maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/lib/Target/Mips/MipsFrameLowering.cpp

326 lines
13 KiB
C++
Raw Blame History

//===-- MipsFrameLowering.cpp - Mips Frame Information --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the Mips implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "MipsFrameLowering.h"
#include "MipsAnalyzeImmediate.h"
#include "MipsInstrInfo.h"
#include "MipsMachineFunction.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
//===----------------------------------------------------------------------===//
//
// Stack Frame Processing methods
// +----------------------------+
//
// The stack is allocated decrementing the stack pointer on
// the first instruction of a function prologue. Once decremented,
// all stack references are done thought a positive offset
// from the stack/frame pointer, so the stack is considering
// to grow up! Otherwise terrible hacks would have to be made
// to get this stack ABI compliant :)
//
// The stack frame required by the ABI (after call):
// Offset
//
// 0 ----------
// 4 Args to pass
// . saved $GP (used in PIC)
// . Alloca allocations
// . Local Area
// . CPU "Callee Saved" Registers
// . saved FP
// . saved RA
// . FPU "Callee Saved" Registers
// StackSize -----------
//
// Offset - offset from sp after stack allocation on function prologue
//
// The sp is the stack pointer subtracted/added from the stack size
// at the Prologue/Epilogue
//
// References to the previous stack (to obtain arguments) are done
// with offsets that exceeds the stack size: (stacksize+(4*(num_arg-1))
//
// Examples:
// - reference to the actual stack frame
// for any local area var there is smt like : FI >= 0, StackOffset: 4
// sw REGX, 4(SP)
//
// - reference to previous stack frame
// suppose there's a load to the 5th arguments : FI < 0, StackOffset: 16.
// The emitted instruction will be something like:
// lw REGX, 16+StackSize(SP)
//
// Since the total stack size is unknown on LowerFormalArguments, all
// stack references (ObjectOffset) created to reference the function
// arguments, are negative numbers. This way, on eliminateFrameIndex it's
// possible to detect those references and the offsets are adjusted to
// their real location.
//
//===----------------------------------------------------------------------===//
// hasFP - Return true if the specified function should have a dedicated frame
// pointer register. This is true if the function has variable sized allocas or
// if frame pointer elimination is disabled.
bool MipsFrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
return MF.getTarget().Options.DisableFramePointerElim(MF) ||
MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken();
}
bool MipsFrameLowering::targetHandlesStackFrameRounding() const {
return true;
}
// Build an instruction sequence to load an immediate that is too large to fit
// in 16-bit and add the result to Reg.
static void expandLargeImm(unsigned Reg, int64_t Imm, bool IsN64,
const MipsInstrInfo &TII, MachineBasicBlock& MBB,
MachineBasicBlock::iterator II, DebugLoc DL) {
unsigned LUi = IsN64 ? Mips::LUi64 : Mips::LUi;
unsigned ADDu = IsN64 ? Mips::DADDu : Mips::ADDu;
unsigned ZEROReg = IsN64 ? Mips::ZERO_64 : Mips::ZERO;
unsigned ATReg = IsN64 ? Mips::AT_64 : Mips::AT;
MipsAnalyzeImmediate AnalyzeImm;
const MipsAnalyzeImmediate::InstSeq &Seq =
AnalyzeImm.Analyze(Imm, IsN64 ? 64 : 32, false /* LastInstrIsADDiu */);
MipsAnalyzeImmediate::InstSeq::const_iterator Inst = Seq.begin();
// The first instruction can be a LUi, which is different from other
// instructions (ADDiu, ORI and SLL) in that it does not have a register
// operand.
if (Inst->Opc == LUi)
BuildMI(MBB, II, DL, TII.get(LUi), ATReg)
.addImm(SignExtend64<16>(Inst->ImmOpnd));
else
BuildMI(MBB, II, DL, TII.get(Inst->Opc), ATReg).addReg(ZEROReg)
.addImm(SignExtend64<16>(Inst->ImmOpnd));
// Build the remaining instructions in Seq.
