[flang][driver] Delete `f18` (i.e. the old Flang driver)

This patch removes `f18`, a.k.a. the old driver. It is being replaced
with the new driver, `flang-new`, which has reached feature parity with
`f18` a while ago. This was discussed in [1] and also in [2].

With this change, `FLANG_BUILD_NEW_DRIVER` is no longer needed and is
also deleted. This means that we are making the dependency on Clang permanent
(i.e. it cannot be disabled with a CMake flag).

LIT set-up is updated accordingly. All references to `f18` or `f18.cpp`
are either updated or removed.

The `F18_FC` variable from the `flang` bash script is replaced with
`FLANG_FC`. The former is still supported for backwards compatibility.

[1] https://lists.llvm.org/pipermail/flang-dev/2021-June/000742.html
[2] https://reviews.llvm.org/D103177

Differential Revision: https://reviews.llvm.org/D105811

1 files changed, 28 insertions, 39 deletions

diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
index adf3dc819dc9..fc85f4451316 100644
--- a/flang/CMakeLists.txt
+++ b/flang/CMakeLists.txt
@@ -26,11 +26,6 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(Flang)
   set(FLANG_STANDALONE_BUILD ON)
 
-  # For in-tree builds, this variable is inherited from
-  # llvm-project/llvm/CMakeLists.txt. For out-of-tree builds, we need a
-  # separate definition.
-  option(FLANG_BUILD_NEW_DRIVER "Build the flang compiler driver" ON)
-
   set(FLANG_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
   if (NOT MSVC_IDE)
     set(LLVM_ENABLE_ASSERTIONS ${ENABLE_ASSERTIONS}
@@ -46,24 +41,22 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   get_filename_component(LLVM_DIR_ABSOLUTE ${LLVM_DIR} REALPATH)
   list(APPEND CMAKE_MODULE_PATH ${LLVM_DIR_ABSOLUTE})
 
-  if(FLANG_BUILD_NEW_DRIVER)
-    # Users might specify a path to CLANG_DIR that's:
-    #   * a full path, or
-    #   * a path relative to the path of this script.
-    # Append the absolute path to CLANG_DIR so that find_package works in both
-    # cases.
-    get_filename_component(
-      CLANG_DIR_ABSOLUTE
-      ${CLANG_DIR}
-      REALPATH
-      ${CMAKE_CURRENT_SOURCE_DIR})
-    list(APPEND CMAKE_MODULE_PATH ${CLANG_DIR_ABSOLUTE})
-
-    # TODO: Remove when libclangDriver is lifted out of Clang
-    find_package(Clang REQUIRED PATHS "${CLANG_DIR_ABSOLUTE}" NO_DEFAULT_PATH)
-    if (NOT Clang_FOUND)
-      message(FATAL_ERROR "Failed to find Clang")
-    endif()
+  # Users might specify a path to CLANG_DIR that's:
+  #   * a full path, or
+  #   * a path relative to the path of this script.
+  # Append the absolute path to CLANG_DIR so that find_package works in both
+  # cases.
+  get_filename_component(
+    CLANG_DIR_ABSOLUTE
+    ${CLANG_DIR}
+    REALPATH
+    ${CMAKE_CURRENT_SOURCE_DIR})
+  list(APPEND CMAKE_MODULE_PATH ${CLANG_DIR_ABSOLUTE})
+
+  # TODO: Remove when libclangDriver is lifted out of Clang
+  find_package(Clang REQUIRED PATHS "${CLANG_DIR_ABSOLUTE}" NO_DEFAULT_PATH)
+  if (NOT Clang_FOUND)
+    message(FATAL_ERROR "Failed to find Clang")
   endif()
 
   # If LLVM links to zlib we need the imported targets so we can too.
@@ -80,9 +73,7 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   include(HandleLLVMOptions)
   include(VersionFromVCS)
 
-  if(FLANG_BUILD_NEW_DRIVER)
-    include(AddClang)
-  endif()
+  include(AddClang)
 
   include(TableGen)
   find_package(MLIR REQUIRED CONFIG)
@@ -206,20 +197,18 @@ endif()
 set(FLANG_INTRINSIC_MODULES_DIR ${CMAKE_BINARY_DIR}/include/flang)
 set(FLANG_INCLUDE_DIR ${FLANG_BINARY_DIR}/include)
 
-if(FLANG_BUILD_NEW_DRIVER)
-    # TODO: Remove when libclangDriver is lifted out of Clang
-    if(FLANG_STANDALONE_BUILD)
-      set(CLANG_INCLUDE_DIR ${CLANG_INCLUDE_DIRS} )
-      # No need to specify TableGen output dir as that's embedded in CLANG_DIR
-    else()
-      set(CLANG_INCLUDE_DIR ${LLVM_MAIN_SRC_DIR}/../clang/include )
-      # Specify TableGen output dir for things like DiagnosticCommonKinds.inc,
-      # DiagnosticDriverKinds.inc (required for reporting diagnostics)
-      set(CLANG_TABLEGEN_OUTPUT_DIR ${CMAKE_BINARY_DIR}/tools/clang/include)
-      include_directories(SYSTEM ${CLANG_TABLEGEN_OUTPUT_DIR})
-    endif()
-    include_directories(SYSTEM ${CLANG_INCLUDE_DIR})
+# TODO: Remove when libclangDriver is lifted out of Clang
+if(FLANG_STANDALONE_BUILD)
+  set(CLANG_INCLUDE_DIR ${CLANG_INCLUDE_DIRS} )
+  # No need to specify TableGen output dir as that's embedded in CLANG_DIR
+else()
+  set(CLANG_INCLUDE_DIR ${LLVM_MAIN_SRC_DIR}/../clang/include )
+  # Specify TableGen output dir for things like DiagnosticCommonKinds.inc,
+  # DiagnosticDriverKinds.inc (required for reporting diagnostics)
+  set(CLANG_TABLEGEN_OUTPUT_DIR ${CMAKE_BINARY_DIR}/tools/clang/include)
+  include_directories(SYSTEM ${CLANG_TABLEGEN_OUTPUT_DIR})
 endif()
+include_directories(SYSTEM ${CLANG_INCLUDE_DIR})
 
 # tco tool and FIR lib output directories
 if(FLANG_STANDALONE_BUILD)