aes-s390x.pl: revisit buffer allocation and add performance data.

# Unlike previous version hardware support detection takes place only

# at the moment of key schedule setup, which is denoted in key->rounds.

# This is done, because deferred key setup can't be made MT-safe, not

# for key lengthes longer than 128 bits.

# for keys longer than 128 bits.

#

# Add AES_cbc_encrypt, which gives incredible performance improvement,

# it was measured to be ~6.6x. It's less than previously mentioned 8x,

# May 2010.

#

# Add AES_ctr32_encrypt.

# Add AES_ctr32_encrypt. If hardware-assisted, it provides up to 4.3x

# performance improvement over "generic" counter mode routine relying

# on single-block, also hardware-assisted, AES_encrypt. "Up to" refers

# to the fact that exact throughput value depends on current stack

# frame alignment within 4KB page. In worst case you get ~75% of the

# maximum, but *on average* it would be as much as ~98%. Meaning that

# worst case is unlike, it's like hitting ravine on plateau.

while (($output=shift) && ($output!~/^\w[\w\-]*\.\w+$/)) {}

open STDOUT,">$output";

	lg	$iv0,0($ivp)	# load ivec

	lg	$ivp,8($ivp)

	# prepare and allocate stack frame

	lghi	$s0,-272	# guarantee at least 256-bytes buffer

	# prepare and allocate stack frame at the top of 4K page

	# with 1K reserved for eventual signal handling

	lghi	$s0,-1024-256-16# guarantee at least 256-bytes buffer

	lghi	$s1,-4096

	lgr	$fp,$sp

	algr	$s0,$sp

	lgr	$fp,$sp

	ngr	$s0,$s1		# align at page boundary

	la	$sp,0($s0)	# alloca

	stg	$fp,0($s0)	# back-chain

	# calculate resultant buffer size

	la	$s0,16($s0)	# buffer starts at offset of 16

	slgr	$fp,$s0

	srlg	$fp,$fp,4	# $fp is buffer length in blocks, minimum 16

	slgr	$fp,$s0		# total buffer size

	lgr	$s2,$sp

	lghi	$s1,1024+16	# sl[g]fi is extended-immediate facility

	slgr	$fp,$s1		# deduct reservation to get usable buffer size

	# buffer size is at lest 256 and at most 3072+256-16

	la	$sp,1024($s0)	# alloca

	srlg	$fp,$fp,4	# convert bytes to blocks, minimum 16

	stg	$s2,0($sp)	# back-chain

	stg	$fp,8($sp)

	slgr	$len,$fp

	brc	1,.Lctr32_hw_loop	# not zero, no borrow

	algr	$fp,$len

	algr	$fp,$len	# input is shorter than allocated buffer

	lghi	$len,0

	stg	$fp,8($sp)