At the moment iter buffers are only guaranteed to be aligned to a 4
byte boundary. SIMD implementations benefit from the buffers being
aligned to 16 bytes, so ensure this is the case.
V2:
- Use uintptr_t instead of unsigned long
- allocate 3 * SCANLINE_BUFFER_LENGTH byte on stack rather than just
SCANLINE_BUFFER_LENGTH
- use sizeof (stack_scanline_buffer) instead of SCANLINE_BUFFER_LENGTH
to determine overflow
The loops are already unrolled, so it was just a matter of packing
4 pixels into a single XMM register and doing aligned 128-bit
writes to memory via MOVDQA instructions for the SRC compositing
operator fast path. For the other fast paths, this XMM register
is also directly routed to further processing instead of doing
extra reshuffling. This replaces "8 PACKSSDW/PACKUSWB + 4 MOVD"
instructions with "3 PACKSSDW/PACKUSWB + 1 MOVDQA" per 4 pixels,
which results in a clear performance improvement.
There are also some other (less important) tweaks:
1. Convert 'pixman_fixed_t' to 'intptr_t' before using it as an
index for addressing memory. The problem is that 'pixman_fixed_t'
is a 32-bit data type and it has to be extended to 64-bit
offsets, which needs extra instructions on 64-bit systems.
2. Allow to recalculate the horizontal interpolation weights only
once per 4 pixels by treating the XMM register as four pairs
of 16-bit values. Each of these 16-bit/16-bit pairs can be
replicated to fill the whole 128-bit register by using PSHUFD
instructions. So we get "3 PADDW/PSRLW + 4 PSHUFD" instructions
per 4 pixels instead of "12 PADDW/PSRLW" per 4 pixels
(or "3 PADDW/PSRLW" per each pixel).
Now a good question is whether replacing "9 PADDW/PSRLW" with
"4 PSHUFD" is a favourable exchange. As it turns out, PSHUFD
instructions are very fast on new Intel processors (including
Atoms), but are rather slow on the first generation of Core2
(Merom) and on the other processors from that time or older.
A good instructions latency/throughput table, covering all the
relevant processors, can be found at:
http://www.agner.org/optimize/instruction_tables.pdf
Enabling this optimization is controlled by the PSHUFD_IS_FAST
define in "pixman-sse2.c".
3. One use of PSHUFD instruction (_mm_shuffle_epi32 intrinsic) in
the older code has been also replaced by PUNPCKLQDQ equivalent
(_mm_unpacklo_epi64 intrinsic) in PSHUFD_IS_FAST=0 configuration.
The PUNPCKLQDQ instruction is usually faster on older processors,
but has some side effects (instead of fully overwriting the
destination register like PSHUFD does, it retains half of the
original value, which may inhibit some compiler optimizations).
Benchmarks with "lowlevel-blt-bench -b src_8888_8888" using GCC 4.8.1 on
x86-64 system and default optimizations. The results are in MPix/s:
====== Intel Core2 T7300 (2GHz) ======
old: src_8888_8888 = L1: 128.69 L2: 125.07 M:124.86
over_8888_8888 = L1: 83.19 L2: 81.73 M: 80.63
over_8888_n_8888 = L1: 79.56 L2: 78.61 M: 77.85
over_8888_8_8888 = L1: 77.15 L2: 75.79 M: 74.63
new (PSHUFD_IS_FAST=0): src_8888_8888 = L1: 168.67 L2: 163.26 M:162.44
over_8888_8888 = L1: 102.91 L2: 100.43 M: 99.01
over_8888_n_8888 = L1: 97.40 L2: 95.64 M: 94.24
over_8888_8_8888 = L1: 98.04 L2: 95.83 M: 94.33
new (PSHUFD_IS_FAST=1): src_8888_8888 = L1: 154.67 L2: 149.16 M:148.48
over_8888_8888 = L1: 95.97 L2: 93.90 M: 91.85
over_8888_n_8888 = L1: 93.18 L2: 91.47 M: 90.15
over_8888_8_8888 = L1: 95.33 L2: 93.32 M: 91.42
====== Intel Core i7 860 (2.8GHz) ======
old: src_8888_8888 = L1: 323.48 L2: 318.86 M:314.81
over_8888_8888 = L1: 187.38 L2: 186.74 M:182.46
new (PSHUFD_IS_FAST=0): src_8888_8888 = L1: 373.06 L2: 370.94 M:368.32
over_8888_8888 = L1: 217.28 L2: 215.57 M:211.32
new (PSHUFD_IS_FAST=1): src_8888_8888 = L1: 401.98 L2: 397.65 M:395.61
over_8888_8888 = L1: 218.89 L2: 217.56 M:213.48
The most interesting benchmark is "src_8888_8888" (because this code can
be reused for a generic non-separable SSE2 bilinear fetch iterator).
