MandatoryPerformanceOptimizations: some refactoring

SwiftCompilerSources/Sources/Optimizer/ModulePasses/MandatoryPerformanceOptimizations.swift

@@ -52,10 +52,9 @@ private func optimizeFunctionsTopDown(using worklist: inout FunctionWorklist,
                                       _ moduleContext: ModulePassContext) {
   while let f = worklist.pop() {
     moduleContext.transform(function: f) { context in
-      if !context.loadFunction(function: f, loadCalleesRecursively: true) {
-        return
+      if context.loadFunction(function: f, loadCalleesRecursively: true) {
+        optimize(function: f, context, moduleContext, &worklist)
       }
-      optimize(function: f, context, moduleContext, &worklist)
     }
 
     // Generic specialization takes care of removing metatype arguments of generic functions.
@@ -316,8 +315,7 @@ private func shouldInline(apply: FullApplySite, callee: Function, alreadyInlined
 
 private extension FullApplySite {
   func resultIsUsedInGlobalInitialization() -> SmallProjectionPath? {
-    guard parentFunction.isGlobalInitOnceFunction,
-          let global = parentFunction.getInitializedGlobal() else {
+    guard let global = parentFunction.initializedGlobal else {
       return nil
     }
 
@@ -441,25 +439,6 @@ private extension Value {
   }
 }
 
-private extension Function {
-  /// Analyzes the global initializer function and returns global it initializes (from `alloc_global` instruction).
-  func getInitializedGlobal() -> GlobalVariable? {
-    if !isDefinition {
-      return nil
-    }
-    for inst in self.entryBlock.instructions {
-      switch inst {
-      case let agi as AllocGlobalInst:
-        return agi.global
-      default:
-        break
-      }
-    }
-
-    return nil
-  }
-}
-
 fileprivate struct FunctionWorklist {
   private(set) var functions = Array<Function>()
   private var pushedFunctions = Set<Function>()
@@ -481,20 +460,10 @@ fileprivate struct FunctionWorklist {
         pushIfNotVisited(f)
       }
 
-      // Annotated global init-once functions
-      if f.isGlobalInitOnceFunction {
-        if let global = f.getInitializedGlobal(),
-           global.mustBeInitializedStatically {
-          pushIfNotVisited(f)
-        }
-      }
-
-      // @const global init-once functions
-      if f.isGlobalInitOnceFunction {
-        if let global = f.getInitializedGlobal(),
-           global.mustBeInitializedStatically {
-          pushIfNotVisited(f)
-        }
+      // Initializers of globals which must be initialized statically.
+      if let global = f.initializedGlobal,
+         global.mustBeInitializedStatically {
+        pushIfNotVisited(f)
       }
     }
   }

SwiftCompilerSources/Sources/Optimizer/Utilities/OptUtils.swift

@@ -763,11 +763,14 @@ private struct EscapesToValueVisitor : EscapeVisitor {
 }
 
 extension Function {
+  /// Analyzes the global initializer function and returns global it initializes (from `alloc_global` instruction).
   var initializedGlobal: GlobalVariable? {
-    if !isGlobalInitOnceFunction {
+    guard isGlobalInitOnceFunction,
+          let firstBlock = blocks.first
+    else {
       return nil
     }
-    for inst in entryBlock.instructions {
+    for inst in firstBlock.instructions {
       if let allocGlobal = inst as? AllocGlobalInst {
         return allocGlobal.global
       }

SwiftCompilerSources/Sources/SIL/GlobalVariable.swift

@@ -69,6 +69,8 @@ final public class GlobalVariable : CustomStringConvertible, HasShortDescription
     return bridged.canBeInitializedStatically()
   }
 
+  /// True if the global has an attribute, like `@const` or `@section` which requires the global to be
+  /// initialized statically.
   public var mustBeInitializedStatically: Bool {
     return bridged.mustBeInitializedStatically()
   }