1 //===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 // This pass is used to make Pc relative loads of constants.
12 // For now, only Mips16 will use this.
14 // Loading constants inline is expensive on Mips16 and it's in general better
15 // to place the constant nearby in code space and then it can be loaded with a
16 // simple 16 bit load instruction.
18 // The constants can be not just numbers but addresses of functions and labels.
19 // This can be particularly helpful in static relocation mode for embedded
24 #define DEBUG_TYPE "mips-constant-islands"
27 #include "MCTargetDesc/MipsBaseInfo.h"
28 #include "MipsMachineFunction.h"
29 #include "MipsTargetMachine.h"
30 #include "llvm/ADT/Statistic.h"
31 #include "llvm/CodeGen/MachineBasicBlock.h"
32 #include "llvm/CodeGen/MachineFunctionPass.h"
33 #include "llvm/CodeGen/MachineInstrBuilder.h"
34 #include "llvm/CodeGen/MachineRegisterInfo.h"
35 #include "llvm/IR/Function.h"
36 #include "llvm/Support/CommandLine.h"
37 #include "llvm/Support/Debug.h"
38 #include "llvm/Support/InstIterator.h"
39 #include "llvm/Support/MathExtras.h"
40 #include "llvm/Support/raw_ostream.h"
41 #include "llvm/Target/TargetInstrInfo.h"
42 #include "llvm/Target/TargetMachine.h"
43 #include "llvm/Target/TargetRegisterInfo.h"
44 #include "llvm/Support/Format.h"
49 STATISTIC(NumCPEs, "Number of constpool entries");
50 STATISTIC(NumSplit, "Number of uncond branches inserted");
51 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
52 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
54 // FIXME: This option should be removed once it has received sufficient testing.
56 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
57 cl::desc("Align constant islands in code"));
60 // Rather than do make check tests with huge amounts of code, we force
61 // the test to use this amount.
63 static cl::opt<int> ConstantIslandsSmallOffset(
64 "mips-constant-islands-small-offset",
66 cl::desc("Make small offsets be this amount for testing purposes"),
69 /// UnknownPadding - Return the worst case padding that could result from
70 /// unknown offset bits. This does not include alignment padding caused by
71 /// known offset bits.
73 /// @param LogAlign log2(alignment)
74 /// @param KnownBits Number of known low offset bits.
75 static inline unsigned UnknownPadding(unsigned LogAlign, unsigned KnownBits) {
76 if (KnownBits < LogAlign)
77 return (1u << LogAlign) - (1u << KnownBits);
84 typedef MachineBasicBlock::iterator Iter;
85 typedef MachineBasicBlock::reverse_iterator ReverseIter;
87 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
88 /// requires constant pool entries to be scattered among the instructions
89 /// inside a function. To do this, it completely ignores the normal LLVM
90 /// constant pool; instead, it places constants wherever it feels like with
91 /// special instructions.
93 /// The terminology used in this pass includes:
94 /// Islands - Clumps of constants placed in the function.
95 /// Water - Potential places where an island could be formed.
96 /// CPE - A constant pool entry that has been placed somewhere, which
97 /// tracks a list of users.
99 class MipsConstantIslands : public MachineFunctionPass {
101 /// BasicBlockInfo - Information about the offset and size of a single
103 struct BasicBlockInfo {
104 /// Offset - Distance from the beginning of the function to the beginning
105 /// of this basic block.
107 /// Offsets are computed assuming worst case padding before an aligned
108 /// block. This means that subtracting basic block offsets always gives a
109 /// conservative estimate of the real distance which may be smaller.
111 /// Because worst case padding is used, the computed offset of an aligned
112 /// block may not actually be aligned.
115 /// Size - Size of the basic block in bytes. If the block contains
116 /// inline assembly, this is a worst case estimate.
118 /// The size does not include any alignment padding whether from the
119 /// beginning of the block, or from an aligned jump table at the end.
122 /// KnownBits - The number of low bits in Offset that are known to be
123 /// exact. The remaining bits of Offset are an upper bound.
126 /// Unalign - When non-zero, the block contains instructions (inline asm)
127 /// of unknown size. The real size may be smaller than Size bytes by a
128 /// multiple of 1 << Unalign.
131 /// PostAlign - When non-zero, the block terminator contains a .align
132 /// directive, so the end of the block is aligned to 1 << PostAlign
136 BasicBlockInfo() : Offset(0), Size(0), KnownBits(0), Unalign(0),
139 /// Compute the number of known offset bits internally to this block.
140 /// This number should be used to predict worst case padding when
141 /// splitting the block.
142 unsigned internalKnownBits() const {
143 unsigned Bits = Unalign ? Unalign : KnownBits;
144 // If the block size isn't a multiple of the known bits, assume the
145 // worst case padding.
146 if (Size & ((1u << Bits) - 1))
147 Bits = countTrailingZeros(Size);
151 /// Compute the offset immediately following this block. If LogAlign is
152 /// specified, return the offset the successor block will get if it has
154 unsigned postOffset(unsigned LogAlign = 0) const {
155 unsigned PO = Offset + Size;
159 /// Compute the number of known low bits of postOffset. If this block
160 /// contains inline asm, the number of known bits drops to the
161 /// instruction alignment. An aligned terminator may increase the number
163 /// If LogAlign is given, also consider the alignment of the next block.
164 unsigned postKnownBits(unsigned LogAlign = 0) const {
165 return std::max(std::max(unsigned(PostAlign), LogAlign),
166 internalKnownBits());
170 std::vector<BasicBlockInfo> BBInfo;
172 /// WaterList - A sorted list of basic blocks where islands could be placed
173 /// (i.e. blocks that don't fall through to the following block, due
174 /// to a return, unreachable, or unconditional branch).
175 std::vector<MachineBasicBlock*> WaterList;
177 /// NewWaterList - The subset of WaterList that was created since the
178 /// previous iteration by inserting unconditional branches.
