TableGen.cmake: Use DEPFILE for Ninja Generator with CMake>=3.7.

[chapuni]

Summary

CMake emits build targets as relative paths (from build.ninja) but Ninja doesn't identify absolute path (in *.d) as relative path (in build.ninja).
So, let file names, in the command line, relative from ${CMAKE_BINARY_DIR}, where build.ninja is.

Note that tblgen is executed on ${CMAKE_BINARY_DIR} as working directory.

Not tested on msvc/ninja yet, due to avoiding reinstallation of newer CMake.

[chapuni]

I have confirmed it works on ninja.exe with CMake-3.9.

include/llvm/IR/Intrinsics.gen.tmp:
  C:/path/to/llvm-project/llvm/include\llvm/CodeGen/ValueTypes.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsAArch64.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsAMDGPU.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsARM.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsBPF.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsHexagon.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsMips.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsNVVM.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsPowerPC.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsSystemZ.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsWebAssembly.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsX86.td
  C:/path/to/llvm-project/llvm/include\llvm/IR/IntrinsicsXCore.td

Each dependent contains '\\' but it's not a problem since each of them is not a target but a dependent source. Ninja.exe is correctly stat-ing them as I expect.

@beanz, I will commit it within a few days.

[beanz]

This looks great! Thanks for doing this.

llvm/trunk/cmake/modules/TableGen.cmake

 # LLVM_TARGET_DEFINITIONS must contain the name of the .td file to process.
 # Extra parameters for `tblgen' may come after `ofn' parameter.
 # Adds the name of the generated file to TABLEGEN_OUTPUT.
 
 include(LLVMExternalProjectUtils)
 
 if(LLVM_MAIN_INCLUDE_DIR)
   set(LLVM_TABLEGEN_FLAGS -I ${LLVM_MAIN_INCLUDE_DIR})
 endif()
 
 function(tablegen project ofn)
   # Validate calling context.
   if(NOT ${project}_TABLEGEN_EXE)
     message(FATAL_ERROR "${project}_TABLEGEN_EXE not set")
   endif()
 
+  # Use depfile instead of globbing arbitrary *.td(s)
+  # DEPFILE is available for Ninja Generator with CMake>=3.7.
+  if(CMAKE_GENERATOR STREQUAL "Ninja" AND NOT CMAKE_VERSION VERSION_LESS 3.7)
+    # Make output path relative to build.ninja, assuming located on
+    # ${CMAKE_BINARY_DIR}.
+    # 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})
+    set(additional_cmdline
+      -o ${ofn_rel}.tmp
+      -d ${ofn_rel}.d
+      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
+      DEPFILE ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.d
+      )
+    set(local_tds)
+    set(global_tds)
+  else()
     file(GLOB local_tds "*.td")
     file(GLOB_RECURSE global_tds "${LLVM_MAIN_INCLUDE_DIR}/llvm/*.td")
+    set(additional_cmdline
+      -o ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.tmp
+      )
+  endif()
 
   if (IS_ABSOLUTE ${LLVM_TARGET_DEFINITIONS})
     set(LLVM_TARGET_DEFINITIONS_ABSOLUTE ${LLVM_TARGET_DEFINITIONS})
   else()
     set(LLVM_TARGET_DEFINITIONS_ABSOLUTE
       ${CMAKE_CURRENT_SOURCE_DIR}/${LLVM_TARGET_DEFINITIONS})
   endif()
   if (LLVM_ENABLE_DAGISEL_COV)
function(tablegen project ofn)
   # dependency twice in the result file when
   # ("${${project}_TABLEGEN_TARGET}" STREQUAL "${${project}_TABLEGEN_EXE}")
   # but lets us having smaller and cleaner code here.
   add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.tmp
     # Generate tablegen output in a temporary file.
     COMMAND ${${project}_TABLEGEN_EXE} ${ARGN} -I ${CMAKE_CURRENT_SOURCE_DIR}
     ${LLVM_TABLEGEN_FLAGS}
     ${LLVM_TARGET_DEFINITIONS_ABSOLUTE}
-    -o ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.tmp
+    ${additional_cmdline}
     # 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 ${${project}_TABLEGEN_TARGET} ${${project}_TABLEGEN_EXE}
       ${local_tds} ${global_tds}
     ${LLVM_TARGET_DEFINITIONS_ABSOLUTE}
     COMMENT "Building ${ofn}..."
     )