[llvm] [gSYM] Add support merged functions in gSYM format (PR #101604)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-debian-cpp20` running on `clang-debian-cpp20` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/108/builds/2132

Here is the relevant piece of the build log for the reference:
```
Step 5 (build-unified-tree) failure: build (failure)
...
      |               ^
      |                , this
1 warning generated.
19.436 [3812/17/1948] Building CXX object lib/DebugInfo/DWARF/CMakeFiles/LLVMDebugInfoDWARF.dir/DWARFVerifier.cpp.o
23.059 [3811/17/1949] Building AMDGPUGenCallingConv.inc...
23.104 [3810/17/1950] Building CXX object lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/Header.cpp.o
23.161 [3809/17/1951] Building CXX object lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/FileWriter.cpp.o
23.899 [3808/17/1952] Building CXX object lib/Object/CMakeFiles/LLVMObject.dir/IRSymtab.cpp.o
25.745 [3807/17/1953] Building AMDGPUGenMCPseudoLowering.inc...
25.874 [3806/17/1954] Building CXX object lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/DwarfTransformer.cpp.o
FAILED: lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/DwarfTransformer.cpp.o 
ccache /usr/bin/clang++-17 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/lib/DebugInfo/GSYM -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/lib/DebugInfo/GSYM -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/include -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include -Wno-deprecated-enum-enum-conversion -Wno-deprecated-declarations -Wno-deprecated-anon-enum-enum-conversion -Wno-ambiguous-reversed-operator -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 -pedantic -Wno-long-long -Wc++98-compat-extra-semi -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=c++20  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/DwarfTransformer.cpp.o -MF lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/DwarfTransformer.cpp.o.d -o lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/DwarfTransformer.cpp.o -c /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/lib/DebugInfo/GSYM/DwarfTransformer.cpp
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/lib/DebugInfo/GSYM/DwarfTransformer.cpp:12:
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/DebugInfo/DIContext.h:17:
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/ADT/SmallVector.h:25:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/functional:64:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/vector:66:
/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/stl_vector.h:1932:46: error: arithmetic on a pointer to an incomplete type 'llvm::gsym::FunctionInfo'
 1932 |         if (size_type __n = this->_M_impl._M_finish - __pos)
      |                             ~~~~~~~~~~~~~~~~~~~~~~~ ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/stl_vector.h:1603:9: note: in instantiation of member function 'std::vector<llvm::gsym::FunctionInfo>::_M_erase_at_end' requested here
 1603 |       { _M_erase_at_end(this->_M_impl._M_start); }
      |         ^
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/DebugInfo/GSYM/MergedFunctionsInfo.h:27:34: note: in instantiation of member function 'std::vector<llvm::gsym::FunctionInfo>::clear' requested here
   27 |   void clear() { MergedFunctions.clear(); }
      |                                  ^
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/DebugInfo/GSYM/DwarfTransformer.h:23:8: note: forward declaration of 'llvm::gsym::FunctionInfo'
   23 | struct FunctionInfo;
      |        ^
1 error generated.
26.277 [3806/16/1955] Building CXX object lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/FunctionInfo.cpp.o
FAILED: lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/FunctionInfo.cpp.o 
ccache /usr/bin/clang++-17 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/lib/DebugInfo/GSYM -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/lib/DebugInfo/GSYM -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/include -I/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include -Wno-deprecated-enum-enum-conversion -Wno-deprecated-declarations -Wno-deprecated-anon-enum-enum-conversion -Wno-ambiguous-reversed-operator -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 -pedantic -Wno-long-long -Wc++98-compat-extra-semi -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=c++20  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/FunctionInfo.cpp.o -MF lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/FunctionInfo.cpp.o.d -o lib/DebugInfo/GSYM/CMakeFiles/LLVMDebugInfoGSYM.dir/FunctionInfo.cpp.o -c /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/lib/DebugInfo/GSYM/FunctionInfo.cpp
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/lib/DebugInfo/GSYM/FunctionInfo.cpp:9:
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/DebugInfo/GSYM/FunctionInfo.h:12:
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/ADT/SmallString.h:17:
In file included from /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/ADT/SmallVector.h:25:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/functional:64:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/vector:66:
/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/stl_vector.h:1932:46: error: arithmetic on a pointer to an incomplete type 'llvm::gsym::FunctionInfo'
 1932 |         if (size_type __n = this->_M_impl._M_finish - __pos)
      |                             ~~~~~~~~~~~~~~~~~~~~~~~ ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/stl_vector.h:1603:9: note: in instantiation of member function 'std::vector<llvm::gsym::FunctionInfo>::_M_erase_at_end' requested here
 1603 |       { _M_erase_at_end(this->_M_impl._M_start); }
      |         ^
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/DebugInfo/GSYM/MergedFunctionsInfo.h:27:34: note: in instantiation of member function 'std::vector<llvm::gsym::FunctionInfo>::clear' requested here
   27 |   void clear() { MergedFunctions.clear(); }
      |                                  ^
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/DebugInfo/GSYM/LineTable.h:20:8: note: forward declaration of 'llvm::gsym::FunctionInfo'

```

https://github.com/llvm/llvm-project/pull/101604