[v2] Strip of a vector load which is only used partially.

Message ID 20220509051112.80162-1-hongtao.liu@intel.com
State New
Headers
Series [v2] Strip of a vector load which is only used partially. |

Commit Message

Liu, Hongtao May 9, 2022, 5:11 a.m. UTC
  Here's adjused patch.
Ok for trunk?

Optimize

  _4 = VEC_PERM_EXPR <_1, _1, { 4, 5, 6, 7, 4, 5, 6, 7 }>;
  _5 = BIT_FIELD_REF <_4, 128, 0>;

to

  _5 = BIT_FIELD_REF <_1, 128, 128>;

gcc/ChangeLog:

	PR tree-optimization/102583
	* tree-ssa-forwprop.cc (simplify_bitfield_ref): Extended to a
	contiguous stride in the VEC_PERM_EXPR.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr102583.c: New test.
	* gcc.target/i386/pr92645-2.c: Adjust testcase.
	* gcc.target/i386/pr92645-3.c: Ditto.
---
 gcc/testsuite/gcc.target/i386/pr102583.c  | 30 ++++++++
 gcc/testsuite/gcc.target/i386/pr92645-2.c |  4 +-
 gcc/testsuite/gcc.target/i386/pr92645-3.c |  4 +-
 gcc/tree-ssa-forwprop.cc                  | 89 ++++++++++++++++-------
 4 files changed, 96 insertions(+), 31 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr102583.c
  

Comments

Richard Biener May 10, 2022, 6:53 a.m. UTC | #1
On Mon, May 9, 2022 at 7:11 AM liuhongt via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Here's adjused patch.
> Ok for trunk?
>
> Optimize
>
>   _4 = VEC_PERM_EXPR <_1, _1, { 4, 5, 6, 7, 4, 5, 6, 7 }>;
>   _5 = BIT_FIELD_REF <_4, 128, 0>;
>
> to
>
>   _5 = BIT_FIELD_REF <_1, 128, 128>;
>
> gcc/ChangeLog:
>
>         PR tree-optimization/102583
>         * tree-ssa-forwprop.cc (simplify_bitfield_ref): Extended to a
>         contiguous stride in the VEC_PERM_EXPR.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/pr102583.c: New test.
>         * gcc.target/i386/pr92645-2.c: Adjust testcase.
>         * gcc.target/i386/pr92645-3.c: Ditto.
> ---
>  gcc/testsuite/gcc.target/i386/pr102583.c  | 30 ++++++++
>  gcc/testsuite/gcc.target/i386/pr92645-2.c |  4 +-
>  gcc/testsuite/gcc.target/i386/pr92645-3.c |  4 +-
>  gcc/tree-ssa-forwprop.cc                  | 89 ++++++++++++++++-------
>  4 files changed, 96 insertions(+), 31 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr102583.c
>
> diff --git a/gcc/testsuite/gcc.target/i386/pr102583.c b/gcc/testsuite/gcc.target/i386/pr102583.c
> new file mode 100644
> index 00000000000..4ef2f296d0c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr102583.c
> @@ -0,0 +1,30 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mavx512f -O2" } */
> +/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+32\(%.*%ymm} 1 } } */
> +/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+16\(%.*%xmm} 1 } } */
> +/* { dg-final { scan-assembler-times {(?n)vmovq[ \t]+16\(%.*%xmm} 1 { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not {(?n)vpermd[ \t]+.*%zmm} } } */
> +
> +typedef int v16si __attribute__((vector_size(64)));
> +typedef float v8sf __attribute__((vector_size(32)));
> +typedef float v4sf __attribute__((vector_size(16)));
> +typedef float v2sf __attribute__((vector_size(8)));
> +
> +v8sf part (v16si *srcp)
> +{
> +  v16si src = *srcp;
> +  return (v8sf) { (float)src[8], (float) src[9], (float)src[10], (float)src[11],
> +      (float)src[12], (float)src[13], (float)src[14], (float)src[15] };
> +}
> +
> +v4sf part1 (v16si *srcp)
> +{
> +  v16si src = *srcp;
> +  return (v4sf) { (float)src[4], (float)src[5], (float)src[6], (float)src[7] };
> +}
> +
> +v2sf part2 (v16si *srcp)
> +{
> +  v16si src = *srcp;
> +  return (v2sf) { (float)src[4], (float)src[5] };
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr92645-2.c b/gcc/testsuite/gcc.target/i386/pr92645-2.c
> index d34ed3aa8e5..f0608de938a 100644
> --- a/gcc/testsuite/gcc.target/i386/pr92645-2.c
> +++ b/gcc/testsuite/gcc.target/i386/pr92645-2.c
> @@ -29,6 +29,6 @@ void odd (v2si *dst, v4si *srcp)
>  }
>
>  /* { dg-final { scan-tree-dump-times "BIT_FIELD_REF" 4 "cddce1" } } */
> -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
> +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
>  /* Ideally highpart extraction would elide the permutation as well.  */
> -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
> +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr92645-3.c b/gcc/testsuite/gcc.target/i386/pr92645-3.c
> index 9c08c9fb632..691011195c9 100644
> --- a/gcc/testsuite/gcc.target/i386/pr92645-3.c
> +++ b/gcc/testsuite/gcc.target/i386/pr92645-3.c
> @@ -32,6 +32,6 @@ void odd (v4sf *dst, v8si *srcp)
>  /* Four conversions, on the smaller vector type, to not convert excess
>     elements.  */
>  /* { dg-final { scan-tree-dump-times " = \\\(vector\\\(4\\\) float\\\)" 4 "cddce1" } } */
> -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
> +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
>  /* Ideally highpart extraction would elide the VEC_PERM_EXPR as well.  */
> -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
> +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
> diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> index 484491fa1c5..f91f738895d 100644
> --- a/gcc/tree-ssa-forwprop.cc
> +++ b/gcc/tree-ssa-forwprop.cc
> @@ -2334,8 +2334,10 @@ simplify_bitfield_ref (gimple_stmt_iterator *gsi)
>    gimple *stmt = gsi_stmt (*gsi);
>    gimple *def_stmt;
>    tree op, op0, op1;
> -  tree elem_type;
> -  unsigned idx, size;
> +  tree elem_type, type;
> +  tree p, m, tem;
> +  unsigned HOST_WIDE_INT nelts;
> +  unsigned idx, size, elem_size;
>    enum tree_code code;
>
>    op = gimple_assign_rhs1 (stmt);
> @@ -2353,42 +2355,75 @@ simplify_bitfield_ref (gimple_stmt_iterator *gsi)
>    op1 = TREE_OPERAND (op, 1);
>    code = gimple_assign_rhs_code (def_stmt);
>    elem_type = TREE_TYPE (TREE_TYPE (op0));
> -  if (TREE_TYPE (op) != elem_type)
> +  type = TREE_TYPE (op);
> +  /* Also hanlde vector type.
> +   .i.e.
> +   _7 = VEC_PERM_EXPR <_1, _1, { 2, 3, 2, 3 }>;
> +   _11 = BIT_FIELD_REF <_7, 64, 0>;
> +
> +   to
> +
> +   _11 = BIT_FIELD_REF <_1, 64, 64>.  */
> +  if (type != elem_type
> +      && (!VECTOR_TYPE_P (type) || TREE_TYPE (type) != elem_type))
>      return false;

