The type of expression '1<<31' is signed int and this causes cppcheck to
issue the following warning.
src/gf_w32.c:681]: (error) Signed integer overflow for expression
'1<<31'.
Signed-off-by: Brad Hubbard <bhubbard@redhat.com>
Gf32 mul silence warning
silence warning like
```
/slow/kchai/ceph/src/erasure-code/jerasure/gf-complete/src/gf_w32.c: In function ‘gf_w32_cfmgk_multiply_region_from_single’:
/slow/kchai/ceph/src/erasure-code/jerasure/gf-complete/src/gf_w32.c:410:5: warning: ‘a’ may be used uninitialized in this function [-Wmaybe-uninitialized]
g = _mm_insert_epi64 (a, g_star, 0);
^
```
See merge request !19
in gf_w32_cfmgk_multiply_region_from_single(), follow warning is
reported by gcc:
gf-complete/src/gf_w32.c:410:5: warning: ‘a’ may be used uninitialized
in this function [-Wmaybe-uninitialized]
g = _mm_insert_epi64 (a, g_star, 0);
^
actually, we are using `a` as a dummy parameter for initializing `g` and
`q`. and only the lower lower 64 bits of them are used when doing
calculation. but their lower 64 bits are always initialized using
_mm_insert_epi64(). so this is a false alarm.
but we can silence this warning by moving the statement initializing `a`
up before passing it to _mm_insert_epi64(). this change does not hurt
the performance.
Signed-off-by: Kefu Chai <kchai@redhat.com>
Support for runtime detection of SIMD
This merge request adds support for runtime SIMD detection. The idea is that you would build gf-complete with full SIMD support, and gf_init will select the appropriate function at runtime based on the capabilities of the target machine. This would eliminate the need to build different versions of the code for different processors (you still need to build for different archs). Ceph for example has 3-4 flavors of jerasure on Intel (and does not support PCLMUL optimizations as a result of using to many binaries). Numerous libraries have followed as similar approach include zlib.
When reviewing this merge request I recommend that you look at each of the 5 commits independently. The first 3 commits don't change the existing logic. Instead they add debugging functions and test scripts that facilitate testing of the 4th and commit. The 4th commit is where all the new logic goes along with tests. The 5th commit fixes build scripts.
I've tested this on x86_64, arm, and aarch64 using QEMU. Numerous tests have been added that help this code and could help with future testing of gf-complete. Also I've compared the functions selected with the old code (prior to runtime SIMD support) with the new code and all functions are identical. Here's a gist with the test results prior to SIMD extensions: https://gist.github.com/bassamtabbara/d9a6dcf0a749b7ab01bc2953a359edec.
See merge request !18
ax_ext.m4 no longer performs any CPU checks. Instead it just checks
if the the compile supports SIMD flags.
Runtime detection will choose the right methods base on CPU
instructions available.
Intel AVX support is still done through the build since it would
require a major refactoring of the code base to support it at runtime.
For now I added a configuration flag --enable-avx that can be used
to compile with AVX support.
Also use cpu intrinsics instead of __asm__
This commits adds support for runtime detection of SIMD instructions. The idea is that you would build once with all supported SIMD functions and the same binaries could run on different machines with varying support for SIMD. At runtime gf-complete will select the right functions based on the processor.
gf_cpu.c has the logic to detect SIMD instructions. On Intel processors this is done through cpuid. For ARM on linux we use getauxv.
The logic in gf_w*.c has been changed to check for runtime SIMD support and fallback to generic code.
Also a new test has been added. It compares the functions selected by gf_init when we enable/disable SIMD support through build flags, with runtime enabling/disabling. The test checks if the results are identical.
This commit adds a couple of scripts that help test SIMD functionality
on different machines through QEMU.
tools/test_simd_qemu.sh will automatically start qemu, run tests
and stop it. it uses the Ubuntu cloud images which are built for
x86_64, arm and arm64.
tools/test_simd.sh run a number of tests including compiling
with different flags, unit tests, and gathering the functions
selected in gf_init (and when compiling with DEBUG_FUNCTIONS)
There is currently no way to figure out which functions were selected
during gf_init and as a result of SIMD options. This is not even possible
in gdb since most functions are static.
This commit adds a new macro SET_FUNCTION that records the name of the
function selected during init inside the gf_internal structure. This macro
only works when DEBUG_FUNCTIONS is defined during compile. Otherwise the
code works exactly as it did before this change.
The names of selected functions will be used during testing of SIMD
runtime detection.
All calls such as:
gf->multiply.w32 = gf_w16_shift_multiply;
need to be replaced with the following:
SET_FUNCTION(gf,multiply,w32,gf_w16_shift_multiply)
Also added a new flag to tools/gf_methods that will print the names of
functions selected during gf_init.
NEON fixes/tweaks
This merge request fixes some issues and adds some tweaks to NEON code:
* SPLIT(16,4) ALTMAP implementation was broken as it only processed half the amount of data. As such, this fixed implementation is significantly slower than the old code (which is to be expected). Fixes#2
* SPLIT(16,4) implementations now merge the ARMv8 and older code path, similar to SPLIT(32,4). This fixes the ALTMAP variant, and also enables the non-ALTMAP version to have consistent sizing
* Unnecessary VTRN removed in non-ALTMAP SPLIT(16,4) as NEON allows (de)interleaving during load/store; because of this, ALTMAP isn't so useful in NEON
* This can also be done for SPLIT(32,4), but I have not implemented it
* I also pulled the `if(xor)` conditional from non-ALTMAP SPLIT(16,4) to outside the loop. It seems to improve performance a bit on my Cortex A7
* It probably should be implemented everywhere else, but I have not done this
* CARRY_FREE was incorrectly enabled on all sizes of w, when it's only available for w=4 and w=8
See merge request !16
If --enable-valgrind is given to ./configure, all tests are run with
valgrind set to fail if an error is reported ( --error-exitcode=1 )
Signed-off-by: Loic Dachary <loic@dachary.org>
Vitaliy Filippov
Shengjing Zhu