Add API to LTOCodeGenerator to specify a strategy for the -internalize
pass.

This is a new attempt at Bill's change in r185882, which he reverted in
r188029 due to problems with the gold linker.  This puts the onus on the
linker to decide whether (and what) to internalize.

In particular, running internalize before outputting an object file may
change a 'weak' symbol into an internal one, even though that symbol
could be needed by an external object file --- e.g., with arclite.

This patch enables three strategies:

- LTO_INTERNALIZE_FULL: the default (and the old behaviour).
- LTO_INTERNALIZE_NONE: skip -internalize.
- LTO_INTERNALIZE_HIDDEN: only -internalize symbols with hidden
  visibility.

LTO_INTERNALIZE_FULL should be used when linking an executable.

Outputting an object file (e.g., via ld -r) is more complicated, and
depends on whether hidden symbols should be internalized.  E.g., for
ld -r, LTO_INTERNALIZE_NONE can be used when -keep_private_externs, and
LTO_INTERNALIZE_HIDDEN can be used otherwise.  However,
LTO_INTERNALIZE_FULL is inappropriate, since the output object file will
eventually need to link with others.

lto_codegen_set_internalize_strategy() sets the strategy for subsequent
calls to lto_codegen_write_merged_modules() and lto_codegen_compile*().

<rdar://problem/14334895>

llvm-svn: 199191

There are two ways one could implement hiding of linkonce_odr symbols in LTO:
* LLVM tells the linker which symbols can be hidden if not used from native
  files.
* The linker tells LLVM which symbols are not used from other object files,
  but will be put in the dso symbol table if present.

GOLD's API is the second option. It was implemented almost 1:1 in llvm by
passing the list down to internalize.

LLVM already had partial support for the first option. It is also very similar
to how ld64 handles hiding these symbols when *not* doing LTO.

This patch then
* removes the APIs for the DSO list.
* marks LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN all linkonce_odr unnamed_addr
  global values and other linkonce_odr whose address is not used.
* makes the gold plugin responsible for handling the API mismatch.

llvm-svn: 193800

llvm-svn: 193404

This reverts commit r193255 and instead creates an lto_bool_t typedef
that points to bool, _Bool, or unsigned char depending on what is
available.  Only recent versions of MSVC provide a stdbool.h header.

Reviewers: rafael.espindola

Differential Revision: http://llvm-reviews.chandlerc.com/D2019

llvm-svn: 193377

llvm-svn: 193255

Generalize the API so we can distinguish symbols that are needed just for a DSO
symbol table from those that are used from some native .o.

The symbols that are only wanted for the dso symbol table can be dropped if
llvm can prove every other dso has a copy (linkonce_odr) and the address is not
important (unnamed_addr).

llvm-svn: 191922

llvm-svn: 191359

This should fix the MSVC build.

llvm-svn: 191357

----
  Add new API lto_codegen_compile_parallel().

  This API is proposed by Nick Kledzik. The semantic is:

  --------------------------------------------------------------------------
   Generate code for merged module into an array of native object files. On 
   success returns a pointer to an array of NativeObjectFile.  The count 
   parameter returns the number of elements in the array.  Each element is 
   a pointer/length for a generated mach-o/ELF buffer.  The buffer is owned
   by the lto_code_gen_t and will be freed when lto_codegen_dispose() is called, 
   or lto_codegen_compile() is called again. On failure, returns NULL 
   (check lto_get_error_message() for details).

   extern const struct  NativeObjectFile*
   lto_codegen_compile_parallel(lto_code_gen_t cg, size_t *count);
  ---------------------------------------------------------------------------

  This API is currently only called on OSX platform. Linux or other Unixes
using GNU gold are not supposed to call this function, because on these systems, 
object files are fed back to linker via disk file instead of memory buffer.

  In this commit, lto_codegen_compile_parallel() simply calls
lto_codegen_compile() to return a single object file. In the near future,
this function is the entry point for compilation with partition. Linker can
blindly call this function even if partition is turned off; in this case,
compiler will return only one object file.

llvm-svn: 189386

  This API is proposed by Nick Kledzik. The semantic is:

  --------------------------------------------------------------------------
   Generate code for merged module into an array of native object files. On 
   success returns a pointer to an array of NativeObjectFile.  The count 
   parameter returns the number of elements in the array.  Each element is 
   a pointer/length for a generated mach-o/ELF buffer.  The buffer is owned
   by the lto_code_gen_t and will be freed when lto_codegen_dispose() is called, 
   or lto_codegen_compile() is called again. On failure, returns NULL 
   (check lto_get_error_message() for details).

   extern const struct  NativeObjectFile*
   lto_codegen_compile_parallel(lto_code_gen_t cg, size_t *count);
  ---------------------------------------------------------------------------

  This API is currently only called on OSX platform. Linux or other Unixes
using GNU gold are not supposed to call this function, because on these systems, 
object files are fed back to linker via disk file instead of memory buffer.

