1741411 - Optimised spread calls emit duplicate lookups

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect, P1)

Description

[André Bargull [:anba]]

This test case currently fails:

var count = 0;
var scope = {
  get args() {
    count++;
    return "";
  }
};

with (scope) {
  [].push(...args);
}

// Ensure |args| is only looked up once.
assertEq(count, 1);

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1741411 - Part 1: Only emit argument operand once for optimised spread calls. r=iain!

This commit changes the byte code for optimised spread calls to emit the spread
operand only once.

The new BytecodeEmitter::emitSpreadIntoArray() method was added to spread an
on-stack value into an array. This method is needed to avoid emitting the spread
operand another time in 'BytecodeEmitter::emitArray()`.

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1741411 - Part 2: Emit JSOp::OptimizeSpreadCall for all calls with a single spread argument. r=iain!

After part 1 we can lift the single name operand restriction and emit
JSOp::OptimizeSpreadCall for all calls with a single spread argument.

Depends on D131242

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f87b1d574cbc
Part 1: Only emit argument operand once for optimised spread calls. r=iain
https://hg.mozilla.org/integration/autoland/rev/7f550858162e
Part 2: Emit JSOp::OptimizeSpreadCall for all calls with a single spread argument. r=iain

Comment 4

[Marian-Vasile Laza]

Backed out 6 changesets (Bug 1741411, Bug 1740737) for causing build bustages on CacheIR.cpp.
Backout link
Push with failures
Failure Log

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a05795a5d581
Part 1: Only emit argument operand once for optimised spread calls. r=iain
https://hg.mozilla.org/integration/autoland/rev/d58b06af1ac7
Part 2: Emit JSOp::OptimizeSpreadCall for all calls with a single spread argument. r=iain

Comment 6

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/a05795a5d581
https://hg.mozilla.org/mozilla-central/rev/d58b06af1ac7