tree-chrec.c (convert_affine_scev): New parameter.

* tree-chrec.c (convert_affine_scev): New parameter.  Pass new arg.
	(chrec_convert_1, chrec_convert): Ditto.
	* tree-chrec.h (chrec_convert, convert_affine_scev): New parameter.
	* tree-scalar-evolution.c (interpret_rhs_expr): Pass new arg.
	* tree-vrp.c (adjust_range_with_scev): Ditto.
	* tree-ssa-loop-niter.c (idx_infer_loop_bounds): Ditto.
	(scev_var_range_cant_overflow): New function.
	(scev_probably_wraps_p): New parameter.  Call above function.
	* tree-ssa-loop-niter.h (scev_probably_wraps_p): New parameter.

	gcc/testsuite
	* gcc.dg/tree-ssa/scev-15.c: New.

From-SVN: r238586

gcc/ChangeLog

@@ -1,3 +1,15 @@
+2016-07-21  Bin Cheng  <bin.cheng@arm.com>
+
+	* tree-chrec.c (convert_affine_scev): New parameter.  Pass new arg.
+	(chrec_convert_1, chrec_convert): Ditto.
+	* tree-chrec.h (chrec_convert, convert_affine_scev): New parameter.
+	* tree-scalar-evolution.c (interpret_rhs_expr): Pass new arg.
+	* tree-vrp.c (adjust_range_with_scev): Ditto.
+	* tree-ssa-loop-niter.c (idx_infer_loop_bounds): Ditto.
+	(scev_var_range_cant_overflow): New function.
+	(scev_probably_wraps_p): New parameter.  Call above function.
+	* tree-ssa-loop-niter.h (scev_probably_wraps_p): New parameter.
+
 2016-07-21  Bin Cheng  <bin.cheng@arm.com>
 
 	* tree-ssa-loop-niter.c (number_of_iterations_lt_to_ne): Clean up

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2016-07-21  Bin Cheng  <bin.cheng@arm.com>
+
+	* gcc.dg/tree-ssa/scev-15.c: New.
+
 2016-07-21  Bin Cheng  <bin.cheng@arm.com>
 
 	* gcc.dg/vect/vect-mask-store-move-1.c: XFAIL.

gcc/testsuite/gcc.dg/tree-ssa/scev-15.c

@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-ldist" } */
+
+void
+foo (int *p)
+{
+  unsigned short i, j;
+
+  for (i = 0; i < 100; i++)
+    for (j = 1; j < 101; j++)
+      {
+	unsigned int index = 100 * i + j;
+	p[index-1] = 0;
+      }
+}
+
+/* Loop can be transformed into builtin memset since &p[...] is SCEV.  */
+/* { dg-final { scan-tree-dump "builtin_memset" "ldist" } } */

gcc/tree-chrec.c

@@ -1162,16 +1162,17 @@ nb_vars_in_chrec (tree chrec)
 
 /* Converts BASE and STEP of affine scev to TYPE.  LOOP is the loop whose iv
    the scev corresponds to.  AT_STMT is the statement at that the scev is
-   evaluated.  USE_OVERFLOW_SEMANTICS is true if this function should assume that
+   evaluated.  USE_OVERFLOW_SEMANTICS is true if this function should assume
-   the rules for overflow of the given language apply (e.g., that signed
+   that the rules for overflow of the given language apply (e.g., that signed
-   arithmetics in C does not overflow) -- i.e., to use them to avoid unnecessary
+   arithmetics in C does not overflow) -- i.e., to use them to avoid
-   tests, but also to enforce that the result follows them.  Returns true if the
+   unnecessary tests, but also to enforce that the result follows them.
-   conversion succeeded, false otherwise.  */
+   FROM is the source variable converted if it's not NULL.  Returns true if
+   the conversion succeeded, false otherwise.  */
 
 bool
 convert_affine_scev (struct loop *loop, tree type,
 		     tree *base, tree *step, gimple *at_stmt,
-		     bool use_overflow_semantics)
+		     bool use_overflow_semantics, tree from)
 {
   tree ct = TREE_TYPE (*step);
   bool enforce_overflow_semantics;
@@ -1230,7 +1231,7 @@ convert_affine_scev (struct loop *loop, tree type,
     must_check_rslt_overflow = false;
 
   if (must_check_src_overflow
-      && scev_probably_wraps_p (*base, *step, at_stmt, loop,
+      && scev_probably_wraps_p (from, *base, *step, at_stmt, loop,
 				use_overflow_semantics))
     return false;
 
