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llvm-mirror/lib/Target/Mips/MipsMCInstLower.h
Alex Richardson 1e20340b43 Allow negative offsets in MipsMCInstLower::LowerOperand
Summary:
We rely on this in our CHERI backend to address the GOT by generating a
$pc-relative addresses. For this we emit the following code sequence:

lui $1, %pcrel_hi(_CHERI_CAPABILITY_TABLE_-8)
daddiu $1, $1, %pcrel_lo(_CHERI_CAPABILITY_TABLE_-4)
cgetpccincoffset $c1, $1

However, without this change the addend is implicitly converted to
UINT32_MAX and an invalid pointer value is generated.

Reviewers: atanasyan

Reviewed By: atanasyan

Subscribers: merge_guards_bot, sdardis, hiraditya, jrtc27, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70953
2019-12-04 11:30:00 +00:00

54 lines
1.8 KiB
C++

//===- MipsMCInstLower.h - Lower MachineInstr to MCInst --------*- C++ -*--===//
//
// 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
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TARGET_MIPS_MIPSMCINSTLOWER_H
#define LLVM_LIB_TARGET_MIPS_MIPSMCINSTLOWER_H
#include "MCTargetDesc/MipsMCExpr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/Support/Compiler.h"
namespace llvm {
class MachineBasicBlock;
class MachineInstr;
class MCContext;
class MCInst;
class MCOperand;
class MipsAsmPrinter;
/// MipsMCInstLower - This class is used to lower an MachineInstr into an
/// MCInst.
class LLVM_LIBRARY_VISIBILITY MipsMCInstLower {
using MachineOperandType = MachineOperand::MachineOperandType;
MCContext *Ctx;
MipsAsmPrinter &AsmPrinter;
public:
MipsMCInstLower(MipsAsmPrinter &asmprinter);
void Initialize(MCContext *C);
void Lower(const MachineInstr *MI, MCInst &OutMI) const;
MCOperand LowerOperand(const MachineOperand &MO, int64_t offset = 0) const;
private:
MCOperand LowerSymbolOperand(const MachineOperand &MO,
MachineOperandType MOTy, int64_t Offset) const;
MCOperand createSub(MachineBasicBlock *BB1, MachineBasicBlock *BB2,
MipsMCExpr::MipsExprKind Kind) const;
void lowerLongBranchLUi(const MachineInstr *MI, MCInst &OutMI) const;
void lowerLongBranchADDiu(const MachineInstr *MI, MCInst &OutMI,
int Opcode) const;
bool lowerLongBranch(const MachineInstr *MI, MCInst &OutMI) const;
};
} // end namespace llvm
#endif // LLVM_LIB_TARGET_MIPS_MIPSMCINSTLOWER_H