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llvm-6502/lib/CodeGen/PrologEpilogInserter.cpp

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//===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass is responsible for finalizing the functions frame layout, saving
// callee saved registers, and for emitting prolog & epilog code for the
// function.
//
// This pass must be run after register allocation. After this pass is
// executed, it is illegal to construct MO_FrameIndex operands.
//
// This pass implements a shrink wrapping variant of prolog/epilog insertion:
// - Places callee saved register (CSR) spills and restores in the CFG to
// tightly surround uses so that execution paths that do not use CSRs do not
// pay the spill/restore penalty.
//
// - Avoiding placment of spills/restores in loops: if a CSR is used inside a
// loop(nest), the spills are placed in the loop preheader, and restores are
// placed in the loop exit nodes (the successors of the loop _exiting_ nodes).
//
// - Covering paths without CSR uses: e.g. if a restore is placed in a join
// block, a matching spill is added to the end of all immediate predecessor
// blocks that are not reached by a spill. Similarly for saves placed in
// branch blocks.
//
// Shrink wrapping uses an analysis similar to the one in GVNPRE to determine
// which basic blocks require callee-saved register save/restore code.
//
// This pass uses MachineDominators and MachineLoopInfo. Loop information
// is used to prevent shrink wrapping of callee-saved register save/restore
// code into loops.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "shrink-wrap"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/STLExtras.h"
#include <climits>
#include <sstream>
using namespace llvm;
// Shrink Wrapping:
static cl::opt<bool>
ShrinkWrapping("shrink-wrap",
cl::desc("Apply shrink wrapping to callee-saved register spills/restores"));
namespace {
struct VISIBILITY_HIDDEN PEI : public MachineFunctionPass {
static char ID;
PEI() : MachineFunctionPass(&ID) {}
const char *getPassName() const {
return "Prolog/Epilog Insertion & Frame Finalization";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
if (ShrinkWrapping) {
AU.addRequired<MachineLoopInfo>();
AU.addRequired<MachineDominatorTree>();
}
AU.addPreserved<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
MachineFunctionPass::getAnalysisUsage(AU);
}
/// runOnMachineFunction - Insert prolog/epilog code and replace abstract
/// frame indexes with appropriate references.
///
bool runOnMachineFunction(MachineFunction &Fn) {
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
// Get MachineModuleInfo so that we can track the construction of the
// frame.
if (MachineModuleInfo *MMI = getAnalysisIfAvailable<MachineModuleInfo>())
Fn.getFrameInfo()->setMachineModuleInfo(MMI);
// Allow the target machine to make some adjustments to the function
// e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
TRI->processFunctionBeforeCalleeSavedScan(Fn, RS);
// Scan the function for modified callee saved registers and insert spill
// code for any callee saved registers that are modified. Also calculate
// the MaxCallFrameSize and HasCalls variables for the function's frame
// information and eliminates call frame pseudo instructions.
calculateCalleeSavedRegisters(Fn);
// Determine placement of CSR spill/restore code:
// - with shrink wrapping, place spills and restores to tightly
// enclose regions in the Machine CFG of the function where
// they are used. Without shrink wrapping
// - default (no shrink wrapping), place all spills in the
// entry block, all restores in return blocks.
placeCSRSpillsAndRestores(Fn);
// Add the code to save and restore the callee saved registers
insertCSRSpillsAndRestores(Fn);
// Allow the target machine to make final modifications to the function
// before the frame layout is finalized.
TRI->processFunctionBeforeFrameFinalized(Fn);
// Calculate actual frame offsets for all of the abstract stack objects...
calculateFrameObjectOffsets(Fn);
// Add prolog and epilog code to the function. This function is required
// to align the stack frame as necessary for any stack variables or
// called functions. Because of this, calculateCalleeSavedRegisters
// must be called before this function in order to set the HasCalls
// and MaxCallFrameSize variables.
insertPrologEpilogCode(Fn);
// Replace all MO_FrameIndex operands with physical register references
// and actual offsets.
//
replaceFrameIndices(Fn);
delete RS;
return true;
}
private:
RegScavenger *RS;
// MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved
// stack frame indexes.
unsigned MinCSFrameIndex, MaxCSFrameIndex;
// Analysis info for spill/restore placement.
// "CSR": "callee saved register".
// CSRegSet contains indices into the Callee Saved Register Info
// vector built by calculateCalleeSavedRegisters() and accessed
// via MF.getFrameInfo()->getCalleeSavedInfo().
typedef SparseBitVector<> CSRegSet;
// CSRegBlockMap maps MachineBasicBlocks to sets of callee
// saved register indices.
typedef DenseMap<MachineBasicBlock*, CSRegSet> CSRegBlockMap;
// Set and maps for computing CSR spill/restore placement:
// used in function (UsedCSRegs)
// used in a basic block (CSRUsed)
// anticipatable in a basic block (Antic{In,Out})
// available in a basic block (Avail{In,Out})
// to be spilled at the entry to a basic block (CSRSave)
// to be restored at the end of a basic block (CSRRestore)
CSRegSet UsedCSRegs;
CSRegBlockMap CSRUsed;
CSRegBlockMap AnticIn, AnticOut;
CSRegBlockMap AvailIn, AvailOut;
CSRegBlockMap CSRSave;
CSRegBlockMap CSRRestore;
// Entry and return blocks of the current function.
