PROOF-OF-CONCEPT Replace x86_64 asm by CryptOpt output #1254

@dderjoel

It managed to convince autotools to compile your asm. It seems slower than our C code, at least on my machine:

12th Gen Intel(R) Core(TM) i7-1260P, TurboBoost disabled

./bench_internal field

Benchmark                     ,    Min(us)    ,    Avg(us)    ,    Max(us)

this PR (e2684293b1b72a1ab5974a2864549cea2788cf95), --with-asm=x86_64 (which is the default)
field_sqr                     ,     0.0296    ,     0.0297    ,     0.0297 
field_mul                     ,     0.0339    ,     0.0341    ,     0.0344 

master (464a9115b4eda46b464d22829ece4f51985944bf), --with-asm=x86_64 (which is the default)
field_sqr                     ,     0.0270    ,     0.0271    ,     0.0272 
field_mul                     ,     0.0359    ,     0.0359    ,     0.0360 

master, --with-asm=no (464a9115b4eda46b464d22829ece4f51985944bf), gcc 12.2.1 -02:
Benchmark                     ,    Min(us)    ,    Avg(us)    ,    Max(us)
field_sqr                     ,     0.0236    ,     0.0238    ,     0.0240 
field_mul                     ,     0.0283    ,     0.0284    ,     0.0286

By the way, we should really get rid of our current ASM in the short term, at least for the field. GCC beats it significantly.

1. What are the magic incantations to convince Autotools?
2. I've added the fiat-dettman-c code the benchmark is attached (but probably not too representative, as I cant compare against the asm, as I don't have the magic words for auto tools)

original C

$ ./bench_ecmult Benchmark , Min(us) , Avg(us) , Max(us)

ecmult_gen , 18.4 , 18.6 , 18.8
ecmult_const , 36.3 , 36.7 , 39.0
ecmult_1p , 28.9 , 29.3 , 29.8
ecmult_0p_g , 20.2 , 20.6 , 23.7
ecmult_1p_g , 16.9 , 17.0 , 17.2
ecmult_multi_0p_g , 20.0 , 20.3 , 20.7

cryptopt asm

$ ./bench_ecmult
Benchmark , Min(us) , Avg(us) , Max(us)

ecmult_gen , 17.7 , 18.1 , 19.2
ecmult_const , 34.1 , 35.1 , 37.9
ecmult_1p , 27.2 , 28.1 , 29.4
ecmult_0p_g , 18.7 , 19.5 , 21.4
ecmult_1p_g , 16.2 , 16.9 , 18.6
ecmult_multi_0p_g , 18.8 , 19.4 , 20.2

fiat-dettman c ./bench_ecmult Benchmark , Min(us) , Avg(us) , Max(us)

ecmult_gen , 19.5 , 20.1 , 21.5
ecmult_const , 38.9 , 40.4 , 41.4
ecmult_1p , 30.3 , 31.2 , 33.5
ecmult_0p_g , 20.8 , 21.3 , 24.0
ecmult_1p_g , 17.5 , 18.1 , 18.7
ecmult_multi_0p_g , 22.1 , 23.2 , 25.3

Tracked in #1261.