Optimizations are:
1. Reduce code size (-81 bytes).
2. Remove redundant move instructions.
3. Slightly improve instruction selection/scheduling where
possible.
4. Prefer registers which get short instruction encoding.
5. Reduce rodata size (-32 bytes).
Result is roughly a 17-18% speedup:
Function, New Time, Old Time, New / Old
_ZGVdN8v_tanhf, 1.977, 2.402, 0.823
tanhf-avx2 and tanhf-sse4 use the same data tables so we can save
over 4kb using a shared datatable. This does increase the memory
footprint of the sse4 version (as now all the targets are 32 bytes
instead of 16), generally it seems worth the code size save.
NB: This patch doesn't do anything itself, it is setup for future
patches.
Optimizations are:
1. Reduce code size (-67 bytes).
2. Remove redundant move instructions.
3. Slightly improve instruction selection/scheduling where
possible.
4. Reduce rodata usage (-448 bytes).
Result is roughly a 14% speedup:
Function, New Time, Old Time, New / Old
_ZGVeN16v_tanhf, 0.649, 0.752, 0.863
Improvements are:
1. Reduce code size (-62 bytes).
2. Remove redundant move instructions.
3. Slightly improve instruction selection/scheduling where
possible.
4. Prefer registers which get short instruction encoding.
5. Reduce rodata usage (-16 bytes).
The throughput improvement is not significant as the port 0 bottleneck
is unavoidable.
Function, New Time, Old Time, New / Old
_ZGVbN4v_atanhf, 8.821, 8.903, 0.991
Improvements are:
1. Reduce code size (-60 bytes).
2. Remove redundant move instructions.
3. Slightly improve instruction selection/scheduling where
possible.
4. Prefer registers which get short instruction encoding.
5. Shrink rodata usage (-32 bytes).
The throughput improvement is not that significant (3-5%) as the
port 0 bottleneck is unavoidable.
Function, New Time, Old Time, New / Old
_ZGVdN8v_atanhf, 2.799, 2.923, 0.958
Improvements are:
1. Reduce code size (-64 bytes).
2. Remove redundant move instructions.
3. Slightly improve instruction selection/scheduling where
possible.
4. Reduce rodata size ([-128, -188] bytes).
The throughput improvement is not significant as the port 0 bottleneck
is unavoidable.
Function, New Time, Old Time, New / Old
_ZGVeN16v_atanhf, 1.39, 1.408, 0.987
Skip the chroot test if the database isn't loaded
correctly (because the chroot test uses some
existing DB state).
The __stat64_time64 -> fstatat call can fail if
running under an (aggressive) seccomp filter,
like Firefox seems to use.
This manifested in a crash when using glib built
with FAM support with such a Firefox build.
Suggested-by: DJ Delorie <dj@redhat.com>
Signed-off-by: Sam James <sam@gentoo.org>
Reviewed-by: DJ Delorie <dj@redhat.com>
It's interesting if we have a null action list,
so an assert is worthwhile.
Suggested-by: DJ Delorie <dj@redhat.com>
Signed-off-by: Sam James <sam@gentoo.org>
Reviewed-by: DJ Delorie <dj@redhat.com>
commit 6dcbb7d95d
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Mon Jun 6 21:11:33 2022 -0700
x86: Shrink code size of memchr-avx2.S
Changed how the page cross case aligned string (rdi) in
rawmemchr. This was incompatible with how
`L(cross_page_continue)` expected the pointer to be aligned and
would cause rawmemchr to read data start started before the
beginning of the string. What it would read was in valid memory
but could count CHAR matches resulting in an incorrect return
value.
This commit fixes that issue by essentially reverting the changes to
the L(page_cross) case as they didn't really matter.
Test cases added and all pass with the new code (and where confirmed
to fail with the old code).
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Some nptl tests inadvertently use the host's gdb to verify
libthread_db.so, which is loaded with the host's runtime. This causes
a couple of test failures when the host glibc does not support DT_RELR.
The not correct, but simple, workaround is to build without DT_RELR
as this library is otherwise likely to load on glibc 2.17 and newer
today.
This allows tst-pthread-gdb-attach{,-static} to continue working
when testing on a gdb loaded with an older glibc.
