mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-29 13:29:28 +00:00
Summary: No functional change yet, it's just an object replacement for an enum. It will allow us to gather ABI information in a single place so that we can start testing for properties of the ABI's instead of the ABI itself. For example we will eventually be able to use: ABI.MinStackAlignmentInBytes() instead of: (isABI_N32() || isABI_N64()) ? 16 : 8 which is clearer and more maintainable. Reviewers: matheusalmeida Reviewed By: matheusalmeida Differential Revision: http://reviews.llvm.org/D3341 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220568 91177308-0d34-0410-b5e6-96231b3b80d8
1719 lines
62 KiB
C++
1719 lines
62 KiB
C++
//===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
//
|
|
// This pass is used to make Pc relative loads of constants.
|
|
// For now, only Mips16 will use this.
|
|
//
|
|
// Loading constants inline is expensive on Mips16 and it's in general better
|
|
// to place the constant nearby in code space and then it can be loaded with a
|
|
// simple 16 bit load instruction.
|
|
//
|
|
// The constants can be not just numbers but addresses of functions and labels.
|
|
// This can be particularly helpful in static relocation mode for embedded
|
|
// non-linux targets.
|
|
//
|
|
//
|
|
|
|
#include "Mips.h"
|
|
#include "MCTargetDesc/MipsBaseInfo.h"
|
|
#include "Mips16InstrInfo.h"
|
|
#include "MipsMachineFunction.h"
|
|
#include "MipsTargetMachine.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/CodeGen/MachineBasicBlock.h"
|
|
#include "llvm/CodeGen/MachineConstantPool.h"
|
|
#include "llvm/CodeGen/MachineFunctionPass.h"
|
|
#include "llvm/CodeGen/MachineInstrBuilder.h"
|
|
#include "llvm/CodeGen/MachineRegisterInfo.h"
|
|
#include "llvm/IR/Function.h"
|
|
#include "llvm/IR/InstIterator.h"
|
|
#include "llvm/Support/CommandLine.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/Format.h"
|
|
#include "llvm/Support/MathExtras.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
#include "llvm/Target/TargetInstrInfo.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
#include "llvm/Target/TargetRegisterInfo.h"
|
|
#include <algorithm>
|
|
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "mips-constant-islands"
|
|
|
|
STATISTIC(NumCPEs, "Number of constpool entries");
|
|
STATISTIC(NumSplit, "Number of uncond branches inserted");
|
|
STATISTIC(NumCBrFixed, "Number of cond branches fixed");
|
|
STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
|
|
|
|
// FIXME: This option should be removed once it has received sufficient testing.
|
|
static cl::opt<bool>
|
|
AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
|
|
cl::desc("Align constant islands in code"));
|
|
|
|
|
|
// Rather than do make check tests with huge amounts of code, we force
|
|
// the test to use this amount.
|
|
//
|
|
static cl::opt<int> ConstantIslandsSmallOffset(
|
|
"mips-constant-islands-small-offset",
|
|
cl::init(0),
|
|
cl::desc("Make small offsets be this amount for testing purposes"),
|
|
cl::Hidden);
|
|
|
|
//
|
|
// For testing purposes we tell it to not use relaxed load forms so that it
|
|
// will split blocks.
|
|
//
|
|
static cl::opt<bool> NoLoadRelaxation(
|
|
"mips-constant-islands-no-load-relaxation",
|
|
cl::init(false),
|
|
cl::desc("Don't relax loads to long loads - for testing purposes"),
|
|
cl::Hidden);
|
|
|
|
static unsigned int branchTargetOperand(MachineInstr *MI) {
|
|
switch (MI->getOpcode()) {
|
|
case Mips::Bimm16:
|
|
case Mips::BimmX16:
|
|
case Mips::Bteqz16:
|
|
case Mips::BteqzX16:
|
|
case Mips::Btnez16:
|
|
case Mips::BtnezX16:
|
|
case Mips::JalB16:
|
|
return 0;
|
|
case Mips::BeqzRxImm16:
|
|
case Mips::BeqzRxImmX16:
|
|
case Mips::BnezRxImm16:
|
|
case Mips::BnezRxImmX16:
|
|
return 1;
|
|
}
|
|
llvm_unreachable("Unknown branch type");
|
|
}
|
|
|
|
static bool isUnconditionalBranch(unsigned int Opcode) {
|
|
switch (Opcode) {
|
|
default: return false;
|
|
case Mips::Bimm16:
|
|
case Mips::BimmX16:
|
|
case Mips::JalB16:
|
|
return true;
|
|
}
|
|
}
|
|
|
|
static unsigned int longformBranchOpcode(unsigned int Opcode) {
|
|
switch (Opcode) {
|
|
case Mips::Bimm16:
|
|
case Mips::BimmX16:
|
|
return Mips::BimmX16;
|
|
case Mips::Bteqz16:
|
|
case Mips::BteqzX16:
|
|
return Mips::BteqzX16;
|
|
case Mips::Btnez16:
|
|
case Mips::BtnezX16:
|
|
return Mips::BtnezX16;
|
|
case Mips::JalB16:
|
|
return Mips::JalB16;
|
|
case Mips::BeqzRxImm16:
|
|
case Mips::BeqzRxImmX16:
|
|
return Mips::BeqzRxImmX16;
|
|
case Mips::BnezRxImm16:
|
|
case Mips::BnezRxImmX16:
|
|
return Mips::BnezRxImmX16;
|
|
}
|
|
llvm_unreachable("Unknown branch type");
|
|
}
|
|
|
|
//
|
|
// FIXME: need to go through this whole constant islands port and check the math
|
|
// for branch ranges and clean this up and make some functions to calculate things
|
|
// that are done many times identically.
|
|
// Need to refactor some of the code to call this routine.
|
|
//
|
|
static unsigned int branchMaxOffsets(unsigned int Opcode) {
|
|
unsigned Bits, Scale;
|
|
switch (Opcode) {
|
|
case Mips::Bimm16:
|
|
Bits = 11;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BimmX16:
|
|
Bits = 16;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BeqzRxImm16:
|
|
Bits = 8;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BeqzRxImmX16:
|
|
Bits = 16;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BnezRxImm16:
|
|
Bits = 8;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BnezRxImmX16:
|
|
Bits = 16;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::Bteqz16:
|
|
Bits = 8;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BteqzX16:
|
|
Bits = 16;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::Btnez16:
|
|
Bits = 8;
|
|
Scale = 2;
|
|
break;
|
|
case Mips::BtnezX16:
|
|
Bits = 16;
|
|
Scale = 2;
|
|
break;
|
|
default:
|
|
llvm_unreachable("Unknown branch type");
|
|
}
|
|
unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
|
|
return MaxOffs;
|
|
}
|
|
|
|
namespace {
|
|
|
|
|
|
typedef MachineBasicBlock::iterator Iter;
|
|
typedef MachineBasicBlock::reverse_iterator ReverseIter;
|
|
|
|
/// MipsConstantIslands - Due to limited PC-relative displacements, Mips
|
|
/// requires constant pool entries to be scattered among the instructions
|
|
/// inside a function. To do this, it completely ignores the normal LLVM
|
|
/// constant pool; instead, it places constants wherever it feels like with
|
|
/// special instructions.
|
|
///
|
|
/// The terminology used in this pass includes:
|
|
/// Islands - Clumps of constants placed in the function.
|
|
/// Water - Potential places where an island could be formed.
|
|
/// CPE - A constant pool entry that has been placed somewhere, which
|
|
/// tracks a list of users.
|
|
|
|
class MipsConstantIslands : public MachineFunctionPass {
|
|
|
|
/// BasicBlockInfo - Information about the offset and size of a single
|
|
/// basic block.
|
|
struct BasicBlockInfo {
|
|
/// Offset - Distance from the beginning of the function to the beginning
|
|
/// of this basic block.
|
|
///
|
|
/// Offsets are computed assuming worst case padding before an aligned
|
|
/// block. This means that subtracting basic block offsets always gives a
|
|
/// conservative estimate of the real distance which may be smaller.