@@ -1258,7 +1259,8 @@ convert_affine_scev (struct loop *loop, tree type,
   if (must_check_rslt_overflow
       /* Note that in this case we cannot use the fact that signed variables
 	 do not overflow, as this is what we are verifying for the new iv.  */
-      && scev_probably_wraps_p (new_base, new_step, at_stmt, loop, false))
+      && scev_probably_wraps_p (NULL_TREE, new_base, new_step,
+				at_stmt, loop, false))
     return false;
 
   *base = new_base;
@@ -1288,12 +1290,14 @@ chrec_convert_rhs (tree type, tree chrec, gimple *at_stmt)
 
    USE_OVERFLOW_SEMANTICS is true if this function should assume that
    the rules for overflow of the given language apply (e.g., that signed
-   arithmetics in C does not overflow) -- i.e., to use them to avoid unnecessary
+   arithmetics in C does not overflow) -- i.e., to use them to avoid
-   tests, but also to enforce that the result follows them.  */
+   unnecessary tests, but also to enforce that the result follows them.
+
+   FROM is the source variable converted if it's not NULL.  */
 
 static tree
 chrec_convert_1 (tree type, tree chrec, gimple *at_stmt,
-		 bool use_overflow_semantics)
+		 bool use_overflow_semantics, tree from)
 {
   tree ct, res;
   tree base, step;
@@ -1314,7 +1318,7 @@ chrec_convert_1 (tree type, tree chrec, gimple *at_stmt,
   step = CHREC_RIGHT (chrec);
 
   if (convert_affine_scev (loop, type, &base, &step, at_stmt,
-			   use_overflow_semantics))
+			   use_overflow_semantics, from))
     return build_polynomial_chrec (loop->num, base, step);
 
   /* If we cannot propagate the cast inside the chrec, just keep the cast.  */
@@ -1347,7 +1351,7 @@ keep_cast:
 						  CHREC_LEFT (chrec)),
 				    fold_convert (utype,
 						  CHREC_RIGHT (chrec)));
-      res = chrec_convert_1 (type, res, at_stmt, use_overflow_semantics);
+      res = chrec_convert_1 (type, res, at_stmt, use_overflow_semantics, from);
     }
   else
     res = fold_convert (type, chrec);
@@ -1395,14 +1399,16 @@ keep_cast:
 
    USE_OVERFLOW_SEMANTICS is true if this function should assume that
    the rules for overflow of the given language apply (e.g., that signed
-   arithmetics in C does not overflow) -- i.e., to use them to avoid unnecessary
+   arithmetics in C does not overflow) -- i.e., to use them to avoid
-   tests, but also to enforce that the result follows them.  */
+   unnecessary tests, but also to enforce that the result follows them.
+
+   FROM is the source variable converted if it's not NULL.  */
 
 tree
 chrec_convert (tree type, tree chrec, gimple *at_stmt,
-	       bool use_overflow_semantics)
+	       bool use_overflow_semantics, tree from)
 {
-  return chrec_convert_1 (type, chrec, at_stmt, use_overflow_semantics);
+  return chrec_convert_1 (type, chrec, at_stmt, use_overflow_semantics, from);
 }
 
 /* Convert CHREC to TYPE, without regard to signed overflows.  Returns the new

gcc/tree-chrec.h

@@ -59,7 +59,7 @@ enum ev_direction scev_direction (const_tree);
 extern tree chrec_fold_plus (tree, tree, tree);
 extern tree chrec_fold_minus (tree, tree, tree);
 extern tree chrec_fold_multiply (tree, tree, tree);
-extern tree chrec_convert (tree, tree, gimple *, bool = true);
+extern tree chrec_convert (tree, tree, gimple *, bool = true, tree = NULL);
 extern tree chrec_convert_rhs (tree, tree, gimple *);
 extern tree chrec_convert_aggressive (tree, tree, bool *);
 
