[PATCH] Fix PR71522

[Richard Biener]

I am testing the following to fix PR71522.

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

Richard.

2016-06-14  Richard Biener  <rguent...@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.

Index: gcc/tree-ssa.c
===================================================================
*** gcc/tree-ssa.c      (revision 237426)
--- gcc/tree-ssa.c      (working copy)
*************** non_rewritable_lvalue_p (tree lhs)
*** 1300,1305 ****
--- 1328,1337 ----
              || (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;
  
Index: gcc/testsuite/gcc.dg/torture/pr71522.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr71522.c      (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr71522.c      (working copy)
***************
*** 0 ****
--- 1,27 ----
+ /* { 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;
+ }