|
|
///
|
|
/// Because worst case padding is used, the computed offset of an aligned
|
|
/// block may not actually be aligned.
|
|
unsigned Offset;
|
|
|
|
/// Size - Size of the basic block in bytes. If the block contains
|
|
/// inline assembly, this is a worst case estimate.
|
|
///
|
|
/// The size does not include any alignment padding whether from the
|
|
/// beginning of the block, or from an aligned jump table at the end.
|
|
unsigned Size;
|
|
|
|
// FIXME: ignore LogAlign for this patch
|
|
//
|
|
unsigned postOffset(unsigned LogAlign = 0) const {
|
|
unsigned PO = Offset + Size;
|
|
return PO;
|
|
}
|
|
|
|
BasicBlockInfo() : Offset(0), Size(0) {}
|
|
|
|
};
|
|
|
|
std::vector<BasicBlockInfo> BBInfo;
|
|
|
|
/// WaterList - A sorted list of basic blocks where islands could be placed
|
|
/// (i.e. blocks that don't fall through to the following block, due
|
|
/// to a return, unreachable, or unconditional branch).
|
|
std::vector<MachineBasicBlock*> WaterList;
|
|
|
|
/// NewWaterList - The subset of WaterList that was created since the
|
|
/// previous iteration by inserting unconditional branches.
|
|
SmallSet<MachineBasicBlock*, 4> NewWaterList;
|
|
|
|
typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
|
|
|
|
/// CPUser - One user of a constant pool, keeping the machine instruction
|
|
/// pointer, the constant pool being referenced, and the max displacement
|
|
/// allowed from the instruction to the CP. The HighWaterMark records the
|
|
/// highest basic block where a new CPEntry can be placed. To ensure this
|
|
/// pass terminates, the CP entries are initially placed at the end of the
|
|
/// function and then move monotonically to lower addresses. The
|
|
/// exception to this rule is when the current CP entry for a particular
|
|
/// CPUser is out of range, but there is another CP entry for the same
|
|
/// constant value in range. We want to use the existing in-range CP
|
|
/// entry, but if it later moves out of range, the search for new water
|
|
/// should resume where it left off. The HighWaterMark is used to record
|
|
/// that point.
|
|
struct CPUser {
|
|
MachineInstr *MI;
|
|
MachineInstr *CPEMI;
|
|
MachineBasicBlock *HighWaterMark;
|
|
private:
|
|
unsigned MaxDisp;
|
|
unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
|
|
// with different displacements
|
|
unsigned LongFormOpcode;
|
|
public:
|
|
bool NegOk;
|
|
CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
|
|
bool neg,
|
|
unsigned longformmaxdisp, unsigned longformopcode)
|
|
: MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
|
|
LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
|
|
NegOk(neg){
|
|
HighWaterMark = CPEMI->getParent();
|
|
}
|
|
/// getMaxDisp - Returns the maximum displacement supported by MI.
|
|
unsigned getMaxDisp() const {
|
|
unsigned xMaxDisp = ConstantIslandsSmallOffset?
|
|
ConstantIslandsSmallOffset: MaxDisp;
|
|
return xMaxDisp;
|
|
}
|
|
void setMaxDisp(unsigned val) {
|
|
MaxDisp = val;
|
|
}
|
|
unsigned getLongFormMaxDisp() const {
|
|
return LongFormMaxDisp;
|
|
}
|
|
unsigned getLongFormOpcode() const {
|
|
return LongFormOpcode;
|
|
}
|
|
};
|
|
|
|
/// CPUsers - Keep track of all of the machine instructions that use various
|
|
/// constant pools and their max displacement.
|
|
std::vector<CPUser> CPUsers;
|
|
|
|
/// CPEntry - One per constant pool entry, keeping the machine instruction
|
|
/// pointer, the constpool index, and the number of CPUser's which
|
|
/// reference this entry.
|
|
struct CPEntry {
|
|
MachineInstr *CPEMI;
|
|
unsigned CPI;
|
|
unsigned RefCount;
|
|
CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
|
|
: CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
|
|
};
|
|
|
|
/// CPEntries - Keep track of all of the constant pool entry machine
|
|
/// instructions. For each original constpool index (i.e. those that
|
|
/// existed upon entry to this pass), it keeps a vector of entries.
|
|
/// Original elements are cloned as we go along; the clones are
|
|
/// put in the vector of the original element, but have distinct CPIs.
|
|
std::vector<std::vector<CPEntry> > CPEntries;
|
|
|
|
/// ImmBranch - One per immediate branch, keeping the machine instruction
|
|
/// pointer, conditional or unconditional, the max displacement,
|
|
/// and (if isCond is true) the corresponding unconditional branch
|
|
/// opcode.
|
|
struct ImmBranch {
|
|
MachineInstr *MI;
|
|
unsigned MaxDisp : 31;
|
|
bool isCond : 1;
|
|
int UncondBr;
|
|
ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
|
|
: MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
|
|
};
|
|
|
|
/// ImmBranches - Keep track of all the immediate branch instructions.
|
|
///
|
|
std::vector<ImmBranch> ImmBranches;
|
|
|
|
/// HasFarJump - True if any far jump instruction has been emitted during
|
|
/// the branch fix up pass.
|
|
bool HasFarJump;
|
|
|
|
const TargetMachine &TM;
|
|
bool IsPIC;
|
|
const MipsSubtarget *STI;
|
|
const Mips16InstrInfo *TII;
|
|
MipsFunctionInfo *MFI;
|
|
MachineFunction *MF;
|
|
MachineConstantPool *MCP;
|
|
|
|
unsigned PICLabelUId;
|
|
bool PrescannedForConstants;
|
|
|
|
void initPICLabelUId(unsigned UId) {
|
|
PICLabelUId = UId;
|
|
}
|
|
|
|
|
|
unsigned createPICLabelUId() {
|
|
return PICLabelUId++;
|
|
}
|
|
|
|
public:
|
|
static char ID;
|
|
MipsConstantIslands(TargetMachine &tm)
|
|
: MachineFunctionPass(ID), TM(tm),
|
|
IsPIC(TM.getRelocationModel() == Reloc::PIC_), STI(nullptr),
|
|
MF(nullptr), MCP(nullptr), PrescannedForConstants(false) {}
|
|
|
|
const char *getPassName() const override {
|
|
return "Mips Constant Islands";
|
|
}
|
|
|
|
bool runOnMachineFunction(MachineFunction &F) override;
|
|
|
|
void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
|
|
CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
|
|
unsigned getCPELogAlign(const MachineInstr *CPEMI);
|
|
void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
|
|
unsigned getOffsetOf(MachineInstr *MI) const;
|
|
unsigned getUserOffset(CPUser&) const;
|
|
void dumpBBs();
|
|
|
|
bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
|
|
unsigned Disp, bool NegativeOK);
|
|
bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
|
|
const CPUser &U);
|
|
|
|
void computeBlockSize(MachineBasicBlock *MBB);
|
|
MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
|
|
void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
|
|
void adjustBBOffsetsAfter(MachineBasicBlock *BB);
|
|
bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
|
|
int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
|
|
int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
|
|
bool findAvailableWater(CPUser&U, unsigned UserOffset,
|
|
water_iterator &WaterIter);
|
|
void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
|
|
MachineBasicBlock *&NewMBB);
|
|
bool handleConstantPoolUser(unsigned CPUserIndex);
|
|
void removeDeadCPEMI(MachineInstr *CPEMI);
|
|
bool removeUnusedCPEntries();
|
|
bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
|
|
MachineInstr *CPEMI, unsigned Disp, bool NegOk,
|
|
bool DoDump = false);
|
|
bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
|
|
CPUser &U, unsigned &Growth);
|
|
bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
|
|
bool fixupImmediateBr(ImmBranch &Br);
|
|
bool fixupConditionalBr(ImmBranch &Br);
|
|
bool fixupUnconditionalBr(ImmBranch &Br);
|
|
|
|
void prescanForConstants();
|
|
|
|
private:
|
|
|
|
};
|
|
|
|
char MipsConstantIslands::ID = 0;
|
|
} // end of anonymous namespace
|
|
|
|
bool MipsConstantIslands::isOffsetInRange
|
|
(unsigned UserOffset, unsigned TrialOffset,
|
|
const CPUser &U) {
|
|
return isOffsetInRange(UserOffset, TrialOffset,
|
|
U.getMaxDisp(), U.NegOk);
|
|
}
|
|
/// print block size and offset information - debugging
|
|
void MipsConstantIslands::dumpBBs() {
|
|
DEBUG({
|
|
for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
|
|
const BasicBlockInfo &BBI = BBInfo[J];
|
|
dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
|
|
<< format(" size=%#x\n", BBInfo[J].Size);
|
|
}
|
|
});
|
|
}
|
|
/// createMipsLongBranchPass - Returns a pass that converts branches to long
|
|
/// branches.
