Index: docs/LanguageExtensions.rst =================================================================== --- docs/LanguageExtensions.rst +++ docs/LanguageExtensions.rst @@ -1679,7 +1679,7 @@ errorcode_t security_critical_application(...) { unsigned x, y, result; ... - if (__builtin_umul_overflow(x, y, &result)) + if (__builtin_mul_overflow(x, y, &result)) return kErrorCodeHackers; ... use_multiply(result); @@ -1686,10 +1686,13 @@ ... } -A complete enumeration of the builtins are: +Clang provides the following checked arithmetic builtins: .. code-block:: c + bool __builtin_add_overflow (type1 x, type2 y, type3 *sum); + bool __builtin_sub_overflow (type1 x, type2 y, type3 *diff); + bool __builtin_mul_overflow (type1 x, type2 y, type3 *prod); bool __builtin_uadd_overflow (unsigned x, unsigned y, unsigned *sum); bool __builtin_uaddl_overflow (unsigned long x, unsigned long y, unsigned long *sum); bool __builtin_uaddll_overflow(unsigned long long x, unsigned long long y, unsigned long long *sum); @@ -1709,7 +1712,17 @@ bool __builtin_smull_overflow (long x, long y, long *prod); bool __builtin_smulll_overflow(long long x, long long y, long long *prod); +Each builtin performs the specified mathematical operation on the +first two arguments and stores the result in the third argument. If +possible, the result will be equal to mathematically-correct result +and the builtin will return 0. Otherwise, the builtin will return +1 and the result will be equal to the unique value that is equivalent +to the mathematically-correct result modulo two raised to the *k* +power, where *k* is the number of bits in the result type. The +behavior of these builtins is well-defined for all argument values. +The first three builtins can operate on any integer types (including booleans). + .. _langext-__c11_atomic: __c11_atomic builtins Index: include/clang/Basic/Builtins.def =================================================================== --- include/clang/Basic/Builtins.def +++ include/clang/Basic/Builtins.def @@ -1217,6 +1217,9 @@ BUILTIN(__builtin_subcll, "ULLiULLiCULLiCULLiCULLi*", "n") // Checked Arithmetic Builtins for Security. +BUILTIN(__builtin_add_overflow, "v.", "nt") +BUILTIN(__builtin_sub_overflow, "v.", "nt") +BUILTIN(__builtin_mul_overflow, "v.", "nt") BUILTIN(__builtin_uadd_overflow, "bUiCUiCUi*", "n") BUILTIN(__builtin_uaddl_overflow, "bULiCULiCULi*", "n") BUILTIN(__builtin_uaddll_overflow, "bULLiCULLiCULLi*", "n") Index: include/clang/Basic/DiagnosticSemaKinds.td =================================================================== --- include/clang/Basic/DiagnosticSemaKinds.td +++ include/clang/Basic/DiagnosticSemaKinds.td @@ -6207,6 +6207,12 @@ "memory order argument to atomic operation is invalid">, InGroup>; +def err_overflow_builtin_must_be_int : Error< + "operand argument to overflow builtin must be an integer (%0 invalid)">; +def err_overflow_builtin_must_be_ptr_int : Error< + "result argument to overflow builtin must be a pointer " + "to a non-const integer (%0 invalid)">; + def err_atomic_load_store_uses_lib : Error< "atomic %select{load|store}0 requires runtime support that is not " "available for this target">; Index: lib/CodeGen/CGBuiltin.cpp =================================================================== --- lib/CodeGen/CGBuiltin.cpp +++ lib/CodeGen/CGBuiltin.cpp @@ -278,6 +278,50 @@ return CGF.Builder.CreateExtractValue(Tmp, 0); } +namespace { + struct WidthAndSignedness { + unsigned Width; + bool Signed; + }; +} + +static WidthAndSignedness +getIntegerWidthAndSignedness(const clang::ASTContext &context, + const clang::QualType Type) { + assert(Type->isIntegerType() && "Given type is not an integer."); + unsigned Width = Type->isBooleanType() ? 