[CodeGen] Add an option to suppress output of llvm.ident

Summary:
By default Clang outputs its version (including git commit hash, in
case of trunk builds) into object and assembly files. It might be
useful to have an option to disable this, especially for debugging
purposes.
This patch implements new command line flags -Qn and -Qy (the names
are chosen for compatibility with GCC). -Qn disables output of
the 'llvm.ident' metadata string and the 'producer' debug info. -Qy
(enabled by default) does the opposite.

Reviewers: faisalv, echristo, aprantl

Reviewed By: aprantl

Subscribers: aprantl, cfe-commits, JDevlieghere, rogfer01

Differential Revision: https://reviews.llvm.org/D45255

llvm-svn: 330442

7 files changed, 33 insertions, 3 deletions

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index ca6267dad4e..5290d8ad482 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -396,7 +396,10 @@ def O_flag : Flag<["-"], "O">, Flags<[CC1Option]>, Alias<O>, AliasArgs<["2"]>;
 def Ofast : Joined<["-"], "Ofast">, Group<O_Group>, Flags<[CC1Option]>;
 def P : Flag<["-"], "P">, Flags<[CC1Option]>, Group<Preprocessor_Group>,
   HelpText<"Disable linemarker output in -E mode">;
-def Qn : Flag<["-"], "Qn">, IgnoredGCCCompat;
+def Qy : Flag<["-"], "Qy">, Flags<[CC1Option]>,
+  HelpText<"Emit metadata containing compiler name and version">;
+def Qn : Flag<["-"], "Qn">, Flags<[CC1Option]>,
+  HelpText<"Do not emit metadata containing compiler name and version">;
 def Qunused_arguments : Flag<["-"], "Qunused-arguments">, Flags<[DriverOption, CoreOption]>,
   HelpText<"Don't emit warning for unused driver arguments">;
 def Q : Flag<["-"], "Q">, IgnoredGCCCompat;
diff --git a/clang/include/clang/Frontend/CodeGenOptions.def b/clang/include/clang/Frontend/CodeGenOptions.def
index 684f99e1de3..1684dbdb557 100644
--- a/clang/include/clang/Frontend/CodeGenOptions.def
+++ b/clang/include/clang/Frontend/CodeGenOptions.def
@@ -69,6 +69,7 @@ CODEGENOPT(EmitDeclMetadata  , 1, 0) ///< Emit special metadata indicating what
                                      ///< Decl* various IR entities came from.
                                      ///< Only useful when running CodeGen as a
                                      ///< subroutine.
+CODEGENOPT(EmitVersionIdentMetadata , 1, 1) ///< Emit compiler version metadata.
 CODEGENOPT(EmitGcovArcs      , 1, 0) ///< Emit coverage data files, aka. GCDA.
 CODEGENOPT(EmitGcovNotes     , 1, 0) ///< Emit coverage "notes" files, aka GCNO.
 CODEGENOPT(EmitOpenCLArgMetadata , 1, 0) ///< Emit OpenCL kernel arg metadata.
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index bdd326d70e4..474018c065e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -577,7 +577,8 @@ void CGDebugInfo::CreateCompileUnit() {
                           remapDIPath(getCurrentDirname()),
                           CSInfo,
                           getSource(SM, SM.getMainFileID())),
-      Producer, LO.Optimize || CGOpts.PrepareForLTO || CGOpts.EmitSummaryIndex,
+      CGOpts.EmitVersionIdentMetadata ? Producer : "",
+      LO.Optimize || CGOpts.PrepareForLTO || CGOpts.EmitSummaryIndex,
       CGOpts.DwarfDebugFlags, RuntimeVers,
       CGOpts.EnableSplitDwarf ? "" : CGOpts.SplitDwarfFile, EmissionKind,
       0 /* DWOid */, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 17d9db3399f..707b826418a 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -571,7 +571,8 @@ void CodeGenModule::Release() {
   if (DebugInfo)
     DebugInfo->finalize();
 
-  EmitVersionIdentMetadata();
+  if (getCodeGenOpts().EmitVersionIdentMetadata)
+    EmitVersionIdentMetadata();
 
   EmitTargetMetadata();
 }
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index a3cb0f21ed5..6c5e2caae4a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4408,6 +4408,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     }
   }
 
+  if (!Args.hasFlag(options::OPT_Qy, options::OPT_Qn, true))
+    CmdArgs.push_back("-Qn");
+
   // -fcommon is the default unless compiling kernel code or the target says so
   bool NoCommonDefault = KernelOrKext || isNoCommonDefault(RawTriple);
   if (!Args.hasFlag(options::OPT_fcommon, options::OPT_fno_common,
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 67e15b41add..f904e65e724 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1112,6 +1112,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.EmitCheckPathComponentsToStrip = getLastArgIntValue(
       Args, OPT_fsanitize_undefined_strip_path_components_EQ, 0, Diags);
 
+  Opts.EmitVersionIdentMetadata = Args.hasFlag(OPT_Qy, OPT_Qn, true);
+
   return Success;
 }
 
diff --git a/clang/test/CodeGen/no-ident-version.c b/clang/test/CodeGen/no-ident-version.c
new file mode 100644
index 00000000000..35f84f0500d
--- /dev/null
+++ b/clang/test/CodeGen/no-ident-version.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited -o - %s \
+// RUN:   | FileCheck --check-prefix=CHECK-NONE %s
+// RUN: %clang_cc1 -Qn -emit-llvm -debug-info-kind=limited -o - %s \
+// RUN:   | FileCheck --check-prefix=CHECK-QN %s
+// RUN: %clang_cc1 -Qy -emit-llvm -debug-info-kind=limited -o - %s \
+// RUN:   | FileCheck --check-prefix=CHECK-QY %s
+
+// CHECK-NONE: define i32 @main()
+// CHECK-NONE: llvm.ident
+// CHECK-NONE: producer:
+
+// CHECK-QN: define i32 @main()
+// CHECK-QN-NOT: llvm.ident
+// CHECK-QN-NOT: producer:
+
+// CHECK-QY: define i32 @main()
+// CHECK-QY: llvm.ident
+// CHECK-QY: producer:
+int main(void) {}