179 SmallSet<MachineBasicBlock*, 4> NewWaterList;
181 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
183 /// CPUser - One user of a constant pool, keeping the machine instruction
184 /// pointer, the constant pool being referenced, and the max displacement
185 /// allowed from the instruction to the CP. The HighWaterMark records the
186 /// highest basic block where a new CPEntry can be placed. To ensure this
187 /// pass terminates, the CP entries are initially placed at the end of the
188 /// function and then move monotonically to lower addresses. The
189 /// exception to this rule is when the current CP entry for a particular
190 /// CPUser is out of range, but there is another CP entry for the same
191 /// constant value in range. We want to use the existing in-range CP
192 /// entry, but if it later moves out of range, the search for new water
193 /// should resume where it left off. The HighWaterMark is used to record
198 MachineBasicBlock *HighWaterMark;
201 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
202 // with different displacements
203 unsigned LongFormOpcode;
207 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
209 unsigned longformmaxdisp, unsigned longformopcode)
210 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
211 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
212 NegOk(neg), KnownAlignment(false) {
213 HighWaterMark = CPEMI->getParent();
215 /// getMaxDisp - Returns the maximum displacement supported by MI.
216 /// Correct for unknown alignment.
217 /// Conservatively subtract 2 bytes to handle weird alignment effects.
218 unsigned getMaxDisp() const {
219 unsigned xMaxDisp = ConstantIslandsSmallOffset?
220 ConstantIslandsSmallOffset: MaxDisp;
221 return (KnownAlignment ? xMaxDisp : xMaxDisp - 2) - 2;
223 unsigned getLongFormMaxDisp() const {
224 return (KnownAlignment ? LongFormMaxDisp : LongFormMaxDisp - 2) - 2;
226 unsigned getLongFormOpcode() const {
227 return LongFormOpcode;
231 /// CPUsers - Keep track of all of the machine instructions that use various
232 /// constant pools and their max displacement.
233 std::vector<CPUser> CPUsers;
235 /// CPEntry - One per constant pool entry, keeping the machine instruction
236 /// pointer, the constpool index, and the number of CPUser's which
237 /// reference this entry.
242 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
243 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
246 /// CPEntries - Keep track of all of the constant pool entry machine
247 /// instructions. For each original constpool index (i.e. those that
248 /// existed upon entry to this pass), it keeps a vector of entries.
249 /// Original elements are cloned as we go along; the clones are
250 /// put in the vector of the original element, but have distinct CPIs.
251 std::vector<std::vector<CPEntry> > CPEntries;
253 /// ImmBranch - One per immediate branch, keeping the machine instruction
254 /// pointer, conditional or unconditional, the max displacement,
255 /// and (if isCond is true) the corresponding unconditional branch
259 unsigned MaxDisp : 31;
262 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
263 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
266 /// ImmBranches - Keep track of all the immediate branch instructions.
268 std::vector<ImmBranch> ImmBranches;
270 /// HasFarJump - True if any far jump instruction has been emitted during
271 /// the branch fix up pass.
274 const TargetMachine &TM;
277 const MipsSubtarget *STI;
278 const MipsInstrInfo *TII;
279 MipsFunctionInfo *MFI;
281 MachineConstantPool *MCP;
283 unsigned PICLabelUId;
284 bool PrescannedForConstants;
286 void initPICLabelUId(unsigned UId) {
291 unsigned createPICLabelUId() {
292 return PICLabelUId++;
297 MipsConstantIslands(TargetMachine &tm)
298 : MachineFunctionPass(ID), TM(tm),
299 IsPIC(TM.getRelocationModel() == Reloc::PIC_),
300 ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
301 STI(&TM.getSubtarget<MipsSubtarget>()), MF(0), MCP(0),
302 PrescannedForConstants(false){}
304 virtual const char *getPassName() const {
305 return "Mips Constant Islands";
308 bool runOnMachineFunction(MachineFunction &F);
310 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
311 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
312 unsigned getCPELogAlign(const MachineInstr *CPEMI);
313 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
314 unsigned getOffsetOf(MachineInstr *MI) const;
315 unsigned getUserOffset(CPUser&) const;
319 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
320 unsigned Disp, bool NegativeOK);
321 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
324 bool isLongFormOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
327 void computeBlockSize(MachineBasicBlock *MBB);
328 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
329 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
330 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
331 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
332 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
333 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
334 bool findAvailableWater(CPUser&U, unsigned UserOffset,
335 water_iterator &WaterIter);
336 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
337 MachineBasicBlock *&NewMBB);
338 bool handleConstantPoolUser(unsigned CPUserIndex);
339 void removeDeadCPEMI(MachineInstr *CPEMI);
340 bool removeUnusedCPEntries();
341 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
342 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
343 bool DoDump = false);
344 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
345 CPUser &U, unsigned &Growth);
346 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
347 bool fixupImmediateBr(ImmBranch &Br);
348 bool fixupConditionalBr(ImmBranch &Br);
349 bool fixupUnconditionalBr(ImmBranch &Br);
351 void prescanForConstants();
357 char MipsConstantIslands::ID = 0;
358 } // end of anonymous namespace
361 bool MipsConstantIslands::isLongFormOffsetInRange
362 (unsigned UserOffset, unsigned TrialOffset,
364 return isOffsetInRange(UserOffset, TrialOffset,
365 U.getLongFormMaxDisp(), U.NegOk);
368 bool MipsConstantIslands::isOffsetInRange
369 (unsigned UserOffset, unsigned TrialOffset,
371 return isOffsetInRange(UserOffset, TrialOffset,
372 U.getMaxDisp(), U.NegOk);
374 /// print block size and offset information - debugging
375 void MipsConstantIslands::dumpBBs() {
377 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
378 const BasicBlockInfo &BBI = BBInfo[J];
379 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
380 << " kb=" << unsigned(BBI.KnownBits)
381 << " ua=" << unsigned(BBI.Unalign)
382 << " pa=" << unsigned(BBI.PostAlign)
383 << format(" size=%#x\n", BBInfo[J].Size);
387 /// createMipsLongBranchPass - Returns a pass that converts branches to long
389 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
390 return new MipsConstantIslands(tm);
393 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
394 // The intention is for this to be a mips16 only pass for now
397 MCP = mf.getConstantPool();
398 DEBUG(dbgs() << "constant island machine function " << "\n");
399 if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode() ||
400 !MipsSubtarget::useConstantIslands()) {
403 TII = (const MipsInstrInfo*)MF->getTarget().getInstrInfo();
404 MFI = MF->getInfo<MipsFunctionInfo>();
405 DEBUG(dbgs() << "constant island processing " << "\n");
407 // will need to make predermination if there is any constants we need to
408 // put in constant islands. TBD.
