.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