[llvm] [flang-rt] Optimise ShallowCopy and use it in CopyInAssign (PR #140569)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-aarch64-out-of-tree` running on `linaro-flang-aarch64-out-of-tree` while building `flang-rt` at step 12 "build-flang-rt-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/53/builds/16175

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 12 (build-flang-rt-unified-tree) failure: build (failure)
...
2.839 [1/69/51] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/time-intrinsic.cpp.o
2.892 [1/68/52] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/copy.cpp.o
3.113 [1/67/53] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/descriptor.cpp.o
3.206 [1/66/54] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/rrspacing.cpp.o
3.299 [1/65/55] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/connection.cpp.o
3.385 [1/64/56] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/external-unit.cpp.o
3.396 [1/63/57] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/extensions.cpp.o
3.403 [1/62/58] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/descriptor-io.cpp.o
3.416 [1/61/59] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/floor.cpp.o
3.469 [1/60/60] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/assign.cpp.o
FAILED: flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/assign.cpp.o 
/usr/local/bin/c++ -D_DEBUG -D_GLIBCXX_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/include -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/../flang/include -I/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/build_flang-rt/flang-rt -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=gnu++17 -UNDEBUG -fno-lto -fno-exceptions -fno-rtti -funwind-tables -fno-asynchronous-unwind-tables -U_GLIBCXX_ASSERTIONS -U_LIBCPP_ENABLE_ASSERTIONS -MD -MT flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/assign.cpp.o -MF flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/assign.cpp.o.d -o flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/assign.cpp.o -c /home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/runtime/assign.cpp
../llvm-project/flang-rt/lib/runtime/assign.cpp:594:17: error: use of undeclared identifier 'kNoAsyncId'
  594 |   temp.Allocate(kNoAsyncId);
      |                 ^
1 error generated.
3.471 [1/59/61] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/ceil.cpp.o
3.484 [1/58/62] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/set-exponent.cpp.o
3.505 [1/57/63] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/io-error.cpp.o
3.540 [1/56/64] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/cosh.cpp.o
3.552 [1/55/65] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/environment.cpp.o
3.553 [1/54/66] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/asinh.cpp.o
3.554 [1/53/67] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/mod-real.cpp.o
3.562 [1/52/68] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/trunc.cpp.o
3.599 [1/51/69] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/erfc.cpp.o
3.600 [1/50/70] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/stat.cpp.o
3.702 [1/49/71] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/sinh.cpp.o
3.714 [1/48/72] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/round.cpp.o
3.720 [1/47/73] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/tgamma.cpp.o
3.727 [1/46/74] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/fma.cpp.o
3.752 [1/45/75] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/j0.cpp.o
3.757 [1/44/76] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/inquiry.cpp.o
3.761 [1/43/77] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/log.cpp.o
3.770 [1/42/78] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/y1.cpp.o
3.775 [1/41/79] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/log10.cpp.o
3.910 [1/40/80] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/ragged.cpp.o
3.916 [1/39/81] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/random.cpp.o
3.917 [1/38/82] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/misc-intrinsic.cpp.o
3.963 [1/37/83] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/norm2.cpp.o
4.007 [1/36/84] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/exp.cpp.o
4.015 [1/35/85] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/file.cpp.o
4.043 [1/34/86] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/erf.cpp.o
4.087 [1/33/87] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/type-info.cpp.o
4.109 [1/32/88] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/numeric.cpp.o
4.220 [1/31/89] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/derived.cpp.o
4.286 [1/30/90] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/remainder.cpp.o
4.310 [1/29/91] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/array-constructor.cpp.o
4.468 [1/28/92] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/random.cpp.o
4.478 [1/27/93] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/tcwg-buildbot/worker/flang-aarch64-out-of-tree/llvm-project/flang-rt/lib/quadmath/j1.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/140569