Some wide-int review comments

On 11/08/2013 05:30 AM, Richard Sandiford wrote:
> Some comments from looking through the diff with the merge point,
> ignoring wide-int.h and wide-int.cc.  A few more to follow in the
> form of patchses.
>
> --------------------
>
> dwarf2out.c has:
>
> +    case CONST_WIDE_INT:
> +      if (mode == VOIDmode)
> +	mode = GET_MODE (rtl);
> +
> +      if (mode != VOIDmode && (dwarf_version >= 4 || !dwarf_strict))
> +	{
> +	  gcc_assert (mode == GET_MODE (rtl) || VOIDmode == GET_MODE (rtl));
> +
> +	  /* Note that a CONST_DOUBLE rtx could represent either an integer
> +	     or a floating-point constant.  A CONST_DOUBLE is used whenever
> +	     the constant requires more than one word in order to be
> +	     adequately represented.  We output CONST_DOUBLEs as blocks.  */
> +	  loc_result = new_loc_descr (DW_OP_implicit_value,
> +				      GET_MODE_SIZE (mode), 0);
> +	  loc_result->dw_loc_oprnd2.val_class = dw_val_class_wide_int;
> +	  loc_result->dw_loc_oprnd2.v.val_wide = ggc_alloc_cleared_wide_int ();
> +	  *loc_result->dw_loc_oprnd2.v.val_wide = std::make_pair (rtl, mode);
>
> The comment looks like a cut-&-paste.  The "mode == GET_MODE (rtl)"
> bit should never be true.
i removed the assertion completely.  it really is unnecessary.
> --------------------
>
>  From fold-const.c:
>
> @@ -13686,14 +13548,17 @@ fold_binary_loc (location_t loc,
>   		  break;
>   		}
>   
> -	    else if (TREE_INT_CST_HIGH (arg1) == signed_max_hi
> -		     && TREE_INT_CST_LOW (arg1) == signed_max_lo
> +	    else if (wi::eq_p (arg1, signed_max)
>   		     && TYPE_UNSIGNED (arg1_type)
> +		     /* KENNY QUESTIONS THE CHECKING OF THE BITSIZE
> +			HERE.  HE FEELS THAT THE PRECISION SHOULD BE
> +			CHECKED */
> +
>   		     /* We will flip the signedness of the comparison operator
>   			associated with the mode of arg1, so the sign bit is
>   			specified by this mode.  Check that arg1 is the signed
>   			max associated with this sign bit.  */
> -		     && width == GET_MODE_BITSIZE (TYPE_MODE (arg1_type))
> +		     && prec == GET_MODE_BITSIZE (TYPE_MODE (arg1_type))
>   		     /* signed_type does not work on pointer types.  */
>   		     && INTEGRAL_TYPE_P (arg1_type))
>   	      {
>
> Looks like it should be resolved one way or the other before the merge.
I have posted a patch to fix this on trunk.   the enclosed patch is 
consistent with that fix.

