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. While it has the same name and
13 // uses many ideas from the LLVM ARM Constant Island Pass, it's not intended
14 // to reuse any of the code from the ARM version.
16 // Loading constants inline is expensive on Mips16 and it's in general better
17 // to place the constant nearby in code space and then it can be loaded with a
18 // simple 16 bit load instruction.
20 // The constants can be not just numbers but addresses of functions and labels.
21 // This can be particularly helpful in static relocation mode for embedded
26 #define DEBUG_TYPE "mips-constant-islands"
29 #include "MCTargetDesc/MipsBaseInfo.h"
30 #include "MipsMachineFunction.h"
31 #include "MipsTargetMachine.h"
32 #include "llvm/ADT/Statistic.h"
33 #include "llvm/CodeGen/MachineBasicBlock.h"
34 #include "llvm/CodeGen/MachineFunctionPass.h"
35 #include "llvm/CodeGen/MachineInstrBuilder.h"
36 #include "llvm/CodeGen/MachineRegisterInfo.h"
37 #include "llvm/IR/Function.h"
38 #include "llvm/Support/CommandLine.h"
39 #include "llvm/Support/Debug.h"
40 #include "llvm/Support/InstIterator.h"
41 #include "llvm/Support/MathExtras.h"
42 #include "llvm/Support/raw_ostream.h"
43 #include "llvm/Target/TargetInstrInfo.h"
44 #include "llvm/Target/TargetMachine.h"
45 #include "llvm/Target/TargetRegisterInfo.h"
46 #include "llvm/Support/Format.h"
51 STATISTIC(NumCPEs, "Number of constpool entries");
52 STATISTIC(NumSplit, "Number of uncond branches inserted");
53 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
54 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
56 // FIXME: This option should be removed once it has received sufficient testing.
58 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
59 cl::desc("Align constant islands in code"));
62 // Rather than do make check tests with huge amounts of code, we force
63 // the test to use this amount.
65 static cl::opt<int> ConstantIslandsSmallOffset(
66 "mips-constant-islands-small-offset",
68 cl::desc("Make small offsets be this amount for testing purposes"),
71 /// UnknownPadding - Return the worst case padding that could result from
72 /// unknown offset bits. This does not include alignment padding caused by
73 /// known offset bits.
75 /// @param LogAlign log2(alignment)
76 /// @param KnownBits Number of known low offset bits.
77 static inline unsigned UnknownPadding(unsigned LogAlign, unsigned KnownBits) {
78 if (KnownBits < LogAlign)
79 return (1u << LogAlign) - (1u << KnownBits);
86 typedef MachineBasicBlock::iterator Iter;
87 typedef MachineBasicBlock::reverse_iterator ReverseIter;
89 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
90 /// requires constant pool entries to be scattered among the instructions
91 /// inside a function. To do this, it completely ignores the normal LLVM
92 /// constant pool; instead, it places constants wherever it feels like with
93 /// special instructions.
95 /// The terminology used in this pass includes:
96 /// Islands - Clumps of constants placed in the function.
97 /// Water - Potential places where an island could be formed.
98 /// CPE - A constant pool entry that has been placed somewhere, which
99 /// tracks a list of users.
101 class MipsConstantIslands : public MachineFunctionPass {
103 /// BasicBlockInfo - Information about the offset and size of a single
105 struct BasicBlockInfo {
106 /// Offset - Distance from the beginning of the function to the beginning
107 /// of this basic block.
109 /// Offsets are computed assuming worst case padding before an aligned
110 /// block. This means that subtracting basic block offsets always gives a
111 /// conservative estimate of the real distance which may be smaller.
113 /// Because worst case padding is used, the computed offset of an aligned
114 /// block may not actually be aligned.
117 /// Size - Size of the basic block in bytes. If the block contains
118 /// inline assembly, this is a worst case estimate.
120 /// The size does not include any alignment padding whether from the
121 /// beginning of the block, or from an aligned jump table at the end.
124 /// KnownBits - The number of low bits in Offset that are known to be
125 /// exact. The remaining bits of Offset are an upper bound.
128 /// Unalign - When non-zero, the block contains instructions (inline asm)
129 /// of unknown size. The real size may be smaller than Size bytes by a
130 /// multiple of 1 << Unalign.
133 /// PostAlign - When non-zero, the block terminator contains a .align
134 /// directive, so the end of the block is aligned to 1 << PostAlign
138 BasicBlockInfo() : Offset(0), Size(0), KnownBits(0), Unalign(0),
141 /// Compute the number of known offset bits internally to this block.
