caio/clang-p2996
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
8fcb1263f42657ecbc355beff12500dfbcddee17
clang-p2996/llvm/lib/Target/Mips/Mips16InstrInfo.cpp
Venkata Ramanaiah Nalamothu f7d8336a2f [llvm] Pass MachineInstr flags to storeRegToStackSlot/loadRegFromStackSlot (NFC) (#120622) 
This patch is in preparation to enable setting the MachineInstr::MIFlag
flags, i.e. FrameSetup/FrameDestroy, on callee saved register
spill/reload instructions in prologue/epilogue. This eventually helps in
setting the prologue_end and epilogue_begin markers more accurately.

The DWARF Spec in "6.4 Call Frame Information" says:

The code that allocates space on the call frame stack and performs the
save
operation is called the subroutine’s prologue, and the code that
performs
the restore operation and deallocates the frame is called its epilogue.

which means the callee saved register spills and reloads are part of
prologue (a.k.a frame setup) and epilogue (a.k.a frame destruction),
respectively. And, IIUC, LLVM backend uses FrameSetup/FrameDestroy flags
to identify instructions that are part of call frame setup and
destruction.

In the trunk, while most targets consistently set
FrameSetup/FrameDestroy on save/restore call frame information (CFI)
instructions of callee saved registers, they do not consistently set
those flags on the actual callee saved register spill/reload
instructions.

I believe this patch provides a clean mechanism to set
FrameSetup/FrameDestroy flags on the actual callee saved register
spill/reload instructions as needed. And, by having default argument of
MachineInstr::NoFlags for Flags, this patch is a NFC.

With this patch, the targets have to just pass FrameSetup/FrameDestroy
flag to the storeRegToStackSlot/loadRegFromStackSlot calls from the
target derived spillCalleeSavedRegisters and restoreCalleeSavedRegisters
to set those flags on callee saved register spill/reload instructions.

Also, this patch makes it very easy to set the source line information
on callee saved register spill/reload instructions which is needed by
the DwarfDebug.cpp implementation to set prologue_end and epilogue_begin
markers more accurately.

As per DwarfDebug.cpp implementation:

prologue_end is the first known non-DBG_VALUE and non-FrameSetup
location
    that marks the beginning of the function body

epilogue_begin is the first FrameDestroy location that has been seen in
the
    epilogue basic block

With this patch, the targets have to just do the following to set the
source line information on callee saved register spill/reload
instructions, without hampering the LLVM's efforts to avoid adding
source line information on the artificial code generated by the
compiler.

    <Foo>InstrInfo::storeRegToStackSlot() {
    ...
      DebugLoc DL =
Flags & MachineInstr::FrameSetup ? DebugLoc() : MBB.findDebugLoc(I);
    ...
    }

    <Foo>InstrInfo::loadRegFromStackSlot() {
    ...
      DebugLoc DL =
Flags & MachineInstr::FrameDestroy ? MBB.findDebugLoc(I) : DebugLoc();
    ...
    }

While I understand this patch would break out-of-tree backend builds, I
think it is in the right direction.

One immediate use case that can benefit from this patch is fixing
#120553 becomes simpler.
2025-01-22 13:36:39 +05:30

