[PCH] Add a fno-pch-timestamp option to cc1 to disable inclusion of timestamps in PCH files.

This is to allow distributed build systems, that do not preserve time stamps, to use PCH files.

Second and last part of the patch proposed at:

Differential Revision: http://reviews.llvm.org/D20867

llvm-svn: 275267

7 files changed, 42 insertions, 3 deletions

diff --git a/clang/include/clang/Driver/CC1Options.td b/clang/include/clang/Driver/CC1Options.td
index 3402d8d6240..1401984c2a3 100644
--- a/clang/include/clang/Driver/CC1Options.td
+++ b/clang/include/clang/Driver/CC1Options.td
@@ -509,6 +509,8 @@ def find_pch_source_EQ : Joined<["-"], "find-pch-source=">,
   HelpText<"When building a pch, try to find the input file in include "
            "directories, as if it had been included by the argument passed "
            "to this flag.">;
+def fno_pch_timestamp : Flag<["-"], "fno-pch-timestamp">,
+  HelpText<"Disable inclusion of timestamp in precompiled headers">;
   
 //===----------------------------------------------------------------------===//
 // Language Options
diff --git a/clang/include/clang/Frontend/FrontendOptions.h b/clang/include/clang/Frontend/FrontendOptions.h
index d49d8de6f58..a75523f2564 100644
--- a/clang/include/clang/Frontend/FrontendOptions.h
+++ b/clang/include/clang/Frontend/FrontendOptions.h
@@ -154,6 +154,8 @@ public:
                                            ///< implicit module build.
   unsigned ModulesEmbedAllFiles : 1;       ///< Whether we should embed all used
                                            ///< files into the PCM file.
+  unsigned IncludeTimestamps : 1;          ///< Whether timestamps should be
+                                           ///< written to the produced PCH file.
 
   CodeCompleteOptions CodeCompleteOpts;
 
@@ -278,8 +280,8 @@ public:
     SkipFunctionBodies(false), UseGlobalModuleIndex(true),
     GenerateGlobalModuleIndex(true), ASTDumpDecls(false), ASTDumpLookups(false),
     BuildingImplicitModule(false), ModulesEmbedAllFiles(false),
-    ARCMTAction(ARCMT_None), ObjCMTAction(ObjCMT_None),
-    ProgramAction(frontend::ParseSyntaxOnly)
+    IncludeTimestamps(true), ARCMTAction(ARCMT_None),
+    ObjCMTAction(ObjCMT_None), ProgramAction(frontend::ParseSyntaxOnly)
   {}
 
   /// getInputKindForExtension - Return the appropriate input kind for a file
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 59cb40108ac..7bc91ad79bf 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1197,6 +1197,7 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.ModuleFiles = Args.getAllArgValues(OPT_fmodule_file);
   Opts.ModulesEmbedFiles = Args.getAllArgValues(OPT_fmodules_embed_file_EQ);
   Opts.ModulesEmbedAllFiles = Args.hasArg(OPT_fmodules_embed_all_files);
+  Opts.IncludeTimestamps = !Args.hasArg(OPT_fno_pch_timestamp);
 
   Opts.CodeCompleteOpts.IncludeMacros
     = Args.hasArg(OPT_code_completion_macros);
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index dd5479ca71a..6ddb316fd08 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -92,7 +92,10 @@ GeneratePCHAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
   std::vector<std::unique_ptr<ASTConsumer>> Consumers;
   Consumers.push_back(llvm::make_unique<PCHGenerator>(
                         CI.getPreprocessor(), OutputFile, nullptr, Sysroot,
-                        Buffer, CI.getFrontendOpts().ModuleFileExtensions));
+                        Buffer, CI.getFrontendOpts().ModuleFileExtensions,
+                        /*AllowASTWithErrors*/false,
+                        /*IncludeTimestamps*/
+                          +CI.getFrontendOpts().IncludeTimestamps));
   Consumers.push_back(CI.getPCHContainerWriter().CreatePCHContainerGenerator(
       CI, InFile, OutputFile, OS, Buffer));
 
diff --git a/clang/test/PCH/Inputs/pragma-once2-pch.h b/clang/test/PCH/Inputs/pragma-once2-pch.h
new file mode 100644
index 00000000000..642b50f15aa
--- /dev/null
+++ b/clang/test/PCH/Inputs/pragma-once2-pch.h
@@ -0,0 +1 @@
+#include "pragma-once2.h"
diff --git a/clang/test/PCH/Inputs/pragma-once2.h b/clang/test/PCH/Inputs/pragma-once2.h
new file mode 100644
index 00000000000..7ed4a95520e
--- /dev/null
+++ b/clang/test/PCH/Inputs/pragma-once2.h
@@ -0,0 +1,3 @@
+#pragma once
+
+inline void f() {}
diff --git a/clang/test/PCH/include-timestamp.cpp b/clang/test/PCH/include-timestamp.cpp
new file mode 100644
index 00000000000..1add189c699
--- /dev/null
+++ b/clang/test/PCH/include-timestamp.cpp
@@ -0,0 +1,27 @@
+// Test that the timestamp is not included in the produced pch file with
+// -fno-pch-timestamp.
+
+// Check timestamp is included by default.
+// RUN: %clang_cc1 -x c++-header -emit-pch -o %t %S/Inputs/pragma-once2-pch.h
+// RUN: touch -m -a -t 201008011501 %S/Inputs/pragma-once2.h
+// RUN: not %clang_cc1 -include-pch %t %s 2>&1 | FileCheck -check-prefix=CHECK-TIMESTAMP %s
+
+// Check bitcode output as well.
+// RUN: llvm-bcanalyzer -dump %t | FileCheck -check-prefix=CHECK-BITCODE-TIMESTAMP-ON %s
+
+// Check timestamp inclusion is disabled by -fno-pch-timestamp.
+// RUN: %clang_cc1 -x c++-header -emit-pch -o %t %S/Inputs/pragma-once2-pch.h -fno-pch-timestamp
+// RUN: touch -m -a -t 201008011502 %S/Inputs/pragma-once2.h
+// RUN: %clang_cc1 -include-pch %t %s 2>&1
+
+// Check bitcode output as well.
+// RUN: llvm-bcanalyzer -dump %t | FileCheck -check-prefix=CHECK-BITCODE-TIMESTAMP-OFF %s
+
+#include "Inputs/pragma-once2.h"
+
+void g() { f(); }
+
+// CHECK-BITCODE-TIMESTAMP-ON: <INPUT_FILE abbrevid={{.*}} op0={{.*}} op1={{.*}} op2={{[^0]}}
+// CHECK-BITCODE-TIMESTAMP-OFF: <INPUT_FILE abbrevid={{.*}} op0={{.*}} op1={{.*}} op2={{[0]}}
+
+// CHECK-TIMESTAMP: fatal error: file {{.*}} has been modified since the precompiled header {{.*}} was built