accept 'clang++ -c a.pch -o a.o' to create PCH's object file

This way should be the same like with a.pcm for modules.
An alternative way is 'clang++ -c empty.cpp -include-pch a.pch -o a.o
-Xclang -building-pch-with-obj', which is what clang-cl's /Yc does
internally.

Differential Revision: https://reviews.llvm.org/D83716

(cherry picked from commit 3895466e2c336c0797710ae35150ba1ce6bc0b96)

4 files changed, 47 insertions, 8 deletions

diff --git a/clang/lib/Driver/Types.cpp b/clang/lib/Driver/Types.cpp
index 399e26d..2050dffa 100644
--- a/clang/lib/Driver/Types.cpp
+++ b/clang/lib/Driver/Types.cpp
@@ -141,7 +141,7 @@ bool types::isAcceptedByClang(ID Id) {
   case TY_CXXHeader: case TY_PP_CXXHeader:
   case TY_ObjCXXHeader: case TY_PP_ObjCXXHeader:
   case TY_CXXModule: case TY_PP_CXXModule:
-  case TY_AST: case TY_ModuleFile:
+  case TY_AST: case TY_ModuleFile: case TY_PCH:
   case TY_LLVM_IR: case TY_LLVM_BC:
     return true;
   }
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 75d7cf5..73114c6 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2022,8 +2022,9 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
     // FIXME: Supporting '<lang>-header-cpp-output' would be useful.
     bool Preprocessed = XValue.consume_back("-cpp-output");
     bool ModuleMap = XValue.consume_back("-module-map");
-    IsHeaderFile =
-        !Preprocessed && !ModuleMap && XValue.consume_back("-header");
+    IsHeaderFile = !Preprocessed && !ModuleMap &&
+                   XValue != "precompiled-header" &&
+                   XValue.consume_back("-header");
 
     // Principal languages.
     DashX = llvm::StringSwitch<InputKind>(XValue)
@@ -2050,7 +2051,7 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
       DashX = llvm::StringSwitch<InputKind>(XValue)
                   .Case("cpp-output", InputKind(Language::C).getPreprocessed())
                   .Case("assembler-with-cpp", Language::Asm)
-                  .Cases("ast", "pcm",
+                  .Cases("ast", "pcm", "precompiled-header",
                          InputKind(Language::Unknown, InputKind::Precompiled))
                   .Case("ir", Language::LLVM_IR)
                   .Default(Language::Unknown);
diff --git a/clang/test/Driver/pch-codegen.cpp b/clang/test/Driver/pch-codegen.cpp
new file mode 100644
index 0000000..1b12510
--- /dev/null
+++ b/clang/test/Driver/pch-codegen.cpp
@@ -0,0 +1,38 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+
+// Create PCH without codegen.
+// RUN: %clang -x c++-header %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-CREATE
+// CHECK-PCH-CREATE: -emit-pch
+// CHECK-PCH-CREATE-NOT: -fmodules-codegen
+// CHECK-PCH-CREATE-NOT: -fmodules-debuginfo
+
+// Create PCH with -fmodules-codegen.
+// RUN: %clang -x c++-header -Xclang -fmodules-codegen %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-CODEGEN-CREATE
+// CHECK-PCH-CODEGEN-CREATE: -emit-pch
+// CHECK-PCH-CODEGEN-CREATE: -fmodules-codegen
+// CHECK-PCH-CODEGEN-CREATE: "-x" "c++-header"
+// CHECK-PCH-CODEGEN-CREATE-NOT: -fmodules-debuginfo
+
+// Create PCH with -fmodules-debuginfo.
+// RUN: %clang -x c++-header -Xclang -fmodules-debuginfo %S/../Modules/Inputs/codegen-flags/foo.h -g -o %t/foo-di.pch -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-DEBUGINFO-CREATE
+// CHECK-PCH-DEBUGINFO-CREATE: -emit-pch
+// CHECK-PCH-DEBUGINFO-CREATE: -fmodules-debuginfo
+// CHECK-PCH-DEBUGINFO-CREATE: "-x" "c++-header"
+// CHECK-PCH-DEBUGINFO-CREATE-NOT: -fmodules-codegen
+
+// Create PCH's object file for -fmodules-codegen.
+// RUN: touch %t/foo-cg.pch
+// RUN: %clang -c %t/foo-cg.pch -o %t/foo-cg.o -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-CODEGEN-OBJ
+// CHECK-PCH-CODEGEN-OBJ: -emit-obj
+// CHECK-PCH-CODEGEN-OBJ: "-main-file-name" "foo-cg.pch"
+// CHECK-PCH-CODEGEN-OBJ: "-o" "{{.*}}foo-cg.o"
+// CHECK-PCH-CODEGEN-OBJ: "-x" "precompiled-header"
+
+// Create PCH's object file for -fmodules-debuginfo.
+// RUN: touch %t/foo-di.pch
+// RUN: %clang -c %t/foo-di.pch -g -o %t/foo-di.o -### 2>&1 | FileCheck %s -check-prefix=CHECK-PCH-DEBUGINFO-OBJ
+// CHECK-PCH-DEBUGINFO-OBJ: -emit-obj
+// CHECK-PCH-DEBUGINFO-OBJ: "-main-file-name" "foo-di.pch"
+// CHECK-PCH-DEBUGINFO-OBJ: "-o" "{{.*}}foo-di.o"
+// CHECK-PCH-DEBUGINFO-OBJ: "-x" "precompiled-header"
diff --git a/clang/test/PCH/codegen.cpp b/clang/test/PCH/codegen.cpp
index 49ed30a..9d81731 100644
--- a/clang/test/PCH/codegen.cpp
+++ b/clang/test/PCH/codegen.cpp
@@ -9,8 +9,8 @@
 // RUN: %clang_cc1 -triple=x86_64-linux-gnu -fmodules-codegen -x c++-header -building-pch-with-obj -emit-pch %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch
 // RUN: %clang_cc1 -triple=x86_64-linux-gnu -fmodules-debuginfo -x c++-header -building-pch-with-obj -emit-pch %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-di.pch
 
