[llvm][ItaniumDemangle] Use __LDBL_MANT_DIG__ for configuring demangling of long doubles

[Michael137]

Syncing in the changes from #134976 using the cp-to-llvm.sh script.

[Michael137]

libc++ failures look unrelated:

llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/extents/assert.conversion.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/extents/assert.ctor_from_array.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/extents/assert.ctor_from_integral.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/extents/assert.ctor_from_span.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/extents/assert.obs.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_left/assert.conversion.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_left/assert.ctor.extents.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_left/assert.ctor.layout_right.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_left/assert.ctor.layout_stride.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_right/assert.conversion.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_right/assert.ctor.extents.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_right/assert.ctor.layout_left.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_right/assert.ctor.layout_stride.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_stride/assert.ctor.extents_array.pass.cpp
llvm-libc++-shared-cfg-in.libcxx/containers/views/mdspan/layout_stride/assert.ctor.extents_span.pass.cpp

# .---command stderr------------
# | /var/lib/buildkite-agent/builds/linux-56-59b8f5d88-bt7k7-1/llvm-project/github-pull-requests/libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.conversion.pass.cpp:30:29: error: declaration of 'dynamic_extent' must be imported from module 'std.span.fwd' before it is required
# |    30 |   constexpr size_t D = std::dynamic_extent;
# |       |                             ^
# | /var/lib/buildkite-agent/builds/linux-56-59b8f5d88-bt7k7-1/llvm-project/github-pull-requests/build/runtimes/runtimes-bins/libcxx/test-suite-install/include/c++/v1/__fwd/span.h:28:25: note: declaration here is not visible
# |    28 | inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
# |       |                         ^
# | 1 error generated.
# `-----------------------------
# error: command failed with exit status: 1

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-gcc-ubuntu running on sie-linux-worker3 while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/174/builds/16292

Here is the relevant piece of the build log for the reference

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'AddressSanitizer-x86_64-linux :: TestCases/asan_lsan_deadlock.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/./bin/clang  --driver-mode=g++ -fsanitize=address -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -gline-tables-only  -m64  -O0 /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/compiler-rt/test/asan/TestCases/asan_lsan_deadlock.cpp -o /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxConfig/TestCases/Output/asan_lsan_deadlock.cpp.tmp # RUN: at line 4
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/./bin/clang --driver-mode=g++ -fsanitize=address -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -gline-tables-only -m64 -O0 /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/compiler-rt/test/asan/TestCases/asan_lsan_deadlock.cpp -o /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxConfig/TestCases/Output/asan_lsan_deadlock.cpp.tmp
env ASAN_OPTIONS=detect_leaks=1 not  /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxConfig/TestCases/Output/asan_lsan_deadlock.cpp.tmp 2>&1 | FileCheck /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/compiler-rt/test/asan/TestCases/asan_lsan_deadlock.cpp # RUN: at line 5
+ env ASAN_OPTIONS=detect_leaks=1 not /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxConfig/TestCases/Output/asan_lsan_deadlock.cpp.tmp
+ FileCheck /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/compiler-rt/test/asan/TestCases/asan_lsan_deadlock.cpp
�[1m/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/compiler-rt/test/asan/TestCases/asan_lsan_deadlock.cpp:58:12: �[0m�[0;1;31merror: �[0m�[1mCHECK: expected string not found in input
�[0m // CHECK: SUMMARY: AddressSanitizer: stack-buffer-overflow
�[0;1;32m           ^
�[0m�[1m<stdin>:1:1: �[0m�[0;1;30mnote: �[0m�[1mscanning from here
�[0m=================================================================
�[0;1;32m^
�[0m�[1m<stdin>:2:10: �[0m�[0;1;30mnote: �[0m�[1mpossible intended match here
�[0m==3620435==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7b70856de034 at pc 0x564651007260 bp 0x7b70838fdce0 sp 0x7b70838fdcd8
�[0;1;32m         ^
�[0m
Input file: <stdin>
Check file: /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/compiler-rt/test/asan/TestCases/asan_lsan_deadlock.cpp

-dump-input=help explains the following input dump.

Input was:
<<<<<<
�[1m�[0m�[0;1;30m            1: �[0m�[1m�[0;1;46m================================================================= �[0m
�[0;1;31mcheck:58'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
�[0m�[0;1;30m            2: �[0m�[1m�[0;1;46m==3620435==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7b70856de034 at pc 0x564651007260 bp 0x7b70838fdce0 sp 0x7b70838fdcd8 �[0m
�[0;1;31mcheck:58'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
�[0m�[0;1;35mcheck:58'1              ?                                                                                                                                    possible intended match
�[0m�[0;1;30m            3: �[0m�[1m�[0;1;46mWRITE of size 4 at 0x7b70856de034 thread T2 �[0m
�[0;1;31mcheck:58'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
�[0m�[0;1;30m            4: �[0m�[1m�[0;1;46mTimeout! Deadlock detected. �[0m
�[0;1;31mcheck:58'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
�[0m>>>>>>

--

********************

[mstorsjo]

Just for the record; these changes here didn't stem from #134976, but from #130573 - the file hasn't been synced after that change.

[mstorsjo]

Thanks for taking care of this!