There are versions for all combinations of x8r8g8b8/a8r8g8b8 and
pad/repeat/none/normal repeat modes. The bulk of each function is an
inline function that takes a format and a repeat mode as parameters.
Radial gradients are "conical", thus they can have some non-opaque
parts even if all of their stops are completely opaque.
To guarantee that a radial gradient is actually opaque, it needs to
also have one of the two circles containing the other one. In this
case when extrapolating, the whole plane is completely covered (as
explained in the comment in pixman-radial-gradient.c).
The performance improvement is only in the ballpark of 5% when
compared against C code built with a reasonably good compiler
(gcc 4.5.1). But gcc 4.4 produces approximately 30% slower code
here, so assembly optimization makes sense to avoid dependency
on the compiler quality and/or optimization options.
Benchmark from ARM11:
== before ==
op=1, src_fmt=10020565, dst_fmt=10020565, speed=34.86 MPix/s
== after ==
op=1, src_fmt=10020565, dst_fmt=10020565, speed=36.62 MPix/s
Benchmark from ARM Cortex-A8:
== before ==
op=1, src_fmt=10020565, dst_fmt=10020565, speed=89.55 MPix/s
== after ==
op=1, src_fmt=10020565, dst_fmt=10020565, speed=94.91 MPix/s
This template can be used to instantiate scaled fast path functions
by providing main loop code and calling NEON assembly optimized
scanline processing functions from it. Another macro can be used
to simplify adding entries to fast path tables.
Now it is possible to generate scanline processing functions
for the case when the source image is scaled with NEAREST filter.
Only 16bpp and 32bpp pixel formats are supported for now. But the
others can be also added later when needed. All the existing NEON
fast path functions should be quite easy to reuse for implementing
fast paths which can work with scaled source images.
Added a special macro 'pixld_src' which is now responsible for fetching
pixels from the source image. Right now it just passes all its arguments
directly to 'pixld' macro, but it can be used in the future to provide
a special pixel fetcher for implementing nearest scaling.
The 'pixld_src' has a lot of arguments which define its behavior. But
for each particular fast path implementation, we already know NEON
registers allocation and how many pixels are processed in a single block.
That's why a higher level macro 'fetch_src_pixblock' is also introduced
(it's easier to use because it has no arguments) and used everywhere
in 'pixman-arm-neon-asm.S' instead of VLD instructions.
This patch does not introduce any functional changes and the resulting code
in the compiled object file is exactly the same.
This was mostly harmless and had no effect on little endian systems.
But wrong vector element size is at least inconsistent and also
can theoretically cause problems on big endian ARM systems.
There is attribute 'constructor' supported since gcc 2.7 which allows
to have a constructor function for library initialization. This eliminates
an extra branch for each composite operation and also helps to avoid
complains from race condition detection tools like helgrind.
The other compilers may or may not support this attribute properly.
Ideally, the compilers should fail to compile the code with unknown
attribute, so the configure check should do the right job. But in
reality the problems are surely possible. Fortunately such problems
should be quite easy to find because NULL pointer dereference should
happen almost immediately if the constructor fails to run.
clang 2.7:
supports __attribute__((constructor)) properly and pretends to be gcc
tcc 0.9.25:
ignores __attribute__((constructor)), but does not pretend to be gcc
GCC assumes that input variables in inline assembly are fully consumed
before any output variable is written. This means it may allocate the
variables in the same register unless the output variables are marked
as early-clobber.
From Jeremy Huddleston:
I noticed a problem building pixman with clang and reported it to
the clang developers. They responded back with a comment about
the inline asm in pixman-mmx.c and suggested a fix:
"""
Incidentally, Jeremy, in the asm that reads
__asm__ (
"movq %7, %0\n"
"movq %7, %1\n"
"movq %7, %2\n"
"movq %7, %3\n"
"movq %7, %4\n"
"movq %7, %5\n"
"movq %7, %6\n"
: "=y" (v1), "=y" (v2), "=y" (v3),
"=y" (v4), "=y" (v5), "=y" (v6), "=y" (v7)
: "y" (vfill));
all the output operands except the last one should be marked as
earlyclobber ("=&y"). This is working by accident with gcc.
"""
Cc: jeremyhu@apple.com
Reviewed-by: Matt Turner <mattst88@gmail.com>
There used to be a bug in the X server where it would rely on
out-of-bounds accesses when it was asked to composite with a
window as the source. It would create a pixman image pointing
to some bogus position in memory, but then set a clip region
to the position where the actual bits were.
Due to a bug in old versions of pixman, where it would not clip
against the image bounds when a clip region was set, this would
actually work. So when the pixman bug was fixed, a workaround was
added to allow certain out-of-bound accesses.
However, the 1.6 X server is so old now that we can remove this
workaround. This does mean that if you update pixman to 0.22 or later,
you will need to use a 1.7 X server or later.
As of pixman-0.19.2-5-g5b99710, Gtk+ is auto-detected, make sure not to
pick it accidentally, by passing --disable-gtk. (That's only for test
purposes, but would require pixman-1 itself.)
Even after commit e46be417ce alphamap
test is still leaking the alphamap pixmap, leading to mmap() failures
on cygwin
Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
huge-radial in the cairo test suite pointed out an undocumented
overflow in the radial gradient code.
By casting to pixman_fixed_48_16_t before doing the operations,
the overflow can be avoided.
The linear gradient was the only image type that relied on the class
being stored in the image struct itself. With the previous changes, it
doesn't need that anymore, so we can delete the field.
Use the same computations to classify the gradient and to
rasterize it.
This improves the correctness of the classification by
avoiding integer division.
