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111 lines
4.5 KiB
ArmAsm
111 lines
4.5 KiB
ArmAsm
ttl ieee format equivalent (iefsin/iefcos/ieftan)
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***************************************
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* (c) copyright 1981 by motorola inc. *
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***************************************
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*************************************************
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* iefsin iefcos ieftan *
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* ieee format equivalent sine/cosine/tangent *
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* *
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* input: d7 - ieee format argument (radians) *
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* *
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* output: d7 - ieee format function result *
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* *
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* all other registers totally transparent *
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* *
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* maximum stack used: 54 bytes *
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* *
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* condition codes: *
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* z - set if result in d7 is zero *
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* n - set if result in d7 is negative *
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* c - undefined *
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* v - set if result is nan (not-a-number)*
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* (input magnitude too large or nan) *
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* x - undefined *
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* *
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* functions: *
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* iefsin - sine result *
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* iefcos - cosine result *
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* ieftan - tangent result *
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* *
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* notes: *
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* 1) input values are in radians. *
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* 2) input arguments larger than two pi *
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* suffer reduced precision. the larger *
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* the argument, the smaller the precision.*
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* excessively large arguments which have *
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* less than 5 bits of precision are *
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* returned as a nan with the "v" bit set. *
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* 3) the sign of tangents with infinite *
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* value is undefined, however we return *
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* a positive infinity. *
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* 4) spot checks show relative errors bounded*
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* by 4 x 10**-7 but for arguments close to*
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* pi/2 intervals where 10**-5 is seen. *
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* *
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*************************************************
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page
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iefsin idnt 1,1 ieee format equivalent sine/cosine/tangent
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opt pcs
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section 9
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xdef iefsin,iefcos,ieftan entry points
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xref ffpsin,ffpcos,ffptan ffp transcendentals
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xref iefsop single operand front-ender
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xref ieftieee back-end convert back to ieee format
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xref iefrtnan back-end return ieee nan routine
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xref ffpcpyrt copyright stub
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vbit equ $0002 condition code register "v" bit mask
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ffpsign equ.b $80 sign in fast floating point value
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***********************
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* tangent entry point *
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***********************
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ieftan jsr iefsop parse the operand
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bra.s ieftnrm +0 branch not infinity or nan
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jmp iefrtnan +2 return nan for infinity
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* perform tangent function with normalized number
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ieftnrm jsr ffptan find tangent
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bra.s iefcmn enter common exit code
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**********************
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* cosine entry point *
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**********************
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iefcos jsr iefsop parse the operand
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bra.s iefcnrm +0 branch not infinity or nan
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jmp iefrtnan +2 return nan for infinity
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* perform cosine function with normalized number
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iefcnrm jsr ffpcos find cosine
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bra.s iefcmn enter common exit code
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********************
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* sine entry point *
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********************
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iefsin jsr iefsop parse the operand
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bra.s iefsnrm +0 branch not infinity or nan
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jmp iefrtnan +2 return nan for infinity
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* perform sine function with normalized number
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iefsnrm jsr ffpsin find sine
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iefcmn bvc ieftieee return if had enough precision
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* overflow can mean true infinity result or not enough precision
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* we can test for not enough precision by checking for largest possible value
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move.l d7,d5 copy over ffp format result
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or.b #ffpsign,d5 set sign bit to a one
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sub.l #1,d5 test for all one bits
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* bne iefrtnan no, not enough precision, return a nan
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bne dobranch for 16-bit non-MMU problem
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tst.b d7 reset ccr as it was
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or.b #vbit,ccr and show overflow occured
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jmp ieftieee restore with infinity of proper sign
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dobranch:
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jmp iefrtnan
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end
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