在Win10上编译LLVM

代码仓库：https://github.com/llvm/llvm-project

LLVM_TARGETS_TO_BUILD

-DLLVM_TARGETS_TO_BUILD="X86;PowerPC". The full list, as of March 2023, is: AArch64;AMDGPU;ARM;AVR;BPF;Hexagon;Lanai;LoongArch;Mips;MSP430;NVPTX;PowerPC;RISCV;Sparc;SystemZ;VE;WebAssembly;X86;XCore

-DLLVM_TARGETS_TO_BUILD=host // 将编译当前机器的架构的二进制 on an x86_64 machine will include the X86 target.

To enable all of them, use: -DLLVM_TARGETS_TO_BUILD=all

LLVM_ENABLE_PROJECTS

full list：bolt;clang;clang-tools-extra;compiler-rt;cross-project-tests;libc;libclc;lld;lldb;mlir;openmp;polly;pstl

To enable all of them, use: LLVM_ENABLE_RUNTIMES=all

LLVM_ENABLE_RUNTIMES

full list：libc;libunwind;libcxxabi;pstl;libcxx;compiler-rt;openmp;llvm-libgcc;offload

To enable all of them, use: LLVM_ENABLE_RUNTIMES=all

CMAKE_BUILD_TYPE

This configures the optimization level for make or ninja builds.

Possible values:

Build Type	Optimizations	Debug Info	Assertions	Best suited for
Release	For Speed	No	No	Users of LLVM and Clang
Debug	None	Yes	Yes	Developers of LLVM
RelWithDebInfo	For Speed	Yes	No	Users that also need Debug
MinSizeRel	For Size	No	No	When disk space matters

更多详见：https://llvm.org/docs/CMake.html

在windows上编译llvm

build.windows.clang.bat内容如下：

setlocal enableextensions
set "ROOT_DIR=%~dp0"
set "PROJECT_DIR=%ROOT_DIR%\llvm"
set "path=%~dp0tools\bin;C:\Python36-32;%path%"
set "CLANG_BUILD_DIR=%ROOT_DIR%\build\windows"
set "CLANG_INSTALL_DIR=%ROOT_DIR%\install\windows"
mkdir %CLANG_BUILD_DIR%
set "LLVM_ENABLE_PROJECTS=clang;lld"
set "LLVM_TARGETS_TO_BUILD=X86;WebAssembly"
set "CMAKE_BUILD_TYPE=RelWithDebInfo"
set "LIBFFI_DIR=%ROOT_DIR%\..\cppvm\source\cppvm-libffi\install\windows\x86_64"
set "CMAKE_PARAM=-DLLVM_ENABLE_PROJECTS="%LLVM_ENABLE_PROJECTS%" -DLLVM_INCLUDE_EXAMPLES=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_INCLUDE_DOCS=OFF -DLLVM_ENABLE_LLD=On -DLLVM_EXPORT_SYMBOLS_FOR_PLUGINS=On -DLLVM_TARGETS_TO_BUILD="%LLVM_TARGETS_TO_BUILD%" -DLLVM_ENABLE_FFI=ON -DFFI_INCLUDE_DIR=%LIBFFI_DIR%\include -DLLVM_ENABLE_DUMP=On -DFFI_LIBRARY_DIR=%LIBFFI_DIR%\lib -DLLVM_OPTIMIZED_TABLEGEN=ON -DCMAKE_BUILD_TYPE=%CMAKE_BUILD_TYPE% -DCMAKE_INSTALL_PREFIX=%CLANG_INSTALL_DIR% %PROJECT_DIR%"
cmake.exe -S %PROJECT_DIR% -B %CLANG_BUILD_DIR% -G "Visual Studio 16 2019"  -A x64 -Thost=x64 -DLLVM_COMPILER_JOBS=14 -DCMAKE_C_FLAGS="/bigobj" -DCMAKE_CXX_FLAGS="/bigobj" %CMAKE_PARAM% 
cmake --build %CLANG_BUILD_DIR% --config "%CMAKE_BUILD_TYPE%" --target INSTALL -- /m
pause