1 : context.getTypeInfo(Type).Width; + bool Signed = Type->isSignedIntegerType(); + return {Width, Signed}; +} + +// Given one or more integer types, this function produces an integer type that +// encompasses them: any value in one of the given types could be expressed in +// the encompassing type. +static struct WidthAndSignedness +EncompassingIntegerType(ArrayRef Types) { + assert(Types.size() > 0 && "Empty list of types."); + + // If any of the given types is signed, we must return a signed type. + bool Signed = false; + for (const auto &Type : Types) { + Signed |= Type.Signed; + } + + // The encompassing type must have a width greater than or equal to the width + // of the specified types. Aditionally, if the encompassing type is signed, + // its width must be strictly greater than the width of any unsigned types + // given. + unsigned Width = 0; + for (const auto &Type : Types) { + unsigned MinWidth = Type.Width + (Signed && !Type.Signed); + if (Width < MinWidth) { + Width = MinWidth; + } + } + + return {Width, Signed}; +} + Value *CodeGenFunction::EmitVAStartEnd(Value *ArgValue, bool IsStart) { llvm::Type *DestType = Int8PtrTy; if (ArgValue->getType() != DestType) @@ -1544,6 +1588,86 @@ Builder.CreateStore(CarryOut, CarryOutPtr); return RValue::get(Sum2); } + + case Builtin::BI__builtin_add_overflow: + case Builtin::BI__builtin_sub_overflow: + case Builtin::BI__builtin_mul_overflow: { + const clang::Expr *LeftArg = E->getArg(0); + const clang::Expr *RightArg = E->getArg(1); + const clang::Expr *ResultArg = E->getArg(2); + + clang::QualType ResultQTy = + ResultArg->getType()->castAs()->getPointeeType(); + + WidthAndSignedness LeftInfo = + getIntegerWidthAndSignedness(CGM.getContext(), LeftArg->getType()); + WidthAndSignedness RightInfo = + getIntegerWidthAndSignedness(CGM.getContext(), RightArg->getType()); + WidthAndSignedness ResultInfo = + getIntegerWidthAndSignedness(CGM.getContext(), ResultQTy); + WidthAndSignedness EncompassingInfo = + EncompassingIntegerType({LeftInfo, RightInfo, ResultInfo}); + + llvm::Type *EncompassingLLVMTy = + llvm::IntegerType::get(CGM.getLLVMContext(), EncompassingInfo.Width); + + llvm::Type *ResultLLVMTy = CGM.getTypes().ConvertType(ResultQTy); + + llvm::Intrinsic::ID IntrinsicId; + switch (BuiltinID) { + default: + llvm_unreachable("Unknown overflow builtin id."); + case Builtin::BI__builtin_add_overflow: + IntrinsicId = EncompassingInfo.Signed + ? llvm::Intrinsic::sadd_with_overflow + : llvm::Intrinsic::uadd_with_overflow; + break; + case Builtin::BI__builtin_sub_overflow: + IntrinsicId = EncompassingInfo.Signed + ? llvm::Intrinsic::ssub_with_overflow + : llvm::Intrinsic::usub_with_overflow; + break; + case Builtin::BI__builtin_mul_overflow: + IntrinsicId = EncompassingInfo.Signed + ? llvm::Intrinsic::smul_with_overflow + : llvm::Intrinsic::umul_with_overflow; + break; + } + + llvm::Value *Left = EmitScalarExpr(LeftArg); + llvm::Value *Right = EmitScalarExpr(RightArg); + Address ResultPtr = EmitPointerWithAlignment(ResultArg); + + // Extend each operand to the encompassing type. + Left = Builder.CreateIntCast(Left, EncompassingLLVMTy, LeftInfo.Signed); + Right = Builder.CreateIntCast(Right, EncompassingLLVMTy, RightInfo.Signed); + + // Perform the operation on the extended values. + llvm::Value *Overflow, *Result; + Result = EmitOverflowIntrinsic(*this, IntrinsicId, Left, Right, Overflow); + + if (EncompassingInfo.Width > ResultInfo.Width) { + // The encompassing type is wider than the result type, so we need to + // truncate it. + llvm::Value *ResultTrunc = Builder.CreateTrunc(Result, ResultLLVMTy); + + // To see if the truncation caused an overflow, we will extend + // the result and then compare it to the original result. + llvm::Value *ResultTruncExt = Builder.CreateIntCast( + ResultTrunc, EncompassingLLVMTy, ResultInfo.Signed); + llvm::Value *TruncationOverflow = + Builder.CreateICmpNE(Result, ResultTruncExt); + + Overflow = Builder.CreateOr(Overflow, TruncationOverflow); + Result = ResultTrunc; + } + + // Finally, store the result using the pointer. + Builder.CreateStore(EmitToMemory(Result, ResultQTy), ResultPtr); + + return RValue::get(Overflow); + } + case Builtin::BI__builtin_uadd_overflow: case