node.type === 'ImportDeclaration' &&
// Skip source/defer phase imports (e.g. `import source foo from './a.wasm'`
// under SOURCE_PHASE_IMPORTS), whose default specifier binds the module
// itself rather than wasm exports. Value-phase imports leave `phase` unset.
!node.phase &&
isLiteralString(node.source) &&
node.source.value.endsWith('.wasm')
);
}
// A sourceless `export { a as b, .. };` statement (not `export <decl>` and not
// a re-export `export {..} from '..'`).
function isExportSpecifierList(node) {
return (
node.type === 'ExportNamedDeclaration' && !node.declaration && !node.source
);
}
function isExportUse(node) {
// Match usages of symbols on the `wasmExports` object. e.g:
// wasmExports['X']
// `origExports` holds the unwrapped exports in applySignatureConversions.
return (
node.type === 'MemberExpression' &&
node.object.type === 'Identifier' &&
isLiteralString(node.property) &&
(node.object.name === 'wasmExports' || node.object.name === 'origExports')
);
}
function getExportOrModuleUseName(node) {
return node.property.value;
}
function isModuleUse(node) {
return (
node.type === 'MemberExpression' && // Module['X']
node.object.type === 'Identifier' &&
node.object.name === 'Module' &&
isLiteralString(node.property)
);
}
// Apply import/export name changes (after minifying them)
function applyImportAndExportNameChanges(ast) {
const mapping = extraInfo.mapping;
fullWalk(ast, (node) => {
if (isWasmImportsAssign(node)) {
const assignedObject = getWasmImportsValue(node);
assignedObject.properties.forEach((item) => {
if (mapping[item.key.name]) {
item.key.name = mapping[item.key.name];
}
});
} else if (node.type === 'AssignmentExpression') {
const value = node.right;
if (isExportUse(value)) {
const name = value.property.value;
if (mapping[name]) {
setLiteralValue(value.property, mapping[name]);
}
}
} else if (node.type === 'CallExpression' && isExportUse(node.callee)) {
// wasmExports["___wasm_call_ctors"](); -> wasmExports["M"]();
const callee = node.callee;
const name = callee.property.value;
if (mapping[name]) {
setLiteralValue(callee.property, mapping[name]);
}
} else if (isExportUse(node)) {
const prop = node.property;
const name = prop.value;
if (mapping[name]) {
setLiteralValue(prop, mapping[name]);
}
} else if (isImportFromWasm(node)) {
// WASM_ESM_INTEGRATION: rename the wasm-facing name of each received
// export, e.g. `import { malloc as _malloc }` -> `import { a as _malloc }`.
// Replace the imported slot (rather than mutate it in place) since for an
// unaliased specifier acorn shares one node for both sides.
node.specifiers.forEach((spec) => {
const newName = mapping[spec.imported.name];
if (newName) {
spec.imported = makeIdentifier(newName);
}
});
} else if (isExportSpecifierList(node)) {
// WASM_ESM_INTEGRATION: rename the wasm-facing name of each JS function
// sent to wasm, e.g. `export { _fd_write as fd_write }` ->
// `export { _fd_write as a }`. Re-exports of wasm exports (`export {
// _main }`) carry a JS-local name that is never in the mapping, so they
// are left untouched.
node.specifiers.forEach((spec) => {
const newName = mapping[spec.exported.name];
if (newName) {
spec.exported = makeIdentifier(newName);
}
});
}
});
}
// A static dyncall is dynCall('vii', ..), which is actually static even
// though we call dynCall() - we see the string signature statically.
function isStaticDynCall(node) {
return (
node.type === 'CallExpression' &&
node.callee.type === 'Identifier' &&
node.callee.name === 'dynCall' &&
isLiteralString(node.arguments[0])
);
}
function getStaticDynCallName(node) {
return 'dynCall_' + node.arguments[0].value;
}
// a dynamic dyncall is one in which all we know is *some* dynCall may
// be called, but not who. This can be either
// dynCall(*not a string*, ..)
