Re: [PATCH] Add 3 target hooks for memset

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, May 20, 2021 at 10:42 PM Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
>
> On 5/20/21 10:49 PM, H.J. Lu wrote:
> > On Wed, May 19, 2021 at 5:55 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>
> >> On Wed, May 19, 2021 at 2:25 AM Richard Biener
> >> <richard.guenther@gmail.com> wrote:
> >>>
> >>> On Tue, May 18, 2021 at 9:16 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>>>
> >>>> Add TARGET_READ_MEMSET_VALUE and TARGET_GEN_MEMSET_VALUE to support
> >>>> target instructions to duplicate QImode value to TImode/OImode/XImode
> >>>> value for memmset.
> >>>>
> >>>>         PR middle-end/90773
> >>>>         * builtins.c (builtin_memset_read_str): Call
> >>>>         targetm.read_memset_value.
> >>>>         (builtin_memset_gen_str): Call targetm.gen_memset_value.
> >>>>         * target.def (read_memset_value): New hook.
> >>>>         (gen_memset_value): Likewise.
> >>>>         * targhooks.c: Inclue "builtins.h".
> >>>>         (default_read_memset_value): New function.
> >>>>         (default_gen_memset_value): Likewise.
> >>>>         * targhooks.h (default_read_memset_value): New prototype.
> >>>>         (default_gen_memset_value): Likewise.
> >>>>         * doc/tm.texi.in: Add TARGET_READ_MEMSET_VALUE and
> >>>>         TARGET_GEN_MEMSET_VALUE hooks.
> >>>>         * doc/tm.texi: Regenerated.
> >>>> ---
> >>>>  gcc/builtins.c     | 47 ++++----------------------------------
> >>>>  gcc/doc/tm.texi    | 16 +++++++++++++
> >>>>  gcc/doc/tm.texi.in |  4 ++++
> >>>>  gcc/target.def     | 20 +++++++++++++++++
> >>>>  gcc/targhooks.c    | 56 ++++++++++++++++++++++++++++++++++++++++++++++
> >>>>  gcc/targhooks.h    |  4 ++++
> >>>>  6 files changed, 104 insertions(+), 43 deletions(-)
> >>>>
> >>>> diff --git a/gcc/builtins.c b/gcc/builtins.c
> >>>> index e1b284846b1..f78a36478ef 100644
> >>>> --- a/gcc/builtins.c
> >>>> +++ b/gcc/builtins.c
> >>>> @@ -6584,24 +6584,11 @@ expand_builtin_strncpy (tree exp, rtx target)
> >>>>     previous iteration.  */
> >>>>
> >>>>  rtx
> >>>> -builtin_memset_read_str (void *data, void *prevp,
> >>>> +builtin_memset_read_str (void *data, void *prev,
> >>>>                          HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> >>>>                          scalar_int_mode mode)
> >>>>  {
> >>>> -  by_pieces_prev *prev = (by_pieces_prev *) prevp;
> >>>> -  if (prev != nullptr && prev->data != nullptr)
> >>>> -    {
> >>>> -      /* Use the previous data in the same mode.  */
> >>>> -      if (prev->mode == mode)
> >>>> -       return prev->data;
> >>>> -    }
> >>>> -
> >>>> -  const char *c = (const char *) data;
> >>>> -  char *p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
> >>>> -
> >>>> -  memset (p, *c, GET_MODE_SIZE (mode));
> >>>> -
> >>>> -  return c_readstr (p, mode);
> >>>> +  return targetm.read_memset_value ((const char *) data, prev, mode);
> >>>>  }
> >>>>
> >>>>  /* Callback routine for store_by_pieces.  Return the RTL of a register
> >>>> @@ -6611,37 +6598,11 @@ builtin_memset_read_str (void *data, void *prevp,
> >>>>     nullptr, it has the RTL info from the previous iteration.  */
> >>>>