> --------------------
>
>  From gcse.c:
>
> --- wide-int-base/gcc/gcc/gcse.c	2013-11-05 13:09:32.148376180 +0000
> +++ wide-int/gcc/gcc/gcse.c	2013-11-05 13:07:28.431495118 +0000
> @@ -1997,6 +1997,13 @@ prune_insertions_deletions (int n_elems)
>   	bitmap_clear_bit (pre_delete_map[i], j);
>       }
>   
> +  if (dump_file)
> +    {
> +      dump_bitmap_vector (dump_file, "pre_insert_map", "", pre_insert_map, n_edges);
> +      dump_bitmap_vector (dump_file, "pre_delete_map", "", pre_delete_map,
> +			   last_basic_block);
> +    }
> +
>     sbitmap_free (prune_exprs);
>     free (insertions);
>     free (deletions);
>
> This doesn't look related.
removed
>
> --------------------
>
>  From lcm.c:
>
> diff -udpr '--exclude=.svn' '--exclude=.pc' '--exclude=patches' wide-int-base/gcc/gcc/lcm.c wide-int/gcc/gcc/lcm.c
> --- wide-int-base/gcc/gcc/lcm.c	2013-08-22 09:00:23.068716382 +0100
> +++ wide-int/gcc/gcc/lcm.c	2013-10-26 13:19:16.287277520 +0100
> @@ -64,6 +64,7 @@ along with GCC; see the file COPYING3.
>   #include "sbitmap.h"
>   #include "dumpfile.h"
>   
> +#define LCM_DEBUG_INFO 1
>   /* Edge based LCM routines.  */
>   static void compute_antinout_edge (sbitmap *, sbitmap *, sbitmap *, sbitmap *);
>   static void compute_earliest (struct edge_list *, int, sbitmap *, sbitmap *,
> @@ -106,6 +107,7 @@ compute_antinout_edge (sbitmap *antloc,
>     /* We want a maximal solution, so make an optimistic initialization of
>        ANTIN.  */
>     bitmap_vector_ones (antin, last_basic_block);
> +  bitmap_vector_clear (antout, last_basic_block);
>   
>     /* Put every block on the worklist; this is necessary because of the
>        optimistic initialization of ANTIN above.  */
> @@ -432,6 +434,7 @@ pre_edge_lcm (int n_exprs, sbitmap *tran
>   
>     /* Allocate an extra element for the exit block in the laterin vector.  */
>     laterin = sbitmap_vector_alloc (last_basic_block + 1, n_exprs);
> +  bitmap_vector_clear (laterin, last_basic_block);
>     compute_laterin (edge_list, earliest, antloc, later, laterin);
>   
>   #ifdef LCM_DEBUG_INFO
>
> Same here.
i removed this also.   this was done for the sanity of debugging. but i 
do not think that it is important enough for the trunk.   I assume that 
the code was done this way because it is faster to do this than 
explicitly clear the structures.
>
> --------------------
>
>  From real.c:
>
> @@ -2144,43 +2148,131 @@ real_from_string3 (REAL_VALUE_TYPE *r, c
>       real_convert (r, mode, r);
>   }
>   
> -/* Initialize R from the integer pair HIGH+LOW.  */
> +/* Initialize R from a HOST_WIDE_INT.  */
>   
>   void
>   real_from_integer (REAL_VALUE_TYPE *r, enum machine_mode mode,
> -		   unsigned HOST_WIDE_INT low, HOST_WIDE_INT high,
> -		   int unsigned_p)
> +		   HOST_WIDE_INT val,
> +		   signop sgn)
>   {
> -  if (low == 0 && high == 0)
> +  if (val == 0)
>       get_zero (r, 0);
>     else
>       {
>         memset (r, 0, sizeof (*r));
>         r->cl = rvc_normal;
> -      r->sign = high < 0 && !unsigned_p;
> -      SET_REAL_EXP (r, HOST_BITS_PER_DOUBLE_INT);
> +      r->sign = val < 0 && sgn == SIGNED;
> +      SET_REAL_EXP (r, HOST_BITS_PER_WIDE_INT);
>   
> +      /* TODO: This fails for -MAXHOSTWIDEINT, wide_int version would
> +	 have worked.  */
>         if (r->sign)
> +	val = -val;
>
> Given the TODO, is it really worth having this HOST_WIDE_INT version?
> Wouldn't it be better to have just the wide_int version?
i got rid of this version.    The patch also gets rid of 
REAL_VALUE_FOM_INT since it was a pretty thing interface and just made 
everyone call the wide int version.

