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Certain ARM instructions accept 32-bit immediate operands encoded as a 8-bit integer value (0-255) and a 4-bit rotation (0-30, even). Current ARM assembly syntax support in LLVM allows the decoded (32-bit) immediate to be specified as a single immediate operand for such instructions: mov r0, #4278190080 The ARMARM defines an extended assembly syntax allowing the encoding to be made more explicit, as in: mov r0, #255, #8 ; (same 32-bit value as above) The behaviour of the two instructions can be different w.r.t flags, which is documented under "Modified immediate constants" in ARMARM. This patch enables support for this extended syntax at the MC layer. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223113 91177308-0d34-0410-b5e6-96231b3b80d8
164 lines
5.0 KiB
C++
164 lines
5.0 KiB
C++
//===-- ARMMCInstLower.cpp - Convert ARM MachineInstr to an MCInst --------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains code to lower ARM MachineInstrs to their corresponding
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// MCInst records.
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//
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//===----------------------------------------------------------------------===//
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#include "ARM.h"
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#include "ARMAsmPrinter.h"
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#include "MCTargetDesc/ARMBaseInfo.h"
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#include "MCTargetDesc/ARMMCExpr.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Mangler.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCInst.h"
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using namespace llvm;
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MCOperand ARMAsmPrinter::GetSymbolRef(const MachineOperand &MO,
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const MCSymbol *Symbol) {
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const MCExpr *Expr;
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unsigned Option = MO.getTargetFlags() & ARMII::MO_OPTION_MASK;
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switch (Option) {
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default: {
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Expr = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_None,
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OutContext);
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switch (Option) {
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default: llvm_unreachable("Unknown target flag on symbol operand");
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case ARMII::MO_NO_FLAG:
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break;
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case ARMII::MO_LO16:
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Expr = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_None,
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OutContext);
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Expr = ARMMCExpr::CreateLower16(Expr, OutContext);
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break;
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case ARMII::MO_HI16:
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Expr = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_None,
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OutContext);
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Expr = ARMMCExpr::CreateUpper16(Expr, OutContext);
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break;
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}
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break;
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}
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case ARMII::MO_PLT:
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Expr = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_PLT,
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OutContext);
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break;
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}
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if (!MO.isJTI() && MO.getOffset())
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Expr = MCBinaryExpr::CreateAdd(Expr,
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MCConstantExpr::Create(MO.getOffset(),
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OutContext),
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OutContext);
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return MCOperand::CreateExpr(Expr);
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}
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bool ARMAsmPrinter::lowerOperand(const MachineOperand &MO,
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MCOperand &MCOp) {
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switch (MO.getType()) {
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default: llvm_unreachable("unknown operand type");
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case MachineOperand::MO_Register:
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// Ignore all non-CPSR implicit register operands.
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if (MO.isImplicit() && MO.getReg() != ARM::CPSR)
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return false;
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assert(!MO.getSubReg() && "Subregs should be eliminated!");
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MCOp = MCOperand::CreateReg(MO.getReg());
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break;
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case MachineOperand::MO_Immediate:
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MCOp = MCOperand::CreateImm(MO.getImm());
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break;
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case MachineOperand::MO_MachineBasicBlock:
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MCOp = MCOperand::CreateExpr(MCSymbolRefExpr::Create(
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MO.getMBB()->getSymbol(), OutContext));
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break;
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case MachineOperand::MO_GlobalAddress: {
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MCOp = GetSymbolRef(MO,
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GetARMGVSymbol(MO.getGlobal(), MO.getTargetFlags()));
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break;
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}
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case MachineOperand::MO_ExternalSymbol:
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MCOp = GetSymbolRef(MO,
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GetExternalSymbolSymbol(MO.getSymbolName()));
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break;
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case MachineOperand::MO_JumpTableIndex:
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MCOp = GetSymbolRef(MO, GetJTISymbol(MO.getIndex()));
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break;
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case MachineOperand::MO_ConstantPoolIndex:
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MCOp = GetSymbolRef(MO, GetCPISymbol(MO.getIndex()));
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break;
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case MachineOperand::MO_BlockAddress:
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MCOp = GetSymbolRef(MO, GetBlockAddressSymbol(MO.getBlockAddress()));
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break;
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case MachineOperand::MO_FPImmediate: {
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APFloat Val = MO.getFPImm()->getValueAPF();
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bool ignored;
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Val.convert(APFloat::IEEEdouble, APFloat::rmTowardZero, &ignored);
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MCOp = MCOperand::CreateFPImm(Val.convertToDouble());
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break;
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}
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case MachineOperand::MO_RegisterMask:
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// Ignore call clobbers.
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return false;
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}
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return true;
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}
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void llvm::LowerARMMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
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ARMAsmPrinter &AP) {
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OutMI.setOpcode(MI->getOpcode());
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// In the MC layer, we keep modified immediates in their encoded form
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bool EncodeImms = false;
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switch (MI->getOpcode()) {
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default: break;
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case ARM::MOVi:
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case ARM::MVNi:
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case ARM::CMPri:
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case ARM::CMNri:
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case ARM::TSTri:
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case ARM::TEQri:
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case ARM::MSRi:
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case ARM::ADCri:
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case ARM::ADDri:
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case ARM::ADDSri:
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case ARM::SBCri:
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case ARM::SUBri:
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case ARM::SUBSri:
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case ARM::ANDri:
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case ARM::ORRri:
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case ARM::EORri:
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case ARM::BICri:
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case ARM::RSBri:
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case ARM::RSBSri:
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case ARM::RSCri:
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EncodeImms = true;
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break;
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}
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for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
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const MachineOperand &MO = MI->getOperand(i);
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MCOperand MCOp;
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if (AP.lowerOperand(MO, MCOp)) {
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if (MCOp.isImm() && EncodeImms) {
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int32_t Enc = ARM_AM::getSOImmVal(MCOp.getImm());
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if (Enc != -1)
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MCOp.setImm(Enc);
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}
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OutMI.addOperand(MCOp);
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}
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}
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}
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