mirror of https://github.com/lianthony/NT4.0
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
83 lines
2.9 KiB
83 lines
2.9 KiB
#++
|
|
# Copyright 1991, Digital Equipment Corporation
|
|
#
|
|
# int ots_extzv(char *addr, int position, unsigned size)
|
|
#
|
|
# Arbitrary unsigned bitfield extraction
|
|
#
|
|
# Special conventions: No stack space, r0, r16-r18 and r26-r28 ONLY,
|
|
# no linkage pointer required.
|
|
# (Warning: The auto-loader potentially takes some regs across
|
|
# the call if this is being used in a shared lib. environment.)
|
|
#
|
|
# See also: ots_extv (just uses sra in place of srl in some cases...)
|
|
#
|
|
# 001 16 Aug 1991 KDG Initial version
|
|
#
|
|
# 002 4 Sep 1991 KDG Bugfix/improvements
|
|
#
|
|
# 003 19 May 1992 KDG Changes for common VMS/OSF sources
|
|
#
|
|
# 004 22 Sep 1992 KDG Add case-sensitive name
|
|
#
|
|
# 005 26 Jan 1993 KDG Add underscore
|
|
|
|
#include "ots_defs.hs"
|
|
|
|
#
|
|
# Totally general field extract - arbitrary run-time field of 0-64 bits
|
|
# at an unknown alignment target.
|
|
#
|
|
# Conceptually, this operation takes a 67 bit bit-address, which is the sum
|
|
# of a byte-aligned memory address and the bit offset (which is signed).
|
|
#
|
|
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
# | | | | | | | | | | | | | | | | | | | | | | | | | |.|.|.|Q|L|W|B|
|
|
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
# | | | | | | | | | | | | | | | | | | | | | | | | | | |.|.|.|b|b|b|
|
|
# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
#
|
|
# Inputs:
|
|
# r16 - input address
|
|
# r17 - input bit offset
|
|
# r18 - input size
|
|
#
|
|
# This is based on the code GEM generates when not using an out-of-line
|
|
# routine.
|
|
#
|
|
.globl _OtsFieldExtractUnsigned
|
|
.ent _OtsFieldExtractUnsigned
|
|
_OtsFieldExtractUnsigned:
|
|
.set noat
|
|
.set noreorder
|
|
.frame sp,0,r26
|
|
sra r17, 3, r27 # get byte part of bit offset (signed!)
|
|
ble r18, zero # check for zero size - no memory access
|
|
addq r16, r27, r16 # add to initial base addr.
|
|
ldq_u r0, (r16) # start load first or only quadword
|
|
and r16, 7, r27 # get byte-in-quadword of first bit
|
|
and r17, 7, r17 # get bit-in-byte from bit offset
|
|
s8addq r27, r17, r17 # form the true bit offset in the quadword
|
|
addq r17, r18, r27 # get bit offset of bit following field
|
|
cmpule r27, 64, r28 # if <=64, field is contained in 1 quadword
|
|
beq r28, double # handle double case if not
|
|
# common case - fall through, load result hopefully already available
|
|
single: negq r27, r27 # <5:0> = bits for right shift
|
|
sll r0, r27, r0 # move to high bits
|
|
addq r27, r17, r27 # bits for left shift
|
|
srl r0, r27, r0 # and shift into final position
|
|
ret r31, (r26)
|
|
double: ldq_u r28, 8(r16) # load second quadword
|
|
srl r0, r27, r0 # move top piece over
|
|
negq r27, r27 # get shift bits for piece in 2nd word
|
|
sll r28, r27, r28 # move field in 2nd lw to high bits
|
|
bis r0, r28, r0 # form final value
|
|
negq r18, r27 # <5:0> = bits for right shift
|
|
srl r0, r27, r0 # and shift into final position
|
|
ret r31, (r26)
|
|
zero: mov 0, r0 # zero-sized field extracts return 0
|
|
ret r31, (r26)
|
|
|
|
.set at
|
|
.set reorder
|
|
.end _OtsFieldExtractUnsigned
|