Support <, <=, > and >= for offset_int and widest_int

offset_int and widest_int are supposed to be at least one bit wider
than all the values they need to represent, with the extra bits
being signs.  Thus offset_int is effectively int128_t and widest_int
is effectively intNNN_t, for target-dependent NNN.

Because the types are signed, there's not really any need to specify
a sign for operations like comparison.  I think things would be clearer
if we supported <, <=, > and >= for them (but not for wide_int, which
doesn't have a sign).

Tested on x86_64-linux-gnu and aarch64-linux-gnu.

gcc/
	* wide-int.h: Update offset_int and widest_int documentation.
	(WI_SIGNED_BINARY_PREDICATE_RESULT): New macro.
	(wi::binary_traits): Allow ordered comparisons between offset_int and
	offset_int, between widest_int and widest_int, and between either
	of these types and basic C types.
	(operator <, <=, >, >=): Define for the same combinations.
	* tree.h (tree_int_cst_lt): Use comparison operators instead
	of wi:: comparisons.
	(tree_int_cst_le): Likewise.
	* gimple-fold.c (fold_array_ctor_reference): Likewise.
	(fold_nonarray_ctor_reference): Likewise.
	* gimple-ssa-strength-reduction.c (record_increment): Likewise.
	* tree-affine.c (aff_comb_cannot_overlap_p): Likewise.
	* tree-parloops.c (try_transform_to_exit_first_loop_alt): Likewise.
	* tree-sra.c (completely_scalarize): Likewise.
	* tree-ssa-alias.c (stmt_kills_ref_p): Likewise.
	* tree-ssa-reassoc.c (extract_bit_test_mask): Likewise.
	* tree-vrp.c (extract_range_from_binary_expr_1): Likewise.
	(check_for_binary_op_overflow): Likewise.
	(search_for_addr_array): Likewise.
	* ubsan.c (ubsan_expand_objsize_ifn): Likewise.

From-SVN: r235719

12 files changed, 97 insertions, 46 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b3edd2a..acc6b79 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,27 @@
+2016-05-02  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* wide-int.h: Update offset_int and widest_int documentation.
+	(WI_SIGNED_BINARY_PREDICATE_RESULT): New macro.
+	(wi::binary_traits): Allow ordered comparisons between offset_int and
+	offset_int, between widest_int and widest_int, and between either
+	of these types and basic C types.
+	(operator <, <=, >, >=): Define for the same combinations.
+	* tree.h (tree_int_cst_lt): Use comparison operators instead
+	of wi:: comparisons.
+	(tree_int_cst_le): Likewise.
+	* gimple-fold.c (fold_array_ctor_reference): Likewise.
+	(fold_nonarray_ctor_reference): Likewise.
+	* gimple-ssa-strength-reduction.c (record_increment): Likewise.
+	* tree-affine.c (aff_comb_cannot_overlap_p): Likewise.
+	* tree-parloops.c (try_transform_to_exit_first_loop_alt): Likewise.
+	* tree-sra.c (completely_scalarize): Likewise.
+	* tree-ssa-alias.c (stmt_kills_ref_p): Likewise.
+	* tree-ssa-reassoc.c (extract_bit_test_mask): Likewise.
+	* tree-vrp.c (extract_range_from_binary_expr_1): Likewise.
+	(check_for_binary_op_overflow): Likewise.
+	(search_for_addr_array): Likewise.
+	* ubsan.c (ubsan_expand_objsize_ifn): Likewise.
+
 2016-05-02  Claudiu Zissulescu  <claziss@synopsys.com>
 
 	* config/arc/arc.c (arc_preferred_simd_mode): Remove enum keyword.
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 6cd0a4b..6ed72dc 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -5380,7 +5380,7 @@ fold_array_ctor_reference (tree type, tree ctor,
      be larger than size of array element.  */
   if (!TYPE_SIZE_UNIT (type)
       || TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST
-      || wi::lts_p (elt_size, wi::to_offset (TYPE_SIZE_UNIT (type)))
+      || elt_size < wi::to_offset (TYPE_SIZE_UNIT (type))
       || elt_size == 0)
     return NULL_TREE;
 
