[MLIR] Add support for libMLIR.so

Putting this up mainly for discussion on
how this should be done. I am interested in MLIR from
the Julia side and we currently have a strong preference
to dynamically linking against the LLVM shared library,
and would like to have a MLIR shared library.

This patch adds a new cmake function add_mlir_library()
which accumulates a list of targets to be compiled into
libMLIR.so.  Note that not all libraries make sense to
be compiled into libMLIR.so.  In particular, we want
to avoid libraries which primarily exist to support
certain tools (such as mlir-opt and mlir-cpu-runner).

Note that the resulting libMLIR.so depends on LLVM, but
does not contain any LLVM components.  As a result, it
is necessary to link with libLLVM.so to avoid linkage
errors. So, libMLIR.so requires LLVM_BUILD_LLVM_DYLIB=on

FYI, Currently it appears that LLVM_LINK_LLVM_DYLIB is broken
because mlir-tblgen is linked against libLLVM.so and
and independent LLVM components

(updated by Stephen Neuendorffer)

Differential Revision: https://reviews.llvm.org/D73130

1 files changed, 29 insertions, 2 deletions

diff --git a/mlir/cmake/modules/AddMLIR.cmake b/mlir/cmake/modules/AddMLIR.cmake
index d8944532c6ff..cd7860ca2fe3 100644
--- a/mlir/cmake/modules/AddMLIR.cmake
+++ b/mlir/cmake/modules/AddMLIR.cmake
@@ -49,14 +49,41 @@ function(add_mlir_dialect dialect dialect_doc_filename)
   add_dependencies(mlir-doc ${dialect_doc_filename}DocGen)
 endfunction()
 
+# Declare a library which can be compiled in libMLIR.so
+macro(add_mlir_library name)
+  cmake_parse_arguments(ARG
+    "SHARED;INSTALL_WITH_TOOLCHAIN"
+    ""
+    "ADDITIONAL_HEADERS"
+    ${ARGN})
+  set(srcs)
+  if(ARG_SHARED)
+    set(LIBTYPE SHARED)
+  else()
+    # llvm_add_library ignores BUILD_SHARED_LIBS if STATIC is explicitly set,
+    # so we need to handle it here.
+    if(BUILD_SHARED_LIBS)
+      set(LIBTYPE SHARED)
+    else()
+      set(LIBTYPE STATIC)
+    endif()
+    if(NOT XCODE)
+      # The Xcode generator doesn't handle object libraries correctly.
+      list(APPEND LIBTYPE OBJECT)
+    endif()
+    set_property(GLOBAL APPEND PROPERTY MLIR_ALL_LIBS ${name})
+  endif()
+  add_llvm_library(${name} ${LIBTYPE} ${ARG_UNPARSED_ARGUMENTS} ${srcs})
+endmacro(add_mlir_library)
+
 # Declare the library associated with a dialect.
 function(add_mlir_dialect_library name)
   set_property(GLOBAL APPEND PROPERTY MLIR_DIALECT_LIBS ${name})
-  add_llvm_library(${ARGV})
+  add_mlir_library(${ARGV})
 endfunction(add_mlir_dialect_library)
 
 # Declare the library associated with a conversion.
 function(add_mlir_conversion_library name)
   set_property(GLOBAL APPEND PROPERTY MLIR_CONVERSION_LIBS ${name})
-  add_llvm_library(${ARGV})
+  add_mlir_library(${ARGV})
 endfunction(add_mlir_conversion_library)