[CMake] Do not set CMP0116 explicitly to old (#90385)

CMP0116 was originally set to old to get rid of warnings. However, this
behavior is now set to new by default with the minimum CMake version
that LLVM requires so does not produce any warnings, and setting it
explicitly to old does produce a warning in newer CMake versions. Due to
these reasons, remove this check for now.

Splitting off from removing the CMP0114 check just in case something
breaks.

Partially fixes #83727.

cmake/Modules/CMakePolicy.cmake

@@ -1,11 +1,5 @@
 # CMake policy settings shared between LLVM projects
 
-# CMP0116: Ninja generators transform `DEPFILE`s from `add_custom_command()`
-# New in CMake 3.20. https://cmake.org/cmake/help/latest/policy/CMP0116.html
-if(POLICY CMP0116)
-  cmake_policy(SET CMP0116 OLD)
-endif()
-
 # MSVC debug information format flags are selected via
 # CMAKE_MSVC_DEBUG_INFORMATION_FORMAT, instead of
 # embedding flags in e.g. CMAKE_CXX_FLAGS_RELEASE.

llvm/cmake/modules/TableGen.cmake

@@ -21,20 +21,21 @@ function(tablegen project ofn)
     message(FATAL_ERROR "${project}_TABLEGEN_EXE not set")
   endif()
 
-  # Use depfile instead of globbing arbitrary *.td(s) for Ninja.
-  if(CMAKE_GENERATOR MATCHES "Ninja")
-    # Make output path relative to build.ninja, assuming located on
-    # ${CMAKE_BINARY_DIR}.
+  # Use depfile instead of globbing arbitrary *.td(s) for Ninja. We force
+  # CMake versions older than v3.30 on Windows to use the fallback behavior
+  # due to a depfile parsing bug on Windows paths in versions prior to 3.30.
+  # https://gitlab.kitware.com/cmake/cmake/-/issues/25943
+  cmake_policy(GET CMP0116 cmp0116_state)
+  if(CMAKE_GENERATOR MATCHES "Ninja" AND cmp0116_state STREQUAL NEW
+     AND NOT (CMAKE_HOST_WIN32 AND CMAKE_VERSION VERSION_LESS 3.30))
     # CMake emits build targets as relative paths but Ninja doesn't identify
-    # absolute path (in *.d) as relative path (in build.ninja)
-    # Note that tblgen is executed on ${CMAKE_BINARY_DIR} as working directory.
-    file(RELATIVE_PATH ofn_rel
-      ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR}/${ofn})
+    # absolute path (in *.d) as relative path (in build.ninja). Post CMP0116,
+    # CMake handles this discrepancy for us, otherwise we use the fallback
+    # logic.
     set(additional_cmdline
-      -o ${ofn_rel}
-      -d ${ofn_rel}.d
-      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
-      DEPFILE ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.d
+      -o ${ofn}
+      -d ${ofn}.d
+      DEPFILE ${ofn}.d
       )
     set(local_tds)
     set(global_tds)

mlir/cmake/modules/AddMLIR.cmake

@@ -42,20 +42,21 @@ function(_pdll_tablegen project ofn)
     message(FATAL_ERROR "${project}_TABLEGEN_EXE not set")
   endif()
 
-  # Use depfile instead of globbing arbitrary *.td(s) for Ninja.
-  if(CMAKE_GENERATOR MATCHES "Ninja")
-    # Make output path relative to build.ninja, assuming located on
-    # ${CMAKE_BINARY_DIR}.
+  # Use depfile instead of globbing arbitrary *.td(s) for Ninja. We force
+  # CMake versions older than v3.30 on Windows to use the fallback behavior
+  # due to a depfile parsing bug on Windows paths in versions prior to 3.30.
+  # https://gitlab.kitware.com/cmake/cmake/-/issues/25943
+  cmake_policy(GET CMP0116 cmp0116_state)
+  if(CMAKE_GENERATOR MATCHES "Ninja" AND cmp0116_state STREQUAL NEW
+     AND NOT (CMAKE_HOST_WIN32 AND CMAKE_VERSION VERSION_LESS 3.30))
     # CMake emits build targets as relative paths but Ninja doesn't identify
-    # absolute path (in *.d) as relative path (in build.ninja)
-    # Note that tblgen is executed on ${CMAKE_BINARY_DIR} as working directory.
-    file(RELATIVE_PATH ofn_rel
-      ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR}/${ofn})
+    # absolute path (in *.d) as relative path (in build.ninja). Post CMP0116,
+    # CMake handles this discrepancy for us. Otherwise, we use the fallback
+    # logic.
     set(additional_cmdline
-      -o ${ofn_rel}
-      -d ${ofn_rel}.d
-      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
-      DEPFILE ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.d
+      -o ${ofn}
+      -d ${ofn}.d
+      DEPFILE ${ofn}.d
       )
     set(local_tds)
     set(global_tds)