Add -finstrument-function-entry-bare flag

This is an instrumentation flag that's similar to
-finstrument-functions, but it only inserts calls on function entry, the
calls are inserted post-inlining, and they don't take any arugments.

This is intended for users who want to instrument function entry with
minimal overhead.

(-pg would be another alternative, but forces frame pointer emission and
affects link flags, so is probably best left alone to be used for
generating gcov data.)

Differential revision: https://reviews.llvm.org/D40276

llvm-svn: 318785

3 files changed, 22 insertions, 11 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 8544da3da7f..6b8359141be 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -355,10 +355,11 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
   llvm::DebugLoc Loc = EmitReturnBlock();
 
   if (ShouldInstrumentFunction()) {
-    CurFn->addFnAttr(!CGM.getCodeGenOpts().InstrumentFunctionsAfterInlining
-                         ? "instrument-function-exit"
-                         : "instrument-function-exit-inlined",
-                     "__cyg_profile_func_exit");
+    if (CGM.getCodeGenOpts().InstrumentFunctions)
+      CurFn->addFnAttr("instrument-function-exit", "__cyg_profile_func_exit");
+    if (CGM.getCodeGenOpts().InstrumentFunctionsAfterInlining)
+      CurFn->addFnAttr("instrument-function-exit-inlined",
+                       "__cyg_profile_func_exit");
   }
 
   // Emit debug descriptor for function end.
@@ -443,7 +444,8 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
 /// instrumented with __cyg_profile_func_* calls
 bool CodeGenFunction::ShouldInstrumentFunction() {
   if (!CGM.getCodeGenOpts().InstrumentFunctions &&
-      !CGM.getCodeGenOpts().InstrumentFunctionsAfterInlining)
+      !CGM.getCodeGenOpts().InstrumentFunctionsAfterInlining &&
+      !CGM.getCodeGenOpts().InstrumentFunctionEntryBare)
     return false;
   if (!CurFuncDecl || CurFuncDecl->hasAttr<NoInstrumentFunctionAttr>())
     return false;
@@ -982,10 +984,14 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
   }
 
   if (ShouldInstrumentFunction()) {
-    Fn->addFnAttr(!CGM.getCodeGenOpts().InstrumentFunctionsAfterInlining
-                      ? "instrument-function-entry"
-                      : "instrument-function-entry-inlined",
-                  "__cyg_profile_func_enter");
+    if (CGM.getCodeGenOpts().InstrumentFunctions)
+      CurFn->addFnAttr("instrument-function-entry", "__cyg_profile_func_enter");
+    if (CGM.getCodeGenOpts().InstrumentFunctionsAfterInlining)
+      CurFn->addFnAttr("instrument-function-entry-inlined",
+                       "__cyg_profile_func_enter");
+    if (CGM.getCodeGenOpts().InstrumentFunctionEntryBare)
+      CurFn->addFnAttr("instrument-function-entry-inlined",
+                       "__cyg_profile_func_enter_bare");
   }
 
   // Since emitting the mcount call here impacts optimizations such as function
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 2f1fa4af807..3ab28d471be 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3554,8 +3554,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                     options::OPT_fno_unique_section_names, true))
     CmdArgs.push_back("-fno-unique-section-names");
 
-  Args.AddLastArg(CmdArgs, options::OPT_finstrument_functions,
-                  options::OPT_finstrument_functions_after_inlining);
+  if (auto *A = Args.getLastArg(
+      options::OPT_finstrument_functions,
+      options::OPT_finstrument_functions_after_inlining,
+      options::OPT_finstrument_function_entry_bare))
+    A->render(Args, CmdArgs);
 
   addPGOAndCoverageFlags(C, D, Output, Args, CmdArgs);
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 384124bee2b..3d484170f82 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -782,6 +782,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.InstrumentFunctions = Args.hasArg(OPT_finstrument_functions);
   Opts.InstrumentFunctionsAfterInlining =
       Args.hasArg(OPT_finstrument_functions_after_inlining);
+  Opts.InstrumentFunctionEntryBare =
+      Args.hasArg(OPT_finstrument_function_entry_bare);
   Opts.XRayInstrumentFunctions = Args.hasArg(OPT_fxray_instrument);
   Opts.XRayInstructionThreshold =
       getLastArgIntValue(Args, OPT_fxray_instruction_threshold_EQ, 200, Diags);