MachineBasicBlock* EntryBlock;
SmallVector<MachineBasicBlock*, 4> ReturnBlocks;
// Flag to control shrink wrapping per-function:
// may choose to skip shrink wrapping for certain
// functions.
bool ShrinkWrapThisFunction;
bool calculateSets(MachineFunction &Fn);
void calculateAnticAvail(MachineFunction &Fn);
MachineBasicBlock* moveSpillsOutOfLoops(MachineFunction &Fn,
MachineBasicBlock* MBB);
void addRestoresForSBranchBlock(MachineFunction &Fn,
MachineBasicBlock* MBB);
void moveRestoresOutOfLoops(MachineFunction& Fn,
MachineBasicBlock* MBB,
std::vector<MachineBasicBlock*>& SBLKS);
void addSavesForRJoinBlocks(MachineFunction& Fn,
std::vector<MachineBasicBlock*>& SBLKS);
void placeSpillsAndRestores(MachineFunction &Fn);
void placeCSRSpillsAndRestores(MachineFunction &Fn);
void calculateCalleeSavedRegisters(MachineFunction &Fn);
void insertCSRSpillsAndRestores(MachineFunction &Fn);
void calculateFrameObjectOffsets(MachineFunction &Fn);
void replaceFrameIndices(MachineFunction &Fn);
void insertPrologEpilogCode(MachineFunction &Fn);
// Initialize all shrink wrapping data.
void initShrinkWrappingInfo() {
UsedCSRegs.clear();
CSRUsed.clear();
AnticIn.clear();
AnticOut.clear();
AvailIn.clear();
AvailOut.clear();
CSRSave.clear();
CSRRestore.clear();
EntryBlock = 0;
if (! ReturnBlocks.empty())
ReturnBlocks.clear();
ShrinkWrapThisFunction = ShrinkWrapping;
}
// Convienences for dealing with machine loops.
MachineBasicBlock* getTopLevelLoopPreheader(MachineLoop* LP) {
assert(LP && "Machine loop is NULL.");
MachineBasicBlock* PHDR = LP->getLoopPreheader();
MachineLoop* PLP = LP->getParentLoop();
while (PLP) {
PHDR = PLP->getLoopPreheader();
PLP = PLP->getParentLoop();
}
return PHDR;
}
MachineLoop* getTopLevelLoopParent(MachineLoop *LP) {
if (LP == 0)
return 0;
MachineLoop* PLP = LP->getParentLoop();
while (PLP) {
LP = PLP;
PLP = PLP->getParentLoop();
}
return LP;
}
#ifndef NDEBUG
// Debugging methods.
static std::string getBasicBlockName(const MachineBasicBlock* MBB) {
std::ostringstream name;
if (MBB) {
if (MBB->getBasicBlock())
name << MBB->getBasicBlock()->getName();
else
name << "_MBB_" << MBB->getNumber();
}
return name.str();
}
static std::string stringifyCSRegSet(const CSRegSet& s,
MachineFunction &Fn) {
const TargetRegisterInfo* TRI = Fn.getTarget().getRegisterInfo();
const std::vector<CalleeSavedInfo> CSI =
Fn.getFrameInfo()->getCalleeSavedInfo();
std::ostringstream srep;
if (CSI.size() == 0) {
srep << "[]";
return srep.str();
}
srep << "[";
CSRegSet::iterator I = s.begin(), E = s.end();
if (I != E) {
unsigned reg = CSI[*I].getReg();
srep << TRI->getName(reg);
for (++I; I != E; ++I) {
reg = CSI[*I].getReg();
srep << ",";
srep << TRI->getName(reg);
}
}
srep << "]";
return srep.str();
}
static void dumpSet(const CSRegSet& s, MachineFunction &Fn) {
DOUT << stringifyCSRegSet(s, Fn) << "\n";
}
#endif
};
char PEI::ID = 0;
}
/// createPrologEpilogCodeInserter - This function returns a pass that inserts
/// prolog and epilog code, and eliminates abstract frame references.
///
FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
/// placeCSRSpillsAndRestores - determine which MBBs of the function
/// need save, restore code for callee-saved registers by doing a DF analysis
/// similar to the one used in code motion (GVNPRE). This produces maps of MBBs
/// to sets of registers (CSRs) for saves and restores. MachineLoopInfo
/// is used to ensure that CSR save/restore code is not placed inside loops.
/// This function computes the maps of MBBs -> CSRs to spill and restore
/// in CSRSave, CSRRestore.
///
/// If shrink wrapping is not being performed, place all spills in
/// the entry block, all restores in return blocks. In this case,
/// CSRSave has a single mapping, CSRRestore has mappings for each
/// return block.
///
void PEI::placeCSRSpillsAndRestores(MachineFunction &Fn) {
#ifndef NDEBUG
DOUT << "Place CSR spills/restores for "
<< Fn.getFunction()->getName() << "\n";
#endif
initShrinkWrappingInfo();
if (calculateSets(Fn))
placeSpillsAndRestores(Fn);
}
/// calculateAnticAvail - helper for computing the data flow
/// sets required for determining spill/restore placements.
///
void PEI::calculateAnticAvail(MachineFunction &Fn) {
// Calulate Antic{In,Out} and Avail{In,Out} iteratively on the MCFG.