488 lines
18 KiB
C++
Raw Blame History

//===- Mips16InstrInfo.cpp - Mips16 Instruction Information ---------------===//
//
// 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 the Mips16 implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//
#include "Mips16InstrInfo.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include <cassert>
#include <cctype>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <iterator>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "mips16-instrinfo"
Mips16InstrInfo::Mips16InstrInfo(const MipsSubtarget &STI)
: MipsInstrInfo(STI, Mips::Bimm16) {}
const MipsRegisterInfo &Mips16InstrInfo::getRegisterInfo() const {
return RI;
}
/// isLoadFromStackSlot - If the specified machine instruction is a direct
/// load from a stack slot, return the virtual or physical register number of
/// the destination along with the FrameIndex of the loaded stack slot. If
/// not, return 0. This predicate must return 0 if the instruction has
/// any side effects other than loading from the stack slot.
Register Mips16InstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
int &FrameIndex) const {
return 0;
}
/// isStoreToStackSlot - If the specified machine instruction is a direct
/// store to a stack slot, return the virtual or physical register number of
/// the source reg along with the FrameIndex of the loaded stack slot. If
/// not, return 0. This predicate must return 0 if the instruction has
/// any side effects other than storing to the stack slot.
Register Mips16InstrInfo::isStoreToStackSlot(const MachineInstr &MI,
int &FrameIndex) const {
return 0;
}
void Mips16InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
const DebugLoc &DL, MCRegister DestReg,
MCRegister SrcReg, bool KillSrc,
bool RenamableDest, bool RenamableSrc) const {
unsigned Opc = 0;
if (Mips::CPU16RegsRegClass.contains(DestReg) &&
Mips::GPR32RegClass.contains(SrcReg))
Opc = Mips::MoveR3216;
else if (Mips::GPR32RegClass.contains(DestReg) &&
Mips::CPU16RegsRegClass.contains(SrcReg))
Opc = Mips::Move32R16;
else if ((SrcReg == Mips::HI0) &&
(Mips::CPU16RegsRegClass.contains(DestReg)))
Opc = Mips::Mfhi16, SrcReg = 0;
else if ((SrcReg == Mips::LO0) &&
(Mips::CPU16RegsRegClass.contains(DestReg)))
Opc = Mips::Mflo16, SrcReg = 0;
assert(Opc && "Cannot copy registers");
MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(Opc));
if (DestReg)
MIB.addReg(DestReg, RegState::Define);
if (SrcReg)
MIB.addReg(SrcReg, getKillRegState(KillSrc));
}
std::optional<DestSourcePair>
Mips16InstrInfo::isCopyInstrImpl(const MachineInstr &MI) const {
if (MI.isMoveReg())
return DestSourcePair{MI.getOperand(0), MI.getOperand(1)};
return std::nullopt;
}
void Mips16InstrInfo::storeRegToStack(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
Register SrcReg, bool isKill, int FI,
const TargetRegisterClass *RC,
const TargetRegisterInfo *TRI,
int64_t Offset,
MachineInstr::MIFlag Flags) const {
DebugLoc DL;
if (I != MBB.end()) DL = I->getDebugLoc();
MachineMemOperand *MMO = GetMemOperand(MBB, FI, MachineMemOperand::MOStore);
unsigned Opc = 0;
if (Mips::CPU16RegsRegClass.hasSubClassEq(RC))
Opc = Mips::SwRxSpImmX16;
assert(Opc && "Register class not handled!");
BuildMI(MBB, I, DL, get(Opc)).addReg(SrcReg, getKillRegState(isKill)).
addFrameIndex(FI).addImm(Offset)
.addMemOperand(MMO);
}
void Mips16InstrInfo::loadRegFromStack(
MachineBasicBlock &MBB, MachineBasicBlock::iterator I, Register DestReg,
int FI, const TargetRegisterClass *RC, const TargetRegisterInfo *TRI,
int64_t Offset, MachineInstr::MIFlag Flags) const {
DebugLoc DL;
if (I != MBB.end()) DL = I->getDebugLoc();
MachineMemOperand *MMO = GetMemOperand(MBB, FI, MachineMemOperand::MOLoad);
unsigned Opc = 0;
if (Mips::CPU16RegsRegClass.hasSubClassEq(RC))
