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

1 files changed, 5 insertions, 2 deletions

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);