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"),
73 typedef MachineBasicBlock::iterator Iter;
74 typedef MachineBasicBlock::reverse_iterator ReverseIter;
76 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
77 /// requires constant pool entries to be scattered among the instructions
78 /// inside a function. To do this, it completely ignores the normal LLVM
79 /// constant pool; instead, it places constants wherever it feels like with
80 /// special instructions.
82 /// The terminology used in this pass includes:
83 /// Islands - Clumps of constants placed in the function.
84 /// Water - Potential places where an island could be formed.
85 /// CPE - A constant pool entry that has been placed somewhere, which
86 /// tracks a list of users.
88 class MipsConstantIslands : public MachineFunctionPass {
90 /// BasicBlockInfo - Information about the offset and size of a single
92 struct BasicBlockInfo {
93 /// Offset - Distance from the beginning of the function to the beginning
94 /// of this basic block.
96 /// Offsets are computed assuming worst case padding before an aligned
97 /// block. This means that subtracting basic block offsets always gives a
98 /// conservative estimate of the real distance which may be smaller.
100 /// Because worst case padding is used, the computed offset of an aligned
101 /// block may not actually be aligned.
104 /// Size - Size of the basic block in bytes. If the block contains
105 /// inline assembly, this is a worst case estimate.
107 /// The size does not include any alignment padding whether from the
108 /// beginning of the block, or from an aligned jump table at the end.
111 // FIXME: ignore LogAlign for this patch
113 unsigned postOffset(unsigned LogAlign = 0) const {
114 unsigned PO = Offset + Size;
118 BasicBlockInfo() : Offset(0), Size(0) {}
122 std::vector<BasicBlockInfo> BBInfo;
124 /// WaterList - A sorted list of basic blocks where islands could be placed
125 /// (i.e. blocks that don't fall through to the following block, due
126 /// to a return, unreachable, or unconditional branch).
127 std::vector<MachineBasicBlock*> WaterList;
129 /// NewWaterList - The subset of WaterList that was created since the
130 /// previous iteration by inserting unconditional branches.
131 SmallSet<MachineBasicBlock*, 4> NewWaterList;
133 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
135 /// CPUser - One user of a constant pool, keeping the machine instruction
136 /// pointer, the constant pool being referenced, and the max displacement
137 /// allowed from the instruction to the CP. The HighWaterMark records the
138 /// highest basic block where a new CPEntry can be placed. To ensure this
139 /// pass terminates, the CP entries are initially placed at the end of the
140 /// function and then move monotonically to lower addresses. The
141 /// exception to this rule is when the current CP entry for a particular
142 /// CPUser is out of range, but there is another CP entry for the same
143 /// constant value in range. We want to use the existing in-range CP
144 /// entry, but if it later moves out of range, the search for new water
145 /// should resume where it left off. The HighWaterMark is used to record
150 MachineBasicBlock *HighWaterMark;
153 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
154 // with different displacements
155 unsigned LongFormOpcode;
158 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
160 unsigned longformmaxdisp, unsigned longformopcode)
161 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
162 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
164 HighWaterMark = CPEMI->getParent();
166 /// getMaxDisp - Returns the maximum displacement supported by MI.
167 unsigned getMaxDisp() const {
168 unsigned xMaxDisp = ConstantIslandsSmallOffset?
169 ConstantIslandsSmallOffset: MaxDisp;
172 unsigned getLongFormMaxDisp() const {
173 return LongFormMaxDisp;
175 unsigned getLongFormOpcode() const {
176 return LongFormOpcode;
180 /// CPUsers - Keep track of all of the machine instructions that use various
181 /// constant pools and their max displacement.
182 std::vector<CPUser> CPUsers;
184 /// CPEntry - One per constant pool entry, keeping the machine instruction
185 /// pointer, the constpool index, and the number of CPUser's which
186 /// reference this entry.
191 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
192 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
195 /// CPEntries - Keep track of all of the constant pool entry machine
196 /// instructions. For each original constpool index (i.e. those that
197 /// existed upon entry to this pass), it keeps a vector of entries.
198 /// Original elements are cloned as we go along; the clones are
199 /// put in the vector of the original element, but have distinct CPIs.
200 std::vector<std::vector<CPEntry> > CPEntries;
202 /// ImmBranch - One per immediate branch, keeping the machine instruction
203 /// pointer, conditional or unconditional, the max displacement,
204 /// and (if isCond is true) the corresponding unconditional branch
208 unsigned MaxDisp : 31;
211 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
212 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
215 /// ImmBranches - Keep track of all the immediate branch instructions.
217 std::vector<ImmBranch> ImmBranches;
219 /// HasFarJump - True if any far jump instruction has been emitted during
220 /// the branch fix up pass.