I'm not sure we actually need this check.  I think we could handle
a __int128_t extract from the permuted vector as well, no?

>
> -  size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
> +  elem_size = size = TREE_INT_CST_LOW (TYPE_SIZE (type));

That's not going to work with VLA vectors, I think you need to make
elem_size/size poly_uint64 and use tree_to_poly_uint64 (TYPE_SIZE (type))
here.

>    if (maybe_ne (bit_field_size (op), size))
>      return false;
>
> -  if (code == VEC_PERM_EXPR
> -      && constant_multiple_p (bit_field_offset (op), size, &idx))
> +  if (code != VEC_PERM_EXPR
> +      || !constant_multiple_p (bit_field_offset (op), size, &idx))

That might be a bit restrictive?  I think we want elem_size here
with elem_size picked from the vector type of the VEC_PERM_EXPR
operand.

> +    return false;
> +
> +  m = gimple_assign_rhs3 (def_stmt);
> +  if (TREE_CODE (m) != VECTOR_CST
> +      || !VECTOR_CST_NELTS (m).is_constant (&nelts))
> +    return false;
> +
> +  /* One element.  */
> +  if (type == elem_type)

I think this should work on the sizes, so

      if (known_eq (size, elem_size))
...

that makes sure we do not end up with nelts_op == 1 below and also
handle the case where the BIT_FIELD_REF would do int<->float
punning.

> +    idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
> +  else
>      {
> -      tree p, m, tem;
> -      unsigned HOST_WIDE_INT nelts;
> -      m = gimple_assign_rhs3 (def_stmt);
> -      if (TREE_CODE (m) != VECTOR_CST
> -         || !VECTOR_CST_NELTS (m).is_constant (&nelts))
> +      elem_size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
> +      unsigned nelts_op;
> +      if (!constant_multiple_p (bit_field_size (op), elem_size, &nelts_op))

bit_field_size (op) == size?  I think we also want to handle
power-of-two nelts_op
only (I can't think of how we get a non-power-of-two, but checking
pow2p_hwi (nelts_op)
woudl be nice if only for documentation purposes)

>         return false;
> -      idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
> -      idx %= 2 * nelts;
> -      if (idx < nelts)
> -       {
> -         p = gimple_assign_rhs1 (def_stmt);
> -       }
> -      else
> +      unsigned start = TREE_INT_CST_LOW (vector_cst_elt (m, idx));
> +      unsigned end = TREE_INT_CST_LOW (vector_cst_elt (m, idx + nelts_op - 1));
> +      /* Be in the same vector.  */
> +      if ((start < nelts) != (end < nelts))
> +       return false;
> +      for (unsigned HOST_WIDE_INT i = 1; i != nelts_op; i++)
>         {
> -         p = gimple_assign_rhs2 (def_stmt);
> -         idx -= nelts;
> +         /* Continuous area.  */
> +         if (TREE_INT_CST_LOW (vector_cst_elt (m, idx + i)) - 1
> +             != TREE_INT_CST_LOW (vector_cst_elt (m, idx + i - 1)))
> +           return false;
>         }
> -      tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
> -                   unshare_expr (p), op1, bitsize_int (idx * size));
> -      gimple_assign_set_rhs1 (stmt, tem);
> -      fold_stmt (gsi);
> -      update_stmt (gsi_stmt (*gsi));
> -      return true;
> +      /* Alignment not worse than before.  */
> +      unsigned dest_align = TREE_INT_CST_LOW (TYPE_SIZE (type));
> +      if (start * elem_size % dest_align)
> +       return false;

So I think we want to have start * elem_size be a multiple of size
(the check I said above is too restrictive on the _original_ bit-field-ref but
we want to have for the target bit-field-ref).  I think that's what you check
here but see above for the use of poly-ints.

