[PATCH] Fix PR61375: cancel bswap optimization when value doesn't fit in a HOST_WIDE_INT

[Thomas Preud'homme]

Ping?

> -----Original Message-----
> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> owner@gcc.gnu.org] On Behalf Of Thomas Preud'homme
> Sent: Thursday, June 26, 2014 9:11 AM
> To: 'Jakub Jelinek'
> Cc: Richard Biener; GCC Patches
> Subject: RE: [PATCH] Fix PR61375: cancel bswap optimization when value
> doesn't fit in a HOST_WIDE_INT
> 
> Ok, what about the following patch and associated ChangeLog entries?
> 
> 2014-06-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
> 	PR tree-optimization/61375
> 	* tree-ssa-math-opts.c (find_bswap_or_nop_1): Cancel optimization
> if
> 	symbolic number cannot be represented in an unsigned
> HOST_WIDE_INT.
> 	(execute_optimize_bswap): Cancel optimization if CHAR_BIT != 8.
> 
> 2014-06-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
> 	PR tree-optimization/61375
> 	* gcc.c-torture/execute/pr61375-1.c: New test.
> 
> 
> diff --git a/gcc/testsuite/gcc.c-torture/execute/pr61375.c
> b/gcc/testsuite/gcc.c-torture/execute/pr61375.c
> new file mode 100644
> index 0000000..6fb4693
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/execute/pr61375.c
> @@ -0,0 +1,35 @@
> +#ifdef __UINT64_TYPE__
> +typedef __UINT64_TYPE__ uint64_t;
> +#else
> +typedef unsigned long long uint64_t;
> +#endif
> +
> +#ifndef __SIZEOF_INT128__
> +#define __int128 long long
> +#endif
> +
> +/* Some version of bswap optimization would ICE when analyzing a mask
> constant
> +   too big for an HOST_WIDE_INT (PR61375).  */
> +
> +__attribute__ ((noinline, noclone)) uint64_t
> +uint128_central_bitsi_ior (unsigned __int128 in1, uint64_t in2)
> +{
> +  __int128 mask = (__int128)0xffff << 56;
> +  return ((in1 & mask) >> 56) | in2;
> +}
> +
> +int
> +main (int argc)
> +{
> +  __int128 in = 1;
> +#ifdef __SIZEOF_INT128__
> +  in <<= 64;
> +#endif
> +  if (sizeof (uint64_t) * __CHAR_BIT__ != 64)
> +    return 0;
> +  if (sizeof (unsigned __int128) * __CHAR_BIT__ != 128)
> +    return 0;
> +  if (uint128_central_bitsi_ior (in, 2) != 0x102)
> +    __builtin_abort ();
> +  return 0;
> +}
> diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
> index 9ff857c..045bf48 100644
> --- a/gcc/tree-ssa-math-opts.c
> +++ b/gcc/tree-ssa-math-opts.c
> @@ -1740,6 +1740,8 @@ find_bswap_1 (gimple stmt, struct
> symbolic_number *n, int limit)
>  	  n->size = TYPE_PRECISION (TREE_TYPE (rhs1));
>  	  if (n->size % BITS_PER_UNIT != 0)
>  	    return NULL_TREE;
> +	  if (n->size > HOST_BITS_PER_WIDEST_INT)
> +	    return NULL_TREE;
>  	  n->size /= BITS_PER_UNIT;
>  	  n->n = (sizeof (HOST_WIDEST_INT) < 8 ? 0 :
>  		  (unsigned HOST_WIDEST_INT)0x08070605 << 32 |
> 0x04030201);
> @@ -1781,6 +1783,8 @@ find_bswap_1 (gimple stmt, struct
> symbolic_number *n, int limit)
>  	    type_size = TYPE_PRECISION (gimple_expr_type (stmt));
>  	    if (type_size % BITS_PER_UNIT != 0)
>  	      return NULL_TREE;
> +	    if (type_size > (int) HOST_BITS_PER_WIDEST_INT)
> +	      return NULL_TREE;
> 
>  	    if (type_size / BITS_PER_UNIT < (int)(sizeof (HOST_WIDEST_INT)))
>  	      {
> @@ -1911,7 +1915,7 @@ execute_optimize_bswap (void)
>    bool changed = false;
>    tree bswap16_type = NULL_TREE, bswap32_type = NULL_TREE,
> bswap64_type = NULL_TREE;
> 
> -  if (BITS_PER_UNIT != 8)
> +  if (BITS_PER_UNIT != 8 || CHAR_BIT != 8)
>      return 0;
> 
>    if (sizeof (HOST_WIDEST_INT) < 8)
> 
> Is this ok for 4.8 and 4.9 branches?
> 
> Best regards,
> 
> Thomas
> 
>