223 const TargetMachine &TM;
226 const MipsSubtarget *STI;
227 const MipsInstrInfo *TII;
228 MipsFunctionInfo *MFI;
230 MachineConstantPool *MCP;
232 unsigned PICLabelUId;
233 bool PrescannedForConstants;
235 void initPICLabelUId(unsigned UId) {
240 unsigned createPICLabelUId() {
241 return PICLabelUId++;
246 MipsConstantIslands(TargetMachine &tm)
247 : MachineFunctionPass(ID), TM(tm),
248 IsPIC(TM.getRelocationModel() == Reloc::PIC_),
249 ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
250 STI(&TM.getSubtarget<MipsSubtarget>()), MF(0), MCP(0),
251 PrescannedForConstants(false){}
253 virtual const char *getPassName() const {
254 return "Mips Constant Islands";
257 bool runOnMachineFunction(MachineFunction &F);
259 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
260 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
261 unsigned getCPELogAlign(const MachineInstr *CPEMI);
262 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
263 unsigned getOffsetOf(MachineInstr *MI) const;
264 unsigned getUserOffset(CPUser&) const;
268 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
269 unsigned Disp, bool NegativeOK);
270 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
273 bool isLongFormOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
276 void computeBlockSize(MachineBasicBlock *MBB);
277 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
278 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
279 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
280 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
281 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
282 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
283 bool findAvailableWater(CPUser&U, unsigned UserOffset,
284 water_iterator &WaterIter);
285 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
286 MachineBasicBlock *&NewMBB);
287 bool handleConstantPoolUser(unsigned CPUserIndex);
288 void removeDeadCPEMI(MachineInstr *CPEMI);
289 bool removeUnusedCPEntries();
290 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
291 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
292 bool DoDump = false);
293 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
294 CPUser &U, unsigned &Growth);
295 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
296 bool fixupImmediateBr(ImmBranch &Br);
297 bool fixupConditionalBr(ImmBranch &Br);
298 bool fixupUnconditionalBr(ImmBranch &Br);
300 void prescanForConstants();
306 char MipsConstantIslands::ID = 0;
307 } // end of anonymous namespace
310 bool MipsConstantIslands::isLongFormOffsetInRange
311 (unsigned UserOffset, unsigned TrialOffset,
313 return isOffsetInRange(UserOffset, TrialOffset,
314 U.getLongFormMaxDisp(), U.NegOk);
317 bool MipsConstantIslands::isOffsetInRange
318 (unsigned UserOffset, unsigned TrialOffset,
320 return isOffsetInRange(UserOffset, TrialOffset,
321 U.getMaxDisp(), U.NegOk);
323 /// print block size and offset information - debugging
324 void MipsConstantIslands::dumpBBs() {
326 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
327 const BasicBlockInfo &BBI = BBInfo[J];
328 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
329 << format(" size=%#x\n", BBInfo[J].Size);
333 /// createMipsLongBranchPass - Returns a pass that converts branches to long
335 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
336 return new MipsConstantIslands(tm);
339 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
340 // The intention is for this to be a mips16 only pass for now
343 MCP = mf.getConstantPool();
344 DEBUG(dbgs() << "constant island machine function " << "\n");
345 if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode() ||
346 !MipsSubtarget::useConstantIslands()) {
349 TII = (const MipsInstrInfo*)MF->getTarget().getInstrInfo();
350 MFI = MF->getInfo<MipsFunctionInfo>();
351 DEBUG(dbgs() << "constant island processing " << "\n");
353 // will need to make predermination if there is any constants we need to
354 // put in constant islands. TBD.
356 if (!PrescannedForConstants) prescanForConstants();
359 // This pass invalidates liveness information when it splits basic blocks.
360 MF->getRegInfo().invalidateLiveness();
362 // Renumber all of the machine basic blocks in the function, guaranteeing that
363 // the numbers agree with the position of the block in the function.
364 MF->RenumberBlocks();
366 bool MadeChange = false;
368 // Perform the initial placement of the constant pool entries. To start with,
369 // we put them all at the end of the function.
370 std::vector<MachineInstr*> CPEMIs;
372 doInitialPlacement(CPEMIs);
374 /// The next UID to take is the first unused one.
375 initPICLabelUId(CPEMIs.size());
377 // Do the initial scan of the function, building up information about the
378 // sizes of each block, the location of all the water, and finding all of the
379 // constant pool users.
380 initializeFunctionInfo(CPEMIs);
384 /// Remove dead constant pool entries.
385 MadeChange |= removeUnusedCPEntries();
387 // Iteratively place constant pool entries and fix up branches until there
389 unsigned NoCPIters = 0, NoBRIters = 0;
392 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
393 bool CPChange = false;
394 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
395 CPChange |= handleConstantPoolUser(i);
396 if (CPChange && ++NoCPIters > 30)
397 report_fatal_error("Constant Island pass failed to converge!");
400 // Clear NewWaterList now. If we split a block for branches, it should
401 // appear as "new water" for the next iteration of constant pool placement.
402 NewWaterList.clear();
404 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
405 bool BRChange = false;
407 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
408 BRChange |= fixupImmediateBr(ImmBranches[i]);
409 if (BRChange && ++NoBRIters > 30)
410 report_fatal_error("Branch Fix Up pass failed to converge!");
413 if (!CPChange && !BRChange)
418 DEBUG(dbgs() << '\n'; dumpBBs());
428 /// doInitialPlacement - Perform the initial placement of the constant pool
429 /// entries. To start with, we put them all at the end of the function.
431 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
432 // Create the basic block to hold the CPE's.
433 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
437 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
438 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
440 // Mark the basic block as required by the const-pool.
441 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
442 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
444 // The function needs to be as aligned as the basic blocks. The linker may
445 // move functions around based on their alignment.
