segfault in graphene_matrix_interpolate() with clang and scalar SIMD4f

[ebassi]

when running the scalar implementations of the graphene_simd4f_t type, we get a segmentation fault inside graphene_matrix_interpolate() when calculating the linear interpolation of the two perspective vec4.

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7df0ebb in graphene_matrix_interpolate (a=<optimized out>, b=<optimized out>, factor=<optimized out>, 
    res=0x7fffffffded8) at graphene-matrix.c:997
997   res->value.w = graphene_simd4f_interpolate (perspective_a.value,
(gdb) print res
$1 = (graphene_matrix_t *) 0x7fffffffded8
(gdb) print res->value
$2 = {x = {5.88428767e-39, 0, -nan(0x7fdf68), 4.59163468e-41}, y = {-2.38550409e+21, 6.72623263e-44, 0, 0}, z = {
    7.00649232e-44, 0, 8.83997365e-39, 0}, w = {5.88777971e-39, 0, 5.88867373e-39, 0}}
(gdb) print res->value.w
$3 = {5.88777971e-39, 0, 5.88867373e-39, 0}
(gdb) print perspective_a
$4 = {value = {0, 0, 0, 1}}
(gdb) print perspective_b
$5 = {value = {0, 0, 0, 1}}

the issue goes away when compiling graphene with -O0; any other optimization causes a segmentation fault.

[ebassi]

mmh, cannot reproduce it any more - at least, with -O3.