> +      idx = start;
>      }
>
> -  return false;
> +  idx %= 2 * nelts;

that's odd - why do you need to clamp idx?

> +  if (idx < nelts)
> +    p = gimple_assign_rhs1 (def_stmt);
> +  else
> +    {
> +      p = gimple_assign_rhs2 (def_stmt);
> +      idx -= nelts;
> +    }
> +
> +  tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
> +               unshare_expr (p), op1, bitsize_int (idx * elem_size));

You don't need to unshare_expr 'p' here.

Otherwise looks OK.

Thanks,
Richard.

> +  gimple_assign_set_rhs1 (stmt, tem);
> +  fold_stmt (gsi);
> +  update_stmt (gsi_stmt (*gsi));
> +  return true;
>  }
>
>  /* Determine whether applying the 2 permutations (mask1 then mask2)
> --
> 2.18.1
>
  
Hongtao Liu May 12, 2022, 1:48 a.m. UTC | #2
On Tue, May 10, 2022 at 2:54 PM Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Mon, May 9, 2022 at 7:11 AM liuhongt via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Here's adjused patch.
> > Ok for trunk?
> >
> > Optimize
> >
> >   _4 = VEC_PERM_EXPR <_1, _1, { 4, 5, 6, 7, 4, 5, 6, 7 }>;
> >   _5 = BIT_FIELD_REF <_4, 128, 0>;
> >
> > to
> >
> >   _5 = BIT_FIELD_REF <_1, 128, 128>;
> >
> > gcc/ChangeLog:
> >
> >         PR tree-optimization/102583
> >         * tree-ssa-forwprop.cc (simplify_bitfield_ref): Extended to a
> >         contiguous stride in the VEC_PERM_EXPR.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.target/i386/pr102583.c: New test.
> >         * gcc.target/i386/pr92645-2.c: Adjust testcase.
> >         * gcc.target/i386/pr92645-3.c: Ditto.
> > ---
> >  gcc/testsuite/gcc.target/i386/pr102583.c  | 30 ++++++++
> >  gcc/testsuite/gcc.target/i386/pr92645-2.c |  4 +-
> >  gcc/testsuite/gcc.target/i386/pr92645-3.c |  4 +-
> >  gcc/tree-ssa-forwprop.cc                  | 89 ++++++++++++++++-------
> >  4 files changed, 96 insertions(+), 31 deletions(-)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr102583.c
> >
> > diff --git a/gcc/testsuite/gcc.target/i386/pr102583.c b/gcc/testsuite/gcc.target/i386/pr102583.c
> > new file mode 100644
> > index 00000000000..4ef2f296d0c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr102583.c
> > @@ -0,0 +1,30 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-mavx512f -O2" } */
> > +/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+32\(%.*%ymm} 1 } } */
> > +/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+16\(%.*%xmm} 1 } } */
> > +/* { dg-final { scan-assembler-times {(?n)vmovq[ \t]+16\(%.*%xmm} 1 { target { ! ia32 } } } } */
> > +/* { dg-final { scan-assembler-not {(?n)vpermd[ \t]+.*%zmm} } } */
> > +
> > +typedef int v16si __attribute__((vector_size(64)));
> > +typedef float v8sf __attribute__((vector_size(32)));
> > +typedef float v4sf __attribute__((vector_size(16)));
> > +typedef float v2sf __attribute__((vector_size(8)));
> > +
> > +v8sf part (v16si *srcp)
> > +{
> > +  v16si src = *srcp;
> > +  return (v8sf) { (float)src[8], (float) src[9], (float)src[10], (float)src[11],
> > +      (float)src[12], (float)src[13], (float)src[14], (float)src[15] };
> > +}
> > +
> > +v4sf part1 (v16si *srcp)
> > +{
> > +  v16si src = *srcp;
> > +  return (v4sf) { (float)src[4], (float)src[5], (float)src[6], (float)src[7] };
> > +}
> > +
> > +v2sf part2 (v16si *srcp)
> > +{
> > +  v16si src = *srcp;
> > +  return (v2sf) { (float)src[4], (float)src[5] };
> > +}
> > diff --git a/gcc/testsuite/gcc.target/i386/pr92645-2.c b/gcc/testsuite/gcc.target/i386/pr92645-2.c
> > index d34ed3aa8e5..f0608de938a 100644
> > --- a/gcc/testsuite/gcc.target/i386/pr92645-2.c
> > +++ b/gcc/testsuite/gcc.target/i386/pr92645-2.c
> > @@ -29,6 +29,6 @@ void odd (v2si *dst, v4si *srcp)
> >  }
> >
> >  /* { dg-final { scan-tree-dump-times "BIT_FIELD_REF" 4 "cddce1" } } */
> > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
> > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
> >  /* Ideally highpart extraction would elide the permutation as well.  */
> > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
> > diff --git a/gcc/testsuite/gcc.target/i386/pr92645-3.c b/gcc/testsuite/gcc.target/i386/pr92645-3.c
> > index 9c08c9fb632..691011195c9 100644
> > --- a/gcc/testsuite/gcc.target/i386/pr92645-3.c
> > +++ b/gcc/testsuite/gcc.target/i386/pr92645-3.c
> > @@ -32,6 +32,6 @@ void odd (v4sf *dst, v8si *srcp)
> >  /* Four conversions, on the smaller vector type, to not convert excess
> >     elements.  */
> >  /* { dg-final { scan-tree-dump-times " = \\\(vector\\\(4\\\) float\\\)" 4 "cddce1" } } */
> > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
> > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
> >  /* Ideally highpart extraction would elide the VEC_PERM_EXPR as well.  */
> > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
> > diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> > index 484491fa1c5..f91f738895d 100644
> > --- a/gcc/tree-ssa-forwprop.cc
> > +++ b/gcc/tree-ssa-forwprop.cc
> > @@ -2334,8 +2334,10 @@ simplify_bitfield_ref (gimple_stmt_iterator *gsi)
> >    gimple *stmt = gsi_stmt (*gsi);
> >    gimple *def_stmt;
> >    tree op, op0, op1;
> > -  tree elem_type;
> > -  unsigned idx, size;
> > +  tree elem_type, type;
> > +  tree p, m, tem;
> > +  unsigned HOST_WIDE_INT nelts;
> > +  unsigned idx, size, elem_size;
> >    enum tree_code code;
> >
> >    op = gimple_assign_rhs1 (stmt);
