lib/Target/Blackfin/BlackfinFrameLowering.cpp

   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 // Emit a prologue that sets up a stack frame.
  35 // On function entry, R0-R2 and P0 may hold arguments.
  36 // R3, P1, and P2 may be used as scratch registers
  37 void BlackfinFrameLowering::emitPrologue(MachineFunction &MF) const {
  38   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
  39   MachineBasicBlock::iterator MBBI = MBB.begin();
  40   MachineFrameInfo *MFI = MF.getFrameInfo();
  41   const BlackfinRegisterInfo *RegInfo =
  42     static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
  43   const BlackfinInstrInfo &TII =
  44     *static_cast<const BlackfinInstrInfo*>(MF.getTarget().getInstrInfo());
  45
  46   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
  47
  48   int FrameSize = MFI->getStackSize();
  49   if (FrameSize%4) {
  50     FrameSize = (FrameSize+3) & ~3;
  51     MFI->setStackSize(FrameSize);
  52   }
  53
  54   if (!hasFP(MF)) {
  55     assert(!MFI->adjustsStack() &&
  56            "FP elimination on a non-leaf function is not supported");
  57     RegInfo->adjustRegister(MBB, MBBI, dl, BF::SP, BF::P1, -FrameSize);
  58     return;
  59   }
  60
  61   // emit a LINK instruction
  62   if (FrameSize <= 0x3ffff) {
  63     BuildMI(MBB, MBBI, dl, TII.get(BF::LINK)).addImm(FrameSize);
  64     return;
  65   }
  66
  67   // Frame is too big, do a manual LINK:
  68   // [--SP] = RETS;
  69   // [--SP] = FP;
  70   // FP = SP;
  71   // P1 = -FrameSize;
  72   // SP = SP + P1;
  73   BuildMI(MBB, MBBI, dl, TII.get(BF::PUSH))
  74     .addReg(BF::RETS, RegState::Kill);
  75   BuildMI(MBB, MBBI, dl, TII.get(BF::PUSH))
  76     .addReg(BF::FP, RegState::Kill);
  77   BuildMI(MBB, MBBI, dl, TII.get(BF::MOVE), BF::FP)
  78     .addReg(BF::SP);
  79   RegInfo->loadConstant(MBB, MBBI, dl, BF::P1, -FrameSize);
  80   BuildMI(MBB, MBBI, dl, TII.get(BF::ADDpp), BF::SP)
  81     .addReg(BF::SP, RegState::Kill)
  82     .addReg(BF::P1, RegState::Kill);
  83
  84 }
  85
  86 void BlackfinFrameLowering::emitEpilogue(MachineFunction &MF,
  87                                      MachineBasicBlock &MBB) const {
  88   MachineFrameInfo *MFI = MF.getFrameInfo();
  89   const BlackfinRegisterInfo *RegInfo =
  90     static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
  91   const BlackfinInstrInfo &TII =
  92     *static_cast<const BlackfinInstrInfo*>(MF.getTarget().getInstrInfo());
  93   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
  94   DebugLoc dl = MBBI->getDebugLoc();
  95
  96   int FrameSize = MFI->getStackSize();
  97   assert(FrameSize%4 == 0 && "Misaligned frame size");
  98
  99   if (!hasFP(MF)) {
 100     assert(!MFI->adjustsStack() &&
 101            "FP elimination on a non-leaf function is not supported");
 102     RegInfo->adjustRegister(MBB, MBBI, dl, BF::SP, BF::P1, FrameSize);
 103     return;
 104   }
 105
 106   // emit an UNLINK instruction
 107   BuildMI(MBB, MBBI, dl, TII.get(BF::UNLINK));
 108 }
 109
 110 void BlackfinFrameLowering::
 111 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
 112                                      RegScavenger *RS) const {
 113   MachineFrameInfo *MFI = MF.getFrameInfo();
 114   const BlackfinRegisterInfo *RegInfo =
 115     static_cast<const BlackfinRegisterInfo*>(MF.getTarget().getRegisterInfo());
 116   const TargetRegisterClass *RC = BF::DPRegisterClass;
 117
 118   if (RegInfo->requiresRegisterScavenging(MF)) {
 119     // Reserve a slot close to SP or frame pointer.
 120     RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
 121                                                        RC->getAlignment(),
 122                                                        false));
 123   }
 124 }