-======================
-LLVM 3.5 Release Notes
-======================
+========================
+LLVM 7.0.0 Release Notes
+========================
.. contents::
:local:
.. warning::
- These are in-progress notes for the upcoming LLVM 3.6 release. You may
- prefer the `LLVM 3.5 Release Notes <http://llvm.org/releases/3.5.0/docs
- /ReleaseNotes.html>`_.
+ These are in-progress notes for the upcoming LLVM 7 release.
+ Release notes for previous releases can be found on
+ `the Download Page <http://releases.llvm.org/download.html>`_.
Introduction
============
This document contains the release notes for the LLVM Compiler Infrastructure,
-release 3.6. Here we describe the status of LLVM, including major improvements
+release 7.0.0. Here we describe the status of LLVM, including major improvements
from the previous release, improvements in various subprojects of LLVM, and
some of the current users of the code. All LLVM releases may be downloaded
from the `LLVM releases web site <http://llvm.org/releases/>`_.
For more information about LLVM, including information about the latest
release, please check out the `main LLVM web site <http://llvm.org/>`_. If you
have questions or comments, the `LLVM Developer's Mailing List
-<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ is a good place to send
+<http://lists.llvm.org/mailman/listinfo/llvm-dev>`_ is a good place to send
them.
Note that if you are reading this file from a Subversion checkout or the main
Non-comprehensive list of changes in this release
=================================================
-
.. NOTE
For small 1-3 sentence descriptions, just add an entry at the end of
this list. If your description won't fit comfortably in one bullet
functionality, or simply have a lot to talk about), see the `NOTE` below
for adding a new subsection.
-* Support for AuroraUX has been removed.
+* Libraries have been renamed from 7.0 to 7. This change also impacts
+ downstream libraries like lldb.
+
+* The LoopInstSimplify pass (-loop-instsimplify) has been removed.
+
+* Symbols starting with ``?`` are no longer mangled by LLVM when using the
+ Windows ``x`` or ``w`` IR mangling schemes.
+
+* A new tool named :doc:`llvm-exegesis <CommandGuide/llvm-exegesis>` has been
+ added. :program:`llvm-exegesis` automatically measures instruction scheduling
+ properties (latency/uops) and provides a principled way to edit scheduling
+ models.
+
+* A new tool named :doc:`llvm-mca <CommandGuide/llvm-mca>` has been added.
+ :program:`llvm-mca` is a static performance analysis tool that uses
+ information available in LLVM to statically predict the performance of
+ machine code for a specific CPU.
+
+* The optimization flag to merge constants (-fmerge-all-constants) is no longer
+ applied by default.
+
+* Optimization of floating-point casts is improved. This may cause surprising
+ results for code that is relying on the undefined behavior of overflowing
+ casts. The optimization can be disabled by specifying a function attribute:
+ "strict-float-cast-overflow"="false". This attribute may be created by the
+ clang option ``-fno-strict-float-cast-overflow``.
+ Code sanitizers can be used to detect affected patterns. The option for
+ detecting this problem alone is "-fsanitize=float-cast-overflow":
+
+.. code-block:: c
+
+ int main() {
+ float x = 4294967296.0f;
+ x = (float)((int)x);
+ printf("junk in the ftrunc: %f\n", x);
+ return 0;
+ }
-* Added support for a `native object file-based bitcode wrapper format
- <BitCodeFormat.html#native-object-file>`_.
+.. code-block:: bash
-* ... next change ...
+ clang -O1 ftrunc.c -fsanitize=float-cast-overflow ; ./a.out
+ ftrunc.c:5:15: runtime error: 4.29497e+09 is outside the range of representable values of type 'int'
+ junk in the ftrunc: 0.000000
+
+* ``LLVM_ON_WIN32`` is no longer set by ``llvm/Config/config.h`` and
+ ``llvm/Config/llvm-config.h``. If you used this macro, use the compiler-set
+ ``_WIN32`` instead which is set exactly when ``LLVM_ON_WIN32`` used to be set.
+
+* The ``DEBUG`` macro has been renamed to ``LLVM_DEBUG``, the interface remains
+ the same. If you used this macro you need to migrate to the new one.
+ You should also clang-format your code to make it easier to integrate future
+ changes locally. This can be done with the following bash commands:
+
+.. code-block:: bash
+
+ git grep -l 'DEBUG' | xargs perl -pi -e 's/\bDEBUG\s?\(/LLVM_DEBUG(/g'
+ git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
+
+* Early support for UBsan, X-Ray instrumentation and libFuzzer (x86 and x86_64) for OpenBSD. Support for MSan
+ (x86_64), X-Ray instrumentation and libFuzzer (x86 and x86_64) for FreeBSD.
