[llvm][cmake] Fix add_subdirectory build in multi-config

[sebastian-ne]

Summary

Using CMAKE_CFG_INTDIR in paths that are used in configure_file,
resulted in a folder that is literally called '${CONFIGURATION}'
for the multi-config ninja build.

I think this is a regression from a while ago. Fix this by replacing
CMAKE_CFG_INTDIR with '.'. We can only create one of the
LLVMConfig.cmake files as the consuming CMake project can only import a
single file. This creates LLVMConfig.cmake and others in the place where
they were previously and where they are for a single-config build.

[sebastian-ne]

ping for review

[jsilvanus]

I still get the ${CONFIGURATION} directory even with this patch, running:

cmake -G"Ninja Multi-Config" -DLLVM_ENABLE_PROJECTS="clang;lld;clang-tools-extra" -DLLVM_TARGETS_TO_BUILD="X86;AMDGPU" ../llvm

[sebastian-ne]

I still get the ${CONFIGURATION} directory even with this patch

This is caused by set( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${LLVM_TOOLS_BINARY_DIR} ) in llvm/CMakeLists.txt:L963.
If I understand it correctly, set_output_directory() sets the individual output directories for targets to sensible directories and the generic CMAKE_RUNTIME_OUTPUT_DIRECTORY isn’t used.

I see this patch as a band-aid. Long-term, we want to get rid of CMAKE_CFG_INTDIR and use generator expressions.

[jsilvanus]

Ok, fine with me.

For completeness, the patch avoids the creation of mentioned dir under some but not all circumstances?

[sebastian-ne]

For completeness, the patch avoids the creation of mentioned dir under some but not all circumstances?

Yes, I didn’t see a ${CONFIGURATION} dir in a build where llvm was added with add_subdirectory.
More importantly, LLVMConfig.cmake and others are not created inside that directory.

[nhat-nguyen]

@sebastian-ne I'm currently experiencing an mlir build issue after this change with the following error:

CMake Error at D:/a/_work/1/b/llvm/lib/cmake/mlir/MLIRConfig.cmake:6 (find_package):
  Could not find a package configuration file provided by "LLVM" (requested
  version 16.0.0) with any of the following names:

    LLVMConfig.cmake
    llvm-config.cmake

  Add the installation prefix of "LLVM" to CMAKE_PREFIX_PATH or set
  "LLVM_DIR" to a directory containing one of the above files.  If "LLVM"
  provides a separate development package or SDK, be sure it has been
  installed.
Call Stack (most recent call first):
  MLIR.cmake:13 (find_package)
  CMakeLists.txt:84 (include)

I believe this is due to llvm_cmake_builddir not being set correctly for mlir when CMAKE_CFG_INTDIR is $(Configuration). Here's my attempt at fixing the issue -- I'm not particularly well-versed in cmake, so I would very much appreciate if you could take a quick look:

From a601cd27cfdeea2d5a7e37091fe73728c78c9ee3 Mon Sep 17 00:00:00 2001
From: Nhat Nguyen <[e-mail]>
Date: Tue, 10 Jan 2023 14:07:00 -0500
Subject: [PATCH] Attempted fix

---
 llvm-project/mlir/cmake/modules/CMakeLists.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm-project/mlir/cmake/modules/CMakeLists.txt b/llvm-project/mlir/cmake/modules/CMakeLists.txt
index 3f15c2d5cd0b..9d4d51c7a6e1 100644
--- a/llvm-project/mlir/cmake/modules/CMakeLists.txt
+++ b/llvm-project/mlir/cmake/modules/CMakeLists.txt
@@ -15,7 +15,8 @@ set(mlir_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/mlir
 set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
   "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
 # CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
-set(llvm_cmake_builddir "${LLVM_LIBRARY_DIR}/cmake/llvm")
+string(REPLACE "${CMAKE_CFG_INTDIR}" "." llvm_cmake_builddir  "${LLVM_LIBRARY_DIR}")
+set(llvm_cmake_builddir "${llvm_cmake_builddir}/cmake/llvm")
 
 get_property(MLIR_EXPORTS GLOBAL PROPERTY MLIR_EXPORTS)
 export(TARGETS ${MLIR_EXPORTS} FILE ${mlir_cmake_builddir}/MLIRTargets.cmake)
-- 
2.34.0.windows.1

Thank you!

[sebastian-ne]

That looks good to me. I guess the same change applies to the duplicated code in flang, polly, lld and clang.

llvm/cmake/modules/AddLLVM.cmake

function(process_llvm_pass_plugins)
   if(ARG_GEN_CONFIG)
 
       ## Part 1: Extension header to be included whenever we need extension
       #  processing.
       if(NOT DEFINED LLVM_INSTALL_PACKAGE_DIR)
           message(FATAL_ERROR "LLVM_INSTALL_PACKAGE_DIR must be defined and writable. GEN_CONFIG should only be passe when building LLVM proper.")
       endif()
       # LLVM_INSTALL_PACKAGE_DIR might be absolute, so don't reuse below.
-      set(llvm_cmake_builddir "${LLVM_LIBRARY_DIR}/cmake/llvm")
+      string(REPLACE "${CMAKE_CFG_INTDIR}" "." llvm_cmake_builddir  "${LLVM_LIBRARY_DIR}")
+      set(llvm_cmake_builddir "${llvm_cmake_builddir}/cmake/llvm")
       file(WRITE
           "${llvm_cmake_builddir}/LLVMConfigExtensions.cmake"
           "set(LLVM_STATIC_EXTENSIONS ${LLVM_STATIC_EXTENSIONS})")
       install(FILES
           ${llvm_cmake_builddir}/LLVMConfigExtensions.cmake
           DESTINATION ${LLVM_INSTALL_PACKAGE_DIR}
           COMPONENT cmake-exports)
 

llvm/cmake/modules/CMakeLists.txt

 include(ExtendPath)
 include(LLVMDistributionSupport)
 include(FindPrefixFromConfig)
 
 # CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
-set(llvm_cmake_builddir "${LLVM_LIBRARY_DIR}/cmake/llvm")
+string(REPLACE "${CMAKE_CFG_INTDIR}" "." llvm_cmake_builddir  "${LLVM_LIBRARY_DIR}")
+set(llvm_cmake_builddir "${llvm_cmake_builddir}/cmake/llvm")
 
 # First for users who use an installed LLVM, create the LLVMExports.cmake file.
 set(LLVM_EXPORTS_FILE ${llvm_cmake_builddir}/LLVMExports.cmake)
 get_property(LLVM_EXPORTS GLOBAL PROPERTY LLVM_EXPORTS)
 export(TARGETS ${LLVM_EXPORTS} FILE ${LLVM_EXPORTS_FILE})
 
 # Then for users who want to link against the LLVM build tree, provide the
 # normal targets and the build tree only targets.