This patch implements a new design for the symbol table that stores
SymbolBodies within a memory region of the Symbol object. Symbols are mutated
by constructing SymbolBodies in place over existing SymbolBodies, rather
than by mutating pointers. As mentioned in the initial proposal [1], this
memory layout helps reduce the cache miss rate by improving memory locality.
Performance numbers:
old(s) new(s)
Without debug info:
chrome 7.178 6.432 (-11.5%)
LLVMgold.so 0.505 0.502 (-0.5%)
clang 0.954 0.827 (-15.4%)
llvm-as 0.052 0.045 (-15.5%)
With debug info:
scylla 5.695 5.613 (-1.5%)
clang 14.396 14.143 (-1.8%)
Performance counter results show that the fewer required indirections is
indeed the cause of the improved performance. For example, when linking
chrome, stalled cycles decreases from 14,556,444,002 to 12,959,238,310, and
instructions per cycle increases from 0.78 to 0.83. We are also executing
many fewer instructions (15,516,401,933 down to 15,002,434,310), probably
because we spend less time allocating SymbolBodies.
The new mechanism by which symbols are added to the symbol table is by calling
add* functions on the SymbolTable.
In this patch, I handle local symbols by storing them inside "unparented"
SymbolBodies. This is suboptimal, but if we do want to try to avoid allocating
these SymbolBodies, we can probably do that separately.
I also removed a few members from the SymbolBody class that were only being
used to pass information from the input file to the symbol table.
This patch implements the new design for the ELF linker only. I intend to
prepare a similar patch for the COFF linker.
[1] http://lists.llvm.org/pipermail/llvm-dev/2016-April/098832.html
Differential Revision: http://reviews.llvm.org/D19752
llvm-svn: 268178
The Native file format was designed to be the fastest on-memory or
on-disk file format for object files. The problem is that no one
is working on that. No LLVM tools can produce object files in
the Native, thus the feature of supporting the format is useless
in the linker.
This patch removes the Native file support. We can add it back
if we really want it in future.
llvm-svn: 234641
Before this patch there was a cyclic dependency between lldCore and
lldReaderWriter. Only lldConfig could be built as a shared library.
* Moved Reader and Writer base classes into lldCore.
* The following shared libraries can now be built:
lldCore
lldYAML
lldNative
lldPasses
lldReaderWriter
Differential Revision: http://reviews.llvm.org/D7105
From: Greg Fitzgerald <garious@gmail.com>
llvm-svn: 226732
The code is able to statically link the simplest case of:
int main() { return 0; }
* Only works with ARM code - no Thumb code, no interwork (-marm -mno-thumb-interwork)
* musl libc built with no interwork and no Thumb code
Differential Revision: http://reviews.llvm.org/D6716
From: Denis Protivensky <dprotivensky@accesssoftek.com>
llvm-svn: 226643
The original commit had an issue with Mac OS dylib files. It didn't
handle fat binary dylib files correctly. This patch includes a fix.
A test for that case has already been committed in r225764.
llvm-svn: 226123
r225764 broke a basic functionality on Mac OS. This change reverts
r225764, r225766, r225767, r225769, r225814, r225816, r225829, and r225832.
llvm-svn: 225859
This patch adds the initial ELF/AArch64 support to lld. Only a basic "Hello
World" app has been successfully tested for both dynamic and static compiling.
Differential Revision: http://reviews.llvm.org/D4778
Patch by Daniel Stewart <stewartd@codeaurora.org>!
llvm-svn: 215544
``html_favicon`` seem to conflict with [what it in the sphinx
docs](http://sphinx-doc.org/config.html#confval-html_favicon).
So I've copied the comments from there to conf.py and changed its
value appropriately to remove the missing favicon.ico warning.
llvm-svn: 214971
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
Sean Silva