> > @@ -2353,42 +2355,75 @@ simplify_bitfield_ref (gimple_stmt_iterator *gsi)
> >    op1 = TREE_OPERAND (op, 1);
> >    code = gimple_assign_rhs_code (def_stmt);
> >    elem_type = TREE_TYPE (TREE_TYPE (op0));
> > -  if (TREE_TYPE (op) != elem_type)
> > +  type = TREE_TYPE (op);
> > +  /* Also hanlde vector type.
> > +   .i.e.
> > +   _7 = VEC_PERM_EXPR <_1, _1, { 2, 3, 2, 3 }>;
> > +   _11 = BIT_FIELD_REF <_7, 64, 0>;
> > +
> > +   to
> > +
> > +   _11 = BIT_FIELD_REF <_1, 64, 64>.  */
> > +  if (type != elem_type
> > +      && (!VECTOR_TYPE_P (type) || TREE_TYPE (type) != elem_type))
> >      return false;
>
> I'm not sure we actually need this check.  I think we could handle
> a __int128_t extract from the permuted vector as well, no?
Yes, changed.
>
> >
> > -  size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
> > +  elem_size = size = TREE_INT_CST_LOW (TYPE_SIZE (type));
>
> That's not going to work with VLA vectors, I think you need to make
> elem_size/size poly_uint64 and use tree_to_poly_uint64 (TYPE_SIZE (type))
> here.
>
Changed.
> >    if (maybe_ne (bit_field_size (op), size))
> >      return false;
> >
> > -  if (code == VEC_PERM_EXPR
> > -      && constant_multiple_p (bit_field_offset (op), size, &idx))
> > +  if (code != VEC_PERM_EXPR
> > +      || !constant_multiple_p (bit_field_offset (op), size, &idx))
>
> That might be a bit restrictive?  I think we want elem_size here
> with elem_size picked from the vector type of the VEC_PERM_EXPR
> operand.
>
Changed.
> > +    return false;
> > +
> > +  m = gimple_assign_rhs3 (def_stmt);
> > +  if (TREE_CODE (m) != VECTOR_CST
> > +      || !VECTOR_CST_NELTS (m).is_constant (&nelts))
> > +    return false;
> > +
> > +  /* One element.  */
> > +  if (type == elem_type)
>
> I think this should work on the sizes, so
>
>       if (known_eq (size, elem_size))
> ...
>
> that makes sure we do not end up with nelts_op == 1 below and also
> handle the case where the BIT_FIELD_REF would do int<->float
> punning.
>
Yes, also for V1TImode <-> TImode punning.
> > +    idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
> > +  else
> >      {
> > -      tree p, m, tem;
> > -      unsigned HOST_WIDE_INT nelts;
> > -      m = gimple_assign_rhs3 (def_stmt);
> > -      if (TREE_CODE (m) != VECTOR_CST
> > -         || !VECTOR_CST_NELTS (m).is_constant (&nelts))
> > +      elem_size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
> > +      unsigned nelts_op;
> > +      if (!constant_multiple_p (bit_field_size (op), elem_size, &nelts_op))
>
> bit_field_size (op) == size?  I think we also want to handle
> power-of-two nelts_op
> only (I can't think of how we get a non-power-of-two, but checking
> pow2p_hwi (nelts_op)
> woudl be nice if only for documentation purposes)
Add the check.
>
> >         return false;
> > -      idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
> > -      idx %= 2 * nelts;
> > -      if (idx < nelts)
> > -       {
> > -         p = gimple_assign_rhs1 (def_stmt);
> > -       }
> > -      else
> > +      unsigned start = TREE_INT_CST_LOW (vector_cst_elt (m, idx));
> > +      unsigned end = TREE_INT_CST_LOW (vector_cst_elt (m, idx + nelts_op - 1));
> > +      /* Be in the same vector.  */
> > +      if ((start < nelts) != (end < nelts))
> > +       return false;
> > +      for (unsigned HOST_WIDE_INT i = 1; i != nelts_op; i++)
> >         {
> > -         p = gimple_assign_rhs2 (def_stmt);
> > -         idx -= nelts;
> > +         /* Continuous area.  */
> > +         if (TREE_INT_CST_LOW (vector_cst_elt (m, idx + i)) - 1
> > +             != TREE_INT_CST_LOW (vector_cst_elt (m, idx + i - 1)))
> > +           return false;
> >         }
> > -      tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
> > -                   unshare_expr (p), op1, bitsize_int (idx * size));
> > -      gimple_assign_set_rhs1 (stmt, tem);
> > -      fold_stmt (gsi);
> > -      update_stmt (gsi_stmt (*gsi));
> > -      return true;
> > +      /* Alignment not worse than before.  */
> > +      unsigned dest_align = TREE_INT_CST_LOW (TYPE_SIZE (type));
> > +      if (start * elem_size % dest_align)
> > +       return false;
>
> So I think we want to have start * elem_size be a multiple of size
> (the check I said above is too restrictive on the _original_ bit-field-ref but
> we want to have for the target bit-field-ref).  I think that's what you check
> here but see above for the use of poly-ints.
Changed.
>
> > +      idx = start;
> >      }
> >
> > -  return false;
> > +  idx %= 2 * nelts;
>
> that's odd - why do you need to clamp idx?
Changed.
This is just copy from original codes, it looks it's not needed any
more, similar for your below comment.
>
> > +  if (idx < nelts)
> > +    p = gimple_assign_rhs1 (def_stmt);
> > +  else
> > +    {
> > +      p = gimple_assign_rhs2 (def_stmt);
> > +      idx -= nelts;
> > +    }
> > +
> > +  tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
> > +               unshare_expr (p), op1, bitsize_int (idx * elem_size));
>
> You don't need to unshare_expr 'p' here.
>
> Otherwise looks OK.
>
Here's updated patch.
> Thanks,
> Richard.
>
> > +  gimple_assign_set_rhs1 (stmt, tem);
> > +  fold_stmt (gsi);
> > +  update_stmt (gsi_stmt (*gsi));
> > +  return true;
> >  }
> >
> >  /* Determine whether applying the 2 permutations (mask1 then mask2)
> > --
> > 2.18.1
> >
  