446 MF->ensureAlignment(BB->getAlignment());
448 // Order the entries in BB by descending alignment. That ensures correct
449 // alignment of all entries as long as BB is sufficiently aligned. Keep
450 // track of the insertion point for each alignment. We are going to bucket
451 // sort the entries as they are created.
452 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
454 // Add all of the constants from the constant pool to the end block, use an
455 // identity mapping of CPI's to CPE's.
456 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
458 const DataLayout &TD = *MF->getTarget().getDataLayout();
459 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
460 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
461 assert(Size >= 4 && "Too small constant pool entry");
462 unsigned Align = CPs[i].getAlignment();
463 assert(isPowerOf2_32(Align) && "Invalid alignment");
464 // Verify that all constant pool entries are a multiple of their alignment.
465 // If not, we would have to pad them out so that instructions stay aligned.
466 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
468 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
469 unsigned LogAlign = Log2_32(Align);
470 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
472 MachineInstr *CPEMI =
473 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
474 .addImm(i).addConstantPoolIndex(i).addImm(Size);
476 CPEMIs.push_back(CPEMI);
478 // Ensure that future entries with higher alignment get inserted before
479 // CPEMI. This is bucket sort with iterators.
480 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
481 if (InsPoint[a] == InsAt)
483 // Add a new CPEntry, but no corresponding CPUser yet.
484 std::vector<CPEntry> CPEs;
485 CPEs.push_back(CPEntry(CPEMI, i));
486 CPEntries.push_back(CPEs);
488 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
489 << Size << ", align = " << Align <<'\n');
494 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
495 /// into the block immediately after it.
496 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
497 // Get the next machine basic block in the function.
498 MachineFunction::iterator MBBI = MBB;
499 // Can't fall off end of function.
500 if (llvm::next(MBBI) == MBB->getParent()->end())
503 MachineBasicBlock *NextBB = llvm::next(MBBI);
504 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
505 E = MBB->succ_end(); I != E; ++I)
512 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
513 /// look up the corresponding CPEntry.
514 MipsConstantIslands::CPEntry
515 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
516 const MachineInstr *CPEMI) {
517 std::vector<CPEntry> &CPEs = CPEntries[CPI];
518 // Number of entries per constpool index should be small, just do a
520 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
521 if (CPEs[i].CPEMI == CPEMI)
527 /// getCPELogAlign - Returns the required alignment of the constant pool entry
528 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
529 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
530 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
532 // Everything is 4-byte aligned unless AlignConstantIslands is set.
533 if (!AlignConstantIslands)
536 unsigned CPI = CPEMI->getOperand(1).getIndex();
537 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
538 unsigned Align = MCP->getConstants()[CPI].getAlignment();
539 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
540 return Log2_32(Align);
543 /// initializeFunctionInfo - Do the initial scan of the function, building up
544 /// information about the sizes of each block, the location of all the water,
545 /// and finding all of the constant pool users.
546 void MipsConstantIslands::
547 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
549 BBInfo.resize(MF->getNumBlockIDs());
551 // First thing, compute the size of all basic blocks, and see if the function
552 // has any inline assembly in it. If so, we have to be conservative about
553 // alignment assumptions, as we don't know for sure the size of any
554 // instructions in the inline assembly.
555 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
559 // Compute block offsets.
560 adjustBBOffsetsAfter(MF->begin());
562 // Now go back through the instructions and build up our data structures.
563 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
565 MachineBasicBlock &MBB = *MBBI;
567 // If this block doesn't fall through into the next MBB, then this is
568 // 'water' that a constant pool island could be placed.
569 if (!BBHasFallthrough(&MBB))
570 WaterList.push_back(&MBB);
571 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
573 if (I->isDebugValue())
576 int Opc = I->getOpcode();
585 continue; // Ignore other JT branches
587 // Record this immediate branch.
588 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
589 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
594 if (Opc == Mips::CONSTPOOL_ENTRY)
598 // Scan the instructions for constant pool operands.
599 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
600 if (I->getOperand(op).isCPI()) {
602 // We found one. The addressing mode tells us the max displacement
603 // from the PC that this instruction permits.
605 // Basic size info comes from the TSFlags field.
609 unsigned LongFormBits = 0;
610 unsigned LongFormScale = 0;
611 unsigned LongFormOpcode = 0;
614 llvm_unreachable("Unknown addressing mode for CP reference!");
615 case Mips::LwRxPcTcp16:
618 LongFormOpcode = Mips::LwRxPcTcpX16;
620 case Mips::LwRxPcTcpX16:
625 // Remember that this is a user of a CP entry.
626 unsigned CPI = I->getOperand(op).getIndex();
627 MachineInstr *CPEMI = CPEMIs[CPI];
628 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
629 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
630 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
631 LongFormMaxOffs, LongFormOpcode));
633 // Increment corresponding CPEntry reference count.
634 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
635 assert(CPE && "Cannot find a corresponding CPEntry!");
638 // Instructions can only use one CP entry, don't bother scanning the
639 // rest of the operands.
649 /// computeBlockSize - Compute the size and some alignment information for MBB.
650 /// This function updates BBInfo directly.
651 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
652 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
655 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
657 BBI.Size += TII->GetInstSizeInBytes(I);
661 /// getOffsetOf - Return the current offset of the specified machine instruction
662 /// from the start of the function. This offset changes as stuff is moved
663 /// around inside the function.