bool changed = true;
unsigned iterations = 0;
while (changed) {
changed = false;
for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
MBBI != MBBE; ++MBBI) {
MachineBasicBlock* MBB = MBBI;
// AnticOut[MBB] = INTERSECT(AnticIn[S] for S in SUCC(MBB))
MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end();
if (SI != SE) {
CSRegSet prevAnticOut = AnticOut[MBB];
MachineBasicBlock* SUCC = *SI;
AnticOut[MBB] = AnticIn[SUCC];
for (++SI; SI != SE; ++SI) {
SUCC = *SI;
AnticOut[MBB] &= AnticIn[SUCC];
}
if (prevAnticOut != AnticOut[MBB])
changed = true;
}
// AnticIn[MBB] = CSRUsed[MBB] | AnticOut[MBB];
CSRegSet prevAnticIn = AnticIn[MBB];
AnticIn[MBB] = CSRUsed[MBB] | AnticOut[MBB];
if (prevAnticIn |= AnticIn[MBB])
changed = true;
// AvailIn[MBB] = INTERSECT(AvailOut[S] for S in PRED(MBB))
MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end();
if (PI != PE) {
CSRegSet prevAvailIn = AvailIn[MBB];
MachineBasicBlock* PRED = *PI;
AvailIn[MBB] = AvailOut[PRED];
for (++PI; PI != PE; ++PI) {
PRED = *PI;
AvailIn[MBB] &= AvailOut[PRED];
}
if (prevAvailIn != AvailIn[MBB])
changed = true;
}
// AvailOut[MBB] = CSRUsed[MBB] | AvailIn[MBB];
CSRegSet prevAvailOut = AvailOut[MBB];
AvailOut[MBB] = CSRUsed[MBB] | AvailIn[MBB];
if (prevAvailOut |= AvailOut[MBB])
changed = true;
}
++iterations;
}
// EXP
AnticIn[EntryBlock].clear();
AnticOut[EntryBlock].clear();
#ifndef NDEBUG
DOUT << "-----------------------------------------------------------\n";
DOUT << "iterations = " << iterations << "\n";
DOUT << "-----------------------------------------------------------\n";
DOUT << "MBB | ANTIC_IN | ANTIC_OUT | AVAIL_IN | AVAIL_OUT\n";
DOUT << "-----------------------------------------------------------\n";
for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
MBBI != MBBE; ++MBBI) {
MachineBasicBlock* MBB = MBBI;
DOUT << getBasicBlockName(MBB) << " | "
<< stringifyCSRegSet(AnticIn[MBB], Fn)
<< " | "
<< stringifyCSRegSet(AnticOut[MBB], Fn)
<< " | "
<< stringifyCSRegSet(AvailIn[MBB], Fn)
<< " | "
<< stringifyCSRegSet(AvailOut[MBB], Fn)
<< "\n";
}
#endif
}
/// calculateSets - helper function for placeCSRSpillsAndRestores,
/// collect the CSRs used in this function, develop the DF sets that
/// describe the minimal regions in the Machine CFG around which spills,
/// restores must be placed.
///
/// This function decides if shrink wrapping should actually be done:
/// if all CSR uses are in the entry block, no shrink wrapping is possible,
/// so ShrinkWrapping is turned off (for the current function) and the
/// function returns false.
///
bool PEI::calculateSets(MachineFunction &Fn) {
// Sets used to compute spill, restore placement sets.
const std::vector<CalleeSavedInfo> CSI =
Fn.getFrameInfo()->getCalleeSavedInfo();
// If no CSRs used, we are done.
if (CSI.empty()) {
#ifndef NDEBUG
DOUT << Fn.getFunction()->getName()
<< " uses no callee-saved registers.\n";
#endif
return false;
}
#ifndef NDEBUG
DOUT << "-----------------------------------------------------------\n";
#endif
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
bool allCSRUsesInEntryBlock = true;
// Initialize UsedCSRegs set, CSRUsed map.
// At the same time, put entry block directly into
// CSRSave, CSRRestore sets if any CSRs are used.
//
// Quick exit option (not implemented):
// Given N CSR uses in entry block,
// revert to default behavior, skip the placement
// step and put all saves in entry, restores in
// return blocks.
// Set up entry and return blocks.
EntryBlock = Fn.begin();
for (MachineFunction::iterator MBB = Fn.begin(), E = Fn.end();
MBB != E; ++MBB)
if (!MBB->empty() && MBB->back().getDesc().isReturn())
ReturnBlocks.push_back(MBB);
// TODO -- check for a use of a CSR in each imm. successor of EntryBlock,
// do not shrink wrap this function if this is the case.
// If not shrink wrapping (this function) at this point, set bits in
// CSR{Save,Restore}[] and UsedCSRegs, then return.
if (! ShrinkWrapThisFunction) {
for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) {
UsedCSRegs.set(inx);
CSRSave[EntryBlock].set(inx);
for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
CSRRestore[ReturnBlocks[ri]].set(inx);
}
return false;
}
// Walk instructions in all MBBs, create basic sets, choose
// whether or not to shrink wrap this function.
for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
MBBI != MBBE; ++MBBI) {
MachineBasicBlock* MBB = MBBI;
for (MachineBasicBlock::iterator I = MBB->begin(); I != MBB->end(); ++I) {
for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) {
unsigned Reg = CSI[inx].getReg();
// If instruction I reads or modifies Reg, add it to UsedCSRegs,
// CSRUsed map for the current block.
for (unsigned opInx = 0, opEnd = I->getNumOperands();
opInx != opEnd; ++opInx) {
const MachineOperand &MO = I->getOperand(opInx);
if (! (MO.isReg() && (MO.isUse() || MO.isDef())))
continue;
unsigned MOReg = MO.getReg();
if (!MOReg)
continue;
if (MOReg == Reg ||
(TargetRegisterInfo::isPhysicalRegister(MOReg) &&
TargetRegisterInfo::isPhysicalRegister(Reg) &&
TRI->isSubRegister(MOReg, Reg))) {
// CSR Reg is defined/used in block MBB.
UsedCSRegs.set(inx);
CSRUsed[MBB].set(inx);
// Short-circuit analysis for entry, return blocks:
// if a CSR is used in the entry block, add it directly
// to CSRSave[EntryBlock] and to CSRRestore[R] for R
// in ReturnBlocks. Note CSR uses in non-entry blocks.
if (ShrinkWrapThisFunction) {
if (MBB == EntryBlock) {
CSRSave[MBB].set(inx);
for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
CSRRestore[ReturnBlocks[ri]].set(inx);
} else
allCSRUsesInEntryBlock = false;
} else {
// Not shrink wrapping => ensure saves/restores are correctly
// added for entry, return blocks.
CSRSave[EntryBlock].set(inx);
for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
CSRRestore[ReturnBlocks[ri]].set(inx);
}
}
}
}
}
#ifndef NDEBUG
DOUT << "CSRUsed[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(CSRUsed[MBB], Fn) << "\n";
#endif
}
#ifndef NDEBUG
DOUT << "UsedCSRegs = " << stringifyCSRegSet(UsedCSRegs, Fn) << "\n";
#endif
// Early exit:
// 1. Not asked to do shrink wrapping => just "place" all spills(restores)
// in the entry(return) block(s), already done above.
// 2. All CSR uses in entry block => same as case 1, but say we will
// not shrink wrap the current function.
