Better runtime failure messages (not yet enabled by default)

docs/SIL.rst

@@ -5110,13 +5110,15 @@ cond_fail
 `````````
 ::
 
-  sil-instruction ::= 'cond_fail' sil-operand
+  sil-instruction ::= 'cond_fail' sil-operand, string-literal
 
-  cond_fail %0 : $Builtin.Int1
+  cond_fail %0 : $Builtin.Int1, "failure reason"
   // %0 must be of type $Builtin.Int1
 
 This instruction produces a `runtime failure`_ if the operand is one.
 Execution proceeds normally if the operand is zero.
+The second operand is a static failure message, which is displayed by the
+debugger in case the failure is triggered.
 
 Terminators
 ~~~~~~~~~~~

include/swift/AST/Builtins.def

@@ -314,10 +314,6 @@ BUILTIN_SIL_OPERATION(BeginUnpairedModifyAccess, "beginUnpairedModifyAccess",
 /// be a pointer to an UnsafeValueBuffer that records an in progress access.
 BUILTIN_SIL_OPERATION(EndUnpairedAccess, "endUnpairedAccess", Special)
 
-/// condfail(Int1) -> ()
-/// Triggers a runtime failure if the condition is true.
-BUILTIN_SIL_OPERATION(CondFail, "condfail", Special)
-
 /// fixLifetime(T) -> ()
 /// Fixes the lifetime of any heap references in a value.
 BUILTIN_SIL_OPERATION(FixLifetime, "fixLifetime", Special)
@@ -404,6 +400,10 @@ BUILTIN_RUNTIME_CALL(IsOptionalType, "isOptional", "")
           BUILTIN(Id, Name, Attrs)
 #endif
 
+/// condfail(Int1, RawPointer) -> ()
+/// Triggers a runtime failure if the condition is true.
+BUILTIN_MISC_OPERATION(CondFail, "condfail", "", Special)
+
 /// Sizeof has type T.Type -> Int
 BUILTIN_MISC_OPERATION(Sizeof, "sizeof", "n", Special)
 

include/swift/SIL/SILBuilder.h

@@ -1775,15 +1775,15 @@ class SILBuilder {
   //===--------------------------------------------------------------------===//
 
   CondFailInst *createCondFail(SILLocation Loc, SILValue Operand,
-                               bool Inverted = false) {
+                               StringRef Message, bool Inverted = false) {
     if (Inverted) {
       SILType Ty = Operand->getType();
       SILValue True(createIntegerLiteral(Loc, Ty, 1));
       Operand =
           createBuiltinBinaryFunction(Loc, "xor", Ty, Ty, {Operand, True});
     }
-    return insert(new (getModule())
-                      CondFailInst(getSILDebugLocation(Loc), Operand));
+    return insert(CondFailInst::create(getSILDebugLocation(Loc), Operand,
+                                       Message, getModule()));
   }
 
   BuiltinInst *createBuiltinTrap(SILLocation Loc) {

include/swift/SIL/SILCloner.h

@@ -2447,7 +2447,8 @@ SILCloner<ImplClass>::visitCondFailInst(CondFailInst *Inst) {
   getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
   recordClonedInstruction(
       Inst, getBuilder().createCondFail(getOpLocation(Inst->getLoc()),
-                                        getOpValue(Inst->getOperand())));
+                                        getOpValue(Inst->getOperand()),
+                                        Inst->getMessage()));
 }
 
 template<typename ImplClass>

include/swift/SIL/SILInstruction.h

@@ -6715,14 +6715,28 @@ class ProjectExistentialBoxInst
 //===----------------------------------------------------------------------===//
 
 /// Trigger a runtime failure if the given Int1 value is true.
-class CondFailInst
+///
+/// Optionally cond_fail has a static failure message, which is displayed in the debugger in case the failure
+/// is triggered.
+class CondFailInst final
     : public UnaryInstructionBase<SILInstructionKind::CondFailInst,
-                                  NonValueInstruction>
+                                  NonValueInstruction>,
+      private llvm::TrailingObjects<CondFailInst, char>
 {
+  friend TrailingObjects;
   friend SILBuilder;
 