664 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
665 MachineBasicBlock *MBB = MI->getParent();
667 // The offset is composed of two things: the sum of the sizes of all MBB's
668 // before this instruction's block, and the offset from the start of the block
670 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
672 // Sum instructions before MI in MBB.
673 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
674 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
675 Offset += TII->GetInstSizeInBytes(I);
680 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
682 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
683 const MachineBasicBlock *RHS) {
684 return LHS->getNumber() < RHS->getNumber();
687 /// updateForInsertedWaterBlock - When a block is newly inserted into the
688 /// machine function, it upsets all of the block numbers. Renumber the blocks
689 /// and update the arrays that parallel this numbering.
690 void MipsConstantIslands::updateForInsertedWaterBlock
691 (MachineBasicBlock *NewBB) {
692 // Renumber the MBB's to keep them consecutive.
693 NewBB->getParent()->RenumberBlocks(NewBB);
695 // Insert an entry into BBInfo to align it properly with the (newly
696 // renumbered) block numbers.
697 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
699 // Next, update WaterList. Specifically, we need to add NewMBB as having
700 // available water after it.
702 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
704 WaterList.insert(IP, NewBB);
707 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
708 return getOffsetOf(U.MI);
711 /// Split the basic block containing MI into two blocks, which are joined by
712 /// an unconditional branch. Update data structures and renumber blocks to
713 /// account for this change and returns the newly created block.
714 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
716 MachineBasicBlock *OrigBB = MI->getParent();
718 // Create a new MBB for the code after the OrigBB.
719 MachineBasicBlock *NewBB =
720 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
721 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
722 MF->insert(MBBI, NewBB);
724 // Splice the instructions starting with MI over to NewBB.
725 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
727 // Add an unconditional branch from OrigBB to NewBB.
728 // Note the new unconditional branch is not being recorded.
729 // There doesn't seem to be meaningful DebugInfo available; this doesn't
730 // correspond to anything in the source.
731 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::BimmX16)).addMBB(NewBB);
734 // Update the CFG. All succs of OrigBB are now succs of NewBB.
735 NewBB->transferSuccessors(OrigBB);
737 // OrigBB branches to NewBB.
738 OrigBB->addSuccessor(NewBB);
740 // Update internal data structures to account for the newly inserted MBB.
741 // This is almost the same as updateForInsertedWaterBlock, except that
742 // the Water goes after OrigBB, not NewBB.
743 MF->RenumberBlocks(NewBB);
745 // Insert an entry into BBInfo to align it properly with the (newly
746 // renumbered) block numbers.
747 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
749 // Next, update WaterList. Specifically, we need to add OrigMBB as having
750 // available water after it (but not if it's already there, which happens
751 // when splitting before a conditional branch that is followed by an
752 // unconditional branch - in that case we want to insert NewBB).
754 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
756 MachineBasicBlock* WaterBB = *IP;
757 if (WaterBB == OrigBB)
758 WaterList.insert(llvm::next(IP), NewBB);
760 WaterList.insert(IP, OrigBB);
761 NewWaterList.insert(OrigBB);
763 // Figure out how large the OrigBB is. As the first half of the original
764 // block, it cannot contain a tablejump. The size includes
765 // the new jump we added. (It should be possible to do this without
766 // recounting everything, but it's very confusing, and this is rarely
768 computeBlockSize(OrigBB);
770 // Figure out how large the NewMBB is. As the second half of the original
771 // block, it may contain a tablejump.
772 computeBlockSize(NewBB);
774 // All BBOffsets following these blocks must be modified.
775 adjustBBOffsetsAfter(OrigBB);
782 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
783 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
784 /// constant pool entry).
785 /// UserOffset is computed by getUserOffset above to include PC adjustments. If
786 /// the mod 4 alignment of UserOffset is not known, the uncertainty must be
787 /// subtracted from MaxDisp instead. CPUser::getMaxDisp() does that.
788 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
789 unsigned TrialOffset, unsigned MaxDisp,
791 if (UserOffset <= TrialOffset) {
792 // User before the Trial.
793 if (TrialOffset - UserOffset <= MaxDisp)
795 } else if (NegativeOK) {
796 if (UserOffset - TrialOffset <= MaxDisp)
802 /// isWaterInRange - Returns true if a CPE placed after the specified
803 /// Water (a basic block) will be in range for the specific MI.
805 /// Compute how much the function will grow by inserting a CPE after Water.
806 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
807 MachineBasicBlock* Water, CPUser &U,
809 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
810 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
811 unsigned NextBlockOffset, NextBlockAlignment;
812 MachineFunction::const_iterator NextBlock = Water;
813 if (++NextBlock == MF->end()) {
814 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
815 NextBlockAlignment = 0;
817 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
818 NextBlockAlignment = NextBlock->getAlignment();
820 unsigned Size = U.CPEMI->getOperand(2).getImm();
821 unsigned CPEEnd = CPEOffset + Size;
823 // The CPE may be able to hide in the alignment padding before the next
824 // block. It may also cause more padding to be required if it is more aligned
825 // that the next block.
