[X86] Teach Clang about -mfentry flag

Replace mcount calls with calls to fentry.

Reviewers: hfinkel, craig.topper

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28001

llvm-svn: 293649

1 files changed, 6 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 00bde1c5b28..126390957fb 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -860,8 +860,12 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
   // inlining, we just add an attribute to insert a mcount call in backend.
   // The attribute "counting-function" is set to mcount function name which is
   // architecture dependent.
-  if (CGM.getCodeGenOpts().InstrumentForProfiling)
-    Fn->addFnAttr("counting-function", getTarget().getMCountName());
+  if (CGM.getCodeGenOpts().InstrumentForProfiling) {
+    if (CGM.getCodeGenOpts().CallFEntry)
+      Fn->addFnAttr("fentry-call", "true");
+    else
+      Fn->addFnAttr("counting-function", getTarget().getMCountName());
+  }
 
   if (RetTy->isVoidType()) {
     // Void type; nothing to return.