COFF supports a feature similar to ELF's section groups. This
patch implements it.
In ELF, section groups are identified by their names, and they are
treated somewhat differently from regular symbols. In COFF, the
feature is realized in a more straightforward way. A section can
have an annotation saying "if Nth section is linked, link this
section too."
I added a new reference type, kindAssociate. If a target atom is
coalesced away, the referring atom is removed by Resolver, so that
they are treated as a group.
Differential Revision: http://reviews.llvm.org/D4028
llvm-svn: 211106
isCoalescedAway(x) is faster than replacement(x) != x as the former
does not follow the replacement atom chain. Also it's easier to use.
llvm-svn: 210242
COFF supports a feature similar to ELF's section groups. This
patch implements it.
In ELF, section groups are identified by their names, and they are
treated somewhat differently from regular symbols. In COFF, the
feature is realized in a more straightforward way. A section can
have an annotation saying "if Nth section is linked, link this
section too."
Implementing such feature is easy. We can add a reference from a
target atom to an original atom, so that if the target is linked,
the original atom is also linked. If not linked, both will be
dead-stripped. So they are treated as a group.
I added a new reference type, kindAssociate. It does nothing except
preventing referenced atoms from being dead-stripped.
No change to the Resolver is needed.
Reviewers: Bigcheese, shankarke, atanasyan
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D3946
llvm-svn: 210240
This provides support for the autoconfing & make build style.
The format, style and implementation follows that used within the llvm and clang projects.
TODO: implement out-of-source documentation builds.
llvm-svn: 210177
FileToMutable is what this class does, but this class (or, to be precise,
an instance of this class) is a wrapper of the other SimpleFile. It's odd
that the class was named like a function.
llvm-svn: 210089
Previously section groups are doubly linked to their children.
That is, an atom representing a group has group-child references
to its group contents, and content atoms also have group-parent
references to the group atom. That relationship was invariant;
if X has a group-child edge to Y, Y must have a group-parent
edge to X.
However we were not using group-parent references at all. The
resolver only needs group-child edges.
This patch simplifies the section group by removing the unused
reverse edge. No functionality change intended.
Differential Revision: http://reviews.llvm.org/D3945
llvm-svn: 210066
Layout-before edges are no longer used for layout, but they are
still there for dead-stripping. If we would just remove them
from code, LLD would wrongly remove live atoms that were
referenced by layout-befores.
This patch fixes the issue. Before dead-stripping, it scans all
atoms to construct a reverse map for layout-after edges. Dead-
stripping pass uses the map to traverse the graph.
Differential Revision: http://reviews.llvm.org/D3986
llvm-svn: 210057
Reference::target() never returns a nullptr, so NULL check
is not needed and is more harmful than doing nothing.
No functionality change.
llvm-svn: 210008
This is a short-term fix to allow lld Readers to return error messages
with dynamic content.
The long term fix will be to enhance ErrorOr<> to work with errors other
than error_code. Or to change the interface to Readers to pass down a
diagnostics object through which all error messages are written.
llvm-svn: 209681
/alternatename is a command line option to define a weak alias. You
can use it as /alternatename:foo=bar to define "foo" as a weak alias
for "bar".
Because it's a command line option, the weak alias mapping is in the
LinkingContext object, and not in a object file being read.
Previously, we looked up the mapping each time we read a new symbol
from a file, to check if there is a weak alias defined for the symbol.
That's not wrong, but had made function signature's a bit complicated --
we had to pass the mapping object to many functions. Now their
parameter lists are much cleaner.
This also has another (unrealized) benefit. parseFile() now read a
file and then add alias symbols to the file. In the first pass a
LinkingContext object is not used at all. That should make it easy
to read files from archive files speculatively, as the first pass
is free from side effect.
llvm-svn: 209486
Alias symbols are SimpleDefinedAtoms and are platform neutral. They
don't have to belong ELF. This patch is to make it available to all
platforms. No functionality change intended.