|
|
FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
|
|
return new MipsConstantIslands(tm);
|
|
}
|
|
|
|
bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
|
|
// The intention is for this to be a mips16 only pass for now
|
|
// FIXME:
|
|
MF = &mf;
|
|
MCP = mf.getConstantPool();
|
|
STI = &mf.getTarget().getSubtarget<MipsSubtarget>();
|
|
DEBUG(dbgs() << "constant island machine function " << "\n");
|
|
if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) {
|
|
return false;
|
|
}
|
|
TII = (const Mips16InstrInfo *)MF->getTarget()
|
|
.getSubtargetImpl()
|
|
->getInstrInfo();
|
|
MFI = MF->getInfo<MipsFunctionInfo>();
|
|
DEBUG(dbgs() << "constant island processing " << "\n");
|
|
//
|
|
// will need to make predermination if there is any constants we need to
|
|
// put in constant islands. TBD.
|
|
//
|
|
if (!PrescannedForConstants) prescanForConstants();
|
|
|
|
HasFarJump = false;
|
|
// This pass invalidates liveness information when it splits basic blocks.
|
|
MF->getRegInfo().invalidateLiveness();
|
|
|
|
// Renumber all of the machine basic blocks in the function, guaranteeing that
|
|
// the numbers agree with the position of the block in the function.
|
|
MF->RenumberBlocks();
|
|
|
|
bool MadeChange = false;
|
|
|
|
// Perform the initial placement of the constant pool entries. To start with,
|
|
// we put them all at the end of the function.
|
|
std::vector<MachineInstr*> CPEMIs;
|
|
if (!MCP->isEmpty())
|
|
doInitialPlacement(CPEMIs);
|
|
|
|
/// The next UID to take is the first unused one.
|
|
initPICLabelUId(CPEMIs.size());
|
|
|
|
// Do the initial scan of the function, building up information about the
|
|
// sizes of each block, the location of all the water, and finding all of the
|
|
// constant pool users.
|
|
initializeFunctionInfo(CPEMIs);
|
|
CPEMIs.clear();
|
|
DEBUG(dumpBBs());
|
|
|
|
/// Remove dead constant pool entries.
|
|
MadeChange |= removeUnusedCPEntries();
|
|
|
|
// Iteratively place constant pool entries and fix up branches until there
|
|
// is no change.
|
|
unsigned NoCPIters = 0, NoBRIters = 0;
|
|
(void)NoBRIters;
|
|
while (true) {
|
|
DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
|
|
bool CPChange = false;
|
|
for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
|
|
CPChange |= handleConstantPoolUser(i);
|
|
if (CPChange && ++NoCPIters > 30)
|
|
report_fatal_error("Constant Island pass failed to converge!");
|
|
DEBUG(dumpBBs());
|
|
|
|
// Clear NewWaterList now. If we split a block for branches, it should
|
|
// appear as "new water" for the next iteration of constant pool placement.
|
|
NewWaterList.clear();
|
|
|
|
DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
|
|
bool BRChange = false;
|
|
for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
|
|
BRChange |= fixupImmediateBr(ImmBranches[i]);
|
|
if (BRChange && ++NoBRIters > 30)
|
|
report_fatal_error("Branch Fix Up pass failed to converge!");
|
|
DEBUG(dumpBBs());
|
|
if (!CPChange && !BRChange)
|
|
break;
|
|
MadeChange = true;
|
|
}
|
|
|
|
DEBUG(dbgs() << '\n'; dumpBBs());
|
|
|
|
BBInfo.clear();
|
|
WaterList.clear();
|
|
CPUsers.clear();
|
|
CPEntries.clear();
|
|
ImmBranches.clear();
|
|
return MadeChange;
|
|
}
|
|
|
|
/// doInitialPlacement - Perform the initial placement of the constant pool
|
|
/// entries. To start with, we put them all at the end of the function.
|
|
void
|
|
MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
|
|
// Create the basic block to hold the CPE's.
|
|
MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
|
|
MF->push_back(BB);
|
|
|
|
|
|
// MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
|
|
unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
|
|
|
|
// Mark the basic block as required by the const-pool.
|
|
// If AlignConstantIslands isn't set, use 4-byte alignment for everything.
|
|
BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
|
|
|
|
// The function needs to be as aligned as the basic blocks. The linker may
|
|
// move functions around based on their alignment.
|
|
MF->ensureAlignment(BB->getAlignment());
|
|
|
|
// Order the entries in BB by descending alignment. That ensures correct
|
|
// alignment of all entries as long as BB is sufficiently aligned. Keep
|
|
// track of the insertion point for each alignment. We are going to bucket
|
|
// sort the entries as they are created.
|
|
SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
|
|
|
|
// Add all of the constants from the constant pool to the end block, use an
|
|
// identity mapping of CPI's to CPE's.
|
|
const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
|
|
|
|
const DataLayout &TD = *MF->getSubtarget().getDataLayout();
|
|
for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
|
|
unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
|
|
assert(Size >= 4 && "Too small constant pool entry");
|
|
unsigned Align = CPs[i].getAlignment();
|
|
assert(isPowerOf2_32(Align) && "Invalid alignment");
|
|
// Verify that all constant pool entries are a multiple of their alignment.
|
|
// If not, we would have to pad them out so that instructions stay aligned.
|
|
assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
|
|
|
|
// Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
|
|
unsigned LogAlign = Log2_32(Align);
|
|
MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
|
|
|
|
MachineInstr *CPEMI =
|
|
BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
|
|
.addImm(i).addConstantPoolIndex(i).addImm(Size);
|
|
|
|
CPEMIs.push_back(CPEMI);
|
|
|
|
// Ensure that future entries with higher alignment get inserted before
|
|
// CPEMI. This is bucket sort with iterators.
|
|
for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
|
|
if (InsPoint[a] == InsAt)
|
|
InsPoint[a] = CPEMI;
|
|
// Add a new CPEntry, but no corresponding CPUser yet.
|
|
CPEntries.emplace_back(1, CPEntry(CPEMI, i));
|
|
++NumCPEs;
|
|
DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
|
|
<< Size << ", align = " << Align <<'\n');
|
|
}
|
|
DEBUG(BB->dump());
|
|
}
|
|
|
|
/// BBHasFallthrough - Return true if the specified basic block can fallthrough
|
|
/// into the block immediately after it.
|
|
static bool BBHasFallthrough(MachineBasicBlock *MBB) {
|
|
// Get the next machine basic block in the function.
|
|
MachineFunction::iterator MBBI = MBB;
|
|
// Can't fall off end of function.
|
|
if (std::next(MBBI) == MBB->getParent()->end())
|
|
return false;
|
|
|
|
MachineBasicBlock *NextBB = std::next(MBBI);
|
|
for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
|
|
E = MBB->succ_end(); I != E; ++I)
|
|
if (*I == NextBB)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
|
|
/// look up the corresponding CPEntry.
|
|
MipsConstantIslands::CPEntry
|
|
*MipsConstantIslands::findConstPoolEntry(unsigned CPI,
|
|
const MachineInstr *CPEMI) {
|
|
std::vector<CPEntry> &CPEs = CPEntries[CPI];
|
|
// Number of entries per constpool index should be small, just do a
|
|
// linear search.
|
|
for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
|
|
if (CPEs[i].CPEMI == CPEMI)
|
|
return &CPEs[i];
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// getCPELogAlign - Returns the required alignment of the constant pool entry
|
|
/// represented by CPEMI. Alignment is measured in log2(bytes) units.
