[driver] Add -emit-flang-llvm option

-emit-flang-llvm instructs flang to stop after flang2 and dump the LLVM IR.

Can be useful for debugging and also would be a useful option for testing flang
output more accurately.

Signed-off-by: Richard Barton <[email protected]>

Author: RichBarton-Arm

clang/include/clang/Driver/Options.td

@@ -1545,6 +1545,10 @@ def d_Joined : Joined<["-"], "d">, Group<d_Group>;
 def emit_ast : Flag<["-"], "emit-ast">,
   Visibility<[ClangOption, CLOption, DXCOption]>,
   HelpText<"Emit Clang AST files for source inputs">;
+#ifdef ENABLE_CLASSIC_FLANG
+def emit_flang_llvm : Flag<["-"], "emit-flang-llvm">,
+  HelpText<"Emit Flang LLVM files for source inputs">;
+#endif
 def emit_llvm : Flag<["-"], "emit-llvm">,
   Visibility<[ClangOption, CC1Option, FC1Option, FlangOption]>,
   Group<Action_Group>,

clang/lib/Driver/Driver.cpp

@@ -423,6 +423,9 @@ phases::ID Driver::getFinalPhase(const DerivedArgList &DAL,
              (PhaseArg = DAL.getLastArg(options::OPT_print_supported_cpus)) ||
              (PhaseArg = DAL.getLastArg(options::OPT_print_enabled_extensions)) ||
              (PhaseArg = DAL.getLastArg(options::OPT_module_file_info)) ||
+#ifdef ENABLE_CLASSIC_FLANG
+             (PhaseArg = DAL.getLastArg(options::OPT_emit_flang_llvm)) ||
+#endif
              (PhaseArg = DAL.getLastArg(options::OPT_verify_pch)) ||
              (PhaseArg = DAL.getLastArg(options::OPT_rewrite_objc)) ||
              (PhaseArg = DAL.getLastArg(options::OPT_rewrite_legacy_objc)) ||

clang/lib/Driver/ToolChains/ClassicFlang.cpp

@@ -87,6 +87,13 @@ void ClassicFlang::ConstructJob(Compilation &C, const JobAction &JA,
     llvm::sys::path::replace_extension(Stem, "");
   }
 
+#ifdef ENABLE_CLASSIC_FLANG
+  if (Args.hasArg(options::OPT_emit_flang_llvm)) {
+    // -emit-flang-llvm only supports asm output so claim -S to prevent warning
+    Args.ClaimAllArgs(options::OPT_S);
+  }
+#endif
+
   // Add input file name to the compilation line
   UpperCmdArgs.push_back(Input.getBaseInput());