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llvm-mirror/lib/Target/Mips/MipsMCInstLower.cpp
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

329 lines
9.7 KiB
C++

//===- MipsMCInstLower.cpp - Convert Mips MachineInstr to MCInst ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains code to lower Mips MachineInstrs to their corresponding
// MCInst records.
//
//===----------------------------------------------------------------------===//
#include "MipsMCInstLower.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "MCTargetDesc/MipsMCExpr.h"
#include "MipsAsmPrinter.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
using namespace llvm;
MipsMCInstLower::MipsMCInstLower(MipsAsmPrinter &asmprinter)
: AsmPrinter(asmprinter) {}
void MipsMCInstLower::Initialize(MCContext *C) {
Ctx = C;
}
MCOperand MipsMCInstLower::LowerSymbolOperand(const MachineOperand &MO,
MachineOperandType MOTy,
int64_t Offset) const {
MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
MipsMCExpr::MipsExprKind TargetKind = MipsMCExpr::MEK_None;
bool IsGpOff = false;
const MCSymbol *Symbol;
switch(MO.getTargetFlags()) {
default:
llvm_unreachable("Invalid target flag!");
case MipsII::MO_NO_FLAG:
break;
case MipsII::MO_GPREL:
TargetKind = MipsMCExpr::MEK_GPREL;
break;
case MipsII::MO_GOT_CALL:
TargetKind = MipsMCExpr::MEK_GOT_CALL;
break;
case MipsII::MO_GOT:
TargetKind = MipsMCExpr::MEK_GOT;
break;
case MipsII::MO_ABS_HI:
TargetKind = MipsMCExpr::MEK_HI;
break;
case MipsII::MO_ABS_LO:
TargetKind = MipsMCExpr::MEK_LO;
break;
case MipsII::MO_TLSGD:
TargetKind = MipsMCExpr::MEK_TLSGD;
break;
case MipsII::MO_TLSLDM:
TargetKind = MipsMCExpr::MEK_TLSLDM;
break;
case MipsII::MO_DTPREL_HI:
TargetKind = MipsMCExpr::MEK_DTPREL_HI;
break;
case MipsII::MO_DTPREL_LO:
TargetKind = MipsMCExpr::MEK_DTPREL_LO;
break;
case MipsII::MO_GOTTPREL:
TargetKind = MipsMCExpr::MEK_GOTTPREL;
break;
case MipsII::MO_TPREL_HI:
TargetKind = MipsMCExpr::MEK_TPREL_HI;
break;
case MipsII::MO_TPREL_LO:
TargetKind = MipsMCExpr::MEK_TPREL_LO;
break;
case MipsII::MO_GPOFF_HI:
TargetKind = MipsMCExpr::MEK_HI;
IsGpOff = true;
break;
case MipsII::MO_GPOFF_LO:
TargetKind = MipsMCExpr::MEK_LO;
IsGpOff = true;
break;
case MipsII::MO_GOT_DISP:
TargetKind = MipsMCExpr::MEK_GOT_DISP;
break;
case MipsII::MO_GOT_HI16:
TargetKind = MipsMCExpr::MEK_GOT_HI16;
break;
case MipsII::MO_GOT_LO16:
TargetKind = MipsMCExpr::MEK_GOT_LO16;
break;
case MipsII::MO_GOT_PAGE:
TargetKind = MipsMCExpr::MEK_GOT_PAGE;
break;
case MipsII::MO_GOT_OFST:
TargetKind = MipsMCExpr::MEK_GOT_OFST;
break;
case MipsII::MO_HIGHER:
TargetKind = MipsMCExpr::MEK_HIGHER;
break;
case MipsII::MO_HIGHEST:
TargetKind = MipsMCExpr::MEK_HIGHEST;
break;
case MipsII::MO_CALL_HI16:
TargetKind = MipsMCExpr::MEK_CALL_HI16;
break;
