Bug 22844 demonstrates that it is not sufficient to play tricks with
the clip regions to work around the bogus images from the X
server. The problem there is that if the operation hits the general
path and the destination has a different format than a8r8g8b8, the
destination pixels will be fetched into a temporary array. But because
those pixels would be outside the clip region, they would be fetched
as black. The previous workaround was relying on fast paths fetching
those pixels without checking the clip region.
In the new scheme we work around the problem at the
pixman_image_composite() level. If an image is determined to need a
work around, we translate both the bits pointer, the coordinates, and
the clip region, thus effectively undoing the X server's broken
computation.
The pld instruction used in the NEON assembler code is only available
for ARMv5e and >= ARMv6.
Set -mcpu=cortex-a8 when compiling the source file (similar to what is
already done for the SIMD build).
128-bit registers "qX" are incorrectly handled in inline assembly
clobber list for codesourcery cs2007q3 gcc toolchain. Only the
first 64-bit half is saved and restored by gcc. Changing clobber
list to use only 64-bit register aliases can solve this problem.
For example, 128-bit register q0 is mapped to two 64-bit
registers d0 and d1, q1 is mapped to d2 and d3, etc.
This patch effectively reverts the changes done by commit
8eeeca9932 which was causing
severe stability issues, and restores old variant of
'neon_composite_over_n_8_0565' function, which used to work
correctly.
- Introduce a GOOD_RECT() macro that checks that a pixman_box_t is not
empty or degenerate an use it.
- Use GOOD_RECT() instead of magic if statements for funtions that take
x, y, width, height arguments
- Use GOOD_RECT() in _reset(). The checks in the previous code seemed to
allow an empty box, but then created a broken region from it.
- Add GOOD(region) check at the end of _translate()
When compiled without optimization, GCC will place various temporaries
on the stack. Since Firefox sometimes causes the stack to be aligned
to four bytes, this causes movdqa to generate faults.
