[Bug middle-end/99638] New: s132 benchmarks of TSVC on zen3 benefits from -mno-fma

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99638

            Bug ID: 99638
           Summary: s132 benchmarks of TSVC on zen3 benefits from -mno-fma
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hubicka at gcc dot gnu.org
  Target Milestone: ---

typedef float real_t;

#define iterations 1000000
#define LEN_1D 32000
#define LEN_2D 256
// array definitions
real_t flat_2d_array[LEN_2D*LEN_2D];

real_t x[LEN_1D];

real_t a[LEN_1D],b[LEN_1D],c[LEN_1D],d[LEN_1D],e[LEN_1D],
aa[LEN_2D][LEN_2D],bb[LEN_2D][LEN_2D],cc[LEN_2D][LEN_2D],tt[LEN_2D][LEN_2D];

int indx[LEN_1D];

real_t* __restrict__ xx;
real_t* yy;


// %2.5

void main()
{
//    global data flow analysis
//    loop with multiple dimension ambiguous subscripts

    int m = 0;
    int j = m;
    int k = m+1;
    for (int nl = 0; nl < 400*iterations; nl++) {
        for (int i= 1; i < LEN_2D; i++) {
            aa[j][i] = aa[k][i-1] + b[i] * c[1];
        }
        dummy();
    }
}

compiled with -Ofast -march=native runs 4.4s compared to 4.2s with -Ofast
-march=native -mno-fma