@@ -5457,7 +5457,7 @@ fold_nonarray_ctor_reference (tree type, tree ctor,
 	     fields.  */
 	  if (wi::cmps (access_end, bitoffset_end) > 0)
 	    return NULL_TREE;
-	  if (wi::lts_p (offset, bitoffset))
+	  if (offset < bitoffset)
 	    return NULL_TREE;
 	  return fold_ctor_reference (type, cval,
 				      inner_offset.to_uhwi (), size,
diff --git a/gcc/gimple-ssa-strength-reduction.c b/gcc/gimple-ssa-strength-reduction.c
index 46ee7a7..b235151 100644
--- a/gcc/gimple-ssa-strength-reduction.c
+++ b/gcc/gimple-ssa-strength-reduction.c
@@ -2506,8 +2506,7 @@ record_increment (slsr_cand_t c, widest_int increment, bool is_phi_adjust)
       if (c->kind == CAND_ADD
 	  && !is_phi_adjust
 	  && c->index == increment
-	  && (wi::gts_p (increment, 1)
-	      || wi::lts_p (increment, -1))
+	  && (increment > 1 || increment < -1)
 	  && (gimple_assign_rhs_code (c->cand_stmt) == PLUS_EXPR
 	      || gimple_assign_rhs_code (c->cand_stmt) == POINTER_PLUS_EXPR))
 	{
diff --git a/gcc/tree-affine.c b/gcc/tree-affine.c
index 4251a5b..32f2301 100644
--- a/gcc/tree-affine.c
+++ b/gcc/tree-affine.c
@@ -929,7 +929,7 @@ aff_comb_cannot_overlap_p (aff_tree *diff, const widest_int &size1,
   else
     {
       /* We succeed if the second object starts after the first one ends.  */
-      return wi::les_p (size1, diff->offset);
+      return size1 <= diff->offset;
     }
 }
 
diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c
index 2e55b79..25a29bd 100644
--- a/gcc/tree-parloops.c
+++ b/gcc/tree-parloops.c
@@ -1868,7 +1868,7 @@ try_transform_to_exit_first_loop_alt (struct loop *loop,
 
   /* Check if nit + 1 overflows.  */
   widest_int type_max = wi::to_widest (TYPE_MAXVAL (nit_type));
-  if (!wi::lts_p (nit_max, type_max))
+  if (nit_max >= type_max)
     return false;
 
   gimple *def = SSA_NAME_DEF_STMT (nit);
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 6fafe55..936d3a6 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -1055,7 +1055,7 @@ completely_scalarize (tree base, tree decl_type, HOST_WIDE_INT offset, tree ref)
 		idx = wi::sext (idx, TYPE_PRECISION (domain));
 		max = wi::sext (max, TYPE_PRECISION (domain));
 	      }
-	    for (int el_off = offset; wi::les_p (idx, max); ++idx)
+	    for (int el_off = offset; idx <= max; ++idx)
 	      {
 		tree nref = build4 (ARRAY_REF, elemtype,
 				    ref,
diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index f801b01..4ffefaf 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -2440,10 +2440,10 @@ stmt_kills_ref_p (gimple *stmt, ao_ref *ref)
 		  rbase = TREE_OPERAND (rbase, 0);
 		}
 	      if (base == rbase
-		  && wi::les_p (offset, roffset)
-		  && wi::les_p (roffset + ref->max_size,
-				offset + wi::lshift (wi::to_offset (len),
-						     LOG2_BITS_PER_UNIT)))
+		  && offset <= roffset
+		  && (roffset + ref->max_size
+		      <= offset + wi::lshift (wi::to_offset (len),
+					      LOG2_BITS_PER_UNIT)))
 		return true;
 	      break;
 	    }
diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c
index d23dabd..7408977 100644
--- a/gcc/tree-ssa-reassoc.c
+++ b/gcc/tree-ssa-reassoc.c
@@ -2464,7 +2464,7 @@ extract_bit_test_mask (tree exp, int prec, tree totallow, tree low, tree high,
 		return NULL_TREE;
 	      bias = wi::to_widest (tbias);
 	      bias -= wi::to_widest (totallow);
-	      if (wi::ges_p (bias, 0) && wi::lts_p (bias, prec - max))
+	      if (bias >= 0 && bias < prec - max)
 		{
 		  *mask = wi::lshift (*mask, bias);
 		  return ret;
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 3cb470b..4cd1ab3 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -2749,17 +2749,17 @@ extract_range_from_binary_expr_1 (value_range *vr,
 	  /* Sort the 4 products so that min is in prod0 and max is in
 	     prod3.  */
 	  /* min0min1 > max0max1 */
-	  if (wi::gts_p (prod0, prod3))
+	  if (prod0 > prod3)
 	    std::swap (prod0, prod3);
 
 	  /* min0max1 > max0min1 */
-	  if (wi::gts_p (prod1, prod2))
+	  if (prod1 > prod2)
 	    std::swap (prod1, prod2);
 
-	  if (wi::gts_p (prod0, prod1))
+	  if (prod0 > prod1)
 	    std::swap (prod0, prod1);
 
-	  if (wi::gts_p (prod2, prod3))
+	  if (prod2 > prod3)
 	    std::swap (prod2, prod3);
 