The results shows that PSHUFD instructions are bad for Intel Core2 T7300
(Merom core) and good for Intel Core i7 860 (Nehalem core). Both of these
processors support SSSE3 instructions though, so they are not the primary
targets for SSE2 code. But without having any other more relevant hardware
to test, PSHUFD_IS_FAST=0 seems to be a reasonable default for SSE2 code
and old processors (until the runtime CPU features detection becomes
clever enough to recognize different microarchitectures).
(Rebased on top of patch that removes support for 8-bit bilinear
filtering -ssp)
The calloc call from pixman_image_create_bits may still
rely on http://en.wikipedia.org/wiki/Copy-on-write
Explicitly initializing the destination image results in
a more predictable behaviour.
V2:
- allocate 16 bytes aligned buffer with aligned stride instead
of delegating this to pixman_image_create_bits
- use memset for the allocated buffer instead of pixman solid fill
- repeat tests 3 times and select best results in order to filter
out even more measurement noise
The default has been 7-bit for a while now, and the quality
improvement with 8-bit precision is not enough to justify keeping the
code around as a compile-time option.
Scanline fetchers haven't been used for images other than bits for a
long time, so by making the type reflect this fact, a bit of casting
can be saved in various places.
Later versions of gcc-4.7.x are capable of generating iwMMXt
instructions properly, but gcc-4.8 contains better support and other
fixes, including iwMMXt in conjunction with hardfp. The existing 4.5
requirement was based on attempts to have OLPC use a patched gcc to
build pixman. Let's just require gcc-4.8.
This new iterator works in a separable way; that is, for a destination
scaline, it scales the two involved source scanlines and then caches
them so that they can be reused for the next destination scanlines.
There are two versions of the code, one that uses 64 bit arithmetic,
and one that uses 32 bit arithmetic only. The latter version is
used on 32 bit systems, where it is expected to be faster.
This scheme saves a substantial amount of arithmetic for larger
scalings; the per-pixel times for various configurations as reported
by scaling-bench are graphed here:
http://people.freedesktop.org/~sandmann/separable.v2/v2.png
The "sse2" graph is current default on x86, "mmx" is with sse2
disabled, "old c" is with sse2 and mmx disabled. The "new 32" and "new
64" graphs show times for the new code. As the graphs show, the 64 bit
version of the new code beats the "old c" for all scaling ratios.
The data was taken on a Sandy Bridge Core i3-2350M CPU @ 2.0 GHz
running in 64 bit mode.
The data used to generate the graph is available in this directory:
http://people.freedesktop.org/~sandmann/separable.v2/
There is also a Gnumeric spreadsheet v2.gnumeric containing the
per-pixel values and the graph.
V2:
- Add error message in the OOM/bad matrix case
- Save some shifts by storing the cached scanlines in AGBR order
- Special cased version that uses 32 bit arithmetic when sizeof(long) <= 4
This new benchmark scales a 320 x 240 test a8r8g8b8 image by all
ratios from 0.1, 0.2, ... up to 10.0 and reports the time it to took
to do each of the scaling operations, and the time spent per
destination pixel.
The times reported for the scaling operations are given in
milliseconds, the times-per-pixel are in nanoseconds.
V2: Format output better
The MSVC compiler is very strict about variable declarations after
statements.
Move all the declarations of each block before any statement in the
same block to fix multiple instances of:
alpha-loop.c(XX) : error C2275: 'pixman_image_t' : illegal use of this
type as an expression
I'm got bug in my system:
lcc: "scale.c", line 374: warning: function "gtk_scale_add_mark" declared
implicitly [-Wimplicit-function-declaration]
gtk_scale_add_mark (GTK_SCALE (widget), 0.0, GTK_POS_LEFT, NULL);
^
CCLD scale
scale.o: In function `app_new':
(.text+0x23e4): undefined reference to `gtk_scale_add_mark'
scale.o: In function `app_new':
(.text+0x250c): undefined reference to `gtk_scale_add_mark'
scale.o: In function `app_new':
(.text+0x2634): undefined reference to `gtk_scale_add_mark'
make[2]: *** [scale] Error 1
make[2]: Target `all' not remade because of errors.
