In COFF, an undefined symbol can have up to one alternative name. If a symbol
is resolved by its regular name, then it's linked normally. If a symbol is not
found in any input files, all references to the regular name are resolved using
the alternative name. If the alternative name is not found, it's a link error.
This mechanism is called "weak externals".

To support this mechanism, I added a new member function fallback() to undefined
atom. If an undefined atom has the second name, fallback() returns a new undefined
atom that should be used instead of the original one to resolve undefines. If it
does not have the second name, the function returns nullptr.

Differential Revision: http://llvm-reviews.chandlerc.com/D1550

llvm-svn: 190625

attribute in LinkerInput to isWholeArchive and use that for deciding
whether library archives should be expanded. Implement the -all_load
option of the Darwin linker using this flag and drop the support for it
in GNU mode.

llvm-svn: 190275

reference. Move readFile logic into FileNode::createLinkerInput.

llvm-svn: 190253

It looks like there is a possibility of seeing RO/RW note sections
and we would need to create an appropriate RO/RW segment associated
with them.

Adds a test too.

llvm-svn: 189907

Emit note sections if the input contains a note section.

Also emit a note segment.

llvm-svn: 189896

llvm-svn: 189775

This adds an API to the LinkingContext for flavors to add Internal files
containing atoms that need to appear in the YAML output as well, when -emit-yaml
switch is used.

Flavors can add more internal files for other options that are needed.

llvm-svn: 189718

llvm-svn: 189413

typeTLV content type is used by Darwin to represent thread local
storage. A new contentType has to be made to represent ELF
thread local storage data. These have been set to

- typeThreadZeroFill (represents TBSS storage)
- typeThreadData     (represents TDATA storage)

llvm-svn: 189137

llvm-svn: 188049

Also change some local variable names: "ti" -> "context" and
"_targetInfo" -> "_context".

Differential Revision: http://llvm-reviews.chandlerc.com/D1301

llvm-svn: 187823

llvm-svn: 186996

This patch adds a new pass, IdataPass, to transform shared atom references
to real references and to construct the .idata section data. With this patch
lld can produce a working Hello World program by linking it against
kernel32.dll and user32.dll.

Reviewers: Bigcheese

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1096

llvm-svn: 186071

llvm-svn: 184589

The yaml reader is not specific to any file format. This patch moves
it to TargetInfo and makes validate a non virtual interface so that it
can be constructed from a single location.

The same method will be used to create a reader for llvm bitcode
files.

llvm-svn: 183740

llvm-svn: 182789

llvm-svn: 181503

llvm-svn: 181492

llvm-svn: 181473

Patch by Rui Ueyama.

llvm-svn: 180209

to the list of undefined atoms. 

The processing of undefined atoms from dynamic libraries is controlled by
use-shlib-undefines command line option. 

This patch also adds additional command line arguments to allow/disallow
unresolved symbols from shared libraries and mimics GNU ld behavior.

llvm-svn: 179257

llvm-svn: 178940

llvm-svn: 178918

llvm-svn: 178914

llvm-svn: 178913

The major changes are:
1) LinkerOptions has been merged into TargetInfo
2) LinkerInvocation has been merged into Driver
3) Drivers no longer convert arguments into an intermediate (core) argument 
   list, but instead create a TargetInfo object and call setter methods on 
   it. This is only how in-process linking would work. That is, you can 
   programmatically set up a TargetInfo object which controls the linking.
4) Lots of tweaks to test suite to work with driver changes
5) Add the DarwinDriver
6) I heavily doxygen commented TargetInfo.h

Things to do after this patch is committed:
a) Consider renaming TargetInfo, given its new roll. 
b) Consider pulling the list of input files out of TargetInfo. This will 
   enable in-process clients to create one TargetInfo the re-use it with 
   different input file lists.
c) Work out a way for Drivers to format the warnings and error done in 
   core linking.

llvm-svn: 178776

ArrayRef<uint8_t>::equals(); lowers to a byte compare loop :(.

TODO: Figure out if we are getting hash collisions, or just have a lot of equal
content. Also test if crypto hashing the content instead of full compare is
better.

llvm-svn: 177588

llvm-svn: 177079

llvm-svn: 176309

llvm-svn: 175983

llvm-svn: 175901

llvm-svn: 174277

llvm-svn: 174107

llvm-svn: 173300

It owns and manages passes.

llvm-svn: 173287

No functionality change.

llvm-svn: 173192

llvm-svn: 173117

constants and string literals which the linker should coalesce.

llvm-svn: 172495

Since most content types (e.g. typeCode) have a 
preferred Permission, add a function to do that mapping.
Then hook up to YAML Reader and Writer such that
the 'permissions:' key does not need to be specified unless
overriding what the content type prefers.

llvm-svn: 171929

llvm-svn: 171916