[Frontend] Infer simulator environment in the frontend, too.

Some code paths that see target triples go through the frontend
without seeing the driver. Therefore, perform the same "simulator"
inference for x86 iOS/tvOS/watchOS triples also in the frontend,
to ensure that we remain compatible. Also make sure that
-print-target-info performs the appropriate adjustment.

Author: DougGregor

include/swift/AST/DiagnosticsDriver.def

@@ -84,9 +84,6 @@ ERROR(error_unexpected_input_file,none,
 
 ERROR(error_unknown_target,none,
       "unknown target '%0'", (StringRef))
-WARNING(warning_inferred_simulator_target,none,
-      "inferring simulator environment for target '%0'; "
-      "use '-target %1' instead", (StringRef, StringRef))
 
 ERROR(error_framework_bridging_header,none,
       "using bridging headers with framework targets is unsupported", ())

include/swift/AST/DiagnosticsFrontend.def

@@ -61,6 +61,10 @@ ERROR(error_unsupported_target_arch, none,
 ERROR(error_unsupported_opt_for_target, none,
       "unsupported option '%0' for target '%1'", (StringRef, StringRef))
 
+WARNING(warning_inferred_simulator_target,none,
+      "inferring simulator environment for target '%0'; "
+      "use '-target %1' instead", (StringRef, StringRef))
+
 ERROR(error_argument_not_allowed_with, none,
       "argument '%0' is not allowed with '%1'", (StringRef, StringRef))
 

include/swift/Basic/Platform.h

@@ -46,6 +46,9 @@ namespace swift {
   /// Returns true if the given triple represents a macCatalyst environment.
   bool tripleIsMacCatalystEnvironment(const llvm::Triple &triple);
 
+  /// Determine whether the triple infers the "simulator" environment.
+  bool tripleInfersSimulatorEnvironment(const llvm::Triple &triple);
+
   /// Returns true if the given -target triple and -target-variant triple
   /// can be zippered.
   bool triplesAreValidForZippering(const llvm::Triple &target,

lib/Basic/Platform.cpp

@@ -37,6 +37,21 @@ bool swift::tripleIsMacCatalystEnvironment(const llvm::Triple &triple) {
       triple.getEnvironment() == llvm::Triple::MacABI;
 }
 
+bool swift::tripleInfersSimulatorEnvironment(const llvm::Triple &triple) {
+  switch (triple.getOS()) {
+  case llvm::Triple::IOS:
+  case llvm::Triple::TvOS:
+  case llvm::Triple::WatchOS:
+    return !triple.isSimulatorEnvironment() &&
+        (triple.getArch() == llvm::Triple::x86 ||
+         triple.getArch() == llvm::Triple::x86_64) &&
+        !tripleIsMacCatalystEnvironment(triple);
+
+  default:
+    return false;
+  }
+}
+
 bool swift::triplesAreValidForZippering(const llvm::Triple &target,
                                         const llvm::Triple &targetVariant) {
   // The arch and vendor must match.

lib/Driver/Driver.cpp

@@ -270,27 +270,23 @@ Driver::buildToolChain(const llvm::opt::InputArgList &ArgList) {
 
   llvm::Triple target(DefaultTargetTriple);
 
+  // Backward compatibility hack: infer "simulator" environment for x86
+  // iOS/tvOS/watchOS.
+  if (tripleInfersSimulatorEnvironment(target)) {
+    // Set the simulator environment.
+    target.setEnvironment(llvm::Triple::EnvironmentType::Simulator);
+
+    auto newTargetTriple = target.normalize();
+    Diags.diagnose(SourceLoc(), diag::warning_inferred_simulator_target,
+                   DefaultTargetTriple, newTargetTriple);
+
+    DefaultTargetTriple = newTargetTriple;
+  }
+
   switch (target.getOS()) {
   case llvm::Triple::IOS:
   case llvm::Triple::TvOS:
   case llvm::Triple::WatchOS:
-    // Backward compatibility hack: infer "simulator" environment for x86
-    // iOS/tvOS/watchOS.
-    if (!target.isSimulatorEnvironment() &&
-        (target.getArch() == llvm::Triple::x86 ||
-         target.getArch() == llvm::Triple::x86_64) &&
-        !tripleIsMacCatalystEnvironment(target)) {
-      // Set the simulator environment.
-      target.setEnvironment(llvm::Triple::EnvironmentType::Simulator);
-
-      auto newTargetTriple = target.normalize();
-      Diags.diagnose(SourceLoc(), diag::warning_inferred_simulator_target,
-                     DefaultTargetTriple, newTargetTriple);
-
-      DefaultTargetTriple = newTargetTriple;
-    }
-    LLVM_FALLTHROUGH;
-
   case llvm::Triple::Darwin:
   case llvm::Triple::MacOSX: {
     Optional<llvm::Triple> targetVariant;

lib/Frontend/CompilerInvocation.cpp

@@ -553,9 +553,22 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   llvm::Triple Target = Opts.Target;
   StringRef TargetArg;
+  std::string TargetArgScratch;
+
   if (const Arg *A = Args.getLastArg(OPT_target)) {
     Target = llvm::Triple(A->getValue());
     TargetArg = A->getValue();
+
+    // Backward compatibility hack: infer "simulator" environment for x86
+    // iOS/tvOS/watchOS. The driver takes care of this for the frontend
+    // most of the time, but loading of old .swiftinterface files goes
+    // directly to the frontend.
+    if (tripleInfersSimulatorEnvironment(Target)) {
+      // Set the simulator environment.
+      Target.setEnvironment(llvm::Triple::EnvironmentType::Simulator);
+      TargetArgScratch = Target.str();
+      TargetArg = TargetArgScratch;
+    }
   }
 
   if (const Arg *A = Args.getLastArg(OPT_target_variant)) {

test/Driver/print_target_info.swift

@@ -7,6 +7,8 @@
 // RUN: %swift_driver -print-target-info -target x86_64-apple-macosx10.15 -target-variant x86_64-apple-ios13-macabi | %FileCheck -check-prefix CHECK-ZIPPERED %s
 // RUN: %target-swift-frontend -print-target-info -target x86_64-apple-macosx10.15 -target-variant x86_64-apple-ios13-macabi | %FileCheck -check-prefix CHECK-ZIPPERED %s
 
+// RUN: %swift_driver -print-target-info -target x86_64-apple-ios12.0 | %FileCheck -check-prefix CHECK-IOS-SIM %s
+
 // CHECK-IOS:   "target": {
 // CHECK-IOS:     "triple": "arm64-apple-ios12.0",
 // CHECK-IOS:     "unversionedTriple": "arm64-apple-ios",
@@ -50,3 +52,11 @@
 // CHECK-ZIPPERED:   "swiftRuntimeCompatibilityVersion": "5.1"
 // CHECK-ZIPPERED:   "librariesRequireRPath": false
 // CHECK-ZIPPERED: }
+
+// CHECK-IOS-SIM:   "target": {
+// CHECK-IOS-SIM:     "triple": "x86_64-apple-ios12.0-simulator",
+// CHECK-IOS-SIM:     "unversionedTriple": "x86_64-apple-ios-simulator",
+// CHECK-IOS-SIM:     "moduleTriple": "x86_64-apple-ios-simulator",
+// CHECK-IOS-SIM:     "swiftRuntimeCompatibilityVersion": "5.0",
+// CHECK-IOS-SIM:     "librariesRequireRPath": true
+// CHECK-IOS-SIM:   }