|
|
unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
|
|
assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
|
|
|
|
// Everything is 4-byte aligned unless AlignConstantIslands is set.
|
|
if (!AlignConstantIslands)
|
|
return 2;
|
|
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
|
|
unsigned Align = MCP->getConstants()[CPI].getAlignment();
|
|
assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
|
|
return Log2_32(Align);
|
|
}
|
|
|
|
/// initializeFunctionInfo - Do the initial scan of the function, building up
|
|
/// information about the sizes of each block, the location of all the water,
|
|
/// and finding all of the constant pool users.
|
|
void MipsConstantIslands::
|
|
initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
|
|
BBInfo.clear();
|
|
BBInfo.resize(MF->getNumBlockIDs());
|
|
|
|
// First thing, compute the size of all basic blocks, and see if the function
|
|
// has any inline assembly in it. If so, we have to be conservative about
|
|
// alignment assumptions, as we don't know for sure the size of any
|
|
// instructions in the inline assembly.
|
|
for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
|
|
computeBlockSize(I);
|
|
|
|
|
|
// Compute block offsets.
|
|
adjustBBOffsetsAfter(MF->begin());
|
|
|
|
// Now go back through the instructions and build up our data structures.
|
|
for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
|
|
MBBI != E; ++MBBI) {
|
|
MachineBasicBlock &MBB = *MBBI;
|
|
|
|
// If this block doesn't fall through into the next MBB, then this is
|
|
// 'water' that a constant pool island could be placed.
|
|
if (!BBHasFallthrough(&MBB))
|
|
WaterList.push_back(&MBB);
|
|
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
|
|
I != E; ++I) {
|
|
if (I->isDebugValue())
|
|
continue;
|
|
|
|
int Opc = I->getOpcode();
|
|
if (I->isBranch()) {
|
|
bool isCond = false;
|
|
unsigned Bits = 0;
|
|
unsigned Scale = 1;
|
|
int UOpc = Opc;
|
|
switch (Opc) {
|
|
default:
|
|
continue; // Ignore other branches for now
|
|
case Mips::Bimm16:
|
|
Bits = 11;
|
|
Scale = 2;
|
|
isCond = false;
|
|
break;
|
|
case Mips::BimmX16:
|
|
Bits = 16;
|
|
Scale = 2;
|
|
isCond = false;
|
|
break;
|
|
case Mips::BeqzRxImm16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 8;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::BeqzRxImmX16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 16;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::BnezRxImm16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 8;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::BnezRxImmX16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 16;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::Bteqz16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 8;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::BteqzX16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 16;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::Btnez16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 8;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
case Mips::BtnezX16:
|
|
UOpc=Mips::Bimm16;
|
|
Bits = 16;
|
|
Scale = 2;
|
|
isCond = true;
|
|
break;
|
|
}
|
|
// Record this immediate branch.
|
|
unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
|
|
ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
|
|
}
|
|
|
|
if (Opc == Mips::CONSTPOOL_ENTRY)
|
|
continue;
|
|
|
|
|
|
// Scan the instructions for constant pool operands.
|
|
for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
|
|
if (I->getOperand(op).isCPI()) {
|
|
|
|
// We found one. The addressing mode tells us the max displacement
|
|
// from the PC that this instruction permits.
|
|
|
|
// Basic size info comes from the TSFlags field.
|
|
unsigned Bits = 0;
|
|
unsigned Scale = 1;
|
|
bool NegOk = false;
|
|
unsigned LongFormBits = 0;
|
|
unsigned LongFormScale = 0;
|
|
unsigned LongFormOpcode = 0;
|
|
switch (Opc) {
|
|
default:
|
|
llvm_unreachable("Unknown addressing mode for CP reference!");
|
|
case Mips::LwRxPcTcp16:
|
|
Bits = 8;
|
|
Scale = 4;
|
|
LongFormOpcode = Mips::LwRxPcTcpX16;
|
|
LongFormBits = 14;
|
|
LongFormScale = 1;
|
|
break;
|
|
case Mips::LwRxPcTcpX16:
|
|
Bits = 14;
|
|
Scale = 1;
|
|
NegOk = true;
|
|
break;
|
|
}
|
|
// Remember that this is a user of a CP entry.
|
|
unsigned CPI = I->getOperand(op).getIndex();
|
|
MachineInstr *CPEMI = CPEMIs[CPI];
|
|
unsigned MaxOffs = ((1 << Bits)-1) * Scale;
|
|
unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
|
|
CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
|
|
LongFormMaxOffs, LongFormOpcode));
|
|
|
|
// Increment corresponding CPEntry reference count.
|
|
CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
|
|
assert(CPE && "Cannot find a corresponding CPEntry!");
|
|
CPE->RefCount++;
|
|
|
|
// Instructions can only use one CP entry, don't bother scanning the
|
|
// rest of the operands.
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
/// computeBlockSize - Compute the size and some alignment information for MBB.
|
|
/// This function updates BBInfo directly.
|
|
void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
|
|
BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
|
|
BBI.Size = 0;
|
|
|
|
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
|
|
++I)
|
|
BBI.Size += TII->GetInstSizeInBytes(I);
|
|
|
|
}
|
|
|
|
/// getOffsetOf - Return the current offset of the specified machine instruction
|
|
/// from the start of the function. This offset changes as stuff is moved
|
|
/// around inside the function.
|
|
unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
|
|
// The offset is composed of two things: the sum of the sizes of all MBB's
|
|
// before this instruction's block, and the offset from the start of the block
|
|
// it is in.
|
|
unsigned Offset = BBInfo[MBB->getNumber()].Offset;
|
|
|
|
// Sum instructions before MI in MBB.
|
|
for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
|
|
assert(I != MBB->end() && "Didn't find MI in its own basic block?");
|
|
Offset += TII->GetInstSizeInBytes(I);
|
|
}
|
|
return Offset;
|
|
}
|
|
|
|
/// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
|
|
/// ID.
|
|
static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
|
|
const MachineBasicBlock *RHS) {
|
|
return LHS->getNumber() < RHS->getNumber();
|
|
}
|
|
|
|
/// updateForInsertedWaterBlock - When a block is newly inserted into the
|
|
/// machine function, it upsets all of the block numbers. Renumber the blocks
|
|
/// and update the arrays that parallel this numbering.
|
|
void MipsConstantIslands::updateForInsertedWaterBlock
|
|
(MachineBasicBlock *NewBB) {
|
|
// Renumber the MBB's to keep them consecutive.
|
|
NewBB->getParent()->RenumberBlocks(NewBB);
|
|
|
|
// Insert an entry into BBInfo to align it properly with the (newly
|
|
// renumbered) block numbers.
|
|
BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
|
|
|
|
// Next, update WaterList. Specifically, we need to add NewMBB as having
|
|
// available water after it.
|
|
water_iterator IP =
|
|
std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
|
|
CompareMBBNumbers);
|
|
WaterList.insert(IP, NewBB);
|
|
}
|
|
|
|
unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
|
|
return getOffsetOf(U.MI);
|
|
}
|
|
|
|
/// Split the basic block containing MI into two blocks, which are joined by
|
|
/// an unconditional branch. Update data structures and renumber blocks to
|
|
/// account for this change and returns the newly created block.
|
|
MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
|
|
(MachineInstr *MI) {
|
|
MachineBasicBlock *OrigBB = MI->getParent();
|
|
|
|
// Create a new MBB for the code after the OrigBB.
|
|
MachineBasicBlock *NewBB =
|
|
MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
|
|
MachineFunction::iterator MBBI = OrigBB; ++MBBI;
|
|
MF->insert(MBBI, NewBB);
|
|
|
|
// Splice the instructions starting with MI over to NewBB.
|
|
NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
|
|
|
|
// Add an unconditional branch from OrigBB to NewBB.
|
|
// Note the new unconditional branch is not being recorded.
|
|
// There doesn't seem to be meaningful DebugInfo available; this doesn't
|
|
// correspond to anything in the source.
