[libc] [llvm] Refactor WIDE_READ to allow finer control over high-performance function selection (PR #165613)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `libc-x86_64-debian-dbg-asan` running on `libc-x86_64-debian` while building `libc,utils` at step 4 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/147/builds/34206

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

```
Step 4 (annotate) failure: 'python ../llvm-zorg/zorg/buildbot/builders/annotated/libc-linux.py ...' (failure)
...
[7/20] Linking CXX executable libc/fuzzing/stdlib/libc.fuzzing.stdlib.atof_differential_fuzz
[8/20] Linking CXX executable libc/fuzzing/stdio/libc.fuzzing.stdio.printf_parser_fuzz
[9/20] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.remainderf.__internal__.dir/remainderf.cpp.o
[10/20] Linking CXX executable libc/fuzzing/string/libc.fuzzing.string.strcmp_fuzz
[11/20] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.remainder.__internal__.dir/remainder.cpp.o
[12/20] Linking CXX executable libc/fuzzing/math/libc.fuzzing.math.nextafter_differential_fuzz
[13/20] Linking CXX executable libc/fuzzing/string/libc.fuzzing.string.strlen_fuzz
[14/20] Linking CXX executable libc/fuzzing/stdlib/libc.fuzzing.stdlib.strtointeger_differential_fuzz_cleaner
[15/20] Building CXX object libc/src/math/generic/CMakeFiles/libc.src.math.generic.remainderl.__internal__.dir/remainderl.cpp.o
[16/20] Building CXX object libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_fuzz.dir/hashtable_fuzz.cpp.o
FAILED: libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_fuzz.dir/hashtable_fuzz.cpp.o 
/usr/bin/clang++ -DLIBC_NAMESPACE=__llvm_libc_20_0_0_git -D_DEBUG -I/home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc -isystem /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/build/libc/include -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 -Wno-comment -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fno-omit-frame-pointer -fsanitize=address -fdiagnostics-color -fsanitize=fuzzer -g -std=gnu++17 -MD -MT libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_fuzz.dir/hashtable_fuzz.cpp.o -MF libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_fuzz.dir/hashtable_fuzz.cpp.o.d -o libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_fuzz.dir/hashtable_fuzz.cpp.o -c /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/fuzzing/__support/hashtable_fuzz.cpp
In file included from /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/fuzzing/__support/hashtable_fuzz.cpp:15:
In file included from /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/src/__support/HashTable/table.h:23:
In file included from /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/src/string/string_utils.h:23:
/home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/src/string/string_length.h:202:5: error: use of undeclared identifier 'LIBC_COPT_FIND_FIRST_CHARACTER_IMPL'
    LIBC_COPT_FIND_FIRST_CHARACTER_IMPL::find_first_character;
    ^
1 error generated.
[17/20] Building CXX object libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_opt_fuzz.dir/hashtable_fuzz.cpp.o
FAILED: libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_opt_fuzz.dir/hashtable_fuzz.cpp.o 
/usr/bin/clang++ -DLIBC_NAMESPACE=__llvm_libc_20_0_0_git -D_DEBUG -I/home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc -isystem /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/build/libc/include -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 -Wno-comment -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fno-omit-frame-pointer -fsanitize=address -fdiagnostics-color -fsanitize=fuzzer -g -D__LIBC_EXPLICIT_SIMD_OPT -std=gnu++17 -MD -MT libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_opt_fuzz.dir/hashtable_fuzz.cpp.o -MF libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_opt_fuzz.dir/hashtable_fuzz.cpp.o.d -o libc/fuzzing/__support/CMakeFiles/libc.fuzzing.__support.hashtable_opt_fuzz.dir/hashtable_fuzz.cpp.o -c /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/fuzzing/__support/hashtable_fuzz.cpp
In file included from /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/fuzzing/__support/hashtable_fuzz.cpp:15:
In file included from /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/src/__support/HashTable/table.h:23:
In file included from /home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/src/string/string_utils.h:23:
/home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-project/libc/src/string/string_length.h:202:5: error: use of undeclared identifier 'LIBC_COPT_FIND_FIRST_CHARACTER_IMPL'
    LIBC_COPT_FIND_FIRST_CHARACTER_IMPL::find_first_character;
    ^
1 error generated.
[18/20] Linking CXX executable libc/fuzzing/math/libc.fuzzing.math.math_differential_fuzz
ninja: build stopped: subcommand failed.
['ninja', 'libc-fuzzer'] exited with return code 1.
The build step threw an exception...
Traceback (most recent call last):
  File "/home/llvm-libc-buildbot/home/sivachandra/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/build/../llvm-zorg/zorg/buildbot/builders/annotated/libc-linux.py", line 181, in step
    yield
  File "/home/llvm-libc-buildbot/home/sivachandra/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/build/../llvm-zorg/zorg/buildbot/builders/annotated/libc-linux.py", line 172, in main
    run_command(['ninja', 'libc-fuzzer'])
  File "/home/llvm-libc-buildbot/home/sivachandra/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/build/../llvm-zorg/zorg/buildbot/builders/annotated/libc-linux.py", line 196, in run_command
    util.report_run_cmd(cmd, cwd=directory)
  File "/home/llvm-libc-buildbot/home/sivachandra/libc-x86_64-debian/libc-x86_64-debian-dbg-asan/llvm-zorg/zorg/buildbot/builders/annotated/util.py", line 49, in report_run_cmd
    subprocess.check_call(cmd, shell=shell, *args, **kwargs)
  File "/usr/lib/python3.11/subprocess.py", line 413, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['ninja', 'libc-fuzzer']' returned non-zero exit status 1.
@@@STEP_FAILURE@@@

```

</details>

https://github.com/llvm/llvm-project/pull/165613