VEFrameLowering.cpp | Explore in Territory

//===-- VEFrameLowering.cpp - VE Frame Information ------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the VE implementation of TargetFrameLowering class.
//
// On VE, stack frames are structured as follows:
//
// The stack grows downward.
//
// All of the individual frame areas on the frame below are optional, i.e. it's
// possible to create a function so that the particular area isn't present
// in the frame.
//
// At function entry, the "frame" looks as follows:
//
// |                                              | Higher address
// |----------------------------------------------|
// | Parameter area for this function             |
// |----------------------------------------------|
// | Register save area (RSA) for this function   |
// |----------------------------------------------|
// | Return address for this function             |
// |----------------------------------------------|
// | Frame pointer for this function              |
// |----------------------------------------------| <- sp
// |                                              | Lower address
//
// VE doesn't use on demand stack allocation, so user code generated by LLVM
// needs to call VEOS to allocate stack frame.  VE's ABI want to reduce the
// number of VEOS calls, so ABI requires to allocate not only RSA (in general
// CSR, callee saved register) area but also call frame at the prologue of
// caller function.
//
// After the prologue has run, the frame has the following general structure.
// Note that technically the last frame area (VLAs) doesn't get created until
// in the main function body, after the prologue is run. However, it's depicted
// here for completeness.
//
// |                                              | Higher address
// |----------------------------------------------|
// | Parameter area for this function             |
// |----------------------------------------------|
// | Register save area (RSA) for this function   |
// |----------------------------------------------|
// | Return address for this function             |
// |----------------------------------------------|
// | Frame pointer for this function              |
// |----------------------------------------------| <- fp(=old sp)
// |.empty.space.to.make.part.below.aligned.in....|
// |.case.it.needs.more.than.the.standard.16-byte.| (size of this area is
// |.alignment....................................|  unknown at compile time)
// |----------------------------------------------|
// | Local variables of fixed size including spill|
// | slots                                        |
// |----------------------------------------------| <- bp(not defined by ABI,
// |.variable-sized.local.variables.(VLAs)........|       LLVM chooses SX17)
// |..............................................| (size of this area is
// |..............................................|  unknown at compile time)
// |----------------------------------------------| <- stack top (returned by
// | Parameter area for callee                    |               alloca)
// |----------------------------------------------|
// | Register save area (RSA) for callee          |
// |----------------------------------------------|
// | Return address for callee                    |
// |----------------------------------------------|
// | Frame pointer for callee                     |
// |----------------------------------------------| <- sp
// |                                              | Lower address
//
// To access the data in a frame, at-compile time, a constant offset must be
// computable from one of the pointers (fp, bp, sp) to access it. The size
// of the areas with a dotted background cannot be computed at compile-time
// if they are present, making it required to have all three of fp, bp and
// sp to be set up to be able to access all contents in the frame areas,
// assuming all of the frame areas are non-empty.
//
// For most functions, some of the frame areas are empty. For those functions,
// it may not be necessary to set up fp or bp:
// * A base pointer is definitely needed when there are both VLAs and local
//   variables with more-than-default alignment requirements.
// * A frame pointer is definitely needed when there are local variables with
//   more-than-default alignment requirements.
//
// In addition, VE ABI defines RSA frame, return address, and frame pointer
// as follows:
//
// |----------------------------------------------| <- sp+176
// | %s18...%s33                                  |
// |----------------------------------------------| <- sp+48
// | Linkage area register (%s17)                 |
// |----------------------------------------------| <- sp+40
// | Procedure linkage table register (%plt=%s16) |
// |----------------------------------------------| <- sp+32
// | Global offset table register (%got=%s15)     |
// |----------------------------------------------| <- sp+24
// | Thread pointer register (%tp=%s14)           |
// |----------------------------------------------| <- sp+16
// | Return address                               |
// |----------------------------------------------| <- sp+8
// | Frame pointer                                |
// |----------------------------------------------| <- sp+0
//
// NOTE: This description is based on VE ABI and description in
//       AArch64FrameLowering.cpp.  Thanks a lot.
//===----------------------------------------------------------------------===//

#include "VEFrameLowering.h"
#include "VEInstrInfo.h"
#include "VEMachineFunctionInfo.h"
#include "VESubtarget.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/CodeGen/RegisterScavenging.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/MathExtras.h"

usingnamespacellvm;

VEFrameLowering::VEFrameLowering(const VESubtarget &ST)
    : … { … }

void VEFrameLowering::emitPrologueInsns(MachineFunction &MF,
                                        MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
                                        uint64_t NumBytes,
                                        bool RequireFPUpdate) const { … }

void VEFrameLowering::emitEpilogueInsns(MachineFunction &MF,
                                        MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
                                        uint64_t NumBytes,
                                        bool RequireFPUpdate) const { … }

void VEFrameLowering::emitSPAdjustment(MachineFunction &MF,
                                       MachineBasicBlock &MBB,
                                       MachineBasicBlock::iterator MBBI,
                                       int64_t NumBytes,
                                       MaybeAlign MaybeAlign) const { … }

void VEFrameLowering::emitSPExtend(MachineFunction &MF, MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator MBBI) const { … }

void VEFrameLowering::emitPrologue(MachineFunction &MF,
                                   MachineBasicBlock &MBB) const { … }

MachineBasicBlock::iterator VEFrameLowering::eliminateCallFramePseudoInstr(
    MachineFunction &MF, MachineBasicBlock &MBB,
    MachineBasicBlock::iterator I) const { … }

void VEFrameLowering::emitEpilogue(MachineFunction &MF,
                                   MachineBasicBlock &MBB) const { … }

// 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 VEFrameLowering::hasFP(const MachineFunction &MF) const { … }

bool VEFrameLowering::hasBP(const MachineFunction &MF) const { … }

bool VEFrameLowering::hasGOT(const MachineFunction &MF) const { … }

StackOffset VEFrameLowering::getFrameIndexReference(const MachineFunction &MF,
                                                    int FI,
                                                    Register &FrameReg) const { … }

bool VEFrameLowering::isLeafProc(MachineFunction &MF) const { … }

void VEFrameLowering::determineCalleeSaves(MachineFunction &MF,
                                           BitVector &SavedRegs,
                                           RegScavenger *RS) const { … }
llvm/llvm/lib/Target/VE/VEFrameLowering.cpp
