810604 - vertical white lines in downscaled images when building with --enable-optimize=-O3

Status: NEW

(Core :: Graphics: ImageLib, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

So ever since bug 486918 landed (but not during the period when it was backed out) I've been seeing vertical white lines in a lot of downscaled images; for images that load incrementally they don't show up until the image is done loading.

However, I only see these lines in builds I build myself, but I don't see them in official Firefox nightlies.  However, I've just verified that the determining factor there is the toolchain or mozconfig rather than my local patches; I still see the white lines with a clean tree.

I haven't yet figured out which parts of my build configuration are the problem, though, but I wanted to get a bug on file in case anyone else is seeing the same thing.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: screenshot

This is one of the worse examples.

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: my about:buildconfig

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

The crucial bit turns out to be:
  --enable-optimize="-O3 -march=corei7 -mtune=corei7"

If I switch to just --enable-optimize (which, on Linux, means -Os) by taking the is_windows path in https://hg.mozilla.org/users/dbaron_mozilla.com/mozconfigs/raw-file/f173758c559e/common-opt , then the problem goes away.

Comment 4

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Interestingly:
  --enable-optimize="-Os -march=corei7 -mtune=corei7"
works fine.  (And I was getting ready to start poking around in gfx/skia/src/opts/.)

Comment 5

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

And with just:
  --enable-optimize="-O3"
I still see the bug.

Comment 6

[drunkenbatman]

I'm seeing this with march=core-avx-i but on OS, O2 and O3 on gentoo using the last several firefox versions up to the current: GCC 4.8.2, firefox 27.0.1, mesa 9.2.5-r1, xf86-video-intel 2.99.910.

Comment 7

[drunkenbatman]

Seeing the same with GCC 4.9 + FF v29, lines go away if I revert to bog-standard CFLAGS on Gentoo with no "custom-optimization custom-cflags", but it's there with OS/O2/etc, so march=native? It's obviously slower with my larger tabsets...