Richard Biener May 12, 2022, 11:26 a.m. UTC | #3
On Thu, May 12, 2022 at 3:48 AM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Tue, May 10, 2022 at 2:54 PM Richard Biener via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Mon, May 9, 2022 at 7:11 AM liuhongt via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > Here's adjused patch.
> > > Ok for trunk?
> > >
> > > Optimize
> > >
> > >   _4 = VEC_PERM_EXPR <_1, _1, { 4, 5, 6, 7, 4, 5, 6, 7 }>;
> > >   _5 = BIT_FIELD_REF <_4, 128, 0>;
> > >
> > > to
> > >
> > >   _5 = BIT_FIELD_REF <_1, 128, 128>;
> > >
> > > gcc/ChangeLog:
> > >
> > >         PR tree-optimization/102583
> > >         * tree-ssa-forwprop.cc (simplify_bitfield_ref): Extended to a
> > >         contiguous stride in the VEC_PERM_EXPR.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > >         * gcc.target/i386/pr102583.c: New test.
> > >         * gcc.target/i386/pr92645-2.c: Adjust testcase.
> > >         * gcc.target/i386/pr92645-3.c: Ditto.
> > > ---
> > >  gcc/testsuite/gcc.target/i386/pr102583.c  | 30 ++++++++
> > >  gcc/testsuite/gcc.target/i386/pr92645-2.c |  4 +-
> > >  gcc/testsuite/gcc.target/i386/pr92645-3.c |  4 +-
> > >  gcc/tree-ssa-forwprop.cc                  | 89 ++++++++++++++++-------
> > >  4 files changed, 96 insertions(+), 31 deletions(-)
> > >  create mode 100644 gcc/testsuite/gcc.target/i386/pr102583.c
> > >
> > > diff --git a/gcc/testsuite/gcc.target/i386/pr102583.c b/gcc/testsuite/gcc.target/i386/pr102583.c
> > > new file mode 100644
> > > index 00000000000..4ef2f296d0c
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/pr102583.c
> > > @@ -0,0 +1,30 @@
> > > +/* { dg-do compile } */
> > > +/* { dg-options "-mavx512f -O2" } */
> > > +/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+32\(%.*%ymm} 1 } } */
> > > +/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+16\(%.*%xmm} 1 } } */
> > > +/* { dg-final { scan-assembler-times {(?n)vmovq[ \t]+16\(%.*%xmm} 1 { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler-not {(?n)vpermd[ \t]+.*%zmm} } } */
> > > +
> > > +typedef int v16si __attribute__((vector_size(64)));
> > > +typedef float v8sf __attribute__((vector_size(32)));
> > > +typedef float v4sf __attribute__((vector_size(16)));
> > > +typedef float v2sf __attribute__((vector_size(8)));
> > > +
> > > +v8sf part (v16si *srcp)
> > > +{
> > > +  v16si src = *srcp;
> > > +  return (v8sf) { (float)src[8], (float) src[9], (float)src[10], (float)src[11],
> > > +      (float)src[12], (float)src[13], (float)src[14], (float)src[15] };
> > > +}
> > > +
> > > +v4sf part1 (v16si *srcp)
> > > +{
> > > +  v16si src = *srcp;
> > > +  return (v4sf) { (float)src[4], (float)src[5], (float)src[6], (float)src[7] };
> > > +}
> > > +
> > > +v2sf part2 (v16si *srcp)
> > > +{
> > > +  v16si src = *srcp;
> > > +  return (v2sf) { (float)src[4], (float)src[5] };
> > > +}
> > > diff --git a/gcc/testsuite/gcc.target/i386/pr92645-2.c b/gcc/testsuite/gcc.target/i386/pr92645-2.c
> > > index d34ed3aa8e5..f0608de938a 100644
> > > --- a/gcc/testsuite/gcc.target/i386/pr92645-2.c
> > > +++ b/gcc/testsuite/gcc.target/i386/pr92645-2.c
> > > @@ -29,6 +29,6 @@ void odd (v2si *dst, v4si *srcp)
> > >  }
> > >
> > >  /* { dg-final { scan-tree-dump-times "BIT_FIELD_REF" 4 "cddce1" } } */
> > > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
> > > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
> > >  /* Ideally highpart extraction would elide the permutation as well.  */
> > > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
> > > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/pr92645-3.c b/gcc/testsuite/gcc.target/i386/pr92645-3.c
> > > index 9c08c9fb632..691011195c9 100644
> > > --- a/gcc/testsuite/gcc.target/i386/pr92645-3.c
> > > +++ b/gcc/testsuite/gcc.target/i386/pr92645-3.c
> > > @@ -32,6 +32,6 @@ void odd (v4sf *dst, v8si *srcp)
> > >  /* Four conversions, on the smaller vector type, to not convert excess
> > >     elements.  */
> > >  /* { dg-final { scan-tree-dump-times " = \\\(vector\\\(4\\\) float\\\)" 4 "cddce1" } } */
> > > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
> > > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
> > >  /* Ideally highpart extraction would elide the VEC_PERM_EXPR as well.  */
> > > -/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
> > > +/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
> > > diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> > > index 484491fa1c5..f91f738895d 100644
> > > --- a/gcc/tree-ssa-forwprop.cc
> > > +++ b/gcc/tree-ssa-forwprop.cc
> > > @@ -2334,8 +2334,10 @@ simplify_bitfield_ref (gimple_stmt_iterator *gsi)
> > >    gimple *stmt = gsi_stmt (*gsi);
> > >    gimple *def_stmt;
> > >    tree op, op0, op1;
> > > -  tree elem_type;
> > > -  unsigned idx, size;
> > > +  tree elem_type, type;
> > > +  tree p, m, tem;
> > > +  unsigned HOST_WIDE_INT nelts;
> > > +  unsigned idx, size, elem_size;
> > >    enum tree_code code;
> > >
> > >    op = gimple_assign_rhs1 (stmt);
> > > @@ -2353,42 +2355,75 @@ simplify_bitfield_ref (gimple_stmt_iterator *gsi)
> > >    op1 = TREE_OPERAND (op, 1);
> > >    code = gimple_assign_rhs_code (def_stmt);
> > >    elem_type = TREE_TYPE (TREE_TYPE (op0));
