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Require wi::to_wide for trees


One of the original requirements for getting wide-int.h accepted
was that it should work efficiently on trees.  Through a process
that I no longer recall exactly, this ended up meaning that we can
use things like:

   wi::add (t, 1)

to add 1 to an INTEGER_CST T in its native precision.  However, we also have:

   wi::to_offset (t)      // Treat T as an offset_int
   wi::to_widest (t)      // Treat T as a widest_int

Recently we also gained:

   wi::to_wide (t, prec)  // Treat T as a wide_int in preccision PREC

I'd like to revisit the decision to treat "wide_int trees" differently.
Requiring:

   wi::to_wide (t)

would be just as efficient, and would make it clearer that a deliberate
choice is being made to treat the tree as a wide_int in its native
precision.  This also removes the inconsistency that

a) wide_int trees can be used without an accessor but must use wi::
   functions instead of C++ operators

b) the other forms need an explicit accessor but the result can be used
   with C++ operators.

It also helps with SVE, where there's the additional possibility
that the tree could be a runtime value.

Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu.
Also tested by comparing the testsuite assembly output on at least one
target per CPU directory.  OK to install?

If so, it might make sense to use wi::to_wide (rtx, mode) for rtxes too.

Richard


2017-10-03  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* wide-int.h (wide_int_ref_storage): Make host_dependent_precision
	a template parameter.
	(WIDE_INT_REF_FOR): Update accordingly.
	* tree.h (wi::int_traits <const_tree>): Delete.
	(wi::tree_to_widest_ref, wi::tree_to_offset_ref): New typedefs.
	(wi::to_widest, wi::to_offset): Use them.  Expand commentary.
	(wi::tree_to_wide_ref): New typedef.
	(wi::to_wide): New function.
	* calls.c (get_size_range): Use wi::to_wide when operating on
	trees as wide_ints.
	* cgraph.c (cgraph_node::create_thunk): Likewise.
	* config/i386/i386.c (ix86_data_alignment): Likewise.
	(ix86_local_alignment): Likewise.
	* dbxout.c (stabstr_O): Likewise.
	* dwarf2out.c (add_scalar_info, gen_enumeration_type_die): Likewise.
	* expr.c (const_vector_from_tree): Likewise.
	* fold-const-call.c (host_size_t_cst_p, fold_const_call_1): Likewise.
	* fold-const.c (may_negate_without_overflow_p, negate_expr_p)
	(fold_negate_expr_1, int_const_binop_1, const_binop)
	(fold_convert_const_int_from_real, optimize_bit_field_compare)
	(all_ones_mask_p, sign_bit_p, build_range_check, unextend)
	(extract_muldiv_1, fold_div_compare, fold_single_bit_test)
	(fold_plusminus_mult_expr, pointer_may_wrap_p, expr_not_equal_to)
	(fold_binary_loc, fold_ternary_loc, multiple_of_p, fold_negate_const)
	(fold_abs_const, fold_not_const, round_up_loc): Likewise.
	* gimple-fold.c (gimple_fold_indirect_ref): Likewise.
	* gimple-ssa-warn-alloca.c (alloca_call_type_by_arg): Likewise.
	(alloca_call_type): Likewise.
	* gimple.c (preprocess_case_label_vec_for_gimple): Likewise.
	* godump.c (go_output_typedef): Likewise.
	* graphite-sese-to-poly.c (tree_int_to_gmp): Likewise.
	* internal-fn.c (get_min_precision): Likewise.
	* ipa-cp.c (ipcp_store_vr_results): Likewise.
	* ipa-polymorphic-call.c
	(ipa_polymorphic_call_context::ipa_polymorphic_call_context): Likewise.
	* ipa-prop.c (ipa_print_node_jump_functions_for_edge): Likewise.
	(ipa_modify_call_arguments): Likewise.
	* match.pd: Likewise.
	* omp-low.c (scan_omp_1_op, lower_omp_ordered_clauses): Likewise.
	* print-tree.c (print_node_brief, print_node): Likewise.
