from ：http://www.oschina.net/news/51084/gcc-4-9-0
GCC 4.9.0 公布，此版本号是个主要版本号更新，包含了 GCC 4.8.x 系列和之前的 GCC 版本号都没有的新特性，新特性很之多。下载地址：http://gcc.gnu.org/mirrors.html
移除 mudflap 执行时检查器，mudflap 选项保留，但没有不论什么效果.
对一些非常多老的系统和一些不维护的平台的支持在 4.9 版本号中声明为过世的，下一个版本号将永久删除，比如 Solaris 9
很多其它移植到 GCC 4.9 的信息请參考 移植指南
AddressSanitizer, a fast memory error detector, is now available on ARM.
UndefinedBehaviorSanitizer (ubsan), a fast undefined behavior detector,
has been added and can be enabled via -fsanitize=undefined.
Various computations will be instrumented to detect undefined behavior at
runtime. UndefinedBehaviorSanitizer is currently available for the C and
C++ languages.
Link-time optimization (LTO) improvements:Memory usage building Firefox with debug enabled was reduced from 15GB to 3.5GB; link time from 1700 seconds to 350 seconds.
Type merging was rewritten. The new implementation is significantly faster and uses less memory.
Better partitioning algorithm resulting in less streaming during link time.
Early removal of virtual methods reduces the size of object files and improves link-time memory usage and compile time.
Function bodies are now loaded on-demand and released early improving overall memory usage at link time.
C++ hidden keyed methods can now be optimized out.
When using a linker plugin, compiling with the -flto
option now generates slim objects files (.o)
which only contain intermediate language
representation for LTO. Use -ffat-lto-objects to
create files which contain additionally
the object code. To generate static libraries suitable
for LTO processing, use gcc-ar and
gcc-ranlib;
to list symbols from a slim object file use
gcc-nm.
(Requires that ar,
ranlib and nm have
been compiled with plugin support.)
Inter-procedural optimization improvements:
New type inheritance analysis module improving devirtualization.
Devirtualization now takes into account anonymous name-spaces and the
C++11 final keyword.
New speculative devirtualization pass (controlled by -fdevirtualize-speculatively.
Calls that were speculatively made direct are turned back to indirect where direct call is not cheaper.
Local aliases are introduced for symbols that are known to be semantically equivalent across shared libraries improving dynamic linking times.
Feedback directed optimization improvements:
Profiling of programs using C++ inline functions is now more reliable.
New time profiling determines typical order in which functions are executed.
A new function reordering pass (controlled by -freorder-functions)
significantly reduces startup time of large applications. Until
binutils support is completed, it is effective only with link-time
optimization.
Feedback driven indirect call removal and devirtualization now handle cross-module calls when link-time optimization is enabled.
Version 4.0 of the OpenMP
specification is now supported for the C and C++ compilers. The
new -fopenmp-simd option
can be used to enable OpenMP‘s SIMD directives, while ignoring other OpenMP
directives. The new -fsimd-cost-model= option
permits to tune the vectorization cost model for loops annotated with OpenMP
and Cilk Plus simd directives;-Wopenmp-simd warns
when the current costmodel overrides simd directives set by the user.
The -Wdate-time option
has been added for the C, C++ and Fortran compilers, which warns when
the __DATE__,
__TIME__ or __TIMESTAMP__ macros
are used. Those macros might prevent bit-wise-identical reproducible
compilations.
GNAT switched to Ada 2012 instead of Ada 2005 by default.
Support for colorizing diagnostics emitted by GCC has been added.
The-fdiagnostics-color=auto will enable it when
outputting to terminals,-fdiagnostics-color=always
unconditionally. The GCC_COLORS environment
variable can be used to customize the colors or disable coloring.
If GCC_COLORS variable
is present in the environment, the default is -fdiagnostics-color=auto,
otherwise -fdiagnostics-color=never.