ShrinkWrapThisFunction = (ShrinkWrapping &&
ShrinkWrapThisFunction &&
! allCSRUsesInEntryBlock);
if (! ShrinkWrapThisFunction) {
return false;
}
calculateAnticAvail(Fn);
return true;
}
/// moveSpillsOutOfLoops - helper for placeSpillsAndRestores() which
/// relocates a spill from a subgraph in a loop to the loop preheader.
/// Returns the MBB to which saves have been moved, or the given MBB
/// if it is a branch point.
///
MachineBasicBlock* PEI::moveSpillsOutOfLoops(MachineFunction &Fn,
MachineBasicBlock* MBB) {
if (MBB == 0 || CSRSave[MBB].empty())
return 0;
// Block to which saves are moved.
MachineBasicBlock* DEST = 0;
MachineLoopInfo &LI = getAnalysis<MachineLoopInfo>();
if (MachineLoop* LP = LI.getLoopFor(MBB)) {
MachineBasicBlock* LPH = getTopLevelLoopPreheader(LP);
assert(LPH && "Loop has no top level preheader?");
#ifndef NDEBUG
DOUT << "Moving saves of "
<< stringifyCSRegSet(CSRSave[MBB], Fn)
<< " from " << getBasicBlockName(MBB)
<< " to " << getBasicBlockName(LPH) << "\n";
#endif
// Add CSRegSet from MBB to LPH, empty out MBB's CSRegSet.
CSRSave[LPH] |= CSRSave[MBB];
// If saves moved to entry block, add restores to returns.
if (LPH == EntryBlock) {
for (unsigned i = 0, e = ReturnBlocks.size(); i != e; ++i)
CSRRestore[ReturnBlocks[i]] |= CSRSave[MBB];
} else {
// Remember where we moved the save so we can add
// restores on successor paths if necessary.
if (LPH->succ_size() > 1)
DEST = LPH;
}
CSRSave[MBB].clear();
} else if (MBB->succ_size() > 1)
DEST = MBB;
return DEST;
}
/// addRestoresForSBranchBlock - helper for placeSpillsAndRestores() which
/// adds restores of CSRs saved in branch point MBBs to the front of any
/// successor blocks connected to regions with no uses of the saved CSRs.
///
void PEI::addRestoresForSBranchBlock(MachineFunction &Fn,
MachineBasicBlock* MBB) {
if (MBB == 0 || CSRSave[MBB].empty() || MBB->succ_size() < 2)
return;
// Add restores of CSRs saved in branch point MBBs to the
// front of any succ blocks flowing into regions that
// have no uses of MBB's CSRs.
bool hasCSRUses = false;
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI) {
MachineBasicBlock* SUCC = *SI;
bool needsRestore = false;
if (CSRUsed[SUCC].intersects(CSRSave[MBB])) {
hasCSRUses = true;
continue;
}
needsRestore = true;
for (df_iterator<MachineBasicBlock*> BI = df_begin(SUCC),
BE = df_end(SUCC); BI != BE; ++BI) {
MachineBasicBlock* SBB = *BI;
if (CSRUsed[SBB].intersects(CSRSave[MBB])) {
hasCSRUses = true;
needsRestore = false;
break;
}
}
// Additional restores are needed for SUCC iff there is at least
// one CSR use reachable from the successors of MBB and there
// are no uses in or below SUCC.
if (needsRestore && hasCSRUses) {
#ifndef NDEBUG
DOUT << "MBB " << getBasicBlockName(MBB)
<< " needs a restore on path to successor "
<< getBasicBlockName(SUCC) << "\n";
#endif
// Add restores to SUCC for all CSRs saved in MBB...
CSRRestore[SUCC] = CSRSave[MBB];
}
}
}
/// moveRestoresOutOfLoops - helper for placeSpillsAndRestores() which
/// relocates restores from a subgraph in a loop to the loop exit blocks.
/// This function records the MBBs to which restores have been moved in
/// SBLKS. If no restores are moved, SBLKS contains the input MBB if it
/// is a join point in the Machine CFG.
///
void PEI::moveRestoresOutOfLoops(MachineFunction& Fn,
MachineBasicBlock* MBB,
std::vector<MachineBasicBlock*>& SBLKS) {
SBLKS.clear();
if (MBB == 0 || CSRRestore[MBB].empty())
return;
MachineLoopInfo &LI = getAnalysis<MachineLoopInfo>();
if (MachineLoop* LP = LI.getLoopFor(MBB)) {
LP = getTopLevelLoopParent(LP);
assert(LP && "Loop with no top level parent?");
SmallVector<MachineBasicBlock*, 4> exitBlocks;
LP->getExitBlocks(exitBlocks);
assert(exitBlocks.size() > 0 &&
"Loop has no top level exit blocks?");
for (unsigned i = 0, e = exitBlocks.size(); i != e; ++i) {
MachineBasicBlock* EXB = exitBlocks[i];
#ifndef NDEBUG
DOUT << "Moving restores of "
<< stringifyCSRegSet(CSRRestore[MBB], Fn)
<< " from " << getBasicBlockName(MBB)
<< " to " << getBasicBlockName(EXB) << "\n";
#endif
// Add CSRegSet from MBB to LPE, empty out MBB's CSRegSet.
CSRRestore[EXB] |= CSRRestore[MBB];
if (EXB->pred_size() > 1)
SBLKS.push_back(EXB);
}
CSRRestore[MBB].clear();
} else if (MBB->pred_size() > 1)
SBLKS.push_back(MBB);
}
/// addSavesForRJoinBlocks - Add saves of CSRs restored in join point MBBs
/// to the ends of any pred blocks that flow into MBB from regions that
/// have no uses of MBB's CSRs.
