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142 lines
3.6 KiB
142 lines
3.6 KiB
20 years ago
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| sgetem.sa 3.1 12/10/90
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| The entry point sGETEXP returns the exponent portion
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| of the input argument. The exponent bias is removed
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| and the exponent value is returned as an extended
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| precision number in fp0. sGETEXPD handles denormalized
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| numbers.
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| The entry point sGETMAN extracts the mantissa of the
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| input argument. The mantissa is converted to an
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| extended precision number and returned in fp0. The
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| range of the result is [1.0 - 2.0).
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| Input: Double-extended number X in the ETEMP space in
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| the floating-point save stack.
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| Output: The functions return exp(X) or man(X) in fp0.
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| Modified: fp0.
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| Copyright (C) Motorola, Inc. 1990
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| All Rights Reserved
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| THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
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| The copyright notice above does not evidence any
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| actual or intended publication of such source code.
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|SGETEM idnt 2,1 | Motorola 040 Floating Point Software Package
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|section 8
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#include "fpsp.h"
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|xref nrm_set
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| This entry point is used by the unimplemented instruction exception
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| handler. It points a0 to the input operand.
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| SGETEXP
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.global sgetexp
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sgetexp:
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movew LOCAL_EX(%a0),%d0 |get the exponent
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bclrl #15,%d0 |clear the sign bit
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subw #0x3fff,%d0 |subtract off the bias
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fmovew %d0,%fp0 |move the exp to fp0
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rts
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.global sgetexpd
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sgetexpd:
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bclrb #sign_bit,LOCAL_EX(%a0)
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bsr nrm_set |normalize (exp will go negative)
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movew LOCAL_EX(%a0),%d0 |load resulting exponent into d0
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subw #0x3fff,%d0 |subtract off the bias
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fmovew %d0,%fp0 |move the exp to fp0
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rts
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| This entry point is used by the unimplemented instruction exception
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| handler. It points a0 to the input operand.
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| SGETMAN
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| For normalized numbers, leave the mantissa alone, simply load
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| with an exponent of +/- $3fff.
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.global sgetman
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sgetman:
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movel USER_FPCR(%a6),%d0
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andil #0xffffff00,%d0 |clear rounding precision and mode
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fmovel %d0,%fpcr |this fpcr setting is used by the 882
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movew LOCAL_EX(%a0),%d0 |get the exp (really just want sign bit)
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orw #0x7fff,%d0 |clear old exp
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bclrl #14,%d0 |make it the new exp +-3fff
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movew %d0,LOCAL_EX(%a0) |move the sign & exp back to fsave stack
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fmovex (%a0),%fp0 |put new value back in fp0
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rts
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| For denormalized numbers, shift the mantissa until the j-bit = 1,
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| then load the exponent with +/1 $3fff.
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.global sgetmand
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sgetmand:
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movel LOCAL_HI(%a0),%d0 |load ms mant in d0
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movel LOCAL_LO(%a0),%d1 |load ls mant in d1
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bsr shft |shift mantissa bits till msbit is set
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movel %d0,LOCAL_HI(%a0) |put ms mant back on stack
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movel %d1,LOCAL_LO(%a0) |put ls mant back on stack
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bras sgetman
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| SHFT
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| Shifts the mantissa bits until msbit is set.
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| input:
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| ms mantissa part in d0
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| ls mantissa part in d1
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| output:
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| shifted bits in d0 and d1
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shft:
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tstl %d0 |if any bits set in ms mant
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bnes upper |then branch
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| ;else no bits set in ms mant
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tstl %d1 |test if any bits set in ls mant
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bnes cont |if set then continue
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bras shft_end |else return
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cont:
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movel %d3,-(%a7) |save d3
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exg %d0,%d1 |shift ls mant to ms mant
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bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0
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lsll %d3,%d0 |shift first 1 to integer bit in ms mant
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movel (%a7)+,%d3 |restore d3
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bras shft_end
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upper:
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moveml %d3/%d5/%d6,-(%a7) |save registers
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bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0
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lsll %d3,%d0 |shift ms mant until j-bit is set
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movel %d1,%d6 |save ls mant in d6
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lsll %d3,%d1 |shift ls mant by count
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movel #32,%d5
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subl %d3,%d5 |sub 32 from shift for ls mant
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lsrl %d5,%d6 |shift off all bits but those that will
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| ;be shifted into ms mant
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orl %d6,%d0 |shift the ls mant bits into the ms mant
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moveml (%a7)+,%d3/%d5/%d6 |restore registers
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shft_end:
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rts
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|end
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