[lit] Force site configs to be run before source-tree configs

This patch simplifies LLVM's lit infrastructure by enforcing an ordering
that a site config is always run before a source-tree config.

A significant amount of the complexity from lit config files arises from
the fact that inside of a source-tree config file, we don't yet know if
the site config has been run.  However it is *always* required to run
a site config first, because it passes various variables down through
CMake that the main config depends on.  As a result, every config
file has to do a bunch of magic to try to reverse-engineer the location
of the site config file if they detect (heuristically) that the site
config file has not yet been run.

This patch solves the problem by emitting a mapping from source tree
config file to binary tree site config file in llvm-lit.py. Then, during
discovery when we find a config file, we check to see if we have a
target mapping for it, and if so we use that instead.

This mechanism is generic enough that it does not affect external users
of lit. They will just not have a config mapping defined, and everything
will work as normal.

On the other hand, for us it allows us to make many simplifications:

* We are guaranteed that a site config will be executed first
* Inside of a main config, we no longer have to assume that attributes
  might not be present and use getattr everywhere.
* We no longer have to pass parameters such as --param llvm_site_config=<path>
  on the command line.
* It is future-proof, meaning you don't have to edit llvm-lit.in to add
  support for new projects.
* All of the duplicated logic of trying various fallback mechanisms of
  finding a site config from the main config are now gone.

One potentially noteworthy thing that was required to implement this
change is that whereas the ninja check targets previously used the first
method to spawn lit, they now use the second. In particular, you can no
longer run lit.py against the source tree while specifying the various
`foo_site_config=<path>` parameters.  Instead, you need to run
llvm-lit.py.

Differential Revision: https://reviews.llvm.org/D37756

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313270 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 5 deletions

diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
index 66abb2486d9..b30d002aa20 100644
--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -1174,6 +1174,13 @@ function(configure_lit_site_cfg input output)
   endif()
 
   configure_file(${input} ${output} @ONLY)
+  get_filename_component(INPUT_DIR ${input} DIRECTORY)
+  if (EXISTS "${INPUT_DIR}/lit.cfg")
+    set(PYTHON_STATEMENT "map_config('${INPUT_DIR}/lit.cfg', '${output}')")
+    get_property(LLVM_LIT_CONFIG_MAP GLOBAL PROPERTY LLVM_LIT_CONFIG_MAP)
+    set(LLVM_LIT_CONFIG_MAP "${LLVM_LIT_CONFIG_MAP}\n${PYTHON_STATEMENT}")
+    set_property(GLOBAL PROPERTY LLVM_LIT_CONFIG_MAP ${LLVM_LIT_CONFIG_MAP})
+  endif()
 endfunction()
 
 # A raw function to create a lit target. This is used to implement the testuite
@@ -1185,12 +1192,16 @@ function(add_lit_target target comment)
   if (NOT CMAKE_CFG_INTDIR STREQUAL ".")
     list(APPEND LIT_ARGS --param build_mode=${CMAKE_CFG_INTDIR})
   endif ()
-  if (EXISTS ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
-    set (LIT_COMMAND "${PYTHON_EXECUTABLE};${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py"
-         CACHE STRING "Command used to spawn llvm-lit")
-  else()
-    find_program(LIT_COMMAND NAMES llvm-lit lit.py lit)
+
+  if (WIN32 AND NOT CYGWIN)
+    # llvm-lit needs suffix.py for multiprocess to find a main module.
+    set(suffix .py)
   endif ()
+  set(llvm_lit_path ${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-lit${suffix})
+
+  set (LIT_COMMAND "${PYTHON_EXECUTABLE};${llvm_lit_path}"
+        CACHE STRING "Command used to spawn llvm-lit" FORCE)
+
   list(APPEND LIT_COMMAND ${LIT_ARGS})
   foreach(param ${ARG_PARAMS})
     list(APPEND LIT_COMMAND --param ${param})