Re: [PATCH 1/2] Allow REG_EQUAL for ZERO_EXTRACT

[Maxim Kuvyrkov <maxim dot kuvyrkov at linaro dot org>]

> On Jun 28, 2015, at 2:28 PM, Kugan <kugan.vivekanandarajah@linaro.org> wrote:
> 
> This patch allows setting REG_EQUAL for ZERO_EXTRACT and handle that in
> cse (where the src for the ZERO_EXTRACT needs to be calculated)
> 
> Thanks,
> Kugan

> From 75e746e559ffd21b25542b3db627e3b318118569 Mon Sep 17 00:00:00 2001
> From: Kugan Vivekanandarajah <kugan.vivekanandarajah@linaro.org>
> Date: Fri, 26 Jun 2015 17:12:07 +1000
> Subject: [PATCH 1/2] Allow adding REG_EQUAL for ZERO_EXTRACT
> 
> ---
>  gcc/ChangeLog  |  6 ++++++
>  gcc/cse.c      | 41 ++++++++++++++++++++++++++++++++++++++++-
>  gcc/emit-rtl.c |  3 ++-
>  3 files changed, 48 insertions(+), 2 deletions(-)
> 
> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
> index 080aa39..d4a73d6 100644
> --- a/gcc/ChangeLog
> +++ b/gcc/ChangeLog
> @@ -1,3 +1,9 @@
> +2015-06-26  Kugan Vivekanandarajah  <kuganv@linaro.org>
> +
> +	* cse.c (cse_insn): Calculate src_eqv for ZERO_EXTRACT.
> +	* emit-rtl.c (set_for_reg_notes): Allow ZERO_EXTRACT to set
> +	REG_EQUAL note.
> +
>  2015-06-25  H.J. Lu  <hongjiu.lu@intel.com>
>  
>  	* gentarget-def.c (def_target_insn): Cast return of strtol to
> diff --git a/gcc/cse.c b/gcc/cse.c
> index 100c9c8..8add651 100644
> --- a/gcc/cse.c
> +++ b/gcc/cse.c
> @@ -4531,8 +4531,47 @@ cse_insn (rtx_insn *insn)
>    if (n_sets == 1 && REG_NOTES (insn) != 0
>        && (tem = find_reg_note (insn, REG_EQUAL, NULL_RTX)) != 0
>        && (! rtx_equal_p (XEXP (tem, 0), SET_SRC (sets[0].rtl))
> +	  || GET_CODE (SET_DEST (sets[0].rtl)) == ZERO_EXTRACT
>  	  || GET_CODE (SET_DEST (sets[0].rtl)) == STRICT_LOW_PART))
> -    src_eqv = copy_rtx (XEXP (tem, 0));
> +    {
> +      src_eqv = copy_rtx (XEXP (tem, 0));
> +
> +      /* If DEST is of the form ZERO_EXTACT, as in:
> +	 (set (zero_extract:SI (reg:SI 119)
> +		  (const_int 16 [0x10])
> +		  (const_int 16 [0x10]))
> +	      (const_int 51154 [0xc7d2]))
> +	 REG_EQUAL note will specify the value of register (reg:SI 119) at this
> +	 point.  Note that this is different from SRC_EQV. We can however
> +	 calculate SRC_EQV with the position and width of ZERO_EXTRACT.  */
> +      if (GET_CODE (SET_DEST (sets[0].rtl)) == ZERO_EXTRACT)

Consider changing

if (something
    && (!rtx_equal_p)
        || ZERO_EXTRACT
        || STRICT_LOW_PART)

to 

if (something
    && !rtx_equal_p)
  {
     if (ZERO_EXTRACT)
       {
       }
     else if (STRICT_LOW_PART)
       {
       }
  }

Otherwise looks good to me, but you still need another approval.


> +	{
> +	  if (CONST_INT_P (src_eqv)
> +	      && CONST_INT_P (XEXP (SET_DEST (sets[0].rtl), 1))
> +	      && CONST_INT_P (XEXP (SET_DEST (sets[0].rtl), 2)))
> +	    {
> +	      rtx dest_reg = XEXP (SET_DEST (sets[0].rtl), 0);
> +	      rtx width = XEXP (SET_DEST (sets[0].rtl), 1);
> +	      rtx pos = XEXP (SET_DEST (sets[0].rtl), 2);
> +	      HOST_WIDE_INT val = INTVAL (src_eqv);
> +	      HOST_WIDE_INT mask;
> +	      unsigned int shift;
> +	      if (BITS_BIG_ENDIAN)
> +		shift = GET_MODE_PRECISION (GET_MODE (dest_reg))
> +		  - INTVAL (pos) - INTVAL (width);
> +	      else
> +		shift = INTVAL (pos);
> +	      if (INTVAL (width) == HOST_BITS_PER_WIDE_INT)
> +		mask = ~(HOST_WIDE_INT) 0;
> +	      else
> +		mask = ((HOST_WIDE_INT) 1 << INTVAL (width)) - 1;
> +	      val = (val >> shift) & mask;
> +	      src_eqv = GEN_INT (val);
> +	    }
> +	  else
> +	    src_eqv = 0;
> +	}
> +    }
>  
>    /* Set sets[i].src_elt to the class each source belongs to.
>       Detect assignments from or to volatile things
> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
> index e7f7eab..cb891b1 100644
> --- a/gcc/emit-rtl.c
> +++ b/gcc/emit-rtl.c
> @@ -5228,7 +5228,8 @@ set_for_reg_notes (rtx insn)
>    reg = SET_DEST (pat);
>  
>    /* Notes apply to the contents of a STRICT_LOW_PART.  */
> -  if (GET_CODE (reg) == STRICT_LOW_PART)
> +  if (GET_CODE (reg) == STRICT_LOW_PART
> +      || GET_CODE (reg) == ZERO_EXTRACT)
>      reg = XEXP (reg, 0);
>  
>    /* Check that we have a register.  */
> -- 
> 1.9.1
> 
> 


--
Maxim Kuvyrkov
www.linaro.org