// or, to be conservative,
// "dynCall_"
// as that prefix means we may be constructing a dynamic dyncall name
// (dynCall and embind's requireFunction do this internally).
function isDynamicDynCall(node) {
return (
(node.type === 'CallExpression' &&
node.callee.type === 'Identifier' &&
node.callee.name === 'dynCall' &&
!isLiteralString(node.arguments[0])) ||
(isLiteralString(node) && node.value === 'dynCall_')
);
}
//
// Emit the DCE graph, to help optimize the combined JS+wasm.
// This finds where JS depends on wasm, and where wasm depends
// on JS, and prints that out.
//
// The analysis here is simplified, and not completely general. It
// is enough to optimize the common case of JS library and runtime
// functions involved in loops with wasm, but not more complicated
// things like JS objects and sub-functions. Specifically we
// analyze as follows:
//
// * We consider (1) the toplevel scope, and (2) the scopes of toplevel defined
// functions (defun, not function; i.e., function X() {} where
// X can be called later, and not y = function Z() {} where Z is
// just a name for stack traces). We also consider the wasm, which
// we can see things going to and arriving from.
// * Anything used in a defun creates a link in the DCE graph, either
// to another defun, or the wasm.
// * Anything used in the toplevel scope is rooted, as it is code
// we assume will execute. The exceptions are
// * when we receive something from wasm; those are "free" and
// do not cause rooting. (They will become roots if they are
// exported, the metadce logic will handle that.)
// * when we send something to wasm; sending a defun causes a
// link in the DCE graph.
// * Anything not in the toplevel or not in a toplevel defun is
// considering rooted. We don't optimize those cases.
//
// Special handling:
//
// * dynCall('vii', ..) are dynamic dynCalls, but we analyze them
// statically, to preserve the dynCall_vii etc. method they depend on.
// Truly dynamic dynCalls (not to a string constant) will not work,
// and require the user to export them.
// * Truly dynamic dynCalls are assumed to reach any dynCall_*.
//
// XXX this modifies the input AST. if you want to keep using it,
// that should be fixed. Currently the main use case here does
// not require that. TODO FIXME
//
function emitDCEGraph(ast) {
// First pass: find the wasm imports and exports, and the toplevel
// defuns, and save them on the side, removing them from the AST,
// which makes the second pass simpler.
//
// The imports that wasm receives look like this:
//
// var wasmImports = { "abort": abort, "assert": assert, [..] };
//
// The exports are trickier, as they have a different form whether or not
// async compilation is enabled. It can be either:
//
// var _malloc = Module['_malloc'] = wasmExports['_malloc'];
//
// or
//
// var _malloc = wasmExports['_malloc'];
//
// or
//
// var _malloc = Module['_malloc'] = (x) => wasmExports['_malloc'](x);
//
// or, in the minimal runtime, it looks like
//
// function assignWasmExports(wasmExports)
// ..
// _malloc = wasmExports["malloc"];
// ..
// });
const imports = [];
const defuns = [];
const dynCallNames = [];
const nameToGraphName = {};
const modulePropertyToGraphName = {};
const exportNameToGraphName = {}; // identical to wasmExports['..'] nameToGraphName
let foundWasmImportsAssign = false;
let foundMinimalRuntimeExports = false;
// Under WASM_ESM_INTEGRATION, JS names bound to wasm exports via an ES import
// from the wasm module. Lets us tell a re-export of a wasm export apart from a
// JS function that is itself exported to wasm (both are `export {..}`).
const wasmExportLocals = new Set();
function saveAsmExport(name, asmName) {
// the asmName is what the wasm provides directly; the outside JS
// name may be slightly different (extra "_" in wasm backend)
const graphName = getGraphName(name, 'export');
nameToGraphName[name] = graphName;
modulePropertyToGraphName[name] = graphName;
exportNameToGraphName[asmName] = graphName;
if (/^dynCall_/.test(name)) {
dynCallNames.push(graphName);
}
}
// We track defined functions very carefully, so that we can remove them and
// the things they call, but other function scopes (like arrow functions and
// object methods) are trickier to track (object methods require knowing what
// object a function name is called on), so we do not track those. We consider
// all content inside them as top-level, which means it is used.