|
|
BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
|
|
++NumSplit;
|
|
|
|
// Update the CFG. All succs of OrigBB are now succs of NewBB.
|
|
NewBB->transferSuccessors(OrigBB);
|
|
|
|
// OrigBB branches to NewBB.
|
|
OrigBB->addSuccessor(NewBB);
|
|
|
|
// Update internal data structures to account for the newly inserted MBB.
|
|
// This is almost the same as updateForInsertedWaterBlock, except that
|
|
// the Water goes after OrigBB, not NewBB.
|
|
MF->RenumberBlocks(NewBB);
|
|
|
|
// Insert an entry into BBInfo to align it properly with the (newly
|
|
// renumbered) block numbers.
|
|
BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
|
|
|
|
// Next, update WaterList. Specifically, we need to add OrigMBB as having
|
|
// available water after it (but not if it's already there, which happens
|
|
// when splitting before a conditional branch that is followed by an
|
|
// unconditional branch - in that case we want to insert NewBB).
|
|
water_iterator IP =
|
|
std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
|
|
CompareMBBNumbers);
|
|
MachineBasicBlock* WaterBB = *IP;
|
|
if (WaterBB == OrigBB)
|
|
WaterList.insert(std::next(IP), NewBB);
|
|
else
|
|
WaterList.insert(IP, OrigBB);
|
|
NewWaterList.insert(OrigBB);
|
|
|
|
// Figure out how large the OrigBB is. As the first half of the original
|
|
// block, it cannot contain a tablejump. The size includes
|
|
// the new jump we added. (It should be possible to do this without
|
|
// recounting everything, but it's very confusing, and this is rarely
|
|
// executed.)
|
|
computeBlockSize(OrigBB);
|
|
|
|
// Figure out how large the NewMBB is. As the second half of the original
|
|
// block, it may contain a tablejump.
|
|
computeBlockSize(NewBB);
|
|
|
|
// All BBOffsets following these blocks must be modified.
|
|
adjustBBOffsetsAfter(OrigBB);
|
|
|
|
return NewBB;
|
|
}
|
|
|
|
|
|
|
|
/// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
|
|
/// reference) is within MaxDisp of TrialOffset (a proposed location of a
|
|
/// constant pool entry).
|
|
bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
|
|
unsigned TrialOffset, unsigned MaxDisp,
|
|
bool NegativeOK) {
|
|
if (UserOffset <= TrialOffset) {
|
|
// User before the Trial.
|
|
if (TrialOffset - UserOffset <= MaxDisp)
|
|
return true;
|
|
} else if (NegativeOK) {
|
|
if (UserOffset - TrialOffset <= MaxDisp)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// isWaterInRange - Returns true if a CPE placed after the specified
|
|
/// Water (a basic block) will be in range for the specific MI.
|
|
///
|
|
/// Compute how much the function will grow by inserting a CPE after Water.
|
|
bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
|
|
MachineBasicBlock* Water, CPUser &U,
|
|
unsigned &Growth) {
|
|
unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
|
|
unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
|
|
unsigned NextBlockOffset, NextBlockAlignment;
|
|
MachineFunction::const_iterator NextBlock = Water;
|
|
if (++NextBlock == MF->end()) {
|
|
NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
|
|
NextBlockAlignment = 0;
|
|
} else {
|
|
NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
|
|
NextBlockAlignment = NextBlock->getAlignment();
|
|
}
|
|
unsigned Size = U.CPEMI->getOperand(2).getImm();
|
|
unsigned CPEEnd = CPEOffset + Size;
|
|
|
|
// The CPE may be able to hide in the alignment padding before the next
|
|
// block. It may also cause more padding to be required if it is more aligned
|
|
// that the next block.
|
|
if (CPEEnd > NextBlockOffset) {
|
|
Growth = CPEEnd - NextBlockOffset;
|
|
// Compute the padding that would go at the end of the CPE to align the next
|
|
// block.
|
|
Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
|
|
|
|
// If the CPE is to be inserted before the instruction, that will raise
|
|
// the offset of the instruction. Also account for unknown alignment padding
|
|
// in blocks between CPE and the user.
|
|
if (CPEOffset < UserOffset)
|
|
UserOffset += Growth;
|
|
} else
|
|
// CPE fits in existing padding.
|
|
Growth = 0;
|
|
|
|
return isOffsetInRange(UserOffset, CPEOffset, U);
|
|
}
|
|
|
|
/// isCPEntryInRange - Returns true if the distance between specific MI and
|
|
/// specific ConstPool entry instruction can fit in MI's displacement field.
|
|
bool MipsConstantIslands::isCPEntryInRange
|
|
(MachineInstr *MI, unsigned UserOffset,
|
|
MachineInstr *CPEMI, unsigned MaxDisp,
|
|
bool NegOk, bool DoDump) {
|
|
unsigned CPEOffset = getOffsetOf(CPEMI);
|
|
|
|
if (DoDump) {
|
|
DEBUG({
|
|
unsigned Block = MI->getParent()->getNumber();
|
|
const BasicBlockInfo &BBI = BBInfo[Block];
|
|
dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
|
|
<< " max delta=" << MaxDisp
|
|
<< format(" insn address=%#x", UserOffset)
|
|
<< " in BB#" << Block << ": "
|
|
<< format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
|
|
<< format("CPE address=%#x offset=%+d: ", CPEOffset,
|
|
int(CPEOffset-UserOffset));
|
|
});
|
|
}
|
|
|
|
return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
|
|
/// unconditionally branches to its only successor.
|
|
static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
|
|
if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
|
|
return false;
|
|
MachineBasicBlock *Succ = *MBB->succ_begin();
|
|
MachineBasicBlock *Pred = *MBB->pred_begin();
|
|
MachineInstr *PredMI = &Pred->back();
|
|
if (PredMI->getOpcode() == Mips::Bimm16)
|
|
return PredMI->getOperand(0).getMBB() == Succ;
|
|
return false;
|
|
}
|
|
#endif
|
|
|
|
void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
|
|
unsigned BBNum = BB->getNumber();
|
|
for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
|
|
// Get the offset and known bits at the end of the layout predecessor.
|
|
// Include the alignment of the current block.
|
|
unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
|
|
BBInfo[i].Offset = Offset;
|
|
}
|
|
}
|
|
|
|
/// decrementCPEReferenceCount - find the constant pool entry with index CPI
|
|
/// and instruction CPEMI, and decrement its refcount. If the refcount
|
|
/// becomes 0 remove the entry and instruction. Returns true if we removed
|
|
/// the entry, false if we didn't.
|
|
|
|
bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
|
|
MachineInstr *CPEMI) {
|
|
// Find the old entry. Eliminate it if it is no longer used.
|
|
CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
|
|
assert(CPE && "Unexpected!");
|
|
if (--CPE->RefCount == 0) {
|
|
removeDeadCPEMI(CPEMI);
|
|
CPE->CPEMI = nullptr;
|
|
--NumCPEs;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
|
|
/// if not, see if an in-range clone of the CPE is in range, and if so,
|
|
/// change the data structures so the user references the clone. Returns:
|
|
/// 0 = no existing entry found
|
|
/// 1 = entry found, and there were no code insertions or deletions
|
|
/// 2 = entry found, and there were code insertions or deletions
|
|
int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
|
|
{
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
|
|
// Check to see if the CPE is already in-range.
|
|
if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
|
|
true)) {
|
|
DEBUG(dbgs() << "In range\n");
|
|
return 1;
|
|
}
|
|
|
|
// No. Look for previously created clones of the CPE that are in range.