一些报错：

LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_prep_cif referenced in function "bool __cdecl ffiInvoke(void (__cdecl*)(void),class llvm::Function *,class llvm::ArrayRef
<struct llvm::GenericValue>,class llvm::DataLayout const &,struct llvm::GenericValue &)" (?ffiInvoke@@YA_NP6AXXZPEAVFunction@llvm@@V?$ArrayRef@UGenericValue@llvm@@@2@AEBVDataLayout@2@AEAUGenericValue@2@@Z) [G:\svn\llvm
-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_call referenced in function "bool __cdecl ffiInvoke(void (__cdecl*)(void),class llvm::Function *,class llvm::ArrayRef<str
uct llvm::GenericValue>,class llvm::DataLayout const &,struct llvm::GenericValue &)" (?ffiInvoke@@YA_NP6AXXZPEAVFunction@llvm@@V?$ArrayRef@UGenericValue@llvm@@@2@AEBVDataLayout@2@AEAUGenericValue@2@@Z) [G:\svn\llvm-pro
ject\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_void referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_typ 
e@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint8 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_ty 
pe@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint16 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint32 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint64 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_float referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_ty 
pe@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_double referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_pointer referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_ 
type@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]
G:\svn\llvm-project\build\windows\RelWithDebInfo\bin\lli.exe : fatal error LNK1120: 10 unresolved externals [G:\svn\llvm-project\build\windows\tools\lli\lli.vcxproj]

LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_prep_cif referenced in function "bool __cdecl ffiInvoke(void (__cdecl*)(void),class llvm::Function *,class llvm::ArrayRef
<struct llvm::GenericValue>,class llvm::DataLayout const &,struct llvm::GenericValue &)" (?ffiInvoke@@YA_NP6AXXZPEAVFunction@llvm@@V?$ArrayRef@UGenericValue@llvm@@@2@AEBVDataLayout@2@AEAUGenericValue@2@@Z) [G:\svn\llvm 
-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_call referenced in function "bool __cdecl ffiInvoke(void (__cdecl*)(void),class llvm::Function *,class llvm::ArrayRef<str
uct llvm::GenericValue>,class llvm::DataLayout const &,struct llvm::GenericValue &)" (?ffiInvoke@@YA_NP6AXXZPEAVFunction@llvm@@V?$ArrayRef@UGenericValue@llvm@@@2@AEBVDataLayout@2@AEAUGenericValue@2@@Z) [G:\svn\llvm-pro
ject\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_void referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_typ 
e@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint8 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_ty 
pe@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint16 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint32 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_sint64 referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_float referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_ty 
pe@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_double referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_t 
ype@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
LLVMInterpreter.lib(ExternalFunctions.obj) : error LNK2019: unresolved external symbol __imp_ffi_type_pointer referenced in function "struct _ffi_type * __cdecl ffiTypeFor(class llvm::Type *)" (?ffiTypeFor@@YAPEAU_ffi_ 
type@@PEAVType@llvm@@@Z) [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]
G:\svn\llvm-project\build\windows\RelWithDebInfo\bin\LLVM-C.dll : fatal error LNK1120: 10 unresolved externals [G:\svn\llvm-project\build\windows\tools\llvm-shlib\LLVM-C.vcxproj]

原因是：使用了静态库版的ffi.lib，而在G:\svn\llvm-project\llvm\lib\ExecutionEngine\Interpreter\ExternalFunctions.cpp中引用ffi.h，会将FFI_API定义为__declspec(dllimport)，导致名字修饰都会带上__imp_前缀，从而找不到这些符号

/* Need minimal decorations for DLLs to work on Windows.  GCC has
   autoimport and autoexport.  Always mark externally visible symbols
   as dllimport for MSVC clients, even if it means an extra indirection
   when using the static version of the library.
   Besides, as a workaround, they can define FFI_BUILDING if they
   *know* they are going to link with the static library.  */
#if defined _MSC_VER
# if defined FFI_BUILDING_DLL /* Building libffi.DLL with msvcc.sh */
#  define FFI_API __declspec(dllexport)
# elif !defined FFI_BUILDING  /* Importing libffi.DLL */
#  define FFI_API __declspec(dllimport)
# else                        /* Building/linking static library */
#  define FFI_API
# endif
#else
# define FFI_API
#endif