[Bug tree-optimization/98544] [11 regression] Wrong code generated by tree vectorizer since r11-3917-g28290cb50c7dbf87

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98544

--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
So at least the following doesn't produce any different answers for me
comparing -O -ftree-loop-vectorize -mavx to -O0

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 __attribute__((noipa))
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)
    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);
      }
}

int main()
{
  double *cc, *ch, *wa;
  cc = new double[8*8*8];
  ch = new double[8*8*8];
  wa = new double[8*8*8];
  for (size_t i = 0; i < 8*8*8; ++i)
    cc[i] = i;
  for (size_t i = 0; i < 8*8*8; ++i)
    ch[i] = i + 0.25;
  for (size_t i = 0; i < 8*8*8; ++i)
    wa[i] = i - 0.5;
  radb2 (8, 8, cc, ch, wa);
  for (size_t i = 0; i < 8*8*8; ++i)
    __builtin_printf ("%f %f %f\n", cc[i], ch[i], wa[i]);
  return 0;
}