Treat polly as "in tree" if LLVM_EXTERNAL_POLLY_SOURCE_DIR is provided

[etherzhhb]

Summary

Treat polly as "in tree" if LLVM_EXTERNAL_POLLY_SOURCE_DIR is provided, since in this case polly is also built as if it is in tree.

[Meinersbur]

Did you successfully build Polly out-of-tree with this. with an without LLVM_POLLY_LINK_INTO_TOOLS? I think I remember there were other places where it assumed that polly is in ${LLVM_ROOT}/tools/polly.

[etherzhhb]

The only "tools/polly" I saw is :
./CMakeLists.txt:if (EXISTS ${LLVM_MAIN_SRC_DIR}/tools/polly/CMakeLists.txt)

I am setting LLVM_POLLY_LINK_INTO_TOOLS and running check-all

[etherzhhb]

I tried the combination of {LLVM_POLLY_LINK_INTO_TOOLS On/Of} x {cmake from scratch/cmake on existing cmakecach}, and it passed check-all (which includes check-polly).

[Meinersbur]

Well, the other occurrences might have already been removed. Since this works: LGTM

CMakeLists.txt

 option(LLVM_USE_SPLIT_DWARF
   "Use -gsplit-dwarf when compiling llvm." OFF)
 
 option(LLVM_POLLY_LINK_INTO_TOOLS "Statically link Polly into tools (if available)" ON)
 option(LLVM_POLLY_BUILD "Build LLVM with Polly" ON)
 
 if (EXISTS ${LLVM_MAIN_SRC_DIR}/tools/polly/CMakeLists.txt)
   set(POLLY_IN_TREE TRUE)
+elseif(LLVM_EXTERNAL_POLLY_SOURCE_DIR)
+  set(POLLY_IN_TREE TRUE)
 else()
   set(POLLY_IN_TREE FALSE)
 endif()
 
 if (LLVM_POLLY_BUILD AND POLLY_IN_TREE)
   set(WITH_POLLY ON)
 else()
   set(WITH_POLLY OFF)