-  CondFailInst(SILDebugLocation DebugLoc, SILValue Operand)
-      : UnaryInstructionBase(DebugLoc, Operand) {}
+  unsigned MessageSize;
+
+  CondFailInst(SILDebugLocation DebugLoc, SILValue Operand, StringRef Message);
+
+  static CondFailInst *create(SILDebugLocation DebugLoc, SILValue Operand,
+                              StringRef Message, SILModule &M);
+
+public:
+  StringRef getMessage() const {
+    return {getTrailingObjects<char>(), MessageSize};
+  }
 };
 
 //===----------------------------------------------------------------------===//

include/swift/Serialization/ModuleFormat.h

@@ -52,7 +52,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 500; // dependency types for protocols
+const uint16_t SWIFTMODULE_VERSION_MINOR = 501; // cond_fail messages
 
 using DeclIDField = BCFixed<31>;
 

lib/AST/Builtins.cpp

@@ -1037,8 +1037,9 @@ static ValueDecl *getCanBeObjCClassOperation(ASTContext &Context,
 static ValueDecl *getCondFailOperation(ASTContext &C, Identifier Id) {
   // Int1 -> ()
   auto CondTy = BuiltinIntegerType::get(1, C);
+  auto MsgTy = C.TheRawPointerType;
   auto VoidTy = TupleType::getEmpty(C);
-  return getBuiltinFunction(Id, {CondTy}, VoidTy);
+  return getBuiltinFunction(Id, {CondTy, MsgTy}, VoidTy);
 }
 
 static ValueDecl *getAssertConfOperation(ASTContext &C, Identifier Id) {

lib/IRGen/GenBuiltin.cpp

@@ -204,7 +204,7 @@ void irgen::emitBuiltinCall(IRGenFunction &IGF, const BuiltinInfo &Builtin,
 
   // Emit non-mergeable traps only.
   if (IGF.Builder.isTrapIntrinsic(IID)) {
-    IGF.Builder.CreateNonMergeableTrap(IGF.IGM);
+    IGF.Builder.CreateNonMergeableTrap(IGF.IGM, StringRef());
     return;
   }
 
@@ -359,7 +359,8 @@ if (Builtin.ID == BuiltinValueKind::id) { \
     // string literal. If we ever get to the point of executing this builtin
     // at run time, it implies an incorrect use of the builtin and must result
     // in a trap.
-    IGF.emitTrap(/*Unreachable=*/false);
+    IGF.emitTrap("invalid use of globalStringTablePointer",
+                 /*Unreachable=*/false);
     auto returnValue = llvm::UndefValue::get(IGF.IGM.Int8PtrTy);
     // Consume the arguments of the builtin.
     (void)args.claimAll();

lib/IRGen/GenCast.cpp

@@ -469,7 +469,7 @@ emitExistentialScalarCastFn(IRGenModule &IGM,
   }
 
   case CheckedCastMode::Unconditional: {
-    IGF.emitTrap(/*EmitUnreachable=*/true);
+    IGF.emitTrap("type cast failed", /*EmitUnreachable=*/true);
     break;
   }
   }

lib/IRGen/IRBuilder.h

@@ -307,7 +307,7 @@ class IRBuilder : public IRBuilderBase {
   /// Call the trap intrinsic. If optimizations are enabled, an inline asm
   /// gadget is emitted before the trap. The gadget inhibits transforms which
   /// merge trap calls together, which makes debugging crashes easier.
-  llvm::CallInst *CreateNonMergeableTrap(IRGenModule &IGM);
+  llvm::CallInst *CreateNonMergeableTrap(IRGenModule &IGM, StringRef failureMsg);
 
   /// Split a first-class aggregate value into its component pieces.
   template <unsigned N>

