Merge pull request swiftlang#18711 from aschwaighofer/renable_inlining_isOSVersionAtLeast

Re-enable inlining of the _stdlib_isOSVersionAtLeast macro

Author: aschwaighofer

lib/IRGen/AllocStackHoisting.cpp

@@ -332,6 +332,20 @@ class HoistAllocStack {
 };
 } // end anonymous namespace
 
+bool indicatesDynamicAvailabilityCheckUse(SILInstruction *I) {
+  auto *Apply = dyn_cast<ApplyInst>(I);
+  if (!Apply)
+    return false;
+  if (Apply->hasSemantics("availability.osversion"))
+    return true;
+  auto *FunRef = Apply->getReferencedFunction();
+  if (!FunRef)
+    return false;
+  if (FunRef->getName().equals("_swift_stdlib_operatingSystemVersion"))
+    return true;
+  return false;
+}
+
 /// Collect generic alloc_stack instructions in the current function can be
 /// hoisted.
 /// We can hoist generic alloc_stack instructions if they are not dependent on a
@@ -349,11 +363,9 @@ void HoistAllocStack::collectHoistableInstructions() {
         continue;
       }
       // Don't perform alloc_stack hoisting in functions with availability.
-      if (auto *Apply = dyn_cast<ApplyInst>(&Inst)) {
-        if (Apply->hasSemantics("availability.osversion")) {
-          AllocStackToHoist.clear();
-          return;
-        }
+      if (indicatesDynamicAvailabilityCheckUse(&Inst)) {
+        AllocStackToHoist.clear();
+        return;
       }
       auto *ASI = dyn_cast<AllocStackInst>(&Inst);
       if (!ASI) {

stdlib/public/core/Availability.swift

@@ -17,17 +17,17 @@ import SwiftShims
 ///
 /// This is a magic entry point known to the compiler. It is called in
 /// generated code for API availability checking.
-/// Note: It is important not to make this function inlinable. There is a pass
-/// that relies on being able to tell whether this function is called. It does
-/// this using the semantics attribute.
 @_semantics("availability.osversion")
-@inline(never)
+@inlinable
 public func _stdlib_isOSVersionAtLeast(
   _ major: Builtin.Word,
   _ minor: Builtin.Word,
   _ patch: Builtin.Word
 ) -> Builtin.Int1 {
 #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
+  // The call to _swift_stdlib_operatingSystemVersion is used as an indicator
+  // that this function was called by a compiler optimization pass. If it is
+  // replaced that pass needs to be updated.
   let runningVersion = _swift_stdlib_operatingSystemVersion()
   let queryVersion = _SwiftNSOperatingSystemVersion(
     majorVersion: Int(major),

test/IRGen/availability.swift

@@ -1,5 +1,5 @@
 // RUN: %target-swift-frontend -assume-parsing-unqualified-ownership-sil -primary-file %s -emit-ir | %FileCheck %s
-// RUN: %target-swift-frontend -assume-parsing-unqualified-ownership-sil -primary-file %s -O -emit-ir | %FileCheck %s
+// RUN: %target-swift-frontend -assume-parsing-unqualified-ownership-sil -primary-file %s -O -emit-ir | %FileCheck %s --check-prefix=OPT
 
 // REQUIRES: objc_interop
 
@@ -13,6 +13,11 @@ import Foundation
 // CHECK: call swiftcc i1 @"$Ss26_stdlib_isOSVersionAtLeastyBi1_Bw_BwBwtF"(
 // CHECK: S10Foundation11MeasurementVySo17NSUnitTemperature
 
+// OPT-LABEL: define{{.*}} @{{.*}}dontHoist
+// OPT-NOT: S10Foundation11MeasurementVySo17NSUnitTemperature
+// OPT: call {{.*}} @_swift_stdlib_operatingSystemVersion(
+// OPT: S10Foundation11MeasurementVySo17NSUnitTemperature
+
 public func dontHoist() {
   if #available(OSX 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *) {
       let measurement = Measurement<UnitTemperature>(value: Double(42), unit: .celsius)