[llvm] r367896 - NFC. Documenting Native tablegen dependency

[Chris Bieneman via llvm-commits]

Author: cbieneman
Date: Mon Aug  5 11:00:55 2019
New Revision: 367896

URL: http://llvm.org/viewvc/llvm-project?rev=367896&view=rev
Log:
NFC. Documenting Native tablegen dependency

Adding documentation explaining why this dependency is required and should not be removed again.

Modified:
    llvm/trunk/cmake/modules/TableGen.cmake

Modified: llvm/trunk/cmake/modules/TableGen.cmake
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/cmake/modules/TableGen.cmake?rev=367896&r1=367895&r2=367896&view=diff
==============================================================================
--- llvm/trunk/cmake/modules/TableGen.cmake (original)
+++ llvm/trunk/cmake/modules/TableGen.cmake Mon Aug  5 11:00:55 2019
@@ -125,6 +125,9 @@ macro(add_tablegen target project)
 
   if(LLVM_USE_HOST_TOOLS)
     if( ${${project}_TABLEGEN} STREQUAL "${target}" )
+      # The NATIVE tablegen executable *must* depend on the current target one
+      # otherwise the native one won't get rebuilt when the tablgen sources
+      # change, and we end up with incorrect builds.
       build_native_tool(${target} ${project}_TABLEGEN_EXE DEPENDS ${target})
       set(${project}_TABLEGEN_EXE ${${project}_TABLEGEN_EXE} PARENT_SCOPE)