[llvm] r351938 - [ARM] Alter the register allocation order for minsize on Thumb2

[Reid Kleckner via llvm-commits]

I confirmed this change was responsible and reverted it in r351979.

Here is a mostly reduced reproducer. I think this must be some pre-existing
issue that your change is exercising. My first reduction attempt
overreduced the test case so that clang produced the same backend error
even with r351938 reverted.

On Wed, Jan 23, 2019 at 11:54 AM David Green <David.Green at arm.com> wrote:

> > I suspect that this caused the following build error in Chromium
>
>
> OK, thanks for letting me know! I thought this one would be fairly
> harmless.
>
> Let me know when you have a reproducer.
> Dave
>
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typedef __attribute__((neon_vector_type(4))) short b;
typedef __attribute__((neon_vector_type(8))) short c;
typedef __attribute__((neon_vector_type(2))) d;
typedef __attribute__((neon_vector_type(4))) e;
typedef struct {
  c f[2]
} g;
typedef struct {
  e f[2]
} h;
c i(b j, b k) {
  c l = __builtin_shufflevector(j, k, 0, 1, 2, 3, 4, 5, 6, 7);
  return l;
}
b m();
e n(b j, b k) {
  e l = __builtin_neon_vmull_v(j, k, 34);
  return l;
}
g o(c j, c k) {
  g l;
  __builtin_neon_vtrnq_v(&l, j, k, 33);
  return l;
}
g p(e q, e r) {
  c s;
  c u;
  d v;
  g aa;
  e j = q;
  d l = __builtin_shufflevector(j, j, 0, 1);
  {
    e j = r;
    d l = __builtin_shufflevector(j, j, 0, 1);
    v = l;
  }
  {
    b j = l;
    b k = v;
    c l = __builtin_shufflevector(j, k, 0, 1, 2, 3, 4, 5, 6, 7);
    u = l;
  }
  aa.f[0] = u;
  {
    l = __builtin_shufflevector(j, j, 2, 3);
    b j;
    b k = l;
    c l = __builtin_shufflevector(j, k, 0, 1, 2, 3, 4, 5, 6, 7);
    s = l;
  }
  aa.f[1] = s;
  return aa;
}
g ab;
g ac;
e w;
static ad(c *q, c *r, c *ae, c *af, c *ag, c *ah, c *ai, c *aj) {
  h ak;
  e al;
  e am;
  h an;
  e ao;
  e ap;
  h aq;
  e ar;
  e as;
  h at;
  e au;
  e av;
  g aa = ab;
  g aw = o(*ae, *af);
  g ax = o(*ag, *ah);
  g ay = o(*ai, *aj);
  e l;
  av = aa.f[0];
  l = aw.f[0];
  au = l;
  {
    h l;
    __builtin_neon_vtrnq_v(&l, av, au, 34);
    at = l;
  }
  h az = at;
  {
    as = aa.f[1];
    l = aw.f[1];
    ar = l;
    h l;
    __builtin_neon_vtrnq_v(&l, as, ar, 34);
    aq = l;
  }
  h ba = aq;
  {
    ap = ay.f[0];
    ao = ax.f[0];
    h l;
    __builtin_neon_vtrnq_v(&l, ap, ao, 34);
    an = l;
  }
  h bb = an;
  {
    am = ax.f[1];
    h l;
    __builtin_neon_vtrnq_v(&l, am, al, 34);
    ak = l;
  }
  h bc = ak;
  g bd = p(az.f[0], bb.f[0]);
  g be = p(ba.f[0], bc.f[0]);
  g bf = ac;
  g bg = p(ba.f[1], w);
  *q = bd.f[0];
  *r = be.f[0];
