llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-20 10:30:03 +00:00

History

Rafael Espindola 3fd7e37b34 Rewrite the gold plugin to fix pr19901. There is a fundamental difference between how the gold API and lib/LTO view the LTO process. The gold API talks about a particular symbol in a particular file. The lib/LTO API talks about a symbol in the merged module. The merged module is then defined in terms of the IR semantics. In particular, a linkonce_odr GV is only copied if it is used, since it is valid to drop unused linkonce_odr GVs. In the testcase in pr19901 both properties collide. What happens is that gold asks us to keep a particular linkonce_odr symbol, but the IR linker doesn't copy it to the merged module and we never have a chance to ask lib/LTO to keep it. This patch fixes it by having a more direct implementation of the gold API. If it asks us to keep a symbol, we change the linkage so it is not linkonce. If it says we can drop a symbol, we do so. All of this before we even send the module to lib/Linker. Since now we don't have to produce LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN, during symbol resolution we can use a temporary LLVMContext and do lazy module loading. This allows us to keep the minimum possible amount of allocated memory around. This should also allow as much parallelism as we want, since there is no shared context. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216215 91177308-0d34-0410-b5e6-96231b3b80d8		2014-08-21 20:28:55 +00:00
..
CMakeLists.txt	Rewrite the gold plugin to fix pr19901.	2014-08-21 20:28:55 +00:00
gold-plugin.cpp	Rewrite the gold plugin to fix pr19901.	2014-08-21 20:28:55 +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	Rewrite the gold plugin to fix pr19901.	2014-08-21 20:28:55 +00:00
README.txt	Cut the gold plugin README down to size	2013-12-02 14:17:47 +00:00

README.txt

The LLVM Gold LTO Plugin
========================

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.

See docs/GoldPlugin.html for complete build and usage instructions.

NOTE: libLTO and LLVMgold aren't built without PIC because they would fail
to 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.