[lld] r308700 - Add contents to lld 5.0's release notes.

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
 -----------------