for (++Inst; Inst != Seq.end(); ++Inst)
BuildMI(MBB, II, DL, TII.get(Inst->Opc), ATReg).addReg(ATReg)
.addImm(SignExtend64<16>(Inst->ImmOpnd));
BuildMI(MBB, II, DL, TII.get(ADDu), Reg).addReg(Reg).addReg(ATReg);
}
void MipsFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineFrameInfo *MFI = MF.getFrameInfo();
MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
const MipsRegisterInfo *RegInfo =
static_cast<const MipsRegisterInfo*>(MF.getTarget().getRegisterInfo());
const MipsInstrInfo &TII =
*static_cast<const MipsInstrInfo*>(MF.getTarget().getInstrInfo());
MachineBasicBlock::iterator MBBI = MBB.begin();
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
bool isPIC = (MF.getTarget().getRelocationModel() == Reloc::PIC_);
unsigned SP = STI.isABI_N64() ? Mips::SP_64 : Mips::SP;
unsigned FP = STI.isABI_N64() ? Mips::FP_64 : Mips::FP;
unsigned ZERO = STI.isABI_N64() ? Mips::ZERO_64 : Mips::ZERO;
unsigned ADDu = STI.isABI_N64() ? Mips::DADDu : Mips::ADDu;
unsigned ADDiu = STI.isABI_N64() ? Mips::DADDiu : Mips::ADDiu;
// First, compute final stack size.
unsigned RegSize = STI.isGP32bit() ? 4 : 8;
unsigned StackAlign = getStackAlignment();
unsigned LocalVarAreaOffset = MipsFI->needGPSaveRestore() ?
(MFI->getObjectOffset(MipsFI->getGPFI()) + RegSize) :
MipsFI->getMaxCallFrameSize();
uint64_t StackSize = RoundUpToAlignment(LocalVarAreaOffset, StackAlign) +
RoundUpToAlignment(MFI->getStackSize(), StackAlign);
// Update stack size
MFI->setStackSize(StackSize);
// Emit instructions that set the global base register if the target ABI is
// O32.
if (isPIC && MipsFI->globalBaseRegSet() && STI.isABI_O32() &&
!MipsFI->globalBaseRegFixed()) {
// See MipsInstrInfo.td for explanation.
MachineBasicBlock *NewEntry = MF.CreateMachineBasicBlock();
MF.insert(&MBB, NewEntry);
NewEntry->addSuccessor(&MBB);
// Copy live in registers.
for (MachineBasicBlock::livein_iterator R = MBB.livein_begin();
R != MBB.livein_end(); ++R)
NewEntry->addLiveIn(*R);
BuildMI(*NewEntry, NewEntry->begin(), dl, TII.get(Mips:: SETGP01),
Mips::V0);
}
// No need to allocate space on the stack.
if (StackSize == 0 && !MFI->adjustsStack()) return;
MachineModuleInfo &MMI = MF.getMMI();
std::vector<MachineMove> &Moves = MMI.getFrameMoves();
MachineLocation DstML, SrcML;
// Adjust stack.
if (isInt<16>(-StackSize)) // addi sp, sp, (-stacksize)
BuildMI(MBB, MBBI, dl, TII.get(ADDiu), SP).addReg(SP).addImm(-StackSize);
else { // Expand immediate that doesn't fit in 16-bit.
MipsFI->setEmitNOAT();
expandLargeImm(SP, -StackSize, STI.isABI_N64(), TII, MBB, MBBI, dl);
}
// emit ".cfi_def_cfa_offset StackSize"
MCSymbol *AdjustSPLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, dl,
TII.get(TargetOpcode::PROLOG_LABEL)).addSym(AdjustSPLabel);
DstML = MachineLocation(MachineLocation::VirtualFP);
SrcML = MachineLocation(MachineLocation::VirtualFP, -StackSize);
Moves.push_back(MachineMove(AdjustSPLabel, DstML, SrcML));
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
if (CSI.size()) {
// Find the instruction past the last instruction that saves a callee-saved
// register to the stack.
for (unsigned i = 0; i < CSI.size(); ++i)
++MBBI;
// Iterate over list of callee-saved registers and emit .cfi_offset
// directives.
MCSymbol *CSLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, dl,
TII.get(TargetOpcode::PROLOG_LABEL)).addSym(CSLabel);
for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
E = CSI.end(); I != E; ++I) {
int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
unsigned Reg = I->getReg();
// If Reg is a double precision register, emit two cfa_offsets,
// one for each of the paired single precision registers.
if (Mips::AFGR64RegClass.contains(Reg)) {
const uint16_t *SubRegs = RegInfo->getSubRegisters(Reg);
MachineLocation DstML0(MachineLocation::VirtualFP, Offset);
MachineLocation DstML1(MachineLocation::VirtualFP, Offset + 4);
MachineLocation SrcML0(*SubRegs);
MachineLocation SrcML1(*(SubRegs + 1));
if (!STI.isLittle())
std::swap(SrcML0, SrcML1);
Moves.push_back(MachineMove(CSLabel, DstML0, SrcML0));
Moves.push_back(MachineMove(CSLabel, DstML1, SrcML1));
} else {
// Reg is either in CPURegs or FGR32.