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
std::vector<CPEntry> &CPEs = CPEntries[CPI];
|
|
for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
|
|
// We already tried this one
|
|
if (CPEs[i].CPEMI == CPEMI)
|
|
continue;
|
|
// Removing CPEs can leave empty entries, skip
|
|
if (CPEs[i].CPEMI == nullptr)
|
|
continue;
|
|
if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
|
|
U.NegOk)) {
|
|
DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
|
|
<< CPEs[i].CPI << "\n");
|
|
// Point the CPUser node to the replacement
|
|
U.CPEMI = CPEs[i].CPEMI;
|
|
// Change the CPI in the instruction operand to refer to the clone.
|
|
for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
|
|
if (UserMI->getOperand(j).isCPI()) {
|
|
UserMI->getOperand(j).setIndex(CPEs[i].CPI);
|
|
break;
|
|
}
|
|
// Adjust the refcount of the clone...
|
|
CPEs[i].RefCount++;
|
|
// ...and the original. If we didn't remove the old entry, none of the
|
|
// addresses changed, so we don't need another pass.
|
|
return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
|
|
/// This version checks if the longer form of the instruction can be used to
|
|
/// to satisfy things.
|
|
/// if not, see if an in-range clone of the CPE is in range, and if so,
|
|
/// change the data structures so the user references the clone. Returns:
|
|
/// 0 = no existing entry found
|
|
/// 1 = entry found, and there were no code insertions or deletions
|
|
/// 2 = entry found, and there were code insertions or deletions
|
|
int MipsConstantIslands::findLongFormInRangeCPEntry
|
|
(CPUser& U, unsigned UserOffset)
|
|
{
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
|
|
// Check to see if the CPE is already in-range.
|
|
if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
|
|
U.getLongFormMaxDisp(), U.NegOk,
|
|
true)) {
|
|
DEBUG(dbgs() << "In range\n");
|
|
UserMI->setDesc(TII->get(U.getLongFormOpcode()));
|
|
U.setMaxDisp(U.getLongFormMaxDisp());
|
|
return 2; // instruction is longer length now
|
|
}
|
|
|
|
// No. Look for previously created clones of the CPE that are in range.
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
std::vector<CPEntry> &CPEs = CPEntries[CPI];
|
|
for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
|
|
// We already tried this one
|
|
if (CPEs[i].CPEMI == CPEMI)
|
|
continue;
|
|
// Removing CPEs can leave empty entries, skip
|
|
if (CPEs[i].CPEMI == nullptr)
|
|
continue;
|
|
if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
|
|
U.getLongFormMaxDisp(), U.NegOk)) {
|
|
DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
|
|
<< CPEs[i].CPI << "\n");
|
|
// Point the CPUser node to the replacement
|
|
U.CPEMI = CPEs[i].CPEMI;
|
|
// Change the CPI in the instruction operand to refer to the clone.
|
|
for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
|
|
if (UserMI->getOperand(j).isCPI()) {
|
|
UserMI->getOperand(j).setIndex(CPEs[i].CPI);
|
|
break;
|
|
}
|
|
// Adjust the refcount of the clone...
|
|
CPEs[i].RefCount++;
|
|
// ...and the original. If we didn't remove the old entry, none of the
|
|
// addresses changed, so we don't need another pass.
|
|
return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
|
|
/// the specific unconditional branch instruction.
|
|
static inline unsigned getUnconditionalBrDisp(int Opc) {
|
|
switch (Opc) {
|
|
case Mips::Bimm16:
|
|
return ((1<<10)-1)*2;
|
|
case Mips::BimmX16:
|
|
return ((1<<16)-1)*2;
|
|
default:
|
|
break;
|
|
}
|
|
return ((1<<16)-1)*2;
|
|
}
|
|
|
|
/// findAvailableWater - Look for an existing entry in the WaterList in which
|
|
/// we can place the CPE referenced from U so it's within range of U's MI.
|
|
/// Returns true if found, false if not. If it returns true, WaterIter
|
|
/// is set to the WaterList entry.
|
|
/// To ensure that this pass
|
|
/// terminates, the CPE location for a particular CPUser is only allowed to
|
|
/// move to a lower address, so search backward from the end of the list and
|
|
/// prefer the first water that is in range.
|
|
bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
|
|
water_iterator &WaterIter) {
|
|
if (WaterList.empty())
|
|
return false;
|
|
|
|
unsigned BestGrowth = ~0u;
|
|
for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();;
|
|
--IP) {
|
|
MachineBasicBlock* WaterBB = *IP;
|
|
// Check if water is in range and is either at a lower address than the
|
|
// current "high water mark" or a new water block that was created since
|
|
// the previous iteration by inserting an unconditional branch. In the
|
|
// latter case, we want to allow resetting the high water mark back to
|
|
// this new water since we haven't seen it before. Inserting branches
|
|
// should be relatively uncommon and when it does happen, we want to be
|
|
// sure to take advantage of it for all the CPEs near that block, so that
|
|
// we don't insert more branches than necessary.
|
|
unsigned Growth;
|
|
if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
|
|
(WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
|
|
NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
|
|
// This is the least amount of required padding seen so far.
|
|
BestGrowth = Growth;
|
|
WaterIter = IP;
|
|
DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
|
|
<< " Growth=" << Growth << '\n');
|
|
|
|
// Keep looking unless it is perfect.
|
|
if (BestGrowth == 0)
|
|
return true;
|
|
}
|
|
if (IP == B)
|
|
break;
|
|
}
|
|
return BestGrowth != ~0u;
|
|
}
|
|
|
|
/// createNewWater - No existing WaterList entry will work for
|
|
/// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
|
|
/// block is used if in range, and the conditional branch munged so control
|
|
/// flow is correct. Otherwise the block is split to create a hole with an
|
|
/// unconditional branch around it. In either case NewMBB is set to a
|
|
/// block following which the new island can be inserted (the WaterList
|
|
/// is not adjusted).
|
|
void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
|
|
unsigned UserOffset,
|
|
MachineBasicBlock *&NewMBB) {
|
|
CPUser &U = CPUsers[CPUserIndex];
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
unsigned CPELogAlign = getCPELogAlign(CPEMI);
|
|
MachineBasicBlock *UserMBB = UserMI->getParent();
|
|
const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
|
|
|
|
// If the block does not end in an unconditional branch already, and if the
|
|
// end of the block is within range, make new water there.
|
|
if (BBHasFallthrough(UserMBB)) {
|
|
// Size of branch to insert.
|
|
unsigned Delta = 2;
|
|
// Compute the offset where the CPE will begin.
|
|
unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
|
|
|
|
if (isOffsetInRange(UserOffset, CPEOffset, U)) {
|
|
DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
|
|
<< format(", expected CPE offset %#x\n", CPEOffset));
|
|
NewMBB = std::next(MachineFunction::iterator(UserMBB));
|
|
// Add an unconditional branch from UserMBB to fallthrough block. Record
|
|
// it for branch lengthening; this new branch will not get out of range,
|
|
// but if the preceding conditional branch is out of range, the targets
|
|
// will be exchanged, and the altered branch may be out of range, so the
|
|
// machinery has to know about it.
|
|
int UncondBr = Mips::Bimm16;
|
|
BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
|
|
unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
|
|
ImmBranches.push_back(ImmBranch(&UserMBB->back(),
|
|
MaxDisp, false, UncondBr));
|
|
BBInfo[UserMBB->getNumber()].Size += Delta;
|
|
adjustBBOffsetsAfter(UserMBB);
|
|
return;
|
|
}
|
|
}
|
|
|
|
// What a big block. Find a place within the block to split it.
|
|
|
|
// Try to split the block so it's fully aligned. Compute the latest split
|
|
// point where we can add a 4-byte branch instruction, and then align to
|
|
// LogAlign which is the largest possible alignment in the function.
|
|
unsigned LogAlign = MF->getAlignment();
|
|
assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
|
|
unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
|
|
DEBUG(dbgs() << format("Split in middle of big block before %#x",
|
|
BaseInsertOffset));
|
|
|
|
// The 4 in the following is for the unconditional branch we'll be inserting
|
|
// Alignment of the island is handled
|
|
// inside isOffsetInRange.
|
|
BaseInsertOffset -= 4;
|
|
|
|
DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
|
|
<< " la=" << LogAlign << '\n');
|
|
|
|
// This could point off the end of the block if we've already got constant
|
|
// pool entries following this block; only the last one is in the water list.
|
|
// Back past any possible branches (allow for a conditional and a maximally
|
|
// long unconditional).
