[llvm-branch-commits] [runtimes] Allow building against an installed LLVM tree (PR #86209)

[Louis Dionne via llvm-branch-commits]

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@@ -218,6 +218,22 @@ foreach(entry ${runtimes})
 endforeach()
 
 if(LLVM_INCLUDE_TESTS)
+  # Add lit if needed before adding any runtimes since their CMake tests
+  # configuration might depend on lit being present.
+  if (NOT HAVE_LLVM_LIT)
+    # If built by manually invoking cmake on this directory, we don't have
+    # llvm-lit. If invoked via llvm/runtimes, the toplevel llvm cmake
+    # invocation already generated the llvm-lit script.
+    set(LLVM_LIT_OUTPUT_DIR ${CMAKE_CURRENT_BINARY_DIR}/bin)
+    add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/llvm-lit
+                     ${CMAKE_CURRENT_BINARY_DIR}/llvm-lit)
+    # Ensure that the testsuites use the local lit rather than
+    # LLVM_INSTALL_DIR/bin/llvm-lit (which may not exist if LLVM_BINARY_DIR
+    # points at an installed LLVM tree rather than a build tree.
+    get_llvm_lit_path(_base_dir _file_name)
+    set(LLVM_EXTERNAL_LIT "${_base_dir}/${_file_name}" CACHE STRING "Command used to spawn lit" FORCE)
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ldionne wrote:

I don't understand. We *must* have `lit` available since we are in the `runtimes/CMakeLists.txt`? I actually don't understand why the `if (NOT HAVE_LLVM_LIT)` branch is ever taken. Can you shed some light on this?

https://github.com/llvm/llvm-project/pull/86209