[clang] allow -fthinlto-index= without -x ir

[inglorion]

Summary

Previously, passing -fthinlto-index= to clang required that bitcode
files be explicitly marked by -x ir. This change makes us detect files
with object file extensions as bitcode files when -fthinlto-index= is
present, so that explicitly marking them is no longer necessary.
Explicitly specifying -x ir is still accepted and continues to be part
of the test case to ensure we continue to support it.

[inglorion]

This was suggested on D64458.

If we take this change, D64458 can be simplified to just accepting -fthinlto-index= as a CoreOption without needing any further changes to Driver.cpp.

I also changed the error message in this change to reflect the fact that we no longer require -x ir; we just require the input to be a bitcode file.

[rnk]

lgtm

[MaskRay]

clang/lib/Driver/Driver.cpp

2123

-fthinlto-index=

[tejohnson]

LGTM with the comment fix from @MaskRay

[inglorion]

Fix typo pointed out by MaskRay (thanks!)

clang/include/clang/Basic/DiagnosticDriverKinds.td

 def err_drv_config_file_not_found : Error<
   "configuration file '%0' cannot be found">;
 def note_drv_config_file_searched_in : Note<
   "was searched for in the directory: %0">;
 def err_drv_cannot_read_config_file : Error<
   "cannot read configuration file '%0'">;
 def err_drv_nested_config_file: Error<
   "option '--config' is not allowed inside configuration file">;
+def err_drv_arg_requires_bitcode_input: Error<
+  "option '%0' requires input to be LLVM bitcode">;
 
 def err_target_unsupported_arch
   : Error<"the target architecture '%0' is not supported by the target '%1'">;
 def err_cpu_unsupported_isa
   : Error<"CPU '%0' does not support '%1' execution mode">;
 def err_arch_unsupported_isa
   : Error<"Architecture '%0' does not support '%1' execution mode">;
 

clang/lib/Driver/Driver.cpp

if (A->getOption().getKind() == Option::InputClass) {
           if (CCCIsCXX()) {
             types::ID OldTy = Ty;
             Ty = types::lookupCXXTypeForCType(Ty);
 
             if (Ty != OldTy)
               Diag(clang::diag::warn_drv_treating_input_as_cxx)
                   << getTypeName(OldTy) << getTypeName(Ty);
           }
+
+          // If running with -thinlto-index=, extensions that normally identify
+          // native object files actually identify LLVM bitcode files.
+          if (Args.hasArgNoClaim(options::OPT_fthinlto_index_EQ) &&
+              Ty == types::TY_Object)
+            Ty = types::TY_LLVM_BC;
         }
 
         // -ObjC and -ObjC++ override the default language, but only for "source
         // files". We just treat everything that isn't a linker input as a
         // source file.
         //
         // FIXME: Clean this up if we move the phase sequence into the type.
         if (Ty != types::TY_Object) {

clang/lib/Driver/ToolChains/Clang.cpp

if (D.isUsingLTO() && !isDeviceOffloadAction) {
       if (!(RawTriple.isOSDarwin() || RawTriple.isPS4()) ||
           D.getLTOMode() == LTOK_Full)
         CmdArgs.push_back("-flto-unit");
     }
   }
 
   if (const Arg *A = Args.getLastArg(options::OPT_fthinlto_index_EQ)) {
     if (!types::isLLVMIR(Input.getType()))
-      D.Diag(diag::err_drv_argument_only_allowed_with) << A->getAsString(Args)
-                                                       << "-x ir";
+      D.Diag(diag::err_drv_arg_requires_bitcode_input) << A->getAsString(Args);
     Args.AddLastArg(CmdArgs, options::OPT_fthinlto_index_EQ);
   }
 
   if (Args.getLastArg(options::OPT_save_temps_EQ))
     Args.AddLastArg(CmdArgs, options::OPT_save_temps_EQ);
 
   // Embed-bitcode option.
   // Only white-listed flags below are allowed to be embedded.

clang/test/Driver/thinlto_backend.c

 // RUN: %clang -O2 %s -flto=thin -c -o %t.o
 // RUN: llvm-lto -thinlto -o %t %t.o
 
 // -fthinlto_index should be passed to cc1
-// RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -### 2>&1 | FileCheck %s -check-prefix=CHECK-THINLTOBE-ACTION
+// RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -### \
+// RUN:     2>&1 | FileCheck %s -check-prefix=CHECK-THINLTOBE-ACTION
 // CHECK-THINLTOBE-ACTION: -fthinlto-index=
+// CHECK-THINLTOBE-ACTION-SAME: {{"?-x"? "?ir"?}}
+
+// Check that this also works without -x ir.
+// RUN: %clang -O2 -o %t1.o %t.o -c -fthinlto-index=%t.thinlto.bc -### 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-THINLTOBE-ACTION
 
 // -save-temps should be passed to cc1
 // RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -save-temps -### 2>&1 | FileCheck %s -check-prefix=CHECK-SAVE-TEMPS -check-prefix=CHECK-SAVE-TEMPS-CWD
 // RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -save-temps=cwd -### 2>&1 | FileCheck %s -check-prefix=CHECK-SAVE-TEMPS -check-prefix=CHECK-SAVE-TEMPS-CWD
 // RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -save-temps=obj -### 2>&1 | FileCheck %s -check-prefix=CHECK-SAVE-TEMPS -check-prefix=CHECK-SAVE-TEMPS-OBJ
 // CHECK-SAVE-TEMPS-NOT: -emit-llvm-bc
 // CHECK-SAVE-TEMPS-CWD: -save-temps=cwd
 // CHECK-SAVE-TEMPS-OBJ: -save-temps=obj
 // CHECK-SAVE-TEMPS-NOT: -emit-llvm-bc
 
 // Ensure clang driver gives the expected error for incorrect input type
-// RUN: not %clang -O2 -o %t1.o %s -c -fthinlto-index=%t.thinlto.bc 2>&1 | FileCheck %s -check-prefix=CHECK-WARNING
-// CHECK-WARNING: error: invalid argument '-fthinlto-index={{.*}}' only allowed with '-x ir'
+// RUN: not %clang -O2 -o %t1.o %s -c -fthinlto-index=%t.thinlto.bc 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-WARNING
+// CHECK-WARNING: error: option '-fthinlto-index={{.*}}' requires input to be LLVM bitcode