Add Builtin.print_disabled()

include/swift/AST/Builtins.def

@@ -642,6 +642,9 @@ BUILTIN_MISC_OPERATION(StaticReport, "staticReport", "", Special)
 /// Returns the selected assertion configuration.
 BUILTIN_MISC_OPERATION(AssertConf, "assert_configuration", "n", Special)
 
+/// PrintDisabled has type () -> Bool
+BUILTIN_MISC_OPERATION(PrintDisabled, "print_disabled", "n", Special)
+
 /// StringObjectOr has type (T,T) -> T.
 /// Sets bits in a string object. The first operand is bit-cast string literal
 /// pointer to an integer. The second operand is the bit mask to be or'd into

include/swift/AST/SILOptions.h

@@ -127,6 +127,15 @@ class SILOptions {
   /// The assert configuration controls how assertions behave.
   unsigned AssertConfig = Debug;
 
+  enum PrintConfiguration: unsigned {
+    // Used by stdlib code to tell whether client is built with -disable-print
+    Normal = 0,
+    Disabled = 1,
+  };
+
+  /// The print configuration how printing from stdlib should behave.
+  unsigned PrintConfig = Normal;
+
   /// Should we print out instruction counts if -print-stats is passed in?
   bool PrintInstCounts = false;
 

include/swift/Option/FrontendOptions.td

@@ -446,6 +446,10 @@ def enable_experimental_static_assert :
   Flag<["-"], "enable-experimental-static-assert">,
   HelpText<"Enable experimental #assert">;
 
+def experimental_disable_print : Flag<["-"], "experimental-disable-print">,
+  Flags<[FrontendOption, HelpHidden]>,
+  HelpText<"Turn print() calls into no-ops.">;
+
 def enable_experimental_named_opaque_types :
   Flag<["-"], "enable-experimental-named-opaque-types">,
   HelpText<"Enable experimental support for named opaque result types">;

include/swift/SILOptimizer/Utils/ConstantFolding.h

@@ -64,6 +64,9 @@ class ConstantFolder {
   /// The assert configuration of SILOptions.
   unsigned AssertConfiguration;
 
+  /// The print configuration of SILOptions.
+  unsigned PrintConfiguration;
+
   /// Print diagnostics as part of mandatory constant propagation.
   bool EnableDiagnostics;
 
@@ -79,11 +82,13 @@ class ConstantFolder {
   /// \param Callback Called for each constant folded instruction.
   ConstantFolder(SILOptFunctionBuilder &FuncBuilder,
                  unsigned AssertConfiguration,
+                 unsigned PrintConfiguration,
                  bool EnableDiagnostics = false,
                  std::function<void (SILInstruction *)> Callback =
                  [](SILInstruction *){}) :
     FuncBuilder(FuncBuilder),
     AssertConfiguration(AssertConfiguration),
+    PrintConfiguration(PrintConfiguration),
     EnableDiagnostics(EnableDiagnostics),
     Callback(Callback) { }
 

lib/AST/Builtins.cpp

@@ -1682,6 +1682,12 @@ static ValueDecl *getAssertConfOperation(ASTContext &C, Identifier Id) {
   return getBuiltinFunction(Id, {}, Int32Ty);
 }
 
+static ValueDecl *getPrintDisabledOperation(ASTContext &C, Identifier Id) {
+  // () -> Int1
+  auto Int1Ty = BuiltinIntegerType::get(1, C);
+  return getBuiltinFunction(Id, {}, Int1Ty);
+}
+
 static ValueDecl *getFixLifetimeOperation(ASTContext &C, Identifier Id) {
   // <T> T -> ()
   BuiltinFunctionBuilder builder(C);
@@ -2675,6 +2681,9 @@ ValueDecl *swift::getBuiltinValueDecl(ASTContext &Context, Identifier Id) {
 
   case BuiltinValueKind::AssertConf:
     return getAssertConfOperation(Context, Id);
+
+  case BuiltinValueKind::PrintDisabled:
+    return getPrintDisabledOperation(Context, Id);
 
   case BuiltinValueKind::FixLifetime:
     return getFixLifetimeOperation(Context, Id);

lib/Frontend/CompilerInvocation.cpp

@@ -1397,6 +1397,13 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
         (IRGenOpts.shouldOptimize() ? SILOptions::Release : SILOptions::Debug);
   }
 