lib/IRGen/IRGenDebugInfo.cpp

@@ -148,6 +148,9 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
 
   void setCurrentLoc(IRBuilder &Builder, const SILDebugScope *DS,
                      SILLocation Loc);
+
+  void addFailureMessageToCurrentLoc(IRBuilder &Builder, StringRef failureMsg);
+
   void clearLoc(IRBuilder &Builder);
   void pushLoc();
   void popLoc();
@@ -1828,7 +1831,37 @@ void IRGenDebugInfoImpl::setCurrentLoc(IRBuilder &Builder,
   auto DL = llvm::DebugLoc::get(L.Line, L.Column, Scope, InlinedAt);
   Builder.SetCurrentDebugLocation(DL);
 }
+
+void IRGenDebugInfoImpl::addFailureMessageToCurrentLoc(IRBuilder &Builder,
+                                                       StringRef failureMsg) {
+  auto TrapLoc = Builder.getCurrentDebugLocation();
+
+  // Create a function in the debug info which has failureMsg as name.
+  // TrapSc is the SIL debug scope which corresponds to TrapSP in the LLVM debug
+  // info.
+  RegularLocation ALoc = RegularLocation::getAutoGeneratedLocation();
+  const SILDebugScope *TrapSc = new (IGM.getSILModule()) SILDebugScope(ALoc);
+
+  llvm::DISubroutineType *DIFnTy = DBuilder.createSubroutineType(nullptr);
+
+  std::string FuncName = "Swift runtime failure: ";
+  FuncName += failureMsg;
+
+  llvm::DISubprogram *TrapSP = DBuilder.createFunction(
+     MainModule, StringRef(), FuncName, TrapLoc->getFile(), 0, DIFnTy, 0,
+     llvm::DINode::FlagArtificial, llvm::DISubprogram::SPFlagDefinition,
+     nullptr, nullptr, nullptr);
 
+  ScopeCache[TrapSc] = llvm::TrackingMDNodeRef(TrapSP);
+  LastScope = TrapSc;
+
+  assert(parentScopesAreSane(TrapSc) && "parent scope sanity check failed");
+
+  // Wrap the existing TrapLoc into the failure function.
+  auto DL = llvm::DebugLoc::get(0, 0, TrapSP, TrapLoc);
+  Builder.SetCurrentDebugLocation(DL);
+}
+
 void IRGenDebugInfoImpl::clearLoc(IRBuilder &Builder) {
   LastDebugLoc = {};
   LastScope = nullptr;
@@ -2320,6 +2353,12 @@ void IRGenDebugInfo::setCurrentLoc(IRBuilder &Builder, const SILDebugScope *DS,
   static_cast<IRGenDebugInfoImpl *>(this)->setCurrentLoc(Builder, DS, Loc);
 }
 
+void IRGenDebugInfo::addFailureMessageToCurrentLoc(IRBuilder &Builder,
+                                                   StringRef failureMsg) {
+  static_cast<IRGenDebugInfoImpl *>(this)->
+    addFailureMessageToCurrentLoc(Builder, failureMsg);
+}
+
 void IRGenDebugInfo::clearLoc(IRBuilder &Builder) {
   static_cast<IRGenDebugInfoImpl *>(this)->clearLoc(Builder);
 }

lib/IRGen/IRGenDebugInfo.h

@@ -59,6 +59,12 @@ class IRGenDebugInfo {
   void setCurrentLoc(IRBuilder &Builder, const SILDebugScope *DS,
                      SILLocation Loc);
 
+  /// Replace the current debug location in \p Builder with the same location, but contained in an
+  /// inlined function which is named like \p failureMsg.
+  ///
+  /// This lets the debugger display the \p failureMsg as an inlined function frame.
+  void addFailureMessageToCurrentLoc(IRBuilder &Builder, StringRef failureMsg);
+
   void clearLoc(IRBuilder &Builder);
 
   /// Push the current debug location onto a stack and initialize the

lib/IRGen/IRGenFunction.cpp

@@ -31,6 +31,10 @@
 using namespace swift;
 using namespace irgen;
 
+static llvm::cl::opt<bool> EnableTrapDebugInfo(
+    "enable-trap-debug-info", llvm::cl::Hidden,
+    llvm::cl::desc("Generate failure-message functions in the debug info"));
+
 IRGenFunction::IRGenFunction(IRGenModule &IGM, llvm::Function *Fn,
                              OptimizationMode OptMode,
                              const SILDebugScope *DbgScope,
@@ -432,7 +436,8 @@ Address IRGenFunction::emitAddressAtOffset(llvm::Value *base, Offset offset,
   return Address(slotPtr, objectAlignment);
 }
 
