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140 lines
3.6 KiB
140 lines
3.6 KiB
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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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| 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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| 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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