410 if (!PrescannedForConstants) prescanForConstants();
413 // This pass invalidates liveness information when it splits basic blocks.
414 MF->getRegInfo().invalidateLiveness();
416 // Renumber all of the machine basic blocks in the function, guaranteeing that
417 // the numbers agree with the position of the block in the function.
418 MF->RenumberBlocks();
420 bool MadeChange = false;
422 // Perform the initial placement of the constant pool entries. To start with,
423 // we put them all at the end of the function.
424 std::vector<MachineInstr*> CPEMIs;
426 doInitialPlacement(CPEMIs);
428 /// The next UID to take is the first unused one.
429 initPICLabelUId(CPEMIs.size());
431 // Do the initial scan of the function, building up information about the
432 // sizes of each block, the location of all the water, and finding all of the
433 // constant pool users.
434 initializeFunctionInfo(CPEMIs);
438 /// Remove dead constant pool entries.
439 MadeChange |= removeUnusedCPEntries();
441 // Iteratively place constant pool entries and fix up branches until there
443 unsigned NoCPIters = 0, NoBRIters = 0;
446 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
447 bool CPChange = false;
448 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
449 CPChange |= handleConstantPoolUser(i);
450 if (CPChange && ++NoCPIters > 30)
451 report_fatal_error("Constant Island pass failed to converge!");
454 // Clear NewWaterList now. If we split a block for branches, it should
455 // appear as "new water" for the next iteration of constant pool placement.
456 NewWaterList.clear();
458 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
459 bool BRChange = false;
461 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
462 BRChange |= fixupImmediateBr(ImmBranches[i]);
463 if (BRChange && ++NoBRIters > 30)
464 report_fatal_error("Branch Fix Up pass failed to converge!");
467 if (!CPChange && !BRChange)
472 DEBUG(dbgs() << '\n'; dumpBBs());
482 /// doInitialPlacement - Perform the initial placement of the constant pool
483 /// entries. To start with, we put them all at the end of the function.
485 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
486 // Create the basic block to hold the CPE's.
487 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
491 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
492 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
494 // Mark the basic block as required by the const-pool.
495 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
496 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
498 // The function needs to be as aligned as the basic blocks. The linker may
499 // move functions around based on their alignment.
500 MF->ensureAlignment(BB->getAlignment());
502 // Order the entries in BB by descending alignment. That ensures correct
503 // alignment of all entries as long as BB is sufficiently aligned. Keep
504 // track of the insertion point for each alignment. We are going to bucket
505 // sort the entries as they are created.
506 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
508 // Add all of the constants from the constant pool to the end block, use an
509 // identity mapping of CPI's to CPE's.
510 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
512 const DataLayout &TD = *MF->getTarget().getDataLayout();
513 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
514 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
515 assert(Size >= 4 && "Too small constant pool entry");
516 unsigned Align = CPs[i].getAlignment();
517 assert(isPowerOf2_32(Align) && "Invalid alignment");
518 // Verify that all constant pool entries are a multiple of their alignment.
519 // If not, we would have to pad them out so that instructions stay aligned.
520 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
522 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
523 unsigned LogAlign = Log2_32(Align);
524 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
526 MachineInstr *CPEMI =
527 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
528 .addImm(i).addConstantPoolIndex(i).addImm(Size);
530 CPEMIs.push_back(CPEMI);
532 // Ensure that future entries with higher alignment get inserted before
533 // CPEMI. This is bucket sort with iterators.
534 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
535 if (InsPoint[a] == InsAt)
537 // Add a new CPEntry, but no corresponding CPUser yet.
538 std::vector<CPEntry> CPEs;
539 CPEs.push_back(CPEntry(CPEMI, i));
540 CPEntries.push_back(CPEs);
542 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
543 << Size << ", align = " << Align <<'\n');
548 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
549 /// into the block immediately after it.
550 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
551 // Get the next machine basic block in the function.
552 MachineFunction::iterator MBBI = MBB;
553 // Can't fall off end of function.
554 if (llvm::next(MBBI) == MBB->getParent()->end())
557 MachineBasicBlock *NextBB = llvm::next(MBBI);
558 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
559 E = MBB->succ_end(); I != E; ++I)
566 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
567 /// look up the corresponding CPEntry.
568 MipsConstantIslands::CPEntry
569 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
570 const MachineInstr *CPEMI) {
571 std::vector<CPEntry> &CPEs = CPEntries[CPI];
572 // Number of entries per constpool index should be small, just do a
574 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
575 if (CPEs[i].CPEMI == CPEMI)
581 /// getCPELogAlign - Returns the required alignment of the constant pool entry
582 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
583 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
584 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
586 // Everything is 4-byte aligned unless AlignConstantIslands is set.
587 if (!AlignConstantIslands)
590 unsigned CPI = CPEMI->getOperand(1).getIndex();
591 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
592 unsigned Align = MCP->getConstants()[CPI].getAlignment();
593 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
594 return Log2_32(Align);
597 /// initializeFunctionInfo - Do the initial scan of the function, building up
598 /// information about the sizes of each block, the location of all the water,
599 /// and finding all of the constant pool users.