+  Opts.PrintConfig = Args.hasArg(OPT_experimental_disable_print)
+                         ? SILOptions::Disabled
+                         : SILOptions::Normal;
+  if (FEOpts.ParseStdlib) {
+    Opts.PrintConfig = SILOptions::DisableReplacement;
+  }
+
   // -Ounchecked might also set removal of runtime asserts (cond_fail).
   Opts.RemoveRuntimeAsserts |= Args.hasArg(OPT_RemoveRuntimeAsserts);
 

lib/IRGen/GenBuiltin.cpp

@@ -1087,6 +1087,10 @@ if (Builtin.ID == BuiltinValueKind::id) { \
     out.add(DebugAssert);
     return;
   }
+
+  if (Builtin.ID == BuiltinValueKind::PrintDisabled) {
+    llvm_unreachable("PrintDisabled not constant folded");
+  }
 
   if (Builtin.ID == BuiltinValueKind::DestroyArray) {
     // The input type is (T.Type, Builtin.RawPointer, Builtin.Word).

lib/SIL/IR/OperandOwnership.cpp

@@ -641,6 +641,7 @@ BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, AllocRaw)
 BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, And)
 BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, GenericAnd)
 BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, AssertConf)
+BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, PrintDisabled)
 BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, AssignCopyArrayNoAlias)
 BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, AssignCopyArrayFrontToBack)
 BUILTIN_OPERAND_OWNERSHIP(InstantaneousUse, AssignCopyArrayBackToFront)

lib/SIL/IR/ValueOwnership.cpp

@@ -486,6 +486,7 @@ CONSTANT_OWNERSHIP_BUILTIN(None, IsSameMetatype)
 CONSTANT_OWNERSHIP_BUILTIN(None, Alignof)
 CONSTANT_OWNERSHIP_BUILTIN(None, AllocRaw)
 CONSTANT_OWNERSHIP_BUILTIN(None, AssertConf)
+CONSTANT_OWNERSHIP_BUILTIN(None, PrintDisabled)
 CONSTANT_OWNERSHIP_BUILTIN(None, UToSCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(None, SToSCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(None, SToUCheckedTrunc)

lib/SILOptimizer/IPO/GlobalOpt.cpp

@@ -409,7 +409,8 @@ replaceLoadsByKnownValue(SILFunction *InitF, SILGlobalVariable *SILG,
     // constant, e.g.
     //    let a = 1
     //    let b = a + 1
-    ConstantFolder constFolder(FunctionBuilder, PM->getOptions().AssertConfig);
+    ConstantFolder constFolder(FunctionBuilder, PM->getOptions().AssertConfig,
+                               PM->getOptions().PrintConfig);
     for (SILInstruction *inst : insertedInsts) {
       constFolder.addToWorklist(inst);
     }

lib/SILOptimizer/Mandatory/ConstantPropagation.cpp

@@ -35,7 +35,7 @@ class ConstantPropagation : public SILFunctionTransform {
   void run() override {
     SILOptFunctionBuilder FuncBuilder(*this);
     ConstantFolder Folder(FuncBuilder, getOptions().AssertConfig,
-                          EnableDiagnostics);
+                          getOptions().PrintConfig, EnableDiagnostics);
     Folder.initializeWorklist(*getFunction());
     auto Invalidation = Folder.processWorkList();
 

lib/SILOptimizer/Transforms/AccessEnforcementReleaseSinking.cpp

@@ -123,6 +123,7 @@ static bool isBarrier(SILInstruction *inst) {
     case BuiltinValueKind::ShuffleVector:
     case BuiltinValueKind::StaticReport:
     case BuiltinValueKind::AssertConf:
+    case BuiltinValueKind::PrintDisabled:
     case BuiltinValueKind::StringObjectOr:
     case BuiltinValueKind::UToSCheckedTrunc:
     case BuiltinValueKind::SToUCheckedTrunc:

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -138,6 +138,7 @@ class SimplifyCFG {
               bool EnableJumpThread)
       : FuncBuilder(T), Fn(Fn), PM(T.getPassManager()),
         ConstFolder(FuncBuilder, PM->getOptions().AssertConfig,
+                    PM->getOptions().PrintConfig,
                     /* EnableDiagnostics */ false,
                     [&](SILInstruction *I) { constFoldingCallback(I); }),
         ShouldVerify(Verify), EnableJumpThread(EnableJumpThread) {}

lib/SILOptimizer/Utils/ConstantFolding.cpp

@@ -1152,6 +1152,15 @@ static SILValue constantFoldIsConcrete(BuiltinInst *BI) {
   return inst;
 }
 
