tweak zstd behavior in cmake and llvm config for better testing

[ckissane]

Summary

add LLVM_PREFER_STATIC_ZSTD (default TRUE) cmake config flag
(compression test seems to fail for shared zstd on windows, note that zstd multithread is by default disabled in the static build so it may be a hidden variable)
propagate variable zstd_DIR in LLVMConfig.cmake.in
fix llvm-config CMakeLists.txt behavior for absolute libs windows
get zstd lib name

[phosek]

llvm/cmake/modules/LLVMConfig.cmake.in

77–78

I think it should be possible to omit this line altogether, this shouldn't be needed (zlib above is a special case).

llvm/lib/Support/CMakeLists.txt

24

This is unnecessary, you can just omit this line.

[ckissane]

llvm/cmake/modules/LLVMConfig.cmake.in

77–78

unfortunately this is the critical change

[ckissane]

• omit uneeded line

[ckissane]

llvm/cmake/modules/LLVMConfig.cmake.in

77–78

without this:
the builders that set custom zstd_DIR when building clang will build fine
but tests that run then using the llvmconfig vars will fail to find zstd

llvm/lib/Support/CMakeLists.txt

24

omitted

[ckissane]

• add LLVM_PREFER_STATIC_ZSTD (default TRUE)

[ckissane]

• remove nit

llvm/cmake/modules/LLVMConfig.cmake.in

77–78

apparently warning which this fixes can be ignored anyway... so removing for now...

[phosek]

LGTM

llvm/lib/Support/CMakeLists.txt

31–43

I'd prefer a slightly simpler strategy which is to follow what linkers do (and what we also sometimes use elsewhere in the build): try shared first, if it doesn't exist use static plus provide a flag to skip the shared library search.

llvm/CMakeLists.txt

 else()
   option(LLVM_ENABLE_THREADS "Use threads if available." ON)
 endif()
 
 set(LLVM_ENABLE_ZLIB "ON" CACHE STRING "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_ENABLE_ZSTD "ON" CACHE STRING "Use zstd for compression/decompression if available. Can be ON, OFF, or FORCE_ON")
 
+set(LLVM_PREFER_STATIC_ZSTD TRUE CACHE BOOL "Use static version of zstd if available. Can be TRUE, FALSE")
+
 set(LLVM_ENABLE_CURL "OFF" CACHE STRING "Use libcurl for the HTTP client if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_ENABLE_HTTPLIB "OFF" CACHE STRING "Use cpp-httplib HTTP server library if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")
 
 option(LLVM_ENABLE_Z3_SOLVER
   "Enable Support for the Z3 constraint solver in LLVM."

llvm/cmake/modules/LLVMConfig.cmake.in

 
 set(LLVM_ENABLE_ZLIB @LLVM_ENABLE_ZLIB@)
 if(LLVM_ENABLE_ZLIB)
   set(ZLIB_ROOT @ZLIB_ROOT@)
   find_package(ZLIB)
 endif()
 
 set(LLVM_ENABLE_ZSTD @LLVM_ENABLE_ZSTD@)
 if(LLVM_ENABLE_ZSTD)
-  set(zstd_ROOT @zstd_ROOT@)
   find_package(zstd)
 endif()
 
 set(LLVM_ENABLE_LIBXML2 @LLVM_ENABLE_LIBXML2@)
 if(LLVM_ENABLE_LIBXML2)
   find_package(LibXml2)
 endif()
 
 set(LLVM_WITH_Z3 @LLVM_WITH_Z3@)

llvm/lib/Support/CMakeLists.txt

if (HAS_WERROR_GLOBAL_CTORS)
   static std::recursive_mutex TestGlobalCtorDtor2;
   int main() { (void)TestGlobalCtorDtor; (void)TestGlobalCtorDtor2; return 0;}
   " LLVM_HAS_NOGLOBAL_CTOR_MUTEX)
   if (NOT LLVM_HAS_NOGLOBAL_CTOR_MUTEX)
     string(REPLACE "-Werror=global-constructors" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
   endif()
 endif()
 
