initial import of GCC 12.3.0.

major changes in GCC 11 included:

- The default mode for C++ is now -std=gnu++17 instead of -std=gnu++14.
- When building GCC itself, the host compiler must now support C++11,
rather than C++98.
- Some short options of the gcov tool have been renamed: -i to -j and
-j to -H.
- ThreadSanitizer improvements.
- Introduce Hardware-assisted AddressSanitizer support.
- For targets that produce DWARF debugging information GCC now defaults
to DWARF version 5. This can produce up to 25% more compact debug
information compared to earlier versions.
- Many optimisations.
- The existing malloc attribute has been extended so that it can be
used to identify allocator/deallocator API pairs. A pair of new
-Wmismatched-dealloc and -Wmismatched-new-delete warnings are added.
- Other new warnings:
-Wsizeof-array-div, enabled by -Wall, warns about divisions of two
sizeof operators when the first one is applied to an array and the
divisor does not equal the size of the array element.
-Wstringop-overread, enabled by default, warns about calls to string
functions reading past the end of the arrays passed to them as
arguments.
-Wtsan, enabled by default, warns about unsupported features in
ThreadSanitizer (currently std::atomic_thread_fence).
- Enchanced warnings:
-Wfree-nonheap-object detects many more instances of calls to
deallocation functions with pointers not returned from a dynamic
memory allocation function.
-Wmaybe-uninitialized diagnoses passing pointers or references to
uninitialized memory to functions taking const-qualified arguments.
-Wuninitialized detects reads from uninitialized dynamically
allocated memory.
-Warray-parameter warns about functions with inconsistent array forms.
-Wvla-parameter warns about functions with inconsistent VLA forms.
- Several new features from the upcoming C2X revision of the ISO C
standard are supported with -std=c2x and -std=gnu2x.
- Several C++20 features have been implemented.
- The C++ front end has experimental support for some of the upcoming
C++23 draft.
- Several new C++ warnings.
- Enhanced Arm, AArch64, x86, and RISC-V CPU support.
- The implementation of how program state is tracked within
-fanalyzer has been completely rewritten with many enhancements.

see https://gcc.gnu.org/gcc-11/changes.html for a full list.

major changes in GCC 12 include:

- An ABI incompatibility between C and C++ when passing or returning
by value certain aggregates containing zero width bit-fields has
been discovered on various targets. x86-64, ARM and AArch64
will always ignore them (so there is a C ABI incompatibility
between GCC 11 and earlier with GCC 12 or later), PowerPC64 ELFv2
always take them into account (so there is a C++ ABI
incompatibility, GCC 4.4 and earlier compatible with GCC 12 or
later, incompatible with GCC 4.5 through GCC 11). RISC-V has
changed the handling of these already starting with GCC 10. As
the ABI requires, MIPS takes them into account handling function
return values so there is a C++ ABI incompatibility with GCC 4.5
through 11.
- STABS: Support for emitting the STABS debugging format is
deprecated and will be removed in the next release. All ports now
default to emit DWARF (version 2 or later) debugging info or are
obsoleted.
- Vectorization is enabled at -O2 which is now equivalent to the
original -O2 -ftree-vectorize -fvect-cost-model=very-cheap.
- GCC now supports the ShadowCallStack sanitizer.
- Support for __builtin_shufflevector compatible with the clang
language extension was added.
- Support for attribute unavailable was added.
- Support for __builtin_dynamic_object_size compatible with the
clang language extension was added.
- New warnings:
-Wbidi-chars warns about potentially misleading UTF-8
bidirectional control characters.
-Warray-compare warns about comparisons between two operands of
array type.
- Some new features from the upcoming C2X revision of the ISO C
standard are supported with -std=c2x and -std=gnu2x.
- Several C++23 features have been implemented.
- Many C++ enhancements across warnings and -f options.

see https://gcc.gnu.org/gcc-12/changes.html for a full list.

initial import of GCC 10.3.0. main changes include:

caveats:
- ABI issue between c++14 and c++17 fixed
- profile mode is removed from libstdc++
- -fno-common is now the default

new features:
- new flags -fallocation-dce, -fprofile-partial-training,
-fprofile-reproducible, -fprofile-prefix-path, and -fanalyzer
- many new compile and link time optimisations
- enhanced drive optimisations
- openacc 2.6 support
- openmp 5.0 features
- new warnings: -Wstring-compare and -Wzero-length-bounds
- extended warnings: -Warray-bounds, -Wformat-overflow,
-Wrestrict, -Wreturn-local-addr, -Wstringop-overflow,
-Warith-conversion, -Wmismatched-tags, and -Wredundant-tags
- some likely C2X features implemented
- more C++20 implemented
- many new arm & intel CPUs known

hundreds of reported bugs are fixed. full list of changes
can be found at:

https://gcc.gnu.org/gcc-10/changes.html

branches: 1.1.1.1.2; 1.1.1.1.4;
import GCC 8.4. it fixes at least these 210 PRs in GCC bugzilla:

90095 93348 89906 89766 86747 87770 89588 89753 88235 89762 89684 89946
89965 90010 90026 90733 90810 90840 90842 90867 91623 92930 93073 93402
93505 93576 93744 93820 93908 85762 86429 86521 87327 87480 87513 87554
87685 87748 88183 88380 88394 88419 88690 88820 89381 89422 89576 89831
89917 90951 92003 92852 93140 80791 89358 89970 90899 89212 89419 92745
93684 93789 88273 91826 92376 84746 89497 89595 89664 89711 89725 90018
90316 90900 91108 91293 91772 92763 93054 93246 90313 92420 93434 93767
88530 89517 91838 79262 84680 85459 85711 85860 86567 87008 87651 87652
88469 89546 89827 90197 93072 93241 81800 89190 85400 91472 91854 92095
92131 92575 93704 60228 61414 65782 89405 89498 89703 89752 90187 90193
90898 91401 91450 91665 92296 92384 92438 92615 92648 92723 92732 92904
93087 93228 93515 93905 82081 92859 89712 89876 92106 82645 78552 81266
85965 89102 90165 90299 90532 91436 92059 93205 93325 93562 90359 91280
91375 92674 92704 93439 92768 80938 83361 90563 92113 92961 87833 89848
89902 89903 92022 93828 78179 79221 82920 84016 87015 88075 89077 89266
90454 90634 91226 92154 92664 92886 93065 92692 92629 80590 91944 92899
92977 93463 89601 88025 91660 91845 90498 91077 84487 86119 89174 89981
91550 92569 84135 84974 90872 93714

initial import of GCC 10.3.0. main changes include:

caveats:
- ABI issue between c++14 and c++17 fixed
- profile mode is removed from libstdc++
- -fno-common is now the default

new features:
- new flags -fallocation-dce, -fprofile-partial-training,
-fprofile-reproducible, -fprofile-prefix-path, and -fanalyzer
- many new compile and link time optimisations
- enhanced drive optimisations
- openacc 2.6 support
- openmp 5.0 features
- new warnings: -Wstring-compare and -Wzero-length-bounds
- extended warnings: -Warray-bounds, -Wformat-overflow,
-Wrestrict, -Wreturn-local-addr, -Wstringop-overflow,
-Warith-conversion, -Wmismatched-tags, and -Wredundant-tags
- some likely C2X features implemented
- more C++20 implemented
- many new arm & intel CPUs known

hundreds of reported bugs are fixed. full list of changes
can be found at:

https://gcc.gnu.org/gcc-10/changes.html

branches: 1.1.1.1.2; 1.1.1.1.4;
import GCC 8.4. it fixes at least these 210 PRs in GCC bugzilla:

90095 93348 89906 89766 86747 87770 89588 89753 88235 89762 89684 89946
89965 90010 90026 90733 90810 90840 90842 90867 91623 92930 93073 93402
93505 93576 93744 93820 93908 85762 86429 86521 87327 87480 87513 87554
87685 87748 88183 88380 88394 88419 88690 88820 89381 89422 89576 89831
89917 90951 92003 92852 93140 80791 89358 89970 90899 89212 89419 92745
93684 93789 88273 91826 92376 84746 89497 89595 89664 89711 89725 90018
90316 90900 91108 91293 91772 92763 93054 93246 90313 92420 93434 93767
88530 89517 91838 79262 84680 85459 85711 85860 86567 87008 87651 87652
88469 89546 89827 90197 93072 93241 81800 89190 85400 91472 91854 92095
92131 92575 93704 60228 61414 65782 89405 89498 89703 89752 90187 90193
90898 91401 91450 91665 92296 92384 92438 92615 92648 92723 92732 92904
93087 93228 93515 93905 82081 92859 89712 89876 92106 82645 78552 81266
85965 89102 90165 90299 90532 91436 92059 93205 93325 93562 90359 91280
91375 92674 92704 93439 92768 80938 83361 90563 92113 92961 87833 89848
89902 89903 92022 93828 78179 79221 82920 84016 87015 88075 89077 89266
90454 90634 91226 92154 92664 92886 93065 92692 92629 80590 91944 92899
92977 93463 89601 88025 91660 91845 90498 91077 84487 86119 89174 89981
91550 92569 84135 84974 90872 93714