> --------------------
>
>  From real.c:
>
> +/* Initialize R from the integer pair HIGH+LOW.  */
> +
> +void
> +real_from_integer (REAL_VALUE_TYPE *r, enum machine_mode mode,
> +		   const wide_int_ref &val_in, signop sgn)
> +{
> +  if (val_in == 0)
> +    get_zero (r, 0);
> +  else
> +    {
> +      unsigned int len = val_in.get_precision ();
> +      int i, j, e=0;
> +      int maxbitlen = MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT;
>
> Why + HOST_BITS_PER_WIDE_INT?  AIUI you want + X so that you can negate
> the largest negative number, but 1 bit should be enough for that.
wide int works faster with precs that are multiples of hwi.
> In case the idea was to get a rounded bitlen, there's no guarantee that
> MAX_BITSIZE_MODE_ANY_INT itself is rounded.
>
> +	  HOST_WIDE_INT cnt_l_z;
> +	  cnt_l_z = wi::clz (val);
> +
> +	  if (maxbitlen - cnt_l_z > realmax)
> +	    {
> +	      e = maxbitlen - cnt_l_z - realmax;
> +
> +	      /* This value is too large, we must shift it right to
> +		 preserve all the bits we can, and then bump the
> +		 exponent up by that amount.  */
> +	      val = wi::lrshift (val, e);
>
> Don't we want a sticky bit for the shifted-out bits, in order to detect
> the 0.5 ULP case properly?
this is something for an fp expert.   what we do here is upwards 
compatible with what was there before. What you are suggesting would be 
more a change.
> --------------------
>
>  From recog.c:
>
> +int
> +const_scalar_int_operand (rtx op, enum machine_mode mode)
> +{
> +  if (!CONST_SCALAR_INT_P (op))
> +    return 0;
> +
> +  if (CONST_INT_P (op))
> +    return const_int_operand (op, mode);
> +
> +  if (mode != VOIDmode)
> +    {
> +      int prec = GET_MODE_PRECISION (mode);
> +      int bitsize = GET_MODE_BITSIZE (mode);
> +
> +      if (CONST_WIDE_INT_NUNITS (op) * HOST_BITS_PER_WIDE_INT > bitsize)
> +	return 0;
> +
> +      if (prec == bitsize)
> +	return 1;
> +      else
> +	{
> +	  /* Multiword partial int.  */
> +	  HOST_WIDE_INT x
> +	    = CONST_WIDE_INT_ELT (op, CONST_WIDE_INT_NUNITS (op) - 1);
> +	  return (sext_hwi (x, prec & (HOST_BITS_PER_WIDE_INT - 1)) == x);
> +	}
> +    }
> +  return 1;
> +}
>
> const_int_operand rejects cases where gen_int_mode (INTVAL (op), mode)
> would give something different from op.  We need to do the equivalent
> for CONST_WIDE_INT too.  (The current CONST_DOUBLE code doesn't bother
> because at the moment the only >HWI mode we support is a 2*HWI one.)
>
> It'd be nice to handle CONST_INT and CONST_WIDE_INT using the same code,
> without going to const_int_operand.
>
> +/* Returns 1 if OP is an operand that is a CONST_WIDE_INT of mode
> +   MODE.  This most likely is not as useful as
> +   const_scalar_int_operand since it does not accept CONST_INTs, but
> +   is here for consistancy.  */
> +int
> +const_wide_int_operand (rtx op, enum machine_mode mode)
> +{
> +  if (!CONST_WIDE_INT_P (op))
> +    return 0;
> +
> +  return const_scalar_int_operand (op, mode);
> +}
>
> Hmm, but have you found any use cases?  Like you say in the comment,
> it just seems wrong to require a CONST_WIDE_INT over a CONST_INT,
> since that's a host-dependent choice.  I think we should drop this
> from the initial merge.
its gone.
> --------------------
>
>  From rtl.c:
>
> +/* Write the wide constant X to OUTFILE.  */
> +
> +void
> +cwi_output_hex (FILE *outfile, const_rtx x)
> +{
> +  int i = CWI_GET_NUM_ELEM (x);
> +  gcc_assert (i > 0);
> +  if (CWI_ELT (x, i-1) == 0)
> +    fprintf (outfile, "0x");
> +  fprintf (outfile, HOST_WIDE_INT_PRINT_HEX, CWI_ELT (x, --i));
> +  while (--i >= 0)
> +    fprintf (outfile, HOST_WIDE_INT_PRINT_PADDED_HEX, CWI_ELT (x, i));
> +}
>
> Why only print "0x" if the top element is 0?  Probably deserves a comment.
it got one
> --------------------
>
>  From tree-cfg.c:
>
> @@ -2698,24 +2700,25 @@ verify_expr (tree *tp, int *walk_subtree
>   
>         if (TREE_CODE (t) == BIT_FIELD_REF)
>   	{
> -	  if (!host_integerp (TREE_OPERAND (t, 1), 1)
> -	      || !host_integerp (TREE_OPERAND (t, 2), 1))
> +	  if (!tree_fits_uhwi_p (TREE_OPERAND (t, 1))
> +	      || !tree_fits_uhwi_p (TREE_OPERAND (t, 2)))
>   	    {
>   	      error ("invalid position or size operand to BIT_FIELD_REF");
>   	      return t;
>   	    }
>   	  if (INTEGRAL_TYPE_P (TREE_TYPE (t))
>   	      && (TYPE_PRECISION (TREE_TYPE (t))
> -		  != TREE_INT_CST_LOW (TREE_OPERAND (t, 1))))
> +		  != tree_to_uhwi (TREE_OPERAND (t, 1))))
>   	    {
>   	      error ("integral result type precision does not match "
>   		     "field size of BIT_FIELD_REF");
>   	      return t;
>   	    }
>   	  else if (!INTEGRAL_TYPE_P (TREE_TYPE (t))
> +		   && !AGGREGATE_TYPE_P (TREE_TYPE (t))
>   		   && TYPE_MODE (TREE_TYPE (t)) != BLKmode
>   		   && (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (t)))
> -		       != TREE_INT_CST_LOW (TREE_OPERAND (t, 1))))
> +		       != tree_to_uhwi (TREE_OPERAND (t, 1))))
>   	    {
>   	      error ("mode precision of non-integral result does not "
>   		     "match field size of BIT_FIELD_REF");
>
> Why the extra !AGGREGATE_TYPE_P test?
this was a merge failure.    it has been removed.
> --------------------
>
>  From tree-vrp.c:
>
> @@ -1893,6 +1884,10 @@ vrp_int_const_binop (enum tree_code code
>       /* If the singed operation wraps then int_const_binop has done
>          everything we want.  */
>       ;
> +  /* Signed division of -1/0 overflows and by the time it gets here
> +     returns NULL_TREE.  */
> +  else if (!res)
> +    return NULL_TREE;
>     else if ((TREE_OVERFLOW (res)
>   	    && !TREE_OVERFLOW (val1)
>   	    && !TREE_OVERFLOW (val2))
>
> Why is this case different from trunk?  Or is it a bug-fix independent
> of wide-int?
this will be handled in a separate set of patches.   I am working on it.
> Thanks,
> Richard
ok to commit?  Bootstrapped and tested on x86-64.


kenny

Some wide-int review comments

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