File _patchinfo of Package patchinfo.3147

<patchinfo incident="3147">
  <category>optional</category>
  <issue tracker="bnc" id="983206">[Toolchain Module] Summer 2016 Refresh</issue>
  <issue tracker="fate" id="320851"/>
  <rating>low</rating>
  <packager>rguenther</packager>
  <summary>Optional update for gcc6</summary>
  <description>
This update ships the GNU Compiler Collection (GCC) in version 6.2.

This update is shipped in two parts:

- SUSE Linux Enterprise Server 12 and Desktop:

  The runtime libraries libgcc_s1, libstdc++6, libatomic1, libgomp1, libitm1
  and some others can now be used by GCC 6 built binaries.

- SUSE Linux Enterprise 12 Toolchain Module:

  The Toolchain module received the GCC 6 compiler suite with this update.

Changes:

- The default mode for C++ is now -std=gnu++14 instead of -std=gnu++98.

Generic Optimization improvements:

- UndefinedBehaviorSanitizer gained a new sanitization option,
  -fsanitize=bounds-strict, which enables strict checking of array
  bounds. In particular, it enables -fsanitize=bounds as well as
  instrumentation of flexible array member-like arrays.
- Type-based alias analysis now disambiguates accesses to different
  pointers. This improves precision of the alias oracle by about 20-30%
  on higher-level C++ programs. Programs doing invalid type punning of
  pointer types may now need -fno-strict-aliasing to work correctly.
- Alias analysis now correctly supports weakref and alias attributes. This
  makes it possible to access both a variable and its alias in one
  translation unit which is common with link-time optimization.
- Value range propagation now assumes that the this pointer of C++
  member functions is non-null. This eliminates common null pointer checks
  but also breaks some non-conforming code-bases (such as Qt-5, Chromium,
  KDevelop). As a temporary work-around -fno-delete-null-pointer-checks
  can be used. Wrong code can be identified by using -fsanitize=undefined.
- Various Link-time optimization improvements.
- Inter-procedural optimization improvements:
    - Basic jump threading is now performed before profile construction
      and inline analysis, resulting in more realistic size and time
      estimates that drive the heuristics of the of inliner and function
      cloning passes.
    - Function cloning now more aggressively eliminates unused function
      parameters.
- Compared to GCC 5, the GCC 6 release series includes a much improved
  implementation of the OpenACC 2.0a specification.

C language specific improvements:

- Version 4.5 of the OpenMP specification is now supported in the C and C++ compilers.
- Source locations for the C and C++ compilers are now tracked as ranges,
  rather than just points, making it easier to identify the subexpression
  of interest within a complicated expression. In addition, there is
  now initial support for precise diagnostic locations within strings,
- Diagnostics can now contain "fix-it hints", which are displayed in
  context underneath the relevant source code.
- The C and C++ compilers now offer suggestions for misspelled field names.
- New command-line options have been added for the C and C++ compilers:
    - -Wshift-negative-value warns about left shifting a negative value.
    - -Wshift-overflow warns about left shift overflows. This warning is
      enabled by default. -Wshift-overflow=2 also warns about left-shifting
      1 into the sign bit.
    - -Wtautological-compare warns if a self-comparison always evaluates
      to true or false. This warning is enabled by -Wall.
    - -Wnull-dereference warns if the compiler detects paths that
      trigger erroneous or undefined behavior due to dereferencing a null
      pointer. This option is only active when -fdelete-null-pointer-checks
      is active, which is enabled by optimizations in most targets. The
      precision of the warnings depends on the optimization options used.
    - -Wduplicated-cond warns about duplicated conditions in an if-else-if chain.
    - -Wmisleading-indentation warns about places where the indentation
      of the code gives a misleading idea of the block structure of the
      code to a human reader. This warning is enabled by -Wall.
- The C and C++ compilers now emit saner error messages if merge-conflict markers
  are present in a source file.

C improvements:

- It is possible to disable warnings when an initialized field
  of a structure or a union with side effects is being overridden
  when using designated initializers via a new warning option
  -Woverride-init-side-effects.
- A new type attribute scalar_storage_order applying to structures
  and unions has been introduced. It specifies the storage order (aka
  endianness) in memory of scalar fields in structures or unions.

