[Driver] Don't use Classic Flang tools for LLVM IR input

LLVM IR input should not be acceptable for Classic Flang tools. This bug was
caused by an incorrect merge conflict resolution when upgrading to LLVM 15.

Author: bryanpkc

clang/lib/Driver/Types.cpp

@@ -175,14 +175,15 @@ bool types::isAcceptedByFlang(ID Id) {
   case TY_PP_F_FreeForm:
   case TY_F_FixedForm:
   case TY_PP_F_FixedForm:
+    return true;
 #else
   case TY_Fortran:
   case TY_PP_Fortran:
-#endif
     return true;
   case TY_LLVM_IR:
   case TY_LLVM_BC:
     return true;
+#endif
   }
 }
 

clang/test/Driver/flang/Inputs/llvm-ir-input.ll

@@ -0,0 +1,7 @@
+! Check that LLVM IR input is passed to clang instead of flang1.
+
+! REQUIRES: classic_flang
+! RUN: %clang --driver-mode=flang -S %S/Inputs/llvm-ir-input.ll -### 2>&1 | FileCheck %s
+
+! CHECK-NOT: flang1
+! CHECK: "{{.*}}clang{{.*}}" "-cc1"