1 //===- X86RegisterInfo.cpp - X86 Register Information -----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the X86 implementation of the MRegisterInfo class. This
11 // file is responsible for the frame pointer elimination optimization on X86.
13 //===----------------------------------------------------------------------===//
16 #include "X86RegisterInfo.h"
17 #include "X86InstrBuilder.h"
18 #include "llvm/Constants.h"
19 #include "llvm/Type.h"
20 #include "llvm/CodeGen/ValueTypes.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/CodeGen/MachineFrameInfo.h"
24 #include "llvm/Target/TargetMachine.h"
25 #include "llvm/Target/TargetFrameInfo.h"
26 #include "Support/CommandLine.h"
32 NoFPElim("disable-fp-elim",
33 cl::desc("Disable frame pointer elimination optimization"));
36 X86RegisterInfo::X86RegisterInfo()
37 : X86GenRegisterInfo(X86::ADJCALLSTACKDOWN, X86::ADJCALLSTACKUP) {}
39 static unsigned getIdx(const TargetRegisterClass *RC) {
40 switch (RC->getSize()) {
41 default: assert(0 && "Invalid data size!");
49 int X86RegisterInfo::storeRegToStackSlot(MachineBasicBlock &MBB,
50 MachineBasicBlock::iterator &MBBI,
51 unsigned SrcReg, int FrameIdx,
52 const TargetRegisterClass *RC) const {
53 static const unsigned Opcode[] =
54 { X86::MOVrm8, X86::MOVrm16, X86::MOVrm32, X86::FSTPr80 };
55 MachineInstr *MI = addFrameReference(BuildMI(Opcode[getIdx(RC)], 5),
56 FrameIdx).addReg(SrcReg);
57 MBBI = MBB.insert(MBBI, MI)+1;
61 int X86RegisterInfo::loadRegFromStackSlot(MachineBasicBlock &MBB,
62 MachineBasicBlock::iterator &MBBI,
63 unsigned DestReg, int FrameIdx,
64 const TargetRegisterClass *RC) const{
65 static const unsigned Opcode[] =
66 { X86::MOVmr8, X86::MOVmr16, X86::MOVmr32, X86::FLDr80 };
67 MachineInstr *MI = addFrameReference(BuildMI(Opcode[getIdx(RC)], 4, DestReg),
69 MBBI = MBB.insert(MBBI, MI)+1;
73 int X86RegisterInfo::copyRegToReg(MachineBasicBlock &MBB,
74 MachineBasicBlock::iterator &MBBI,
75 unsigned DestReg, unsigned SrcReg,
76 const TargetRegisterClass *RC) const {
77 static const unsigned Opcode[] =
78 { X86::MOVrr8, X86::MOVrr16, X86::MOVrr32, X86::FpMOV };
79 MachineInstr *MI = BuildMI(Opcode[getIdx(RC)],1,DestReg).addReg(SrcReg);
80 MBBI = MBB.insert(MBBI, MI)+1;
84 //===----------------------------------------------------------------------===//
85 // Stack Frame Processing methods
86 //===----------------------------------------------------------------------===//
88 // hasFP - Return true if the specified function should have a dedicated frame
89 // pointer register. This is true if the function has variable sized allocas or
90 // if frame pointer elimination is disabled.
92 static bool hasFP(MachineFunction &MF) {
93 return NoFPElim || MF.getFrameInfo()->hasVarSizedObjects();
96 int X86RegisterInfo::eliminateCallFramePseudoInstr(MachineFunction &MF,
97 MachineBasicBlock &MBB,
98 MachineBasicBlock::iterator &I) const {
99 MachineInstr *New = 0, *Old = *I;;
101 // If we have a frame pointer, turn the adjcallstackup instruction into a
102 // 'sub ESP, <amt>' and the adjcallstackdown instruction into 'add ESP,
104 unsigned Amount = Old->getOperand(0).getImmedValue();
106 // We need to keep the stack aligned properly. To do this, we round the
107 // amount of space needed for the outgoing arguments up to the next
108 // alignment boundary.
109 unsigned Align = MF.getTarget().getFrameInfo().getStackAlignment();
110 Amount = (Amount+Align-1)/Align*Align;
112 if (Old->getOpcode() == X86::ADJCALLSTACKDOWN) {
113 New=BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(Amount);
115 assert(Old->getOpcode() == X86::ADJCALLSTACKUP);
116 New=BuildMI(X86::ADDri32, 2, X86::ESP).addReg(X86::ESP).addZImm(Amount);
122 *I = New; // Replace the pseudo instruction with a new instruction...
126 I = MBB.erase(I);// Just delete the pseudo instruction...
132 int X86RegisterInfo::eliminateFrameIndex(MachineFunction &MF,
133 MachineBasicBlock::iterator &II) const {
135 MachineInstr &MI = **II;
136 while (!MI.getOperand(i).isFrameIndex()) {
138 assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
141 int FrameIndex = MI.getOperand(i).getFrameIndex();
143 // This must be part of a four operand memory reference. Replace the
144 // FrameIndex with base register with EBP. Add add an offset to the offset.