Differential Revision: http://reviews.llvm.org/D3862
llvm-svn: 209475
In r205566, I made a change to Resolver so that Resolver revisit
only archive files in --start-group and --end-group pair. That's
not correct, as it also has to revisit DSO files.
This patch is to fix the issue.
Added a test to demonstrate the fix. I confirmed that it succeeded
before r205566, failed after r205566, and is ok with this patch.
Differential Revision: http://reviews.llvm.org/D3734
llvm-svn: 208797
Make it possible to add observers to an Input Graph, so that files
returned from an Input Graph can be examined before they are
passed to Resolver.
To implement some PE/COFF features we need to know all the symbols
that *can* be solved, including ones in archive files that are not
yet to be read.
Currently, Resolver only maintains a set of symbols that are
already read. It has no knowledge on symbols in skipped files in
an archive file.
There are many ways to implement that. I chose to apply the
observer pattern here because it seems most non-intrusive. We don't
want to mess up Resolver with architecture specific features.
Even in PE/COFF, the feature that needs this mechanism is minor.
So I chose not to modify Resolver, but add a hook to Input Graph.
Differential Revision: http://reviews.llvm.org/D3735
llvm-svn: 208753
Previously only the toplevel elements were expanded by expandElements().
Now we recursively call getReplacements() to expand input elements even
if they are in, say, in a group.
llvm-svn: 208144
isAlias always returns false and no one is using it. It was
originally added Atom to query if an atom is an alias for another
atom, assuming that alias atoms are different from normal atoms.
We now support atom aliasing, but the way that's implemented is
in a different way than what isAlias assumed. An alias atom is
just a regular defined atom with no content, and it has a layout-
before edge to alias-to atom so that they are layed out at the
same location in the result. So this is dead code, and it doesn't
make much sense to keep it.
llvm-svn: 207884
Export definitions in a module definition file is as follows:
exportedname[=internalname] [@ordinal [NONAME]] [PRIVATE] [DATA]
Previously we did not support =internalname, so users couldn't export
symbols from a DLL with a different name.
llvm-svn: 207827
In general the linker scripts's GROUP command works like a pair
of command line options --start-group/--end-group. But there is
a difference in the files look up algorithm.
The --start-group/--end-group commands use a trivial approach:
a) If the path has '-l' prefix, add 'lib' prefix and '.a'/'.so'
suffix and search the path through library search directories.
b) Otherwise, use the path 'as-is'.
The GROUP command implements more compicated approach:
a) If the path has '-l' prefix, add 'lib' prefix and '.a'/'.so'
suffix and search the path through library search directories.
b) If the path does not have '-l' prefix, and sysroot is configured,
and the path starts with the / character, and the script being
processed is located inside the sysroot, search the path under
the sysroot. Otherwise, try to open the path in the current
directory. If it is not found, search through library search
directories.
https://www.sourceware.org/binutils/docs-2.24/ld/File-Commands.html
The patch reviewed by Shankar Easwaran, Rui Ueyama.
llvm-svn: 207769
When creating a .lib file, we should strip the leading underscore,
but should not strip stdcall atsign suffix. Otherwise produced .lib
files cannot be linked.
llvm-svn: 207729
Previously the input file for the lib.exe command would be removed
as soon as the command exits, so we couldn't write a test to check
the file contents are correct.
This patch adds /lldmoduledeffile: option to retain a copy of the
temporary file at the given file path, so that you can see the file
if you want.
llvm-svn: 207727
I'm a bit surprised that I have not implemented this yet. This is
definitely needed to handle real-world module definition files.
This patch contains a unit test for r207294.
llvm-svn: 207297
LIBRARY directive in a module definition file specifies the output
DLL file name. It also takes an optional value for the base address.
llvm-svn: 206647
Currently LLD supports --defsym only in the form of
--defsym=<symbol>=<integer>, where the integer is interpreted as the
absolute address of the symbol. This patch extends it to allow other
symbol name to be given as an RHS value. If a RHS value is a symbol
name, the LHS symbol will be defined as an alias for the RHS symbol.