var specialScopes = 0;
fullWalk(
ast,
(node) => {
if (isWasmImportsAssign(node)) {
const assignedObject = getWasmImportsValue(node);
assignedObject.properties.forEach((item) => {
let value = item.value;
if (value.type === 'Literal' || value.type === 'FunctionExpression') {
return; // if it's a numeric or function literal, nothing to do here
}
if (value.type === 'LogicalExpression') {
// We may have something like wasmMemory || Module.wasmMemory in pthreads code;
// use the left hand identifier.
value = value.left;
}
assertAt(value.type === 'Identifier', value);
const nativeName = item.key.type == 'Literal' ? item.key.value : item.key.name;
assert(nativeName);
imports.push([value.name, nativeName]);
});
foundWasmImportsAssign = true;
emptyOut(node); // ignore this in the second pass; this does not root
} else if (isImportFromWasm(node)) {
// WASM_ESM_INTEGRATION: wasm exports received as
// import { malloc as _malloc, memory } from './a.out.wasm';
// Each binding is a wasm export, exactly like `var _x = wasmExports['x']`.
node.specifiers.forEach((spec) => {
const jsName = spec.local.name; // JS-side name
const asmName = spec.imported.name; // wasm-provided name
if (exportNameToGraphName.hasOwnProperty(asmName)) {
// Another local already binds this wasm export (e.g. both `memory`
// and `memory as wasmMemory`): point this local at the same node so
// a use of either roots the one underlying export.
nameToGraphName[jsName] = exportNameToGraphName[asmName];
} else {
saveAsmExport(jsName, asmName);
}
wasmExportLocals.add(jsName);
});
// This ES form stands in for the `wasmImports`/`wasmExports` idioms the
// non-ESM build emits, so it satisfies the sanity check below.
foundWasmImportsAssign = true;
// Drop from the second pass: the local bindings must not be seen as
// top-level uses (that would root every export and defeat DCE).
emptyOut(node);
} else if (isExportSpecifierList(node)) {
// Sourceless `export {..}` statements come in three forms:
// (a) JS functions sent to wasm: export { _fd_write as fd_write };
// (b) re-exports of wasm exports: export { _main };
// (c) runtime/library exports: export { HEAP32, baz };
// Only (a) are wasm import edges (recorded and removed here). (b) and
// (c) are ordinary top-level uses left in place to root in the second
// pass. (a) is the only form written with an alias (`x as y`), which
// acorn represents with distinct local/exported nodes; bare specifiers
// reuse a single node for both sides.
const importEdges = node.specifiers.filter(
(spec) =>
spec.local !== spec.exported && !wasmExportLocals.has(spec.local.name),
);
if (importEdges.length) {
// (a) `export { jsName as nativeName }` - jsName implements the import.
importEdges.forEach((spec) => imports.push([spec.local.name, spec.exported.name]));
foundWasmImportsAssign = true;
emptyOut(node); // does not root; second pass ignores it
}
} else if (node.type === 'AssignmentExpression') {
const target = node.left;
// Ignore assignment to the wasmExports object (as happens in
// applySignatureConversions).
if (isExportUse(target)) {
emptyOut(node);
}
} else if (node.type === 'VariableDeclaration') {
if (node.declarations.length === 1) {
const item = node.declarations[0];
const name = item.id.name;
const value = item.init;
if (value && isExportUse(value)) {
const asmName = getExportOrModuleUseName(value);
// this is:
// var _x = wasmExports['x'];
saveAsmExport(name, asmName);
emptyOut(node);
} else if (value && value.type === 'AssignmentExpression') {
const assigned = value.left;
if (isModuleUse(assigned) && getExportOrModuleUseName(assigned) === name) {
// this is
// var x = Module['x'] = ?
