PerformanceDiagnostics: don't issue a metatype diagnostics when using MemoryLayout

The metatype is not code-gend for the memory layout builtins.
Also fix the wrong help test for the -experimental-performance-annotations option.

Author: eeckstein

include/swift/Option/Options.td

@@ -812,7 +812,7 @@ def CrossModuleOptimization : Flag<["-"], "cross-module-optimization">,
 
 def ExperimentalPerformanceAnnotations : Flag<["-"], "experimental-performance-annotations">,
   Flags<[HelpHidden, FrontendOption]>,
-  HelpText<"Perform cross-module optimization">;
+  HelpText<"Enable experimental performance annotations">;
 
 def RemoveRuntimeAsserts : Flag<["-"], "remove-runtime-asserts">,
   Flags<[FrontendOption]>,

lib/SIL/Utils/InstructionUtils.cpp

@@ -667,10 +667,9 @@ RuntimeEffect swift::getRuntimeEffect(SILInstruction *inst, SILType &impactType)
       if (auto selfType = instTy->getAs<DynamicSelfType>())
         instTy = selfType->getSelfType();
       auto *cl = instTy->getClassOrBoundGenericClass();
-      bool isForeign =
-          cl->getObjectModel() == ReferenceCounting::ObjC ||
-          cl->isForeign();
-      if ((cl && isForeign) || instTy->isAnyObject())
+      bool isForeign = cl && (cl->getObjectModel() == ReferenceCounting::ObjC ||
+                              cl->isForeign());
+      if (isForeign || instTy->isAnyObject())
         return RuntimeEffect::MetaData | RuntimeEffect::ObjectiveC;
       return RuntimeEffect::MetaData;
     }

lib/SILOptimizer/Mandatory/PerformanceDiagnostics.cpp

@@ -154,6 +154,26 @@ bool PerformanceDiagnostics::visitCallee(FullApplySite as,
   return false;
 }
 
+static bool metatypeUsesAreNotRelevant(MetatypeInst *mt) {
+  for (Operand *use : mt->getUses()) {
+    if (auto  *bi = dyn_cast<BuiltinInst>(use->getUser())) {
+      switch (bi->getBuiltinInfo().ID) {
+        case BuiltinValueKind::Sizeof:
+        case BuiltinValueKind::Strideof:
+        case BuiltinValueKind::Alignof:
+        case BuiltinValueKind::IsPOD:
+        case BuiltinValueKind::IsConcrete:
+        case BuiltinValueKind::IsBitwiseTakable:
+          continue;
+        default:
+          break;
+      }
+    }
+    return false;
+  }
+  return true;
+}
+
 bool PerformanceDiagnostics::visitInst(SILInstruction *inst,
                                           PerformanceConstraints perfConstr,
                                           LocWithParent *parentLoc) {
@@ -191,6 +211,10 @@ bool PerformanceDiagnostics::visitInst(SILInstruction *inst,
       diagnose(loc, diag::performance_metadata, "generic function calls");
       break;
     }
+    case SILInstructionKind::MetatypeInst:
+      if (metatypeUsesAreNotRelevant(cast<MetatypeInst>(inst)))
+        break;
+      LLVM_FALLTHROUGH;
     default:
       // We didn't recognize the instruction, so try to give an error message
       // based on the involved type.

test/SILOptimizer/performance-annotations.swift

@@ -85,6 +85,11 @@ func testUnsafePerformance(_ idx: Int) -> [Int] {
   return _unsafePerformance { [10, 20, 30, 40] }
 }
 
+@_noAllocation
+func testMemoryLayout() -> Int {
+  return MemoryLayout<Int>.size + MemoryLayout<Int>.stride + MemoryLayout<Int>.alignment
+}
+
 class MyError : Error {}
 
 @_noLocks