> > > -  if (TREE_TYPE (op) != elem_type)
> > > +  type = TREE_TYPE (op);
> > > +  /* Also hanlde vector type.
> > > +   .i.e.
> > > +   _7 = VEC_PERM_EXPR <_1, _1, { 2, 3, 2, 3 }>;
> > > +   _11 = BIT_FIELD_REF <_7, 64, 0>;
> > > +
> > > +   to
> > > +
> > > +   _11 = BIT_FIELD_REF <_1, 64, 64>.  */
> > > +  if (type != elem_type
> > > +      && (!VECTOR_TYPE_P (type) || TREE_TYPE (type) != elem_type))
> > >      return false;
> >
> > I'm not sure we actually need this check.  I think we could handle
> > a __int128_t extract from the permuted vector as well, no?
> Yes, changed.
> >
> > >
> > > -  size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
> > > +  elem_size = size = TREE_INT_CST_LOW (TYPE_SIZE (type));
> >
> > That's not going to work with VLA vectors, I think you need to make
> > elem_size/size poly_uint64 and use tree_to_poly_uint64 (TYPE_SIZE (type))
> > here.
> >
> Changed.
> > >    if (maybe_ne (bit_field_size (op), size))
> > >      return false;
> > >
> > > -  if (code == VEC_PERM_EXPR
> > > -      && constant_multiple_p (bit_field_offset (op), size, &idx))
> > > +  if (code != VEC_PERM_EXPR
> > > +      || !constant_multiple_p (bit_field_offset (op), size, &idx))
> >
> > That might be a bit restrictive?  I think we want elem_size here
> > with elem_size picked from the vector type of the VEC_PERM_EXPR
> > operand.
> >
> Changed.
> > > +    return false;
> > > +
> > > +  m = gimple_assign_rhs3 (def_stmt);
> > > +  if (TREE_CODE (m) != VECTOR_CST
> > > +      || !VECTOR_CST_NELTS (m).is_constant (&nelts))
> > > +    return false;
> > > +
> > > +  /* One element.  */
> > > +  if (type == elem_type)
> >
> > I think this should work on the sizes, so
> >
> >       if (known_eq (size, elem_size))
> > ...
> >
> > that makes sure we do not end up with nelts_op == 1 below and also
> > handle the case where the BIT_FIELD_REF would do int<->float
> > punning.
> >
> Yes, also for V1TImode <-> TImode punning.
> > > +    idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
> > > +  else
> > >      {
> > > -      tree p, m, tem;
> > > -      unsigned HOST_WIDE_INT nelts;
> > > -      m = gimple_assign_rhs3 (def_stmt);
> > > -      if (TREE_CODE (m) != VECTOR_CST
> > > -         || !VECTOR_CST_NELTS (m).is_constant (&nelts))
> > > +      elem_size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
> > > +      unsigned nelts_op;
> > > +      if (!constant_multiple_p (bit_field_size (op), elem_size, &nelts_op))
> >
> > bit_field_size (op) == size?  I think we also want to handle
> > power-of-two nelts_op
> > only (I can't think of how we get a non-power-of-two, but checking
> > pow2p_hwi (nelts_op)
> > woudl be nice if only for documentation purposes)
> Add the check.
> >
> > >         return false;
> > > -      idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
> > > -      idx %= 2 * nelts;
> > > -      if (idx < nelts)
> > > -       {
> > > -         p = gimple_assign_rhs1 (def_stmt);
> > > -       }
> > > -      else
> > > +      unsigned start = TREE_INT_CST_LOW (vector_cst_elt (m, idx));
> > > +      unsigned end = TREE_INT_CST_LOW (vector_cst_elt (m, idx + nelts_op - 1));
> > > +      /* Be in the same vector.  */
> > > +      if ((start < nelts) != (end < nelts))
> > > +       return false;
> > > +      for (unsigned HOST_WIDE_INT i = 1; i != nelts_op; i++)
> > >         {
> > > -         p = gimple_assign_rhs2 (def_stmt);
> > > -         idx -= nelts;
> > > +         /* Continuous area.  */
> > > +         if (TREE_INT_CST_LOW (vector_cst_elt (m, idx + i)) - 1
> > > +             != TREE_INT_CST_LOW (vector_cst_elt (m, idx + i - 1)))
> > > +           return false;
> > >         }
> > > -      tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
> > > -                   unshare_expr (p), op1, bitsize_int (idx * size));
> > > -      gimple_assign_set_rhs1 (stmt, tem);
> > > -      fold_stmt (gsi);
> > > -      update_stmt (gsi_stmt (*gsi));
> > > -      return true;
> > > +      /* Alignment not worse than before.  */
> > > +      unsigned dest_align = TREE_INT_CST_LOW (TYPE_SIZE (type));
> > > +      if (start * elem_size % dest_align)
> > > +       return false;
> >
> > So I think we want to have start * elem_size be a multiple of size
> > (the check I said above is too restrictive on the _original_ bit-field-ref but
> > we want to have for the target bit-field-ref).  I think that's what you check
> > here but see above for the use of poly-ints.
> Changed.
> >
> > > +      idx = start;
> > >      }
> > >
> > > -  return false;
> > > +  idx %= 2 * nelts;
> >
> > that's odd - why do you need to clamp idx?
> Changed.
> This is just copy from original codes, it looks it's not needed any
> more, similar for your below comment.
> >
> > > +  if (idx < nelts)
> > > +    p = gimple_assign_rhs1 (def_stmt);
> > > +  else
> > > +    {
> > > +      p = gimple_assign_rhs2 (def_stmt);
> > > +      idx -= nelts;
> > > +    }
> > > +
> > > +  tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
> > > +               unshare_expr (p), op1, bitsize_int (idx * elem_size));
> >
> > You don't need to unshare_expr 'p' here.
> >
> > Otherwise looks OK.
> >
> Here's updated patch.