	* stmt.c (expand_case): Likewise.
	* stor-layout.c (layout_type): Likewise.
	* tree-affine.c (tree_to_aff_combination): Likewise.
	* tree-cfg.c (group_case_labels_stmt): Likewise.
	* tree-data-ref.c (dr_analyze_indices): Likewise.
	(prune_runtime_alias_test_list): Likewise.
	* tree-dump.c (dequeue_and_dump): Likewise.
	* tree-inline.c (remap_gimple_op_r, copy_tree_body_r): Likewise.
	* tree-predcom.c (is_inv_store_elimination_chain): Likewise.
	* tree-pretty-print.c (dump_generic_node): Likewise.
	* tree-scalar-evolution.c (iv_can_overflow_p): Likewise.
	(simple_iv_with_niters): Likewise.
	* tree-ssa-address.c (addr_for_mem_ref): Likewise.
	* tree-ssa-ccp.c (ccp_finalize, evaluate_stmt): Likewise.
	* tree-ssa-loop-ivopts.c (constant_multiple_of): Likewise.
	* tree-ssa-loop-niter.c (split_to_var_and_offset)
	(refine_value_range_using_guard, number_of_iterations_ne_max)
	(number_of_iterations_lt_to_ne, number_of_iterations_lt)
	(get_cst_init_from_scev, record_nonwrapping_iv)
	(scev_var_range_cant_overflow): Likewise.
	* tree-ssa-phiopt.c (minmax_replacement): Likewise.
	* tree-ssa-pre.c (compute_avail): Likewise.
	* tree-ssa-sccvn.c (vn_reference_fold_indirect): Likewise.
	(vn_reference_maybe_forwprop_address, valueized_wider_op): Likewise.
	* tree-ssa-structalias.c (get_constraint_for_ptr_offset): Likewise.
	* tree-ssa-uninit.c (is_pred_expr_subset_of): Likewise.
	* tree-ssanames.c (set_nonzero_bits, get_nonzero_bits): Likewise.
	* tree-switch-conversion.c (collect_switch_conv_info, array_value_type)
	(dump_case_nodes, try_switch_expansion): Likewise.
	* tree-vect-loop-manip.c (vect_gen_vector_loop_niters): Likewise.
	(vect_do_peeling): Likewise.
	* tree-vect-patterns.c (vect_recog_bool_pattern): Likewise.
	* tree-vect-stmts.c (vectorizable_load): Likewise.
	* tree-vrp.c (compare_values_warnv, vrp_int_const_binop): Likewise.
	(zero_nonzero_bits_from_vr, ranges_from_anti_range): Likewise.
	(extract_range_from_binary_expr_1, adjust_range_with_scev): Likewise.
	(overflow_comparison_p_1, register_edge_assert_for_2): Likewise.
	(is_masked_range_test, find_switch_asserts, maybe_set_nonzero_bits)
	(vrp_evaluate_conditional_warnv_with_ops, intersect_ranges): Likewise.
	(range_fits_type_p, two_valued_val_range_p, vrp_finalize): Likewise.
	(evrp_dom_walker::before_dom_children): Likewise.
	* tree.c (cache_integer_cst, real_value_from_int_cst, integer_zerop)
	(integer_all_onesp, integer_pow2p, integer_nonzerop, tree_log2)
	(tree_floor_log2, tree_ctz, mem_ref_offset, tree_int_cst_sign_bit)
	(tree_int_cst_sgn, get_unwidened, int_fits_type_p): Likewise.
	(get_type_static_bounds, num_ending_zeros, drop_tree_overflow)
	(get_range_pos_neg): Likewise.
	* ubsan.c (ubsan_expand_ptr_ifn): Likewise.
	* config/darwin.c (darwin_mergeable_constant_section): Likewise.
	* config/aarch64/aarch64.c (aapcs_vfp_sub_candidate): Likewise.
	* config/arm/arm.c (aapcs_vfp_sub_candidate): Likewise.
	* config/avr/avr.c (avr_fold_builtin): Likewise.
	* config/bfin/bfin.c (bfin_local_alignment): Likewise.
	* config/msp430/msp430.c (msp430_attr): Likewise.
	* config/nds32/nds32.c (nds32_insert_attributes): Likewise.
	* config/powerpcspe/powerpcspe-c.c
	(altivec_resolve_overloaded_builtin): Likewise.
	* config/powerpcspe/powerpcspe.c (rs6000_aggregate_candidate)
	(rs6000_expand_ternop_builtin): Likewise.
	* config/rs6000/rs6000-c.c
	(altivec_resolve_overloaded_builtin): Likewise.
	* config/rs6000/rs6000.c (rs6000_aggregate_candidate): Likewise.
	(rs6000_expand_ternop_builtin): Likewise.
	* config/s390/s390.c (s390_handle_hotpatch_attribute): Likewise.

