Home | History | Annotate | Download | only in Blackfin 
      1 //====- BlackfinFrameLowering.cpp - Blackfin Frame Information --*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file contains the Blackfin implementation of TargetFrameLowering class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "BlackfinFrameLowering.h"
     15 #include "BlackfinInstrInfo.h"
     16 #include "llvm/CodeGen/MachineFrameInfo.h"
     17 #include "llvm/CodeGen/MachineFunction.h"
     18 #include "llvm/CodeGen/MachineInstrBuilder.h"
     19 #include "llvm/CodeGen/RegisterScavenging.h"
     20 #include "llvm/Target/TargetOptions.h"
     21 
     22 using namespace llvm;
     23 
     24 
     25 // hasFP - Return true if the specified function should have a dedicated frame
     26 // pointer register.  This is true if the function has variable sized allocas or
     27 // if frame pointer elimination is disabled.
     28 bool BlackfinFrameLowering::hasFP(const MachineFunction &MF) const {
     29   const MachineFrameInfo *MFI = MF.getFrameInfo();
     30   return DisableFramePointerElim(MF) ||
     31     MFI->adjustsStack() || MFI->hasVarSizedObjects();
     32 }
     33 
     34 // Always reserve a call frame. We dont have enough registers to adjust SP.
     35 bool BlackfinFrameLowering::
     36 hasReservedCallFrame(const MachineFunction &MF) const {
     37   return true;
     38 }
     39 
     40 // Emit a prologue that sets up a stack frame.
     41 // On function entry, R0-R2 and P0 may hold arguments.
     42 // R3, P1, and P2 may be used as scratch registers
     43 void BlackfinFrameLowering::emitPrologue(MachineFunction &MF) const {
     44   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
     45   MachineBasicBlock::iterator MBBI = MBB.begin();
     46   MachineFrameInfo *MFI = MF.getFrameInfo();
     47   const BlackfinRegisterInfo *RegInfo =
     48     static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
     49   const BlackfinInstrInfo &TII =
     50     *static_cast<const BlackfinInstrInfo*>(MF.getTarget().getInstrInfo());
     51 
     52   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
     53 
     54   int FrameSize = MFI->getStackSize();
     55   if (FrameSize%4) {
     56     FrameSize = (FrameSize+3) & ~3;
     57     MFI->setStackSize(FrameSize);
     58   }
     59 
     60   if (!hasFP(MF)) {
     61     assert(!MFI->adjustsStack() &&
     62            "FP elimination on a non-leaf function is not supported");
     63     RegInfo->adjustRegister(MBB, MBBI, dl, BF::SP, BF::P1, -FrameSize);
     64     return;
     65   }
     66 
     67   // emit a LINK instruction
     68   if (FrameSize <= 0x3ffff) {
     69     BuildMI(MBB, MBBI, dl, TII.get(BF::LINK)).addImm(FrameSize);
     70     return;
     71   }
     72 
     73   // Frame is too big, do a manual LINK:
     74   // [--SP] = RETS;
     75   // [--SP] = FP;
     76   // FP = SP;
     77   // P1 = -FrameSize;
     78   // SP = SP + P1;
     79   BuildMI(MBB, MBBI, dl, TII.get(BF::PUSH))
     80     .addReg(BF::RETS, RegState::Kill);
     81   BuildMI(MBB, MBBI, dl, TII.get(BF::PUSH))
     82     .addReg(BF::FP, RegState::Kill);
     83   BuildMI(MBB, MBBI, dl, TII.get(BF::MOVE), BF::FP)
     84     .addReg(BF::SP);
     85   RegInfo->loadConstant(MBB, MBBI, dl, BF::P1, -FrameSize);
     86   BuildMI(MBB, MBBI, dl, TII.get(BF::ADDpp), BF::SP)
     87     .addReg(BF::SP, RegState::Kill)
     88     .addReg(BF::P1, RegState::Kill);
     89 
     90 }
     91 
     92 void BlackfinFrameLowering::emitEpilogue(MachineFunction &MF,
     93                                      MachineBasicBlock &MBB) const {
     94   MachineFrameInfo *MFI = MF.getFrameInfo();
     95   const BlackfinRegisterInfo *RegInfo =
     96     static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
     97   const BlackfinInstrInfo &TII =
     98     *static_cast<const BlackfinInstrInfo*>(MF.getTarget().getInstrInfo());
     99   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
    100   DebugLoc dl = MBBI->getDebugLoc();
    101 
    102   int FrameSize = MFI->getStackSize();
    103   assert(FrameSize%4 == 0 && "Misaligned frame size");
    104 
    105   if (!hasFP(MF)) {
    106     assert(!MFI->adjustsStack() &&
    107            "FP elimination on a non-leaf function is not supported");
    108     RegInfo->adjustRegister(MBB, MBBI, dl, BF::SP, BF::P1, FrameSize);
    109     return;
    110   }
    111 
    112   // emit an UNLINK instruction
    113   BuildMI(MBB, MBBI, dl, TII.get(BF::UNLINK));
    114 }
    115 
    116 void BlackfinFrameLowering::
    117 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
    118                                      RegScavenger *RS) const {
    119   MachineFrameInfo *MFI = MF.getFrameInfo();
    120   const BlackfinRegisterInfo *RegInfo =
    121     static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
    122   const TargetRegisterClass *RC = BF::DPRegisterClass;
    123 
    124   if (RegInfo->requiresRegisterScavenging(MF)) {
    125     // Reserve a slot close to SP or frame pointer.
    126     RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
    127                                                        RC->getAlignment(),
    128                                                        false));
    129   }
    130 }
    131