> >>>>  static rtx
> >>>> -builtin_memset_gen_str (void *data, void *prevp,
> >>>> +builtin_memset_gen_str (void *data, void *prev,
> >>>>                         HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> >>>>                         scalar_int_mode mode)
> >>>>  {
> >>>> -  rtx target, coeff;
> >>>> -  size_t size;
> >>>> -  char *p;
> >>>> -
> >>>> -  by_pieces_prev *prev = (by_pieces_prev *) prevp;
> >>>> -  if (prev != nullptr && prev->data != nullptr)
> >>>> -    {
> >>>> -      /* Use the previous data in the same mode.  */
> >>>> -      if (prev->mode == mode)
> >>>> -       return prev->data;
> >>>> -
> >>>> -      target = simplify_gen_subreg (mode, prev->data, prev->mode, 0);
> >>>> -      if (target != nullptr)
> >>>> -       return target;
> >>>> -    }
> >>>> -
> >>>> -  size = GET_MODE_SIZE (mode);
> >>>> -  if (size == 1)
> >>>> -    return (rtx) data;
> >>>> -
> >>>> -  p = XALLOCAVEC (char, size);
> >>>> -  memset (p, 1, size);
> >>>> -  coeff = c_readstr (p, mode);
> >>>> -
> >>>> -  target = convert_to_mode (mode, (rtx) data, 1);
> >>>> -  target = expand_mult (mode, target, coeff, NULL_RTX, 1);
> >>>> -  return force_reg (mode, target);
> >>>> +  return targetm.gen_memset_value ((rtx) data, prev, mode);
> >>>>  }
> >>>>
> >>>>  /* Expand expression EXP, which is a call to the memset builtin.  Return
> >>>> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> >>>> index 85ea9395560..51385044e76 100644
> >>>> --- a/gcc/doc/tm.texi
> >>>> +++ b/gcc/doc/tm.texi
> >>>> @@ -11868,6 +11868,22 @@ This function prepares to emit a conditional comparison within a sequence
> >>>>   @var{bit_code} is @code{AND} or @code{IOR}, which is the op on the compares.
> >>>>  @end deftypefn
> >>>>
> >>>> +@deftypefn {Target Hook} rtx TARGET_READ_MEMSET_VALUE (const char *@var{c}, void *@var{prev}, scalar_int_mode @var{mode})
> >>>> +This function returns the RTL of a constant integer corresponding to
> >>>> +target reading @code{GET_MODE_SIZE (@var{mode})} bytes from the stringn
> >>>> +constant @var{str}.  If @var{prev} is not @samp{nullptr}, it contains
> >>>> +the RTL information from the previous interation.
> >>>> +@end deftypefn
> >>>> +
> >>>> +@deftypefn {Target Hook} rtx TARGET_GEN_MEMSET_VALUE (rtx @var{data}, void *@var{prev}, scalar_int_mode @var{mode})
> >>>> +This function returns the RTL of a register containing
> >>>> +@code{GET_MODE_SIZE (@var{mode})} consecutive copies of the unsigned
> >>>> +char value given in the RTL register @var{data}.  For example, if
> >>>> +@var{mode} is 4 bytes wide, return the RTL for 0x01010101*@var{data}.
> >>>> +If @var{PREV} is not @samp{nullptr}, it is the RTL information from
> >>>> +the previous iteration.
> >>>> +@end deftypefn
> >>>> +
> >>>>  @deftypefn {Target Hook} unsigned TARGET_LOOP_UNROLL_ADJUST (unsigned @var{nunroll}, class loop *@var{loop})
> >>>>  This target hook returns a new value for the number of times @var{loop}
> >>>>  should be unrolled. The parameter @var{nunroll} is the number of times
> >>>> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> >>>> index d8e3de14af1..8d4c3949fbf 100644
> >>>> --- a/gcc/doc/tm.texi.in
> >>>> +++ b/gcc/doc/tm.texi.in
> >>>> @@ -7956,6 +7956,10 @@ lists.