Opc = Mips::LwRxSpImmX16;
assert(Opc && "Register class not handled!");
BuildMI(MBB, I, DL, get(Opc), DestReg).addFrameIndex(FI).addImm(Offset)
.addMemOperand(MMO);
}
bool Mips16InstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
MachineBasicBlock &MBB = *MI.getParent();
switch (MI.getDesc().getOpcode()) {
default:
return false;
case Mips::RetRA16:
ExpandRetRA16(MBB, MI, Mips::JrcRa16);
break;
}
MBB.erase(MI.getIterator());
return true;
}
/// GetOppositeBranchOpc - Return the inverse of the specified
/// opcode, e.g. turning BEQ to BNE.
unsigned Mips16InstrInfo::getOppositeBranchOpc(unsigned Opc) const {
switch (Opc) {
case Mips::BeqzRxImmX16: return Mips::BnezRxImmX16;
case Mips::BnezRxImmX16: return Mips::BeqzRxImmX16;
case Mips::BeqzRxImm16: return Mips::BnezRxImm16;
case Mips::BnezRxImm16: return Mips::BeqzRxImm16;
case Mips::BteqzT8CmpX16: return Mips::BtnezT8CmpX16;
case Mips::BteqzT8SltX16: return Mips::BtnezT8SltX16;
case Mips::BteqzT8SltiX16: return Mips::BtnezT8SltiX16;
case Mips::Btnez16: return Mips::Bteqz16;
case Mips::BtnezX16: return Mips::BteqzX16;
case Mips::BtnezT8CmpiX16: return Mips::BteqzT8CmpiX16;
case Mips::BtnezT8SltuX16: return Mips::BteqzT8SltuX16;
case Mips::BtnezT8SltiuX16: return Mips::BteqzT8SltiuX16;
case Mips::Bteqz16: return Mips::Btnez16;
case Mips::BteqzX16: return Mips::BtnezX16;
case Mips::BteqzT8CmpiX16: return Mips::BtnezT8CmpiX16;
case Mips::BteqzT8SltuX16: return Mips::BtnezT8SltuX16;
case Mips::BteqzT8SltiuX16: return Mips::BtnezT8SltiuX16;
case Mips::BtnezT8CmpX16: return Mips::BteqzT8CmpX16;
case Mips::BtnezT8SltX16: return Mips::BteqzT8SltX16;
case Mips::BtnezT8SltiX16: return Mips::BteqzT8SltiX16;
}
llvm_unreachable("Illegal opcode!");
}
static void addSaveRestoreRegs(MachineInstrBuilder &MIB,
ArrayRef<CalleeSavedInfo> CSI,
unsigned Flags = 0) {
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
// Add the callee-saved register as live-in. Do not add if the register is
// RA and return address is taken, because it has already been added in
// method MipsTargetLowering::lowerRETURNADDR.
// It's killed at the spill, unless the register is RA and return address
// is taken.
Register Reg = CSI[e-i-1].getReg();
switch (Reg) {
case Mips::RA:
case Mips::S0:
case Mips::S1:
MIB.addReg(Reg, Flags);
break;
case Mips::S2:
break;
default:
llvm_unreachable("unexpected mips16 callee saved register");
}
}
}
// Adjust SP by FrameSize bytes. Save RA, S0, S1
void Mips16InstrInfo::makeFrame(unsigned SP, int64_t FrameSize,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
DebugLoc DL;
MachineFunction &MF = *MBB.getParent();
MachineFrameInfo &MFI = MF.getFrameInfo();
const BitVector Reserved = RI.getReservedRegs(MF);
bool SaveS2 = Reserved[Mips::S2];
MachineInstrBuilder MIB;
unsigned Opc = ((FrameSize <= 128) && !SaveS2)? Mips::Save16:Mips::SaveX16;
MIB = BuildMI(MBB, I, DL, get(Opc));
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
addSaveRestoreRegs(MIB, CSI);
if (SaveS2)
MIB.addReg(Mips::S2);
if (isUInt<11>(FrameSize))
MIB.addImm(FrameSize);
else {
int Base = 2040; // should create template function like isUInt that
// returns largest possible n bit unsigned integer
int64_t Remainder = FrameSize - Base;
MIB.addImm(Base);
if (isInt<16>(-Remainder))
BuildAddiuSpImm(MBB, I, -Remainder);
else
adjustStackPtrBig(SP, -Remainder, MBB, I, Mips::V0, Mips::V1);
}
}
// Adjust SP by FrameSize bytes. Restore RA, S0, S1
void Mips16InstrInfo::restoreFrame(unsigned SP, int64_t FrameSize,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
DebugLoc DL = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
MachineFunction *MF = MBB.getParent();
MachineFrameInfo &MFI = MF->getFrameInfo();
const BitVector Reserved = RI.getReservedRegs(*MF);
bool SaveS2 = Reserved[Mips::S2];
