2012-02-17 16:55:11 +08:00
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//===-- MipsFrameLowering.cpp - Mips Frame Information --------------------===//
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2010-11-15 08:06:54 +08:00
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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2011-04-16 05:51:11 +08:00
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//===----------------------------------------------------------------------===//
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2010-11-15 08:06:54 +08:00
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//
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2011-01-10 20:39:04 +08:00
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// This file contains the Mips implementation of TargetFrameLowering class.
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2010-11-15 08:06:54 +08:00
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//
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2011-04-16 05:51:11 +08:00
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//===----------------------------------------------------------------------===//
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2010-11-15 08:06:54 +08:00
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2011-01-10 20:39:04 +08:00
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#include "MipsFrameLowering.h"
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2012-12-04 00:50:05 +08:00
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#include "MCTargetDesc/MipsBaseInfo.h"
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2010-11-15 08:06:54 +08:00
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#include "MipsInstrInfo.h"
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#include "MipsMachineFunction.h"
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2012-08-03 02:21:47 +08:00
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#include "MipsTargetMachine.h"
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2010-11-15 08:06:54 +08:00
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Function.h"
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2012-12-04 00:50:05 +08:00
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#include "llvm/Target/TargetOptions.h"
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2010-11-15 08:06:54 +08:00
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using namespace llvm;
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2011-04-16 05:51:11 +08:00
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//===----------------------------------------------------------------------===//
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2010-11-15 08:06:54 +08:00
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//
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// Stack Frame Processing methods
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// +----------------------------+
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//
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// The stack is allocated decrementing the stack pointer on
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// the first instruction of a function prologue. Once decremented,
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// all stack references are done thought a positive offset
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// from the stack/frame pointer, so the stack is considering
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// to grow up! Otherwise terrible hacks would have to be made
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// to get this stack ABI compliant :)
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//
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// The stack frame required by the ABI (after call):
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// Offset
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//
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// 0 ----------
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// 4 Args to pass
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// . saved $GP (used in PIC)
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// . Alloca allocations
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// . Local Area
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// . CPU "Callee Saved" Registers
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// . saved FP
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// . saved RA
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// . FPU "Callee Saved" Registers
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// StackSize -----------
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//
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// Offset - offset from sp after stack allocation on function prologue
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//
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// The sp is the stack pointer subtracted/added from the stack size
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// at the Prologue/Epilogue
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//
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// References to the previous stack (to obtain arguments) are done
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// with offsets that exceeds the stack size: (stacksize+(4*(num_arg-1))
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//
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// Examples:
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// - reference to the actual stack frame
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// for any local area var there is smt like : FI >= 0, StackOffset: 4
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// sw REGX, 4(SP)
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//
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// - reference to previous stack frame
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// suppose there's a load to the 5th arguments : FI < 0, StackOffset: 16.
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// The emitted instruction will be something like:
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// lw REGX, 16+StackSize(SP)
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//
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// Since the total stack size is unknown on LowerFormalArguments, all
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// stack references (ObjectOffset) created to reference the function
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// arguments, are negative numbers. This way, on eliminateFrameIndex it's
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// possible to detect those references and the offsets are adjusted to
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// their real location.
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//
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2011-04-16 05:51:11 +08:00
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//===----------------------------------------------------------------------===//
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2010-11-15 08:06:54 +08:00
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2014-07-19 07:33:47 +08:00
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const MipsFrameLowering *MipsFrameLowering::create(const MipsSubtarget &ST) {
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if (ST.inMips16Mode())
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2012-08-03 02:21:47 +08:00
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return llvm::createMips16FrameLowering(ST);
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return llvm::createMipsSEFrameLowering(ST);
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}
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2010-11-19 05:19:35 +08:00
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// hasFP - Return true if the specified function should have a dedicated frame
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2015-06-02 21:14:46 +08:00
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// pointer register. This is true if the function has variable sized allocas,
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// if it needs dynamic stack realignment, if frame pointer elimination is
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// disabled, or if the frame address is taken.