826 if (CPEEnd > NextBlockOffset) {
827 Growth = CPEEnd - NextBlockOffset;
828 // Compute the padding that would go at the end of the CPE to align the next
830 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
832 // If the CPE is to be inserted before the instruction, that will raise
833 // the offset of the instruction. Also account for unknown alignment padding
834 // in blocks between CPE and the user.
835 if (CPEOffset < UserOffset)
836 UserOffset += Growth;
838 // CPE fits in existing padding.
841 return isOffsetInRange(UserOffset, CPEOffset, U);
844 /// isCPEntryInRange - Returns true if the distance between specific MI and
845 /// specific ConstPool entry instruction can fit in MI's displacement field.
846 bool MipsConstantIslands::isCPEntryInRange
847 (MachineInstr *MI, unsigned UserOffset,
848 MachineInstr *CPEMI, unsigned MaxDisp,
849 bool NegOk, bool DoDump) {
850 unsigned CPEOffset = getOffsetOf(CPEMI);
854 unsigned Block = MI->getParent()->getNumber();
855 const BasicBlockInfo &BBI = BBInfo[Block];
856 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
857 << " max delta=" << MaxDisp
858 << format(" insn address=%#x", UserOffset)
859 << " in BB#" << Block << ": "
860 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
861 << format("CPE address=%#x offset=%+d: ", CPEOffset,
862 int(CPEOffset-UserOffset));
866 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
870 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
871 /// unconditionally branches to its only successor.
872 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
873 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
875 MachineBasicBlock *Succ = *MBB->succ_begin();
876 MachineBasicBlock *Pred = *MBB->pred_begin();
877 MachineInstr *PredMI = &Pred->back();
878 if (PredMI->getOpcode() == Mips::BimmX16)
879 return PredMI->getOperand(0).getMBB() == Succ;
884 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
885 unsigned BBNum = BB->getNumber();
886 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
887 // Get the offset and known bits at the end of the layout predecessor.
888 // Include the alignment of the current block.
889 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
890 BBInfo[i].Offset = Offset;
894 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
895 /// and instruction CPEMI, and decrement its refcount. If the refcount
896 /// becomes 0 remove the entry and instruction. Returns true if we removed
897 /// the entry, false if we didn't.
899 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
900 MachineInstr *CPEMI) {
901 // Find the old entry. Eliminate it if it is no longer used.
902 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
903 assert(CPE && "Unexpected!");
904 if (--CPE->RefCount == 0) {
905 removeDeadCPEMI(CPEMI);
913 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
914 /// if not, see if an in-range clone of the CPE is in range, and if so,
915 /// change the data structures so the user references the clone. Returns:
916 /// 0 = no existing entry found
917 /// 1 = entry found, and there were no code insertions or deletions
918 /// 2 = entry found, and there were code insertions or deletions
919 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
921 MachineInstr *UserMI = U.MI;
922 MachineInstr *CPEMI = U.CPEMI;
924 // Check to see if the CPE is already in-range.
925 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
927 DEBUG(dbgs() << "In range\n");
931 // No. Look for previously created clones of the CPE that are in range.
932 unsigned CPI = CPEMI->getOperand(1).getIndex();
933 std::vector<CPEntry> &CPEs = CPEntries[CPI];
934 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
935 // We already tried this one
936 if (CPEs[i].CPEMI == CPEMI)
938 // Removing CPEs can leave empty entries, skip
939 if (CPEs[i].CPEMI == NULL)
941 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
943 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
944 << CPEs[i].CPI << "\n");
945 // Point the CPUser node to the replacement
946 U.CPEMI = CPEs[i].CPEMI;
947 // Change the CPI in the instruction operand to refer to the clone.
948 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
949 if (UserMI->getOperand(j).isCPI()) {
950 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
953 // Adjust the refcount of the clone...
955 // ...and the original. If we didn't remove the old entry, none of the
956 // addresses changed, so we don't need another pass.
957 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
963 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
964 /// This version checks if the longer form of the instruction can be used to
965 /// to satisfy things.
966 /// if not, see if an in-range clone of the CPE is in range, and if so,
967 /// change the data structures so the user references the clone. Returns:
968 /// 0 = no existing entry found
969 /// 1 = entry found, and there were no code insertions or deletions
970 /// 2 = entry found, and there were code insertions or deletions
971 int MipsConstantIslands::findLongFormInRangeCPEntry
972 (CPUser& U, unsigned UserOffset)
974 MachineInstr *UserMI = U.MI;
975 MachineInstr *CPEMI = U.CPEMI;
977 // Check to see if the CPE is already in-range.
978 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
979 U.getLongFormMaxDisp(), U.NegOk,
981 DEBUG(dbgs() << "In range\n");
982 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
983 return 2; // instruction is longer length now
986 // No. Look for previously created clones of the CPE that are in range.
987 unsigned CPI = CPEMI->getOperand(1).getIndex();
988 std::vector<CPEntry> &CPEs = CPEntries[CPI];
989 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
990 // We already tried this one
991 if (CPEs[i].CPEMI == CPEMI)
993 // Removing CPEs can leave empty entries, skip
994 if (CPEs[i].CPEMI == NULL)
996 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
997 U.getLongFormMaxDisp(), U.NegOk)) {
998 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
999 << CPEs[i].CPI << "\n");
1000 // Point the CPUser node to the replacement
1001 U.CPEMI = CPEs[i].CPEMI;
1002 // Change the CPI in the instruction operand to refer to the clone.