Internally, a LHS symbol is represented as a zero-size defined atom
who has an LayoutAfter reference to an undefined atom, whose name is
the RHS value. Everything else is already implemented -- Resolver
will resolve the undefined symbol, and the layout pass will layout
the two atoms at the same location. Looks like it's working fine.
Note that GNU LD supports --defsym=<symbol>=<symbol>+<addend>. That
feature is out of scope of this patch.
Differential Revision: http://reviews.llvm.org/D3332
llvm-svn: 206417
Seems getSomething() is more common naming scheme than just a noun
to get something, so renaming these members.
Differential Revision: http://llvm-reviews.chandlerc.com/D3285
llvm-svn: 205589
ELFLinkingContext has a method addUndefinedAtomsFromSharedLibrary().
The method is being used to skip a shared library within --start-group
and --end-group if it's not the first iteration of the group.
We have the same, incomplete mechanism to skip a shared library within
a group too. That's implemented in ELFFileNode. It's intended to not
return a shared library on the second or further iterations in the
first place. This mechanism is preferred over
addUndefinedAtomsFromSharedLibrary because the policy is implemented
in Input Graph -- that's what Input Graph is for.
This patch removes the dupluicate feature and fixes ELFFileNode.
Differential Revision: http://llvm-reviews.chandlerc.com/D3280
llvm-svn: 205566
"x.empty()" is more idiomatic than "x.size() == 0". This patch is to
add such method and use it in LLD.
Differential Revision: http://llvm-reviews.chandlerc.com/D3279
llvm-svn: 205558
Seems clang-modernize couldn't add "override" to nested classes, so
doing it by hand. Also removed unused virtual member function that
is not overriding anything, that seems to have been added by mistake.
llvm-svn: 205552
An ordinal is set to each child of Input Graph, but no one actually
uses it. The only piece of code that gets ordinaly values is
sortInputElements in InputGraph.cpp, but it does not actually do
anything -- we assign ordinals in increasing order just before
calling sort, so when sort is called it's already sorted. It's no-op.
We can simply remove it. No functionality change.
Differential Revision: http://llvm-reviews.chandlerc.com/D3270
llvm-svn: 205501
Resolver is sending too much information to Input Graph than Input
Graph actually needs. In order to collect the detailed information,
which wouldn't be consumed by anyone, we have a good amount of code
in Resolver, Input Graph and Input Elements. This patch is to
simplify it. No functionality change.
Specifically, this patch replaces ResolverState enum with a boolean
value. The enum defines many bits to notify the progress about
linking to Input Graph using bit masks, however, what Input Graph
actually does is to compare a given value with 0. The details of
the bit mask is simply being ignored, so the efforts to collect
such data is wasted.
This patch also changes the name of the notification interface from
setResolverState to notifyProgress, to make it sounds more like
message passing style. It's not a setter but something to notify of
an update, so the new name should be more appropriate than before.
Differential Revision: http://llvm-reviews.chandlerc.com/D3267
llvm-svn: 205463
LinkingContext and InputGraph are unnecessarily entangled. Most linker
input file data, e.g. the vector containing input files, the next index
of the input file, etc. are managed by InputGraph, but only the current
input file is for no obvious reason managed by LinkingContext.
This patch is to move code from LinkingContext to InputGraph to fix it.
It's now clear who's reponsible for managing input file state, which is
InputGraph, and LinkingContext is now free from that responsibility.
It improves the readability as we now have fewer dependencies between
classes. No functionality change.
Differential Revision: http://llvm-reviews.chandlerc.com/D3259
llvm-svn: 205394
insertElementAt()'s third parameter is not only unused but also ignored
if you pass Position::END. The actual meaning of the parameter was obscure.
Differential Revision: http://llvm-reviews.chandlerc.com/D3256
llvm-svn: 205376
Group class is designed for GNU LD's --start-group and --end-group. There's
no obvious need to have two classes for it -- one as an abstract base class
and the other as a concrete class.
llvm-svn: 205375
InputGraph has too many knobs and controls that are not being used. This
patch is to remove dead code, unused features and a class. There are two
things that worth noting, besides simple dead code removal:
1. ControlNode class is removed. We had it as the base class of Group
class, but it provides no functionality particularly meaningful. We now
have shallower class hierarchy that is easier to understand.
