arch/m68k/ifpsp060/src/fplsp.S

Source file repositories/reference/linux-study-clean/arch/m68k/ifpsp060/src/fplsp.S

File Facts

System
Linux kernel
Corpus path
arch/m68k/ifpsp060/src/fplsp.S
Extension
.S
Size
293709 bytes
Lines
10981
Domain
Architecture Layer
Bucket
arch/m68k
Inferred role
Architecture Layer: arch/m68k
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

bfffo		FTEMP_HI(%a0){&0:&32}, %d0 # how many shifts are needed?
	bne.b		unnorm_shift		# hi(man) is not all zeroes

#
# hi(man) is all zeroes so see if any bits in lo(man) are set
#
unnorm_chk_lo:
	bfffo		FTEMP_LO(%a0){&0:&32}, %d0 # is operand really a zero?
	beq.w		unnorm_zero		# yes

	add.w		&32, %d0		# no; fix shift distance

#
# d0 = # shifts needed for complete normalization
#
unnorm_shift:
	clr.l		%d1			# clear top word
	mov.w		FTEMP_EX(%a0), %d1	# extract exponent
	and.w		&0x7fff, %d1		# strip off sgn

	cmp.w		%d0, %d1		# will denorm push exp < 0?
	bgt.b		unnorm_nrm_zero		# yes; denorm only until exp = 0

#
# exponent would not go < 0. therefore, number stays normalized
#
	sub.w		%d0, %d1		# shift exponent value
	mov.w		FTEMP_EX(%a0), %d0	# load old exponent
	and.w		&0x8000, %d0		# save old sign
	or.w		%d0, %d1		# {sgn,new exp}
	mov.w		%d1, FTEMP_EX(%a0)	# insert new exponent

	bsr.l		norm			# normalize UNNORM

	mov.b		&NORM, %d0		# return new optype tag
	rts

#
# exponent would go < 0, so only denormalize until exp = 0
#
unnorm_nrm_zero:
	cmp.b		%d1, &32		# is exp <= 32?
	bgt.b		unnorm_nrm_zero_lrg	# no; go handle large exponent

	bfextu		FTEMP_HI(%a0){%d1:&32}, %d0 # extract new hi(man)
	mov.l		%d0, FTEMP_HI(%a0)	# save new hi(man)

	mov.l		FTEMP_LO(%a0), %d0	# fetch old lo(man)
	lsl.l		%d1, %d0		# extract new lo(man)
	mov.l		%d0, FTEMP_LO(%a0)	# save new lo(man)

	and.w		&0x8000, FTEMP_EX(%a0)	# set exp = 0

	mov.b		&DENORM, %d0		# return new optype tag
	rts

#
# only mantissa bits set are in lo(man)
#
unnorm_nrm_zero_lrg:
	sub.w		&32, %d1		# adjust shft amt by 32

	mov.l		FTEMP_LO(%a0), %d0	# fetch old lo(man)
	lsl.l		%d1, %d0		# left shift lo(man)

	mov.l		%d0, FTEMP_HI(%a0)	# store new hi(man)
	clr.l		FTEMP_LO(%a0)		# lo(man) = 0

	and.w		&0x8000, FTEMP_EX(%a0)	# set exp = 0

Annotation

Implementation Notes