1003 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1004 if (UserMI->getOperand(j).isCPI()) {
1005 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1008 // Adjust the refcount of the clone...
1010 // ...and the original. If we didn't remove the old entry, none of the
1011 // addresses changed, so we don't need another pass.
1012 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1018 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1019 /// the specific unconditional branch instruction.
1020 static inline unsigned getUnconditionalBrDisp(int Opc) {
1023 return ((1<<16)-1)*2;
1027 return ((1<<16)-1)*2;
1030 /// findAvailableWater - Look for an existing entry in the WaterList in which
1031 /// we can place the CPE referenced from U so it's within range of U's MI.
1032 /// Returns true if found, false if not. If it returns true, WaterIter
1033 /// is set to the WaterList entry.
1034 /// To ensure that this pass
1035 /// terminates, the CPE location for a particular CPUser is only allowed to
1036 /// move to a lower address, so search backward from the end of the list and
1037 /// prefer the first water that is in range.
1038 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1039 water_iterator &WaterIter) {
1040 if (WaterList.empty())
1043 unsigned BestGrowth = ~0u;
1044 for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();;
1046 MachineBasicBlock* WaterBB = *IP;
1047 // Check if water is in range and is either at a lower address than the
1048 // current "high water mark" or a new water block that was created since
1049 // the previous iteration by inserting an unconditional branch. In the
1050 // latter case, we want to allow resetting the high water mark back to
1051 // this new water since we haven't seen it before. Inserting branches
1052 // should be relatively uncommon and when it does happen, we want to be
1053 // sure to take advantage of it for all the CPEs near that block, so that
1054 // we don't insert more branches than necessary.
1056 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1057 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1058 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1059 // This is the least amount of required padding seen so far.
1060 BestGrowth = Growth;
1062 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1063 << " Growth=" << Growth << '\n');
1065 // Keep looking unless it is perfect.
1066 if (BestGrowth == 0)
1072 return BestGrowth != ~0u;
1075 /// createNewWater - No existing WaterList entry will work for
1076 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1077 /// block is used if in range, and the conditional branch munged so control
1078 /// flow is correct. Otherwise the block is split to create a hole with an
1079 /// unconditional branch around it. In either case NewMBB is set to a
1080 /// block following which the new island can be inserted (the WaterList
1081 /// is not adjusted).
1082 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1083 unsigned UserOffset,
1084 MachineBasicBlock *&NewMBB) {
1085 CPUser &U = CPUsers[CPUserIndex];
1086 MachineInstr *UserMI = U.MI;
1087 MachineInstr *CPEMI = U.CPEMI;
1088 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1089 MachineBasicBlock *UserMBB = UserMI->getParent();
1090 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1092 // If the block does not end in an unconditional branch already, and if the
1093 // end of the block is within range, make new water there.
1094 if (BBHasFallthrough(UserMBB)) {
1095 // Size of branch to insert.
1097 // Compute the offset where the CPE will begin.
1098 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1100 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1101 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1102 << format(", expected CPE offset %#x\n", CPEOffset));
1103 NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
1104 // Add an unconditional branch from UserMBB to fallthrough block. Record
1105 // it for branch lengthening; this new branch will not get out of range,
1106 // but if the preceding conditional branch is out of range, the targets
1107 // will be exchanged, and the altered branch may be out of range, so the
1108 // machinery has to know about it.
1109 int UncondBr = Mips::BimmX16;
1110 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1111 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1112 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1113 MaxDisp, false, UncondBr));
1114 BBInfo[UserMBB->getNumber()].Size += Delta;
1115 adjustBBOffsetsAfter(UserMBB);
1120 // What a big block. Find a place within the block to split it.
1122 // Try to split the block so it's fully aligned. Compute the latest split
1123 // point where we can add a 4-byte branch instruction, and then align to
1124 // LogAlign which is the largest possible alignment in the function.
1125 unsigned LogAlign = MF->getAlignment();
1126 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1127 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1128 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1131 // The 4 in the following is for the unconditional branch we'll be inserting
1132 // Alignment of the island is handled
1133 // inside isOffsetInRange.
1134 BaseInsertOffset -= 4;
1136 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1137 << " la=" << LogAlign << '\n');
1139 // This could point off the end of the block if we've already got constant
1140 // pool entries following this block; only the last one is in the water list.
1141 // Back past any possible branches (allow for a conditional and a maximally
1142 // long unconditional).
1143 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1144 BaseInsertOffset = UserBBI.postOffset() - 8;
1145 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1147 unsigned EndInsertOffset = BaseInsertOffset + 4 +
1148 CPEMI->getOperand(2).getImm();
1149 MachineBasicBlock::iterator MI = UserMI;
1151 unsigned CPUIndex = CPUserIndex+1;
1152 unsigned NumCPUsers = CPUsers.size();
1153 //MachineInstr *LastIT = 0;
1154 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1155 Offset < BaseInsertOffset;
1156 Offset += TII->GetInstSizeInBytes(MI),
1157 MI = llvm::next(MI)) {
1158 assert(MI != UserMBB->end() && "Fell off end of block");
1159 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1160 CPUser &U = CPUsers[CPUIndex];
1161 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1162 // Shift intertion point by one unit of alignment so it is within reach.