// which looks like a wasm export being received. confirm with the asm use
let found = 0;
let asmName;
fullWalk(value.right, (node) => {
if (isExportUse(node)) {
found++;
asmName = getExportOrModuleUseName(node);
}
});
// in the wasm backend, the asm name may have one fewer "_" prefixed
if (found === 1) {
// this is indeed an export
// the asmName is what the wasm provides directly; the outside JS
// name may be slightly different (extra "_" in wasm backend)
saveAsmExport(name, asmName);
emptyOut(node); // ignore this in the second pass; this does not root
return;
}
if (value.right.type === 'Literal') {
// this is
// var x = Module['x'] = 1234;
// this form occurs when global addresses are exported from the
// module. It doesn't constitute a usage.
assertAt(typeof value.right.value === 'number', value.right);
emptyOut(node);
}
}
}
}
// A variable declaration that has no initial values can be ignored in
// the second pass, these are just declarations, not roots - an actual
// use must be found in order to root.
if (!node.declarations.reduce((hasInit, decl) => hasInit || !!decl.init, false)) {
emptyOut(node);
}
} else if (node.type === 'FunctionDeclaration') {
const name = node.id.name;
// Check if this is the minimal runtime exports function, which looks like
// function assignWasmExports(wasmExports)
if (
name == 'assignWasmExports' &&
node.params.length === 1 &&
node.params[0].type === 'Identifier' &&
node.params[0].name === 'wasmExports'
) {
// This looks very much like what we are looking for.
const body = node.body.body;
assert(!foundMinimalRuntimeExports);
foundMinimalRuntimeExports = true;
for (let i = 0; i < body.length; i++) {
const item = body[i];
if (
item.type === 'ExpressionStatement' &&
item.expression.type === 'AssignmentExpression' &&
item.expression.operator === '=' &&
item.expression.left.type === 'Identifier' &&
item.expression.right.type === 'MemberExpression' &&
item.expression.right.object.type === 'Identifier' &&
item.expression.right.object.name === 'wasmExports' &&
item.expression.right.property.type === 'Literal'
) {
const name = item.expression.left.name;
const asmName = item.expression.right.property.value;
saveAsmExport(name, asmName);
emptyOut(item); // ignore all this in the second pass; this does not root
}
}
} else if (!specialScopes) {
defuns.push(node);
nameToGraphName[name] = getGraphName(name, 'defun');
emptyOut(node); // ignore this in the second pass; we scan defuns separately
}
} else if (node.type === 'ArrowFunctionExpression') {
assert(specialScopes > 0);
specialScopes--;
} else if (node.type === 'Property' && node.method) {
assert(specialScopes > 0);
specialScopes--;
}
},
(node) => {
// Pre-walking logic. We note special scopes (see above).
if (node.type === 'ArrowFunctionExpression' || (node.type === 'Property' && node.method)) {
specialScopes++;
}
},
);
// Scoping must balance out.
assert(specialScopes === 0);
// We must have found the info we need.
