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//====- BlackfinFrameLowering.cpp - Blackfin Frame Information --*- C++ -*-===//
//
// 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 Blackfin implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "BlackfinFrameLowering.h"
#include "BlackfinInstrInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
// 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 BlackfinFrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
return DisableFramePointerElim(MF) ||
MFI->adjustsStack() || MFI->hasVarSizedObjects();
}
// Always reserve a call frame. We dont have enough registers to adjust SP.
bool BlackfinFrameLowering::
hasReservedCallFrame(const MachineFunction &MF) const {
return true;
}
// Emit a prologue that sets up a stack frame.
// On function entry, R0-R2 and P0 may hold arguments.
// R3, P1, and P2 may be used as scratch registers
void BlackfinFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
const BlackfinRegisterInfo *RegInfo =
static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
const BlackfinInstrInfo &TII =
*static_cast<const BlackfinInstrInfo*>(MF.getTarget().getInstrInfo());
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
int FrameSize = MFI->getStackSize();
if (FrameSize%4) {
FrameSize = (FrameSize+3) & ~3;
MFI->setStackSize(FrameSize);
}
if (!hasFP(MF)) {
assert(!MFI->adjustsStack() &&
"FP elimination on a non-leaf function is not supported");
RegInfo->adjustRegister(MBB, MBBI, dl, BF::SP, BF::P1, -FrameSize);
return;
}
// emit a LINK instruction
if (FrameSize <= 0x3ffff) {
BuildMI(MBB, MBBI, dl, TII.get(BF::LINK)).addImm(FrameSize);
return;
}
// Frame is too big, do a manual LINK:
// [--SP] = RETS;
// [--SP] = FP;
// FP = SP;
// P1 = -FrameSize;
// SP = SP + P1;
BuildMI(MBB, MBBI, dl, TII.get(BF::PUSH))
.addReg(BF::RETS, RegState::Kill);
BuildMI(MBB, MBBI, dl, TII.get(BF::PUSH))
.addReg(BF::FP, RegState::Kill);
BuildMI(MBB, MBBI, dl, TII.get(BF::MOVE), BF::FP)
.addReg(BF::SP);
RegInfo->loadConstant(MBB, MBBI, dl, BF::P1, -FrameSize);
BuildMI(MBB, MBBI, dl, TII.get(BF::ADDpp), BF::SP)
.addReg(BF::SP, RegState::Kill)
.addReg(BF::P1, RegState::Kill);
}
void BlackfinFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineFrameInfo *MFI = MF.getFrameInfo();
const BlackfinRegisterInfo *RegInfo =
static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
const BlackfinInstrInfo &TII =
*static_cast<const BlackfinInstrInfo*>(MF.getTarget().getInstrInfo());
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
DebugLoc dl = MBBI->getDebugLoc();
int FrameSize = MFI->getStackSize();
assert(FrameSize%4 == 0 && "Misaligned frame size");
if (!hasFP(MF)) {
assert(!MFI->adjustsStack() &&
"FP elimination on a non-leaf function is not supported");
RegInfo->adjustRegister(MBB, MBBI, dl, BF::SP, BF::P1, FrameSize);
return;
}
// emit an UNLINK instruction
BuildMI(MBB, MBBI, dl, TII.get(BF::UNLINK));
}
void BlackfinFrameLowering::
processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *RS) const {
MachineFrameInfo *MFI = MF.getFrameInfo();
const BlackfinRegisterInfo *RegInfo =
static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
const TargetRegisterClass *RC = BF::DPRegisterClass;
if (RegInfo->requiresRegisterScavenging(MF)) {
// Reserve a slot close to SP or frame pointer.
RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
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