+
+* ``SmallVector<T, 0>`` shrank from ``sizeof(void*) * 4 + sizeof(T)`` to
+ ``sizeof(void*) + sizeof(unsigned) * 2``, smaller than ``std::vector<T>`` on
+ 64-bit platforms. The maximum capacity is now restricted to ``UINT32_MAX``.
+ Since SmallVector doesn't have the exception-safety pessimizations some
+ implementations saddle std::vector with and is better at using ``realloc``,
+ it's now a better choice even on the heap (although when TinyPtrVector works,
+ it's even smaller).
+
+* Preliminary/experimental support for DWARF v5 debugging information,
+ including the new .debug_names accelerator table. DWARF emitted at ``-O0``
+ should be fully DWARF v5 compliant. Type units and split DWARF are known
+ not to be compliant, and higher optimization levels will still emit some
+ information in v4 format.
+
+* Note..
.. NOTE
If you would like to document a larger change, then you can add a
Makes programs 10x faster by doing Special New Thing.
-Prefix data rework
-------------------
+Changes to the LLVM IR
+----------------------
-The semantics of the ``prefix`` attribute have been changed. Users
-that want the previous ``prefix`` semantics should instead use
-``prologue``. To motivate this change, let's examine the primary
-usecases that these attributes aim to serve,
+* The signatures for the builtins @llvm.memcpy, @llvm.memmove, and @llvm.memset
+ have changed. Alignment is no longer an argument, and are instead conveyed as
+ parameter attributes.
- 1. Code sanitization metadata (e.g. Clang's undefined behavior
- sanitizer)
+* invariant.group.barrier has been renamed to launder.invariant.group.
- 2. Function hot-patching: Enable the user to insert ``nop`` operations
- at the beginning of the function which can later be safely replaced
- with a call to some instrumentation facility.
+* invariant.group metadata can now refer only empty metadata nodes.
- 3. Language runtime metadata: Allow a compiler to insert data for
- use by the runtime during execution. GHC is one example of a
- compiler that needs this functionality for its
- tables-next-to-code functionality.
+Changes to the ARM Backend
+--------------------------
-Previously ``prefix`` served cases (1) and (2) quite well by allowing the user
-to introduce arbitrary data at the entrypoint but before the function
-body. Case (3), however, was poorly handled by this approach as it
-required that prefix data was valid executable code.
+ During this release ...
-In this release the concept of prefix data has been redefined to be
-data which occurs immediately before the function entrypoint (i.e. the
-symbol address). Since prefix data now occurs before the function
-entrypoint, there is no need for the data to be valid code.
-The previous notion of prefix data now goes under the name "prologue
-data" to emphasize its duality with the function epilogue.
+Changes to the MIPS Target
+--------------------------
-The intention here is to handle cases (1) and (2) with prologue data and
-case (3) with prefix data. See the language reference for further details
-on the semantics of these attributes.
+ During this release ...
-This refactoring arose out of discussions_ with Reid Kleckner in
-response to a proposal to introduce the notion of symbol offsets to
-enable handling of case (3).
-.. _discussions: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073235.html
+Changes to the PowerPC Target
+-----------------------------
+ During this release ...
-Changes to the ARM Backend
---------------------------
+Changes to the X86 Target
+-------------------------
During this release ...
+Changes to the AMDGPU Target
+-----------------------------
-Changes to the MIPS Target
---------------------------
+ During this release ...
-During this release ...
+Changes to the AVR Target
+-----------------------------
-Changes to the PowerPC Target
+ During this release ...
+
+Changes to the OCaml bindings
-----------------------------
-During this release ...
+* Remove ``add_bb_vectorize``.
-External Open Source Projects Using LLVM 3.6
-============================================
-An exciting aspect of LLVM is that it is used as an enabling technology for
-a lot of other language and tools projects. This section lists some of the
-projects that have already been updated to work with LLVM 3.6.
+Changes to the C API
+--------------------
-* A project
+* Remove ``LLVMAddBBVectorizePass``. The implementation was removed and the C
+ interface was made a deprecated no-op in LLVM 5. Use
+ ``LLVMAddSLPVectorizePass`` instead to get the supported SLP vectorizer.
+
+Changes to the DAG infrastructure
+---------------------------------
+* ADDC/ADDE/SUBC/SUBE are now deprecated and will default to expand. Backends
+ that wish to continue to use these opcodes should explicitely request so
+ using ``setOperationAction`` in their ``TargetLowering``. New backends
+ should use UADDO/ADDCARRY/USUBO/SUBCARRY instead of the deprecated opcodes.
+
+* The SETCCE opcode has now been removed in favor of SETCCCARRY.
+
+External Open Source Projects Using LLVM 7
+==========================================
+
+* A project...
Additional Information
If you have any questions or comments about LLVM, please feel free to contact
us via the `mailing lists <http://llvm.org/docs/#maillist>`_.
-
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