  *ag = bd.f[1];
  *ah = be.f[1];
  *ai = bf.f[1];
  *aj = bg.f[1];
}
c bh(e *bi) {
  return i(({ __builtin_neon_vrshrn_n_v(bi[0], 14, 1); }),
           ({ __builtin_neon_vrshrn_n_v(bi[1], 14, 1); }));
}
bj(e *bk, c *bd, c *be) {
  c x;
  e *bi = bk;
  x = i(({ __builtin_neon_vrshrn_n_v(bi[0], 14, 1); }),
        ({ __builtin_neon_vrshrn_n_v(bi[1], 14, 1); }));
  *bd = x;
  *be = bh(bk + 2);
}
static bl(b bm, b bn, c *bo) {
  e y;
  c bp;
  c br;
  c bt;
  c bu;
  b bx;
  c bz[1];
  c ca;
  c cb;
  c cc;
  c cd;
  c ce;
  c cf;
  e bk[8];
  c j = bo[1];
  b l = __builtin_shufflevector(j, j, 0, 1, 2, 3);
  bx = l = __builtin_shufflevector(j, j, 4, 5, 6, 7);
  bk[0] = ({
    b cg = bx;
    b ch = bn;
    n(cg, __builtin_shufflevector(ch, ch, 3, 3, 3, 3));
  });
  bk[1] = ({
    b cg;
    b ch = bn;
    n(cg, __builtin_shufflevector(ch, ch, 3, 3, 3, 3));
  });
  bk[2] = ({
    b cg;
    b ch = bn;
    n(cg, __builtin_shufflevector(ch, ch, 2, 2, 2, 2));
  });
  bk[3] = ({
    b cg;
    b ch;
    e l = __builtin_neon_vmull_v(cg, ch, 34);
    l;
  });
  bk[4] = ({
    b cg;
    b ch = bn;
    n(cg, __builtin_shufflevector(ch, ch, 1, 1, 1, 1));
  });
  bk[5] = ({
    b cg;
    b ch = bn;
    n(cg, __builtin_shufflevector(ch, ch, 1, 1, 1, 1));
  });
  bk[6] = ({
    b cg = bx;
    b ch = bn;
    n(cg, __builtin_shufflevector(ch, ch, 0, 0, 0, 0));
  });
  bk[7] = ({
    b ch;
    n(l, ch);
  });
  bk[2] = ({
    e cg = bk[2];
    b ch;
    b ci = bn;
    cg + n(ch, __builtin_shufflevector(ci, ci, 1, 1, 1, 1));
  });
  bj(bk, &cf, &ce);
  bk[2] = ({
    b cg;
    b ch = bm;
    n(cg, __builtin_shufflevector(ch, ch, 2, 2, 2, 2));
  });
  bk[3] = ({
    b cg;
    b ch = bm;
    n(cg, __builtin_shufflevector(ch, ch, 2, 2, 2, 2));
  });
  bk[6] = ({
    e cg = bk[6];
    b ch;
    b ci = bm;
    cg + n(ch, __builtin_shufflevector(ci, ci, 3, 3, 3, 3));
  });
  bk[7] = ({
    e cg = bk[7];
    b ch;
    b ci = bm;
    cg + n(ch, __builtin_shufflevector(ci, ci, 3, 3, 3, 3));
  });
  bj(bk, bz, &cd);
  bj(&bk[4], &cc, &cb);
  {
    c l = cf + ce;
    bu = l;
    l = cd + cc;
    bt = l;
  }
  bk[3] = ({
    e cg = bk[3];
    b ch;
    b ci = bm;
    cg + n(ch, __builtin_shufflevector(ci, ci, 2, 2, 2, 2));
  });
  bj(bk, &ce, &ca);
  {
    c l = bt + ca;
    br = l;
  }
  bo[1] = br;
  bo[2] = ce;
  {
    c l = cb + bu;
    bp = l;
  }
  bo[3] = bp;
}
static cj(b bm, b bn, c *bo) {
  ad(&bo[0], &bo[1], &bo[2], &bo[3], &bo[4], &bo[5], &bo[6], &bo[7]);
  bl(bm, bn, bo);
}
cl() {
  b bm = m();
  b bn = m();
  c a[1];
  cj(bm, bn, a);
  cj(bm, bn, a);
}
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