forked from KolibriOS/kolibrios
Magomed Kostoev (mkostoevr)
71b99beec5
git-svn-id: svn://kolibrios.org@7855 a494cfbc-eb01-0410-851d-a64ba20cac60
61 lines
1.6 KiB
NASM
61 lines
1.6 KiB
NASM
|
|
format ELF
|
|
include '../proc32.inc'
|
|
section '.text' executable
|
|
|
|
public exp_ as "exp"
|
|
public exp2_ as "exp2"
|
|
|
|
SaveCW dw ?
|
|
MaskedCW dw ?
|
|
|
|
; 2**x = 2**int(x) * 2**frac(x).
|
|
; We can easily compute 2**int(x) with fscale and
|
|
; 2**frac(x) using f2xm1.
|
|
exp2_int:
|
|
fstcw [SaveCW]
|
|
|
|
; Modify the control word to truncate when rounding.
|
|
|
|
fstcw [MaskedCW]
|
|
or byte ptr MaskedCW + 1, 1100b
|
|
fldcw [MaskedCW]
|
|
|
|
fld st0 ;Duplicate tos.
|
|
fld st0
|
|
frndint ;Compute integer portion.
|
|
|
|
fxch ;Swap whole and int values.
|
|
fsub st0, st1 ;Compute fractional part.
|
|
|
|
f2xm1 ;Compute 2**frac(x)-1.
|
|
fld1
|
|
faddp st1, st0 ;Compute 2**frac(x).
|
|
|
|
fxch ;Get integer portion.
|
|
fld1 ;Compute 1*2**int(x).
|
|
fscale
|
|
fstp st1 ;Remove st(1) (which is 1).
|
|
|
|
fmulp st1, st0 ;Compute 2**int(x) * 2**frac(x).
|
|
fstp st1 ;Remove st1
|
|
|
|
fldcw [SaveCW] ;Restore rounding mode.
|
|
ret
|
|
|
|
exp_:
|
|
; exp(x) = 2**(x * lg(e))
|
|
|
|
fld qword[esp+4]
|
|
fldl2e ;Put lg(e) onto the stack.
|
|
fmulp st1, st0 ;Compute x*lg(e).
|
|
call exp2_int;Compute 2**(x * lg(e))
|
|
ret
|
|
|
|
exp2_:
|
|
fld qword[esp+4]
|
|
call exp2_int;Compute 2 ** x
|
|
ret
|
|
|
|
|