[llvm] 8e22227 - Revert "[CMake][TableGen] Fix Ninja depslog error with implicit outputs on Ninja <1.10" (#182695)

[via llvm-commits]

Author: Rahul Joshi
Date: 2026-02-21T19:52:21Z
New Revision: 8e2222795bcc70bfdf8d7506c19ca8cee59be548

URL: https://github.com/llvm/llvm-project/commit/8e2222795bcc70bfdf8d7506c19ca8cee59be548
DIFF: https://github.com/llvm/llvm-project/commit/8e2222795bcc70bfdf8d7506c19ca8cee59be548.diff

LOG: Revert "[CMake][TableGen] Fix Ninja depslog error with implicit outputs on Ninja <1.10" (#182695)

Reverts llvm/llvm-project#179842

This seems to break some dependency tracking, as I no longer see .inc
files being regenerated when I update a TableGen .cpp file. Reverting
for now per the discussion on the PR.

Added: 
    

Modified: 
    llvm/cmake/modules/TableGen.cmake

Removed: 
    


################################################################################
diff  --git a/llvm/cmake/modules/TableGen.cmake b/llvm/cmake/modules/TableGen.cmake
index 1bac44c70d2c8..84c03cd6432ed 100644
--- a/llvm/cmake/modules/TableGen.cmake
+++ b/llvm/cmake/modules/TableGen.cmake
@@ -24,14 +24,6 @@ function(tablegen project ofn)
   # Filter out any empty include items.
   list(REMOVE_ITEM tblgen_includes "")
 
-  # Check for multi-output tablegen invocations BEFORE deciding on depfile mode.
-  # Ninja's depslog cannot handle multiple outputs with depfile, so we must use
-  # fallback mode (globbing) for these cases.
-  set(has_extra_outputs FALSE)
-  if("-gen-register-info" IN_LIST ARGN)
-    set(has_extra_outputs TRUE)
-  endif()
-
   # 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.
@@ -40,28 +32,10 @@ function(tablegen project ofn)
   # behavior as v3.22 and earlier fail to parse some depfiles that get
   # generated, and this behavior was fixed in CMake commit
   # e04a352cca523eba2ac0d60063a3799f5bb1c69e.
-  # CRITICAL: Ninja <1.10 has a depslog limitation: it cannot handle depfile
-  # mode when CMake generates implicit outputs (absolute path aliases for IDE
-  # support). For multi-output rules OR when using Ninja <1.10, we MUST use
-  # fallback mode (glob .td files) to avoid "multiple outputs aren't supported
-  # by depslog" errors.
   cmake_policy(GET CMP0116 cmp0116_state)
-  
-  # Check Ninja version to avoid depslog errors with implicit outputs
-  set(ninja_version_supports_depfile TRUE)
-  if(CMAKE_GENERATOR MATCHES "Ninja")
-    execute_process(COMMAND ${CMAKE_MAKE_PROGRAM} --version
-                    OUTPUT_VARIABLE ninja_version
-                    OUTPUT_STRIP_TRAILING_WHITESPACE)
-    if(ninja_version VERSION_LESS "1.10")
-      set(ninja_version_supports_depfile FALSE)
-    endif()
-  endif()
   if(CMAKE_GENERATOR MATCHES "Ninja" AND cmp0116_state STREQUAL NEW
      AND NOT (CMAKE_HOST_WIN32 AND CMAKE_VERSION VERSION_LESS 3.30)
-     AND NOT (CMAKE_VERSION VERSION_LESS 3.23)
-     AND NOT has_extra_outputs
-     AND ninja_version_supports_depfile)
+     AND NOT (CMAKE_VERSION VERSION_LESS 3.23))
     # CMake emits build targets as relative paths but Ninja doesn't identify
     # absolute path (in *.d) as relative path (in build.ninja). Post CMP0116,
     # CMake handles this discrepancy for us, otherwise we use the fallback
@@ -154,7 +128,7 @@ function(tablegen project ofn)
   # ("${${project}_TABLEGEN_TARGET}" STREQUAL "${${project}_TABLEGEN_EXE}")
   # but lets us having smaller and cleaner code here.
   set(tablegen_exe ${${project}_TABLEGEN_EXE})
-  set(tablegen_target ${${project}_TABLEGEN_TARGET})
+  set(tablegen_depends ${${project}_TABLEGEN_TARGET} ${tablegen_exe})
 
   if(LLVM_PARALLEL_TABLEGEN_JOBS)
     set(LLVM_TABLEGEN_JOB_POOL JOB_POOL tablegen_job_pool)
@@ -162,20 +136,6 @@ function(tablegen project ofn)
     set(LLVM_TABLEGEN_JOB_POOL "")
   endif()
 
-  # For Ninja with multiple outputs, we cannot add the target to DEPENDS due to
-  # depslog limitations. Instead, rely on the implicit tool dependency from COMMAND
-  # and the globbed .td files for proper dependency tracking.
-  # For single outputs or non-Ninja generators, include the target in DEPENDS.
-  set(tablegen_target_dep)
-  if(NOT EXTRA_OUTPUTS)
-    # Single output: safe to add explicit target dependency
-    set(tablegen_target_dep ${tablegen_target})
-  elseif(NOT CMAKE_GENERATOR MATCHES "Ninja")
-    # Multiple outputs but not Ninja: Ninja's depslog is not a constraint
-    set(tablegen_target_dep ${tablegen_target})
-  endif()
-  # Multiple outputs + Ninja: Don't add target dependency; rely on COMMAND implicit tracking
-
   add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${ofn} ${EXTRA_OUTPUTS}
     COMMAND ${tablegen_exe} ${ARG_UNPARSED_ARGUMENTS}
     ${tblgen_includes}
@@ -186,7 +146,7 @@ function(tablegen project ofn)
     # The file in LLVM_TARGET_DEFINITIONS may be not in the current
     # directory and local_tds may not contain it, so we must
     # explicitly list it here:
-    DEPENDS ${ARG_DEPENDS} ${tablegen_target_dep}
+    DEPENDS ${ARG_DEPENDS} ${tablegen_depends}
       ${global_tds}
     ${LLVM_TARGET_DEFINITIONS_ABSOLUTE}
     ${LLVM_TARGET_DEPENDS}