libLTO is exposing a very “stable” (in the sense of immutable) C API to be used by linkers (and binutils tools) that manipulate bitcode (like when performing LTO).
I’m looking into relaxing the stability concern and design a policy for this API that would allow to deprecate and remove some the APIs exposed here. The MacOS linker (ld64) is one the users of libLTO, but there are others (Sony? Qualcomm? Anyone else?) that I think are also targeting this API.
I’d like to identify stakeholders so that we can establish a new policy that would accomodate everyone as much as possible. So if you care about the libLTO C API, please speak-up!
Sorry for the delayed reply I was out on vacation for that last few days.
As Pete Cooper already commented, the Apple cctools project (aka the “binutils” stuff), make use of the libLTO C API.
At this time do you want to know an exact list of each API in use? It is not clear from your email below exactly what you are after at this point in time other than to identify who are the stakeholders. On that I do care about the libLTO C API so we don’t break the uses in the Apple cctools project.
From: mehdi.amini at apple.com [mailto:mehdi.amini at apple.com]
Sent: Friday, September 30, 2016 1:19 PM
I’d like to identify stakeholders so that we can establish a
new policy that would accomodate everyone as much as possible.
So if you care about the libLTO C API, please speak-up!
Hi Mehdi,
Apologies, I missed this thread. Thanks for pinging James Molloy
who made me aware of it.
ARM Compiler 6 [1] ships with a home-grown linker (armlink) that
makes use of libLTO and its C API to enable the LTO functionality
in this product.
The installation of the product comes with the libLTO binary and
the only supported use case is to use armlink and libLTO from the
same installation. This means that deprecation and later removing
some functions should not bring us much trouble as long there is
a reasonable window that allows us to update our code to use
newer APIs.
The following is a list of functions that the linker currently
uses:
* lto_get_error_message(),
* lto_module_create_in_local_context(),
* lto_module_create_in_codegen_context(),
* lto_module_dispose(),
* lto_module_get_num_symbols(),
* lto_module_get_symbol_name(),
* lto_module_get_symbol_attribute(),
* lto_codegen_set_diagnostic_handler(),
* lto_codegen_create(),
* lto_codegen_dispose(),
* lto_codegen_add_module(),
* lto_codegen_set_pic_model(),
* lto_codegen_set_cpu(),
* lto_codegen_add_must_preserve_symbol(),
* lto_codegen_compile(),
* lto_codegen_compile_to_file(),
* lto_codegen_debug_options().
Just saw the recent replies to this old thread, so just as an FYI... We (QuIC Hexagon and ARM) are moving away from libLTO and are anticipating to complete the move to the C++ API imminently, so I don't have any particular concerns about backward compatibility of the C API on our side.