@@ -75,7 +75,7 @@ extern tree reset_evolution_in_loop (unsigned, tree, tree);
 extern tree chrec_merge (tree, tree);
 extern void for_each_scev_op (tree *, bool (*) (tree *, void *), void *);
 extern bool convert_affine_scev (struct loop *, tree, tree *, tree *, gimple *,
-				 bool);
+				 bool, tree = NULL);
 
 /* Observers.  */
 extern bool eq_evolutions_p (const_tree, const_tree);

gcc/tree-scalar-evolution.c

@@ -1933,7 +1933,7 @@ interpret_rhs_expr (struct loop *loop, gimple *at_stmt,
 	}
       else
 	chrec1 = analyze_scalar_evolution (loop, rhs1);
-      res = chrec_convert (type, chrec1, at_stmt);
+      res = chrec_convert (type, chrec1, at_stmt, true, rhs1);
       break;
 
     case BIT_AND_EXPR:

gcc/tree-ssa-loop-niter.c

@@ -3128,7 +3128,8 @@ idx_infer_loop_bounds (tree base, tree *idx, void *dta)
   /* If access is not executed on every iteration, we must ensure that overlow
      may not make the access valid later.  */
   if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt))
-      && scev_probably_wraps_p (initial_condition_in_loop_num (ev, loop->num),
+      && scev_probably_wraps_p (NULL_TREE,
+				initial_condition_in_loop_num (ev, loop->num),
 				step, data->stmt, loop, true))
     upper = false;
 
@@ -4191,6 +4192,104 @@ loop_exits_before_overflow (tree base, tree step,
   return false;
 }
 
+/* VAR is scev variable whose evolution part is constant STEP, this function
+   proves that VAR can't overflow by using value range info.  If VAR's value
+   range is [MIN, MAX], it can be proven by:
+     MAX + step doesn't overflow    ; if step > 0
+   or
+     MIN + step doesn't underflow   ; if step < 0.
+
+   We can only do this if var is computed in every loop iteration, i.e, var's
+   definition has to dominate loop latch.  Consider below example:
+
+     {
+       unsigned int i;
+
+       <bb 3>:
+
+       <bb 4>:
+       # RANGE [0, 4294967294] NONZERO 65535
+       # i_21 = PHI <0(3), i_18(9)>
+       if (i_21 != 0)
+	 goto <bb 6>;
+       else
+	 goto <bb 8>;
+
+       <bb 6>:
+       # RANGE [0, 65533] NONZERO 65535
+       _6 = i_21 + 4294967295;
+       # RANGE [0, 65533] NONZERO 65535
+       _7 = (long unsigned int) _6;
+       # RANGE [0, 524264] NONZERO 524280
+       _8 = _7 * 8;
+       # PT = nonlocal escaped
+       _9 = a_14 + _8;
+       *_9 = 0;
+
+       <bb 8>:
+       # RANGE [1, 65535] NONZERO 65535
+       i_18 = i_21 + 1;
+       if (i_18 >= 65535)
+	 goto <bb 10>;
+       else
+	 goto <bb 9>;
+
+       <bb 9>:
+       goto <bb 4>;
+
+       <bb 10>:
+       return;
+     }
+
+   VAR _6 doesn't overflow only with pre-condition (i_21 != 0), here we
+   can't use _6 to prove no-overlfow for _7.  In fact, var _7 takes value
+   sequence (4294967295, 0, 1, ..., 65533) in loop life time, rather than
+   (4294967295, 4294967296, ...).  */
+
+static bool
+scev_var_range_cant_overflow (tree var, tree step, struct loop *loop)
+{
+  tree type;
+  wide_int minv, maxv, diff, step_wi;
+  enum value_range_type rtype;
+
+  if (TREE_CODE (step) != INTEGER_CST || !INTEGRAL_TYPE_P (TREE_TYPE (var)))
+    return false;
+
+  /* Check if VAR evaluates in every loop iteration.  It's not the case
+     if VAR is default definition or does not dominate loop's latch.  */
+  basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (var));
+  if (!def_bb || !dominated_by_p (CDI_DOMINATORS, loop->latch, def_bb))
+    return false;
+
+  rtype = get_range_info (var, &minv, &maxv);
+  if (rtype != VR_RANGE)
+    return false;
+
+  /* VAR is a scev whose evolution part is STEP and value range info
+     is [MIN, MAX], we can prove its no-overflowness by conditions:
+
+       type_MAX - MAX >= step   ; if step > 0
+       MIN - type_MIN >= |step| ; if step < 0.
+
+     Or VAR must take value outside of value range, which is not true.  */
+  step_wi = step;
+  type = TREE_TYPE (var);
+  if (tree_int_cst_sign_bit (step))
+    {
+      diff = lower_bound_in_type (type, type);
+      diff = minv - diff;
+      step_wi = - step_wi;
+    }
+  else
+    {
+      diff = upper_bound_in_type (type, type);
+      diff = diff - maxv;
+    }
+
+  return (wi::geu_p (diff, step_wi));
+}
+
 /* Return false only when the induction variable BASE + STEP * I is
    known to not overflow: i.e. when the number of iterations is small
    enough with respect to the step and initial condition in order to
@@ -4199,10 +4298,13 @@ loop_exits_before_overflow (tree base, tree step,
 
