https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98544
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
Or massaging the C++ to produce a single-function testcase (driver still
missing,
I think we can remove the "unrelated" loops as well). What kind of shape (w/o
too much guessing) is the function expecting for its input arrays?
typedef unsigned long size_t;
template<typename T> inline void PM(T &a, T &b, T c, T d)
{ a=c+d; b=c-d; }
template<typename T1, typename T2, typename T3> inline void MULPM
(T1 &a, T1 &b, T2 c, T2 d, T3 e, T3 f)
{ a=c*e+d*f; b=c*f-d*e; }
typedef double T;
void radb2(size_t ido, size_t l1,
const T * __restrict cc, T * __restrict ch,
const T * __restrict wa)
{
auto WA = [wa,ido](size_t x, size_t i) { return wa[i+x*(ido-1)]; };
auto CC = [cc,ido](size_t a, size_t b, size_t c) -> const T&
{ return cc[a+ido*(b+2*c)]; };
auto CH = [ch,ido,l1](size_t a, size_t b, size_t c) -> T&
{ return ch[a+ido*(b+l1*c)]; };
for (size_t k=0; k<l1; k++)
PM (CH(0,k,0),CH(0,k,1),CC(0,0,k),CC(ido-1,1,k));
if ((ido&1)==0)
for (size_t k=0; k<l1; k++)
{
CH(ido-1,k,0) = T( 2)*CC(ido-1,0,k);
CH(ido-1,k,1) = T(-2)*CC(0 ,1,k);
}
if (ido<=2) return;
for (size_t k=0; k<l1;++k)
for (size_t i=2; i<ido; i+=2)
{
size_t ic=ido-i;
T ti2, tr2;
PM (CH(i-1,k,0),tr2,CC(i-1,0,k),CC(ic-1,1,k));
PM (ti2,CH(i ,k,0),CC(i ,0,k),CC(ic ,1,k));
MULPM (CH(i,k,1),CH(i-1,k,1),WA(0,i-2),WA(0,i-1),ti2,tr2);
}
}