///
void PEI::addSavesForRJoinBlocks(MachineFunction& Fn,
std::vector<MachineBasicBlock*>& SBLKS) {
if (SBLKS.empty())
return;
for (unsigned i = 0, e = SBLKS.size(); i != e; ++i) {
MachineBasicBlock* MBB = SBLKS[i];
if (MBB->pred_size() > 1) {
bool needsSave = false;
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock* PRED = *PI;
// Walk back up in the CFG from the preds of MBB, look for
// a block that uses any CSR that is restored in MBB.
if (CSRUsed[PRED].intersects(CSRRestore[MBB]))
continue;
needsSave = true;
for (idf_iterator<MachineBasicBlock*> PPI = idf_begin(PRED),
PPE = idf_end(PRED); PPI != PPE; ++PPI) {
MachineBasicBlock* PBB = *PPI;
if (CSRUsed[PBB].intersects(CSRRestore[MBB])) {
needsSave = false;
break;
}
}
if (needsSave) {
// Add saves to PRED for all CSRs restored in MBB...
#ifndef NDEBUG
DOUT << "MBB " << getBasicBlockName(MBB)
<< " needs a save on path from predecessor "
<< getBasicBlockName(PRED) << "\n";
#endif
CSRSave[PRED] = CSRRestore[MBB];
}
}
}
}
}
/// placeSpillsAndRestores - decide which MBBs need spills, restores
/// of CSRs.
///
void PEI::placeSpillsAndRestores(MachineFunction &Fn) {
#ifndef NDEBUG
DOUT << "-----------------------------------------------------------\n";
#endif
// Calculate CSR{Save,Restore} using Antic, Avail on the Machine-CFG.
for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
MBBI != MBBE; ++MBBI) {
MachineBasicBlock* MBB = MBBI;
// Entry block saves are recorded in UsedCSRegs pass above.
if (MBB != EntryBlock) {
// Intersect (CSRegs - AnticIn[P]) for all predecessors P of MBB
CSRegSet anticInPreds;
MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end();
if (PI != PE) {
MachineBasicBlock* PRED = *PI;
anticInPreds = UsedCSRegs - AnticIn[PRED];
for (++PI; PI != PE; ++PI) {
PRED = *PI;
// Handle self loop.
if (PRED != MBB)
anticInPreds &= (UsedCSRegs - AnticIn[PRED]);
}
}
// CSRSave[MBB] = (AnticIn[MBB] - AvailIn[MBB]) & anticInPreds
CSRSave[MBB] = (AnticIn[MBB] - AvailIn[MBB]) & anticInPreds;
// Remove the CSRs that are saved in the entry block
if (! CSRSave[MBB].empty() && ! CSRSave[EntryBlock].empty())
CSRSave[MBB] = CSRSave[MBB] - CSRSave[EntryBlock];
// Move saves inside loops to the preheaders of the outermost
// containing loops, add restores to blocks reached by saves
// placed at branch points where necessary.
if (MachineBasicBlock* DESTBB = moveSpillsOutOfLoops(Fn, MBB)) {
// Add restores to blocks reached by saves placed at branch
// points where necessary.
addRestoresForSBranchBlock(Fn, DESTBB);
}
}
#ifndef NDEBUG
if (! CSRSave[MBB].empty())
DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(CSRSave[MBB], Fn) << "\n";
#endif
// Compute CSRRestore, which may already be set for return blocks.
if (! CSRRestore[MBB].empty() || MBB->pred_size() == 0)
continue;
// Intersect (CSRegs - AvailOut[S]) for all successors S of MBB
CSRegSet availOutSucc;
MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end();
if (SI != SE) {
MachineBasicBlock* SUCC = *SI;
availOutSucc = UsedCSRegs - AvailOut[SUCC];
for (++SI; SI != SE; ++SI) {
SUCC = *SI;
// Handle self loop.
if (SUCC != MBB)
availOutSucc &= (UsedCSRegs - AvailOut[SUCC]);
}
} else if (! CSRUsed[MBB].empty()) {
// Take care of uses in return blocks (which have no successors).
availOutSucc = UsedCSRegs;
}
// CSRRestore[MBB] = (AvailOut[MBB] - AnticOut[MBB]) & availOutSucc
CSRRestore[MBB] = (AvailOut[MBB] - AnticOut[MBB]) & availOutSucc;
// Remove the CSRs that are restored in the return blocks.
// Lest this be confusing, note that:
// CSRSave[EntryBlock] == CSRRestore[B] for all B in ReturnBlocks.
if (! CSRRestore[MBB].empty() && ! CSRSave[EntryBlock].empty())
CSRRestore[MBB] = CSRRestore[MBB] - CSRSave[EntryBlock];
// Move restores inside loops to the exits of the outermost (top level)
// containing loops.
std::vector<MachineBasicBlock*> saveBlocks;
moveRestoresOutOfLoops(Fn, MBB, saveBlocks);
// Add saves of CSRs restored in join point MBBs to the ends
// of any pred blocks that flow into MBB from regions that
// have no uses of MBB's CSRs.
addSavesForRJoinBlocks(Fn, saveBlocks);
#ifndef NDEBUG
if (! CSRRestore[MBB].empty())
DOUT << "RESTORE[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(CSRRestore[MBB], Fn) << "\n";
#endif
}
#ifndef NDEBUG
DOUT << "-----------------------------------------------------------\n";
DOUT << "Final SAVE, RESTORE:\n";
DOUT << "-----------------------------------------------------------\n";
for (MachineFunction::iterator MBB = Fn.begin(), E = Fn.end();
MBB != E; ++MBB) {
if (! CSRSave[MBB].empty()) {
DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(CSRSave[MBB], Fn);
if (CSRRestore[MBB].empty())
DOUT << "\n";
}
if (! CSRRestore[MBB].empty()) {
if (! CSRSave[MBB].empty())
DOUT << " ";
DOUT << "RESTORE[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(CSRRestore[MBB], Fn) << "\n";
}
}
#endif
}
/// calculateCalleeSavedRegisters - Scan the function for modified callee saved
/// registers. Also calculate the MaxCallFrameSize and HasCalls variables for
/// the function's frame information and eliminates call frame pseudo
/// instructions.
