[Bug target/39821] 120% slowdown with vectorizer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39821

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |target

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The code generation for aarch64 looks fine:
dotproduct_order4:
.LFB1:
        .cfi_startproc
        ldr     q1, [x0]
        ldr     q2, [x1]
        smull   v0.2d, v2.2s, v1.2s
        smlal2  v0.2d, v2.4s, v1.4s
        addp    d0, v0.2d
        fmov    x0, d0
        ret
  vect__6.41_18 = MEM <vector(4) int> [(int32_t *)v1_2(D)];
  vect__10.44_13 = MEM <vector(4) int> [(int32_t *)v2_3(D)];
  vect_patt_25.45_8 = WIDEN_MULT_LO_EXPR <vect__10.44_13, vect__6.41_18>;
  vect_patt_25.45_4 = WIDEN_MULT_HI_EXPR <vect__10.44_13, vect__6.41_18>;
  vect_accum_14.46_31 = vect_patt_25.45_4 + vect_patt_25.45_8;
  _33 = .REDUC_PLUS (vect_accum_14.46_31); [tail call]
---- CUT ----
Even the gimple level for x86_64 looks ok:
  vect__6.41_18 = MEM <vector(4) int> [(int32_t *)v1_2(D)];
  vect__10.44_13 = MEM <vector(4) int> [(int32_t *)v2_3(D)];
  vect_patt_25.45_8 = WIDEN_MULT_LO_EXPR <vect__10.44_13, vect__6.41_18>;
  vect_patt_25.45_4 = WIDEN_MULT_HI_EXPR <vect__10.44_13, vect__6.41_18>;
  vect_accum_14.46_31 = vect_patt_25.45_4 + vect_patt_25.45_8;
  _33 = VEC_PERM_EXPR <vect_accum_14.46_31, { 0, 0 }, { 1, 2 }>;
  _34 = vect_accum_14.46_31 + _33;
  stmp_accum_14.47_35 = BIT_FIELD_REF <_34, 64, 0>;

But the expansion looks bad.