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7e667c56cf
llvm/tools/gold
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Rafael Espindola 7e667c56cf Use LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN instead of the "dso list". 
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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193800 91177308-0d34-0410-b5e6-96231b3b80d8
2013-10-31 20:51:58 +00:00
..
CMakeLists.txt Use absolute path to exportsfile in gold plugin CMake build. 2011-11-05 04:17:20 +00:00
gold-plugin.cpp Use LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN instead of the "dso list". 2013-10-31 20:51:58 +00:00
gold.exports Create an exports file, so that the plugin only exports the onload symbol. 2010-04-16 00:43:25 +00:00
Makefile Pass -lLTO after gold-plugin.o so that it gets used in systems that default to 2012-08-27 03:03:07 +00:00
README.txt s/libLLVMgold/LLVMgold/g 2010-08-08 21:14:26 +00:00

README.txt 

This directory contains a plugin that is designed to work with binutils
gold linker. At present time, this is not the default linker in
binutils, and the default build of gold does not support plugins.

Obtaining binutils:

  cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src login
  {enter "anoncvs" as the password}
  cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src co binutils

This will create a src/ directory. Make a build/ directory and from
there configure binutils with "../src/configure --enable-gold --enable-plugins".
Then build binutils with "make all-gold".

To build the LLVMgold plugin, configure LLVM with the option
--with-binutils-include=/path/to/binutils/src/include/ --enable-pic. To use the
plugin, run "ld-new --plugin /path/to/LLVMgold.so".
Without PIC libLTO and LLVMgold are not being built (because they would fail
link on x86-64 with a relocation error: PIC and non-PIC can't be combined).
As an alternative to passing --enable-pic, you can use 'make ENABLE_PIC=1' in
your entire LLVM build.