-llvm::CallInst *IRBuilder::CreateNonMergeableTrap(IRGenModule &IGM) {
+llvm::CallInst *IRBuilder::CreateNonMergeableTrap(IRGenModule &IGM,
+                                                  StringRef failureMsg) {
   if (IGM.IRGen.Opts.shouldOptimize()) {
     // Emit unique side-effecting inline asm calls in order to eliminate
     // the possibility that an LLVM optimization or code generation pass
@@ -452,13 +457,16 @@ llvm::CallInst *IRBuilder::CreateNonMergeableTrap(IRGenModule &IGM) {
   // Emit the trap instruction.
   llvm::Function *trapIntrinsic =
       llvm::Intrinsic::getDeclaration(&IGM.Module, llvm::Intrinsic::ID::trap);
+  if (EnableTrapDebugInfo && IGM.DebugInfo && !failureMsg.empty()) {
+    IGM.DebugInfo->addFailureMessageToCurrentLoc(*this, failureMsg);
+  }
   auto Call = IRBuilderBase::CreateCall(trapIntrinsic, {});
   setCallingConvUsingCallee(Call);
   return Call;
 }
 
-void IRGenFunction::emitTrap(bool EmitUnreachable) {
-  Builder.CreateNonMergeableTrap(IGM);
+void IRGenFunction::emitTrap(StringRef failureMessage, bool EmitUnreachable) {
+  Builder.CreateNonMergeableTrap(IGM, failureMessage);
   if (EmitUnreachable)
     Builder.CreateUnreachable();
 }

lib/IRGen/IRGenFunction.h

@@ -287,7 +287,7 @@ class IRGenFunction {
   void setDereferenceableLoad(llvm::LoadInst *load, unsigned size);
 
   /// Emit a non-mergeable trap call, optionally followed by a terminator.
-  void emitTrap(bool EmitUnreachable);
+  void emitTrap(StringRef failureMessage, bool EmitUnreachable);
 
 private:
   llvm::Instruction *AllocaIP;

lib/IRGen/IRGenSIL.cpp

@@ -3880,7 +3880,7 @@ static bool hasReferenceSemantics(IRGenSILFunction &IGF,
 static llvm::Value *emitIsUnique(IRGenSILFunction &IGF, SILValue operand,
                                  SourceLoc loc) {
   if (!hasReferenceSemantics(IGF, operand->getType())) {
-    IGF.emitTrap(/*EmitUnreachable=*/false);
+    IGF.emitTrap("isUnique called for a non-reference", /*EmitUnreachable=*/false);
     return llvm::UndefValue::get(IGF.IGM.Int1Ty);
   }
 
@@ -4540,7 +4540,7 @@ static void emitTrapAndUndefValue(IRGenSILFunction &IGF,
   IGF.FailBBs.push_back(failBB);
 
   IGF.Builder.emitBlock(failBB);
-  IGF.emitTrap(/*EmitUnreachable=*/true);
+  IGF.emitTrap("mismatching type layouts", /*EmitUnreachable=*/true);
 
   llvm::BasicBlock *contBB = llvm::BasicBlock::Create(IGF.IGM.getLLVMContext());
   IGF.Builder.emitBlock(contBB);
@@ -5441,7 +5441,7 @@ void IRGenSILFunction::visitCondFailInst(swift::CondFailInst *i) {
     // debug location. This is because zero is not an artificial line location
     // in CodeView.
     IGM.DebugInfo->setInlinedTrapLocation(Builder, i->getDebugScope());
-  emitTrap(/*EmitUnreachable=*/true);
+  emitTrap(i->getMessage(), /*EmitUnreachable=*/true);
   Builder.emitBlock(contBB);
   FailBBs.push_back(failBB);
 }

lib/ParseSIL/ParseSIL.cpp

@@ -2635,6 +2635,33 @@ bool SILParser::parseSILInstruction(SILBuilder &B) {
     break;
   }
 