 	  /* diff = max - min.  */
@@ -3775,7 +3775,7 @@ check_for_binary_op_overflow (enum tree_code subcode, tree type,
       /* If all values in [wmin, wmax] are smaller than
 	 [wtmin, wtmax] or all are larger than [wtmin, wtmax],
 	 the arithmetic operation will always overflow.  */
-      if (wi::lts_p (wmax, wtmin) || wi::gts_p (wmin, wtmax))
+      if (wmax < wtmin || wmin > wtmax)
 	return true;
       return false;
     }
@@ -6587,7 +6587,7 @@ search_for_addr_array (tree t, location_t location)
 
       idx = mem_ref_offset (t);
       idx = wi::sdiv_trunc (idx, wi::to_offset (el_sz));
-      if (wi::lts_p (idx, 0))
+      if (idx < 0)
 	{
 	  if (dump_file && (dump_flags & TDF_DETAILS))
 	    {
@@ -6599,8 +6599,8 @@ search_for_addr_array (tree t, location_t location)
 		      "array subscript is below array bounds");
 	  TREE_NO_WARNING (t) = 1;
 	}
-      else if (wi::gts_p (idx, (wi::to_offset (up_bound)
-				- wi::to_offset (low_bound) + 1)))
+      else if (idx > (wi::to_offset (up_bound)
+		      - wi::to_offset (low_bound) + 1))
 	{
 	  if (dump_file && (dump_flags & TDF_DETAILS))
 	    {
diff --git a/gcc/tree.h b/gcc/tree.h
index 259a2bf..aa76f50 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -5318,7 +5318,7 @@ wi::max_value (const_tree type)
 inline bool
 tree_int_cst_lt (const_tree t1, const_tree t2)
 {
-  return wi::lts_p (wi::to_widest (t1), wi::to_widest (t2));
+  return wi::to_widest (t1) < wi::to_widest (t2);
 }
 
 /* Return true if INTEGER_CST T1 is less than or equal to INTEGER_CST T2,
@@ -5327,7 +5327,7 @@ tree_int_cst_lt (const_tree t1, const_tree t2)
 inline bool
 tree_int_cst_le (const_tree t1, const_tree t2)
 {
-  return wi::les_p (wi::to_widest (t1), wi::to_widest (t2));
+  return wi::to_widest (t1) <= wi::to_widest (t2);
 }
 
 /* Returns -1 if T1 < T2, 0 if T1 == T2, and 1 if T1 > T2.  T1 and T2
diff --git a/gcc/ubsan.c b/gcc/ubsan.c
index d3fbfd1..802341e 100644
--- a/gcc/ubsan.c
+++ b/gcc/ubsan.c
@@ -911,8 +911,8 @@ ubsan_expand_objsize_ifn (gimple_stmt_iterator *gsi)
     /* Yes, __builtin_object_size couldn't determine the
        object size.  */;
   else if (TREE_CODE (offset) == INTEGER_CST
-	   && wi::ges_p (wi::to_widest (offset), -OBJSZ_MAX_OFFSET)
-	   && wi::les_p (wi::to_widest (offset), -1))
+	   && wi::to_widest (offset) >= -OBJSZ_MAX_OFFSET
+	   && wi::to_widest (offset) <= -1)
     /* The offset is in range [-16K, -1].  */;
   else
     {
@@ -928,8 +928,8 @@ ubsan_expand_objsize_ifn (gimple_stmt_iterator *gsi)
       /* If the offset is small enough, we don't need the second
 	 run-time check.  */
       if (TREE_CODE (offset) == INTEGER_CST
-	  && wi::ges_p (wi::to_widest (offset), 0)
-	  && wi::les_p (wi::to_widest (offset), OBJSZ_MAX_OFFSET))
+	  && wi::to_widest (offset) >= 0
+	  && wi::to_widest (offset) <= OBJSZ_MAX_OFFSET)
 	*gsi = gsi_after_labels (then_bb);
       else
 	{
diff --git a/gcc/wide-int.h b/gcc/wide-int.h
index fa133f0..b1dfcff 100644
--- a/gcc/wide-int.h
+++ b/gcc/wide-int.h
@@ -53,22 +53,26 @@ along with GCC; see the file COPYING3.  If not see
      multiply, division, shifts, comparisons, and operations that need
      overflow detected), the signedness must be specified separately.
 
