Comment # 1 on bug 1199150 from Richard Biener

'a' is x = {0, 0}, m is 8 and we run into

    /*
     *  y ^ maxExpt >= 2^{-960}
     *  =>  maxExpt = 960 / log2(y.x[0]) = 708 / log(y.x[0])
     *              = 665/((1-y.x[0] + y.x[0]^2/2 - ...)
     *              <= 665/(1-y.x[0])
     * Quick check to see if we might need to break up the exponentiation
     */
    if (m*(y.x[0]-1) / y.x[0] < -_MAX_EXPONENT * NPY_LOGE2) {
        /* Now do it carefully, calling log() */
        double lg2y = log(y.x[0]) / NPY_LOGE2;
        double lgAns = m * lg2y;
        if (lgAns <= -_MAX_EXPONENT) {
            maxExpt = (int)(nextPowerOf2(-_MAX_EXPONENT / lg2y + 1)/2);
        }
    }

but we compute

    y = frexpD(a, &yE);

and that results in {0, <optimized out>}, we bogously run into the above
and lg2y ends up as -Inf and it's all bullshit from here.

Now the question is whether we are supposed to arrive at pow2Scaled_D
with all zero 'a'.

Since the code uses -msse2 it probably should also use -mfpmath=sse
on i586 or alternatively -fexcess-precision=standard.  The build isn't
much verbose but it seems we use

[  201s] C compiler: gcc -Wno-unused-result -Wsign-compare -DNDEBUG
-fomit-frame
-pointer -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables 
-fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type -g
-DO
PENSSL_LOAD_CONF -fwrapv -fno-semantic-interposition -fomit-frame-pointer -O2
-W
all -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables
-fasynchronous-
unwind-tables -fstack-clash-protection -Werror=return-type -g -IVendor/
-fomit-f
rame-pointer -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong
-funwind-tab
les -fasynchronous-unwind-tables -fstack-clash-protection -Werror=return-type
-g
 -IVendor/ -fomit-frame-pointer -O2 -Wall -D_FORTIFY_SOURCE=2
-fstack-protector-
strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection
-We
rror=return-type -flto=auto -g -fno-strict-aliasing -fPIC
...
[  201s] extra options: '-msse -msse2'
...
[  202s] gcc: scipy/special/cephes/kolmogorov.c