+  case SILInstructionKind::CondFailInst: {
+
+    if (parseTypedValueRef(Val, B))
+      return true;
+
+    SmallVector<char, 128> stringBuffer;
+    StringRef message;
+    if (P.consumeIf(tok::comma)) {
+      // Parse the string.
+      if (P.Tok.getKind() != tok::string_literal) {
+        P.diagnose(P.Tok, diag::expected_tok_in_sil_instr, "string");
+        return true;
+      }
+      SmallVector<Lexer::StringSegment, 1> segments;
+      P.L->getStringLiteralSegments(P.Tok, segments);
+      assert(segments.size() == 1);
+
+      P.consumeToken(tok::string_literal);
+      message = P.L->getEncodedStringSegment(segments.front(), stringBuffer);
+    }
+    if (parseSILDebugLocation(InstLoc, B))
+      return true;
+
+    ResultVal = B.createCondFail(InstLoc, Val, message);
+    break;
+  }
+
   case SILInstructionKind::AllocValueBufferInst: {
     SILType Ty;
     if (parseSILType(Ty) ||
@@ -2887,7 +2914,6 @@ bool SILParser::parseSILInstruction(SILBuilder &B) {
     UNARY_INSTRUCTION(DestroyAddr)
     UNARY_INSTRUCTION(CopyValue)
     UNARY_INSTRUCTION(DestroyValue)
-    UNARY_INSTRUCTION(CondFail)
     UNARY_INSTRUCTION(EndBorrow)
     UNARY_INSTRUCTION(DestructureStruct)
     UNARY_INSTRUCTION(DestructureTuple)

lib/SIL/OperandOwnership.cpp

@@ -953,6 +953,7 @@ ANY_OWNERSHIP_BUILTIN(AtomicRMW)
 ANY_OWNERSHIP_BUILTIN(AtomicStore)
 ANY_OWNERSHIP_BUILTIN(BitCast)
 ANY_OWNERSHIP_BUILTIN(CanBeObjCClass)
+ANY_OWNERSHIP_BUILTIN(CondFail)
 ANY_OWNERSHIP_BUILTIN(CmpXChg)
 ANY_OWNERSHIP_BUILTIN(CondUnreachable)
 ANY_OWNERSHIP_BUILTIN(CopyArray)

lib/SIL/SILInstructions.cpp

@@ -773,6 +773,21 @@ StringLiteralInst *StringLiteralInst::create(SILDebugLocation Loc,
   return ::new (buf) StringLiteralInst(Loc, text, encoding, Ty);
 }
 
+CondFailInst::CondFailInst(SILDebugLocation DebugLoc, SILValue Operand,
+                           StringRef Message)
+      : UnaryInstructionBase(DebugLoc, Operand),
+        MessageSize(Message.size()) {
+  memcpy(getTrailingObjects<char>(), Message.data(), Message.size());
+}
+
+CondFailInst *CondFailInst::create(SILDebugLocation DebugLoc, SILValue Operand,
+                                   StringRef Message, SILModule &M) {
+
+  auto Size = totalSizeToAlloc<char>(Message.size());
+  auto Buffer = M.allocateInst(Size, alignof(CondFailInst));
+  return ::new (Buffer) CondFailInst(DebugLoc, Operand, Message);
+}
+
 uint64_t StringLiteralInst::getCodeUnitCount() {
   auto E = unsigned(Encoding::UTF16);
   if (SILInstruction::Bits.StringLiteralInst.TheEncoding == E)

lib/SIL/SILPrinter.cpp

@@ -1866,7 +1866,8 @@ class SILPrinter : public SILInstructionVisitor<SILPrinter> {
   }
 
   void visitCondFailInst(CondFailInst *FI) {
-    *this << getIDAndType(FI->getOperand());
+    *this << getIDAndType(FI->getOperand()) << ", "
+          << QuotedString(FI->getMessage());
   }
 
   void visitIndexAddrInst(IndexAddrInst *IAI) {

lib/SIL/ValueOwnership.cpp

@@ -378,6 +378,7 @@ CONSTANT_OWNERSHIP_BUILTIN(Any, And)
 CONSTANT_OWNERSHIP_BUILTIN(Any, AssumeNonNegative)
 CONSTANT_OWNERSHIP_BUILTIN(Any, AssumeTrue)
 CONSTANT_OWNERSHIP_BUILTIN(Any, BitCast)
+CONSTANT_OWNERSHIP_BUILTIN(Any, CondFail)
 CONSTANT_OWNERSHIP_BUILTIN(Any, ExactSDiv)
 CONSTANT_OWNERSHIP_BUILTIN(Any, ExactUDiv)
 CONSTANT_OWNERSHIP_BUILTIN(Any, FAdd)