$ pkg-config --modversion gtk+-2.0
2.12.1
The demos/scale.c use call to gtk_scale_add_mark() function from 2.16+
version of GTK+. Need do support old GTK+ (rewrite scale.c) or simple
demand of high version of GTK+, like this:
The Loongson code is compiled with -march=loongson2f to enable the MMI
instructions, but binutils refuses to link object code compiled with
different -march settings, leading to link failures later in the
compile. This avoids that problem by checking if we can link code
compiled for Loongson.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
The MSVC compiler is very strict about variable declarations after
statements.
Move all the declarations of each block before any statement in the
same block to fix multiple instances of:
alpha-loop.c(XX) : error C2275: 'pixman_image_t' : illegal use of this
type as an expression
I'm got bug in my system:
lcc: "scale.c", line 374: warning: function "gtk_scale_add_mark" declared
implicitly [-Wimplicit-function-declaration]
gtk_scale_add_mark (GTK_SCALE (widget), 0.0, GTK_POS_LEFT, NULL);
^
CCLD scale
scale.o: In function `app_new':
(.text+0x23e4): undefined reference to `gtk_scale_add_mark'
scale.o: In function `app_new':
(.text+0x250c): undefined reference to `gtk_scale_add_mark'
scale.o: In function `app_new':
(.text+0x2634): undefined reference to `gtk_scale_add_mark'
make[2]: *** [scale] Error 1
make[2]: Target `all' not remade because of errors.
$ pkg-config --modversion gtk+-2.0
2.12.1
The demos/scale.c use call to gtk_scale_add_mark() function from 2.16+
version of GTK+. Need do support old GTK+ (rewrite scale.c) or simple
demand of high version of GTK+, like this:
The SSE2, MMX, and fast implementations all have a copy of the
function iter_init_bits_stride that computes an image buffer and
stride.
Move that function to pixman-utils.c and share it among all the
implementations.
Now that we are using the new _pixman_implementation_iter_init(), the
old _src/_dest_iter_init() functions are no longer needed, so they can
be deleted, and the corresponding fields in pixman_implementation_t
can be removed.
A new field, 'iter_info', is added to the implementation struct, and
all the implementations store a pointer to their iterator tables in
it. A new function, _pixman_implementation_iter_init(), is then added
that searches those tables, and the new function is called in
pixman-general.c and pixman-image.c instead of the old
_pixman_implementation_src_init() and _pixman_implementation_dest_init().
In preparation for sharing all iterator initialization code from all
the implementations, move the general implementation to use a table of
pixman_iter_info_t.
The existing src_iter_init and dest_iter_init functions are
consolidated into one general_iter_init() function that checks the
iter_flags for whether it is dealing with a source or destination
iterator.
Unlike in the other implementations, the general_iter_init() function
stores its own get_scanline() and write_back() functions in the
iterator, so it relies on the initializer being called after
get_scanline and write_back being copied from the struct to the
iterator.
Similar to the SSE2 and MMX patches, this commit replaces a table of
fetcher_info_t with a table of pixman_iter_info_t, and similar to the
noop patch, both fast_src_iter_init() and fast_dest_iter_init() are
now doing exactly the same thing, so their code can be shared in a new
function called fast_iter_init_common().
Similar to the changes to noop, put all the iterators into a table of
pixman_iter_info_t and then do a generic search of that table during
iterator initialization.
Instead of having a nest of if statements, store the information about
iterators in a table of a new struct type, pixman_iter_info_t, and
then walk that table when initializing iterators.
The new struct contains a format, a set of image flags, and a set of
iter flags, plus a pixman_iter_get_scanline_t, a
pixman_iter_write_back_t, and a new function type
pixman_iter_initializer_t.
If the iterator matches an entry, it is first initialized with the
given get_scanline and write_back functions, and then the provided
iter_initializer (if present) is run. Running the iter_initializer
after setting get_scanline and write_back allows the initializer to
override those fields if it wishes.
The table contains both source and destination iterators,
distinguished based on the recently-added ITER_SRC and ITER_DEST;
similarly, wide iterators are recognized with the ITER_WIDE
flag. Having both source and destination iterators in the table means
the noop_src_iter_init() and noop_dest_iter_init() functions become
identical, so this patch factors out their code in a new function
noop_iter_init_common() that both calls.
The following patches in this series will change all the
implementations to use an iterator table, and then move the table
search code to pixman-implementation.c.