  In this commit, lto_codegen_compile_parallel() simply calls
lto_codegen_compile() to return a single object file. In the near future,
this function is the entry point for compilation with partition. Linker can
blindly call this function even if partition is turned off; in this case,
compiler will return only one object file.

llvm-svn: 189297

In order to appease people (in Apple) who accuse me for committing "huge change" (?) without proper review. 

Thank Eric for fixing a compile-warning. 

llvm-svn: 188204

  1. Add some helper classes for partitions. They are designed in a
     way such that the top-level LTO driver will not see much difference 
     with or without partitioning.

  2. Introduce work-dir. Now all intermediate files generated during 
     LTO phases will be saved under work-dir. User can specify the workdir
     via -lto-workdir=/path/to/dir. By default the work-dir will be 
     erased before linker exit. To keep the workdir, do -lto-keep, or -lto-keep=1.

    TODO: Erase the workdir, if the linker exit prematurely.  
      We are currently not able to remove directory on signal. The support 
      routines simply ignore directory.

  3. Add one new API lto_codegen_get_files_need_remove().
     Linker and LTO plugin will communicate via this API about which files
    (including directories) need to removed before linker exit.

llvm-svn: 188188

llvm-svn: 172025

The linker will call `lto_codegen_add_must_preserve_symbol' on all globals that
should be kept around. The linker will pretend that a dylib is being created.
<rdar://problem/12528059>

llvm-svn: 169770

This function sets the `_exportDynamic' ivar. When that's set, we export all
symbols (e.g. we don't run the internalize pass). This is equivalent to the
`--export-dynamic' linker flag in GNU land:

--export-dynamic
  When creating a dynamically linked executable, add all symbols to the dynamic
  symbol table. The dynamic symbol table is the set of symbols which are visible
  from dynamic objects at run time. If you do not use this option, the dynamic
  symbol table will normally contain only those symbols which are referenced by
  some dynamic object mentioned in the link. If you use dlopen to load a dynamic
  object which needs to refer back to the symbols defined by the program, rather
  than some other dynamic object, then you will probably need to use this option
  when linking the program itself.

The Darwin linker will support this via the `-export_dynamic' flag. We should
modify clang to support this via the `-rdynamic' flag.

llvm-svn: 169656

Necessary to give disassembler users (like darwin's otool) a possibility to
dlopen libLTO and still initialize the required LLVM bits. This used to go
through libMCDisassembler but that's a gross layering violation, the MC layer
can't pull in functions from the targets. Adding a function to libLTO is a bit
of a hack but not worse than exposing other disassembler bits from libLTO.

Fixes PR14362.

llvm-svn: 168545

so we don't want it to show up in the stable 3.1 interface.

While at it, add a comment about why LTOCodeGenerator manually creates the
internalize pass.

llvm-svn: 154807

llvm-svn: 154312

llvm-svn: 154306

llvm-svn: 153802

This gives a lot of love to the docs for the C API. Like Clang's
documentation, the C API is now organized into a Doxygen "module"
(LLVMC). Each C header file is a child of the main module. Some modules
(like Core) have a hierarchy of there own. The produced documentation is
thus better organized (before everything was in one monolithic list).

This patch also includes a lot of new documentation for APIs in Core.h.
It doesn't document them all, but is better than none. Function docs are
missing @param and @return annotation, but the documentation body now
commonly provides help details (like the expected llvm::Value sub-type
to expect).

llvm-svn: 153157

Luis Felipe Strano Moraes!

llvm-svn: 129558

memory and writing it back to disk.

llvm-svn: 128108

of an file.

llvm-svn: 127781

MemoryBuffer::getOpenFile to not close the file descriptor.

llvm-svn: 125128

This means avoid using uint32_t. This patch reverts r112200 and fixes original  problem by fixing argument type in lto.cpp.

llvm-svn: 123038

llvm-svn: 120304

"linker_private_weak_auto_def" linkage type for LTO.

llvm-svn: 114868

llvm-svn: 112200

llvm-svn: 112069

llvm-svn: 110759

Nick, please review.

llvm-svn: 110705

gold plugin.

llvm-svn: 110604

llvm-svn: 108126

several unwanted dependencies.

llvm-svn: 75717

llvm-svn: 74678

llvm-svn: 74663

llvm-svn: 74640

Add lto_codegen_set_assembler_path() API which allows the linker to specify the
path to the assembler tool to run.  When assembler is used (instead of compiler)
different command line options are used.
Add LTO_API_VERSION #define so clients (linkers) can conditionalize use of new APIs.

llvm-svn: 72823

llvm-svn: 70491