gcc/ada/
	* gcc-interface/decl.c (annotate_value): Use wi::to_wide when
	operating on trees as wide_ints.

gcc/c/
	* c-parser.c (c_parser_cilk_clause_vectorlength): Use wi::to_wide when
	operating on trees as wide_ints.
	* c-typeck.c (build_c_cast, c_finish_omp_clauses): Likewise.
	(c_tree_equal): Likewise.

gcc/c-family/
	* c-ada-spec.c (dump_generic_ada_node): Use wi::to_wide when
	operating on trees as wide_ints.
	* c-common.c (pointer_int_sum): Likewise.
	* c-pretty-print.c (pp_c_integer_constant): Likewise.
	* c-warn.c (match_case_to_enum_1): Likewise.
	(c_do_switch_warnings): Likewise.
	(maybe_warn_shift_overflow): Likewise.

gcc/cp/
	* cvt.c (ignore_overflows): Use wi::to_wide when
	operating on trees as wide_ints.
	* decl.c (check_array_designated_initializer): Likewise.
	* mangle.c (write_integer_cst): Likewise.
	* semantics.c (cp_finish_omp_clause_depend_sink): Likewise.

gcc/fortran/
	* target-memory.c (gfc_interpret_logical): Use wi::to_wide when
	operating on trees as wide_ints.
	* trans-const.c (gfc_conv_tree_to_mpz): Likewise.
	* trans-expr.c (gfc_conv_cst_int_power): Likewise.
	* trans-intrinsic.c (trans_this_image): Likewise.
	(gfc_conv_intrinsic_bound): Likewise.
	(conv_intrinsic_cobound): Likewise.

gcc/lto/
	* lto.c (compare_tree_sccs_1): Use wi::to_wide when
	operating on trees as wide_ints.

gcc/objc/
	* objc-act.c (objc_decl_method_attributes): Use wi::to_wide when
	operating on trees as wide_ints.

Index: gcc/wide-int.h
===================================================================
*** gcc/wide-int.h	2017-10-03 19:57:02.809678461 +0100
--- gcc/wide-int.h	2017-10-03 19:57:03.680691854 +0100
*************** #define WIDE_INT_H
*** 150,164 ****
     and in wider precisions.
  
     There are constructors to create the various forms of wide_int from
!    trees, rtl and constants.  For trees you can simply say:
  
  	     tree t = ...;
! 	     wide_int x = t;
  
!    However, a little more syntax is required for rtl constants since
!    they do not have an explicit precision.  To make an rtl into a
!    wide_int, you have to pair it with a mode.  The canonical way to do
!    this is with rtx_mode_t as in:
  
  	     rtx r = ...
  	     wide_int x = rtx_mode_t (r, mode);
--- 150,172 ----
     and in wider precisions.
  
