re PR tree-optimization/71522 (Wrong optimization of memcpy through a var of type long double)

2016-06-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71522
	* tree-ssa.c (non_rewritable_lvalue_p): Do not rewrite non-float
	copying into float copying.

	* gcc.dg/torture/pr71522.c: New testcase.

From-SVN: r237429

gcc/ChangeLog

+2016-06-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/71522
+	* tree-ssa.c (non_rewritable_lvalue_p): Do not rewrite non-float
+	copying into float copying.
+
 2016-06-14  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/71520

gcc/testsuite/ChangeLog

+2016-06-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/71522
+	* gcc.dg/torture/pr71522.c: New testcase.
+
 2016-06-14  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/71520

gcc/testsuite/gcc.dg/torture/pr71522.c

+/* { dg-do run } */
+
+#if __SIZEOF_LONG_DOUBLE__ == 16
+#define STR "AAAAAAAAAAAAAAA"
+#elif __SIZEOF_LONG_DOUBLE__ == 12
+#define STR "AAAAAAAAAAA"
+#elif __SIZEOF_LONG_DOUBLE__ == 8
+#define STR "AAAAAAA"
+#elif __SIZEOF_LONG_DOUBLE__ == 4
+#define STR "AAA"
+#else
+#define STR "A"
+#endif
+
+int main()
+{
+  long double d;
+  char s[sizeof d];
+
+  __builtin_memcpy(&d, STR, sizeof d);
+  __builtin_memcpy(&s, &d, sizeof s);
+
+  if (__builtin_strncmp (s, STR, sizeof s) != 0)
+    __builtin_abort ();
+
+  return 0;
+}

gcc/tree-ssa.c

@@ -1300,6 +1300,10 @@ non_rewritable_lvalue_p (tree lhs)
 	      || (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
 		  && (TYPE_PRECISION (TREE_TYPE (decl))
 		      >= TYPE_PRECISION (TREE_TYPE (lhs)))))
+	  /* Make sure we are not re-writing non-float copying into float
+	     copying as that can incur normalization.  */
+	  && (! FLOAT_TYPE_P (TREE_TYPE (decl))
+	      || types_compatible_p (TREE_TYPE (lhs), TREE_TYPE (decl)))
 	  && (TREE_THIS_VOLATILE (decl) == TREE_THIS_VOLATILE (lhs)))
 	return false;