llvm/unittests/MC/MCInstPrinter.cpp
Jonas Devlieghere e9377b9227 [MC] Fix undefined behavior in MCInstPrinter::formatHex
Passing INT64_MIN to MCInstPrinter::formatHex triggers undefined
behavior because the negation of -9223372036854775808 cannot be
represented in type 'int64_t' (aka 'long long'). This patch puts a
workaround in place to just print the hex value directly.

A possible alternative involves using a small helper functions that uses
(implementation) defined conversions to achieve the desirable value:

  static int64_t helper(int64_t V) {
    auto U = static_cast<uint64_t>(V);
    return V < 0 ? -U : U;
  }

The underlying problem is that MCInstPrinter::formatHex(int64_t) returns
a format_object<int64_t> and should really return a
format_object<uint64_t>. However, that's not possible because formatImm
needs to be able to print both as decimal (where a signed is required)
and hex (where we'd prefer to always have an unsigned).

  format_object<int64_t> formatImm(int64_t Value) const {
    return PrintImmHex ? formatHex(Value) : formatDec(Value);
  }

Differential revision: https://reviews.llvm.org/D67236

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371159 91177308-0d34-0410-b5e6-96231b3b80d8
2019-09-06 01:13:32 +00:00

69 lines
2.0 KiB
C++

//===- llvm/unittest/MC/MCInstPrinter.cpp ---------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "gtest/gtest.h"
using namespace llvm;
namespace {
class MCInstPrinterTest : public ::testing::Test {
public:
std::unique_ptr<MCRegisterInfo> MRI;
std::unique_ptr<MCAsmInfo> MAI;
std::unique_ptr<const MCInstrInfo> MII;
std::unique_ptr<MCInstPrinter> Printer;
MCInstPrinterTest() {
llvm::InitializeAllTargetInfos();
llvm::InitializeAllTargetMCs();
std::string TripleName = "x86_64-pc-linux";
std::string ErrorStr;
const Target *TheTarget =
TargetRegistry::lookupTarget(TripleName, ErrorStr);
// If we didn't build x86, do not run the test.
if (!TheTarget)
return;
MRI.reset(TheTarget->createMCRegInfo(TripleName));
MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName));
MII.reset(TheTarget->createMCInstrInfo());
Printer.reset(TheTarget->createMCInstPrinter(
Triple(TripleName), MAI->getAssemblerDialect(), *MAI, *MII, *MRI));
}
template <typename T> std::string formatHex(T i) {
std::string Buffer;
raw_string_ostream OS(Buffer);
OS << Printer->formatHex(i);
OS.flush();
return Buffer;
}
};
} // namespace
TEST_F(MCInstPrinterTest, formatHex) {
if (!Printer)
return;
EXPECT_EQ("0x1", formatHex<int64_t>(1));
EXPECT_EQ("0x7fffffffffffffff",
formatHex(std::numeric_limits<int64_t>::max()));
EXPECT_EQ("-0x8000000000000000",
formatHex(std::numeric_limits<int64_t>::min()));
}