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 // 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 }