MachineInstrBuilder MIB;
unsigned Opc = ((FrameSize <= 128) && !SaveS2)?
Mips::Restore16:Mips::RestoreX16;
if (!isUInt<11>(FrameSize)) {
unsigned Base = 2040;
int64_t Remainder = FrameSize - Base;
FrameSize = Base; // should create template function like isUInt that
// returns largest possible n bit unsigned integer
if (isInt<16>(Remainder))
BuildAddiuSpImm(MBB, I, Remainder);
else
adjustStackPtrBig(SP, Remainder, MBB, I, Mips::A0, Mips::A1);
}
MIB = BuildMI(MBB, I, DL, get(Opc));
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
addSaveRestoreRegs(MIB, CSI, RegState::Define);
if (SaveS2)
MIB.addReg(Mips::S2, RegState::Define);
MIB.addImm(FrameSize);
}
// Adjust SP by Amount bytes where bytes can be up to 32bit number.
// This can only be called at times that we know that there is at least one free
// register.
// This is clearly safe at prologue and epilogue.
void Mips16InstrInfo::adjustStackPtrBig(unsigned SP, int64_t Amount,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
unsigned Reg1, unsigned Reg2) const {
DebugLoc DL;
//
// li reg1, constant
// move reg2, sp
// add reg1, reg1, reg2
// move sp, reg1
//
//
MachineInstrBuilder MIB1 = BuildMI(MBB, I, DL, get(Mips::LwConstant32), Reg1);
MIB1.addImm(Amount).addImm(-1);
MachineInstrBuilder MIB2 = BuildMI(MBB, I, DL, get(Mips::MoveR3216), Reg2);
MIB2.addReg(Mips::SP, RegState::Kill);
MachineInstrBuilder MIB3 = BuildMI(MBB, I, DL, get(Mips::AdduRxRyRz16), Reg1);
MIB3.addReg(Reg1);
MIB3.addReg(Reg2, RegState::Kill);
MachineInstrBuilder MIB4 = BuildMI(MBB, I, DL, get(Mips::Move32R16),
Mips::SP);
MIB4.addReg(Reg1, RegState::Kill);
}
void Mips16InstrInfo::adjustStackPtrBigUnrestricted(
unsigned SP, int64_t Amount, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
llvm_unreachable("adjust stack pointer amount exceeded");
}
/// Adjust SP by Amount bytes.
void Mips16InstrInfo::adjustStackPtr(unsigned SP, int64_t Amount,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
if (Amount == 0)
return;
if (isInt<16>(Amount)) // need to change to addiu sp, ....and isInt<16>
BuildAddiuSpImm(MBB, I, Amount);
else
adjustStackPtrBigUnrestricted(SP, Amount, MBB, I);
}
/// This function generates the sequence of instructions needed to get the
/// result of adding register REG and immediate IMM.
unsigned Mips16InstrInfo::loadImmediate(unsigned FrameReg, int64_t Imm,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator II,
const DebugLoc &DL,
unsigned &NewImm) const {
//
// given original instruction is:
// Instr rx, T[offset] where offset is too big.
//
// lo = offset & 0xFFFF
// hi = ((offset >> 16) + (lo >> 15)) & 0xFFFF;
//
// let T = temporary register
// li T, hi
// shl T, 16
// add T, Rx, T
//
RegScavenger rs;
int32_t lo = Imm & 0xFFFF;
NewImm = lo;
int Reg =0;
int SpReg = 0;
rs.enterBasicBlockEnd(MBB);
rs.backward(std::next(II));
//
// We need to know which registers can be used, in the case where there
// are not enough free registers. We exclude all registers that
// are used in the instruction that we are helping.
// // Consider all allocatable registers in the register class initially
BitVector Candidates =
RI.getAllocatableSet
(*II->getParent()->getParent(), &Mips::CPU16RegsRegClass);
// Exclude all the registers being used by the instruction.
for (MachineOperand &MO : II->operands()) {
if (MO.isReg() && MO.getReg() != 0 && !MO.isDef() &&
!MO.getReg().isVirtual())
Candidates.reset(MO.getReg());
}
// If the same register was used and defined in an instruction, then
// it will not be in the list of candidates.
//
// we need to analyze the instruction that we are helping.
// we need to know if it defines register x but register x is not
// present as an operand of the instruction. this tells
