[Profiler] Only map implicit getters for lazy vars

This is the only implicit getter case we care
about, the rest do not contain user-written code.
This means that we now otherwise only ever map
explicit decls, which we need to SILGen anyway. As
such I believe this should fix rdar://39332957.

We do still potentially map implicit expressions,
but should only do so for explicit property
initializers. There is one remaining bug where we
can map an implicit property wrapper backing
initalizer, which I'm tracking in rdar://99931619.

Author: hamishknight

lib/SIL/IR/SILProfiler.cpp

@@ -77,10 +77,13 @@ static bool isUnmapped(ASTNode N) {
       return true;
     }
 
-    // Map implicit getters.
-    if (auto *accessor = dyn_cast<AccessorDecl>(AFD))
-      if (accessor->isImplicit() && accessor->isGetter())
+    // Map implicit getters for lazy variables.
+    if (auto *accessor = dyn_cast<AccessorDecl>(AFD)) {
+      if (accessor->isImplicit() && accessor->isGetter() &&
+          accessor->getStorage()->getAttrs().hasAttribute<LazyAttr>()) {
         return false;
+      }
+    }
   }
 
   // Skip any remaining implicit, or otherwise unsupported decls.

test/Profiler/unmapped.swift

@@ -0,0 +1,24 @@
+// RUN: %target-swift-frontend -Xllvm -sil-full-demangle -suppress-warnings -profile-generate -profile-coverage-mapping -emit-sorted-sil -emit-sil -module-name unmapped %s | %FileCheck %s
+// RUN: %target-swift-frontend -profile-generate -profile-coverage-mapping -emit-ir %s
+
+// This test is exclusively for AST that we should never profile, as there is
+// no interesting user-written code.
+
+// CHECK-NOT: increment_profiler_counter
+// CHECK-NOT: sil_coverage_map
+
+struct S {
+  // Don't profile the implicit accessor, or the implicit constructor.
+  var x: Int
+}
+
+// Don't profile any synthesized codable methods.
+struct R : Codable {
+  var x: String
+  var y: Int
+}
+
+// Don't profile the implicit rawValue.
+enum E : Int {
+  case a
+}