1546407 - Wasm baseline compiler: fix inconsistent indexing in MachineStackTracker::{set,is}GCPointer

Status: RESOLVED FIXED

(Core :: JavaScript: WebAssembly, defect)

Description

[Julian Seward [:jseward]]

MachineStackTracker::setGCPointer claims in a comment that its argument
|offsetFromSP| is an index up from the lowest address denoted by the stack
map. It implements that consistently with the comment.

MachineStackTracker::isGCPointer makes the same claim in a comment, but
actually implements the indexing in the opposite direction.

Comment 1

[Julian Seward [:jseward]]

Attachment: Bug 1546407 - Wasm baseline compiler: fix inconsistent indexing in MachineStackTracker::{set,is}GCPointer.

MachineStackTracker::setGCPointer claims in a comment that its argument
|offsetFromSP| is an index up from the lowest address denoted by the stack
map. It implements that consistently with the comment.

MachineStackTracker::isGCPointer makes the same claim in a comment, but
actually implements the indexing in the opposite direction.

This patch:

• inverts the indexing direction of ::isGCPointer, making it consistent with
  the comments and with ::setGCPointer

• changes the one-and-only use point of ::isGCPointer, in createStackMap(),
  accordingly. Rather than change the argument to ::isGCPointer, the
  iteration direction of the containing loop is inverted, since that fits
  better with the surrounding code.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/cfafd091d301
Wasm baseline compiler: fix inconsistent indexing in MachineStackTracker::{set,is}GCPointer.  r=lhansen.

Comment 3

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/cfafd091d301