case MipsII::MO_CALL_LO16:
TargetKind = MipsMCExpr::MEK_CALL_LO16;
break;
case MipsII::MO_JALR:
return MCOperand();
}
switch (MOTy) {
case MachineOperand::MO_MachineBasicBlock:
Symbol = MO.getMBB()->getSymbol();
break;
case MachineOperand::MO_GlobalAddress:
Symbol = AsmPrinter.getSymbol(MO.getGlobal());
Offset += MO.getOffset();
break;
case MachineOperand::MO_BlockAddress:
Symbol = AsmPrinter.GetBlockAddressSymbol(MO.getBlockAddress());
Offset += MO.getOffset();
break;
case MachineOperand::MO_ExternalSymbol:
Symbol = AsmPrinter.GetExternalSymbolSymbol(MO.getSymbolName());
Offset += MO.getOffset();
break;
case MachineOperand::MO_MCSymbol:
Symbol = MO.getMCSymbol();
Offset += MO.getOffset();
break;
case MachineOperand::MO_JumpTableIndex:
Symbol = AsmPrinter.GetJTISymbol(MO.getIndex());
break;
case MachineOperand::MO_ConstantPoolIndex:
Symbol = AsmPrinter.GetCPISymbol(MO.getIndex());
Offset += MO.getOffset();
break;
default:
llvm_unreachable("<unknown operand type>");
}
const MCExpr *Expr = MCSymbolRefExpr::create(Symbol, Kind, *Ctx);
if (Offset) {
// Note: Offset can also be negative
Expr = MCBinaryExpr::createAdd(Expr, MCConstantExpr::create(Offset, *Ctx),
*Ctx);
}
if (IsGpOff)
Expr = MipsMCExpr::createGpOff(TargetKind, Expr, *Ctx);
else if (TargetKind != MipsMCExpr::MEK_None)
Expr = MipsMCExpr::create(TargetKind, Expr, *Ctx);
return MCOperand::createExpr(Expr);
}
MCOperand MipsMCInstLower::LowerOperand(const MachineOperand &MO,
int64_t offset) const {
MachineOperandType MOTy = MO.getType();
switch (MOTy) {
default: llvm_unreachable("unknown operand type");
case MachineOperand::MO_Register:
// Ignore all implicit register operands.
if (MO.isImplicit()) break;
return MCOperand::createReg(MO.getReg());
case MachineOperand::MO_Immediate:
return MCOperand::createImm(MO.getImm() + offset);
case MachineOperand::MO_MachineBasicBlock:
case MachineOperand::MO_GlobalAddress:
case MachineOperand::MO_ExternalSymbol:
case MachineOperand::MO_MCSymbol:
case MachineOperand::MO_JumpTableIndex:
case MachineOperand::MO_ConstantPoolIndex:
case MachineOperand::MO_BlockAddress:
return LowerSymbolOperand(MO, MOTy, offset);
case MachineOperand::MO_RegisterMask:
break;
}
return MCOperand();
}
MCOperand MipsMCInstLower::createSub(MachineBasicBlock *BB1,
MachineBasicBlock *BB2,
MipsMCExpr::MipsExprKind Kind) const {
const MCSymbolRefExpr *Sym1 = MCSymbolRefExpr::create(BB1->getSymbol(), *Ctx);
const MCSymbolRefExpr *Sym2 = MCSymbolRefExpr::create(BB2->getSymbol(), *Ctx);
const MCBinaryExpr *Sub = MCBinaryExpr::createSub(Sym1, Sym2, *Ctx);
return MCOperand::createExpr(MipsMCExpr::create(Kind, Sub, *Ctx));
}
void MipsMCInstLower::
lowerLongBranchLUi(const MachineInstr *MI, MCInst &OutMI) const {
OutMI.setOpcode(Mips::LUi);
// Lower register operand.
