[PATCH][ARM][1/4] Replace uses of int_log2 by exact_log2

[Ramana Radhakrishnan]

On 24/05/16 14:25, Kyrill Tkachov wrote:
> Hi all,
> 
> The int_log2 function in arm.c is not really useful since we already have a generic function for calculating
> the log2 of HOST_WIDE_INTs. The only difference in functionality is that int_log2 also asserts that the result
> is no greater than 31.
> 
> This patch removes int_log2 in favour of exact_log2 and adds an assert on the result to make sure the return
> value was as expected.
> 
> Bootstrapped and tested on arm-none-linux-gnueabihf.
> 
> Is this ok? Or is there something I'm missing about int_log2?


Not that I can see - this is OK. 

Thanks for the patience, I'm behind on patch reviews thanks to unplanned time off recently.

Ramana
> 
> Thanks,
> Kyrill
> 
> 2016-05-24  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> 
>     * config/arm/arm.c (int_log2): Delete definition and prototype.
>     (shift_op): Use exact_log2 instead of int_log2.
>     (vfp3_const_double_for_fract_bits): Likewise.
> 
> arm-1.patch
> 
> 
> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> index 6cc0feb6f87157171c889e998e52b4e5d8683c66..3fe6eab46f3c18ace6899b5be45ad646992f43e4 100644
> --- a/gcc/config/arm/arm.c
> +++ b/gcc/config/arm/arm.c
> @@ -104,7 +104,6 @@ static void arm_print_operand_address (FILE *, machine_mode, rtx);
>  static bool arm_print_operand_punct_valid_p (unsigned char code);
>  static const char *fp_const_from_val (REAL_VALUE_TYPE *);
>  static arm_cc get_arm_condition_code (rtx);
> -static HOST_WIDE_INT int_log2 (HOST_WIDE_INT);
>  static const char *output_multi_immediate (rtx *, const char *, const char *,
>  					   int, HOST_WIDE_INT);
>  static const char *shift_op (rtx, HOST_WIDE_INT *);
> @@ -18920,7 +18919,8 @@ shift_op (rtx op, HOST_WIDE_INT *amountp)
>  	  return NULL;
>  	}
>  
> -      *amountp = int_log2 (*amountp);
> +      *amountp = exact_log2 (*amountp);
> +      gcc_assert (IN_RANGE (*amountp, 0, 31));
>        return ARM_LSL_NAME;
>  
>      default:
> @@ -18952,22 +18952,6 @@ shift_op (rtx op, HOST_WIDE_INT *amountp)
>    return mnem;
>  }
>  
> -/* Obtain the shift from the POWER of two.  */
> -
> -static HOST_WIDE_INT
> -int_log2 (HOST_WIDE_INT power)
> -{
> -  HOST_WIDE_INT shift = 0;
> -
> -  while ((((HOST_WIDE_INT) 1 << shift) & power) == 0)
> -    {
> -      gcc_assert (shift <= 31);
> -      shift++;
> -    }
> -
> -  return shift;
> -}
> -
>  /* Output a .ascii pseudo-op, keeping track of lengths.  This is
>     because /bin/as is horribly restrictive.  The judgement about
>     whether or not each character is 'printable' (and can be output as
> @@ -27691,7 +27675,11 @@ vfp3_const_double_for_fract_bits (rtx operand)
>  	  HOST_WIDE_INT value = real_to_integer (&r0);
>  	  value = value & 0xffffffff;
>  	  if ((value != 0) && ( (value & (value - 1)) == 0))
> -	    return int_log2 (value);
> +	    {
> +	      int ret = exact_log2 (value);
> +	      gcc_assert (IN_RANGE (ret, 0, 31));
> +	      return ret;
> +	    }
>  	}
>      }
>    return 0;
>