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[/] [or1k_soc_on_altera_embedded_dev_kit/] [trunk/] [linux-2.6/] [linux-2.6.24/] [arch/] [m68k/] [fpsp040/] [sgetem.S] - Blame information for rev 3

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1 3 xianfeng 
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|       sgetem.sa 3.1 12/10/90
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|
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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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|
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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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|
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|
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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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|
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|       Output: The functions return exp(X) or man(X) in fp0.
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|
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|       Modified: fp0.
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|
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|
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|               Copyright (C) Motorola, Inc. 1990
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|                       All Rights Reserved
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|
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|       For details on the license for this file, please see the
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|       file, README, in this same directory.
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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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|
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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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|
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|       SGETEXP
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|
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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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|
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|
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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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|
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|
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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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|
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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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|
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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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