C++ improvements:

- The default mode has been changed to -std=gnu++14.
- C++ Concepts are now supported when compiling with -fconcepts.
- -flifetime-dse is more aggressive in dead-store elimination in situations where
  a memory store to a location precedes a constructor to that memory location.
- G++ now supports C++17 fold expressions, u8 character literals, extended static_assert,
  and nested namespace definitions.
- G++ now allows constant evaluation for all non-type template arguments.
- G++ now supports C++ Transactional Memory when compiling with -fgnu-tm.

libstdc++ improvements:

- Extensions to the C++ Library to support mathematical special functions
  (ISO/IEC 29124:2010), thanks to Edward Smith-Rowland.
- Experimental support for C++17.
- An experimental implementation of the File System TS.
- Experimental support for most features of the second version of the
  Library Fundamentals TS. This includes polymorphic memory resources and
  array support in shared_ptr, thanks to Fan You.
- Some assertions checked by Debug Mode can now also be enabled by
  _GLIBCXX_ASSERTIONS. The subset of checks enabled by the new macro have
  less run-time overhead than the full _GLIBCXX_DEBUG checks and don't
  affect the library ABI, so can be enabled per-translation unit.

Fortran improvements:

- Fortran 2008 SUBMODULE support.
- Fortran 2015 EVENT_TYPE, EVENT_POST, EVENT_WAIT, and EVENT_QUERY support.
- Improved support for Fortran 2003 deferred-length character variables.
- Improved support for OpenMP and OpenACC.
- The MATMUL intrinsic is now inlined for straightforward cases if
  front-end optimization is active. The maximum size for inlining can be
  set to n with the -finline-matmul-limit=n option and turned off with
  -finline-matmul-limit=0.
- The -Wconversion-extra option will warn about REAL constants which
  have excess precision for their kind.
- The -Winteger-division option has been added, which warns about
  divisions of integer constants which are truncated. This option is
  included in -Wall by default.

Architecture improvements:

- AArch64 received a lot of improvements.

IA-32/x86-64 improvements:

- GCC now supports the Intel CPU named Skylake with AVX-512 extensions
  through -march=skylake-avx512. The switch enables the following ISA
  extensions: AVX-512F, AVX512VL, AVX-512CD, AVX-512BW, AVX-512DQ.
- Support for new AMD instructions monitorx and mwaitx has been
  added. This includes new intrinsic and built-in support. It is enabled
  through option -mmwaitx. The instructions monitorx and mwaitx implement
  the same functionality as the old monitor and mwait instructions. In
  addition mwaitx adds a configurable timer. The timer value is received
  as third argument and stored in register %ebx.
- x86-64 targets now allow stack realignment from a word-aligned stack
  pointer using the command-line option -mstackrealign or __attribute__
  ((force_align_arg_pointer)). This allows functions compiled with
  a vector-aligned stack to be invoked from objects that keep only
  word-alignment.
- Support for address spaces __seg_fs, __seg_gs, and __seg_tls. These
  can be used to access data via the %fs and %gs segments without having
  to resort to inline assembly.
- Support for AMD Zen (family 17h) processors is now available through
  the -march=znver1 and -mtune=znver1 options.

PowerPC / PowerPC64 / RS6000 improvements:

- PowerPC64 now supports IEEE 128-bit floating-point using the
  __float128 data type. In GCC 6, this is not enabled by default, but you
  can enable it with -mfloat128. The IEEE 128-bit floating-point support
  requires the use of the VSX instruction set. IEEE 128-bit floating-point
  values are passed and returned as a single vector value. The software
  emulator for IEEE 128-bit floating-point support is only built on
  PowerPC GNU/Linux systems where the default CPU is at least power7. On
  future ISA 3.0 systems (POWER 9 and later), you will be able to use the
  -mfloat128-hardware option to use the ISA 3.0 instructions that support
  IEEE 128-bit floating-point. An additional type (__ibm128) has been added
  to refer to the IBM extended double type that normally implements long
  double. This will allow for a future transition to implementing long
  double with IEEE 128-bit floating-point.
- Basic support has been added for POWER9 hardware that will use the
  recently published OpenPOWER ISA 3.0 instructions. The following new
  switches are available:
     - -mcpu=power9: Implement all of the ISA 3.0 instructions supported by
       the compiler.
     - -mtune=power9: In the future, apply tuning for POWER9 systems. Currently,
       POWER8 tunings are used.
     - -mmodulo: Generate code using the ISA 3.0 integer instructions (modulus,
       count trailing zeros, array index support, integer multiply/add).
     - -mpower9-fusion: Generate code to suitably fuse instruction sequences for
       a POWER9 system.
     - -mpower9-dform: Generate code to use the new D-form (register+offset) memory
       instructions for the vector registers.
     - -mpower9-vector: Generate code using the new ISA 3.0 vector (VSX or Altivec)
       instructions.
     - -mpower9-minmax: Reserved for future development.
     - -mtoc-fusion: Keep TOC entries together to provide more fusion opportunities.
- New constraints have been added to support IEEE 128-bit floating-point and ISA 3.0
  instructions.
- Support has been added for __builtin_cpu_is() and __builtin_cpu_supports(),
  allowing for very fast access to AT_PLATFORM, AT_HWCAP, and AT_HWCAP2 values.
  This requires use of glibc 2.23 or later.
- All hardware transactional memory builtins now correctly behave as
  memory barriers. Programmers can use #ifdef __TM_FENCE__ to determine
  whether their "old" compiler treats the builtins as barriers.
- Split-stack support has been added for gccgo on PowerPC64 for both
  big- and little-endian (but not for 32-bit). The gold linker from at
  least binutils 2.25.1 must be available in the PATH when configuring and
  building gccgo to enable split stack. (The requirement for binutils 2.25.1
  applies to PowerPC64 only.) The split-stack feature allows a small initial
  stack size to be allocated for each goroutine, which increases as needed.
- GCC on PowerPC now supports the standard lround function.
- The "q", "S", "T", and "t" asm-constraints have been removed.
- The "b", "B", "m", "M", and "W" format modifiers have been removed.

S/390, System z, IBM z Systems improvements:

- Support for the IBM z13 processor has been added. When using the
  -march=z13 option, the compiler will generate code making use of the
  new instructions and registers introduced with the vector extension
  facility. The -mtune=z13 option enables z13 specific instruction
  scheduling without making use of new instructions.
- Compiling code with -march=z13 reduces the default alignment of vector
  types bigger than 8 bytes to 8. This is an ABI change and care must be
  taken when linking modules compiled with different arch levels which
  interchange variables containing vector type values. For newly compiled
  code the GNU linker will emit a warning.
- The -mzvector option enables a C/C++ language extension. This extension
  provides a new keyword vector which can be used to define vector type
  variables. (Note: This is not available when enforcing strict standard
  compliance e.g. with -std=c99. Either enable GNU extensions with
  e.g. -std=gnu99 or use __vector instead of vector.)
- Additionally a set of overloaded builtins is provided which is partially
  compatible to the PowerPC Altivec builtins. In order to make use of
  these builtins the vecintrin.h header file needs to be included.
- The new command line options -march=native, and -mtune=native are now
  available on native IBM z Systems. Specifying these options will cause
  GCC to auto-detect the host CPU and rewrite these options to the optimal
  setting for that system. If GCC is unable to detect the host CPU these
  options have no effect.
- The IBM z Systems port now supports target attributes and
  pragmas. Please refer to the documentation for details of available
  attributes and pragmas as well as usage instructions.
- -fsplit-stack is now supported as part of the IBM z Systems port. This
  feature requires a recent gold linker to be used.
- Support for the g5 and g6 -march=/-mtune= CPU level switches has been
  deprecated and will be removed in a future GCC release. -m31 from now
  on defaults to -march=z900 if not specified otherwise. -march=native on
  a g5/g6 machine will default to -march=z900.

An even more detailed list of features can be found at:
https://gcc.gnu.org/gcc-6/changes.html
</description>
</patchinfo>