145 MI.SetMachineOperandReg(i, hasFP(MF) ? X86::EBP : X86::ESP);
147 // Now add the frame object offset to the offset from EBP.
148 int Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex) +
149 MI.getOperand(i+3).getImmedValue()+4;
152 Offset += MF.getFrameInfo()->getStackSize();
154 MI.SetMachineOperandConst(i+3, MachineOperand::MO_SignExtendedImmed, Offset);
158 int X86RegisterInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF)
161 // Create a frame entry for the EBP register that must be saved.
162 int FrameIdx = MF.getFrameInfo()->CreateStackObject(4, 4);
163 assert(FrameIdx == MF.getFrameInfo()->getObjectIndexEnd()-1 &&
164 "Slot for EBP register must be last in order to be found!");
169 int X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
170 MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB
171 MachineBasicBlock::iterator MBBI = MBB.begin();
172 MachineFrameInfo *MFI = MF.getFrameInfo();
175 unsigned oldSize = MBB.size();
176 // Get the number of bytes to allocate from the FrameInfo
177 unsigned NumBytes = MFI->getStackSize();
179 // Get the offset of the stack slot for the EBP register... which is
180 // guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
181 int EBPOffset = MFI->getObjectOffset(MFI->getObjectIndexEnd()-1)+4;
183 if (NumBytes) { // adjust stack pointer: ESP -= numbytes
184 MI= BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes);
185 MBBI = MBB.insert(MBBI, MI)+1;
188 // Save EBP into the appropriate stack slot...
189 MI = addRegOffset(BuildMI(X86::MOVrm32, 5), // mov [ESP-<offset>], EBP
190 X86::ESP, EBPOffset+NumBytes).addReg(X86::EBP);
191 MBBI = MBB.insert(MBBI, MI)+1;
193 // Update EBP with the new base value...
194 if (NumBytes == 0) // mov EBP, ESP
195 MI = BuildMI(X86::MOVrr32, 2, X86::EBP).addReg(X86::ESP);
196 else // lea EBP, [ESP+StackSize]
197 MI = addRegOffset(BuildMI(X86::LEAr32, 5, X86::EBP), X86::ESP, NumBytes);
199 MBBI = MBB.insert(MBBI, MI)+1;
202 // When we have no frame pointer, we reserve argument space for call sites
203 // in the function immediately on entry to the current function. This
204 // eliminates the need for add/sub ESP brackets around call sites.
206 NumBytes += MFI->getMaxCallFrameSize();
208 // Round the size to a multiple of the alignment (don't forget the 4 byte
210 unsigned Align = MF.getTarget().getFrameInfo().getStackAlignment();
211 NumBytes = ((NumBytes+4)+Align-1)/Align*Align - 4;
213 // Update frame info to pretend that this is part of the stack...
214 MFI->setStackSize(NumBytes);
217 // adjust stack pointer: ESP -= numbytes
218 MI= BuildMI(X86::SUBri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes);
219 MBB.insert(MBBI, MI);
222 return MBB.size() - oldSize;
225 int X86RegisterInfo::emitEpilogue(MachineFunction &MF,
226 MachineBasicBlock &MBB) const {
227 unsigned oldSize = MBB.size();
228 const MachineFrameInfo *MFI = MF.getFrameInfo();
229 MachineBasicBlock::iterator MBBI = MBB.end()-1;
231 assert((*MBBI)->getOpcode() == X86::RET &&
232 "Can only insert epilog into returning blocks");
235 // Get the offset of the stack slot for the EBP register... which is
236 // guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
237 int EBPOffset = MFI->getObjectOffset(MFI->getObjectIndexEnd()-1)+4;
240 MI = BuildMI(X86::MOVrr32, 1,X86::ESP).addReg(X86::EBP);
241 MBBI = 1+MBB.insert(MBBI, MI);
243 // mov EBP, [ESP-<offset>]
244 MI = addRegOffset(BuildMI(X86::MOVmr32, 5, X86::EBP), X86::ESP, EBPOffset);
245 MBBI = 1+MBB.insert(MBBI, MI);
247 // Get the number of bytes allocated from the FrameInfo...
248 unsigned NumBytes = MFI->getStackSize();
250 if (NumBytes) { // adjust stack pointer back: ESP += numbytes
251 MI =BuildMI(X86::ADDri32, 2, X86::ESP).addReg(X86::ESP).addZImm(NumBytes);
252 MBBI = 1+MBB.insert(MBBI, MI);
255 return MBB.size() - oldSize;
258 } // End llvm namespace
260 #include "X86GenRegisterInfo.inc"
264 const TargetRegisterClass*
265 X86RegisterInfo::getRegClassForType(const Type* Ty) const {
266 switch (Ty->getPrimitiveID()) {
268 case Type::ULongTyID: assert(0 && "Long values can't fit in registers!");
269 default: assert(0 && "Invalid type to getClass!");
271 case Type::SByteTyID:
272 case Type::UByteTyID: return &R8Instance;
273 case Type::ShortTyID:
274 case Type::UShortTyID: return &R16Instance;
277 case Type::PointerTyID: return &R32Instance;
279 case Type::FloatTyID:
280 case Type::DoubleTyID: return &RFPInstance;
284 } // End llvm namespace