Sample diagnostics output:
$ g++ -fdiagnostics-color=always -S -Wall test.C test.C: In function ‘int foo()’: test.C:1:14: warning: no return statement in function returning non-void [-Wreturn-type]
int foo () { } ^
test.C:2:46: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) instantiating ‘struct X<100>’
template <int N> struct X { static const int value = X<N-1>::value; }; template struct X<1000>; ^
test.C:2:46: recursively required from ‘const int X<999>::value’ test.C:2:46: required from ‘const int X<1000>::value’ test.C:2:88: required from here test.C:2:46: error: incomplete type ‘X<100>’ used in nested name specifier
With the new #pragma
GCC ivdep, the user can assert that there are no
loop-carried dependencies which would prevent concurrent execution of
consecutive iterations using SIMD (single instruction multiple
data) instructions.
Support for Cilk Plus has been
added and can be enabled with the -fcilkplus option.
Cilk Plus is an extension to the C and C++ languages to
support data and task parallelism. The present
implementation follows ABI version 1.2; all features
but _Cilk_for have
been implemented.
ISO C11 atomics (the _Atomic type
specifier and qualifier and the <stdatomic.h> header)
are now supported.
ISO C11 generic selections (_Generic keyword)
are now supported.
ISO C11 thread-local storage (_Thread_local,
similar to GNU C __thread)
is now supported.
ISO C11 support is now at a similar level of completeness to ISO C99
support: substantially complete modulo bugs, extended identifiers
(supported except for corner cases when-fextended-identifiers is
used), floating-point issues (mainly but not entirely relating to
optional C99 features from Annexes F and G) and the optional Annexes K
(Bounds-checking interfaces) and L (Analyzability).
A new C extension __auto_type provides
a subset of the functionality of C++11 auto in
GNU C.
The G++ implementation of C++1y return type deduction for normal functions has been updated to conform to N3638, the proposal accepted into the working paper. Most notably, it adds decltype(auto) for getting decltype semantics rather than the template argument deduction semantics of plain auto:
int& f(); auto i1 = f(); // int decltype(auto) i2 = f(); // int&
G++ supports C++1y lambda capture initializers:
[x = 42]{ ... };
Actually, they have been accepted since GCC 4.5, but now the compiler doesn‘t warn about them with -std=c++1y, and supports parenthesized and brace-enclosed initializers as well.
G++ supports C++1y variable length arrays. G++ has supported GNU/C99-style VLAs for a long time, but now additionally supports initializers and lambda capture by reference. In C++1y mode G++ will complain about VLA uses that are not permitted by the draft standard, such as forming a pointer to VLA type or applying sizeof to a VLA variable. Note that it now appears that VLAs will not be part of C++14, but will be part of a separate document and then perhaps C++17.
void f(int n) {
int a[n] = { 1, 2, 3 }; // throws std::bad_array_length if n < 3
[&a]{ for (int i : a) { cout << i << endl; } }();
&a; // error, taking address of VLA
}
G++ supports the C++1y [[deprecated]] attribute modulo bugs in the underlying [[gnu::deprecated]] attribute. Classes and functions can be marked deprecated and a diagnostic message added:
class A;
int bar(int n);
#if __cplusplus > 201103
class [[deprecated("A is deprecated in C++14; Use B instead")]] A;
[[deprecated("bar is unsafe; use foo() instead")]]
int bar(int n);
int foo(int n);
class B;
#endif
A aa; // warning: ‘A‘ is deprecated : A is deprecated in C++14; Use B instead
int j = bar(2); // warning: ‘int bar(int)‘ is deprecated : bar is unsafe; use foo() instead
G++ supports C++1y digit separators. Long numeric literals can be subdivided with a single quote ‘ to enhance readability:
int i = 1048576; int j = 1‘048‘576; int k = 0x10‘0000; int m = 0‘004‘000‘000; int n = 0b0001‘0000‘0000‘0000‘0000‘0000; double x = 1.602‘176‘565e-19; double y = 1.602‘176‘565e-1‘9;
G++ supports C++1y polymorphic lambdas.
// a functional object that will increment any type
auto incr = [](auto x) { return x++; };
Improved support for C++11, including:
support for <regex>;
The associative containers in <map> and
<set> and
the unordered associative containers
in <unordered_map> and <unordered_set>
meet the allocator-aware container
requirements;
Improved experimental support for the upcoming ISO C++ standard, C++14, including:
fixing constexpr member
functions without const;
implementation of the std::exchange() utility
function;
addressing tuples by type;
implemention of std::make_unique;
implemention of std::shared_lock;
making std::result_of SFINAE-friendly;
adding operator() to integral_constant;
adding user-defined literals for standard library types
std::basic_string,std::chrono::duration,
and std::complex;
adding two range overloads to non-modifying sequence oprations
std::equaland std::mismatch;
adding IO manipulators for quoted strings;
adding constexpr members
to <utility>,
<complex>, <chrono>,
and some containers;
adding compile-time std::integer_sequence;
adding cleaner transformation traits;
making <functional>s
operator functors easier to use
and more generic;
An implementation of std::experimental::optional.
