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Diffstat (limited to 'c/src/lib/libcpu/m68k/m68040/fpsp/sgetem.S')
| -rw-r--r-- | c/src/lib/libcpu/m68k/m68040/fpsp/sgetem.S | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/c/src/lib/libcpu/m68k/m68040/fpsp/sgetem.S b/c/src/lib/libcpu/m68k/m68040/fpsp/sgetem.S new file mode 100644 index 0000000000..d1e8a49c41 --- /dev/null +++ b/c/src/lib/libcpu/m68k/m68040/fpsp/sgetem.S @@ -0,0 +1,143 @@ +// +// $Id$ +// +// sgetem.sa 3.1 12/10/90 +// +// The entry point sGETEXP returns the exponent portion +// of the input argument. The exponent bias is removed +// and the exponent value is returned as an extended +// precision number in fp0. sGETEXPD handles denormalized +// numbers. +// +// The entry point sGETMAN extracts the mantissa of the +// input argument. The mantissa is converted to an +// extended precision number and returned in fp0. The +// range of the result is [1.0 - 2.0). +// +// +// Input: Double-extended number X in the ETEMP space in +// the floating-point save stack. +// +// Output: The functions return exp(X) or man(X) in fp0. +// +// Modified: fp0. +// +// +// Copyright (C) Motorola, Inc. 1990 +// All Rights Reserved +// +// THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA +// The copyright notice above does not evidence any +// actual or intended publication of such source code. + +//SGETEM idnt 2,1 | Motorola 040 Floating Point Software Package + + |section 8 + +#include "fpsp.defs" + + |xref nrm_set + +// +// This entry point is used by the unimplemented instruction exception +// handler. It points a0 to the input operand. +// +// +// +// SGETEXP +// + + .global sgetexp +sgetexp: + movew LOCAL_EX(%a0),%d0 //get the exponent + bclrl #15,%d0 //clear the sign bit + subw #0x3fff,%d0 //subtract off the bias + fmovew %d0,%fp0 //move the exp to fp0 + rts + + .global sgetexpd +sgetexpd: + bclrb #sign_bit,LOCAL_EX(%a0) + bsr nrm_set //normalize (exp will go negative) + movew LOCAL_EX(%a0),%d0 //load resulting exponent into d0 + subw #0x3fff,%d0 //subtract off the bias + fmovew %d0,%fp0 //move the exp to fp0 + rts +// +// +// This entry point is used by the unimplemented instruction exception +// handler. It points a0 to the input operand. +// +// +// +// SGETMAN +// +// +// For normalized numbers, leave the mantissa alone, simply load +// with an exponent of +/- $3fff. +// + .global sgetman +sgetman: + movel USER_FPCR(%a6),%d0 + andil #0xffffff00,%d0 //clear rounding precision and mode + fmovel %d0,%fpcr //this fpcr setting is used by the 882 + movew LOCAL_EX(%a0),%d0 //get the exp (really just want sign bit) + orw #0x7fff,%d0 //clear old exp + bclrl #14,%d0 //make it the new exp +-3fff + movew %d0,LOCAL_EX(%a0) //move the sign & exp back to fsave stack + fmovex (%a0),%fp0 //put new value back in fp0 + rts + +// +// For denormalized numbers, shift the mantissa until the j-bit = 1, +// then load the exponent with +/1 $3fff. +// + .global sgetmand +sgetmand: + movel LOCAL_HI(%a0),%d0 //load ms mant in d0 + movel LOCAL_LO(%a0),%d1 //load ls mant in d1 + bsr shft //shift mantissa bits till msbit is set + movel %d0,LOCAL_HI(%a0) //put ms mant back on stack + movel %d1,LOCAL_LO(%a0) //put ls mant back on stack + bras sgetman + +// +// SHFT +// +// Shifts the mantissa bits until msbit is set. +// input: +// ms mantissa part in d0 +// ls mantissa part in d1 +// output: +// shifted bits in d0 and d1 +shft: + tstl %d0 //if any bits set in ms mant + bnes upper //then branch +// ;else no bits set in ms mant + tstl %d1 //test if any bits set in ls mant + bnes cont //if set then continue + bras shft_end //else return +cont: + movel %d3,-(%a7) //save d3 + exg %d0,%d1 //shift ls mant to ms mant + bfffo %d0{#0:#32},%d3 //find first 1 in ls mant to d0 + lsll %d3,%d0 //shift first 1 to integer bit in ms mant + movel (%a7)+,%d3 //restore d3 + bras shft_end +upper: + + moveml %d3/%d5/%d6,-(%a7) //save registers + bfffo %d0{#0:#32},%d3 //find first 1 in ls mant to d0 + lsll %d3,%d0 //shift ms mant until j-bit is set + movel %d1,%d6 //save ls mant in d6 + lsll %d3,%d1 //shift ls mant by count + movel #32,%d5 + subl %d3,%d5 //sub 32 from shift for ls mant + lsrl %d5,%d6 //shift off all bits but those that will +// ;be shifted into ms mant + orl %d6,%d0 //shift the ls mant bits into the ms mant + moveml (%a7)+,%d3/%d5/%d6 //restore registers +shft_end: + rts + + |end |