    USE_OVERFLOW_SEMANTICS is true if this function should assume that
    the rules for overflow of the given language apply (e.g., that signed
-   arithmetics in C does not overflow).  */
+   arithmetics in C does not overflow).
+
+   If VAR is a ssa variable, this function also returns false if VAR can
+   be proven not overflow with value range info.  */
 
 bool
-scev_probably_wraps_p (tree base, tree step,
+scev_probably_wraps_p (tree var, tree base, tree step,
 		       gimple *at_stmt, struct loop *loop,
 		       bool use_overflow_semantics)
 {
@@ -4239,6 +4341,11 @@ scev_probably_wraps_p (tree base, tree step,
   if (TREE_CODE (step) != INTEGER_CST)
     return true;
 
+  /* Check if var can be proven not overflow with value range info.  */
+  if (var && TREE_CODE (var) == SSA_NAME
+      && scev_var_range_cant_overflow (var, step, loop))
+    return false;
+
   if (loop_exits_before_overflow (base, step, at_stmt, loop))
     return false;
 

gcc/tree-ssa-loop-niter.h

@@ -49,7 +49,8 @@ extern bool estimated_stmt_executions (struct loop *, widest_int *);
 extern void estimate_numbers_of_iterations (void);
 extern bool stmt_dominates_stmt_p (gimple *, gimple *);
 extern bool nowrap_type_p (tree);
-extern bool scev_probably_wraps_p (tree, tree, gimple *, struct loop *, bool);
+extern bool scev_probably_wraps_p (tree, tree, tree, gimple *,
+				   struct loop *, bool);
 extern void free_loop_control_ivs (struct loop *);
 extern void free_numbers_of_iterations_estimates_loop (struct loop *);
 extern void free_numbers_of_iterations_estimates (function *);

gcc/tree-vrp.c

@@ -4156,8 +4156,8 @@ adjust_range_with_scev (value_range *vr, struct loop *loop,
 	 or decreases,  ... */
       dir == EV_DIR_UNKNOWN
       /* ... or if it may wrap.  */
-      || scev_probably_wraps_p (init, step, stmt, get_chrec_loop (chrec),
+      || scev_probably_wraps_p (NULL_TREE, init, step, stmt,
-				true))
+				get_chrec_loop (chrec), true))
     return;
 
   /* We use TYPE_MIN_VALUE and TYPE_MAX_VALUE here instead of