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2011-01-10 20:39:04 +08:00
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bool MipsFrameLowering::hasFP(const MachineFunction &MF) const {
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2016-07-29 02:40:00 +08:00
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const MachineFrameInfo &MFI = MF.getFrameInfo();
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2015-06-02 21:14:46 +08:00
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const TargetRegisterInfo *TRI = STI.getRegisterInfo();
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2011-12-03 06:16:29 +08:00
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return MF.getTarget().Options.DisableFramePointerElim(MF) ||
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2016-07-29 02:40:00 +08:00
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MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken() ||
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2015-06-02 21:14:46 +08:00
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TRI->needsStackRealignment(MF);
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}
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bool MipsFrameLowering::hasBP(const MachineFunction &MF) const {
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2016-07-29 02:40:00 +08:00
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const MachineFrameInfo &MFI = MF.getFrameInfo();
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2015-06-02 21:14:46 +08:00
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const TargetRegisterInfo *TRI = STI.getRegisterInfo();
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2016-07-29 02:40:00 +08:00
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return MFI.hasVarSizedObjects() && TRI->needsStackRealignment(MF);
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2010-11-19 05:19:35 +08:00
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}
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2012-11-03 05:10:22 +08:00
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2017-11-02 20:47:22 +08:00
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// Estimate the size of the stack, including the incoming arguments. We need to
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// account for register spills, local objects, reserved call frame and incoming
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// arguments. This is required to determine the largest possible positive offset
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// from $sp so that it can be determined if an emergency spill slot for stack
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// addresses is required.
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2012-11-03 05:10:22 +08:00
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uint64_t MipsFrameLowering::estimateStackSize(const MachineFunction &MF) const {
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2016-07-29 02:40:00 +08:00
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const MachineFrameInfo &MFI = MF.getFrameInfo();
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2015-01-30 07:27:36 +08:00
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const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
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2012-11-03 05:10:22 +08:00
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2017-11-02 20:47:22 +08:00
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int64_t Size = 0;
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2012-11-03 05:10:22 +08:00
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2017-11-02 20:47:22 +08:00
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// Iterate over fixed sized objects which are incoming arguments.
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2016-07-29 02:40:00 +08:00
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for (int I = MFI.getObjectIndexBegin(); I != 0; ++I)
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2017-11-02 20:47:22 +08:00
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if (MFI.getObjectOffset(I) > 0)
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Size += MFI.getObjectSize(I);
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2012-11-03 05:10:22 +08:00
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// Conservatively assume all callee-saved registers will be saved.
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2014-04-04 13:16:06 +08:00
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for (const MCPhysReg *R = TRI.getCalleeSavedRegs(&MF); *R; ++R) {
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2017-11-02 20:47:22 +08:00
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unsigned RegSize = TRI.getSpillSize(*TRI.getMinimalPhysRegClass(*R));
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Size = alignTo(Size + RegSize, RegSize);
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2012-11-03 05:10:22 +08:00
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}
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2017-11-02 20:47:22 +08:00
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// Get the size of the rest of the frame objects and any possible reserved
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// call frame, accounting for alignment.
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return Size + MFI.estimateStackSize(MF);
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2012-11-03 05:10:22 +08:00
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}
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2015-04-02 19:09:40 +08:00
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// Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions
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2016-04-01 02:33:38 +08:00
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MachineBasicBlock::iterator MipsFrameLowering::
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2015-04-02 19:09:40 +08:00
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eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator I) const {
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unsigned SP = STI.getABI().IsN64() ? Mips::SP_64 : Mips::SP;
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if (!hasReservedCallFrame(MF)) {
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int64_t Amount = I->getOperand(0).getImm();
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if (I->getOpcode() == Mips::ADJCALLSTACKDOWN)
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Amount = -Amount;
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STI.getInstrInfo()->adjustStackPtr(SP, Amount, MBB, I);
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}
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2016-04-01 02:33:38 +08:00
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return MBB.erase(I);
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2015-04-02 19:09:40 +08:00
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}
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