600 void MipsConstantIslands::
601 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
603 BBInfo.resize(MF->getNumBlockIDs());
605 // First thing, compute the size of all basic blocks, and see if the function
606 // has any inline assembly in it. If so, we have to be conservative about
607 // alignment assumptions, as we don't know for sure the size of any
608 // instructions in the inline assembly.
609 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
612 // The known bits of the entry block offset are determined by the function
614 BBInfo.front().KnownBits = MF->getAlignment();
616 // Compute block offsets.
617 adjustBBOffsetsAfter(MF->begin());
619 // Now go back through the instructions and build up our data structures.
620 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
622 MachineBasicBlock &MBB = *MBBI;
624 // If this block doesn't fall through into the next MBB, then this is
625 // 'water' that a constant pool island could be placed.
626 if (!BBHasFallthrough(&MBB))
627 WaterList.push_back(&MBB);
628 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
630 if (I->isDebugValue())
633 int Opc = I->getOpcode();
642 continue; // Ignore other JT branches
644 // Record this immediate branch.
645 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
646 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
651 if (Opc == Mips::CONSTPOOL_ENTRY)
655 // Scan the instructions for constant pool operands.
656 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
657 if (I->getOperand(op).isCPI()) {
659 // We found one. The addressing mode tells us the max displacement
660 // from the PC that this instruction permits.
662 // Basic size info comes from the TSFlags field.
666 unsigned LongFormBits = 0;
667 unsigned LongFormScale = 0;
668 unsigned LongFormOpcode = 0;
671 llvm_unreachable("Unknown addressing mode for CP reference!");
672 case Mips::LwRxPcTcp16:
675 LongFormOpcode = Mips::LwRxPcTcpX16;
677 case Mips::LwRxPcTcpX16:
682 // Remember that this is a user of a CP entry.
683 unsigned CPI = I->getOperand(op).getIndex();
684 MachineInstr *CPEMI = CPEMIs[CPI];
685 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
686 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
687 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
688 LongFormMaxOffs, LongFormOpcode));
690 // Increment corresponding CPEntry reference count.
691 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
692 assert(CPE && "Cannot find a corresponding CPEntry!");
695 // Instructions can only use one CP entry, don't bother scanning the
696 // rest of the operands.
706 /// computeBlockSize - Compute the size and some alignment information for MBB.
707 /// This function updates BBInfo directly.
708 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
709 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
714 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
716 BBI.Size += TII->GetInstSizeInBytes(I);
720 /// getOffsetOf - Return the current offset of the specified machine instruction
721 /// from the start of the function. This offset changes as stuff is moved
722 /// around inside the function.
723 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
724 MachineBasicBlock *MBB = MI->getParent();
726 // The offset is composed of two things: the sum of the sizes of all MBB's
727 // before this instruction's block, and the offset from the start of the block
729 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
731 // Sum instructions before MI in MBB.
732 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
733 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
734 Offset += TII->GetInstSizeInBytes(I);
739 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
741 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
742 const MachineBasicBlock *RHS) {
743 return LHS->getNumber() < RHS->getNumber();
746 /// updateForInsertedWaterBlock - When a block is newly inserted into the
747 /// machine function, it upsets all of the block numbers. Renumber the blocks
748 /// and update the arrays that parallel this numbering.
749 void MipsConstantIslands::updateForInsertedWaterBlock
750 (MachineBasicBlock *NewBB) {
751 // Renumber the MBB's to keep them consecutive.
752 NewBB->getParent()->RenumberBlocks(NewBB);
754 // Insert an entry into BBInfo to align it properly with the (newly
755 // renumbered) block numbers.
756 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
758 // Next, update WaterList. Specifically, we need to add NewMBB as having
759 // available water after it.
761 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
763 WaterList.insert(IP, NewBB);
766 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
767 return getOffsetOf(U.MI);
770 /// Split the basic block containing MI into two blocks, which are joined by
771 /// an unconditional branch. Update data structures and renumber blocks to
772 /// account for this change and returns the newly created block.
773 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
775 MachineBasicBlock *OrigBB = MI->getParent();
777 // Create a new MBB for the code after the OrigBB.
778 MachineBasicBlock *NewBB =
779 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
780 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
781 MF->insert(MBBI, NewBB);
783 // Splice the instructions starting with MI over to NewBB.
784 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
786 // Add an unconditional branch from OrigBB to NewBB.
787 // Note the new unconditional branch is not being recorded.
788 // There doesn't seem to be meaningful DebugInfo available; this doesn't
789 // correspond to anything in the source.
790 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::BimmX16)).addMBB(NewBB);
793 // Update the CFG. All succs of OrigBB are now succs of NewBB.
794 NewBB->transferSuccessors(OrigBB);
796 // OrigBB branches to NewBB.
797 OrigBB->addSuccessor(NewBB);
799 // Update internal data structures to account for the newly inserted MBB.
800 // This is almost the same as updateForInsertedWaterBlock, except that
801 // the Water goes after OrigBB, not NewBB.
802 MF->RenumberBlocks(NewBB);
804 // Insert an entry into BBInfo to align it properly with the (newly
805 // renumbered) block numbers.
806 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
808 // Next, update WaterList. Specifically, we need to add OrigMBB as having
809 // available water after it (but not if it's already there, which happens
810 // when splitting before a conditional branch that is followed by an
811 // unconditional branch - in that case we want to insert NewBB).
