Avoid generating useless range info

[Aldy Hernandez <aldyh@redhat.com>]

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Hi!

As discovered in my range class work, we seem to generate a significant 
amount of useless range info out of VRP.

Is there any reason why we can't avoid generating any range info that 
spans the entire domain, and yet contains nothing in the non-zero bitmask?

The attached patch passes bootstrap, and the one regression it causes is 
because now the -Walloca-larger-than= pass is better able to determine 
that there is no range information at all, and the testcase is 
unbounded.  So...win, win.

OK for trunk?

Aldy

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gcc/

	* tree-vrp.c (vrp_finalize): Do not expose any useless range
	information.

gcc/testsuite/

	* gcc.dg/Walloca-14.c: Adapt test to recognize new complaint of
	unbounded use.

diff --git a/gcc/testsuite/gcc.dg/Walloca-14.c b/gcc/testsuite/gcc.dg/Walloca-14.c
index 723dbe5..f3e3f57 100644
--- a/gcc/testsuite/gcc.dg/Walloca-14.c
+++ b/gcc/testsuite/gcc.dg/Walloca-14.c
@@ -9,5 +9,6 @@ g (int *p)
   extern void f (void *);
 
   void *q = __builtin_alloca (p); /* { dg-warning "passing argument 1" } */
+  /* { dg-warning "unbounded use of 'alloca'" "unbounded" { target *-*-* } 11 } */
   f (q);
 }
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 716a7c2..8442b1f 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -10708,8 +10708,24 @@ vrp_finalize (bool warn_array_bounds_p)
 					      vr_value[i]->max) == 1)))
 	  set_ptr_nonnull (name);
 	else if (!POINTER_TYPE_P (TREE_TYPE (name)))
-	  set_range_info (name, vr_value[i]->type, vr_value[i]->min,
-			  vr_value[i]->max);
+	  {
+	    range_info_def *ri = SSA_NAME_RANGE_INFO (name);
+	    tree type = TREE_TYPE (name);
+	    unsigned precision = TYPE_PRECISION (type);
+	    /* If the range covers the entire domain and there is
+	       nothing in the non-zero bits mask, there is no sense in
+	       storing anything.  */
+	    if (vr_value[i]->min == TYPE_MIN_VALUE (type)
+		&& vr_value[i]->max == TYPE_MAX_VALUE (type)
+		&& vr_value[i]->type == VR_RANGE
+		&& (!ri
+		    || ri->get_nonzero_bits () == wi::shwi (-1, precision)))
+	      SSA_NAME_RANGE_INFO (name) = NULL;
+	    else
+	      set_range_info (name, vr_value[i]->type, vr_value[i]->min,
+			      vr_value[i]->max);
+	  }
+}
       }
 
   substitute_and_fold (op_with_constant_singleton_value_range, vrp_fold_stmt);