assert(
foundWasmImportsAssign,
'could not find the assignment to "wasmImports". perhaps --pre-js or --post-js code moved it out of the global scope? (things like that should be done after emcc runs, as they do not need to be run through the optimizer which is the special thing about --pre-js/--post-js code)',
);
// Read exports that were declared in extraInfo
if (extraInfo) {
for (const exp of extraInfo.exports) {
saveAsmExport(exp[0], exp[1]);
}
}
// Second pass: everything used in the toplevel scope is rooted;
// things used in defun scopes create links
function getGraphName(name, what) {
return 'emcc$' + what + '$' + name;
}
const infos = {}; // the graph name of the item => info for it
for (const [jsName, nativeName] of imports) {
const name = getGraphName(jsName, 'import');
const info = (infos[name] = {
name: name,
import: ['env', nativeName],
reaches: new Set(),
});
if (nameToGraphName.hasOwnProperty(jsName)) {
info.reaches.add(nameToGraphName[jsName]);
} // otherwise, it's a number, ignore
}
for (const [e, _] of Object.entries(exportNameToGraphName)) {
const name = exportNameToGraphName[e];
infos[name] = {
name: name,
export: e,
reaches: new Set(),
};
}
// a function that handles a node we visit, in either a defun or
// the toplevel scope (in which case the second param is not provided)
function visitNode(node, defunInfo) {
// TODO: scope awareness here. for now we just assume all uses are
// from the top scope, which might create more uses than needed
let reached;
if (node.type === 'Identifier') {
const name = node.name;
if (nameToGraphName.hasOwnProperty(name)) {
reached = nameToGraphName[name];
}
} else if (isModuleUse(node)) {
const name = getExportOrModuleUseName(node);
if (modulePropertyToGraphName.hasOwnProperty(name)) {
reached = modulePropertyToGraphName[name];
}
} else if (isStaticDynCall(node)) {
reached = getGraphName(getStaticDynCallName(node), 'export');
} else if (isDynamicDynCall(node)) {
// this can reach *all* dynCall_* targets, we can't narrow it down
reached = dynCallNames;
} else if (isExportUse(node)) {
// any remaining asm uses are always rooted in any case
const name = getExportOrModuleUseName(node);
if (exportNameToGraphName.hasOwnProperty(name)) {
infos[exportNameToGraphName[name]].root = true;
}
return;
}
if (reached) {
function addReach(reached) {
if (defunInfo) {
defunInfo.reaches.add(reached); // defun reaches it
} else {
if (infos[reached]) {
infos[reached].root = true; // in global scope, root it
} else {
// An info might not exist for the identifier if it is missing, for
// example, we might call Module.dynCall_vi in library code, but it
// won't exist in a standalone (non-JS) build anyhow. We can ignore
// it in that case as the JS won't be used, but warn to be safe.
trace('metadce: missing declaration for ' + reached);
}
}
}
if (typeof reached === 'string') {
addReach(reached);
} else {
reached.forEach(addReach);
}
}
}
defuns.forEach((defun) => {
const name = getGraphName(defun.id.name, 'defun');
const info = (infos[name] = {
name: name,
reaches: new Set(),
});
fullWalk(defun.body, (node) => visitNode(node, info));
});
fullWalk(ast, (node) => visitNode(node, null));
// Final work: print out the graph
// sort for determinism
const graph = Object.entries(infos)
.sort(([name1], [name2]) => (name1 > name2 ? 1 : -1))
.map(([_name, info]) => ({
...info,
reaches: Array.from(info.reaches).sort(),
}));
dump(graph);
}
// Apply graph removals from running wasm-metadce. This only removes imports and
// exports from JS side, effectively disentangling the wasm and JS sides that
// way (and we leave further DCE on the JS and wasm sides to their respective
// optimizers, closure compiler and binaryen).
function applyDCEGraphRemovals(ast) {
const unusedExports = new Set(extraInfo.unusedExports);
const unusedImports = new Set(extraInfo.unusedImports);
const foundUnusedImports = new Set();
const foundUnusedExports = new Set();
trace('unusedExports:', unusedExports);
trace('unusedImports:', unusedImports);
fullWalk(ast, (node) => {
if (isWasmImportsAssign(node)) {
const assignedObject = getWasmImportsValue(node);
assignedObject.properties = assignedObject.properties.filter((item) => {
const name = item.key.name;
const value = item.value;
if (unusedImports.has(name)) {
foundUnusedImports.add(name);
return hasSideEffects(value);
}
return true;
});
} else if (isImportFromWasm(node)) {
// WASM_ESM_INTEGRATION: drop unused wasm exports from
// import { malloc as _malloc, .. } from './a.out.wasm';
node.specifiers = node.specifiers.filter((spec) => {
if (unusedExports.has(spec.imported.name)) {
foundUnusedExports.add(spec.imported.name);
return false;
}
return true;
});
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