> >>>>
> >>>>  @hook TARGET_GEN_CCMP_NEXT
> >>>>
> >>>> +@hook TARGET_READ_MEMSET_VALUE
> >>>> +
> >>>> +@hook TARGET_GEN_MEMSET_VALUE
> >>>> +
> >>>>  @hook TARGET_LOOP_UNROLL_ADJUST
> >>>>
> >>>>  @defmac POWI_MAX_MULTS
> >>>> diff --git a/gcc/target.def b/gcc/target.def
> >>>> index bbaf6b4f3a0..c9aca40fa88 100644
> >>>> --- a/gcc/target.def
> >>>> +++ b/gcc/target.def
> >>>> @@ -2694,6 +2694,26 @@ DEFHOOK
> >>>>   rtx, (rtx_insn **prep_seq, rtx_insn **gen_seq, rtx prev, int cmp_code, tree op0, tree op1, int bit_code),
> >>>>   NULL)
> >>>>
> >>>> +DEFHOOK
> >>>> +(read_memset_value,
> >>>> + "This function returns the RTL of a constant integer corresponding to\n\
> >>>> +target reading @code{GET_MODE_SIZE (@var{mode})} bytes from the stringn\n\
> >>>> +constant @var{str}.  If @var{prev} is not @samp{nullptr}, it contains\n\
> >>>
> >>> where is 'str' defined?  I can't really tell what's the difference
> >>
> >> Fixed with
> >>
> >> diff --git a/gcc/target.def b/gcc/target.def
> >> index c9aca40fa88..4c3a5fcc634 100644
> >> --- a/gcc/target.def
> >> +++ b/gcc/target.def
> >> @@ -2699,8 +2699,8 @@ DEFHOOK
> >>   "This function returns the RTL of a constant integer corresponding to\n\
> >>  target reading @code{GET_MODE_SIZE (@var{mode})} bytes from the string\n\
> >>  constant @var{str}.  If @var{prev} is not @samp{nullptr}, it contains\n\
> >> -the RTL information from the previous interation.",
> >> - rtx, (const char *c, void *prev, scalar_int_mode mode),
> >> +the RTL information from the previous iteration.",
> >> + rtx, (const char *str, void *prev, scalar_int_mode mode),
> >>   default_read_memset_value)
> >>
> >>  DEFHOOK
> >>
> >>> from read_memset_value
> >>> and gen_memset_value.
> >>
> >> The difference is that input of read_memset_value is a string constant
> >> like "123" and input of gen_memset_value is an RTL register.
> >>
> >>> Somehow I feel that an optab for the "splat" operation similar
> >>> to vec_duplicate might be a better way to expose this - of course
> >>> that doesn't handle the "prev" thing.
> >>
> >> The x86 backend has ix86_expand_vector_init_duplicate () to
> >> broadcast QImode to TImode/OImode/XImode:
> >>
> >> /* A subroutine of ix86_expand_vector_init.  Store into TARGET a vector
> >>    with all elements equal to VAR.  Return true if successful.  */
> >>
> >> bool
> >> ix86_expand_vector_init_duplicate (bool mmx_ok, machine_mode mode,
> >>                                    rtx target, rtx val)
> >>
> >>> So how's this the right point of abstraction to the target?
> >>
> >> I can add 2 target hooks, one for scratch register and one for
> >> broadcasting QImode to TImode/OImode/XImode.   Then I can
> >> move x86 codes to the middle-end.
> >>
> >
> > Here is the patch to add 3 target hooks:
> >
> >  -- Target Hook: rtx TARGET_READ_MEMSET_VALUE (const char *C,
> >           scalar_int_mode MODE)
> >      This function returns the RTL of a constant integer corresponding
> >      to target reading 'GET_MODE_SIZE (MODE)' bytes from the string
> >      constant C.
> >
> >  -- Target Hook: rtx TARGET_GEN_MEMSET_VALUE (rtx DATA, scalar_int_mode
> >           MODE)
> >      This function returns the RTL of a register containing
> >      'GET_MODE_SIZE (MODE)' consecutive copies of the unsigned char
> >      value given in the RTL register DATA.  For example, if MODE is 4
> >      bytes wide, return the RTL for 0x01010101*DATA.
