To reduce the cache missing events, the mix layout is changed
to PMULL+CRC. It also relaxes the final delay caused by data
dependency.
As results, the cold perf was improved about 20% and warm perf
was improved about 4%.
Change-Id: I7756f846edcb4f1665b4643a5a0e02283938cfdf
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
Hardware folding algorithm depend on CRC32 and PMULL instruction.
And it should match both flags .
Change-Id: I361068402db1fe6d7c0bd8d2c7048f1d94880233
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
+ Utilise `pmull2` instruction in main loops of arm64 crc functions and
avoid the need for `dup` to align multiplicands.
+ Use just 1 ASIMD register to hold both 64b p4 constants,
appropriately aligned.
+ Interleave quadword `ldr` with `pmull{2}` to avoid unnecessary stalls
on existing LITTLE uarch (which can only issue these instructions every
other cycle).
+ Similarly interleave scalar instructions with ASIMD instructions to
increase likelihood of instruction level parallelism on a variety of
uarch.
+ Cut down on needless instructions in non-critical sections to help
performance for small buffers.
+ Extract common instruction sequences into inner macros and moved
them into shared header - crc_common_pmull.h
+ Use the same human readable register aliases and register allocation
in all 4 implementations, never refer to registers without using human
readable alias.
+ Use #defines rather than .req to allow use of same names across
several implementations
+ Reduce tail case size from 1024B to 64B
+ Phrased the `eor` instructions in the main loop to more clearly show
that we can rewrite pairs of `eor` instructions with a single `eor3`
instruction in the presence of Armv8.2-SHA (should probably be an option
in multibinary in future).
Change-Id: I3688193ea4ad88b53cf47e5bd9a7fd5c2b4401e1
Signed-off-by: Samuel Lee <samuel.lee@microsoft.com>
This issue occurs when dynamic compilation is used
and gcc's -fsanitize memory detection option is turned on.
[Log] relocation truncated to fit: R_AARCH64_LD_PREL_LO19 against `.rodata'
Change-Id: Ic2f82264610552f347e043f82ac5ebafc93748e2
Signed-off-by: Zhiyuan Zhu <zhiyuan.zhu@arm.com>
Some CPUs report "illegal instruction" error for the crc test because
they do not support the relevant optional feature . This can be fixed by
introducing CPU feature detection for AArch64 .
The difference with the x86 implementation is the dispatcher . It is based
on the glibc function `getauxval(AT_HWCAP)` and `getauxval(AT_HWCAP2)` , not
registers or instructions .
On a heterogeneous system (big.LITTLE) , it is dangerous to detect CPU
features using identification registers . And while it is possible to use
architectural feature registers from userspace on recent kernels, this
won't necessarily work with older platforms . Thus we use the HW_CAPs
exported from the kernel (and visible in getauxval) as the solution.
- According to kernel suggestion , getauxval should be used for this purpose .
- [CPU Feature detection](https://github.com/torvalds/linux/blob/master/Documentation/arm64/cpu-feature-registers.rst)
- According to AAPCS result/paramter registers should be saved/restore for function call
- [AAPCS](http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf)
- [GLibc](https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=blob;f=sysdeps/aarch64/dl-trampoline.S)
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
Change-Id: Ic9abe0d2268ac95537e1abf10acc642fc58a5054
Some arm64 machines don't support pmull instructions, so set these
crc interface to base functions. For long-term solution, will
provide better multi-binary support with cpu features detection.
Change-Id: I02791a2a50283dc8df2f9ba124eb309912b5b4b7
Signed-off-by: Zhiyuan Zhu <zhiyuan.zhu@arm.com>