This avoids a failure in tst-pthread-gdb-attach similar to:
Trying host libthread_db library: .../build/glibc/nptl_db/libthread_db.so.1.
dlopen failed: /lib64/libc.so.6: version `GLIBC_ABI_DT_RELR' not found (required by .../build/glibc/nptl_db/libthread_db.so.1).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Give fall-through path to `vzeroupper` and taken-path to `vzeroall`.
Generally even on machines with RTM the expectation is the
string-library functions will not be called in transactions.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This is not meant as a performance optimization. The previous code was
far to liberal in aligning targets and wasted code size unnecissarily.
The total code size saving is: 64 bytes
There are no non-negligible changes in the benchmarks.
Geometric Mean of all benchmarks New / Old: 1.000
Full xcheck passes on x86_64.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This is not meant as a performance optimization. The previous code was
far to liberal in aligning targets and wasted code size unnecissarily.
The total code size saving is: 59 bytes
There are no major changes in the benchmarks.
Geometric Mean of all benchmarks New / Old: 0.967
Full xcheck passes on x86_64.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The new code:
1. prioritizes smaller user-arg lengths more.
2. optimizes target placement more carefully
3. reuses logic more
4. fixes up various inefficiencies in the logic. The biggest
case here is the `lzcnt` logic for checking returns which
saves either a branch or multiple instructions.
The total code size saving is: 306 bytes
Geometric Mean of all benchmarks New / Old: 0.760
Regressions:
There are some regressions. Particularly where the length (user arg
length) is large but the position of the match char is near the
beginning of the string (in first VEC). This case has roughly a
10-20% regression.
This is because the new logic gives the hot path for immediate matches
to shorter lengths (the more common input). This case has roughly
a 15-45% speedup.
Full xcheck passes on x86_64.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The new code:
1. prioritizes smaller user-arg lengths more.
2. optimizes target placement more carefully
3. reuses logic more
4. fixes up various inefficiencies in the logic. The biggest
case here is the `lzcnt` logic for checking returns which
saves either a branch or multiple instructions.
The total code size saving is: 263 bytes
Geometric Mean of all benchmarks New / Old: 0.755
Regressions:
There are some regressions. Particularly where the length (user arg
length) is large but the position of the match char is near the
beginning of the string (in first VEC). This case has roughly a
20% regression.
This is because the new logic gives the hot path for immediate matches
to shorter lengths (the more common input). This case has roughly
a 35% speedup.
Full xcheck passes on x86_64.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The new code:
1. prioritizes smaller lengths more.
2. optimizes target placement more carefully.
3. reuses logic more.
4. fixes up various inefficiencies in the logic.
The total code size saving is: 394 bytes
Geometric Mean of all benchmarks New / Old: 0.874
Regressions:
1. The page cross case is now colder, especially re-entry from the
page cross case if a match is not found in the first VEC
(roughly 50%). My general opinion with this patch is this is
acceptable given the "coldness" of this case (less than 4%) and
generally performance improvement in the other far more common
cases.
2. There are some regressions 5-15% for medium/large user-arg
lengths that have a match in the first VEC. This is because the
logic was rewritten to optimize finds in the first VEC if the
user-arg length is shorter (where we see roughly 20-50%
performance improvements). It is not always the case this is a
regression. My intuition is some frontend quirk is partially
explaining the data although I haven't been able to find the
root cause.
Full xcheck passes on x86_64.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Add a second iteration for memrchr to set `pos` starting from the end
of the buffer.
Previously `pos` was only set relative to the beginning of the
buffer. This isn't really useful for memrchr because the beginning
of the search space is (buf + len).
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The RTM vzeroupper mitigation has no way of replacing inline
vzeroupper not before a return.
This can be useful when hoisting a vzeroupper to save code size
for example:
```
L(foo):
cmpl %eax, %edx
jz L(bar)
tzcntl %eax, %eax
addq %rdi, %rax
VZEROUPPER_RETURN
L(bar):
xorl %eax, %eax
VZEROUPPER_RETURN
```
Can become:
```
L(foo):
COND_VZEROUPPER
cmpl %eax, %edx
jz L(bar)
tzcntl %eax, %eax
addq %rdi, %rax
ret
L(bar):
xorl %eax, %eax
ret
```
This code does not change any existing functionality.