An implementation of std::experimental::string_view.
The non-standard function std::copy_exception has
been deprecated and will be removed in a future
version. std::make_exception_ptr
should be used instead.
Compatibility notice:
Note that the argument passing ABI has changed for scalar dummy
arguments of typeINTEGER, REAL,
COMPLEX and LOGICAL,
which have both the VALUE and
theOPTIONAL attribute.
Due to the support of finalization, the virtual table associated
with polymorphic variables has changed.
Therefore, code containing CLASS should
be recompiled, including all files which
define derived types involved in the type definition used by
polymorphic variables. (Note: Due to the
incremented module version, trying to mix
old code with new code will usually give an error
message.)
Module files: The version of the module files (.mod)
has been incremented; additionally, module files
are now compressed. Fortran MODULEs
compiled by earlier GCC versions have to be
recompiled, when they are USEd
by files compiled with GCC 4.9, because GCC 4.9
is not able to read .mod
files of earlier GCC versions; attempting to do so gives
an error message. Note: The ABI of the produced
assembler data itself has not changed: object
files and libraries are fully compatible to older
versions. (Except for the next items.)
ABI changes:
GNU Fortran no longer deallocates allocatable variables or
allocatable components of variables declared in the main
program. Since Fortran 2008, the standard
explicitly states that variables declared in the
Fortran main program automatically have theSAVE
attribute.
When opening files, the close-on-exec flag is set if the system
supports such a feature. This is generally considered
good practice these days, but if there is a need
to pass file descriptors to child processes the
parent process must now remember to clear the
close-on-exec flag by calling fcntl(),
e.g. via ISO_C_BINDING,
before executing the child process.
The deprecated command-line option -fno-whole-file
has been removed. (-fwhole-file is
the default since GCC 4.6.) -fwhole-file/-fno-whole-file
continue to be accepted but do not influence the code
generation.
The compiler no longer unconditionally warns
about DO loops
with zero iterations. This warning is now controlled
by the -Wzerotrips option,
which is implied by -Wall.
The new NO_ARG_CHECK attribute
of the !GCC$ directive can
be used to disable the type-kind-rank (TKR) argument check
for a dummy argument. The feature is similar to ISO/IEC TS
29133:2012‘s TYPE(*),
except that it additionally also disables the rank check.
Variables with NO_ARG_CHECK have
to be dummy arguments and may only be used as argument
to ISO_C_BINDING‘s C_LOC
and as actual argument to another NO_ARG_CHECKdummy
argument; also the other constraints of TYPE(*) apply.
The dummy arguments should be declared as scalar or
assumed-size variable of type type(*) (recommended)
– or of type integer, real, complex
or logical.
With NO_ARG_CHECK,
a pointer to the data without further type or shape
information is passed, similar to C‘s void*.
Note that also TS 29113‘s type(*),dimension(..) accepts
arguments of any type and rank; contrary to NO_ARG_CHECK assumed-rank
arguments pass an array descriptor which contains the
array shape and stride of the argument.
Finalization is now supported. Note that finalization is currently only done for a subset of the situations in which it should occur.
Experimental support for scalar character components with deferred length (i.e. allocatable string length) in derived types has been added. (Deferred-length character variables are supported since GCC 4.6.)
When STOP or ERROR
STOP is used to terminate the
execution and any exception (but inexact) is signaling, a warning is
printed to ERROR_UNIT,
indicating which exceptions are signaling.
The -ffpe-summary= command-line option can be
used to fine-tune for which exception the warning
should be shown.
Rounding on input (READ)
is now handled on systems where strtod honours
the rounding mode. (For output, rounding is
supported since GCC 4.5.) Note that for input, the
compatible rounding
mode is handled as nearest
(i.e., for a tie, rounding to an even last significant
[cf. IEC 60559:1989] – while compatible rounds
away from zero for a tie).
