4a5bc791f3
When LLVM_NATIVE_TOOL_DIR was introduced ind3da9067d1/ D131052, it consisted of refactoring a couple cases of manual logic for tools in clang-tools-extra/clang-tidy, clang-tools-extra/pseudo/include and mlir/tools/mlir-linalg-ods-gen. The former two had the same consistent behaviour while the latter was slightly different, so the refactoring would end up slightly adjusting one or the other. The difference was that the clang-tools-extra tools respected the external variable for setting the tool name, regardless of the LLVM_USE_HOST_TOOLS variable, while mlir-linalg-ods-gen tool only checked its external variable if LLVM_USE_HOST_TOOLS was set. LLVM_USE_HOST_TOOLS is supposed to be enabled automatically whenever cross compiling, so this shouldn't have been an issue. In https://github.com/llvm/llvm-project/issues/60784, it seems like some users do cross compile LLVM, without CMake knowing about it (without CMAKE_CROSSCOMPILING being set). In these cases, their build broke, as the variables for pointing to external host tools no longer were being respected. The fact that CMAKE_CROSSCOMPILING wasn't set stems from a non-obvious behaviour of CMake; CMAKE_CROSSCOMPILING isn't supposed to be set by the user (and if it was, it gets overridden), but one has to set CMAKE_SYSTEM_NAME to indicate that one is cross compiling, even if the target OS is the same as the current host. Skip the checks for LLVM_USE_HOST_TOOLS and always respect the variables for pointing to external tools (both the old tool specific variables, and the new LLVM_NATIVE_TOOL_DIR), if they're set. This makes the logic within setup_host_tool more exactly match the logic for the clang-tools-extra tools from before the refactoring ind3da9067d1. This makes the behaviour consistent with that of the tablegen executables, which also respect the externally set variables regardless of LLVM_USE_HOST_TOOLS. This fixes https://github.com/llvm/llvm-project/issues/60784. Differential Revision: https://reviews.llvm.org/D146666
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