///
void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) {
const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo();
// Get the callee saved register list...
const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn);
// Get the function call frame set-up and tear-down instruction opcode
int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode();
int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode();
// These are used to keep track the callee-save area. Initialize them.
MinCSFrameIndex = INT_MAX;
MaxCSFrameIndex = 0;
// Early exit for targets which have no callee saved registers and no call
// frame setup/destroy pseudo instructions.
if ((CSRegs == 0 || CSRegs[0] == 0) &&
FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
return;
unsigned MaxCallFrameSize = 0;
bool HasCalls = false;
std::vector<MachineBasicBlock::iterator> FrameSDOps;
for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
if (I->getOpcode() == FrameSetupOpcode ||
I->getOpcode() == FrameDestroyOpcode) {
assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
" instructions should have a single immediate argument!");
unsigned Size = I->getOperand(0).getImm();
if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
HasCalls = true;
FrameSDOps.push_back(I);
}
MachineFrameInfo *FFI = Fn.getFrameInfo();
FFI->setHasCalls(HasCalls);
FFI->setMaxCallFrameSize(MaxCallFrameSize);
for (unsigned i = 0, e = FrameSDOps.size(); i != e; ++i) {
MachineBasicBlock::iterator I = FrameSDOps[i];
// If call frames are not being included as part of the stack frame,
// and there is no dynamic allocation (therefore referencing frame slots
// off sp), leave the pseudo ops alone. We'll eliminate them later.
if (RegInfo->hasReservedCallFrame(Fn) || RegInfo->hasFP(Fn))
RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
}
// Now figure out which *callee saved* registers are modified by the current
// function, thus needing to be saved and restored in the prolog/epilog.
//
const TargetRegisterClass* const *CSRegClasses =
RegInfo->getCalleeSavedRegClasses(&Fn);
std::vector<CalleeSavedInfo> CSI;
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
if (Fn.getRegInfo().isPhysRegUsed(Reg)) {
// If the reg is modified, save it!
CSI.push_back(CalleeSavedInfo(Reg, CSRegClasses[i]));
} else {
for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
*AliasSet; ++AliasSet) { // Check alias registers too.
if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) {
CSI.push_back(CalleeSavedInfo(Reg, CSRegClasses[i]));
break;
}
}
}
}
if (CSI.empty())
return; // Early exit if no callee saved registers are modified!
unsigned NumFixedSpillSlots;
const std::pair<unsigned,int> *FixedSpillSlots =
TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
// Now that we know which registers need to be saved and restored, allocate
// stack slots for them.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
const TargetRegisterClass *RC = CSI[i].getRegClass();
// Check to see if this physreg must be spilled to a particular stack slot
// on this target.
const std::pair<unsigned,int> *FixedSlot = FixedSpillSlots;
while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
FixedSlot->first != Reg)
++FixedSlot;
int FrameIdx;
if (FixedSlot == FixedSpillSlots+NumFixedSpillSlots) {
// Nope, just spill it anywhere convenient.
unsigned Align = RC->getAlignment();
unsigned StackAlign = TFI->getStackAlignment();
// We may not be able to sastify the desired alignment specification of
// the TargetRegisterClass if the stack alignment is smaller.
// Use the min.
Align = std::min(Align, StackAlign);
FrameIdx = FFI->CreateStackObject(RC->getSize(), Align);
if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
} else {
// Spill it to the stack where we must.
FrameIdx = FFI->CreateFixedObject(RC->getSize(), FixedSlot->second);
}
CSI[i].setFrameIdx(FrameIdx);
}
FFI->setCalleeSavedInfo(CSI);
}
/// insertCSRSpillsAndRestores - Insert spill and restore code for
/// callee saved registers used in the function, handling shrink wrapping.
///
void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
// Get callee saved register information.
MachineFrameInfo *FFI = Fn.getFrameInfo();
const std::vector<CalleeSavedInfo> &CSI = FFI->getCalleeSavedInfo();
// Early exit if no callee saved registers are modified!
if (CSI.empty())
return;
const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
MachineBasicBlock::iterator I;
std::vector<CalleeSavedInfo> blockCSI;
#ifndef NDEBUG
DOUT << "Inserting spill/restore code for CSRs in function "
<< Fn.getFunction()->getName() << "\n";
#endif
// Insert spills.
for (CSRegBlockMap::iterator
BI = CSRSave.begin(), BE = CSRSave.end(); BI != BE; ++BI) {
MachineBasicBlock* MBB = BI->first;
CSRegSet save = BI->second;
if (save.empty())
continue;
if (! ShrinkWrapThisFunction) {
// Spill using target interface.
I = MBB->begin();
if (!TII.spillCalleeSavedRegisters(*MBB, I, CSI)) {
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
// Add the callee-saved register as live-in. It's killed at the spill.
MBB->addLiveIn(CSI[i].getReg());
// Insert the spill to the stack frame.
TII.storeRegToStackSlot(*MBB, I, CSI[i].getReg(), true,
CSI[i].getFrameIdx(), CSI[i].getRegClass());
}
}
} else {
#ifndef NDEBUG
DOUT << "CSRSave[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(save, Fn) << "\n";
#endif
blockCSI.clear();
for (CSRegSet::iterator RI = save.begin(),
RE = save.end(); RI != RE; ++RI) {
blockCSI.push_back(CSI[*RI]);
}
assert(blockCSI.size() > 0 &&
"Could not collect callee saved register info");
// If MBB has no uses of CSRs being saved, this means saves
// must be inserted at the _end_.
if (! MBB->empty() && ! CSRUsed[MBB].intersects(save)) {
I = MBB->end();
--I;
if (I->getDesc().isCall()) {
++I;
} else {
MachineBasicBlock::iterator I2 = I;
while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
I = I2;
}
} else {
I = MBB->begin();
}
// When shrink wrapping, use stack slot stores/loads.
for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
// Add the callee-saved register as live-in.
// It's killed at the spill.
MBB->addLiveIn(blockCSI[i].getReg());
// Insert the spill to the stack frame.
