I don't understand why the previous code is pretty flaky and
the new code is at least less flaky, but the original test
occasionally failed on the second run of lib.exe.
My guess was that lib.exe was failing because the output of
the echo command executed immediately before lib.exe was not
flushed to a file, but as far as I can say, the file
descriptor is properly closed in TestRunner.py, so this's
probably not correct. Other theory is that, on Windows, file
output is not guaranteed to be visible to other processes even
if a process flushes file descriptors, but I'd think that's
unlikely. So honestly I don't know the cause yet.
llvm-svn: 246621
This patch fixes a subtle incompatibility with MSVC linker.
MSVC linker preserves the original spelling of a DLL in the
import descriptor table. LLD previously converted all
characters to lowercase. Usually this difference is benign,
but if a program explicitly checks for DLL file names, the
program could fail.
llvm-svn: 246620
The ELF spec says:
... if any reference to or definition of a name is a symbol with a
non-default visibility attribute, the visibility attribute must be
propagated to the resolving symbol in the linked object. If different
visibility attributes are specified for distinct references to or
definitions of a symbol, the most constraining visibility attribute
must be propagated to the resolving symbol in the linked object. The
attributes, ordered from least to most constraining, are:
STV_PROTECTED, STV_HIDDEN and STV_INTERNAL.
llvm-svn: 246603
In r246424, I made a change that disables non-DLL to export
symbols. It turned out that the change was not correct. Both
DLLs and executables are able to export symbols (although the
latter is relatively rare). This change restores the feature.
llvm-svn: 246537
I have totally no idea why, but MSVC linker is sensitive about
file names of archive members. If we do not make import library
file names to the same as the DLL name, MSVC link *crashes*
when it is processing the library file. This patch is to set
the same name.
llvm-svn: 246535
The rules for dllexported symbols are overly complicated due to
x86 name decoration, fuzzy symbol resolution, and the fact that
one symbol can be resolved by so many different names. The rules
are probably intended to be "intuitive", so that users don't have
to understand the name mangling schemes, but it seems that it can
lead to unintended symbol exports.
To make it clear what I'm trying to do with this patch, let me
write how the export rules are subtle and complicated.
- x86 name decoration: If machine type is i386 and export name
is given by a command line option, like /export:foo, the
real symbol name the linker has to search for is _foo because
all symbols are decorated with "_" prefixes. This doesn't happen
on non-x86 machines. This automatic name decoration happens only
when the name is not C++ mangled.
However, the symbol name exported from DLLs are ones without "_"
on all platforms.
Moreover, if the option is given via .drectve section, no
symbol decoration is done (the reason being that the .drectve
section is created by a compiler and the compiler should always
know the exact name of the symbol, I guess).
- Fuzzy symbol resolution: In addition to x86 name decoration,
the linker has to look for cdecl or C++ mangled symbols
for a given /export. For example, it searches for not only
_foo but also _foo@<number> or ??foo@... for /export:foo.
Previous implementation didn't get it right. I'm trying to make
it as compatible with MSVC linker as possible with this patch
however the rules are. The new code looks a bit messy to me, but
I don't think it can be simpler due to the ad-hoc-ness of the rules.
llvm-svn: 246424
Now that we print a symbol table and all symbol kinds are at least declared,
we can test all combinations that don't produce an error.
This also includes a few fixes to keep the test passing:
* Keep the strong symbol in a weak X strong pair
* Handle common symbols.
The common X common case will be finished in a followup patch.
llvm-svn: 246401
This is exposed via a new flag /opt:lldltojobs=N, where N is the number of
code generation threads.
Differential Revision: http://reviews.llvm.org/D12309
llvm-svn: 246342
This is a basic implementation that allows lld to emit binaries
consumable by the HSA runtime.
Differential Revision: http://reviews.llvm.org/D11267
llvm-svn: 246155
ICF is a feature to merge sections not by name (which is the regular
COMDAT merging) but by contents. If two or more sections have the
identical contents and relocations, ICF merges them to save space.
Accessors or templated functions tend to have the same contents, and
ICF can hold them.
If we consider sections as vertices and relocations as edges, the
problem is to find as many isomorphic graphs as possile from input
graphs. MSVC linker is smart enough to identify isomorphic graphs
even if they contain circles (GNU gold cannot handle circles
according to http://research.google.com/pubs/pub36912.html, so this
is impressive).
Circular references are not uncommon in COFF object files.
One example is .pdata. .pdata sections contain exception handler info
for functions, so they naturally have relocations for the functions.
The functions in turn have references to the .pdata sections so that
the functions and their .pdata are linked together. As a result, they
form circles.
This is a test case for circular graphs. LLD is not able to handle
this test case yet. I'll add code soon.
llvm-svn: 245827
The old test files were just compiler outputs, so it was hard to
debug if something goes wrong. The new test file is carefully
hand-crafted to trigger ICF to avoid that.
llvm-svn: 245826
Previously, weak external symbols could reference only symbols that
appeared before them. Although that covers almost all use cases
of weak externals, there are object files out there which contains
weak externals that have forward references.
This patch supports such weak externals.
llvm-svn: 245258
There are some DLLs whose initializers depends on other DLLs'
initializers. The initialization order matters for them.
MSVC linker uses the order of the libraries from the command line.
LLD used ASCII-betical order. So they were incompatible.
This patch makes LLD compatible with MSVC.
llvm-svn: 245201
Michael J. Spencer