     There are constructors to create the various forms of wide_int from
!    trees, rtl and constants.  For trees the options are:
  
  	     tree t = ...;
! 	     wi::to_wide (t)     // Treat T as a wide_int
! 	     wi::to_offset (t)   // Treat T as an offset_int
! 	     wi::to_widest (t)   // Treat T as a widest_int
! 
!    All three are light-weight accessors that should have no overhead
!    in release builds.  If it is useful for readability reasons to
!    store the result in a temporary variable, the preferred method is:
! 
! 	     wi::tree_to_wide_ref twide = wi::to_wide (t);
! 	     wi::tree_to_offset_ref toffset = wi::to_offset (t);
! 	     wi::tree_to_widest_ref twidest = wi::to_widest (t);
  
!    To make an rtx into a wide_int, you have to pair it with a mode.
!    The canonical way to do this is with rtx_mode_t as in:
  
  	     rtx r = ...
  	     wide_int x = rtx_mode_t (r, mode);
*************** #define WIDE_INT_H
*** 175,197 ****
  	     offset_int x = (int) c;          // sign-extend C
  	     widest_int x = (unsigned int) c; // zero-extend C
  
!    It is also possible to do arithmetic directly on trees, rtxes and
     constants.  For example:
  
! 	     wi::add (t1, t2);	  // add equal-sized INTEGER_CSTs t1 and t2
! 	     wi::add (t1, 1);     // add 1 to INTEGER_CST t1
! 	     wi::add (r1, r2);    // add equal-sized rtx constants r1 and r2
  	     wi::lshift (1, 100); // 1 << 100 as a widest_int
  
     Many binary operations place restrictions on the combinations of inputs,
     using the following rules:
  
!    - {tree, rtx, wide_int} op {tree, rtx, wide_int} -> wide_int
         The inputs must be the same precision.  The result is a wide_int
         of the same precision
  
!    - {tree, rtx, wide_int} op (un)signed HOST_WIDE_INT -> wide_int
!      (un)signed HOST_WIDE_INT op {tree, rtx, wide_int} -> wide_int
         The HOST_WIDE_INT is extended or truncated to the precision of
         the other input.  The result is a wide_int of the same precision
         as that input.
--- 183,204 ----
  	     offset_int x = (int) c;          // sign-extend C
  	     widest_int x = (unsigned int) c; // zero-extend C
  
!    It is also possible to do arithmetic directly on rtx_mode_ts and
     constants.  For example:
  
! 	     wi::add (r1, r2);    // add equal-sized rtx_mode_ts r1 and r2
! 	     wi::add (r1, 1);     // add 1 to rtx_mode_t r1
  	     wi::lshift (1, 100); // 1 << 100 as a widest_int
  
     Many binary operations place restrictions on the combinations of inputs,
     using the following rules:
  
!    - {rtx, wide_int} op {rtx, wide_int} -> wide_int
         The inputs must be the same precision.  The result is a wide_int
         of the same precision
  
!    - {rtx, wide_int} op (un)signed HOST_WIDE_INT -> wide_int
!      (un)signed HOST_WIDE_INT op {rtx, wide_int} -> wide_int
         The HOST_WIDE_INT is extended or truncated to the precision of
         the other input.  The result is a wide_int of the same precision
         as that input.
*************** typedef generic_wide_int <wide_int_stora
*** 316,322 ****
  typedef FIXED_WIDE_INT (ADDR_MAX_PRECISION) offset_int;
  typedef FIXED_WIDE_INT (WIDE_INT_MAX_PRECISION) widest_int;
  
! template <bool SE>
  struct wide_int_ref_storage;
  
  typedef generic_wide_int <wide_int_ref_storage <false> > wide_int_ref;
--- 323,331 ----
  typedef FIXED_WIDE_INT (ADDR_MAX_PRECISION) offset_int;
  typedef FIXED_WIDE_INT (WIDE_INT_MAX_PRECISION) widest_int;
  