DstML = MachineLocation(MachineLocation::VirtualFP, Offset);
SrcML = MachineLocation(Reg);
Moves.push_back(MachineMove(CSLabel, DstML, SrcML));
}
}
}
// if framepointer enabled, set it to point to the stack pointer.
if (hasFP(MF)) {
// Insert instruction "move $fp, $sp" at this location.
BuildMI(MBB, MBBI, dl, TII.get(ADDu), FP).addReg(SP).addReg(ZERO);
// emit ".cfi_def_cfa_register $fp"
MCSymbol *SetFPLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, dl,
TII.get(TargetOpcode::PROLOG_LABEL)).addSym(SetFPLabel);
DstML = MachineLocation(FP);
SrcML = MachineLocation(MachineLocation::VirtualFP);
Moves.push_back(MachineMove(SetFPLabel, DstML, SrcML));
}
// Restore GP from the saved stack location
if (MipsFI->needGPSaveRestore()) {
unsigned Offset = MFI->getObjectOffset(MipsFI->getGPFI());
BuildMI(MBB, MBBI, dl, TII.get(Mips::CPRESTORE)).addImm(Offset)
.addReg(Mips::GP);
}
}
void MipsFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
MachineFrameInfo *MFI = MF.getFrameInfo();
const MipsInstrInfo &TII =
*static_cast<const MipsInstrInfo*>(MF.getTarget().getInstrInfo());
DebugLoc dl = MBBI->getDebugLoc();
unsigned SP = STI.isABI_N64() ? Mips::SP_64 : Mips::SP;
unsigned FP = STI.isABI_N64() ? Mips::FP_64 : Mips::FP;
unsigned ZERO = STI.isABI_N64() ? Mips::ZERO_64 : Mips::ZERO;
unsigned ADDu = STI.isABI_N64() ? Mips::DADDu : Mips::ADDu;
unsigned ADDiu = STI.isABI_N64() ? Mips::DADDiu : Mips::ADDiu;
// if framepointer enabled, restore the stack pointer.
if (hasFP(MF)) {
// Find the first instruction that restores a callee-saved register.
MachineBasicBlock::iterator I = MBBI;
for (unsigned i = 0; i < MFI->getCalleeSavedInfo().size(); ++i)
--I;
// Insert instruction "move $sp, $fp" at this location.
BuildMI(MBB, I, dl, TII.get(ADDu), SP).addReg(FP).addReg(ZERO);
}
// Get the number of bytes from FrameInfo
uint64_t StackSize = MFI->getStackSize();
if (!StackSize)
return;
// Adjust stack.
if (isInt<16>(StackSize)) // addi sp, sp, (-stacksize)
BuildMI(MBB, MBBI, dl, TII.get(ADDiu), SP).addReg(SP).addImm(StackSize);
else // Expand immediate that doesn't fit in 16-bit.
expandLargeImm(SP, StackSize, STI.isABI_N64(), TII, MBB, MBBI, dl);
}
void MipsFrameLowering::
processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *RS) const {
MachineRegisterInfo& MRI = MF.getRegInfo();
unsigned FP = STI.isABI_N64() ? Mips::FP_64 : Mips::FP;
// FIXME: remove this code if register allocator can correctly mark
// $fp and $ra used or unused.
// Mark $fp and $ra as used or unused.
if (hasFP(MF))
MRI.setPhysRegUsed(FP);
// The register allocator might determine $ra is used after seeing
// instruction "jr $ra", but we do not want PrologEpilogInserter to insert
// instructions to save/restore $ra unless there is a function call.
// To correct this, $ra is explicitly marked unused if there is no
// function call.
if (MF.getFrameInfo()->hasCalls())
MRI.setPhysRegUsed(Mips::RA);
else {
MRI.setPhysRegUnused(Mips::RA);
MRI.setPhysRegUnused(Mips::RA_64);
}
}
Reference in New Issue View Git Blame Copy Permalink