OutMI.addOperand(LowerOperand(MI->getOperand(0)));
MipsMCExpr::MipsExprKind Kind;
unsigned TargetFlags = MI->getOperand(1).getTargetFlags();
switch (TargetFlags) {
case MipsII::MO_HIGHEST:
Kind = MipsMCExpr::MEK_HIGHEST;
break;
case MipsII::MO_HIGHER:
Kind = MipsMCExpr::MEK_HIGHER;
break;
case MipsII::MO_ABS_HI:
Kind = MipsMCExpr::MEK_HI;
break;
case MipsII::MO_ABS_LO:
Kind = MipsMCExpr::MEK_LO;
break;
default:
report_fatal_error("Unexpected flags for lowerLongBranchLUi");
}
if (MI->getNumOperands() == 2) {
const MCExpr *Expr =
MCSymbolRefExpr::create(MI->getOperand(1).getMBB()->getSymbol(), *Ctx);
const MipsMCExpr *MipsExpr = MipsMCExpr::create(Kind, Expr, *Ctx);
OutMI.addOperand(MCOperand::createExpr(MipsExpr));
} else if (MI->getNumOperands() == 3) {
// Create %hi($tgt-$baltgt).
OutMI.addOperand(createSub(MI->getOperand(1).getMBB(),
MI->getOperand(2).getMBB(), Kind));
}
}
void MipsMCInstLower::lowerLongBranchADDiu(const MachineInstr *MI,
MCInst &OutMI, int Opcode) const {
OutMI.setOpcode(Opcode);
MipsMCExpr::MipsExprKind Kind;
unsigned TargetFlags = MI->getOperand(2).getTargetFlags();
switch (TargetFlags) {
case MipsII::MO_HIGHEST:
Kind = MipsMCExpr::MEK_HIGHEST;
break;
case MipsII::MO_HIGHER:
Kind = MipsMCExpr::MEK_HIGHER;
break;
case MipsII::MO_ABS_HI:
Kind = MipsMCExpr::MEK_HI;
break;
case MipsII::MO_ABS_LO:
Kind = MipsMCExpr::MEK_LO;
break;
default:
report_fatal_error("Unexpected flags for lowerLongBranchADDiu");
}
// Lower two register operands.
for (unsigned I = 0, E = 2; I != E; ++I) {
const MachineOperand &MO = MI->getOperand(I);
OutMI.addOperand(LowerOperand(MO));
}
if (MI->getNumOperands() == 3) {
// Lower register operand.
const MCExpr *Expr =
MCSymbolRefExpr::create(MI->getOperand(2).getMBB()->getSymbol(), *Ctx);
const MipsMCExpr *MipsExpr = MipsMCExpr::create(Kind, Expr, *Ctx);
OutMI.addOperand(MCOperand::createExpr(MipsExpr));
} else if (MI->getNumOperands() == 4) {
// Create %lo($tgt-$baltgt) or %hi($tgt-$baltgt).
OutMI.addOperand(createSub(MI->getOperand(2).getMBB(),
MI->getOperand(3).getMBB(), Kind));
}
}
bool MipsMCInstLower::lowerLongBranch(const MachineInstr *MI,
MCInst &OutMI) const {
switch (MI->getOpcode()) {
default:
return false;
case Mips::LONG_BRANCH_LUi:
case Mips::LONG_BRANCH_LUi2Op:
case Mips::LONG_BRANCH_LUi2Op_64:
lowerLongBranchLUi(MI, OutMI);
return true;
case Mips::LONG_BRANCH_ADDiu:
case Mips::LONG_BRANCH_ADDiu2Op:
lowerLongBranchADDiu(MI, OutMI, Mips::ADDiu);
return true;
case Mips::LONG_BRANCH_DADDiu:
case Mips::LONG_BRANCH_DADDiu2Op:
lowerLongBranchADDiu(MI, OutMI, Mips::DADDiu);
return true;
}
}
void MipsMCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
if (lowerLongBranch(MI, OutMI))
return;
OutMI.setOpcode(MI->getOpcode());
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
MCOperand MCOp = LowerOperand(MO);
if (MCOp.isValid())
OutMI.addOperand(MCOp);
}
}