lwsync() is a full read/write-barrier. That's all we need, never
need sync(). I'm not sure why an isync() was used in fetch_and_add,
but since that's a read-modify-write, I just changed it to have
lwsync() on both sides.
Originally, glib's atomic_get was implemented as "memory_barrier; load".
I copied this into cairo, fontconfig, and harfbuzz. However, that's
wrong. Correct way is "load; memory_barrier". The details are long
and hard to fully grasp. Best to read:
https://www.kernel.org/doc/Documentation/memory-barriers.txt
Also see my report against GNOME:
https://gitlab.gnome.org/GNOME/glib/issues/1449
Note that this is irrelevant if C++11-like atomic ops are available.
This reverts commit b1e5650c67.
After lots of head-scratching and finally finding the only truly
readable source to be the good old:
https://www.kernel.org/doc/Documentation/memory-barriers.txt
I've convinced myself that we need consume memory-ordering on get().
The location of memory-barrier in a load should be after, not before
the load. That needs fixing. I'll do that separately.
Oriya went down from 9 to 2.
BENGALI: 353725 out of 354188 tests passed. 463 failed (0.130722%)
DEVANAGARI: 707311 out of 707394 tests passed. 83 failed (0.0117332%)
GUJARATI: 366355 out of 366457 tests passed. 102 failed (0.0278341%)
GURMUKHI: 60729 out of 60747 tests passed. 18 failed (0.0296311%)
KANNADA: 951300 out of 951913 tests passed. 613 failed (0.0643966%)
MALAYALAM: 1048136 out of 1048334 tests passed. 198 failed (0.0188871%)
MYANMAR: 1115830 out of 1123883 tests passed. 8053 failed (0.716534%)
ORIYA: 42327 out of 42329 tests passed. 2 failed (0.00472489%)
SINHALA: 271596 out of 271847 tests passed. 251 failed (0.0923313%)
TAMIL: 1091754 out of 1091754 tests passed. 0 failed (0%)
TELUGU: 970555 out of 970573 tests passed. 18 failed (0.00185457%)
Note that there's minor positioning differences, and ONE reordering
difference between what we get for these and what Uniscribe gets.
Probably same as what's described in commit message for
1a96cc825d
This makes test suite happy again (at 44) while fixing the sequences
we were fixing, which were the following with KhmerUI.ttf:
U+1789,U+17BC
U+1789,U+17D2,U+1789
U+1789,U+17D2,U+1789,U+17BC
Fixes rest of https://github.com/harfbuzz/harfbuzz/issues/974
Behdad Esfahbod
Ebrahim Byagowi
Garret Rieger