gnu: gcc: Adjust 'strmov' patch for string constants in variables.

Fixes <https://bugs.gnu.org/30395>.

* gnu/packages/patches/gcc-strmov-store-file-names.patch: Update patch
to deal with string constants stored in 'static' variables.

gnu/packages/patches/gcc-strmov-store-file-names.patch

@@ -2,23 +2,43 @@ Make sure that statements such as:
 
   strcpy (dst, "/gnu/store/…");
 
+or
+
+  static const char str[] = "/gnu/store/…";
+  …
+  strcpy (dst, str);
+
 do not result in chunked /gnu/store strings that are undetectable by
-Guix's GC and its grafting code.  See <http://bugs.gnu.org/24703>.
+Guix's GC and its grafting code.  See <https://bugs.gnu.org/24703>
+and <https://bugs.gnu.org/30395>.
+
 
 --- gcc-5.3.0/gcc/builtins.c	2016-10-18 10:50:46.080616285 +0200
 +++ gcc-5.3.0/gcc/builtins.c	2016-11-09 15:26:43.693042737 +0100
-@@ -3192,6 +3192,42 @@ determine_block_size (tree len, rtx len_
+@@ -3192,6 +3192,54 @@ determine_block_size (tree len, rtx len_
  			  GET_MODE_MASK (GET_MODE (len_rtx)));
  }
  
++extern void debug_tree (tree);
++
 +/* Return true if STR contains the string "/gnu/store".  */
 +
-+static bool
++bool
 +store_reference_p (tree str)
 +{
++  if (getenv ("GUIX_GCC_DEBUG") != NULL)
++    debug_tree (str);
++
 +  if (TREE_CODE (str) == ADDR_EXPR)
 +    str = TREE_OPERAND (str, 0);
 +
++  if (TREE_CODE (str) == VAR_DECL
++      && TREE_STATIC (str)
++      && TREE_READONLY (str))
++    /* STR may be a 'static const' variable whose initial value
++       is a string constant.  See <https://bugs.gnu.org/30395>.  */
++    str = DECL_INITIAL (str);
++
 +  if (TREE_CODE (str) != STRING_CST)
 +    return false;
 +
@@ -57,10 +77,32 @@ Guix's GC and its grafting code.  See <http://bugs.gnu.org/24703>.
 +  /* Do not emit block moves, which translate to the 'movabs' instruction on
 +     x86_64, when SRC refers to store items.  That way, store references
 +     remain visible to the Guix GC and grafting code.  See
-+     <http://bugs.gnu.org/24703>.  */
++     <https://bugs.gnu.org/24703>.  */
 +  if (store_reference_p (src))
 +    return NULL_RTX;
 +
    /* If DEST is not a pointer type, call the normal function.  */
    if (dest_align == 0)
      return NULL_RTX;
+
+--- gcc-5.5.0/gcc/gimple-fold.c	2018-03-20 11:36:16.709442004 +0100
++++ gcc-5.5.0/gcc/gimple-fold.c	2018-03-20 11:46:43.838487065 +0100
+@@ -769,6 +769,8 @@ var_decl_component_p (tree var)
+   return SSA_VAR_P (inner);
+ }
+ 
++extern bool store_reference_p (tree);
++
+ /* Fold function call to builtin mem{{,p}cpy,move}.  Return
+    false if no simplification can be made.
+    If ENDP is 0, return DEST (like memcpy).
+@@ -1099,6 +1101,9 @@ gimple_fold_builtin_memory_op (gimple_st
+       if (!srctype)
+ 	return false;
+ 
++      if (store_reference_p (src))
++        return false;
++
+       src_align = get_pointer_alignment (src);
+       dest_align = get_pointer_alignment (dest);
+       if (dest_align < TYPE_ALIGN (desttype)