2. InputGraph provides a feature to replace a node with its internal data.
It is being used to "expand" some type of node, such as a Linker Script
node, with its actual files. We used to have two options when replacing
it -- ExpandOnly or ExpandAndReplace. ExpandOnly was to expand it but not
remove the node from the tree. There is no use of that option in the code,
so it was a dead feature.
Differential Revision: http://llvm-reviews.chandlerc.com/D3252
llvm-svn: 205363
PECOFFFileNode::parse can be called twice -- once by WinLink driver and
once more by Driver. We want to make sure that the second call won't mess
up the internal data.
llvm-svn: 205284
Some Clang build uses .imp not .lib file extension for an import library file,
so we need to treat such file as a library file.
Ideally we should not rely on file extensions to detect file type. Instead
we should use magic bytes at beginning of a file. The GNU-compatible driver
actually does that but it made writing unit tests hard, so I chose an ad-hoc
approach for now.
llvm-svn: 205283
.gnu.linkonce sections are similar to section groups.
They were supported before section groups existed and provided a way
to resolve COMDAT sections using a different design.
There are few implementations that use .gnu.linkonce sections
to store simple floating point constants which doesnot require complex section
group support but need a way to store only one copy of the floating point
constant in a binary.
.gnu.linkonce based symbol resolution achieves that.
Review : http://llvm-reviews.chandlerc.com/D3242
llvm-svn: 205280
This reverts commit 5d5ca72a7876c3dd3dd1db83dc6a0d74be9e2cd1.
Discuss on a better design to raise error when there is a similar group with Gnu
linkonce sections and COMDAT sections.
llvm-svn: 205224
.gnu.linkonce sections are similar to section groups. They were supported before
section groups existed and provided a way to resolve COMDAT sections using a
different design. There are few implementations that use .gnu.linkonce sections
to store simple floating point constants which doesnot require complex section
group support but need a way to store only one copy of the floating point
constant. .gnu.linkonce based symbol resolution achieves that.
llvm-svn: 205163
This patch is to support --defsym option for ELF file format/GNU-compatible
driver. Currently it takes a symbol name followed by '=' and a number. If such
option is given, the driver sets up an absolute symbol with the specified
address. You can specify multiple --defsym options to define multiple symbols.
GNU LD's --defsym provides many more features. For example, it allows users to
specify another symbol name instead of a number to define a symbol alias, or it
even allows a symbol plus an offset (e.g. --defsym=foo+3) to define symbol-
relative alias. This patch does not support that, but will be supported in
subsequent patches.
Differential Revision: http://llvm-reviews.chandlerc.com/D3208
llvm-svn: 205029
If --allow-multiple-definition option is given, LLD does not treat duplicate
symbol error as a fatal error. GNU LD supports this option.
Differential Revision: http://llvm-reviews.chandlerc.com/D3211
llvm-svn: 205015
Currently we use both layout-after and layout-before edges to specify atom
orders in the resulting executable. We have a complex piece of code in
LayoutPass.cpp to deal with both types of layout specifiers.
(In the following description, I denote "Atom A having a layout-after edge
to B" as "A -> B", and A's layout-before to B as "A => B".)
However, that complexity is not really needed for this reason: If there
are atoms such that A => B, B -> A is always satisifed, so using only layout-
after relationships will yield the same result as the current code.
Actually we have a piece of complex code that verifies that, for each A -> B,
B => [ X => Y => ... => Z => ] A is satsified, where X, Y, ... Z are all
zero-size atoms. We can get rid of the code from our codebase because layout-
before is basically redundant.
I think we can simplify the code for layout-after even more than this, but
I want to just remove this pass for now for simplicity.
Layout-before edges are still there for dead-stripping, so this change won't
break it. We will remove layout-before in a followup patch once we fix the
dead-stripping pass.
Differential Revision: http://llvm-reviews.chandlerc.com/D3164
llvm-svn: 204966
Tim Northover