[SystemZ] Recognize mnop-mcount in backend

With -pg -mfentry -mnop-mcount, a nop is emitted instead of the call to
fentry.

Review: Ulrich Weigand
https://reviews.llvm.org/D67765

llvm-svn: 372950

2 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp b/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
index f03ed2014e4..10023e9e169 100644
--- a/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp
@@ -553,6 +553,12 @@ static unsigned EmitNop(MCContext &OutContext, MCStreamer &OutStreamer,
 void SystemZAsmPrinter::LowerFENTRY_CALL(const MachineInstr &MI,
                                          SystemZMCInstLower &Lower) {
   MCContext &Ctx = MF->getContext();
+  if (MF->getFunction().getFnAttribute("mnop-mcount")
+                       .getValueAsString() == "true") {
+    EmitNop(Ctx, *OutStreamer, 6, getSubtargetInfo());
+    return;
+  }
+
   MCSymbol *fentry = Ctx.getOrCreateSymbol("__fentry__");
   const MCSymbolRefExpr *Op =
       MCSymbolRefExpr::create(fentry, MCSymbolRefExpr::VK_PLT, Ctx);
diff --git a/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp b/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
index e73d6e82e6e..751034c2d41 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
@@ -346,6 +346,11 @@ public:
       : SelectionDAGISel(TM, OptLevel) {}
 
   bool runOnMachineFunction(MachineFunction &MF) override {
+    const Function &F = MF.getFunction();
+    if (F.getFnAttribute("mnop-mcount").getValueAsString() == "true" &&
+        F.getFnAttribute("fentry-call").getValueAsString() != "true")
+      report_fatal_error("mnop-mcount only supported with fentry-call");
+
     Subtarget = &MF.getSubtarget<SystemZSubtarget>();
     return SelectionDAGISel::runOnMachineFunction(MF);
   }