Disable PGO instrumentation on naked function (#75224)

We only allow for assembly code in naked function, and PGO
instrumentation (esp. temporal instrumentation that introduces a
function call) can wreak havoc in this.

Fix #74573

Author: serge-sans-paille

llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp

@@ -1783,6 +1783,8 @@ static bool skipPGOUse(const Function &F) {
 static bool skipPGOGen(const Function &F) {
   if (skipPGOUse(F))
     return true;
+  if (F.hasFnAttribute(llvm::Attribute::Naked))
+    return true;
   if (F.hasFnAttribute(llvm::Attribute::NoProfile))
     return true;
   if (F.hasFnAttribute(llvm::Attribute::SkipProfile))

llvm/test/Transforms/PGOProfile/timestamp.ll

@@ -3,10 +3,21 @@
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
+; CHECK-LABEL: define void @foo(
 define void @foo() {
 entry:
   ; CHECK: call void @llvm.instrprof.timestamp({{.*}})
   ret void
 }
 
-; CHECK: declare void @llvm.instrprof.timestamp(
+; CHECK-LABEL: define void @bar(
+define void @bar() #0 {
+entry:
+  ; CHECK-NOT: call void @llvm.instrprof.timestamp({{.*}})
+  call void asm sideeffect "retq;", "~{dirflag},~{fpsr},~{flags}"()
+  unreachable
+}
+
+; CHECK-LABEL: declare void @llvm.instrprof.timestamp(
+
+attributes #0 = { naked }