TII.storeRegToStackSlot(*MBB, I, blockCSI[i].getReg(),
true,
blockCSI[i].getFrameIdx(),
blockCSI[i].getRegClass());
}
}
}
// Use CSRRestore to add code to restore the callee-saved registers in
// each block.
for (CSRegBlockMap::iterator
BI = CSRRestore.begin(), BE = CSRRestore.end(); BI != BE; ++BI) {
MachineBasicBlock* MBB = BI->first;
CSRegSet restore = BI->second;
if (restore.empty())
continue;
if (! ShrinkWrapThisFunction) {
// Restore using target interface.
I = MBB->end(); --I;
// Skip over all terminator instructions, which are part of the return
// sequence.
MachineBasicBlock::iterator I2 = I;
while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
I = I2;
bool AtStart = I == MBB->begin();
MachineBasicBlock::iterator BeforeI = I;
if (!AtStart)
--BeforeI;
// Restore all registers immediately before the return and any
// terminators that preceed it.
if (!TII.restoreCalleeSavedRegisters(*MBB, I, CSI)) {
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
TII.loadRegFromStackSlot(*MBB, I, CSI[i].getReg(),
CSI[i].getFrameIdx(),
CSI[i].getRegClass());
assert(I != MBB->begin() &&
"loadRegFromStackSlot didn't insert any code!");
// Insert in reverse order. loadRegFromStackSlot can insert
// multiple instructions.
if (AtStart)
I = MBB->begin();
else {
I = BeforeI;
++I;
}
}
}
} else {
#ifndef NDEBUG
DOUT << "CSRRestore[" << getBasicBlockName(MBB) << "] = "
<< stringifyCSRegSet(restore, Fn) << "\n";
#endif
blockCSI.clear();
for (CSRegSet::iterator RI = restore.begin(),
RE = restore.end(); RI != RE; ++RI) {
blockCSI.push_back(CSI[*RI]);
}
assert(blockCSI.size() > 0 &&
"Could not find callee saved register info");
// If MBB uses no CSRs but has restores, this means
// it must have restores inserted at the _beginning_.
// N.B. -- not necessary if edge splitting done.
if (MBB->empty() || ! CSRUsed[MBB].intersects(restore)) {
I = MBB->begin();
} else {
I = MBB->end();
--I;
// EXP iff spill/restore implemented with push/pop:
// append restore to block unless it ends in a
// barrier terminator instruction.
// Skip over all terminator instructions, which are part of the
// return sequence.
if (I->getDesc().isCall()) {
++I;
} else {
MachineBasicBlock::iterator I2 = I;
while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
I = I2;
}
}
bool AtStart = I == MBB->begin();
MachineBasicBlock::iterator BeforeI = I;
if (!AtStart)
--BeforeI;
#ifndef NDEBUG
if (! MBB->empty() && ! CSRUsed[MBB].intersects(restore)) {
MachineInstr* MI = BeforeI;
DOUT << "adding restore after ";
DEBUG(MI->dump());
} else {
DOUT << "adding restore to beginning of "
<< getBasicBlockName(MBB) << "\n";
}
#endif
// Restore all registers immediately before the return and any
// terminators that preceed it.
for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
TII.loadRegFromStackSlot(*MBB, I, blockCSI[i].getReg(),
blockCSI[i].getFrameIdx(),
blockCSI[i].getRegClass());
assert(I != MBB->begin() &&
"loadRegFromStackSlot didn't insert any code!");
// Insert in reverse order. loadRegFromStackSlot can insert
// multiple instructions.
if (AtStart)
I = MBB->begin();
else {
I = BeforeI;
++I;
}
}
}
}
}
/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
static inline void
AdjustStackOffset(MachineFrameInfo *FFI, int FrameIdx,
bool StackGrowsDown, int64_t &Offset,
unsigned &MaxAlign) {
// If stack grows down, we need to add size of find the lowest address of the
// object.
if (StackGrowsDown)
Offset += FFI->getObjectSize(FrameIdx);
unsigned Align = FFI->getObjectAlignment(FrameIdx);
// If the alignment of this object is greater than that of the stack, then
// increase the stack alignment to match.
MaxAlign = std::max(MaxAlign, Align);
// Adjust to alignment boundary.
Offset = (Offset + Align - 1) / Align * Align;
if (StackGrowsDown) {
FFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
} else {
FFI->setObjectOffset(FrameIdx, Offset);
Offset += FFI->getObjectSize(FrameIdx);
}
}
/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
bool StackGrowsDown =
TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
// Loop over all of the stack objects, assigning sequential addresses...
MachineFrameInfo *FFI = Fn.getFrameInfo();
unsigned MaxAlign = FFI->getMaxAlignment();
// Start at the beginning of the local area.
// The Offset is the distance from the stack top in the direction
// of stack growth -- so it's always nonnegative.
int64_t Offset = TFI.getOffsetOfLocalArea();
if (StackGrowsDown)
Offset = -Offset;
assert(Offset >= 0
&& "Local area offset should be in direction of stack growth");
// If there are fixed sized objects that are preallocated in the local area,
// non-fixed objects can't be allocated right at the start of local area.
// We currently don't support filling in holes in between fixed sized
// objects, so we adjust 'Offset' to point to the end of last fixed sized
// preallocated object.
for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) {
int64_t FixedOff;
if (StackGrowsDown) {
// The maximum distance from the stack pointer is at lower address of
// the object -- which is given by offset. For down growing stack
// the offset is negative, so we negate the offset to get the distance.
FixedOff = -FFI->getObjectOffset(i);
} else {
// The maximum distance from the start pointer is at the upper
// address of the object.
FixedOff = FFI->getObjectOffset(i) + FFI->getObjectSize(i);
}
if (FixedOff > Offset) Offset = FixedOff;
}
// First assign frame offsets to stack objects that are used to spill
// callee saved registers.
if (StackGrowsDown) {
for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
// If stack grows down, we need to add size of find the lowest
// address of the object.
