[embedded] Don't produce PerfDiags when in non-WMO mode (e.g. when building during indexing)

Author: kubamracek

lib/SILOptimizer/Mandatory/PerformanceDiagnostics.cpp

@@ -805,6 +805,10 @@ class PerformanceDiagnosticsPass : public SILModuleTransform {
   void run() override {
     SILModule *module = getModule();
 
+    // Skip all performance/embedded diagnostics if not in WMO mode. Building in
+    // non-WMO mode currently results in false positives.
+    if (!module->isWholeModule()) return;
+
     PerformanceDiagnostics diagnoser(*module, getAnalysis<BasicCalleeAnalysis>());
 
     // Check that @_section, @_silgen_name is only on constant globals

test/SourceKit/Diagnostics/embedded_non_wmo.swift

@@ -0,0 +1,34 @@
+// Check that when emitting diagnostics in SourceKit, we don't report false positives in PerformanceDiagnostics (because WMO is disabled).
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %sourcekitd-test -req=diags %t/file1.swift -- %t/file1.swift %t/file2.swift -enable-experimental-feature Embedded | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: embedded_stdlib
+// REQUIRES: OS=macosx || OS=linux-gnu
+
+//--- file1.swift
+
+func foo() {
+    bar(Int.self)
+}
+
+@main
+struct Main {
+    static func main() {
+        foo()
+    }
+}
+
+//--- file2.swift
+
+func bar<T>(_ T: T.Type) {
+    
+}
+
+// CHECK:      {
+// CHECK-NEXT:   key.diagnostics: [
+// CHECK-NEXT:   ]
+// CHECK-NEXT: }