+static SILValue constantFoldPrintDisabled(BuiltinInst *BI, bool PrintDisabled) {
+  SILBuilderWithScope builder(BI);
+  auto *inst = builder.createIntegerLiteral(
+      BI->getLoc(), SILType::getBuiltinIntegerType(1, builder.getASTContext()),
+      PrintDisabled);
+  BI->replaceAllUsesWith(inst);
+  return inst;
+}
+
 static SILValue constantFoldBuiltin(BuiltinInst *BI,
                                     Optional<bool> &ResultsInError) {
   const IntrinsicInfo &Intrinsic = BI->getIntrinsicInfo();
@@ -1569,7 +1578,8 @@ void ConstantFolder::initializeWorklist(SILFunction &f) {
       }
 
       if (isApplyOfBuiltin(*inst, BuiltinValueKind::GlobalStringTablePointer) ||
-          isApplyOfBuiltin(*inst, BuiltinValueKind::IsConcrete)) {
+          isApplyOfBuiltin(*inst, BuiltinValueKind::IsConcrete) ||
+          isApplyOfBuiltin(*inst, BuiltinValueKind::PrintDisabled)) {
         WorkList.insert(inst);
         continue;
       }
@@ -1779,7 +1789,7 @@ ConstantFolder::processWorkList() {
     if (isApplyOfBuiltin(*I, BuiltinValueKind::GlobalStringTablePointer)) {
       if (constantFoldGlobalStringTablePointerBuiltin(cast<BuiltinInst>(I),
                                                       EnableDiagnostics)) {
-        // Here, the bulitin instruction got folded, so clean it up.
+        // Here, the builtin instruction got folded, so clean it up.
         eliminateDeadInstruction(I, callbacks);
       }
       continue;
@@ -1804,13 +1814,25 @@ ConstantFolder::processWorkList() {
 
     if (isApplyOfBuiltin(*I, BuiltinValueKind::IsConcrete)) {
       if (constantFoldIsConcrete(cast<BuiltinInst>(I))) {
-        // Here, the bulitin instruction got folded, so clean it up.
+        // Here, the builtin instruction got folded, so clean it up.
         recursivelyDeleteTriviallyDeadInstructions(I, /*force*/ true,
                                                    callbacks);
       }
       continue;
     }
 
+    if (PrintConfiguration != SILOptions::DisableReplacement) {
+      if (isApplyOfBuiltin(*I, BuiltinValueKind::PrintDisabled)) {
+        if (constantFoldPrintDisabled(cast<BuiltinInst>(I),
+                                      PrintConfiguration ==
+                                          SILOptions::Disabled)) {
+          // Here, the builtin instruction got folded, so clean it up.
+          eliminateDeadInstruction(I, callbacks);
+        }
+        continue;
+      }
+    }
+
     if (auto *bi = dyn_cast<BuiltinInst>(I)) {
       if (auto kind = bi->getBuiltinKind()) {
         if (SILValue v = specializePolymorphicBuiltin(bi, kind.getValue())) {

stdlib/public/core/Builtin.swift

@@ -768,6 +768,19 @@ func _trueAfterDiagnostics() -> Builtin.Int1 {
   return true._value
 }
 
+/// Whether client code is built with -print-disabled.
+@_alwaysEmitIntoClient
+private func _isPrintingDisabled() -> Bool {
+  return Bool(Builtin.print_disabled())
+}
+
+// For testing only.
+@_alwaysEmitIntoClient
+private func _customPrint(_ s: String) {
+  if _isPrintingDisabled() { return }
+  print(s)
+}
+
 /// Returns the dynamic type of a value.
 ///
 /// You can use the `type(of:)` function to find the dynamic type of a value,

test/stdlib/print-disabled.swift

@@ -0,0 +1,25 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Release -O
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/ReleasePrintDisabled -O -disable-print
+// RUN: %target-run %t/Release | %FileCheck %s
+// RUN: %target-run %t/ReleasePrintDisabled | %FileCheck %s --check-prefix CHECK-PRINT-DISABLED
+
+// REQUIRES: executable_test
+
+#if canImport(Darwin)
+import Darwin
+#elseif canImport(Glibc)
+import Glibc
+#elseif os(Windows)
+import CRT
+import WinSDK
+#endif
+
+puts("Start\n")
+_customPrint("Hello world!")
+
+// CHECK: Start
+// CHECK: Hello world!
+
+// CHECK-PRINT-DISABLED: Start
+// CHECK-PRINT-DISABLED-NOT: Hello world!