 if(LLVM_ENABLE_ZLIB)
-  set(imported_libs ZLIB::ZLIB)
+  list(APPEND imported_libs ZLIB::ZLIB)
+endif()
+
+set(zstd_target none)
+
+if(LLVM_ENABLE_ZSTD)
+  if(LLVM_PREFER_STATIC_ZSTD)
+    if(TARGET zstd::libzstd_static)
+      set(zstd_target zstd::libzstd_static)
+    else()
+      set(zstd_target zstd::libzstd_shared)
+    endif()
+  else()
+    if(TARGET zstd::libzstd_shared)
+      set(zstd_target zstd::libzstd_shared)
+    else()
+      set(zstd_target zstd::libzstd_static)
+    endif()
+  endif()
 endif()
 
 if(LLVM_ENABLE_ZSTD)
-  list(APPEND imported_libs zstd::libzstd_shared)
+  list(APPEND imported_libs ${zstd_target})
 endif()
 
 if( MSVC OR MINGW )
   # libuuid required for FOLDERID_Profile usage in lib/Support/Windows/Path.inc.
   # advapi32 required for CryptAcquireContextW in lib/Support/Windows/Path.inc.
   set(system_libs ${system_libs} psapi shell32 ole32 uuid advapi32)
 elseif( CMAKE_HOST_UNIX )
   if( HAVE_LIBRT )
if(LLVM_ENABLE_ZLIB)
   get_library_name(${zlib_library} zlib_library)
   set(llvm_system_libs ${llvm_system_libs} "${zlib_library}")
 endif()
 
 if(LLVM_ENABLE_ZSTD)
   # CMAKE_BUILD_TYPE is only meaningful to single-configuration generators.
   if(CMAKE_BUILD_TYPE)
     string(TOUPPER ${CMAKE_BUILD_TYPE} build_type)
-    get_property(zstd_library TARGET zstd::libzstd_shared PROPERTY LOCATION_${build_type})
+    get_property(zstd_library TARGET ${zstd_target} PROPERTY LOCATION_${build_type})
   endif()
   if(NOT zstd_library)
-    get_property(zstd_library TARGET zstd::libzstd_shared PROPERTY LOCATION)
+    get_property(zstd_library TARGET ${zstd_target} PROPERTY LOCATION)
   endif()
+  get_library_name(${zstd_library} zstd_library)
   set(llvm_system_libs ${llvm_system_libs} "${zstd_library}")
 endif()
 
 if(LLVM_ENABLE_TERMINFO)
   if(NOT terminfo_library)
     get_property(terminfo_library TARGET Terminfo::terminfo PROPERTY LOCATION)
   endif()
   get_library_name(${terminfo_library} terminfo_library)

llvm/tools/llvm-config/CMakeLists.txt

add_llvm_tool(llvm-config
   # want to build an entire native libLLVM.so in addition to the cross one just
   # for the native `llvm-config`!
   DISABLE_LLVM_LINK_LLVM_DYLIB
   )
 
 # Compute the substitution values for various items.
 get_property(SUPPORT_SYSTEM_LIBS TARGET LLVMSupport PROPERTY LLVM_SYSTEM_LIBS)
 get_property(WINDOWSMANIFEST_SYSTEM_LIBS TARGET LLVMWindowsManifest PROPERTY LLVM_SYSTEM_LIBS)
+
 foreach(l ${SUPPORT_SYSTEM_LIBS} ${WINDOWSMANIFEST_SYSTEM_LIBS})
   if(MSVC)
+    if(IS_ABSOLUTE ${l})
+      set(SYSTEM_LIBS ${SYSTEM_LIBS} "${l}")
+    else()
       set(SYSTEM_LIBS ${SYSTEM_LIBS} "${l}.lib")
+    endif()
   else()
     if (l MATCHES "^-")
       # If it's an option, pass it without changes.
       set(SYSTEM_LIBS ${SYSTEM_LIBS} "${l}")
     else()
       # Otherwise assume it's a library name we need to link with.
       if(IS_ABSOLUTE ${l})
         set(SYSTEM_LIBS ${SYSTEM_LIBS} "${l}")
       else()
         set(SYSTEM_LIBS ${SYSTEM_LIBS} "-l${l}")
       endif()
     endif()
   endif()
 endforeach()
+
 string(REPLACE ";" " " SYSTEM_LIBS "${SYSTEM_LIBS}")
 
 # Fetch target specific compile options, e.g. RTTI option
 get_property(COMPILE_FLAGS TARGET llvm-config PROPERTY COMPILE_FLAGS)
 
 # NOTE: We don't want to start extracting any random C/CXX flags that the
 # user may add that could affect the ABI.  We only want to extract flags
 # that have been added by the LLVM build system.