// whether the register is live before the instruction. if it's not
// then we don't need to save it in case there are no free registers.
int DefReg = 0;
for (MachineOperand &MO : II->operands()) {
if (MO.isReg() && MO.isDef()) {
DefReg = MO.getReg();
break;
}
}
BitVector Available = rs.getRegsAvailable(&Mips::CPU16RegsRegClass);
Available &= Candidates;
//
// we use T0 for the first register, if we need to save something away.
// we use T1 for the second register, if we need to save something away.
//
unsigned FirstRegSaved =0, SecondRegSaved=0;
unsigned FirstRegSavedTo = 0, SecondRegSavedTo = 0;
Reg = Available.find_first();
if (Reg == -1) {
Reg = Candidates.find_first();
Candidates.reset(Reg);
if (DefReg != Reg) {
FirstRegSaved = Reg;
FirstRegSavedTo = Mips::T0;
copyPhysReg(MBB, II, DL, FirstRegSavedTo, FirstRegSaved, true);
}
}
else
Available.reset(Reg);
BuildMI(MBB, II, DL, get(Mips::LwConstant32), Reg).addImm(Imm).addImm(-1);
NewImm = 0;
if (FrameReg == Mips::SP) {
SpReg = Available.find_first();
if (SpReg == -1) {
SpReg = Candidates.find_first();
// Candidates.reset(SpReg); // not really needed
if (DefReg!= SpReg) {
SecondRegSaved = SpReg;
SecondRegSavedTo = Mips::T1;
}
if (SecondRegSaved)
copyPhysReg(MBB, II, DL, SecondRegSavedTo, SecondRegSaved, true);
}
else
Available.reset(SpReg);
copyPhysReg(MBB, II, DL, SpReg, Mips::SP, false);
BuildMI(MBB, II, DL, get(Mips::AdduRxRyRz16), Reg)
.addReg(SpReg, RegState::Kill)
.addReg(Reg);
}
else
BuildMI(MBB, II, DL, get(Mips:: AdduRxRyRz16), Reg).addReg(FrameReg)
.addReg(Reg, RegState::Kill);
if (FirstRegSaved || SecondRegSaved) {
II = std::next(II);
if (FirstRegSaved)
copyPhysReg(MBB, II, DL, FirstRegSaved, FirstRegSavedTo, true);
if (SecondRegSaved)
copyPhysReg(MBB, II, DL, SecondRegSaved, SecondRegSavedTo, true);
}
return Reg;
}
unsigned Mips16InstrInfo::getAnalyzableBrOpc(unsigned Opc) const {
return (Opc == Mips::BeqzRxImmX16 || Opc == Mips::BimmX16 ||
Opc == Mips::Bimm16 ||
Opc == Mips::Bteqz16 || Opc == Mips::Btnez16 ||
Opc == Mips::BeqzRxImm16 || Opc == Mips::BnezRxImm16 ||
Opc == Mips::BnezRxImmX16 || Opc == Mips::BteqzX16 ||
Opc == Mips::BteqzT8CmpX16 || Opc == Mips::BteqzT8CmpiX16 ||
Opc == Mips::BteqzT8SltX16 || Opc == Mips::BteqzT8SltuX16 ||
Opc == Mips::BteqzT8SltiX16 || Opc == Mips::BteqzT8SltiuX16 ||
Opc == Mips::BtnezX16 || Opc == Mips::BtnezT8CmpX16 ||
Opc == Mips::BtnezT8CmpiX16 || Opc == Mips::BtnezT8SltX16 ||
Opc == Mips::BtnezT8SltuX16 || Opc == Mips::BtnezT8SltiX16 ||
Opc == Mips::BtnezT8SltiuX16 ) ? Opc : 0;
}
void Mips16InstrInfo::ExpandRetRA16(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
unsigned Opc) const {
BuildMI(MBB, I, I->getDebugLoc(), get(Opc));
}
const MCInstrDesc &Mips16InstrInfo::AddiuSpImm(int64_t Imm) const {
if (validSpImm8(Imm))
return get(Mips::AddiuSpImm16);
else
return get(Mips::AddiuSpImmX16);
}
void Mips16InstrInfo::BuildAddiuSpImm
(MachineBasicBlock &MBB, MachineBasicBlock::iterator I, int64_t Imm) const {
DebugLoc DL;
BuildMI(MBB, I, DL, AddiuSpImm(Imm)).addImm(Imm);
}
const MipsInstrInfo *llvm::createMips16InstrInfo(const MipsSubtarget &STI) {
return new Mips16InstrInfo(STI);
}
bool Mips16InstrInfo::validImmediate(unsigned Opcode, unsigned Reg,
int64_t Amount) {
switch (Opcode) {
case Mips::LbRxRyOffMemX16:
case Mips::LbuRxRyOffMemX16:
case Mips::LhRxRyOffMemX16:
case Mips::LhuRxRyOffMemX16:
case Mips::SbRxRyOffMemX16:
case Mips::ShRxRyOffMemX16:
case Mips::LwRxRyOffMemX16:
case Mips::SwRxRyOffMemX16:
case Mips::SwRxSpImmX16:
case Mips::LwRxSpImmX16:
return isInt<16>(Amount);
case Mips::AddiuRxRyOffMemX16:
if ((Reg == Mips::PC) || (Reg == Mips::SP))
return isInt<16>(Amount);
return isInt<15>(Amount);
}
llvm_unreachable("unexpected Opcode in validImmediate");
}
Reference in New Issue View Git Blame Copy Permalink