813 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
815 MachineBasicBlock* WaterBB = *IP;
816 if (WaterBB == OrigBB)
817 WaterList.insert(llvm::next(IP), NewBB);
819 WaterList.insert(IP, OrigBB);
820 NewWaterList.insert(OrigBB);
822 // Figure out how large the OrigBB is. As the first half of the original
823 // block, it cannot contain a tablejump. The size includes
824 // the new jump we added. (It should be possible to do this without
825 // recounting everything, but it's very confusing, and this is rarely
827 computeBlockSize(OrigBB);
829 // Figure out how large the NewMBB is. As the second half of the original
830 // block, it may contain a tablejump.
831 computeBlockSize(NewBB);
833 // All BBOffsets following these blocks must be modified.
834 adjustBBOffsetsAfter(OrigBB);
841 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
842 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
843 /// constant pool entry).
844 /// UserOffset is computed by getUserOffset above to include PC adjustments. If
845 /// the mod 4 alignment of UserOffset is not known, the uncertainty must be
846 /// subtracted from MaxDisp instead. CPUser::getMaxDisp() does that.
847 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
848 unsigned TrialOffset, unsigned MaxDisp,
850 if (UserOffset <= TrialOffset) {
851 // User before the Trial.
852 if (TrialOffset - UserOffset <= MaxDisp)
854 } else if (NegativeOK) {
855 if (UserOffset - TrialOffset <= MaxDisp)
861 /// isWaterInRange - Returns true if a CPE placed after the specified
862 /// Water (a basic block) will be in range for the specific MI.
864 /// Compute how much the function will grow by inserting a CPE after Water.
865 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
866 MachineBasicBlock* Water, CPUser &U,
868 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
869 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
870 unsigned NextBlockOffset, NextBlockAlignment;
871 MachineFunction::const_iterator NextBlock = Water;
872 if (++NextBlock == MF->end()) {
873 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
874 NextBlockAlignment = 0;
876 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
877 NextBlockAlignment = NextBlock->getAlignment();
879 unsigned Size = U.CPEMI->getOperand(2).getImm();
880 unsigned CPEEnd = CPEOffset + Size;
882 // The CPE may be able to hide in the alignment padding before the next
883 // block. It may also cause more padding to be required if it is more aligned
884 // that the next block.
885 if (CPEEnd > NextBlockOffset) {
886 Growth = CPEEnd - NextBlockOffset;
887 // Compute the padding that would go at the end of the CPE to align the next
889 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
891 // If the CPE is to be inserted before the instruction, that will raise
892 // the offset of the instruction. Also account for unknown alignment padding
893 // in blocks between CPE and the user.
894 if (CPEOffset < UserOffset)
895 UserOffset += Growth + UnknownPadding(MF->getAlignment(), CPELogAlign);
897 // CPE fits in existing padding.
900 return isOffsetInRange(UserOffset, CPEOffset, U);
903 /// isCPEntryInRange - Returns true if the distance between specific MI and
904 /// specific ConstPool entry instruction can fit in MI's displacement field.
905 bool MipsConstantIslands::isCPEntryInRange
906 (MachineInstr *MI, unsigned UserOffset,
907 MachineInstr *CPEMI, unsigned MaxDisp,
908 bool NegOk, bool DoDump) {
909 unsigned CPEOffset = getOffsetOf(CPEMI);
913 unsigned Block = MI->getParent()->getNumber();
914 const BasicBlockInfo &BBI = BBInfo[Block];
915 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
916 << " max delta=" << MaxDisp
917 << format(" insn address=%#x", UserOffset)
918 << " in BB#" << Block << ": "
919 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
920 << format("CPE address=%#x offset=%+d: ", CPEOffset,
921 int(CPEOffset-UserOffset));
925 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
929 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
930 /// unconditionally branches to its only successor.
931 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
932 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
934 MachineBasicBlock *Succ = *MBB->succ_begin();
935 MachineBasicBlock *Pred = *MBB->pred_begin();
936 MachineInstr *PredMI = &Pred->back();
937 if (PredMI->getOpcode() == Mips::BimmX16)
938 return PredMI->getOperand(0).getMBB() == Succ;
943 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
944 unsigned BBNum = BB->getNumber();
945 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
946 // Get the offset and known bits at the end of the layout predecessor.
947 // Include the alignment of the current block.
948 unsigned Offset = BBInfo[i - 1].postOffset();
949 BBInfo[i].Offset = Offset;
953 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
954 /// and instruction CPEMI, and decrement its refcount. If the refcount
955 /// becomes 0 remove the entry and instruction. Returns true if we removed
956 /// the entry, false if we didn't.
958 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
959 MachineInstr *CPEMI) {
960 // Find the old entry. Eliminate it if it is no longer used.
961 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
962 assert(CPE && "Unexpected!");
963 if (--CPE->RefCount == 0) {
964 removeDeadCPEMI(CPEMI);
972 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
973 /// if not, see if an in-range clone of the CPE is in range, and if so,
974 /// change the data structures so the user references the clone. Returns:
975 /// 0 = no existing entry found
976 /// 1 = entry found, and there were no code insertions or deletions
977 /// 2 = entry found, and there were code insertions or deletions
978 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
980 MachineInstr *UserMI = U.MI;
981 MachineInstr *CPEMI = U.CPEMI;
983 // Check to see if the CPE is already in-range.
984 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
986 DEBUG(dbgs() << "In range\n");
990 // No. Look for previously created clones of the CPE that are in range.
991 unsigned CPI = CPEMI->getOperand(1).getIndex();
992 std::vector<CPEntry> &CPEs = CPEntries[CPI];
993 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
994 // We already tried this one
995 if (CPEs[i].CPEMI == CPEMI)
997 // Removing CPEs can leave empty entries, skip
998 if (CPEs[i].CPEMI == NULL)
1000 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1002 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1003 << CPEs[i].CPI << "\n");
1004 // Point the CPUser node to the replacement
1005 U.CPEMI = CPEs[i].CPEMI;
1006 // Change the CPI in the instruction operand to refer to the clone.
1007 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1008 if (UserMI->getOperand(j).isCPI()) {
1009 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1012 // Adjust the refcount of the clone...