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - %s -include-pch %t/foo-cg.pch -building-pch-with-obj -fmodules-codegen | FileCheck --check-prefix=CG %s
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - %s -include-pch %t/foo-di.pch -building-pch-with-obj -fmodules-debuginfo | FileCheck --check-prefix=DI %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -x precompiled-header %t/foo-cg.pch | FileCheck --check-prefix=CG %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -x precompiled-header %t/foo-di.pch | FileCheck --check-prefix=DI %s
 
 // RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -include-pch %t/foo-cg.pch %S/../Modules/Inputs/codegen-flags/use.cpp | FileCheck --check-prefix=CG-USE %s
 // RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -include-pch %t/foo-di.pch %S/../Modules/Inputs/codegen-flags/use.cpp | FileCheck --check-prefix=DI-USE %s
@@ -20,8 +20,8 @@
 // RUN: %clang_cc1 -triple=x86_64-linux-gnu -fmodules-codegen -x c++-header -building-pch-with-obj -emit-pch -fpch-instantiate-templates %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch
 // RUN: %clang_cc1 -triple=x86_64-linux-gnu -fmodules-debuginfo -x c++-header -building-pch-with-obj -emit-pch -fpch-instantiate-templates %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-di.pch
 
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - %s -include-pch %t/foo-cg.pch -building-pch-with-obj -fmodules-codegen | FileCheck --check-prefix=CG %s
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - %s -include-pch %t/foo-di.pch -building-pch-with-obj -fmodules-debuginfo | FileCheck --check-prefix=DI %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -x precompiled-header %t/foo-cg.pch | FileCheck --check-prefix=CG %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -x precompiled-header %t/foo-di.pch | FileCheck --check-prefix=DI %s
 
 // RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -include-pch %t/foo-cg.pch %S/../Modules/Inputs/codegen-flags/use.cpp | FileCheck --check-prefix=CG-USE %s
 // RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -include-pch %t/foo-di.pch %S/../Modules/Inputs/codegen-flags/use.cpp | FileCheck --check-prefix=DI-USE %s