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From: "juzhe.zhong at rivai dot ai" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/106989] New: GCC fail to vectorize and clang succeed
Date: Tue, 20 Sep 2022 23:05:36 +0000
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X-Bugzilla-Version: 13.0
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X-Bugzilla-Who: juzhe.zhong at rivai dot ai
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106989

            Bug ID: 106989
           Summary: GCC fail to vectorize and clang succeed
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: juzhe.zhong at rivai dot ai
  Target Milestone: ---

https://godbolt.org/z/v5arbjh3n

This case ARM-clang can vectorize but ARM-GCC failed.
Can anyone fix it? Or give me some guideline to fix it?


code:
typedef float real_t;

#define iterations 100000
#define LEN_1D 32000
#define LEN_2D 256
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],
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;
real_t s243(void)
{
    for (int nl =3D 0; nl < iterations; nl++) {
        for (int i =3D 0; i < LEN_1D-1; i++) {
            a[i] =3D b[i] + c[i  ] * d[i];
            b[i] =3D a[i] + d[i  ] * e[i];
            a[i] =3D b[i] + a[i+1] * d[i];
        }
    }
}=