[Clang FE, SystemZ] Don't add "true" value for the "mnop-mcount" attribute.

[jonpa]

Summary

Let the "mnop-mcount" function attribute simply be present or non-present.

Update SystemZ backend as well to use hasFnAttribute() instead.

[uweigand]

LGTM.

[jonpa]

ca52059

clang/lib/CodeGen/CodeGenFunction.cpp

if (!CurFuncDecl || !CurFuncDecl->hasAttr<NoInstrumentFunctionAttr>()) {
       if (CGM.getCodeGenOpts().MNopMCount) {
         if (getContext().getTargetInfo().getTriple().getArch() !=
             llvm::Triple::systemz)
           CGM.getDiags().Report(diag::err_opt_not_valid_on_target)
             << "-mnop-mcount";
         if (!CGM.getCodeGenOpts().CallFEntry)
           CGM.getDiags().Report(diag::err_opt_not_valid_without_opt)
             << "-mnop-mcount" << "-mfentry";
-        Fn->addFnAttr("mnop-mcount", "true");
+        Fn->addFnAttr("mnop-mcount");
       }
     }
   }
 
   if (CGM.getCodeGenOpts().PackedStack) {
     if (getContext().getTargetInfo().getTriple().getArch() !=
         llvm::Triple::systemz)
       CGM.getDiags().Report(diag::err_opt_not_valid_on_target)

clang/test/CodeGen/mnop-mcount.c

 int foo(void) {
   return 0;
 }
 
 int __attribute__((no_instrument_function)) no_instrument(void) {
   return foo();
 }
 
-//CHECK: attributes #0 = { {{.*}}"mnop-mcount"="true"{{.*}} }
+//CHECK: attributes #0 = { {{.*}}"mnop-mcount"{{.*}} }
 //CHECK: attributes #1 = { {{.*}} }
-//CHECK-NOT: attributes #1 = { {{.*}}"mnop-mcount"="true"{{.*}} }
+//CHECK-NOT: attributes #1 = { {{.*}}"mnop-mcount"{{.*}} }
 //NOMFENTRY: error: option '-mnop-mcount' cannot be specified without '-mfentry'
 //NOPG-NOT: attributes #0 = { {{.*}}"mnop-mcount"{{.*}} }
 //NOPG-NOT: attributes #1 = { {{.*}}"mnop-mcount"{{.*}} }
 //X86: error: option '-mnop-mcount' cannot be specified on this target

llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp

else {
     OutStreamer.EmitLabel(DotSym);
     return 6;
   }
 }
 
 void SystemZAsmPrinter::LowerFENTRY_CALL(const MachineInstr &MI,
                                          SystemZMCInstLower &Lower) {
   MCContext &Ctx = MF->getContext();
-  if (MF->getFunction().getFnAttribute("mnop-mcount")
-                       .getValueAsString() == "true") {
+  if (MF->getFunction().hasFnAttribute("mnop-mcount")) {
     EmitNop(Ctx, *OutStreamer, 6, getSubtargetInfo());
     return;
   }
 
   MCSymbol *fentry = Ctx.getOrCreateSymbol("__fentry__");
   const MCSymbolRefExpr *Op =
       MCSymbolRefExpr::create(fentry, MCSymbolRefExpr::VK_PLT, Ctx);
   OutStreamer->EmitInstruction(MCInstBuilder(SystemZ::BRASL)

llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp

class SystemZDAGToDAGISel : public SelectionDAGISel {
   SDValue expandSelectBoolean(SDNode *Node);
 
 public:
   SystemZDAGToDAGISel(SystemZTargetMachine &TM, CodeGenOpt::Level OptLevel)
       : SelectionDAGISel(TM, OptLevel) {}
 
   bool runOnMachineFunction(MachineFunction &MF) override {
     const Function &F = MF.getFunction();
-    if (F.getFnAttribute("mnop-mcount").getValueAsString() == "true" &&
+    if (F.hasFnAttribute("mnop-mcount") &&
         F.getFnAttribute("fentry-call").getValueAsString() != "true")
       report_fatal_error("mnop-mcount only supported with fentry-call");
 
     Subtarget = &MF.getSubtarget<SystemZSubtarget>();
     return SelectionDAGISel::runOnMachineFunction(MF);
   }
 
   // Override MachineFunctionPass.

llvm/test/CodeGen/SystemZ/mnop-mcount-01.ll

 
 ; CHECK-LABEL: @test2
 ; CHECK-NOT: brasl %r0, __fentry__
 ; CHECK: brcl 0, .Ltmp0
 ; CHECK: br %r14
 }
 
 attributes #0 = { "fentry-call"="true" }
-attributes #1 = { "fentry-call"="true" "mnop-mcount"="true" }
+attributes #1 = { "fentry-call"="true" "mnop-mcount" }
 

llvm/test/CodeGen/SystemZ/mnop-mcount-02.ll

 ; RUN: not llc %s -mtriple=s390x-linux-gnu -o - 2>&1 | FileCheck %s
 ;
 ; CHECK: LLVM ERROR: mnop-mcount only supported with fentry-call
 
 define void @test1() #0 {
 entry:
   ret void
 }
 
-attributes #0 = { "instrument-function-entry-inlined"="mcount" "mnop-mcount"="true" }
-
+attributes #0 = { "instrument-function-entry-inlined"="mcount" "mnop-mcount" }