1======================
2LLVM 3.9 Release Notes
3======================
4
5.. contents::
6    :local:
7
8.. warning::
9   These are in-progress notes for the upcoming LLVM 3.9 release.  You may
10   prefer the `LLVM 3.8 Release Notes <http://llvm.org/releases/3.8.0/docs
11   /ReleaseNotes.html>`_.
12
13
14Introduction
15============
16
17This document contains the release notes for the LLVM Compiler Infrastructure,
18release 3.9.  Here we describe the status of LLVM, including major improvements
19from the previous release, improvements in various subprojects of LLVM, and
20some of the current users of the code.  All LLVM releases may be downloaded
21from the `LLVM releases web site <http://llvm.org/releases/>`_.
22
23For more information about LLVM, including information about the latest
24release, please check out the `main LLVM web site <http://llvm.org/>`_.  If you
25have questions or comments, the `LLVM Developer's Mailing List
26<http://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send
27them.
28
29Note that if you are reading this file from a Subversion checkout or the main
30LLVM web page, this document applies to the *next* release, not the current
31one.  To see the release notes for a specific release, please see the `releases
32page <http://llvm.org/releases/>`_.
33
34Non-comprehensive list of changes in this release
35=================================================
36* The LLVMContext gains a new runtime check (see
37  LLVMContext::discardValueNames()) that can be set to discard Value names
38  (other than GlobalValue). This is intended to be used in release builds by
39  clients that are interested in saving CPU/memory as much as possible.
40
41* There is no longer a "global context" available in LLVM, except for the C API.
42
43* .. note about autoconf build having been removed.
44
45* .. note about C API functions LLVMParseBitcode,
46   LLVMParseBitcodeInContext, LLVMGetBitcodeModuleInContext and
47   LLVMGetBitcodeModule having been removed. LLVMGetTargetMachineData has been
48   removed (use LLVMGetDataLayout instead).
49
50* The C API function LLVMLinkModules has been removed.
51
52* The C API function LLVMAddTargetData has been removed.
53
54* The C API function LLVMGetDataLayout is deprecated
55  in favor of LLVMGetDataLayoutStr.
56
57* The C API enum LLVMAttribute is deprecated in favor of
58  LLVMGetAttrKindID.
59
60* ``TargetFrameLowering::eliminateCallFramePseudoInstr`` now returns an
61  iterator to the next instruction instead of ``void``. Targets that previously
62  did ``MBB.erase(I); return;`` now probably want ``return MBB.erase(I);``.
63
64.. NOTE
65   For small 1-3 sentence descriptions, just add an entry at the end of
66   this list. If your description won't fit comfortably in one bullet
67   point (e.g. maybe you would like to give an example of the
68   functionality, or simply have a lot to talk about), see the `NOTE` below
69   for adding a new subsection.
70
71* ... next change ...
72
73.. NOTE
74   If you would like to document a larger change, then you can add a
75   subsection about it right here. You can copy the following boilerplate
76   and un-indent it (the indentation causes it to be inside this comment).
77
78   Special New Feature
79   -------------------
80
81   Makes programs 10x faster by doing Special New Thing.
82
83Changes to the LLVM IR
84----------------------
85
86* New intrinsics ``llvm.masked.load``, ``llvm.masked.store``,
87  ``llvm.masked.gather`` and ``llvm.masked.scatter`` were introduced to the
88  LLVM IR to allow selective memory access for vector data types.
89
90Changes to LLVM's IPO model
91---------------------------
92
93LLVM no longer does inter-procedural analysis and optimization (except
94inlining) on functions with comdat linkage.  Doing IPO over such
95functions is unsound because the implementation the linker chooses at
96link-time may be differently optimized than the one what was visible
97during optimization, and may have arbitrarily different observable
98behavior.  See `PR26774 <http://llvm.org/PR26774>`_ for more details.
99
100Changes to the ARM Backend
101--------------------------
102
103 During this release ...
104
105
106Changes to the MIPS Target
107--------------------------
108
109 During this release ...
110
111
112Changes to the PowerPC Target
113-----------------------------
114
115 Moved some optimizations from O3 to O2 (D18562)
116
117* Enable sibling call optimization on ppc64 ELFv1/ELFv2 abi
118
119Changes to the X86 Target
120-------------------------
121
122* LLVM now supports the Intel CPU codenamed Skylake Server with AVX-512
123  extensions using ``-march=skylake-avx512``. The switch enables the
124  ISA extensions AVX-512{F, CD, VL, BW, DQ}.
125
126* LLVM now supports the Intel CPU codenamed Knights Landing with AVX-512
127  extensions using ``-march=knl``. The switch enables the ISA extensions
128  AVX-512{F, CD, ER, PF}.
129
130Changes to the AMDGPU Target
131-----------------------------
132
133 * Mesa 11.0.x is no longer supported
134
135
136Changes to the OCaml bindings
137-----------------------------
138
139 During this release ...
140
141Support for attribute 'notail' has been added
142---------------------------------------------
143
144This marker prevents optimization passes from adding 'tail' or
145'musttail' markers to a call. It is used to prevent tail call
146optimization from being performed on the call.
147
148External Open Source Projects Using LLVM 3.9
149============================================
150
151An exciting aspect of LLVM is that it is used as an enabling technology for
152a lot of other language and tools projects. This section lists some of the
153projects that have already been updated to work with LLVM 3.9.
154
155* A project
156
157
158Additional Information
159======================
160
161A wide variety of additional information is available on the `LLVM web page
162<http://llvm.org/>`_, in particular in the `documentation
163<http://llvm.org/docs/>`_ section.  The web page also contains versions of the
164API documentation which is up-to-date with the Subversion version of the source
165code.  You can access versions of these documents specific to this release by
166going into the ``llvm/docs/`` directory in the LLVM tree.
167
168If you have any questions or comments about LLVM, please feel free to contact
169us via the `mailing lists <http://llvm.org/docs/#maillist>`_.
170
171