! /* wi::storage_ref can be a reference to a primitive type,
!    so this is the conservatively-correct setting.  */
! template <bool SE, bool HDP = true>
  struct wide_int_ref_storage;
  
  typedef generic_wide_int <wide_int_ref_storage <false> > wide_int_ref;
*************** typedef generic_wide_int <wide_int_ref_s
*** 330,336 ****
     to use those.  */
  #define WIDE_INT_REF_FOR(T) \
    generic_wide_int \
!     <wide_int_ref_storage <wi::int_traits <T>::is_sign_extended> >
  
  namespace wi
  {
--- 339,346 ----
     to use those.  */
  #define WIDE_INT_REF_FOR(T) \
    generic_wide_int \
!     <wide_int_ref_storage <wi::int_traits <T>::is_sign_extended, \
! 			   wi::int_traits <T>::host_dependent_precision> >
  
  namespace wi
  {
*************** decompose (HOST_WIDE_INT *, unsigned int
*** 929,935 ****
  /* Provide the storage for a wide_int_ref.  This acts like a read-only
     wide_int, with the optimization that VAL is normally a pointer to
     another integer's storage, so that no array copy is needed.  */
! template <bool SE>
  struct wide_int_ref_storage : public wi::storage_ref
  {
  private:
--- 939,945 ----
  /* Provide the storage for a wide_int_ref.  This acts like a read-only
     wide_int, with the optimization that VAL is normally a pointer to
     another integer's storage, so that no array copy is needed.  */
! template <bool SE, bool HDP>
  struct wide_int_ref_storage : public wi::storage_ref
  {
  private:
*************** struct wide_int_ref_storage : public wi:
*** 948,955 ****
  };
  
  /* Create a reference from an existing reference.  */
! template <bool SE>
! inline wide_int_ref_storage <SE>::
  wide_int_ref_storage (const wi::storage_ref &x)
    : storage_ref (x)
  {}
--- 958,965 ----
  };
  
  /* Create a reference from an existing reference.  */
! template <bool SE, bool HDP>
! inline wide_int_ref_storage <SE, HDP>::
  wide_int_ref_storage (const wi::storage_ref &x)
    : storage_ref (x)
  {}
*************** wide_int_ref_storage (const wi::storage_
*** 957,988 ****
  /* Create a reference to integer X in its natural precision.  Note
     that the natural precision is host-dependent for primitive
     types.  */
! template <bool SE>
  template <typename T>
! inline wide_int_ref_storage <SE>::wide_int_ref_storage (const T &x)
    : storage_ref (wi::int_traits <T>::decompose (scratch,
  						wi::get_precision (x), x))
  {
  }
  
  /* Create a reference to integer X in precision PRECISION.  */
! template <bool SE>
  template <typename T>
! inline wide_int_ref_storage <SE>::wide_int_ref_storage (const T &x,
! 							unsigned int precision)
    : storage_ref (wi::int_traits <T>::decompose (scratch, precision, x))
  {
  }
  
  namespace wi
  {
!   template <bool SE>
!   struct int_traits <wide_int_ref_storage <SE> >
    {
      static const enum precision_type precision_type = VAR_PRECISION;
!     /* wi::storage_ref can be a reference to a primitive type,
!        so this is the conservatively-correct setting.  */
!     static const bool host_dependent_precision = true;
      static const bool is_sign_extended = SE;
    };
  }
--- 967,996 ----
  /* Create a reference to integer X in its natural precision.  Note
     that the natural precision is host-dependent for primitive
     types.  */
! template <bool SE, bool HDP>
  template <typename T>
! inline wide_int_ref_storage <SE, HDP>::wide_int_ref_storage (const T &x)
    : storage_ref (wi::int_traits <T>::decompose (scratch,
  						wi::get_precision (x), x))
  {
  }
  
