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

1 files changed, 4 insertions, 3 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index c34c2a1..0b5f335 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);