There is no difference in the objdump of libc.so before and after this
patch.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This patch does not touch any existing code and is only meant to be a
tool for future patches so that simple source files can more easily be
maintained to target multiple VEC classes.
There is no difference in the objdump of libc.so before and after this
patch.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
__strncpy_power9 initializes VR 18 with zeroes to be used throughout the
code, including when zero-padding the destination string. However, the
v18 reference was mistakenly being used for stxv and stxvl, which take a
VSX vector as operand. The code ended up using the uninitialized VSR 18
register by mistake.
Both occurrences have been changed to use the proper VSX number for VR 18
(i.e. VSR 50).
Tested on powerpc, powerpc64 and powerpc64le.
Signed-off-by: Kewen Lin <linkw@gcc.gnu.org>
Add an initial SVE memcpy implementation. Copies up to 32 bytes use SVE
vectors which improves the random memcpy benchmark significantly.
Cleanup the memcpy and memmove ifunc selectors.
Adding a 512-bit EVEX version of strstr. The algorithm works as follows:
(1) We spend a few cycles at the begining to peek into the needle. We
locate an edge in the needle (first occurance of 2 consequent distinct
characters) and also store the first 64-bytes into a zmm register.
(2) We search for the edge in the haystack by looking into one cache
line of the haystack at a time. This avoids having to read past a page
boundary which can cause a seg fault.
(3) If an edge is found in the haystack we first compare the first
64-bytes of the needle (already stored in a zmm register) before we
proceed with a full string compare performed byte by byte.
Benchmarking results: (old = strstr_sse2_unaligned, new = strstr_avx512)
Geometric mean of all benchmarks: new / old = 0.66
Difficult skiptable(0) : new / old = 0.02
Difficult skiptable(1) : new / old = 0.01
Difficult 2-way : new / old = 0.25
Difficult testing first 2 : new / old = 1.26
Difficult skiptable(0) : new / old = 0.05
Difficult skiptable(1) : new / old = 0.06
Difficult 2-way : new / old = 0.26
Difficult testing first 2 : new / old = 1.05
Difficult skiptable(0) : new / old = 0.42
Difficult skiptable(1) : new / old = 0.24
Difficult 2-way : new / old = 0.21
Difficult testing first 2 : new / old = 1.04
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The next revision of the ISO C standard has added the timegm function
(that was already supported in glibc). Update the feature test
conditionals on its declaration in <time.h> accordingly.
Tested for x86_64.
Newer versions of GNU grep (after grep 3.7, not inclusive) will warn on
'egrep' and 'fgrep' invocations.
Convert usages within the tree to their expanded non-aliased counterparts
to avoid irritating warnings during ./configure and the test suite.
Signed-off-by: Sam James <sam@gentoo.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Added in Linux 5.15 (884a7e5964e06ed93c7771c0d7cf19c09a8946f1), the new
syscalls allows a caller to free the memory of a dying target process.
Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
It was added on Linux 5.10 (ecb8ac8b1f146915aa6b96449b66dd48984caacc)
with the same functionality as madvise but using a pidfd of the target
process.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This definition is only used as a fallback with old kernel headers.
The change follows kernel commit bfdf4e6208051ed7165b2e92035b4bf11
("rseq: Remove broken uapi field layout on 32-bit little endian").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The issue is only when used within libc.so (iconvconfig already builds
with _TIME_SIZE=64).
This is a missing spot initially from 52a5fe70a2.
Checked on i686-linux-gnu.
LoongArch is going to be the first architecture supported by Linux that
has neither fstat* nor newfstatat [1], instead exclusively relying on
statx. So in fstatat64's implementation, we need to also enable statx
usage if neither fstatat64 nor newfstatat is present, to prepare for
this new case of kernel ABI.
[1]: https://lore.kernel.org/all/20220518092619.1269111-1-chenhuacai@loongson.cn/
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Linux 5.18 adds a constant MADV_DONTNEED_LOCKED (defined in multiple
header files, but with the same value on all architectures). Add this
constant to bits/mman-linux.h.
Tested for x86_64.
