Clarify commentary in sha512-sparcv9.pl.

# Performance is >75% better than 64-bit code generated by Sun C and

# over 2x than 32-bit code. X[16] resides on stack, but access to it

# is scheduled for L2 latency and staged through 32 least significant

# bits of %l0-%l7. The latter is done to achieve 32-/64-bit bit ABI

# bits of %l0-%l7. The latter is done to achieve 32-/64-bit ABI

# duality. Nevetheless it's ~40% faster than SHA256, which is pretty

# good [optimal coefficient is 50%].

#

#

# It's not any faster than 64-bit code generated by Sun C 5.8. This is

# because 64-bit code generator has the advantage of using 64-bit

# loads to access X[16], which I consciously traded for 32-/64-bit ABI

# duality [as per above]. But it surpasses 32-bit Sun C generated code

# by 60%, not to mention that it doesn't suffer from severe decay when

# running 4 times physical cores threads and that it leaves gcc [3.4]

# behind by over 4x factor! If compared to SHA256, single thread

# loads(*) to access X[16], which I consciously traded for 32-/64-bit

# ABI duality [as per above]. But it surpasses 32-bit Sun C generated

# code by 60%, not to mention that it doesn't suffer from severe decay

# when running 4 times physical cores threads and that it leaves gcc

# [3.4] behind by over 4x factor! If compared to SHA256, single thread

# performance is only 10% better, but overall throughput for maximum

# amount of threads for given CPU exceeds corresponding one of SHA256

# by 30% [again, optimal coefficient is 50%].

#

# (*)	Unlike pre-T1 UltraSPARC loads on T1 are executed strictly

#	in-order, i.e. load instruction has to complete prior next

#	instruction in given thread is executed, even if the latter is

#	not dependent on load result! This means that on T1 two 32-bit

#	loads are always slower than one 64-bit load. Once again this

#	is unlike pre-T1 UltraSPARC, where, if scheduled appropriately,

#	2x32-bit loads can be as fast as 1x64-bit ones.

$bits=32;

for (@ARGV)	{ $bits=64 if (/\-m64/ || /\-xarch\=v9/); }