GCC 4.9 provides a complete implementation of the Go 1.2.1 release.
The ARMv8-A crypto and CRC instructions are now supported through
intrinsics. These are enabled when the architecture supports
these and are available through the-march=armv8-a+crc
and -march=armv8-a+crypto options.
Initial support for ILP32 has now been added to the
compiler. This is now available through the command line option
-mabi=ilp32.
Support for ILP32 is considered experimental as the ABI
specification is still beta.
Coverage of more of the ISA including the SIMD extensions has been added. The Advanced SIMD intrinsics have also been improved.
The new local register allocator (LRA) is now on by default for the AArch64 backend.
The REE (Redundant extension elimination) pass has now been enabled by default for the AArch64 backend.
Tuning for the Cortex-A53 and Cortex-A57 has been improved.
Initial big.LITTLE tuning support for the combination of Cortex-A57
and Cortex-A53 was added through the -mcpu=cortex-a57.cortex-a53
option.
A number of structural changes have been made to both the ARM and AArch64 backends to facilitate improved code-generation.
Use of Advanced SIMD (Neon) for 64-bit scalar computations has been disabled
by default. This was found to generate better code in only a small number of
cases. It can be turned back on with the
-mneon-for-64bits option.
Further support for the ARMv8-A architecture, notably implementing
the restriction around IT blocks in the Thumb32 instruction set
has been added. The -mrestrict-itoption
can be used with -march=armv7-a or
the -march=armv7ve options
to make code generation fully compatible with the
deprecated instructions in ARMv8-A.
Support has now been added for the ARMv7ve variant of the
architecture. This can be used by the -march=armv7ve option.
The ARMv8-A crypto and CRC instructions are now supported through
intrinsics and are available through the -march=armv8-a+crc
and mfpu=crypto-neon-fp-armv8 options.
LRA is now on by default for the ARM target. This can be turned off
using the -mno-lraoption.
This option is purely transitionary command line option
and will be removed in a future release. We are
interested in any bug reports regarding functional and
performance regressions with LRA.
A new option -mslow-flash-data to
improve performance of programs fetching data on slow
flash memory has now been introduced for the ARMv7-M
profile cores.
A new option -mpic-data-is-text-relative for
targets that allows data segments to be relative to text
segments has been added. This is on by default for all
targets except VxWorks RTP.
A number of infrastructural changes have been made to both the ARM and AArch64 backends to facilitate improved code-generation.
GCC now supports Cortex-A12 and the Cortex-R7 through the
-mcpu=cortex-a12 and-mcpu=cortex-r7 options.
GCC now has tuning for the Cortex-A57 and Cortex-A53
through the -mcpu=cortex-a57and -mcpu=cortex-a53
options.
Initial big.LITTLE tuning support for the combination of Cortex-A57
and Cortex-A53 was added through the -mcpu=cortex-a57.cortex-a53
option. Similar support was added for the
combination of Cortex-A15 and Cortex-A7 through the-mcpu=cortex-a15.cortex-a7
option.
Further performance optimizations for the Cortex-A15 and the Cortex-M4 have been added.
A number of code generation improvements for Thumb2 to reduce code size when compiling for the M-profile processors.
-mfpmath=sse is
now implied by -ffast-math on
all targets where SSE2 is supported.
Intel AVX-512 support was added to GCC. That includes inline
assembly support, new registers and extending existing ones,
new intrinsics (covered by corresponding testsuite), and
basic autovectorization. AVX-512 instructions are
available via the following GCC switches: AVX-512
foundation instructions: -mavx512f,
AVX-512 prefetch instructions:-mavx512pf,
AVX-512 exponential and reciprocal
instructions: -mavx512er,
AVX-512 conflict detection instructions: -mavx512cd.
It is now possible to call x86 intrinsics from select functions in
a file that are tagged with the corresponding target attribute
without having to compile the entire file with the-mxxx option.
This improves the usability of x86 intrinsics and is
particularly useful when doing Function Multiversioning.
GCC now supports the new Intel microarchitecture named Silvermont
through-march=silvermont.
GCC now supports the new Intel microarchitecture named Broadwell
through-march=broadwell.
