RE: [PATCH, AArch64 4.7] Backport of __builtin_bswap16 optimisation

["Ian Bolton" <ian.bolton@arm.com>]

It turned out that this patch depended on another one from
earlier, so I have backported that to ARM/aarch64-4.7-branch too.

http://gcc.gnu.org/ml/gcc-patches/2012-04/msg00452.html


Cheers,
Ian

> -----Original Message-----
> From: Ian Bolton [mailto:ian.bolton@arm.com]
> Sent: 23 November 2012 18:09
> To: gcc-patches@gcc.gnu.org
> Subject: [PATCH, AArch64 4.7] Backport of __builtin_bswap16
> optimisation
> 
> I had already committed my testcase for this for aarch64, but
> it depends on this patch that doesn't yet exist in 4.7, so I
> backported to our ARM/aarch64-4.7-branch.
> 
> Cheers,
> Ian
> 
> 
> 
> From:
> http://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=f811051bf87b1de7804c19
> c8192d0d099d157145
> 
> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
> index be34843..ce08fce 100644
> --- a/gcc/ChangeLog
> +++ b/gcc/ChangeLog
> @@ -1,3 +1,8 @@
> +2012-09-26  Christophe Lyon <christophe.lyon@linaro.org>
> +
> +	* tree-ssa-math-opts.c (bswap_stats): Add found_16bit field.
> +	(execute_optimize_bswap): Add support for builtin_bswap16.
> +
>  2012-09-26  Richard Guenther  <rguenther@suse.de>
> 
>  	* tree.h (DECL_IS_BUILTIN): Compare LOCATION_LOCUS.
> diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
> index 3aad841..7c96949 100644
> --- a/gcc/testsuite/ChangeLog
> +++ b/gcc/testsuite/ChangeLog
> @@ -1,3 +1,7 @@
> +2012-09-26  Christophe Lyon <christophe.lyon@linaro.org>
> +
> +	* gcc.target/arm/builtin-bswap16-1.c: New testcase.
> +
>  2012-09-25  Segher Boessenkool  <segher@kernel.crashing.org>
> 
>  	PR target/51274
> diff --git a/gcc/testsuite/gcc.target/arm/builtin-bswap16-1.c
> b/gcc/testsuite/gcc.target/arm/builtin-bswap16-1.c
> new file mode 100644
> index 0000000..6920f00
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/arm/builtin-bswap16-1.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-require-effective-target arm_arch_v6_ok } */
> +/* { dg-add-options arm_arch_v6 } */
> +/* { dg-final { scan-assembler-not "orr\[ \t\]" } } */
> +
> +unsigned short swapu16_1 (unsigned short x)
> +{
> +  return (x << 8) | (x >> 8);
> +}
> +
> +unsigned short swapu16_2 (unsigned short x)
> +{
> +  return (x >> 8) | (x << 8);
> +}
> diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
> index 16ff397..d9f4e9e 100644
> --- a/gcc/tree-ssa-math-opts.c
> +++ b/gcc/tree-ssa-math-opts.c
> @@ -154,6 +154,9 @@ static struct
> 
>  static struct
>  {
> +  /* Number of hand-written 16-bit bswaps found.  */
> +  int found_16bit;
> +
>    /* Number of hand-written 32-bit bswaps found.  */
>    int found_32bit;
> 
> @@ -1803,9 +1806,9 @@ static unsigned int
>  execute_optimize_bswap (void)
>  {
>    basic_block bb;
> -  bool bswap32_p, bswap64_p;
> +  bool bswap16_p, bswap32_p, bswap64_p;
>    bool changed = false;
> -  tree bswap32_type = NULL_TREE, bswap64_type = NULL_TREE;
> +  tree bswap16_type = NULL_TREE, bswap32_type = NULL_TREE,
> bswap64_type = NULL_TREE;
> 
>    if (BITS_PER_UNIT != 8)
>      return 0;
> @@ -1813,17 +1816,25 @@ execute_optimize_bswap (void)
>    if (sizeof (HOST_WIDEST_INT) < 8)
>      return 0;
> 
> +  bswap16_p = (builtin_decl_explicit_p (BUILT_IN_BSWAP16)
> +	       && optab_handler (bswap_optab, HImode) !=
> CODE_FOR_nothing);
>    bswap32_p = (builtin_decl_explicit_p (BUILT_IN_BSWAP32)
>  	       && optab_handler (bswap_optab, SImode) !=
> CODE_FOR_nothing);
>    bswap64_p = (builtin_decl_explicit_p (BUILT_IN_BSWAP64)
>  	       && (optab_handler (bswap_optab, DImode) !=
> CODE_FOR_nothing
>  		   || (bswap32_p && word_mode == SImode)));
> 
> -  if (!bswap32_p && !bswap64_p)
> +  if (!bswap16_p && !bswap32_p && !bswap64_p)
>      return 0;
> 
>    /* Determine the argument type of the builtins.  The code later on
>       assumes that the return and argument type are the same.  */
> +  if (bswap16_p)
> +    {
> +      tree fndecl = builtin_decl_explicit (BUILT_IN_BSWAP16);
> +      bswap16_type = TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (fndecl)));
> +    }
> +
>    if (bswap32_p)
>      {
>        tree fndecl = builtin_decl_explicit (BUILT_IN_BSWAP32);
> @@ -1863,6 +1874,13 @@ execute_optimize_bswap (void)
> 
>  	  switch (type_size)
>  	    {
> +	    case 16:
> +	      if (bswap16_p)
> +		{
> +		  fndecl = builtin_decl_explicit (BUILT_IN_BSWAP16);
> +		  bswap_type = bswap16_type;
> +		}
> +	      break;
>  	    case 32:
>  	      if (bswap32_p)
>  		{
> @@ -1890,7 +1908,9 @@ execute_optimize_bswap (void)
>  	    continue;
> 
>  	  changed = true;
> -	  if (type_size == 32)
> +	  if (type_size == 16)
> +	    bswap_stats.found_16bit++;
> +	  else if (type_size == 32)
>  	    bswap_stats.found_32bit++;
>  	  else
>  	    bswap_stats.found_64bit++;
> @@ -1935,6 +1955,8 @@ execute_optimize_bswap (void)
>  	}
>      }
> 
> +  statistics_counter_event (cfun, "16-bit bswap implementations
> found",
> +			    bswap_stats.found_16bit);
>    statistics_counter_event (cfun, "32-bit bswap implementations
> found",
>  			    bswap_stats.found_32bit);
>    statistics_counter_event (cfun, "64-bit bswap implementations
> found",