Offset += FFI->getObjectSize(i);
unsigned Align = FFI->getObjectAlignment(i);
// If the alignment of this object is greater than that of the stack,
// then increase the stack alignment to match.
MaxAlign = std::max(MaxAlign, Align);
// Adjust to alignment boundary
Offset = (Offset+Align-1)/Align*Align;
FFI->setObjectOffset(i, -Offset); // Set the computed offset
}
} else {
int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
for (int i = MaxCSFI; i >= MinCSFI ; --i) {
unsigned Align = FFI->getObjectAlignment(i);
// If the alignment of this object is greater than that of the stack,
// then increase the stack alignment to match.
MaxAlign = std::max(MaxAlign, Align);
// Adjust to alignment boundary
Offset = (Offset+Align-1)/Align*Align;
FFI->setObjectOffset(i, Offset);
Offset += FFI->getObjectSize(i);
}
}
// Make sure the special register scavenging spill slot is closest to the
// frame pointer if a frame pointer is required.
const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
if (RS && RegInfo->hasFP(Fn)) {
int SFI = RS->getScavengingFrameIndex();
if (SFI >= 0)
AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign);
}
// Make sure that the stack protector comes before the local variables on the
// stack.
if (FFI->getStackProtectorIndex() >= 0)
AdjustStackOffset(FFI, FFI->getStackProtectorIndex(), StackGrowsDown,
Offset, MaxAlign);
// Then assign frame offsets to stack objects that are not used to spill
// callee saved registers.
for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) {
if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
continue;
if (RS && (int)i == RS->getScavengingFrameIndex())
continue;
if (FFI->isDeadObjectIndex(i))
continue;
if (FFI->getStackProtectorIndex() == (int)i)
continue;
AdjustStackOffset(FFI, i, StackGrowsDown, Offset, MaxAlign);
}
// Make sure the special register scavenging spill slot is closest to the
// stack pointer.
if (RS && !RegInfo->hasFP(Fn)) {
int SFI = RS->getScavengingFrameIndex();
if (SFI >= 0)
AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign);
}
// Round up the size to a multiple of the alignment, but only if there are
// calls or alloca's in the function. This ensures that any calls to
// subroutines have their stack frames suitable aligned.
// Also do this if we need runtime alignment of the stack. In this case
// offsets will be relative to SP not FP; round up the stack size so this
// works.
if (!RegInfo->targetHandlesStackFrameRounding() &&
(FFI->hasCalls() || FFI->hasVarSizedObjects() ||
(RegInfo->needsStackRealignment(Fn) &&
FFI->getObjectIndexEnd() != 0))) {
// If we have reserved argument space for call sites in the function
// immediately on entry to the current function, count it as part of the
// overall stack size.
if (RegInfo->hasReservedCallFrame(Fn))
Offset += FFI->getMaxCallFrameSize();
unsigned AlignMask = std::max(TFI.getStackAlignment(),MaxAlign) - 1;
Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
}
// Update frame info to pretend that this is part of the stack...
FFI->setStackSize(Offset+TFI.getOffsetOfLocalArea());
// Remember the required stack alignment in case targets need it to perform
// dynamic stack alignment.
FFI->setMaxAlignment(MaxAlign);
}
/// insertPrologEpilogCode - Scan the function for modified callee saved
/// registers, insert spill code for these callee saved registers, then add
/// prolog and epilog code to the function.
///
void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
// Add prologue to the function...
TRI->emitPrologue(Fn);
// Add epilogue to restore the callee-save registers in each exiting block
for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
// If last instruction is a return instruction, add an epilogue
if (!I->empty() && I->back().getDesc().isReturn())
TRI->emitEpilogue(Fn, *I);
}
}
/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
/// register references and actual offsets.
///
void PEI::replaceFrameIndices(MachineFunction &Fn) {
if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
const TargetMachine &TM = Fn.getTarget();
assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
const TargetFrameInfo *TFI = TM.getFrameInfo();
bool StackGrowsDown =
TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
int FrameSetupOpcode = TRI.getCallFrameSetupOpcode();
int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode();
for (MachineFunction::iterator BB = Fn.begin(),
E = Fn.end(); BB != E; ++BB) {
int SPAdj = 0; // SP offset due to call frame setup / destroy.
if (RS) RS->enterBasicBlock(BB);
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
if (I->getOpcode() == TargetInstrInfo::DECLARE) {
// Ignore it.
++I;
continue;
}
if (I->getOpcode() == FrameSetupOpcode ||
I->getOpcode() == FrameDestroyOpcode) {
// Remember how much SP has been adjusted to create the call
// frame.
int Size = I->getOperand(0).getImm();
if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
(StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
Size = -Size;
SPAdj += Size;
MachineBasicBlock::iterator PrevI = BB->end();
if (I != BB->begin()) PrevI = prior(I);
TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
// Visit the instructions created by eliminateCallFramePseudoInstr().
if (PrevI == BB->end())
I = BB->begin(); // The replaced instr was the first in the block.
else
I = next(PrevI);
continue;
}
MachineInstr *MI = I;
bool DoIncr = true;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
if (MI->getOperand(i).isFI()) {
// Some instructions (e.g. inline asm instructions) can have
// multiple frame indices and/or cause eliminateFrameIndex
// to insert more than one instruction. We need the register
// scavenger to go through all of these instructions so that
// it can update its register information. We keep the
// iterator at the point before insertion so that we can
// revisit them in full.
bool AtBeginning = (I == BB->begin());
if (!AtBeginning) --I;
// If this instruction has a FrameIndex operand, we need to
// use that target machine register info object to eliminate
// it.
TRI.eliminateFrameIndex(MI, SPAdj, RS);
// Reset the iterator if we were at the beginning of the BB.
if (AtBeginning) {
I = BB->begin();
DoIncr = false;
}
MI = 0;
break;
}
if (DoIncr && I != BB->end()) ++I;
// Update register states.
if (RS && MI) RS->forward(MI);
}
assert(SPAdj == 0 && "Unbalanced call frame setup / destroy pairs?");
}
}
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