| //===-- MipsFrameLowering.cpp - Mips Frame Information --------------------===// |
| // |
| // 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 Mips implementation of TargetFrameLowering class. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "MipsFrameLowering.h" |
| #include "MipsAnalyzeImmediate.h" |
| #include "MipsInstrInfo.h" |
| #include "MipsMachineFunction.h" |
| #include "MCTargetDesc/MipsBaseInfo.h" |
| #include "llvm/Function.h" |
| #include "llvm/CodeGen/MachineFrameInfo.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/MachineModuleInfo.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Target/TargetOptions.h" |
| #include "llvm/Support/CommandLine.h" |
| |
| using namespace llvm; |
| |
| |
| //===----------------------------------------------------------------------===// |
| // |
| // Stack Frame Processing methods |
| // +----------------------------+ |
| // |
| // The stack is allocated decrementing the stack pointer on |
| // the first instruction of a function prologue. Once decremented, |
| // all stack references are done thought a positive offset |
| // from the stack/frame pointer, so the stack is considering |
| // to grow up! Otherwise terrible hacks would have to be made |
| // to get this stack ABI compliant :) |
| // |
| // The stack frame required by the ABI (after call): |
| // Offset |
| // |
| // 0 ---------- |
| // 4 Args to pass |
| // . saved $GP (used in PIC) |
| // . Alloca allocations |
| // . Local Area |
| // . CPU "Callee Saved" Registers |
| // . saved FP |
| // . saved RA |
| // . FPU "Callee Saved" Registers |
| // StackSize ----------- |
| // |
| // Offset - offset from sp after stack allocation on function prologue |
| // |
| // The sp is the stack pointer subtracted/added from the stack size |
| // at the Prologue/Epilogue |
| // |
| // References to the previous stack (to obtain arguments) are done |
| // with offsets that exceeds the stack size: (stacksize+(4*(num_arg-1)) |
| // |
| // Examples: |
| // - reference to the actual stack frame |
| // for any local area var there is smt like : FI >= 0, StackOffset: 4 |
| // sw REGX, 4(SP) |
| // |
| // - reference to previous stack frame |
| // suppose there's a load to the 5th arguments : FI < 0, StackOffset: 16. |
| // The emitted instruction will be something like: |
| // lw REGX, 16+StackSize(SP) |
| // |
| // Since the total stack size is unknown on LowerFormalArguments, all |
| // stack references (ObjectOffset) created to reference the function |
| // arguments, are negative numbers. This way, on eliminateFrameIndex it's |
| // possible to detect those references and the offsets are adjusted to |
| // their real location. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| // 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 MipsFrameLowering::hasFP(const MachineFunction &MF) const { |
| const MachineFrameInfo *MFI = MF.getFrameInfo(); |
| return MF.getTarget().Options.DisableFramePointerElim(MF) || |
| MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken(); |
| } |