re PR tree-optimization/71055 (FAIL: gcc.dg/torture/pr53663-1.c -Os execution test)

2016-05-11  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71055
	* tree-ssa-sccvn.c (vn_reference_lookup_3): When native-interpreting
	sth with precision not equal to access size verify we don't chop
	off bits.

	* gcc.dg/torture/pr71055.c: New testcase.

From-SVN: r236122

gcc/ChangeLog

 2016-05-11  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71055
+	* tree-ssa-sccvn.c (vn_reference_lookup_3): When native-interpreting
+	sth with precision not equal to access size verify we don't chop
+	off bits.
+
+2016-05-11  Richard Biener  <rguenther@suse.de>
+
 	PR debug/71057
 	* dwarf2out.c (retry_incomplete_types): Set early_dwarf.
 	(dwarf2out_finish): Move retry_incomplete_types call ...

gcc/testsuite/ChangeLog

 2016-05-11  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71055
+	* gcc.dg/torture/pr71055.c: New testcase.
+
+2016-05-11  Richard Biener  <rguenther@suse.de>
+
 	PR debug/71057
 	* g++.dg/debug/pr71057.C: New testcase.
 

gcc/testsuite/gcc.dg/torture/pr71055.c

+/* { dg-do run } */
+
+extern void abort (void);
+union U { int i; _Bool b; char c; };
+void __attribute__((noinline,noclone))
+foo (union U *u)
+{
+  if (u->c != 0)
+    abort ();
+}
+int main()
+{
+  union U u;
+  u.i = 10;
+  u.b = 0;
+  foo (&u);
+  return 0;
+}

gcc/tree-ssa-sccvn.c

@@ -1907,14 +1907,34 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
 				    buffer, sizeof (buffer));
 	  if (len > 0)
 	    {
-	      tree val = native_interpret_expr (vr->type,
+	      tree type = vr->type;
+	      /* Make sure to interpret in a type that has a range
+	         covering the whole access size.  */
+	      if (INTEGRAL_TYPE_P (vr->type)
+		  && ref->size != TYPE_PRECISION (vr->type))
+		type = build_nonstandard_integer_type (ref->size,
+						       TYPE_UNSIGNED (type));
+	      tree val = native_interpret_expr (type,
 						buffer
 						+ ((offset - offset2)
 						   / BITS_PER_UNIT),
 						ref->size / BITS_PER_UNIT);
+	      /* If we chop off bits because the types precision doesn't
+		 match the memory access size this is ok when optimizing
+		 reads but not when called from the DSE code during
+		 elimination.  */
+	      if (val
+		  && type != vr->type)
+		{
+		  if (! int_fits_type_p (val, vr->type))
+		    val = NULL_TREE;
+		  else
+		    val = fold_convert (vr->type, val);
+		}
+
 	      if (val)
 		return vn_reference_lookup_or_insert_for_pieces
-		         (vuse, vr->set, vr->type, vr->operands, val);
+			 (vuse, vr->set, vr->type, vr->operands, val);
 	    }
 	}
     }