Awesome.

OK for trunk if it boostraps/tests.

Thanks,
Richard.

> > Thanks,
> > Richard.
> >
> > > +  gimple_assign_set_rhs1 (stmt, tem);
> > > +  fold_stmt (gsi);
> > > +  update_stmt (gsi_stmt (*gsi));
> > > +  return true;
> > >  }
> > >
> > >  /* Determine whether applying the 2 permutations (mask1 then mask2)
> > > --
> > > 2.18.1
> > >
>
>
>
> --
> BR,
> Hongtao
  

Patch

diff --git a/gcc/testsuite/gcc.target/i386/pr102583.c b/gcc/testsuite/gcc.target/i386/pr102583.c
new file mode 100644
index 00000000000..4ef2f296d0c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr102583.c
@@ -0,0 +1,30 @@ 
+/* { dg-do compile } */
+/* { dg-options "-mavx512f -O2" } */
+/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+32\(%.*%ymm} 1 } } */
+/* { dg-final { scan-assembler-times {(?n)vcvtdq2ps[ \t]+16\(%.*%xmm} 1 } } */
+/* { dg-final { scan-assembler-times {(?n)vmovq[ \t]+16\(%.*%xmm} 1 { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-not {(?n)vpermd[ \t]+.*%zmm} } } */
+
+typedef int v16si __attribute__((vector_size(64)));
+typedef float v8sf __attribute__((vector_size(32)));
+typedef float v4sf __attribute__((vector_size(16)));
+typedef float v2sf __attribute__((vector_size(8)));
+
+v8sf part (v16si *srcp)
+{
+  v16si src = *srcp;
+  return (v8sf) { (float)src[8], (float) src[9], (float)src[10], (float)src[11],
+      (float)src[12], (float)src[13], (float)src[14], (float)src[15] };
+}
+
+v4sf part1 (v16si *srcp)
+{
+  v16si src = *srcp;
+  return (v4sf) { (float)src[4], (float)src[5], (float)src[6], (float)src[7] };
+}
+
+v2sf part2 (v16si *srcp)
+{
+  v16si src = *srcp;
+  return (v2sf) { (float)src[4], (float)src[5] };
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr92645-2.c b/gcc/testsuite/gcc.target/i386/pr92645-2.c
index d34ed3aa8e5..f0608de938a 100644
--- a/gcc/testsuite/gcc.target/i386/pr92645-2.c
+++ b/gcc/testsuite/gcc.target/i386/pr92645-2.c
@@ -29,6 +29,6 @@  void odd (v2si *dst, v4si *srcp)
 }
 