Optimizing for other Intel microarchitectures have been renamed
to -march=nehalem,westmere,
sandybridge, ivybridge,
haswell, bonnell.
-march=generic has
been retuned for better support of Intel core and AMD
Bulldozer architectures. Performance of AMD K7, K8,
Intel Pentium-M, and Pentium4 based CPUs is no longer considered
important for generic.
-mtune=intel can
now be used to generate code running well on the most
current Intel processors, which are Haswell and Silvermont
for GCC 4.9.
Support to encode 32-bit assembly instructions in 16-bit format
is now available through the -m16 command-line
option.
Better inlining of memcpy and memset that
is aware of value ranges and produces shorter alignment prologues.
-mno-accumulate-outgoing-args is
now honored when unwind information is output.
Argument accumulation is also now turned off for
portions of programs optimized for size.
Support for new AMD family 15h processors (Excavator core)
is now available through the -march=bdver4 and
-mtune=bdver4 options.
A new command-line option -mcpu= has
been added to the MSP430 backend. This option is used to specify
the ISA to be used. Accepted values are msp430 (the
default),msp430x and msp430xv2.
The ISA is no longer deduced from the -mmcu= option
as there are far too many different MCU names. The -mmcu= option
is still supported, and this is still used to select linker
scripts and generate a C preprocessor symbol that will be recognised by
the msp430.h header
file.
A new nds32 port supports the 32-bit architecture from Andes Technology Corporation.
The port provides initial support for the V2, V3, V3m instruction set architectures.
A port for the Altera Nios II has been contributed by Mentor Graphics.
GCC now supports Power ISA 2.07, which includes support for Hardware Transactional Memory (HTM), Quadword atomics and several VMX and VSX additions, including Crypto, 64-bit integer, 128-bit integer and decimal integer operations.
Support for the POWER8 processor is now available through the
-mcpu=power8 and-mtune=power8 options.
The libitm library has been modified to add a HTM fastpath that automatically uses POWER‘s HTM hardware instructions when it is executing on a HTM enabled processor.
Support for the new powerpc64le-linux platform has been added. It defaults to generating code that conforms to the ELFV2 ABI.
Support for the Transactional Execution Facility included with
the IBM zEnterprise zEC12 processor has been added. A set of
GCC style builtins as well as XLC style builtins are
provided. The builtins are enabled by default when using
the -march=zEC12 option
but can explicitly be disabled with -mno-htm.
Using the GCC builtins also libitm supports hardware
transactions on S/390.
The hotpatch features allows to prepare functions for
hotpatching. A certain amount of bytes is reserved before the
function entry label plus a NOP is inserted at its very
beginning to implement a backward jump when applying a
patch. The feature can either be enabled via command line
option -mhotpatch for
a compilation unit or can be enabled per function using
the hotpatch
attribute.
The shrink wrap optimization is now supported on S/390 and enabled by default.
A major rework of the routines to determine which registers
need to be saved and restored in function prologue/epilogue now
allow to use floating point registers as save slots. This
will happen for certain leaf function with -march=z10
or higher.
The LRA rtl pass replaces reload by default on S/390.
The port now allows to specify the RX100, RX200, and RX600 processors with the command line options -mcpu=rx100, -mcpu=rx200 and -mcpu=rx600.
Minor improvements to code generated for integer arithmetic and code that involves the T bit.
Added support for the SH2A clips and clipu
instructions. The compiler will now try to utilize them for
min/max expressions such as max
(-128, min (127, x)).
Added support for the cmp/str instruction
through built-in functions such as__builtin_strlen.
When not optimizing for size, the compiler will now expand
calls to e.g.strlen as
an inlined sequences which utilize the cmp/str instruction.
Improved code generated around volatile memory loads and stores.
The option -mcbranchdi has
been deprecated. Specifying it will result in a warning and
will not influence code generation.
The option -mcmpeqdi has
been deprecated. Specifying it will result in a warning and
will not influence code generation.
具体内容请看发行说明。
GCC 4.9.0 公布，提升 C++11 和 C++14 特性,布布扣,bubuko.com
GCC 4.9.0 公布，提升 C++11 和 C++14 特性
原文：http://www.cnblogs.com/mfrbuaa/p/3761608.html