1163 BaseInsertOffset -= 1u << LogAlign;
1164 EndInsertOffset -= 1u << LogAlign;
1166 // This is overly conservative, as we don't account for CPEMIs being
1167 // reused within the block, but it doesn't matter much. Also assume CPEs
1168 // are added in order with alignment padding. We may eventually be able
1169 // to pack the aligned CPEs better.
1170 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1176 NewMBB = splitBlockBeforeInstr(MI);
1179 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1180 /// is out-of-range. If so, pick up the constant pool value and move it some
1181 /// place in-range. Return true if we changed any addresses (thus must run
1182 /// another pass of branch lengthening), false otherwise.
1183 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1184 CPUser &U = CPUsers[CPUserIndex];
1185 MachineInstr *UserMI = U.MI;
1186 MachineInstr *CPEMI = U.CPEMI;
1187 unsigned CPI = CPEMI->getOperand(1).getIndex();
1188 unsigned Size = CPEMI->getOperand(2).getImm();
1189 // Compute this only once, it's expensive.
1190 unsigned UserOffset = getUserOffset(U);
1192 // See if the current entry is within range, or there is a clone of it
1194 int result = findInRangeCPEntry(U, UserOffset);
1195 if (result==1) return false;
1196 else if (result==2) return true;
1199 // Look for water where we can place this CPE.
1200 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1201 MachineBasicBlock *NewMBB;
1203 if (findAvailableWater(U, UserOffset, IP)) {
1204 DEBUG(dbgs() << "Found water in range\n");
1205 MachineBasicBlock *WaterBB = *IP;
1207 // If the original WaterList entry was "new water" on this iteration,
1208 // propagate that to the new island. This is just keeping NewWaterList
1209 // updated to match the WaterList, which will be updated below.
1210 if (NewWaterList.erase(WaterBB))
1211 NewWaterList.insert(NewIsland);
1213 // The new CPE goes before the following block (NewMBB).
1214 NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
1218 // we first see if a longer form of the instrucion could have reached
1219 // the constant. in that case we won't bother to split
1221 result = findLongFormInRangeCPEntry(U, UserOffset);
1223 DEBUG(dbgs() << "No water found\n");
1224 createNewWater(CPUserIndex, UserOffset, NewMBB);
1226 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1227 // called while handling branches so that the water will be seen on the
1228 // next iteration for constant pools, but in this context, we don't want
1229 // it. Check for this so it will be removed from the WaterList.
1230 // Also remove any entry from NewWaterList.
1231 MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
1232 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1233 if (IP != WaterList.end())
1234 NewWaterList.erase(WaterBB);
1236 // We are adding new water. Update NewWaterList.
1237 NewWaterList.insert(NewIsland);
1240 // Remove the original WaterList entry; we want subsequent insertions in
1241 // this vicinity to go after the one we're about to insert. This
1242 // considerably reduces the number of times we have to move the same CPE
1243 // more than once and is also important to ensure the algorithm terminates.
1244 if (IP != WaterList.end())
1245 WaterList.erase(IP);
1247 // Okay, we know we can put an island before NewMBB now, do it!
1248 MF->insert(NewMBB, NewIsland);
1250 // Update internal data structures to account for the newly inserted MBB.
1251 updateForInsertedWaterBlock(NewIsland);
1253 // Decrement the old entry, and remove it if refcount becomes 0.
1254 decrementCPEReferenceCount(CPI, CPEMI);
1256 // Now that we have an island to add the CPE to, clone the original CPE and
1257 // add it to the island.
1258 U.HighWaterMark = NewIsland;
1259 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1260 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1261 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1264 // Mark the basic block as aligned as required by the const-pool entry.
1265 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1267 // Increase the size of the island block to account for the new entry.
1268 BBInfo[NewIsland->getNumber()].Size += Size;
1269 adjustBBOffsetsAfter(llvm::prior(MachineFunction::iterator(NewIsland)));
1271 // No existing clone of this CPE is within range.
1272 // We will be generating a new clone. Get a UID for it.
1273 unsigned ID = createPICLabelUId();
1275 // Finally, change the CPI in the instruction operand to be ID.
1276 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1277 if (UserMI->getOperand(i).isCPI()) {
1278 UserMI->getOperand(i).setIndex(ID);
1282 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1283 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1288 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1289 /// sizes and offsets of impacted basic blocks.
1290 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1291 MachineBasicBlock *CPEBB = CPEMI->getParent();
1292 unsigned Size = CPEMI->getOperand(2).getImm();
1293 CPEMI->eraseFromParent();
1294 BBInfo[CPEBB->getNumber()].Size -= Size;
1295 // All succeeding offsets have the current size value added in, fix this.
1296 if (CPEBB->empty()) {
1297 BBInfo[CPEBB->getNumber()].Size = 0;
1299 // This block no longer needs to be aligned.
1300 CPEBB->setAlignment(0);
1302 // Entries are sorted by descending alignment, so realign from the front.
1303 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1305 adjustBBOffsetsAfter(CPEBB);
1306 // An island has only one predecessor BB and one successor BB. Check if
1307 // this BB's predecessor jumps directly to this BB's successor. This
1308 // shouldn't happen currently.
