tree-optimization/112774: extend the SCEV CHREC tree with a nonwrapping flag

The flag is defined as CHREC_NOWRAP(tree), and will be dumped from
"{offset, +, 1}_1" to "{offset, +, 1}<nw>_1" (nw is short for nonwrapping).
Two SCEV interfaces record_nonwrapping_chrec and nonwrapping_chrec_p are
added to set and check the flag respectively.

As resetting the SCEV cache (i.e., the chrec trees) may not reset the
loop->estimate_state, free_numbers_of_iterations_estimates is called
explicitly in loop vectorization to make sure the flag can be
calculated propriately by niter.

gcc/ChangeLog:

	PR tree-optimization/112774
	* tree-pretty-print.cc: if nonwrapping flag is set, chrec will be
	printed with additional <nw> info.
	* tree-scalar-evolution.cc: add record_nonwrapping_chrec and
	nonwrapping_chrec_p to set and check the new flag respectively.
	* tree-scalar-evolution.h: Likewise.
	* tree-ssa-loop-niter.cc (idx_infer_loop_bounds,
	infer_loop_bounds_from_pointer_arith, infer_loop_bounds_from_signedness,
	scev_probably_wraps_p): call record_nonwrapping_chrec before
	record_nonwrapping_iv, call nonwrapping_chrec_p to check the flag is
	set and	return false from scev_probably_wraps_p.
	* tree-vect-loop.cc (vect_analyze_loop): call
	free_numbers_of_iterations_estimates explicitly.
	* tree-core.h: document the nothrow_flag usage in CHREC_NOWRAP
	* tree.h: add CHREC_NOWRAP(NODE), base.nothrow_flag is used to
	represent the nonwrapping info.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/scev-16.c: New test.

1 files changed, 24 insertions, 0 deletions

diff --git a/gcc/tree-scalar-evolution.cc b/gcc/tree-scalar-evolution.cc
index 385fc64..94250b1 100644
--- a/gcc/tree-scalar-evolution.cc
+++ b/gcc/tree-scalar-evolution.cc
@@ -2050,6 +2050,30 @@ analyze_scalar_evolution (class loop *loop, tree var)
   return res;
 }
 
+/* If CHREC doesn't overflow, set the nonwrapping flag.  */
+
+void record_nonwrapping_chrec (tree chrec)
+{
+  CHREC_NOWRAP(chrec) = 1;
+
+  if (dump_file && (dump_flags & TDF_SCEV))
+    {
+      fprintf (dump_file, "(record_nonwrapping_chrec: ");
+      print_generic_expr (dump_file, chrec);
+      fprintf (dump_file, ")\n");
+    }
+}
+
+/* Return true if CHREC's nonwrapping flag is set.  */
+
+bool nonwrapping_chrec_p (tree chrec)
+{
+  if (!chrec || TREE_CODE(chrec) != POLYNOMIAL_CHREC)
+    return false;
+
+  return CHREC_NOWRAP(chrec);
+}
+
 /* Analyzes and returns the scalar evolution of VAR address in LOOP.  */
 
 static tree