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llvm-mirror/lib/MC/MCInstPrinter.cpp
Jonas Devlieghere ab486fe71a [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

llvm-svn: 371159
2019-09-06 01:13:32 +00:00

121 lines
3.5 KiB
C++

//===- MCInstPrinter.cpp - Convert an MCInst to target assembly syntax ----===//
//
// 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/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include <cinttypes>
#include <cstdint>
using namespace llvm;
void llvm::dumpBytes(ArrayRef<uint8_t> bytes, raw_ostream &OS) {
static const char hex_rep[] = "0123456789abcdef";
bool First = true;
for (char i: bytes) {
if (First)
First = false;
else
OS << ' ';
OS << hex_rep[(i & 0xF0) >> 4];
OS << hex_rep[i & 0xF];
}
}
MCInstPrinter::~MCInstPrinter() = default;
/// getOpcodeName - Return the name of the specified opcode enum (e.g.
/// "MOV32ri") or empty if we can't resolve it.
StringRef MCInstPrinter::getOpcodeName(unsigned Opcode) const {
return MII.getName(Opcode);
}
void MCInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const {
llvm_unreachable("Target should implement this");
}
void MCInstPrinter::printAnnotation(raw_ostream &OS, StringRef Annot) {
if (!Annot.empty()) {
if (CommentStream) {
(*CommentStream) << Annot;
// By definition (see MCInstPrinter.h), CommentStream must end with
// a newline after each comment.
if (Annot.back() != '\n')
(*CommentStream) << '\n';
} else
OS << " " << MAI.getCommentString() << " " << Annot;
}
}
/// Utility functions to make adding mark ups simpler.
StringRef MCInstPrinter::markup(StringRef s) const {
if (getUseMarkup())
return s;
else
return "";
}
// For asm-style hex (e.g. 0ffh) the first digit always has to be a number.
static bool needsLeadingZero(uint64_t Value)
{
while (Value)
{
uint64_t digit = (Value >> 60) & 0xf;
if (digit != 0)
return (digit >= 0xa);
Value <<= 4;
}
return false;
}
format_object<int64_t> MCInstPrinter::formatDec(int64_t Value) const {
return format("%" PRId64, Value);
}
format_object<int64_t> MCInstPrinter::formatHex(int64_t Value) const {
switch (PrintHexStyle) {
case HexStyle::C:
if (Value < 0) {
if (Value == std::numeric_limits<int64_t>::min())
return format<int64_t>("-0x8000000000000000", Value);
return format("-0x%" PRIx64, -Value);
}
return format("0x%" PRIx64, Value);
case HexStyle::Asm:
if (Value < 0) {
if (Value == std::numeric_limits<int64_t>::min())
return format<int64_t>("-8000000000000000h", Value);
if (needsLeadingZero(-(uint64_t)(Value)))
return format("-0%" PRIx64 "h", -Value);
return format("-%" PRIx64 "h", -Value);
}
if (needsLeadingZero((uint64_t)(Value)))
return format("0%" PRIx64 "h", Value);
return format("%" PRIx64 "h", Value);
}
llvm_unreachable("unsupported print style");
}
format_object<uint64_t> MCInstPrinter::formatHex(uint64_t Value) const {
switch(PrintHexStyle) {
case HexStyle::C:
return format("0x%" PRIx64, Value);
case HexStyle::Asm:
if (needsLeadingZero(Value))
return format("0%" PRIx64 "h", Value);
else
return format("%" PRIx64 "h", Value);
}
llvm_unreachable("unsupported print style");
}