问题
Gprof tells me that my computationally heavy program spends most of it's time (36%) hashing using AP-Hash.
I can't reduce the call count but I would still like to make it faster, can I call intrinsic SHA from a c program?
Do I need the intel compiler or can I stick with gcc?
回答1:
SHA instructions are now available in Goldmont architecture. It was released around September, 2016. According to the Intel Intrinsics Guide, these are the intrinsics of interest:
__m128i _mm_sha1msg1_epu32 (__m128i a, __m128i b)__m128i _mm_sha1msg2_epu32 (__m128i a, __m128i b)__m128i _mm_sha1nexte_epu32 (__m128i a, __m128i b)__m128i _mm_sha1rnds4_epu32 (__m128i a, __m128i b, const int func)__m128i _mm_sha256msg1_epu32 (__m128i a, __m128i b)__m128i _mm_sha256msg2_epu32 (__m128i a, __m128i b)__m128i _mm_sha256rnds2_epu32 (__m128i a, __m128i b, __m128i k)
GCC 5.0 and above make intrinsics available all the time for Function Specific Option Pragmas. You will need Binutils 2.24, however. Testing also shows Clang 3.7 and 3.8 support the intrinsics. Testing also shows Visual Studio 2015 can consume them, but VS2013 failed to compile them.
You can detect the availability of SHA in the preprocessor on Linux by looking for the macro __SHA__. -march=native will make it available if its native to the processor. If not, you can enable it with -msha.
$ gcc -march=native -dM -E - </dev/null | egrep -i '(aes|rdrnd|rdseed|sha)'
#define __RDRND__ 1
#define __SHA__ 1
#define __RDSEED__ 1
#define __AES__ 1
The code for using SHA1 is shown below. Its based on Intel's blog titled Intel® SHA Extensions. Another reference implementation is available from the miTLS project.
The code below is based on Intel® SHA Extensions blog. The code works with full SHA1 blocks, so const uint32_t *data is 64 bytes. You will have to add the padding for the final block and set the bit length.
It runs at about 1.7 cycles-per-byte (cpb) on an Celeron J3455. I believe Andy Polyakov has SHA1 running around 1.5 cpb for OpenSSL. For reference, an optimized C/C++ implementation will run somewhere around 9 to 10 cpb.
static void SHA1_SHAEXT_Transform(uint32_t *state, const uint32_t *data)
{
__m128i ABCD, ABCD_SAVE, E0, E0_SAVE, E1;
__m128i MASK, MSG0, MSG1, MSG2, MSG3;
// Load initial values
ABCD = _mm_loadu_si128((__m128i*) state);
E0 = _mm_set_epi32(state[4], 0, 0, 0);
ABCD = _mm_shuffle_epi32(ABCD, 0x1B);
MASK = _mm_set_epi64x(0x0001020304050607ULL, 0x08090a0b0c0d0e0fULL);
// Save current hash
ABCD_SAVE = ABCD;
E0_SAVE = E0;
// Rounds 0-3
MSG0 = _mm_loadu_si128((__m128i*) data+0);
MSG0 = _mm_shuffle_epi8(MSG0, MASK);
E0 = _mm_add_epi32(E0, MSG0);
E1 = ABCD;
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 0);
// Rounds 4-7
MSG1 = _mm_loadu_si128((__m128i*) (data+4));
MSG1 = _mm_shuffle_epi8(MSG1, MASK);
E1 = _mm_sha1nexte_epu32(E1, MSG1);
E0 = ABCD;
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 0);
MSG0 = _mm_sha1msg1_epu32(MSG0, MSG1);
// Rounds 8-11
MSG2 = _mm_loadu_si128((__m128i*) (data+8));
MSG2 = _mm_shuffle_epi8(MSG2, MASK);
E0 = _mm_sha1nexte_epu32(E0, MSG2);
