9 These are in-progress notes for the upcoming LLVM 3.6 release. You may
10 prefer the `LLVM 3.5 Release Notes <http://llvm.org/releases/3.5.0/docs
11 /ReleaseNotes.html>`_.
17 This document contains the release notes for the LLVM Compiler Infrastructure,
18 release 3.6. Here we describe the status of LLVM, including major improvements
19 from the previous release, improvements in various subprojects of LLVM, and
20 some of the current users of the code. All LLVM releases may be downloaded
21 from the `LLVM releases web site <http://llvm.org/releases/>`_.
23 For more information about LLVM, including information about the latest
24 release, please check out the `main LLVM web site <http://llvm.org/>`_. If you
25 have questions or comments, the `LLVM Developer's Mailing List
26 <http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ is a good place to send
29 Note that if you are reading this file from a Subversion checkout or the main
30 LLVM web page, this document applies to the *next* release, not the current
31 one. To see the release notes for a specific release, please see the `releases
32 page <http://llvm.org/releases/>`_.
34 Non-comprehensive list of changes in this release
35 =================================================
38 For small 1-3 sentence descriptions, just add an entry at the end of
39 this list. If your description won't fit comfortably in one bullet
40 point (e.g. maybe you would like to give an example of the
41 functionality, or simply have a lot to talk about), see the `NOTE` below
42 for adding a new subsection.
44 * Support for AuroraUX has been removed.
46 * Added support for a `native object file-based bitcode wrapper format
47 <BitCodeFormat.html#native-object-file>`_.
52 If you would like to document a larger change, then you can add a
53 subsection about it right here. You can copy the following boilerplate
54 and un-indent it (the indentation causes it to be inside this comment).
59 Makes programs 10x faster by doing Special New Thing.
64 The semantics of the ``prefix`` attribute have been changed. Users
65 that want the previous ``prefix`` semantics should instead use
66 ``prologue``. To motivate this change, let's examine the primary
67 usecases that these attributes aim to serve,
69 1. Code sanitization metadata (e.g. Clang's undefined behavior
72 2. Function hot-patching: Enable the user to insert ``nop`` operations
73 at the beginning of the function which can later be safely replaced
74 with a call to some instrumentation facility.
76 3. Language runtime metadata: Allow a compiler to insert data for
77 use by the runtime during execution. GHC is one example of a
78 compiler that needs this functionality for its
79 tables-next-to-code functionality.
81 Previously ``prefix`` served cases (1) and (2) quite well by allowing the user
82 to introduce arbitrary data at the entrypoint but before the function
83 body. Case (3), however, was poorly handled by this approach as it
84 required that prefix data was valid executable code.
86 In this release the concept of prefix data has been redefined to be
87 data which occurs immediately before the function entrypoint (i.e. the
88 symbol address). Since prefix data now occurs before the function
89 entrypoint, there is no need for the data to be valid code.
91 The previous notion of prefix data now goes under the name "prologue
92 data" to emphasize its duality with the function epilogue.
94 The intention here is to handle cases (1) and (2) with prologue data and
95 case (3) with prefix data. See the language reference for further details
96 on the semantics of these attributes.
98 This refactoring arose out of discussions_ with Reid Kleckner in
99 response to a proposal to introduce the notion of symbol offsets to
100 enable handling of case (3).
102 .. _discussions: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073235.html
105 Changes to the ARM Backend
106 --------------------------
108 During this release ...
111 Changes to the MIPS Target
112 --------------------------
114 During this release the MIPS target has reached a few major milestones. The
115 compiler has gained support for MIPS-II and MIPS-III; become ABI-compatible
116 with GCC for big and little endian O32, N32, and N64; and is now able to
117 compile the Linux kernel for 32-bit targets. Additionally, LLD now supports
118 microMIPS for the O32 ABI on little endian targets.
123 A large number of bugs have been fixed for big-endian MIPS targets using the
124 N32 and N64 ABI's as well as a small number of bugs affecting other ABI's.
125 Please note that some of these bugs will still affect LLVM-IR generated by
126 LLVM 3.5 since correct code generation depends on appropriate usage of the
127 ``inreg``, ``signext``, and ``zeroext`` attributes on all function arguments
130 There are far too many corrections to provide a complete list but here are a
133 * Big-endian N32 and N64 now interlinks successfully with GCC compiled code.
