[lld] r308700 - Add contents to lld 5.0's release notes.
Rui Ueyama via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 20 17:28:02 PDT 2017
Author: ruiu
Date: Thu Jul 20 17:28:02 2017
New Revision: 308700
URL: http://llvm.org/viewvc/llvm-project?rev=308700&view=rev
Log:
Add contents to lld 5.0's release notes.
Modified:
lld/branches/release_50/docs/ReleaseNotes.rst
Modified: lld/branches/release_50/docs/ReleaseNotes.rst
URL: http://llvm.org/viewvc/llvm-project/lld/branches/release_50/docs/ReleaseNotes.rst?rev=308700&r1=308699&r2=308700&view=diff
==============================================================================
--- lld/branches/release_50/docs/ReleaseNotes.rst (original)
+++ lld/branches/release_50/docs/ReleaseNotes.rst Thu Jul 20 17:28:02 2017
@@ -1,5 +1,5 @@
=======================
-LLD 5.0.0 Release Notes
+lld 5.0.0 Release Notes
=======================
.. contents::
@@ -13,9 +13,9 @@ LLD 5.0.0 Release Notes
Introduction
============
-This document contains the release notes for the LLD linker, release 5.0.0.
-Here we describe the status of LLD, including major improvements
-from the previous release. All LLD releases may be downloaded
+This document contains the release notes for the lld linker, release 5.0.0.
+Here we describe the status of lld, including major improvements
+from the previous release. All lld releases may be downloaded
from the `LLVM releases web site <http://llvm.org/releases/>`_.
Non-comprehensive list of changes in this release
@@ -24,7 +24,78 @@ Non-comprehensive list of changes in thi
ELF Improvements
----------------
-* Item 1.
+* First and foremost, a lot of compatibility issues and bugs has been fixed.
+ Linker script support has significantly improved. As a result, we believe you
+ are very likely to be able to link your programs with lld without experiencing
+ any problem now.
+
+* Error message format has changed in order to improve readability.
+ Traditionally, linker's error messages are concise and arguably too tarse.
+ This is an example of lld 4.0's error message (they are actually in one line)::
+
+ /ssd/clang/bin/ld.lld: error: /ssd/llvm-project/lld/ELF/Writer.cpp:207:
+ undefined symbol 'lld::elf::EhFrameSection::addSection()'
+
+ It is not easy to read because too many information is packed into single line
+ and the embedded text, particularly a symbol name, is sometimes too long.
+ In lld 5.0, we use more vertical space to print out error messages in a more
+ structured manner like this::
+
+ bin/ld.lld: error: undefined symbol: lld::elf::EhFrameSection::addSection()
+ >>> Referenced by Writer.cpp:207 (/ssd/llvm-project/lld/ELF/Writer.cpp:207)
+ >>> Writer.cpp.o in archive lib/liblldELF.a
+
+ As a bonus, the new error message contains source code location of the error
+ if it is available from debug info.
+
+* ``./configure`` scripts generated by GNU autoconf determines wheter a linker
+ supports modern GNU-compatible features or not by searching for "GNU" in the
+ ``--help`` message. To be compatible with the scripts, we decided to add a
+ string "(compatible with GNU linkers)" to our ``--help`` message. This is a
+ hack, but just like the web browser's User-Agent string, we had no choice
+ other than doing this to declare that we accept GNU-compatible options.
+
+* The ``-Map`` option is added. The option is to make the linker to print out how
+ input files are mapped to the output file. Here is an example::
+
+ Address Size Align Out In Symbol
+ 00000000016d84d8 00000000008f8f50 8 .eh_frame
+ 00000000016d84d8 00000000008f8f50 8 <internal>:(.eh_frame)
+ 0000000001fd2000 00000000034b3bd0 16 .text
+ 0000000001fd2000 000000000000002a 1 /usr/lib/x86_64-linux-gnu/crt1.o:(.text)
+ 0000000001fd2000 0000000000000000 0 _start
+ 0000000001fd202a 0000000000000000 1 /usr/lib/x86_64-linux-gnu/crti.o:(.text)
+ 0000000001fd2030 00000000000000bd 16 /usr/lib/gcc/x86_64-linux-gnu/4.8/crtbegin.o:(.text)
+ 0000000001fd2030 0000000000000000 0 deregister_tm_clones
+ 0000000001fd2060 0000000000000000 0 register_tm_clones
+
+ This format is not the same as GNU linkers as our linker internal data
+ structure is different from them but contains the same amount of information
+ and should be more readable than their outputs.
+
+ As with other lld features, the ``-Map`` option is desigend with speed in mind.
+ The option would generate a hundred megabyte of text file if you link a large
+ program with it. lld can usually do that in a few seconds, and it is generally
+ a few times faster than the GNU gold's ``-Map`` option.
+
+* Some nonstandard relocations, such as R_X86_64_8 or R_X86_64_16, are supported.
+ They are not used for 32/64-bit applications, but some 16-bit bootloaders need
+ them.
+
+* Paddings in executable text sections are now filled with trap instructions
+ (such as INT3) instead of being left as null bytes. This change improves
+ disassembler outputs because it now prints out trap instructions instead of
+ trying to decode 0x00 as an instruction. It also makes debugging of some type
+ of program easier because when the control reaches a padding, the program
+ immediately raises an error.
+
+* The following options are added: ``-M``, ``-Map``,
+ ``-compress-debug-sections``, ``-emit-relocs``,
+ ``-error-unresolved-symbols``, ``-exclude-libs``, ``-filter``,
+ ``-no-dynamic-linker``, ``-no-export-dynamic``, ``-no-fatal-warnings``,
+ ``-print-map``, ``-warn-unresolved-symbols``, ``-z nocopyreloc``,
+ ``-z notext``, ``-z rodynamic``
+
COFF Improvements
-----------------
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