Found one (the?) ARM bug: (Pointer) aliasing issues

[Iain Buclaw]

On 3 November 2013 10:20, Johannes Pfau <nospam at example.com> wrote:

> Am Sun, 3 Nov 2013 02:10:20 +0000
> schrieb Iain Buclaw <ibuclaw at ubuntu.com>:
>
> > last time I
> > checked, returning 0 disables aliasing rules from taking effect.
>
> That should work. Alias set 0 is a special alias set which conflicts
> with everything. I'll check if it works as expected.
>


This is taken from hunks in the 2.064 merge I'm testing:

Pastebin link here:  http://pastebin.com/jxQQL68N


diff --git a/gcc/d/d-lang.cc b/gcc/d/d-lang.cc
index 8cba369..a19a59b 100644
--- a/gcc/d/d-lang.cc
+++ b/gcc/d/d-lang.cc
@@ -73,6 +73,7 @@ const attribute_spec d_attribute_table[] =
 #undef LANG_HOOKS_COMMON_ATTRIBUTE_TABLE
 #undef LANG_HOOKS_ATTRIBUTE_TABLE
 #undef LANG_HOOKS_FORMAT_ATTRIBUTE_TABLE
+#undef LANG_HOOKS_GET_ALIAS_SET
 #undef LANG_HOOKS_TYPES_COMPATIBLE_P
 #undef LANG_HOOKS_BUILTIN_FUNCTION
 #undef LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE
@@ -95,6 +96,7 @@ const attribute_spec d_attribute_table[] =
 #define LANG_HOOKS_COMMON_ATTRIBUTE_TABLE       d_builtins_attribute_table
 #define LANG_HOOKS_ATTRIBUTE_TABLE              d_attribute_table
 #define LANG_HOOKS_FORMAT_ATTRIBUTE_TABLE      d_format_attribute_table
+#define LANG_HOOKS_GET_ALIAS_SET               d_get_alias_set
 #define LANG_HOOKS_TYPES_COMPATIBLE_P          d_types_compatible_p
 #define LANG_HOOKS_BUILTIN_FUNCTION            d_builtin_function
 #define LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE  d_builtin_function
@@ -1505,6 +1523,33 @@ d_getdecls (void)
 }


+// Get the alias set corresponding to a type or expression.
+// Return -1 if we don't do anything special.
+
+static alias_set_type
+d_get_alias_set (tree t)
+{
+  if (!TYPE_P (t))
+    return get_alias_set (TREE_TYPE (t));
+
+  Type *dtype = build_dtype (t);
+
+  // If the type is a dynamic array, use the alias set of the basetype.
+  if (dtype && dtype->ty == Tarray)
+    return get_alias_set (dtype->nextOf()->toCtype());
+
+  // Permit type-punning when accessing a union, provided the access
+  // is directly through the union.
+  for (tree u = t; handled_component_p (u); u = TREE_OPERAND (u, 0))
+    {
+      if (TREE_CODE (u) == COMPONENT_REF
+         && TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
+       return 0;
+    }
+
+  return -1;
+}
+
 static int
 d_types_compatible_p (tree t1, tree t2)
 {




-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';
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