  /* Create a reference to integer X in precision PRECISION.  */
! template <bool SE, bool HDP>
  template <typename T>
! inline wide_int_ref_storage <SE, HDP>::
! wide_int_ref_storage (const T &x, unsigned int precision)
    : storage_ref (wi::int_traits <T>::decompose (scratch, precision, x))
  {
  }
  
  namespace wi
  {
!   template <bool SE, bool HDP>
!   struct int_traits <wide_int_ref_storage <SE, HDP> >
    {
      static const enum precision_type precision_type = VAR_PRECISION;
!     static const bool host_dependent_precision = HDP;
      static const bool is_sign_extended = SE;
    };
  }
Index: gcc/tree.h
===================================================================
*** gcc/tree.h	2017-10-03 19:57:02.809678461 +0100
--- gcc/tree.h	2017-10-03 19:57:03.678792572 +0100
*************** extern bool anon_aggrname_p (const_tree)
*** 5120,5139 ****
  /* The tree and const_tree overload templates.   */
  namespace wi
  {
-   template <>
-   struct int_traits <const_tree>
-   {
-     static const enum precision_type precision_type = VAR_PRECISION;
-     static const bool host_dependent_precision = false;
-     static const bool is_sign_extended = false;
-     static unsigned int get_precision (const_tree);
-     static wi::storage_ref decompose (HOST_WIDE_INT *, unsigned int,
- 				      const_tree);
-   };
- 
-   template <>
-   struct int_traits <tree> : public int_traits <const_tree> {};
- 
    template <int N>
    class extended_tree
    {
--- 5120,5125 ----
*************** extern bool anon_aggrname_p (const_tree)
*** 5157,5198 ****
      static const unsigned int precision = N;
    };
  
!   generic_wide_int <extended_tree <WIDE_INT_MAX_PRECISION> >
!   to_widest (const_tree);
! 
!   generic_wide_int <extended_tree <ADDR_MAX_PRECISION> > to_offset (const_tree);
! 
    wide_int to_wide (const_tree, unsigned int);
  }
  
! inline unsigned int
! wi::int_traits <const_tree>::get_precision (const_tree tcst)
! {
!   return TYPE_PRECISION (TREE_TYPE (tcst));
! }
  
! /* Convert the tree_cst X into a wide_int of PRECISION.  */
! inline wi::storage_ref
! wi::int_traits <const_tree>::decompose (HOST_WIDE_INT *,
! 					unsigned int precision, const_tree x)
! {
!   gcc_checking_assert (precision == TYPE_PRECISION (TREE_TYPE (x)));
!   return wi::storage_ref (&TREE_INT_CST_ELT (x, 0), TREE_INT_CST_NUNITS (x),
! 			  precision);
! }
  
! inline generic_wide_int <wi::extended_tree <WIDE_INT_MAX_PRECISION> >
  wi::to_widest (const_tree t)
  {
    return t;
  }
  
! inline generic_wide_int <wi::extended_tree <ADDR_MAX_PRECISION> >
  wi::to_offset (const_tree t)
  {
    return t;
  }
  
  /* Convert INTEGER_CST T to a wide_int of precision PREC, extending or
     truncating as necessary.  When extending, use sign extension if T's
     type is signed and zero extension if T's type is unsigned.  */
--- 5143,5257 ----
      static const unsigned int precision = N;
    };
  
!   typedef const generic_wide_int <extended_tree <WIDE_INT_MAX_PRECISION> >
!     tree_to_widest_ref;
!   typedef const generic_wide_int <extended_tree <ADDR_MAX_PRECISION> >
!     tree_to_offset_ref;
!   typedef const generic_wide_int<wide_int_ref_storage<false, false> >
!     tree_to_wide_ref;
! 
!   tree_to_widest_ref to_widest (const_tree);
!   tree_to_offset_ref to_offset (const_tree);
!   tree_to_wide_ref to_wide (const_tree);
    wide_int to_wide (const_tree, unsigned int);
  }
  
! /* Refer to INTEGER_CST T as though it were a widest_int.
  