1014 // ...and the original. If we didn't remove the old entry, none of the
1015 // addresses changed, so we don't need another pass.
1016 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1022 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1023 /// This version checks if the longer form of the instruction can be used to
1024 /// to satisfy things.
1025 /// if not, see if an in-range clone of the CPE is in range, and if so,
1026 /// change the data structures so the user references the clone. Returns:
1027 /// 0 = no existing entry found
1028 /// 1 = entry found, and there were no code insertions or deletions
1029 /// 2 = entry found, and there were code insertions or deletions
1030 int MipsConstantIslands::findLongFormInRangeCPEntry
1031 (CPUser& U, unsigned UserOffset)
1033 MachineInstr *UserMI = U.MI;
1034 MachineInstr *CPEMI = U.CPEMI;
1036 // Check to see if the CPE is already in-range.
1037 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1038 U.getLongFormMaxDisp(), U.NegOk,
1040 DEBUG(dbgs() << "In range\n");
1041 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1042 return 2; // instruction is longer length now
1045 // No. Look for previously created clones of the CPE that are in range.
1046 unsigned CPI = CPEMI->getOperand(1).getIndex();
1047 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1048 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1049 // We already tried this one
1050 if (CPEs[i].CPEMI == CPEMI)
1052 // Removing CPEs can leave empty entries, skip
1053 if (CPEs[i].CPEMI == NULL)
1055 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1056 U.getLongFormMaxDisp(), U.NegOk)) {
1057 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1058 << CPEs[i].CPI << "\n");
1059 // Point the CPUser node to the replacement
1060 U.CPEMI = CPEs[i].CPEMI;
1061 // Change the CPI in the instruction operand to refer to the clone.
1062 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1063 if (UserMI->getOperand(j).isCPI()) {
1064 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1067 // Adjust the refcount of the clone...
1069 // ...and the original. If we didn't remove the old entry, none of the
1070 // addresses changed, so we don't need another pass.
1071 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1077 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1078 /// the specific unconditional branch instruction.
1079 static inline unsigned getUnconditionalBrDisp(int Opc) {
1082 return ((1<<16)-1)*2;
1086 return ((1<<16)-1)*2;
1089 /// findAvailableWater - Look for an existing entry in the WaterList in which
1090 /// we can place the CPE referenced from U so it's within range of U's MI.
1091 /// Returns true if found, false if not. If it returns true, WaterIter
1092 /// is set to the WaterList entry.
1093 /// To ensure that this pass
1094 /// terminates, the CPE location for a particular CPUser is only allowed to
1095 /// move to a lower address, so search backward from the end of the list and
1096 /// prefer the first water that is in range.
1097 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1098 water_iterator &WaterIter) {
1099 if (WaterList.empty())
1102 unsigned BestGrowth = ~0u;
1103 for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();;
1105 MachineBasicBlock* WaterBB = *IP;
1106 // Check if water is in range and is either at a lower address than the
1107 // current "high water mark" or a new water block that was created since
1108 // the previous iteration by inserting an unconditional branch. In the
1109 // latter case, we want to allow resetting the high water mark back to
1110 // this new water since we haven't seen it before. Inserting branches
1111 // should be relatively uncommon and when it does happen, we want to be
1112 // sure to take advantage of it for all the CPEs near that block, so that
1113 // we don't insert more branches than necessary.
1115 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1116 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1117 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1118 // This is the least amount of required padding seen so far.
1119 BestGrowth = Growth;
1121 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1122 << " Growth=" << Growth << '\n');
1124 // Keep looking unless it is perfect.
1125 if (BestGrowth == 0)
1131 return BestGrowth != ~0u;
1134 /// createNewWater - No existing WaterList entry will work for
1135 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1136 /// block is used if in range, and the conditional branch munged so control
1137 /// flow is correct. Otherwise the block is split to create a hole with an
1138 /// unconditional branch around it. In either case NewMBB is set to a
1139 /// block following which the new island can be inserted (the WaterList
1140 /// is not adjusted).
1141 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1142 unsigned UserOffset,
1143 MachineBasicBlock *&NewMBB) {
1144 CPUser &U = CPUsers[CPUserIndex];
1145 MachineInstr *UserMI = U.MI;
1146 MachineInstr *CPEMI = U.CPEMI;
1147 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1148 MachineBasicBlock *UserMBB = UserMI->getParent();
1149 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1151 // If the block does not end in an unconditional branch already, and if the
1152 // end of the block is within range, make new water there.
1153 if (BBHasFallthrough(UserMBB)) {
1154 // Size of branch to insert.
1156 // Compute the offset where the CPE will begin.
1157 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1159 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1160 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1161 << format(", expected CPE offset %#x\n", CPEOffset));
1162 NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
1163 // Add an unconditional branch from UserMBB to fallthrough block. Record
1164 // it for branch lengthening; this new branch will not get out of range,
1165 // but if the preceding conditional branch is out of range, the targets
1166 // will be exchanged, and the altered branch may be out of range, so the
1167 // machinery has to know about it.
1168 int UncondBr = Mips::BimmX16;
1169 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1170 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1171 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1172 MaxDisp, false, UncondBr));
1173 BBInfo[UserMBB->getNumber()].Size += Delta;
1174 adjustBBOffsetsAfter(UserMBB);
1179 // What a big block. Find a place within the block to split it.
1181 // Try to split the block so it's fully aligned. Compute the latest split
1182 // point where we can add a 4-byte branch instruction, and then align to
1183 // LogAlign which is the largest possible alignment in the function.
1184 unsigned LogAlign = MF->getAlignment();
1185 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1186 unsigned KnownBits = UserBBI.internalKnownBits();
1187 unsigned UPad = UnknownPadding(LogAlign, KnownBits);
1188 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp() - UPad;
1189 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1192 // The 4 in the following is for the unconditional branch we'll be inserting
1193 // Alignment of the island is handled
1194 // inside isOffsetInRange.
