[llvm] r326516 - Utility functions for checked arithmetic
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 2 09:17:01 PST 2018
Using out params is a bit ugly for this. Did you consider either
returning pair, struct, or optional result?
Philip
On 03/01/2018 04:30 PM, George Karpenkov via llvm-commits wrote:
> Author: george.karpenkov
> Date: Thu Mar 1 16:30:43 2018
> New Revision: 326516
>
> URL: http://llvm.org/viewvc/llvm-project?rev=326516&view=rev
> Log:
> Utility functions for checked arithmetic
>
> Provide checkedAdd and checkedMul functions, providing checked
> arithmetic on signed integers.
>
> Differential Revision: https://reviews.llvm.org/D43704
>
> Added:
> llvm/trunk/include/llvm/Support/CheckedArithmetic.h
> llvm/trunk/unittests/Support/CheckedArithmeticTest.cpp
> Modified:
> llvm/trunk/unittests/Support/CMakeLists.txt
>
> Added: llvm/trunk/include/llvm/Support/CheckedArithmetic.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/CheckedArithmetic.h?rev=326516&view=auto
> ==============================================================================
> --- llvm/trunk/include/llvm/Support/CheckedArithmetic.h (added)
> +++ llvm/trunk/include/llvm/Support/CheckedArithmetic.h Thu Mar 1 16:30:43 2018
> @@ -0,0 +1,83 @@
> +//==-- llvm/Support/CheckedArithmetic.h - Safe arithmetical operations *- C++ //
> +//
> +// The LLVM Compiler Infrastructure
> +//
> +// This file is distributed under the University of Illinois Open Source
> +// License. See LICENSE.TXT for details.
> +//
> +//===----------------------------------------------------------------------===//
> +//
> +// This file contains generic functions for operating on integers which
> +// give the indication on whether the operation has overflown.
> +//
> +//===----------------------------------------------------------------------===//
> +
> +#ifndef LLVM_SUPPORT_CHECKEDARITHMETIC_H
> +#define LLVM_SUPPORT_CHECKEDARITHMETIC_H
> +
> +#include "llvm/ADT/APInt.h"
> +
> +#include <type_traits>
> +
> +namespace {
> +
> +/// Utility function to apply a given method of \c APInt \p F to \p LHS and
> +/// \p RHS, and write the output into \p Res.
> +/// \return Whether the operation overflows.
> +template <typename T, typename F>
> +typename std::enable_if<std::is_integral<T>::value && sizeof(T) * 8 <= 64,
> + bool>::type
> +checkedOp(T LHS, T RHS, F Op, T *Res = nullptr, bool Signed = true) {
> + llvm::APInt ALHS(/*BitSize=*/sizeof(T) * 8, LHS, Signed);
> + llvm::APInt ARHS(/*BitSize=*/sizeof(T) * 8, RHS, Signed);
> + bool Overflow;
> + llvm::APInt Out = (ALHS.*Op)(ARHS, Overflow);
> + if (Res)
> + *Res = Signed ? Out.getSExtValue() : Out.getZExtValue();
> + return Overflow;
> +}
> +}
> +
> +namespace llvm {
> +
> +/// Add two signed integers \p LHS and \p RHS, write into \p Res if non-null.
> +/// Does not guarantee saturating arithmetic.
> +/// \return Whether the result overflows.
> +template <typename T>
> +typename std::enable_if<std::is_signed<T>::value, bool>::type
> +checkedAdd(T LHS, T RHS, T *Res = nullptr) {
> + return checkedOp(LHS, RHS, &llvm::APInt::sadd_ov, Res);
> +}
> +
> +/// Multiply two signed integers \p LHS and \p RHS, write into \p Res if
> +/// non-null.
> +/// Does not guarantee saturating arithmetic.
> +/// \return Whether the result overflows.
> +template <typename T>
> +typename std::enable_if<std::is_signed<T>::value, bool>::type
> +checkedMul(T LHS, T RHS, T *Res = nullptr) {
> + return checkedOp(LHS, RHS, &llvm::APInt::smul_ov, Res);
> +}
> +
> +/// Add two unsigned integers \p LHS and \p RHS, write into \p Res if non-null.
> +/// Does not guarantee saturating arithmetic.
> +/// \return Whether the result overflows.
> +template <typename T>
> +typename std::enable_if<std::is_unsigned<T>::value, bool>::type
> +checkedAddUnsigned(T LHS, T RHS, T *Res = nullptr) {
> + return checkedOp(LHS, RHS, &llvm::APInt::uadd_ov, Res, /*Signed=*/false);
> +}
> +
> +/// Multiply two unsigned integers \p LHS and \p RHS, write into \p Res if
> +/// non-null.
> +/// Does not guarantee saturating arithmetic.
> +/// \return Whether the result overflows.
