[llvm] r326516 - Utility functions for checked arithmetic
George Karpenkov via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 1 16:30:43 PST 2018
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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