Builtin::BI__builtin_uaddl_overflow: case Builtin::BI__builtin_uaddll_overflow: @@ -1573,7 +1697,7 @@ // Decide which of the overflow intrinsics we are lowering to: llvm::Intrinsic::ID IntrinsicId; switch (BuiltinID) { - default: llvm_unreachable("Unknown security overflow builtin id."); + default: llvm_unreachable("Unknown overflow builtin id."); case Builtin::BI__builtin_uadd_overflow: case Builtin::BI__builtin_uaddl_overflow: case Builtin::BI__builtin_uaddll_overflow: Index: lib/Sema/SemaChecking.cpp =================================================================== --- lib/Sema/SemaChecking.cpp +++ lib/Sema/SemaChecking.cpp @@ -112,6 +112,37 @@ return false; } +static bool SemaBuiltinOverflow(Sema &S, CallExpr *TheCall) { + if (checkArgCount(S, TheCall, 3)) + return true; + + // First two arguments should be integers. + for (unsigned I = 0; I < 2; ++I) { + Expr *Arg = TheCall->getArg(I); + QualType Ty = Arg->getType(); + if (!Ty->isIntegerType()) { + S.Diag(Arg->getLocStart(), diag::err_overflow_builtin_must_be_int) + << Ty << Arg->getSourceRange(); + return true; + } + } + + // Third argument should be a pointer to a non-const integer. + { + Expr *Arg = TheCall->getArg(2); + QualType Ty = Arg->getType(); + const auto *PtrTy = Ty->getAs(); + if (!(PtrTy && PtrTy->getPointeeType()->isIntegerType() && + !PtrTy->getPointeeType().isConstQualified())) { + S.Diag(Arg->getLocStart(), diag::err_overflow_builtin_must_be_ptr_int) + << Ty << Arg->getSourceRange(); + return true; + } + } + + return false; +} + static void SemaBuiltinMemChkCall(Sema &S, FunctionDecl *FDecl, CallExpr *TheCall, unsigned SizeIdx, unsigned DstSizeIdx) { @@ -457,6 +488,12 @@ if (SemaBuiltinAddressof(*this, TheCall)) return ExprError(); break; + case Builtin::BI__builtin_add_overflow: + case Builtin::BI__builtin_sub_overflow: + case Builtin::BI__builtin_mul_overflow: + if (SemaBuiltinOverflow(*this, TheCall)) + return ExprError(); + break; case Builtin::BI__builtin_operator_new: case Builtin::BI__builtin_operator_delete: if (!getLangOpts().CPlusPlus) { Index: test/CodeGen/builtins-overflow-error.c =================================================================== --- test/CodeGen/builtins-overflow-error.c +++ test/CodeGen/builtins-overflow-error.c @@ -0,0 +1,17 @@ +// RUN: %clang_cc1 -Wall -Werror -fsyntax-only -verify %s + +void test(void) { + unsigned r; + const char * c; + float f; + const unsigned q; + + __builtin_add_overflow(); // expected-error {{too few arguments to function call, expected 3, have 0}} + __builtin_add_overflow(1, 1, 1, 1); // expected-error {{too many arguments to function call, expected 3, have 4}} + + __builtin_add_overflow(c, 1, &r); // expected-error {{operand argument to overflow builtin must be an integer ('const char *' invalid)}} + __builtin_add_overflow(1, c, &r); // expected-error {{operand argument to overflow builtin must be an integer ('const char *' invalid)}} + __builtin_add_overflow(1, 1, 3); // expected-error {{result argument to overflow builtin must be a pointer to a non-const integer ('int' invalid)}} + __builtin_add_overflow(1, 1, &f); // expected-error {{result argument to overflow builtin must be a pointer to a non-const integer ('float *' invalid)}} + __builtin_add_overflow(1, 1, &q); // expected-error {{result argument to overflow builtin must be a pointer to a non-const integer ('const unsigned int *' invalid)}} +} Index: test/CodeGen/builtins-overflow.c =================================================================== --- test/CodeGen/builtins-overflow.c +++ test/CodeGen/builtins-overflow.c @@ -11,7 +11,159 @@ extern int IntErrorCode; extern long LongErrorCode; extern long long LongLongErrorCode; +void overflowed(void); +unsigned test_add_overflow_uint_uint_uint(unsigned x, unsigned y) { + // CHECK: @test_add_overflow_uint_uint_uint + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + unsigned r; + if (__builtin_add_overflow(x, y, &r)) + overflowed(); + return r; +} + +int test_add_overflow_int_int_int(int x, int y) { + // CHECK: @test_add_overflow_int_int_int + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + int r; + if (__builtin_add_overflow(x, y, &r)) + overflowed(); + return r; +} + +unsigned test_sub_overflow_uint_uint_uint(unsigned x, unsigned y) { + // CHECK: @test_sub_overflow_uint_uint_uint + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.usub.