> +template <typename T>
> +typename std::enable_if<std::is_unsigned<T>::value, bool>::type
> +checkedMulUnsigned(T LHS, T RHS, T *Res = nullptr) {
> + return checkedOp(LHS, RHS, &llvm::APInt::umul_ov, Res, /*Signed=*/false);
> +}
> +
> +} // End llvm namespace
> +
> +#endif
>
> Modified: llvm/trunk/unittests/Support/CMakeLists.txt
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/CMakeLists.txt?rev=326516&r1=326515&r2=326516&view=diff
> ==============================================================================
> --- llvm/trunk/unittests/Support/CMakeLists.txt (original)
> +++ llvm/trunk/unittests/Support/CMakeLists.txt Thu Mar 1 16:30:43 2018
> @@ -13,6 +13,7 @@ add_llvm_unittest(SupportTests
> CachePruningTest.cpp
> CrashRecoveryTest.cpp
> Casting.cpp
> + CheckedArithmeticTest.cpp
> Chrono.cpp
> CommandLineTest.cpp
> CompressionTest.cpp
>
> Added: llvm/trunk/unittests/Support/CheckedArithmeticTest.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/CheckedArithmeticTest.cpp?rev=326516&view=auto
> ==============================================================================
> --- llvm/trunk/unittests/Support/CheckedArithmeticTest.cpp (added)
> +++ llvm/trunk/unittests/Support/CheckedArithmeticTest.cpp Thu Mar 1 16:30:43 2018
> @@ -0,0 +1,71 @@
> +#include "llvm/Support/CheckedArithmetic.h"
> +#include "gtest/gtest.h"
> +
> +using namespace llvm;
> +
> +namespace {
> +
> +TEST(CheckedArithmetic, CheckedAdd) {
> + int64_t Out;
> + const int64_t Max = std::numeric_limits<int64_t>::max();
> + const int64_t Min = std::numeric_limits<int64_t>::min();
> + EXPECT_EQ(checkedAdd<int64_t>(Max, Max, &Out), true);
> + EXPECT_EQ(checkedAdd<int64_t>(Min, -1, &Out), true);
> + EXPECT_EQ(checkedAdd<int64_t>(Max, 1, &Out), true);
> + EXPECT_EQ(checkedAdd<int64_t>(10, 1, &Out), false);
> + EXPECT_EQ(Out, 11);
> +}
> +
> +TEST(CheckedArithmetic, CheckedAddSmall) {
> + int16_t Out;
> + const int16_t Max = std::numeric_limits<int16_t>::max();
> + const int16_t Min = std::numeric_limits<int16_t>::min();
> + EXPECT_EQ(checkedAdd<int16_t>(Max, Max, &Out), true);
> + EXPECT_EQ(checkedAdd<int16_t>(Min, -1, &Out), true);
> + EXPECT_EQ(checkedAdd<int16_t>(Max, 1, &Out), true);
> + EXPECT_EQ(checkedAdd<int16_t>(10, 1, &Out), false);
> + EXPECT_EQ(Out, 11);
> +}
> +
> +TEST(CheckedArithmetic, CheckedMul) {
> + int64_t Out;
> + const int64_t Max = std::numeric_limits<int64_t>::max();
> + const int64_t Min = std::numeric_limits<int64_t>::min();
> + EXPECT_EQ(checkedMul<int64_t>(Max, 2, &Out), true);
> + EXPECT_EQ(checkedMul<int64_t>(Max, Max, &Out), true);
> + EXPECT_EQ(checkedMul<int64_t>(Min, 2, &Out), true);
> + EXPECT_EQ(checkedMul<int64_t>(10, 2, &Out), false);
> + EXPECT_EQ(Out, 20);
> +}
> +
> +TEST(CheckedArithmetic, CheckedMulSmall) {
> + int16_t Out;
> + const int16_t Max = std::numeric_limits<int16_t>::max();
> + const int16_t Min = std::numeric_limits<int16_t>::min();
> + EXPECT_EQ(checkedMul<int16_t>(Max, 2, &Out), true);
> + EXPECT_EQ(checkedMul<int16_t>(Max, Max, &Out), true);
> + EXPECT_EQ(checkedMul<int16_t>(Min, 2, &Out), true);
> + EXPECT_EQ(checkedMul<int16_t>(10, 2, &Out), false);
> + EXPECT_EQ(Out, 20);
> +}
> +
> +TEST(CheckedArithmetic, CheckedAddUnsigned) {
> + uint64_t Out;
> + const uint64_t Max = std::numeric_limits<uint64_t>::max();
> + EXPECT_EQ(checkedAddUnsigned<uint64_t>(Max, Max, &Out), true);
> + EXPECT_EQ(checkedAddUnsigned<uint64_t>(Max, 1, &Out), true);
> + EXPECT_EQ(checkedAddUnsigned<uint64_t>(10, 1, &Out), false);
> + EXPECT_EQ(Out, uint64_t(11));
> +}
> +
> +TEST(CheckedArithmetic, CheckedMulUnsigned) {
> + uint64_t Out;
> + const uint64_t Max = std::numeric_limits<uint64_t>::max();
> + EXPECT_EQ(checkedMulUnsigned<uint64_t>(Max, 2, &Out), true);
> + EXPECT_EQ(checkedMulUnsigned<uint64_t>(Max, Max, &Out), true);
> + EXPECT_EQ(checkedMulUnsigned<uint64_t>(10, 2, &Out), false);
> + EXPECT_EQ(Out, uint64_t(20));
> +}
> +
> +
> +} // namespace
>
>
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