|
|
if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
|
|
BaseInsertOffset = UserBBI.postOffset() - 8;
|
|
DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
|
|
}
|
|
unsigned EndInsertOffset = BaseInsertOffset + 4 +
|
|
CPEMI->getOperand(2).getImm();
|
|
MachineBasicBlock::iterator MI = UserMI;
|
|
++MI;
|
|
unsigned CPUIndex = CPUserIndex+1;
|
|
unsigned NumCPUsers = CPUsers.size();
|
|
//MachineInstr *LastIT = 0;
|
|
for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
|
|
Offset < BaseInsertOffset;
|
|
Offset += TII->GetInstSizeInBytes(MI), MI = std::next(MI)) {
|
|
assert(MI != UserMBB->end() && "Fell off end of block");
|
|
if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
|
|
CPUser &U = CPUsers[CPUIndex];
|
|
if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
|
|
// Shift intertion point by one unit of alignment so it is within reach.
|
|
BaseInsertOffset -= 1u << LogAlign;
|
|
EndInsertOffset -= 1u << LogAlign;
|
|
}
|
|
// This is overly conservative, as we don't account for CPEMIs being
|
|
// reused within the block, but it doesn't matter much. Also assume CPEs
|
|
// are added in order with alignment padding. We may eventually be able
|
|
// to pack the aligned CPEs better.
|
|
EndInsertOffset += U.CPEMI->getOperand(2).getImm();
|
|
CPUIndex++;
|
|
}
|
|
}
|
|
|
|
--MI;
|
|
NewMBB = splitBlockBeforeInstr(MI);
|
|
}
|
|
|
|
/// handleConstantPoolUser - Analyze the specified user, checking to see if it
|
|
/// is out-of-range. If so, pick up the constant pool value and move it some
|
|
/// place in-range. Return true if we changed any addresses (thus must run
|
|
/// another pass of branch lengthening), false otherwise.
|
|
bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
|
|
CPUser &U = CPUsers[CPUserIndex];
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
unsigned Size = CPEMI->getOperand(2).getImm();
|
|
// Compute this only once, it's expensive.
|
|
unsigned UserOffset = getUserOffset(U);
|
|
|
|
// See if the current entry is within range, or there is a clone of it
|
|
// in range.
|
|
int result = findInRangeCPEntry(U, UserOffset);
|
|
if (result==1) return false;
|
|
else if (result==2) return true;
|
|
|
|
|
|
// Look for water where we can place this CPE.
|
|
MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
|
|
MachineBasicBlock *NewMBB;
|
|
water_iterator IP;
|
|
if (findAvailableWater(U, UserOffset, IP)) {
|
|
DEBUG(dbgs() << "Found water in range\n");
|
|
MachineBasicBlock *WaterBB = *IP;
|
|
|
|
// If the original WaterList entry was "new water" on this iteration,
|
|
// propagate that to the new island. This is just keeping NewWaterList
|
|
// updated to match the WaterList, which will be updated below.
|
|
if (NewWaterList.erase(WaterBB))
|
|
NewWaterList.insert(NewIsland);
|
|
|
|
// The new CPE goes before the following block (NewMBB).
|
|
NewMBB = std::next(MachineFunction::iterator(WaterBB));
|
|
|
|
} else {
|
|
// No water found.
|
|
// we first see if a longer form of the instrucion could have reached
|
|
// the constant. in that case we won't bother to split
|
|
if (!NoLoadRelaxation) {
|
|
result = findLongFormInRangeCPEntry(U, UserOffset);
|
|
if (result != 0) return true;
|
|
}
|
|
DEBUG(dbgs() << "No water found\n");
|
|
createNewWater(CPUserIndex, UserOffset, NewMBB);
|
|
|
|
// splitBlockBeforeInstr adds to WaterList, which is important when it is
|
|
// called while handling branches so that the water will be seen on the
|
|
// next iteration for constant pools, but in this context, we don't want
|
|
// it. Check for this so it will be removed from the WaterList.
|
|
// Also remove any entry from NewWaterList.
|
|
MachineBasicBlock *WaterBB = std::prev(MachineFunction::iterator(NewMBB));
|
|
IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
|
|
if (IP != WaterList.end())
|
|
NewWaterList.erase(WaterBB);
|
|
|
|
// We are adding new water. Update NewWaterList.
|
|
NewWaterList.insert(NewIsland);
|
|
}
|
|
|
|
// Remove the original WaterList entry; we want subsequent insertions in
|
|
// this vicinity to go after the one we're about to insert. This
|
|
// considerably reduces the number of times we have to move the same CPE
|
|
// more than once and is also important to ensure the algorithm terminates.
|
|
if (IP != WaterList.end())
|
|
WaterList.erase(IP);
|
|
|
|
// Okay, we know we can put an island before NewMBB now, do it!
|
|
MF->insert(NewMBB, NewIsland);
|
|
|
|
// Update internal data structures to account for the newly inserted MBB.
|
|
updateForInsertedWaterBlock(NewIsland);
|
|
|
|
// Decrement the old entry, and remove it if refcount becomes 0.
|
|
decrementCPEReferenceCount(CPI, CPEMI);
|
|
|
|
// No existing clone of this CPE is within range.
|
|
// We will be generating a new clone. Get a UID for it.
|
|
unsigned ID = createPICLabelUId();
|
|
|
|
// Now that we have an island to add the CPE to, clone the original CPE and
|
|
// add it to the island.
|
|
U.HighWaterMark = NewIsland;
|
|
U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
|
|
.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
|
|
CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
|
|
++NumCPEs;
|
|
|
|
// Mark the basic block as aligned as required by the const-pool entry.
|
|
NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
|
|
|
|
// Increase the size of the island block to account for the new entry.
|
|
BBInfo[NewIsland->getNumber()].Size += Size;
|
|
adjustBBOffsetsAfter(std::prev(MachineFunction::iterator(NewIsland)));
|
|
|
|
|
|
|
|
// Finally, change the CPI in the instruction operand to be ID.
|
|
for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
|
|
if (UserMI->getOperand(i).isCPI()) {
|
|
UserMI->getOperand(i).setIndex(ID);
|
|
break;
|
|
}
|
|
|
|
DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
|
|
<< format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
|
|
|
|
return true;
|
|
}
|
|
|
|
/// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
|
|
/// sizes and offsets of impacted basic blocks.
|
|
void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
|
|
MachineBasicBlock *CPEBB = CPEMI->getParent();
|
|
unsigned Size = CPEMI->getOperand(2).getImm();
|
|
CPEMI->eraseFromParent();
|
|
BBInfo[CPEBB->getNumber()].Size -= Size;
|
|
// All succeeding offsets have the current size value added in, fix this.
|
|
if (CPEBB->empty()) {
|
|
BBInfo[CPEBB->getNumber()].Size = 0;
|
|
|
|
// This block no longer needs to be aligned.
|
|
CPEBB->setAlignment(0);
|
|
} else
|
|
// Entries are sorted by descending alignment, so realign from the front.
|
|
CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
|
|
|
|
adjustBBOffsetsAfter(CPEBB);
|
|
// An island has only one predecessor BB and one successor BB. Check if
|
|
// this BB's predecessor jumps directly to this BB's successor. This
|
|
// shouldn't happen currently.
|
|
assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
|
|
// FIXME: remove the empty blocks after all the work is done?
|
|
}
|
|
|
|
/// removeUnusedCPEntries - Remove constant pool entries whose refcounts
|
|
/// are zero.
|
|
bool MipsConstantIslands::removeUnusedCPEntries() {
|
|
unsigned MadeChange = false;
|
|
for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
|
|
std::vector<CPEntry> &CPEs = CPEntries[i];
|
|
for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
|
|
if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
|
|
removeDeadCPEMI(CPEs[j].CPEMI);
|
|
CPEs[j].CPEMI = nullptr;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
}
|
|
return MadeChange;
|
|
}
|
|
|
|
/// isBBInRange - Returns true if the distance between specific MI and
|
|
/// specific BB can fit in MI's displacement field.