134 Previously this didn't work for the majority of cases.
136 * The registers used to return a structure containing a single 128-bit floating
137 point member on the N32/N64 ABI's have been changed from those specified by
138 the ABI documentation to match those used by GCC. The documentation specifies
139 that ``$f0`` and ``$f2`` should be used but GCC has used ``$f0`` and ``$f1``
142 * Returning a zero-byte struct no longer causes arguments to be read from the
143 wrong registers when using the O32 ABI.
145 * The exception personality has been changed for 64-bit MIPS targets to
146 eliminate warnings about relocations in a read-only section.
148 * Incorrect usage of odd-numbered single-precision floating point registers
149 has been fixed when the fastcc calling convention is used with 64-bit FPU's
155 It is now possible to compile the Linux kernel. This currently requires a small
156 number of kernel patches. See the `LLVMLinux project
157 <http://llvm.linuxfoundation.org/index.php/Main_Page>`_ for details.
159 * Added -mabicalls and -mno-abicalls. The implementation may not be complete
160 but works sufficiently well for the Linux kernel.
162 * Fixed multiple compatibility issues between LLVM's inline assembly support
165 * Added support for a number of directives used by Linux to the Integrated
171 * Attempting to disassemble l[wd]c[23], s[wd]c[23], cache, and pref no longer
172 triggers an assertion.
174 * Added -muclibc and -mglibc to support toolchains that provide both uClibC and
177 * __SIZEOF_INT128__ is no longer defined for 64-bit targets since 128-bit
178 integers do not work at this time for this target.
180 * Using $t4-$t7 with the N32 and N64 ABI is deprecated when ``-fintegrated-as``
181 is in use and will be removed in LLVM 3.7. These names have never been
182 supported by the GNU Assembler for these ABI's.
184 Changes to the PowerPC Target
185 -----------------------------
187 There are numerous improvements to the PowerPC target in this release:
189 * LLVM now generates the Vector-Scalar eXtension (VSX) instructions from
190 version 2.06 of the Power ISA, for both big- and little-endian targets.
192 * LLVM now has a POWER8 instruction scheduling description.
194 * Address Sanitizer (ASAN) support is now fully functional.
196 * Performance of simple atomic accesses has been greatly improved.
198 * Atomic fences now use light-weight syncs where possible, again providing
199 significant performance benefit.
201 * The PowerPC target now supports PIC levels (-fPIC vs. -fpic).
203 * PPC32 SVR4 now supports small-model PIC.
205 * There have been many smaller bug fixes and performance improvements.
207 Changes to the OCaml bindings
208 -----------------------------
210 * The bindings now require OCaml >=4.00.0, ocamlfind,
211 ctypes >=0.3.0 <0.4 and OUnit 2 if tests are enabled.
213 * The bindings can now be built using cmake as well as autoconf.
215 * LLVM 3.5 has, unfortunately, shipped a broken Llvm_executionengine
216 implementation. In LLVM 3.6, the bindings now fully support MCJIT,
217 however the interface is reworked from scratch using ctypes
218 and is not backwards compatible.
220 * Llvm_linker.Mode was removed following the changes in LLVM.
221 This breaks the interface of Llvm_linker.
223 * All combinations of ocamlc/ocamlc -custom/ocamlopt and shared/static
224 builds of LLVM are now supported.
226 * Absolute paths are not embedded into the OCaml libraries anymore.
227 Either OCaml >=4.02.2 must be used, which includes an rpath-like $ORIGIN
228 mechanism, or META file must be updated for out-of-tree installations;
231 * As usual, many more functions have been exposed to OCaml.
233 External Open Source Projects Using LLVM 3.6
234 ============================================
236 An exciting aspect of LLVM is that it is used as an enabling technology for
237 a lot of other language and tools projects. This section lists some of the
238 projects that have already been updated to work with LLVM 3.6.
243 Additional Information
244 ======================
246 A wide variety of additional information is available on the `LLVM web page
247 <http://llvm.org/>`_, in particular in the `documentation
248 <http://llvm.org/docs/>`_ section. The web page also contains versions of the
249 API documentation which is up-to-date with the Subversion version of the source
250 code. You can access versions of these documents specific to this release by
251 going into the ``llvm/docs/`` directory in the LLVM tree.
253 If you have any questions or comments about LLVM, please feel free to contact
254 us via the `mailing lists <http://llvm.org/docs/#maillist>`_.