1309 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1310 // FIXME: remove the empty blocks after all the work is done?
1313 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1315 bool MipsConstantIslands::removeUnusedCPEntries() {
1316 unsigned MadeChange = false;
1317 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1318 std::vector<CPEntry> &CPEs = CPEntries[i];
1319 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1320 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1321 removeDeadCPEMI(CPEs[j].CPEMI);
1322 CPEs[j].CPEMI = NULL;
1330 /// isBBInRange - Returns true if the distance between specific MI and
1331 /// specific BB can fit in MI's displacement field.
1332 bool MipsConstantIslands::isBBInRange
1333 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1337 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1338 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1340 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1341 << " from BB#" << MI->getParent()->getNumber()
1342 << " max delta=" << MaxDisp
1343 << " from " << getOffsetOf(MI) << " to " << DestOffset
1344 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1346 if (BrOffset <= DestOffset) {
1347 // Branch before the Dest.
1348 if (DestOffset-BrOffset <= MaxDisp)
1351 if (BrOffset-DestOffset <= MaxDisp)
1357 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1358 /// away to fit in its displacement field.
1359 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1360 MachineInstr *MI = Br.MI;
1361 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1363 // Check to see if the DestBB is already in-range.
1364 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1368 return fixupUnconditionalBr(Br);
1369 return fixupConditionalBr(Br);
1372 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1373 /// too far away to fit in its displacement field. If the LR register has been
1374 /// spilled in the epilogue, then we can use BL to implement a far jump.
1375 /// Otherwise, add an intermediate branch instruction to a branch.
1377 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1378 MachineInstr *MI = Br.MI;
1379 MachineBasicBlock *MBB = MI->getParent();
1380 // Use BL to implement far jump.
1381 Br.MaxDisp = ((1 << 16)-1) * 2;
1382 MI->setDesc(TII->get(Mips::BimmX16));
1383 BBInfo[MBB->getNumber()].Size += 2;
1384 adjustBBOffsetsAfter(MBB);
1388 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1393 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1394 /// far away to fit in its displacement field. It is converted to an inverse
1395 /// conditional branch + an unconditional branch to the destination.
1397 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1398 MachineInstr *MI = Br.MI;
1399 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1401 // Add an unconditional branch to the destination and invert the branch
1402 // condition to jump over it:
1408 unsigned CCReg = 0; // FIXME
1409 unsigned CC=0; //FIXME
1411 // If the branch is at the end of its MBB and that has a fall-through block,
1412 // direct the updated conditional branch to the fall-through block. Otherwise,
1413 // split the MBB before the next instruction.
1414 MachineBasicBlock *MBB = MI->getParent();
1415 MachineInstr *BMI = &MBB->back();
1416 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1420 if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
1421 BMI->getOpcode() == Br.UncondBr) {
1422 // Last MI in the BB is an unconditional branch. Can we simply invert the
1423 // condition and swap destinations:
1429 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
1430 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1431 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1433 BMI->getOperand(0).setMBB(DestBB);
1434 MI->getOperand(0).setMBB(NewDest);
1441 splitBlockBeforeInstr(MI);
1442 // No need for the branch to the next block. We're adding an unconditional
1443 // branch to the destination.
1444 int delta = TII->GetInstSizeInBytes(&MBB->back());
1445 BBInfo[MBB->getNumber()].Size -= delta;
1446 MBB->back().eraseFromParent();
1447 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1449 MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
1451 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1452 << " also invert condition and change dest. to BB#"
1453 << NextBB->getNumber() << "\n");
1455 // Insert a new conditional branch and a new unconditional branch.
1456 // Also update the ImmBranch as well as adding a new entry for the new branch.
1457 BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode()))
1458 .addMBB(NextBB).addImm(CC).addReg(CCReg);
1459 Br.MI = &MBB->back();
1460 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1461 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1462 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1463 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1464 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1466 // Remove the old conditional branch. It may or may not still be in MBB.
1467 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1468 MI->eraseFromParent();
1469 adjustBBOffsetsAfter(MBB);
1474 void MipsConstantIslands::prescanForConstants() {
1477 PrescannedForConstants = true;
1478 for (MachineFunction::iterator B =
1479 MF->begin(), E = MF->end(); B != E; ++B) {
1480 for (MachineBasicBlock::instr_iterator I =
1481 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1482 switch(I->getDesc().getOpcode()) {
1483 case Mips::LwConstant32: {
1484 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1485 J = I->getNumOperands();
1486 DEBUG(dbgs() << "num operands " << J << "\n");
1487 MachineOperand& Literal = I->getOperand(1);
1488 if (Literal.isImm()) {
1489 int64_t V = Literal.getImm();
1490 DEBUG(dbgs() << "literal " << V << "\n");
1492 Type::getInt32Ty(MF->getFunction()->getContext());
1493 const Constant *C = ConstantInt::get(Int32Ty, V);
1494 unsigned index = MCP->getConstantPoolIndex(C, 4);
1495 I->getOperand(2).ChangeToImmediate(index);
1496 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1497 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1498 I->RemoveOperand(1);
1499 I->RemoveOperand(1);
1500 I->addOperand(MachineOperand::CreateCPI(index, 0));
1501 I->addOperand(MachineOperand::CreateImm(4));