While following GCC's handling of 'volatile' and other type
qualifiers, I noticed that the gimplify pass created temporaries
with a type with 'volatile' asserted if the underlying type also
had 'volatile' asserted.
Temporaries are created by the create_tmp_var_raw() procedure
in gimplify.c, which reads as follows:
tree
create_tmp_var_raw (tree type, const char *prefix)
{
tree tmp_var;
tree new_type;
/* Make the type of the variable writable. */
new_type = build_type_variant (type, 0, 0);
TYPE_ATTRIBUTES (new_type) = TYPE_ATTRIBUTES (type);
tmp_var = build_decl (VAR_DECL, prefix ? create_tmp_var_name (prefix) :
NULL,
type);
[...]
Note above that an unqualified type, new_type, is created but
then subsequently not used in the call to build_decl. Because of
this omission, if 'type' originally had any qualifiers set
(such as volatile), they'll be propagated to the temporary, which
might have some unexpected effects on subsequent optimizations
and code generation.
The fix, I think, is to pass 'new_type':
Index: gimplify.c
===================================================================
--- gimplify.c (revision 113552)
+++ gimplify.c (working copy)
@@ -449,7 +449,7 @@
TYPE_ATTRIBUTES (new_type) = TYPE_ATTRIBUTES (type);
tmp_var = build_decl (VAR_DECL, prefix ? create_tmp_var_name (prefix) :
NULL,
- type);
+ new_type);
/* The variable was declared by the compiler. */
DECL_ARTIFICIAL (tmp_var) = 1;
(If this analysis is correct and it is recommended that I file a
bug report on this, or post a patch, please let me know.)