1195 BaseInsertOffset -= 4;
1197 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1198 << " la=" << LogAlign
1199 << " kb=" << KnownBits
1200 << " up=" << UPad << '\n');
1202 // This could point off the end of the block if we've already got constant
1203 // pool entries following this block; only the last one is in the water list.
1204 // Back past any possible branches (allow for a conditional and a maximally
1205 // long unconditional).
1206 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1207 BaseInsertOffset = UserBBI.postOffset() - UPad - 8;
1208 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1210 unsigned EndInsertOffset = BaseInsertOffset + 4 + UPad +
1211 CPEMI->getOperand(2).getImm();
1212 MachineBasicBlock::iterator MI = UserMI;
1214 unsigned CPUIndex = CPUserIndex+1;
1215 unsigned NumCPUsers = CPUsers.size();
1216 //MachineInstr *LastIT = 0;
1217 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1218 Offset < BaseInsertOffset;
1219 Offset += TII->GetInstSizeInBytes(MI),
1220 MI = llvm::next(MI)) {
1221 assert(MI != UserMBB->end() && "Fell off end of block");
1222 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1223 CPUser &U = CPUsers[CPUIndex];
1224 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1225 // Shift intertion point by one unit of alignment so it is within reach.
1226 BaseInsertOffset -= 1u << LogAlign;
1227 EndInsertOffset -= 1u << LogAlign;
1229 // This is overly conservative, as we don't account for CPEMIs being
1230 // reused within the block, but it doesn't matter much. Also assume CPEs
1231 // are added in order with alignment padding. We may eventually be able
1232 // to pack the aligned CPEs better.
1233 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1239 NewMBB = splitBlockBeforeInstr(MI);
1242 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1243 /// is out-of-range. If so, pick up the constant pool value and move it some
1244 /// place in-range. Return true if we changed any addresses (thus must run
1245 /// another pass of branch lengthening), false otherwise.
1246 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1247 CPUser &U = CPUsers[CPUserIndex];
1248 MachineInstr *UserMI = U.MI;
1249 MachineInstr *CPEMI = U.CPEMI;
1250 unsigned CPI = CPEMI->getOperand(1).getIndex();
1251 unsigned Size = CPEMI->getOperand(2).getImm();
1252 // Compute this only once, it's expensive.
1253 unsigned UserOffset = getUserOffset(U);
1255 // See if the current entry is within range, or there is a clone of it
1257 int result = findInRangeCPEntry(U, UserOffset);
1258 if (result==1) return false;
1259 else if (result==2) return true;
1262 // Look for water where we can place this CPE.
1263 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1264 MachineBasicBlock *NewMBB;
1266 if (findAvailableWater(U, UserOffset, IP)) {
1267 DEBUG(dbgs() << "Found water in range\n");
1268 MachineBasicBlock *WaterBB = *IP;
1270 // If the original WaterList entry was "new water" on this iteration,
1271 // propagate that to the new island. This is just keeping NewWaterList
1272 // updated to match the WaterList, which will be updated below.
1273 if (NewWaterList.erase(WaterBB))
1274 NewWaterList.insert(NewIsland);
1276 // The new CPE goes before the following block (NewMBB).
1277 NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
1281 // we first see if a longer form of the instrucion could have reached
1282 // the constant. in that case we won't bother to split
1284 result = findLongFormInRangeCPEntry(U, UserOffset);
1286 DEBUG(dbgs() << "No water found\n");
1287 createNewWater(CPUserIndex, UserOffset, NewMBB);
1289 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1290 // called while handling branches so that the water will be seen on the
1291 // next iteration for constant pools, but in this context, we don't want
1292 // it. Check for this so it will be removed from the WaterList.
1293 // Also remove any entry from NewWaterList.
1294 MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
1295 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1296 if (IP != WaterList.end())
1297 NewWaterList.erase(WaterBB);
1299 // We are adding new water. Update NewWaterList.
1300 NewWaterList.insert(NewIsland);
1303 // Remove the original WaterList entry; we want subsequent insertions in
1304 // this vicinity to go after the one we're about to insert. This
1305 // considerably reduces the number of times we have to move the same CPE
1306 // more than once and is also important to ensure the algorithm terminates.
1307 if (IP != WaterList.end())
1308 WaterList.erase(IP);
1310 // Okay, we know we can put an island before NewMBB now, do it!
1311 MF->insert(NewMBB, NewIsland);
1313 // Update internal data structures to account for the newly inserted MBB.
1314 updateForInsertedWaterBlock(NewIsland);
1316 // Decrement the old entry, and remove it if refcount becomes 0.
1317 decrementCPEReferenceCount(CPI, CPEMI);
1319 // Now that we have an island to add the CPE to, clone the original CPE and
1320 // add it to the island.
1321 U.HighWaterMark = NewIsland;
1322 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1323 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1324 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1327 // Mark the basic block as aligned as required by the const-pool entry.
1328 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1330 // Increase the size of the island block to account for the new entry.
1331 BBInfo[NewIsland->getNumber()].Size += Size;
1332 adjustBBOffsetsAfter(llvm::prior(MachineFunction::iterator(NewIsland)));
1334 // No existing clone of this CPE is within range.
1335 // We will be generating a new clone. Get a UID for it.
1336 unsigned ID = createPICLabelUId();
1338 // Finally, change the CPI in the instruction operand to be ID.
1339 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1340 if (UserMI->getOperand(i).isCPI()) {
1341 UserMI->getOperand(i).setIndex(ID);
1345 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1346 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1351 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1352 /// sizes and offsets of impacted basic blocks.
1353 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1354 MachineBasicBlock *CPEBB = CPEMI->getParent();
1355 unsigned Size = CPEMI->getOperand(2).getImm();
1356 CPEMI->eraseFromParent();
1357 BBInfo[CPEBB->getNumber()].Size -= Size;
1358 // All succeeding offsets have the current size value added in, fix this.