E1 = ABCD;
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 0);
MSG1 = _mm_sha1msg1_epu32(MSG1, MSG2);
MSG0 = _mm_xor_si128(MSG0, MSG2);
// Rounds 12-15
MSG3 = _mm_loadu_si128((__m128i*) (data+12));
MSG3 = _mm_shuffle_epi8(MSG3, MASK);
E1 = _mm_sha1nexte_epu32(E1, MSG3);
E0 = ABCD;
MSG0 = _mm_sha1msg2_epu32(MSG0, MSG3);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 0);
MSG2 = _mm_sha1msg1_epu32(MSG2, MSG3);
MSG1 = _mm_xor_si128(MSG1, MSG3);
// Rounds 16-19
E0 = _mm_sha1nexte_epu32(E0, MSG0);
E1 = ABCD;
MSG1 = _mm_sha1msg2_epu32(MSG1, MSG0);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 0);
MSG3 = _mm_sha1msg1_epu32(MSG3, MSG0);
MSG2 = _mm_xor_si128(MSG2, MSG0);
// Rounds 20-23
E1 = _mm_sha1nexte_epu32(E1, MSG1);
E0 = ABCD;
MSG2 = _mm_sha1msg2_epu32(MSG2, MSG1);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 1);
MSG0 = _mm_sha1msg1_epu32(MSG0, MSG1);
MSG3 = _mm_xor_si128(MSG3, MSG1);
// Rounds 24-27
E0 = _mm_sha1nexte_epu32(E0, MSG2);
E1 = ABCD;
MSG3 = _mm_sha1msg2_epu32(MSG3, MSG2);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 1);
MSG1 = _mm_sha1msg1_epu32(MSG1, MSG2);
MSG0 = _mm_xor_si128(MSG0, MSG2);
// Rounds 28-31
E1 = _mm_sha1nexte_epu32(E1, MSG3);
E0 = ABCD;
MSG0 = _mm_sha1msg2_epu32(MSG0, MSG3);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 1);
MSG2 = _mm_sha1msg1_epu32(MSG2, MSG3);
MSG1 = _mm_xor_si128(MSG1, MSG3);
// Rounds 32-35
E0 = _mm_sha1nexte_epu32(E0, MSG0);
E1 = ABCD;
MSG1 = _mm_sha1msg2_epu32(MSG1, MSG0);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 1);
MSG3 = _mm_sha1msg1_epu32(MSG3, MSG0);
MSG2 = _mm_xor_si128(MSG2, MSG0);
// Rounds 36-39
E1 = _mm_sha1nexte_epu32(E1, MSG1);
E0 = ABCD;
MSG2 = _mm_sha1msg2_epu32(MSG2, MSG1);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 1);
MSG0 = _mm_sha1msg1_epu32(MSG0, MSG1);
MSG3 = _mm_xor_si128(MSG3, MSG1);
// Rounds 40-43
E0 = _mm_sha1nexte_epu32(E0, MSG2);
E1 = ABCD;
MSG3 = _mm_sha1msg2_epu32(MSG3, MSG2);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 2);
MSG1 = _mm_sha1msg1_epu32(MSG1, MSG2);
MSG0 = _mm_xor_si128(MSG0, MSG2);
// Rounds 44-47
E1 = _mm_sha1nexte_epu32(E1, MSG3);
E0 = ABCD;
MSG0 = _mm_sha1msg2_epu32(MSG0, MSG3);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 2);
MSG2 = _mm_sha1msg1_epu32(MSG2, MSG3);
MSG1 = _mm_xor_si128(MSG1, MSG3);
// Rounds 48-51
E0 = _mm_sha1nexte_epu32(E0, MSG0);
E1 = ABCD;
MSG1 = _mm_sha1msg2_epu32(MSG1, MSG0);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 2);
MSG3 = _mm_sha1msg1_epu32(MSG3, MSG0);
MSG2 = _mm_xor_si128(MSG2, MSG0);
// Rounds 52-55
E1 = _mm_sha1nexte_epu32(E1, MSG1);
E0 = ABCD;
MSG2 = _mm_sha1msg2_epu32(MSG2, MSG1);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 2);
MSG0 = _mm_sha1msg1_epu32(MSG0, MSG1);
MSG3 = _mm_xor_si128(MSG3, MSG1);
// Rounds 56-59
E0 = _mm_sha1nexte_epu32(E0, MSG2);
E1 = ABCD;
MSG3 = _mm_sha1msg2_epu32(MSG3, MSG2);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 2);
MSG1 = _mm_sha1msg1_epu32(MSG1, MSG2);
MSG0 = _mm_xor_si128(MSG0, MSG2);
// Rounds 60-63
E1 = _mm_sha1nexte_epu32(E1, MSG3);
