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
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).
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This makes it possible to add timers to the code generator and still use them
with -plugin-opt=emit-llvm.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191866 91177308-0d34-0410-b5e6-96231b3b80d8
In order to appease people (in Apple) who accuse me for committing "huge change" (?) without proper review.
Thank Eric for fixing a compile-warning.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188204 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188188 91177308-0d34-0410-b5e6-96231b3b80d8
The main observation is that we never need both the filesize and the map size.
When mapping a slice of a file, it doesn't make sense to request a null
terminator and that would be the only case where the filesize would be used.
There are other cleanups that should be done in this area:
* A client should not have to pass the size (even an explicit -1) to say if
it wants a null terminator or not, so we should probably swap the argument
order.
* The default should be to not require a null terminator. Very few clients
require this, but many end up asking for it just because it is the default.
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The gold plugin was passing the desired map size as the file size. This was
working for two reasons:
* Recent version of gold provide the get_view callback, so this code was not
used.
* In older versions, getOpenFile was called, but the file size is never used
if we don't require null terminated buffers and map size defaults to the
file size.
Thanks to Eli Bendersky for noticing this.
I will try to make this api a bit less error prone.
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The error message was:
/home/espindola/llvm/llvm/tools/gold/gold-plugin.cpp: In function ‘ld_plugin_status cleanup_hook()’:
/home/espindola/llvm/llvm/tools/gold/gold-plugin.cpp:461:30: error: cannot pass objects of non-trivially-copyable type ‘std::string {aka class std::basic_string<char>}’ through ‘...’
I will check if this was a clang or gcc issue.
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Again, tools are trickier to pick the main module header for than
library source files. I've started to follow the pattern of using
LLVMContext.h when it is included as a stub for program source files.
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to hack around this in the gold plugin by deleting a module if no symbol was
needed. Unfortunately, the hack is wrong in the case of o module having no
visible symbols but still having side effects via static constructors.
The bug will have to be fixed in libLTO itself.
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gold to work. Since the enum value LDPO_PIE has just been added to plugin-api.h,
use a numeric constant for now so that we don't require an unreleased
version of gold to build.
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gold plugin is built with Large File Support (sizeof(off_t) == 64 on i686)
and the rest of LLVM is built w/o Large File Support
(sizeof(off_t) == 32 on i686) which corrupts the stack.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139873 91177308-0d34-0410-b5e6-96231b3b80d8
having a library both as bitcode and native code. We want to use the
bitcode first, but if codegen produces new undefined references we have to use
the native code to satisfy those references.
Gold has no notion of bitcode and native search directories, so instead it has
an API where the plugin can instruct it to look for the libraries it is passing
to it. This patch uses that API.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106674 91177308-0d34-0410-b5e6-96231b3b80d8
ask the linker to take another look into some library or object. The case when
one might want to do this is when codegen introduces a new undefined reference.
The canonical example is libgcc.
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