 /* { dg-final { scan-tree-dump-times "BIT_FIELD_REF" 4 "cddce1" } } */
-/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
+/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
 /* Ideally highpart extraction would elide the permutation as well.  */
-/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr92645-3.c b/gcc/testsuite/gcc.target/i386/pr92645-3.c
index 9c08c9fb632..691011195c9 100644
--- a/gcc/testsuite/gcc.target/i386/pr92645-3.c
+++ b/gcc/testsuite/gcc.target/i386/pr92645-3.c
@@ -32,6 +32,6 @@  void odd (v4sf *dst, v8si *srcp)
 /* Four conversions, on the smaller vector type, to not convert excess
    elements.  */
 /* { dg-final { scan-tree-dump-times " = \\\(vector\\\(4\\\) float\\\)" 4 "cddce1" } } */
-/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" } } */
+/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "cddce1" { xfail *-*-* } } } */
 /* Ideally highpart extraction would elide the VEC_PERM_EXPR as well.  */
-/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 2 "cddce1" } } */
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index 484491fa1c5..f91f738895d 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -2334,8 +2334,10 @@  simplify_bitfield_ref (gimple_stmt_iterator *gsi)
   gimple *stmt = gsi_stmt (*gsi);
   gimple *def_stmt;
   tree op, op0, op1;
-  tree elem_type;
-  unsigned idx, size;
+  tree elem_type, type;
+  tree p, m, tem;
+  unsigned HOST_WIDE_INT nelts;
+  unsigned idx, size, elem_size;
   enum tree_code code;
 
   op = gimple_assign_rhs1 (stmt);
@@ -2353,42 +2355,75 @@  simplify_bitfield_ref (gimple_stmt_iterator *gsi)
   op1 = TREE_OPERAND (op, 1);
   code = gimple_assign_rhs_code (def_stmt);
   elem_type = TREE_TYPE (TREE_TYPE (op0));
-  if (TREE_TYPE (op) != elem_type)
+  type = TREE_TYPE (op);
+  /* Also hanlde vector type.
+   .i.e.
+   _7 = VEC_PERM_EXPR <_1, _1, { 2, 3, 2, 3 }>;
+   _11 = BIT_FIELD_REF <_7, 64, 0>;
+
+   to
+
+   _11 = BIT_FIELD_REF <_1, 64, 64>.  */
+  if (type != elem_type
+      && (!VECTOR_TYPE_P (type) || TREE_TYPE (type) != elem_type))
     return false;
 
-  size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
+  elem_size = size = TREE_INT_CST_LOW (TYPE_SIZE (type));
   if (maybe_ne (bit_field_size (op), size))
     return false;
 
-  if (code == VEC_PERM_EXPR
-      && constant_multiple_p (bit_field_offset (op), size, &idx))
+  if (code != VEC_PERM_EXPR
+      || !constant_multiple_p (bit_field_offset (op), size, &idx))
+    return false;
+
+  m = gimple_assign_rhs3 (def_stmt);
+  if (TREE_CODE (m) != VECTOR_CST
+      || !VECTOR_CST_NELTS (m).is_constant (&nelts))
+    return false;
+
+  /* One element.  */
+  if (type == elem_type)
+    idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
+  else
     {
-      tree p, m, tem;
-      unsigned HOST_WIDE_INT nelts;
-      m = gimple_assign_rhs3 (def_stmt);
-      if (TREE_CODE (m) != VECTOR_CST
-	  || !VECTOR_CST_NELTS (m).is_constant (&nelts))
+      elem_size = TREE_INT_CST_LOW (TYPE_SIZE (elem_type));
+      unsigned nelts_op;
+      if (!constant_multiple_p (bit_field_size (op), elem_size, &nelts_op))
 	return false;
-      idx = TREE_INT_CST_LOW (VECTOR_CST_ELT (m, idx));
-      idx %= 2 * nelts;
-      if (idx < nelts)
-	{
-	  p = gimple_assign_rhs1 (def_stmt);
-	}
-      else
+      unsigned start = TREE_INT_CST_LOW (vector_cst_elt (m, idx));
+      unsigned end = TREE_INT_CST_LOW (vector_cst_elt (m, idx + nelts_op - 1));
+      /* Be in the same vector.  */
+      if ((start < nelts) != (end < nelts))
+	return false;
+      for (unsigned HOST_WIDE_INT i = 1; i != nelts_op; i++)
 	{
-	  p = gimple_assign_rhs2 (def_stmt);
-	  idx -= nelts;
+	  /* Continuous area.  */
+	  if (TREE_INT_CST_LOW (vector_cst_elt (m, idx + i)) - 1
+	      != TREE_INT_CST_LOW (vector_cst_elt (m, idx + i - 1)))
+	    return false;
 	}
-      tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
-		    unshare_expr (p), op1, bitsize_int (idx * size));
-      gimple_assign_set_rhs1 (stmt, tem);
-      fold_stmt (gsi);
-      update_stmt (gsi_stmt (*gsi));
-      return true;
+      /* Alignment not worse than before.  */
+      unsigned dest_align = TREE_INT_CST_LOW (TYPE_SIZE (type));
+      if (start * elem_size % dest_align)
+       return false;
+      idx = start;
     }
 
-  return false;
+  idx %= 2 * nelts;
+  if (idx < nelts)
+    p = gimple_assign_rhs1 (def_stmt);
+  else
+    {
+      p = gimple_assign_rhs2 (def_stmt);
+      idx -= nelts;
+    }
+
+  tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
+		unshare_expr (p), op1, bitsize_int (idx * elem_size));
+  gimple_assign_set_rhs1 (stmt, tem);
+  fold_stmt (gsi);
+  update_stmt (gsi_stmt (*gsi));
+  return true;
 }
 
 /* Determine whether applying the 2 permutations (mask1 then mask2)