Hello,
We have a somewhat long-recognized problem with LTO vs. symbols referenced
in inline asm statements. For extended asms, the solution is easy: just
mention the symbol in constraints. For toplevel asms, this is trickier, as
they cannot have constraints.
I think a good solution for toplevel asms would be to give users a way to
add '__attribute__((used))' to symbols referenced in toplevel asms, e.g.:
#include <foo.h>
__attribute__((used))
__typeof(foo) foo;
asm("foo");
If 'foo' has a definition in this translation unit, this already works.
Let's make this work in LTO if 'foo' is defined in some other TU.
The only problem seems to be that the 'force_output' decl flag is reset
prior to LTO streaming just because pre-WPA that node is external. I'm
not sure it's actually necessary.
Does the following patch look reasonable? Bootstrapped/regrested on x86-64.
Thanks.
Alexander
* ipa-visibility.c (function_and_variable_visibility): Do not reset
node->force_output.
diff --git a/gcc/ipa-visibility.c b/gcc/ipa-visibility.c
index a82852b3ce4..caa9d420c82 100644
--- a/gcc/ipa-visibility.c
+++ b/gcc/ipa-visibility.c
@@ -672,10 +672,7 @@ function_and_variable_visibility (bool whole_program)
is finished. We may end up marking as node external nodes
where this flag is meaningless strip it. */
if (DECL_EXTERNAL (node->decl) || !node->definition)
- {
- node->force_output = 0;
- node->forced_by_abi = 0;
- }
+ node->forced_by_abi = 0;
/* C++ FE on lack of COMDAT support create local COMDAT functions
(that ought to be shared but can not due to object format