E0 = ABCD;
MSG0 = _mm_sha1msg2_epu32(MSG0, MSG3);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 3);
MSG2 = _mm_sha1msg1_epu32(MSG2, MSG3);
MSG1 = _mm_xor_si128(MSG1, MSG3);
// Rounds 64-67
E0 = _mm_sha1nexte_epu32(E0, MSG0);
E1 = ABCD;
MSG1 = _mm_sha1msg2_epu32(MSG1, MSG0);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 3);
MSG3 = _mm_sha1msg1_epu32(MSG3, MSG0);
MSG2 = _mm_xor_si128(MSG2, MSG0);
// Rounds 68-71
E1 = _mm_sha1nexte_epu32(E1, MSG1);
E0 = ABCD;
MSG2 = _mm_sha1msg2_epu32(MSG2, MSG1);
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 3);
MSG3 = _mm_xor_si128(MSG3, MSG1);
// Rounds 72-75
E0 = _mm_sha1nexte_epu32(E0, MSG2);
E1 = ABCD;
MSG3 = _mm_sha1msg2_epu32(MSG3, MSG2);
ABCD = _mm_sha1rnds4_epu32(ABCD, E0, 3);
// Rounds 76-79
E1 = _mm_sha1nexte_epu32(E1, MSG3);
E0 = ABCD;
ABCD = _mm_sha1rnds4_epu32(ABCD, E1, 3);
// Add values back to state
E0 = _mm_sha1nexte_epu32(E0, E0_SAVE);
ABCD = _mm_add_epi32(ABCD, ABCD_SAVE);
// Save state
ABCD = _mm_shuffle_epi32(ABCD, 0x1B);
_mm_storeu_si128((__m128i*) state, ABCD);
*(state+4) = _mm_extract_epi32(E0, 3);
}
You can tell if your processor supports the SHA extensions under Linux by looking for the sha_ni flag:
$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 92
model name : Intel(R) Celeron(R) CPU J3455 @ 1.50GHz
stepping : 9
microcode : 0x1a
cpu MHz : 799.987
cache size : 1024 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 21
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36
clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc
art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclm
ulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg cx16 xtpr pdcm sse4_1 sse4_2 x2apic mov
be popcnt tsc_deadline_timer aes xsave rdrand lahf_lm 3dnowprefetch intel_pt tpr_shadow vn
mi flexpriority ept vpid fsgsbase tsc_adjust smep erms mpx rdseed smap clflushopt sha_ni x
saveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts
bugs : monitor
bogomips : 2995.20
clflush size : 64
cache_alignment : 64
address sizes : 39 bits physical, 48 bits virtual
power management:
...
Also see Are there in x86 any instructions to accelerate SHA (SHA1/2/256/512) encoding?
You can find source for both Intel SHA intrinsics and ARMv8 SHA intrinsics at Noloader GitHub | SHA-Intrinsics. They are C source files, and provide the compress function for SHA-1, SHA-224 and SHA-256. The intrinsic based implementations increase throughput approximately 3x to 4x for SHA-1, and approximately 6x to 12x for SHA-224 and SHA-256.
回答2:
Unless you work at Intel, you can't yet. SHA extensions have not yet been included on any released CPU; they are expected to be included in Intel's Skylake microarchitecture (which isn't expected until 2015 or 2016).
Moreover, the AP hash function is probably already faster than even an accelerated SHA would be. You may want to consider alternative approaches, such as optimizing the hash function or caching the results for hot values.
来源：https://stackoverflow.com/questions/21107350/how-can-i-access-sha-intrinsic