Warnings while building clang & lld for WebAssembly

[anutosh491]

1. I see quite some cmake warnings

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:642 (add_library):
  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  /Users/anutosh491/work/llvm-project/clang/cmake/modules/AddClang.cmake:109 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/tools/clang-shlib/CMakeLists.txt:44 (add_clang_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:642 (add_library):
  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  /Users/anutosh491/work/llvm-project/clang/cmake/modules/AddClang.cmake:109 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/tools/libclang/CMakeLists.txt:138 (add_clang_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/examples/LLVMPrintFunctionNames/CMakeLists.txt:12 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/examples/PrintFunctionNames/CMakeLists.txt:12 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/examples/AnnotateFunctions/CMakeLists.txt:1 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/examples/Attribute/CMakeLists.txt:1 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/examples/CallSuperAttribute/CMakeLists.txt:1 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  /Users/anutosh491/work/llvm-project/clang/examples/PluginsOrder/CMakeLists.txt:1 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:639 (add_library):
  ADD_LIBRARY called with MODULE option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:940 (llvm_add_library)
  tools/bugpoint-passes/CMakeLists.txt:17 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at cmake/modules/AddLLVM.cmake:642 (add_library):
  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:942 (llvm_add_library)
  tools/remarks-shlib/CMakeLists.txt:16 (add_llvm_library)
This warning is for project developers.  Use -Wno-dev to suppress it.

2. And then i see these ones through the source code. Can't say if they are seen in our builds too

/Users/anutosh491/work/llvm-project/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:6924:67: warning: comparison of integers of different signs: 'typename iterator_traits<user_iterator_impl<User>>::difference_type' (aka 'long') and 'unsigned int' [-Wsign-compare]
 6924 |               if (std::distance(LI->user_begin(), LI->user_end()) !=
      |                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
 6925 |                       LI->getNumUses())
      |                       ~~~~~~~~~~~~~~~~
[ 79%] Building CXX object lib/Transforms/Instrumentation/CMakeFiles/LLVMInstrumentation.dir/PGOInstrumentation.cpp.o
/Users/anutosh491/work/llvm-project/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:9754:43: warning: comparison of integers of different signs: 'typename iterator_traits<Value *const *>::difference_type' (aka 'long') and 'unsigned int' [-Wsign-compare]
 9754 |               count(Slice, Slice.front()) ==
      |               ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
 9755 |                   (isa<UndefValue>(Slice.front()) ? VF - 1 : 1)) {

[anutosh491]

I think seeing warnings like these make sense.

  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.

I think wasm prefers static library builds in comparison to shared ones !
Hence if we have an option, maybe we should pass static after checking for the target platform.

[anutosh491]

Fixing the warnings occuring out of SLPVectorizer.cpp through a PR soon.
Please let me know what is expected on the cmake side too .