1359 if (CPEBB->empty()) {
1360 BBInfo[CPEBB->getNumber()].Size = 0;
1362 // This block no longer needs to be aligned.
1363 CPEBB->setAlignment(0);
1365 // Entries are sorted by descending alignment, so realign from the front.
1366 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1368 adjustBBOffsetsAfter(CPEBB);
1369 // An island has only one predecessor BB and one successor BB. Check if
1370 // this BB's predecessor jumps directly to this BB's successor. This
1371 // shouldn't happen currently.
1372 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1373 // FIXME: remove the empty blocks after all the work is done?
1376 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1378 bool MipsConstantIslands::removeUnusedCPEntries() {
1379 unsigned MadeChange = false;
1380 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1381 std::vector<CPEntry> &CPEs = CPEntries[i];
1382 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1383 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1384 removeDeadCPEMI(CPEs[j].CPEMI);
1385 CPEs[j].CPEMI = NULL;
1393 /// isBBInRange - Returns true if the distance between specific MI and
1394 /// specific BB can fit in MI's displacement field.
1395 bool MipsConstantIslands::isBBInRange
1396 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1400 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1401 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1403 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1404 << " from BB#" << MI->getParent()->getNumber()
1405 << " max delta=" << MaxDisp
1406 << " from " << getOffsetOf(MI) << " to " << DestOffset
1407 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1409 if (BrOffset <= DestOffset) {
1410 // Branch before the Dest.
1411 if (DestOffset-BrOffset <= MaxDisp)
1414 if (BrOffset-DestOffset <= MaxDisp)
1420 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1421 /// away to fit in its displacement field.
1422 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1423 MachineInstr *MI = Br.MI;
1424 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1426 // Check to see if the DestBB is already in-range.
1427 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1431 return fixupUnconditionalBr(Br);
1432 return fixupConditionalBr(Br);
1435 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1436 /// too far away to fit in its displacement field. If the LR register has been
1437 /// spilled in the epilogue, then we can use BL to implement a far jump.
1438 /// Otherwise, add an intermediate branch instruction to a branch.
1440 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1441 MachineInstr *MI = Br.MI;
1442 MachineBasicBlock *MBB = MI->getParent();
1443 // Use BL to implement far jump.
1444 Br.MaxDisp = ((1 << 16)-1) * 2;
1445 MI->setDesc(TII->get(Mips::BimmX16));
1446 BBInfo[MBB->getNumber()].Size += 2;
1447 adjustBBOffsetsAfter(MBB);
1451 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1456 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1457 /// far away to fit in its displacement field. It is converted to an inverse
1458 /// conditional branch + an unconditional branch to the destination.
1460 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1461 MachineInstr *MI = Br.MI;
1462 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1464 // Add an unconditional branch to the destination and invert the branch
1465 // condition to jump over it:
1471 unsigned CCReg = 0; // FIXME
1472 unsigned CC=0; //FIXME
1474 // If the branch is at the end of its MBB and that has a fall-through block,
1475 // direct the updated conditional branch to the fall-through block. Otherwise,
1476 // split the MBB before the next instruction.
1477 MachineBasicBlock *MBB = MI->getParent();
1478 MachineInstr *BMI = &MBB->back();
1479 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1483 if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
1484 BMI->getOpcode() == Br.UncondBr) {
1485 // Last MI in the BB is an unconditional branch. Can we simply invert the
1486 // condition and swap destinations:
1492 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
1493 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1494 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1496 BMI->getOperand(0).setMBB(DestBB);
1497 MI->getOperand(0).setMBB(NewDest);
1504 splitBlockBeforeInstr(MI);
1505 // No need for the branch to the next block. We're adding an unconditional
1506 // branch to the destination.
1507 int delta = TII->GetInstSizeInBytes(&MBB->back());
1508 BBInfo[MBB->getNumber()].Size -= delta;
1509 MBB->back().eraseFromParent();
1510 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1512 MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
1514 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1515 << " also invert condition and change dest. to BB#"
1516 << NextBB->getNumber() << "\n");
1518 // Insert a new conditional branch and a new unconditional branch.
1519 // Also update the ImmBranch as well as adding a new entry for the new branch.
1520 BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode()))
1521 .addMBB(NextBB).addImm(CC).addReg(CCReg);
1522 Br.MI = &MBB->back();
1523 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1524 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1525 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1526 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1527 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1529 // Remove the old conditional branch. It may or may not still be in MBB.
1530 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1531 MI->eraseFromParent();
1532 adjustBBOffsetsAfter(MBB);
1537 void MipsConstantIslands::prescanForConstants() {
1540 PrescannedForConstants = true;
1541 for (MachineFunction::iterator B =
1542 MF->begin(), E = MF->end(); B != E; ++B) {
1543 for (MachineBasicBlock::instr_iterator I =
1544 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1545 switch(I->getDesc().getOpcode()) {
1546 case Mips::LwConstant32: {
1547 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1548 J = I->getNumOperands();
1549 DEBUG(dbgs() << "num operands " << J << "\n");
1550 MachineOperand& Literal = I->getOperand(1);
1551 if (Literal.isImm()) {
1552 int64_t V = Literal.getImm();
1553 DEBUG(dbgs() << "literal " << V << "\n");
1555 Type::getInt32Ty(MF->getFunction()->getContext());
1556 const Constant *C = ConstantInt::get(Int32Ty, V);
1557 unsigned index = MCP->getConstantPoolIndex(C, 4);
1558 I->getOperand(2).ChangeToImmediate(index);
1559 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1560 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1561 I->RemoveOperand(1);
1562 I->RemoveOperand(1);
1563 I->addOperand(MachineOperand::CreateCPI(index, 0));
1564 I->addOperand(MachineOperand::CreateImm(4));