|
|
bool MipsConstantIslands::isBBInRange
|
|
(MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
|
|
|
|
unsigned PCAdj = 4;
|
|
|
|
unsigned BrOffset = getOffsetOf(MI) + PCAdj;
|
|
unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
|
|
|
|
DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
|
|
<< " from BB#" << MI->getParent()->getNumber()
|
|
<< " max delta=" << MaxDisp
|
|
<< " from " << getOffsetOf(MI) << " to " << DestOffset
|
|
<< " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
|
|
|
|
if (BrOffset <= DestOffset) {
|
|
// Branch before the Dest.
|
|
if (DestOffset-BrOffset <= MaxDisp)
|
|
return true;
|
|
} else {
|
|
if (BrOffset-DestOffset <= MaxDisp)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// fixupImmediateBr - Fix up an immediate branch whose destination is too far
|
|
/// away to fit in its displacement field.
|
|
bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
|
|
MachineInstr *MI = Br.MI;
|
|
unsigned TargetOperand = branchTargetOperand(MI);
|
|
MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
|
|
|
|
// Check to see if the DestBB is already in-range.
|
|
if (isBBInRange(MI, DestBB, Br.MaxDisp))
|
|
return false;
|
|
|
|
if (!Br.isCond)
|
|
return fixupUnconditionalBr(Br);
|
|
return fixupConditionalBr(Br);
|
|
}
|
|
|
|
/// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
|
|
/// too far away to fit in its displacement field. If the LR register has been
|
|
/// spilled in the epilogue, then we can use BL to implement a far jump.
|
|
/// Otherwise, add an intermediate branch instruction to a branch.
|
|
bool
|
|
MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
|
|
MachineInstr *MI = Br.MI;
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
|
|
// Use BL to implement far jump.
|
|
unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2;
|
|
if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) {
|
|
Br.MaxDisp = BimmX16MaxDisp;
|
|
MI->setDesc(TII->get(Mips::BimmX16));
|
|
}
|
|
else {
|
|
// need to give the math a more careful look here
|
|
// this is really a segment address and not
|
|
// a PC relative address. FIXME. But I think that
|
|
// just reducing the bits by 1 as I've done is correct.
|
|
// The basic block we are branching too much be longword aligned.
|
|
// we know that RA is saved because we always save it right now.
|
|
// this requirement will be relaxed later but we also have an alternate
|
|
// way to implement this that I will implement that does not need jal.
|
|
// We should have a way to back out this alignment restriction if we "can" later.
|
|
// but it is not harmful.
|
|
//
|
|
DestBB->setAlignment(2);
|
|
Br.MaxDisp = ((1<<24)-1) * 2;
|
|
MI->setDesc(TII->get(Mips::JalB16));
|
|
}
|
|
BBInfo[MBB->getNumber()].Size += 2;
|
|
adjustBBOffsetsAfter(MBB);
|
|
HasFarJump = true;
|
|
++NumUBrFixed;
|
|
|
|
DEBUG(dbgs() << " Changed B to long jump " << *MI);
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
/// fixupConditionalBr - Fix up a conditional branch whose destination is too
|
|
/// far away to fit in its displacement field. It is converted to an inverse
|
|
/// conditional branch + an unconditional branch to the destination.
|
|
bool
|
|
MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
|
|
MachineInstr *MI = Br.MI;
|
|
unsigned TargetOperand = branchTargetOperand(MI);
|
|
MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
|
|
unsigned Opcode = MI->getOpcode();
|
|
unsigned LongFormOpcode = longformBranchOpcode(Opcode);
|
|
unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
|
|
|
|
// Check to see if the DestBB is already in-range.
|
|
if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
|
|
Br.MaxDisp = LongFormMaxOff;
|
|
MI->setDesc(TII->get(LongFormOpcode));
|
|
return true;
|
|
}
|
|
|
|
// Add an unconditional branch to the destination and invert the branch
|
|
// condition to jump over it:
|
|
// bteqz L1
|
|
// =>
|
|
// bnez L2
|
|
// b L1
|
|
// L2:
|
|
|
|
// If the branch is at the end of its MBB and that has a fall-through block,
|
|
// direct the updated conditional branch to the fall-through block. Otherwise,
|
|
// split the MBB before the next instruction.
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
MachineInstr *BMI = &MBB->back();
|
|
bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
|
|
unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode);
|
|
|
|
++NumCBrFixed;
|
|
if (BMI != MI) {
|
|
if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) &&
|
|
isUnconditionalBranch(BMI->getOpcode())) {
|
|
// Last MI in the BB is an unconditional branch. Can we simply invert the
|
|
// condition and swap destinations:
|
|
// beqz L1
|
|
// b L2
|
|
// =>
|
|
// bnez L2
|
|
// b L1
|
|
unsigned BMITargetOperand = branchTargetOperand(BMI);
|
|
MachineBasicBlock *NewDest =
|
|
BMI->getOperand(BMITargetOperand).getMBB();
|
|
if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
|
|
DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
|
|
<< *BMI);
|
|
MI->setDesc(TII->get(OppositeBranchOpcode));
|
|
BMI->getOperand(BMITargetOperand).setMBB(DestBB);
|
|
MI->getOperand(TargetOperand).setMBB(NewDest);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
if (NeedSplit) {
|
|
splitBlockBeforeInstr(MI);
|
|
// No need for the branch to the next block. We're adding an unconditional
|
|
// branch to the destination.
|
|
int delta = TII->GetInstSizeInBytes(&MBB->back());
|
|
BBInfo[MBB->getNumber()].Size -= delta;
|
|
MBB->back().eraseFromParent();
|
|
// BBInfo[SplitBB].Offset is wrong temporarily, fixed below
|
|
}
|
|
MachineBasicBlock *NextBB = std::next(MachineFunction::iterator(MBB));
|
|
|
|
DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
|
|
<< " also invert condition and change dest. to BB#"
|
|
<< NextBB->getNumber() << "\n");
|
|
|
|
// Insert a new conditional branch and a new unconditional branch.
|
|
// Also update the ImmBranch as well as adding a new entry for the new branch.
|
|
if (MI->getNumExplicitOperands() == 2) {
|
|
BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
|
|
.addReg(MI->getOperand(0).getReg())
|
|
.addMBB(NextBB);
|
|
} else {
|
|
BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
|
|
.addMBB(NextBB);
|
|
}
|
|
Br.MI = &MBB->back();
|
|
BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
|
|
BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
|
|
BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
|
|
unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
|
|
ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
|
|
|
|
// Remove the old conditional branch. It may or may not still be in MBB.
|
|
BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
|
|
MI->eraseFromParent();
|
|
adjustBBOffsetsAfter(MBB);
|
|
return true;
|
|
}
|
|
|
|
|
|
void MipsConstantIslands::prescanForConstants() {
|
|
unsigned J = 0;
|
|
(void)J;
|
|
for (MachineFunction::iterator B =
|
|
MF->begin(), E = MF->end(); B != E; ++B) {
|
|
for (MachineBasicBlock::instr_iterator I =
|
|
B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
|
|
switch(I->getDesc().getOpcode()) {
|
|
case Mips::LwConstant32: {
|
|
PrescannedForConstants = true;
|
|
DEBUG(dbgs() << "constant island constant " << *I << "\n");
|
|
J = I->getNumOperands();
|
|
DEBUG(dbgs() << "num operands " << J << "\n");
|
|
MachineOperand& Literal = I->getOperand(1);
|
|
if (Literal.isImm()) {
|
|
int64_t V = Literal.getImm();
|
|
DEBUG(dbgs() << "literal " << V << "\n");
|
|
Type *Int32Ty =
|
|
Type::getInt32Ty(MF->getFunction()->getContext());
|
|
const Constant *C = ConstantInt::get(Int32Ty, V);
|
|
unsigned index = MCP->getConstantPoolIndex(C, 4);
|
|
I->getOperand(2).ChangeToImmediate(index);
|
|
DEBUG(dbgs() << "constant island constant " << *I << "\n");
|
|
I->setDesc(TII->get(Mips::LwRxPcTcp16));
|
|
I->RemoveOperand(1);
|
|
I->RemoveOperand(1);
|
|
I->addOperand(MachineOperand::CreateCPI(index, 0));
|
|
I->addOperand(MachineOperand::CreateImm(4));
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|