839217 - ion: |a && false| is incompletely optimized

Status: RESOLVED DUPLICATE of bug 669796

(Core :: JavaScript Engine, defect)

Description

[Niko Matsakis [:nmatsakis]]

There is now a pass to strip dead or unreachable blocks, but it fails with code like:

    if (foo() && false) { ... }

This is because the |foo() && false| is first stored into a variable, and at the time the pass runs the constants have not been fully propagated.  This situation arises in self-hosted code for ParallelArray, where inlined functions are often evaluated to true or false to select different control flow in sequential or parallel mode.

Probably the best fix would be to integrate the stripping of unreachable blocks with GVN as proposed in Bug 669796.

Comment 1

[Niko Matsakis [:nmatsakis]]

actually I decided to just call this a dup of bug 669796 and add my comments there.