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[babel-plugin-transform-es2015-parameters] more oportunities for optimisations

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This commit is contained in:
Fabio M. Costa
2015-12-06 18:31:23 -08:00
parent 16ae7c2d9a
commit 3868d36e31
5 changed files with 57 additions and 14 deletions
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27
packages/babel-plugin-transform-es2015-parameters/src/rest.js
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@@ -52,19 +52,34 @@ let memberExpressionOptimisationVisitor = {
if (state.noOptimise) {
state.deopted = true;
} else {
if (path.parentPath.isMemberExpression({ computed: true, object: node })) {
// if we know that this member expression is referencing a number then we can safely
// optimise it
let prop = path.parentPath.get("property");
let {parentPath} = path;
// ex: args[0]
if (parentPath.isMemberExpression({ computed: true, object: node })) {
// if we know that this member expression is referencing a number then
// we can safely optimise it
let prop = parentPath.get("property");
if (prop.isBaseType("number")) {
state.candidates.push(path);
return;
}
}
// ex: args.length
if (parentPath.isMemberExpression({ computed: false, object: node })) {
let prop = parentPath.get("property");
if (prop.node.name === "length") {
state.candidates.push(path);
return;
}
}
// we can only do these optimizations if the rest variable would match
// the arguments exactly
// optimise single spread args in calls
if (path.parentPath.isSpreadElement() && state.offset === 0) {
let call = path.parentPath.parentPath;
// ex: fn(...args)
if (state.offset === 0 && parentPath.isSpreadElement()) {
let call = parentPath.parentPath;
if (call.isCallExpression() && call.node.arguments.length === 1) {
state.candidates.push(path);
return;