-     2) offset_int.  This is a fixed size representation that is
-     guaranteed to be large enough to compute any bit or byte sized
-     address calculation on the target.  Currently the value is 64 + 4
-     bits rounded up to the next number even multiple of
-     HOST_BITS_PER_WIDE_INT (but this can be changed when the first
-     port needs more than 64 bits for the size of a pointer).
-
-     This flavor can be used for all address math on the target.  In
-     this representation, the values are sign or zero extended based
-     on their input types to the internal precision.  All math is done
-     in this precision and then the values are truncated to fit in the
-     result type.  Unlike most gimple or rtl intermediate code, it is
-     not useful to perform the address arithmetic at the same
-     precision in which the operands are represented because there has
-     been no effort by the front ends to convert most addressing
-     arithmetic to canonical types.
+     2) offset_int.  This is a fixed-precision integer that can hold
+     any address offset, measured in either bits or bytes, with at
+     least one extra sign bit.  At the moment the maximum address
+     size GCC supports is 64 bits.  With 8-bit bytes and an extra
+     sign bit, offset_int therefore needs to have at least 68 bits
+     of precision.  We round this up to 128 bits for efficiency.
+     Values of type T are converted to this precision by sign- or
+     zero-extending them based on the signedness of T.
+
+     The extra sign bit means that offset_int is effectively a signed
+     128-bit integer, i.e. it behaves like int128_t.
+
+     Since the values are logically signed, there is no need to
+     distinguish between signed and unsigned operations.  Sign-sensitive
+     comparison operators <, <=, > and >= are therefore supported.
+
+     [ Note that, even though offset_int is effectively int128_t,
+       it can still be useful to use unsigned comparisons like
+       wi::leu_p (a, b) as a more efficient short-hand for
+       "a >= 0 && a <= b". ]
 
      3) widest_int.  This representation is an approximation of
      infinite precision math.  However, it is not really infinite
@@ -76,9 +80,9 @@ along with GCC; see the file COPYING3.  If not see
      precision math where the precision is 4 times the size of the
      largest integer that the target port can represent.
 
-     widest_int is supposed to be wider than any number that it needs to
-     store, meaning that there is always at least one leading sign bit.
-     All widest_int values are therefore signed.
+     Like offset_int, widest_int is wider than all the values that
+     it needs to represent, so the integers are logically signed.
+     Sign-sensitive comparison operators <, <=, > and >= are supported.
 
      There are several places in the GCC where this should/must be used:
 
@@ -255,6 +259,12 @@ along with GCC; see the file COPYING3.  If not see
 #define WI_BINARY_RESULT(T1, T2) \
   typename wi::binary_traits <T1, T2>::result_type
 
+/* The type of result produced by a signed binary predicate on types T1 and T2.
+   This is bool if signed comparisons make sense for T1 and T2 and leads to
+   substitution failure otherwise.  */
+#define WI_SIGNED_BINARY_PREDICATE_RESULT(T1, T2) \
+  typename wi::binary_traits <T1, T2>::signed_predicate_result
+
 /* The type of result produced by a unary operation on type T.  */
 #define WI_UNARY_RESULT(T) \
   typename wi::unary_traits <T>::result_type
@@ -316,7 +326,7 @@ namespace wi
     VAR_PRECISION,
 
     /* The integer has a constant precision (known at GCC compile time)
-       but no defined signedness.  */
+       and is signed.  */
     CONST_PRECISION
   };
 
@@ -379,6 +389,7 @@ namespace wi
        so as not to confuse gengtype.  */
     typedef generic_wide_int < fixed_wide_int_storage
 			       <int_traits <T2>::precision> > result_type;
+    typedef bool signed_predicate_result;
   };
 
   template <typename T1, typename T2>
@@ -394,6 +405,7 @@ namespace wi
        so as not to confuse gengtype.  */
     typedef generic_wide_int < fixed_wide_int_storage
 			       <int_traits <T1>::precision> > result_type;
+    typedef bool signed_predicate_result;
   };
 
   template <typename T1, typename T2>
@@ -404,6 +416,7 @@ namespace wi
     STATIC_ASSERT (int_traits <T1>::precision == int_traits <T2>::precision);
     typedef generic_wide_int < fixed_wide_int_storage
 			       <int_traits <T1>::precision> > result_type;
+    typedef bool signed_predicate_result;
   };
 
   template <typename T1, typename T2>
@@ -3050,6 +3063,21 @@ wi::min_precision (const T &x, signop sgn)
     return get_precision (x) - clz (x);
 }
 
+#define SIGNED_BINARY_PREDICATE(OP, F)			\
+  template <typename T1, typename T2>			\
+    inline WI_SIGNED_BINARY_PREDICATE_RESULT (T1, T2)	\
+    OP (const T1 &x, const T2 &y)			\
+    {							\
+      return wi::F (x, y);				\
+    }
+
+SIGNED_BINARY_PREDICATE (operator <, lts_p)
+SIGNED_BINARY_PREDICATE (operator <=, les_p)
+SIGNED_BINARY_PREDICATE (operator >, gts_p)
+SIGNED_BINARY_PREDICATE (operator >=, ges_p)
+
+#undef SIGNED_BINARY_PREDICATE
+
 template<typename T>
 void
 gt_ggc_mx (generic_wide_int <T> *)