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Author SHA1 Message Date
Sylvestre Ledru b307a0b949 Improve the documentation. Patch from genewitch. Found on https://github.com/llvm-mirror/lld/pull/5 
llvm-svn: 296739
 2017-03-02 10:40:24 +00:00
Rui Ueyama 33d9d5d5b4 Remove an obsolete/duplicate part of a document. 
llvm-svn: 296304
 2017-02-27 00:11:25 +00:00
Sean Silva 69d65ac44b [docs] Fix typo in section heading. 
llvm-svn: 292750
 2017-01-22 03:28:56 +00:00
Rui Ueyama 13146fce60 Update document. 
llvm-svn: 284698
 2016-10-20 05:35:25 +00:00
Rui Ueyama 729822fe39 Update the readme text. 
llvm-svn: 275305
 2016-07-13 19:14:25 +00:00
Rui Ueyama 9337869393 Update numbers. 
llvm-svn: 272596
 2016-06-13 22:48:36 +00:00
Peter Collingbourne 4f9527065c ELF: New symbol table design. 
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
 2016-05-01 04:55:03 +00:00
Rui Ueyama 7a32d9a653 We do not use libLTO, so fix the error. 
llvm-svn: 264093
 2016-03-22 20:58:15 +00:00
Rui Ueyama 27a3f01deb ELF: Update the document. 
llvm-svn: 263473
 2016-03-14 19:53:52 +00:00
Rui Ueyama 88daab9174 ELF: Add a few numbers to the document. 
llvm-svn: 263466
 2016-03-14 18:43:01 +00:00
Rui Ueyama 02aa766897 Update the documents of the new LLD. 
This patch merges the documents for ELF and COFF into one
and puts it into docs directory.

llvm-svn: 263336
 2016-03-12 06:06:40 +00:00