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.text
.type tanh,@function
.global tanh
tanh: # note: exp(x) = 2^(x*log2(e))
fldl2e
fmull 4(%esp) # x*log2(e)
fld %st(0) # x*log2(e) x*log2(e)
frndint # int(x*log2(e)) x*log2(e)
fxch # x*log2(e) int(x*log2(e))
fsub %st(1),%st(0) # frac(x*log2(e)) int(x*log2(e))
f2xm1 # 2^(fract(x*log2(e)))-1 int(x*log2(e))
fld1 # 1 2^(fract(x*log2(e)))-1 int(x*log2(e))
faddp %st(0),%st(1) # 2^(fract(x*log2(e))) int(x*log2(e))
fscale # 2^(x*log2(e)) int(x*log2(e))
fstp %st(1) # 2^(x*log2(e))
# now we have y = exp(x), but tanh(x) = (y - 1/y) / (y + 1/y)
fld1
fdiv %st(1),%st(0) # 1/y y
fld %st(0) # 1/y 1/y y
fadd %st(2) # y+1/y 1/y y
fxch %st(2) # y 1/y y+1/y
fsubp # y-1/y y+1/y
fdivp # (y-1/y)/(y+1/y)
ret
.Lende:
.size tanh,.ende-tanh
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