> >
> >  -- Target Hook: rtx TARGET_GEN_MEMSET_VALUE_FROM_PREV (void *PREV,
> >           scalar_int_mode MODE)
> >      This function returns the RTL of a register in MODE generated from
> >      PREV in the previous iteration.
> >
> > with
> >
> > /* Return the RTL of a register in MODE generated from PREV in the
> >    previous iteration.  */
> >
> > static rtx
> > gen_memset_value_from_prev (void *prevp, scalar_int_mode mode)
> > {
> >   by_pieces_prev *prev = (by_pieces_prev *) prevp;
> >   rtx value;
> >   if (prev != nullptr && prev->data != nullptr)
> >     {
> >       /* Use the previous data in the same mode.  */
> >       if (prev->mode == mode)
> >         return prev->data;
> >
> >       value = targetm.gen_memset_value_from_prev (prevp, mode);
> >     }
> >   else
> >     value = nullptr;
> >   return value;
> > }
> >
> > /* Callback routine for store_by_pieces.  Read GET_MODE_BITSIZE (MODE)
> >    bytes from constant string DATA + OFFSET and return it as target
> >    constant.  If PREV isn't nullptr, it has the RTL info from the
> >    previous iteration.  */
> >
> > rtx
> > builtin_memset_read_str (void *data, void *prev,
> >                          HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> >                          scalar_int_mode mode)
> > {
> >   const char *str = (const char *) data;
> >
> >   /* Don't use the previous value if size is 1.  */
> >   if (GET_MODE_SIZE (mode) == 1)
> >     return default_read_memset_value (str, mode);
> >
> >   rtx value = gen_memset_value_from_prev (prev, mode);
> >   if (value)
> >     return value;
> >
> >   return targetm.read_memset_value (str, mode);
> > }
> >
> > /* Callback routine for store_by_pieces.  Return the RTL of a register
> >    containing GET_MODE_SIZE (MODE) consecutive copies of the unsigned
> >    char value given in the RTL register data.  For example, if mode is
> >    4 bytes wide, return the RTL for 0x01010101*data.  If PREV isn't
> >    nullptr, it has the RTL info from the previous iteration.  */
> >
> > static rtx
> > builtin_memset_gen_str (void *datap, void *prev,
> >                         HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> >                         scalar_int_mode mode)
> > {
> >   rtx data = (rtx) datap;
> >
> >   /* Don't use the previous value if size is 1.  */
> >   if (GET_MODE_SIZE (mode) == 1)
> >     return data;
> >
> >   rtx value = gen_memset_value_from_prev (prev, mode);
> >   if (value)
> >     return value;
> >
> >   return targetm.gen_memset_value (data, mode);
> > }> +/* Default implementation of TARGET_GEN_MEMSET_VALUE.  */
> > +
> > +rtx
> > +default_gen_memset_value (rtx data, scalar_int_mode mode)
> > +{
> > +  rtx target, coeff;
> > +  size_t size;
> > +  char *p;
> > +
> > +  size = GET_MODE_SIZE (mode);
> > +  if (size == 1)
> > +    return data;
> > +
> > +  p = XALLOCAVEC (char, size);
> > +  memset (p, 1, size);
> > +  coeff = c_readstr (p, mode);
> > +
> > +  target = convert_to_mode (mode, data, 1);
> > +  target = expand_mult (mode, target, coeff, NULL_RTX, 1);
>
>
> Note this formula does not work for data = -1 for instance,
> since 0x01010101U * -1 = 0xFEFEFEFFU
> but memset(str, n, -1) set it to 0xFFFFFFFFU, right?
>
> So are we sure that the value of "data" is always in the range [0..255] ?

I didn't change the formula.  I just turned the current formula into
a target hook.  For memset,

DESCRIPTION
       The  memset()  function  fills  the  first  n  bytes of the memory area
       pointed to by s with the constant byte c.

"data", aka the constant byte c, is a byte in the range [0..255].

-- 
H.J.