Re: [PATCH 1/4] rs6000: build constant via li;rotldi

[David Edelsohn <dje.gcc@gmail.com>]

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Hi, Jiufu

	* config/rs6000/rs6000.cc (can_be_rotated_to_possitive_li): New function.
	(can_be_rotated_to_negative_li): New function.
	(can_be_built_by_li_and_rotldi): New function.
	(rs6000_emit_set_long_const): Call can_be_built_by_li_and_rotldi.

In English the word "positive" contains one "s", not two.  Please
correct throughout the patches.

Also a style issue, comments before a function should be followed by a
blank line.

> +/* Check if C can be rotated to a possitive value which 'li' instruction

positive
> +   is able to load.  If so, set *ROT to the number by which C is rotated,
> +   and return true.  Return false otherwise.  */

Add a blank line here
> +static bool
> +can_be_rotated_to_possitive_li (HOST_WIDE_INT c, int *rot)

positive
> +{
> +  /* 49 leading zeros and 15 lowbits on the possitive value

low bits, positive

> +     generated by 'li' instruction.  */
> +  return can_be_rotated_to_lowbits (c, 15, rot);
> +}

> +/* Check if value C can be built by 2 instructions: one is 'li', another is
> +   rotldi.
> +
> +   If so, *SHIFT is set to the shift operand of rotldi(rldicl), and *MASK
> +   is set to -1, and return true.  Return false otherwise.  */
> +static bool
> +can_be_built_by_li_and_rotldi (HOST_WIDE_INT c, int *shift,
> +				   HOST_WIDE_INT *mask)
> +{
> +  int n;
> +  if (can_be_rotated_to_possitive_li (c, &n)
> +      || can_be_rotated_to_negative_li (c, &n))
> +    {
> +      *mask = HOST_WIDE_INT_M1;
> +      *shift = HOST_BITS_PER_WIDE_INT - n;
> +      return true;
> +    }
> +
> +  return false;
> +}
> +
>  /* Subroutine of rs6000_emit_set_const, handling PowerPC64 DImode.
>     Output insns to set DEST equal to the constant C as a series of
>     lis, ori and shl instructions.  */
> @@ -10246,15 +10285,14 @@ static void>  rs6000_emit_set_long_const (rtx dest, HOST_WIDE_INT c)>  {>    rtx temp;> +  int shift;> +  HOST_WIDE_INT mask;>    HOST_WIDE_INT ud1, ud2, ud3, ud4;>  >    ud1 = c & 0xffff;> -  c = c >> 16;> -  ud2 = c & 0xffff;> -  c = c >> 16;> -  ud3 = c & 0xffff;> -  c = c >> 16;> -  ud4 = c & 0xffff;> +  ud2 = (c >> 16) & 0xffff;> +  ud3 = (c >> 32) & 0xffff;> +  ud4 = (c >> 48) & 0xffff;>  >    if ((ud4 == 0xffff && ud3 == 0xffff && ud2 == 0xffff && (ud1 & 0x8000))>        || (ud4 == 0 && ud3 == 0 && ud2 == 0 && ! (ud1 & 0x8000)))> @@ -10278,6 +10316,19 @@ rs6000_emit_set_long_const (rtx dest, HOST_WIDE_INT c)>        emit_move_insn (dest, gen_rtx_XOR (DImode, temp,>  					 GEN_INT ((ud2 ^ 0xffff) << 16)));>      }> +  else if (can_be_built_by_li_and_rotldi (c, &shift, &mask))> +    {> +      temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);> +      unsigned HOST_WIDE_INT imm = (c | ~mask);> +      imm = (imm >> shift) | (imm << (HOST_BITS_PER_WIDE_INT - shift));> +> +      emit_move_insn (temp, GEN_INT (imm));> +      if (shift != 0)> +	temp = gen_rtx_ROTATE (DImode, temp, GEN_INT (shift));> +      if (mask != HOST_WIDE_INT_M1)

How is mask != HOST_WIDE_INT_M1? The call to
can_by_built_by_li_and_rotldi() set it

to that value and it is not modified in the interim statements.

> +	temp = gen_rtx_AND (DImode, temp, GEN_INT (mask));> +      emit_move_insn (dest, temp);> +    }>    else if (ud3 == 0 && ud4 == 0)>      {>        temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);

Thanks, David