Merge pull request swiftlang#78915 from kubamracek/embedded-string-switch-with-cache

[embedded] Support _findStringSwitchCaseWithCache in Embedded Swift

Author: kubamracek

SwiftCompilerSources/Sources/Optimizer/ModulePasses/MandatoryPerformanceOptimizations.swift

@@ -80,6 +80,17 @@ fileprivate struct PathFunctionTuple: Hashable {
 
 private func optimize(function: Function, _ context: FunctionPassContext, _ moduleContext: ModulePassContext, _ worklist: inout FunctionWorklist) {
   var alreadyInlinedFunctions: Set<PathFunctionTuple> = Set()
+
+  // ObjectOutliner replaces calls to findStringSwitchCase with _findStringSwitchCaseWithCache, but this happens as a late SIL optimization,
+  // which is a problem for Embedded Swift, because _findStringSwitchCaseWithCache will then reference non-specialized code. Solve this by
+  // eagerly linking and specializing _findStringSwitchCaseWithCache whenever findStringSwitchCase is found in the module.
+  if context.options.enableEmbeddedSwift {
+    if function.hasSemanticsAttribute("findStringSwitchCase"),
+        let f = context.lookupStdlibFunction(name: "_findStringSwitchCaseWithCache"),
+        context.loadFunction(function: f, loadCalleesRecursively: true) {
+      worklist.pushIfNotVisited(f)
+    }
+  }
 
   var changed = true
   while changed {

lib/SILOptimizer/IPO/DeadFunctionElimination.cpp

@@ -90,6 +90,7 @@ class DeadFunctionAndGlobalElimination {
   llvm::SmallPtrSet<void *, 32> AliveFunctionsAndTables;
 
   bool keepExternalWitnessTablesAlive;
+  bool keepStringSwitchIntrinsicAlive;
 
   /// Checks is a function is alive, e.g. because it is visible externally.
   bool isAnchorFunction(SILFunction *F) {
@@ -124,6 +125,15 @@ class DeadFunctionAndGlobalElimination {
     if (F->getRepresentation() == SILFunctionTypeRepresentation::ObjCMethod)
       return true;
 
+    // To support ObjectOutliner's replacing of calls to findStringSwitchCase
+    // with _findStringSwitchCaseWithCache. In Embedded Swift, we have to load
+    // the body of this function early and specialize it, so that ObjectOutliner
+    // can reference it later. To make this work we have to avoid DFE'ing it in
+    // the early DFE pass. Late DFE will take care of it if actually unused.
+    if (keepStringSwitchIntrinsicAlive &&
+        F->hasSemanticsAttr("findStringSwitchCaseWithCache"))
+      return true;
+
     return false;
   }
 
@@ -713,9 +723,11 @@ class DeadFunctionAndGlobalElimination {
 
 public:
   DeadFunctionAndGlobalElimination(SILModule *module,
-                                   bool keepExternalWitnessTablesAlive) :
+                                   bool keepExternalWitnessTablesAlive,
+                                   bool keepStringSwitchIntrinsicAlive) :
     Module(module),
-    keepExternalWitnessTablesAlive(keepExternalWitnessTablesAlive) {}
+    keepExternalWitnessTablesAlive(keepExternalWitnessTablesAlive),
+    keepStringSwitchIntrinsicAlive(keepStringSwitchIntrinsicAlive) {}
 
   /// The main entry point of the optimization.
   void eliminateFunctionsAndGlobals(SILModuleTransform *DFEPass) {
@@ -799,8 +811,10 @@ class DeadFunctionAndGlobalEliminationPass : public SILModuleTransform {
     // can eliminate such functions.
     getModule()->invalidateSILLoaderCaches();
 
-    DeadFunctionAndGlobalElimination deadFunctionElimination(getModule(),
-                                /*keepExternalWitnessTablesAlive*/ !isLateDFE);
+    DeadFunctionAndGlobalElimination deadFunctionElimination(
+        getModule(),
+        /*keepExternalWitnessTablesAlive*/ !isLateDFE,
+        /*keepStringSwitchIntrinsicAlive*/ !isLateDFE);
     deadFunctionElimination.eliminateFunctionsAndGlobals(this);
   }
 };

test/embedded/string-switch2.swift

@@ -0,0 +1,37 @@
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -wmo -O -Xlinker %swift_obj_root/lib/swift/embedded/%target-cpu-apple-macos/libswiftUnicodeDataTables.a) | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: executable_test
+// REQUIRES: optimized_stdlib
+// REQUIRES: swift_stdlib_no_asserts
+// REQUIRES: OS=macosx
+// REQUIRES: swift_feature_Embedded
+
+enum MyEnum: String {
+    case case1
+    case case2
+    case case3
+    case case4
+    case case5
+    case case6
+    case case7
+    case case8
+    case case9
+    case case10
+    case case11
+    case case12
+    case case13
+    case case14
+    case case15
+    case case16
+    case case17
+    case case18
+    case case19
+}
+
+var e = MyEnum.case1
+print(e.rawValue)
+e = MyEnum.case2
+print(e.rawValue)
+// CHECK: case1
+// CHECK: case2