!    This function gives T's actual numerical value, influenced by the
!    signedness of its type.  For example, a signed byte with just the
!    top bit set would be -128 while an unsigned byte with the same
!    bit pattern would be 128.
! 
!    This is the right choice when operating on groups of INTEGER_CSTs
!    that might have different signedness or precision.  It is also the
!    right choice in code that specifically needs an approximation of
!    infinite-precision arithmetic instead of normal modulo arithmetic.
! 
!    The approximation of infinite precision is good enough for realistic
!    numbers of additions and subtractions of INTEGER_CSTs (where
!    "realistic" includes any number less than 1 << 31) but it cannot
!    represent the result of multiplying the two largest supported
!    INTEGER_CSTs.  The overflow-checking form of wi::mul provides a way
!    of multiplying two arbitrary INTEGER_CSTs and checking that the
!    result is representable as a widest_int.
! 
!    Note that any overflow checking done on these values is relative to
!    the range of widest_int rather than the range of a TREE_TYPE.
! 
!    Calling this function should have no overhead in release builds,
!    so it is OK to call it several times for the same tree.  If it
!    useful for readability reasons to reduce the number of calls,
!    it is more efficient to use:
! 
!      wi::tree_to_widest_ref wt = wi::to_widest (t);
! 
!    instead of:
  
!      widest_int wt = wi::to_widest (t).  */
! 
! inline wi::tree_to_widest_ref
  wi::to_widest (const_tree t)
  {
    return t;
  }
  
! /* Refer to INTEGER_CST T as though it were an offset_int.
! 
!    This function is an optimisation of wi::to_widest for cases
!    in which T is known to be a bit or byte count in the range
!    (-(2 ^ (N + BITS_PER_UNIT)), 2 ^ (N + BITS_PER_UNIT)), where N is
!    the target's address size in bits.
! 
!    This is the right choice when operating on bit or byte counts as
!    untyped numbers rather than M-bit values.  The wi::to_widest comments
!    about addition, subtraction and multiplication apply here: sequences
!    of 1 << 31 additions and subtractions do not induce overflow, but
!    multiplying the largest sizes might.  Again,
! 
!      wi::tree_to_offset_ref wt = wi::to_offset (t);
! 
!    is more efficient than:
! 
!      offset_int wt = wi::to_offset (t).  */
! 
! inline wi::tree_to_offset_ref
  wi::to_offset (const_tree t)
  {
    return t;
  }
  
+ /* Refer to INTEGER_CST T as though it were a wide_int.
+ 
+    In contrast to the approximation of infinite-precision numbers given
+    by wi::to_widest and wi::to_offset, this function treats T as a
+    signless collection of N bits, where N is the precision of T's type.
+    As with machine registers, signedness is determined by the operation
+    rather than the operands; for example, there is a distinction between
+    signed and unsigned division.
+ 
+    This is the right choice when operating on values with the same type
+    using normal modulo arithmetic.  The overflow-checking forms of things
+    like wi::add check whether the result can be represented in T's type.
+ 
+    Calling this function should have no overhead in release builds,
+    so it is OK to call it several times for the same tree.  If it
+    useful for readability reasons to reduce the number of calls,
+    it is more efficient to use:
+ 
+      wi::tree_to_wide_ref wt = wi::to_wide (t);
+ 
+    instead of:
+ 
+      wide_int wt = wi::to_wide (t).  */
+ 
+ inline wi::tree_to_wide_ref
+ wi::to_wide (const_tree t)
+ {
+   return wi::storage_ref (&TREE_INT_CST_ELT (t, 0), TREE_INT_CST_NUNITS (t),
+ 			  TYPE_PRECISION (TREE_TYPE (t)));
+ }
+ 
  /* Convert INTEGER_CST T to a wide_int of precision PREC, extending or
     truncating as necessary.  When extending, use sign extension if T's
     type is signed and zero extension if T's type is unsigned.  */
*************** wi::to_offset (const_tree t)
*** 5200,5206 ****
  inline wide_int
  wi::to_wide (const_tree t, unsigned int prec)
  {
!   return wide_int::from (t, prec, TYPE_SIGN (TREE_TYPE (t)));
  }
  
  template <int N>
--- 5259,5265 ----
  inline wide_int
  wi::to_wide (const_tree t, unsigned int prec)
  {
!   return wide_int::from (wi::to_wide (t), prec, TYPE_SIGN (TREE_TYPE (t)));
  }
  
  template <int N>

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