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + unsigned r; + if (__builtin_sub_overflow(x, y, &r)) + overflowed(); + return r; +} + +int test_sub_overflow_int_int_int(int x, int y) { + // CHECK: @test_sub_overflow_int_int_int + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + int r; + if (__builtin_sub_overflow(x, y, &r)) + overflowed(); + return r; +} + +unsigned test_mul_overflow_uint_uint_uint(unsigned x, unsigned y) { + // CHECK: @test_mul_overflow_uint_uint_uint + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + unsigned r; + if (__builtin_mul_overflow(x, y, &r)) + overflowed(); + return r; +} + +int test_mul_overflow_int_int_int(int x, int y) { + // CHECK: @test_mul_overflow_int_int_int + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.smul.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + int r; + if (__builtin_mul_overflow(x, y, &r)) + overflowed(); + return r; +} + +int test_add_overflow_uint_int_int(unsigned x, int y) { + // CHECK: @test_add_overflow_uint_int_int + // CHECK: [[XE:%.+]] = zext i32 %{{.+}} to i33 + // CHECK: [[YE:%.+]] = sext i32 %{{.+}} to i33 + // CHECK: [[S:%.+]] = call { i33, i1 } @llvm.sadd.with.overflow.i33(i33 [[XE]], i33 [[YE]]) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i33, i1 } [[S]], 0 + // CHECK-DAG: [[C1:%.+]] = extractvalue { i33, i1 } [[S]], 1 + // CHECK: [[QT:%.+]] = trunc i33 [[Q]] to i32 + // CHECK: [[QTE:%.+]] = sext i32 [[QT]] to i33 + // CHECK: [[C2:%.+]] = icmp ne i33 [[Q]], [[QTE]] + // CHECK: [[C3:%.+]] = or i1 [[C1]], [[C2]] + // CHECK: store i32 [[QT]], i32* %r + // CHECK: br i1 [[C3]] + int r; + if (__builtin_add_overflow(x, y, &r)) + overflowed(); + return r; +} + +_Bool test_add_overflow_uint_uint_bool(unsigned x, unsigned y) { + // CHECK: @test_add_overflow_uint_uint_bool + // CHECK-NOT: ext + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}}) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK-DAG: [[C1:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK: [[QT:%.+]] = trunc i32 [[Q]] to i1 + // CHECK: [[QTE:%.+]] = zext i1 [[QT]] to i32 + // CHECK: [[C2:%.+]] = icmp ne i32 [[Q]], [[QTE]] + // CHECK: [[C3:%.+]] = or i1 [[C1]], [[C2]] + // CHECK: [[QT2:%.+]] = zext i1 [[QT]] to i8 + // CHECK: store i8 [[QT2]], i8* %r + // CHECK: br i1 [[C3]] + _Bool r; + if (__builtin_add_overflow(x, y, &r)) + overflowed(); + return r; +} + +unsigned test_add_overflow_bool_bool_uint(_Bool x, _Bool y) { + // CHECK: @test_add_overflow_bool_bool_uint + // CHECK: [[XE:%.+]] = zext i1 %{{.+}} to i32 + // CHECK: [[YE:%.+]] = zext i1 %{{.+}} to i32 + // CHECK: [[S:%.+]] = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 [[XE]], i32 [[YE]]) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0 + // CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1 + // CHECK: store i32 [[Q]], i32* %r + // CHECK: br i1 [[C]] + unsigned r; + if (__builtin_add_overflow(x, y, &r)) + overflowed(); + return r; +} + +_Bool test_add_overflow_bool_bool_bool(_Bool x, _Bool y) { + // CHECK: @test_add_overflow_bool_bool_bool + // CHECK: [[S:%.+]] = call { i1, i1 } @llvm.uadd.with.overflow.i1(i1 %{{.+}}, i1 %{{.+}}) + // CHECK-DAG: [[Q:%.+]] = extractvalue { i1, i1 } [[S]], 0 + // CHECK-DAG: [[C:%.+]] = extractvalue { i1, i1 } [[S]], 1 + // CHECK: [[QT2:%.+]] = zext i1 [[Q]] to i8 + // CHECK: store i8 [[QT2]], i8* %r + // CHECK: br i1 [[C]] + _Bool r; + if (__builtin_add_overflow(x, y, &r)) + overflowed(); + return r; +} + unsigned test_uadd_overflow(unsigned x, unsigned y) { // CHECK: @test_uadd_overflow // CHECK: %{{.+}} = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}})