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83 lines
3.9 KiB
ArmAsm
83 lines
3.9 KiB
ArmAsm
ttl fast floating point power (ffppwr)
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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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* ffppwr *
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* fast floating point power function *
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* *
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* input: d6 - floating point exponent value *
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* d7 - floating point argument value *
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* *
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* output: d7 - result of the value taken to *
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* the power specified *
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* *
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* all registers but d7 are transparent *
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* *
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* code size: 36 bytes stack work: 42 bytes *
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* *
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* calls subroutines: ffplog, ffpexp and ffpmul2 *
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* *
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* condition codes: *
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* z - set if the result is zero *
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* n - cleared *
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* v - set if overflow occurred or base *
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* value argument was negative *
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* c - undefined *
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* x - undefined *
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* *
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* notes: *
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* 1) a negative base value will force the use*
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* if its absolute value. the "v" bit will*
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* be set upon function return. *
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* 2) if the result overflows then the *
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* maximum size value is returned with the *
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* "v" bit set in the condition code. *
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* 3) spot checks show at least six digit *
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* precision for 80 percent of the cases. *
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* *
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* time: (8mhz no wait states assumed) *
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* *
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* the timing is very data sensitive with *
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* test samples ranging from 720 to *
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* 1206 microseconds *
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* *
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*************************************************
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page
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ffppwr idnt 1,1 ffp power
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opt pcs
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section 9
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xdef ffppwr entry point
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xref ffplog,ffpexp exponent and log functions
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xref ffpmul2 multiply function
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xref ffpcpyrt copyright stub
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*****************
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* power entry *
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*****************
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* take the logorithm of the base value
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ffppwr tst.b d7 ? negative base value
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bpl.s fpppos branch positive
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and.b #$7f,d7 take absolute value
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bsr.s fpppos find result using that
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* or.b #$02,ccr force "v" bit on for negative argument
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dc.l $003c0002 *****assembler error*****
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rts return to caller
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fpppos jsr ffplog find log of the number to be used
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movem.l d3-d5,-(sp) save multiply work registers
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jsr ffpmul2 multiply by the exponent
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movem.l (sp)+,d3-d5 restore multiply work registers
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* if overflowed, ffpexp will set "v" bit and return desired result anyway
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jmp ffpexp result is exponent
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end
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end
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end
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