This format is simply a regular object file with the bitcode stored in a
section named ".llvmbc", plus any number of other (non-allocated) sections.
One immediate use case for this is to accommodate compilation processes
which expect the object file to contain metadata in non-allocated sections,
such as the ".go_export" section used by some Go compilers [1], although I
imagine that in the future we could consider compiling parts of the module
(such as large non-inlinable functions) directly into the object file to
improve LTO efficiency.
[1] http://golang.org/doc/install/gccgo#Imports
Differential Revision: http://reviews.llvm.org/D4371
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to match llvm-size and other UNIX systems for their nm(1).
Tweak test cases that used llvm-nm with standard input to add a "-" to
indicate that and add a test case to check the default of a.out for llvm-nm.
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Visibilities of `hidden` and `protected` are meaningless for symbols
with local linkage.
- Change the assembler to reject non-default visibility on symbols
with local linkage.
- Change the bitcode reader to auto-upgrade `hidden` and `protected`
to `default` when the linkage is local.
- Update LangRef.
<rdar://problem/16141113>
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This adds support for an -mattr option to the gold plugin and to llvm-lto. This
allows the caller to specify details of the subtarget architecture, like +aes,
or +ssse3 on x86. Note that this requires a change to the include/llvm-c/lto.h
interface: it adds a function lto_codegen_set_attr and it increments the
version of the interface.
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part of an asm .symver directive as being used. This prevents referenced
functions from being internalized and deleted.
Without the patch to LTOModule.cpp, the test case will produce the error:
LLVM ERROR: A @@ version cannot be undefined.
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During LTO, user-supplied definitions of C library functions often
exist. -instcombine uses Module::getOrInsertFunction() to get a handle
on library functions (e.g., @puts, when optimizing @printf).
Previously, Module::getOrInsertFunction() would rename any matching
functions with local linkage, and create a new declaration. In LTO,
this is the opposite of desired behaviour, as it skips by the
user-supplied version of the library function and creates a new
undefined reference which the linker often cannot resolve.
After some discussing with Rafael on the list, it looks like it's
undesired behaviour. If a consumer actually *needs* this behaviour, we
should add new API with a more explicit name.
I added two testcases: one specifically for the -instcombine behaviour
and one for the LTO flow.
<rdar://problem/16165191>
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r201608 made llvm corretly handle private globals with MachO. r201622 fixed
a bug in it and r201624 and r201625 were changes for using private linkage,
assuming that llvm would do the right thing.
They all got reverted because r201608 introduced a crash in LTO. This patch
includes a fix for that. The issue was that TargetLoweringObjectFile now has
to be initialized before we can mangle names of private globals. This is
trivially true during the normal codegen pipeline (the asm printer does it),
but LTO has to do it manually.
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Add user-supplied C runtime and compiler-rt library functions to
llvm.compiler.used to protect them from premature optimization by
passes like -globalopt and -ipsccp. Calls to (seemingly unused)
runtime library functions can be added by -instcombine and instruction
lowering.
Patch by Duncan Exon Smith, thanks!
Fixes <rdar://problem/14740087>
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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.
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When a linkonce_odr value that is on the dso list is not unnamed_addr
we can still look to see if anything is actually using its address. If
not, it is safe to hide it.
This patch implements that by moving GlobalStatus to Transforms/Utils
and using it in Internalize.
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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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Enable building the LTO library (.lib and.dll) and llvm-lto.exe on Windows with
MSVC and Mingw as well as re-enabling the associated test.
Patch by Greg Bedwell!
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Enable building the LTO library (.lib and.dll) and llvm-lto.exe on Windows with
MSVC and Mingw as well as re-enabling the associated test.
Patch by Greg Bedwell!
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