142 /// This number should be used to predict worst case padding when
143 /// splitting the block.
144 unsigned internalKnownBits() const {
145 unsigned Bits = Unalign ? Unalign : KnownBits;
146 // If the block size isn't a multiple of the known bits, assume the
147 // worst case padding.
148 if (Size & ((1u << Bits) - 1))
149 Bits = countTrailingZeros(Size);
153 /// Compute the offset immediately following this block. If LogAlign is
154 /// specified, return the offset the successor block will get if it has
156 unsigned postOffset(unsigned LogAlign = 0) const {
157 unsigned PO = Offset + Size;
161 /// Compute the number of known low bits of postOffset. If this block
162 /// contains inline asm, the number of known bits drops to the
163 /// instruction alignment. An aligned terminator may increase the number
165 /// If LogAlign is given, also consider the alignment of the next block.
166 unsigned postKnownBits(unsigned LogAlign = 0) const {
167 return std::max(std::max(unsigned(PostAlign), LogAlign),
168 internalKnownBits());
172 std::vector<BasicBlockInfo> BBInfo;
174 /// WaterList - A sorted list of basic blocks where islands could be placed
175 /// (i.e. blocks that don't fall through to the following block, due
176 /// to a return, unreachable, or unconditional branch).
177 std::vector<MachineBasicBlock*> WaterList;
179 /// NewWaterList - The subset of WaterList that was created since the
180 /// previous iteration by inserting unconditional branches.
181 SmallSet<MachineBasicBlock*, 4> NewWaterList;
183 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
185 /// CPUser - One user of a constant pool, keeping the machine instruction
186 /// pointer, the constant pool being referenced, and the max displacement
187 /// allowed from the instruction to the CP. The HighWaterMark records the
188 /// highest basic block where a new CPEntry can be placed. To ensure this
189 /// pass terminates, the CP entries are initially placed at the end of the
190 /// function and then move monotonically to lower addresses. The
191 /// exception to this rule is when the current CP entry for a particular
192 /// CPUser is out of range, but there is another CP entry for the same
193 /// constant value in range. We want to use the existing in-range CP
194 /// entry, but if it later moves out of range, the search for new water
195 /// should resume where it left off. The HighWaterMark is used to record
200 MachineBasicBlock *HighWaterMark;
203 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
204 // with different displacements
205 unsigned LongFormOpcode;
210 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
211 bool neg, bool soimm,
212 unsigned longformmaxdisp, unsigned longformopcode)
213 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
214 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
215 NegOk(neg), IsSoImm(soimm), KnownAlignment(false) {
216 HighWaterMark = CPEMI->getParent();
218 /// getMaxDisp - Returns the maximum displacement supported by MI.
219 /// Correct for unknown alignment.
220 /// Conservatively subtract 2 bytes to handle weird alignment effects.
221 unsigned getMaxDisp() const {
222 unsigned xMaxDisp = ConstantIslandsSmallOffset?
223 ConstantIslandsSmallOffset: MaxDisp;
224 return (KnownAlignment ? xMaxDisp : xMaxDisp - 2) - 2;
226 unsigned getLongFormMaxDisp() const {
227 return (KnownAlignment ? LongFormMaxDisp : LongFormMaxDisp - 2) - 2;
229 unsigned getLongFormOpcode() const {
230 return LongFormOpcode;
234 /// CPUsers - Keep track of all of the machine instructions that use various
235 /// constant pools and their max displacement.
236 std::vector<CPUser> CPUsers;
238 /// CPEntry - One per constant pool entry, keeping the machine instruction
239 /// pointer, the constpool index, and the number of CPUser's which
240 /// reference this entry.
245 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
246 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
249 /// CPEntries - Keep track of all of the constant pool entry machine
250 /// instructions. For each original constpool index (i.e. those that
251 /// existed upon entry to this pass), it keeps a vector of entries.
252 /// Original elements are cloned as we go along; the clones are
253 /// put in the vector of the original element, but have distinct CPIs.
254 std::vector<std::vector<CPEntry> > CPEntries;
256 /// ImmBranch - One per immediate branch, keeping the machine instruction
257 /// pointer, conditional or unconditional, the max displacement,
258 /// and (if isCond is true) the corresponding unconditional branch
262 unsigned MaxDisp : 31;
265 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
266 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
269 /// ImmBranches - Keep track of all the immediate branch instructions.
271 std::vector<ImmBranch> ImmBranches;
273 /// HasFarJump - True if any far jump instruction has been emitted during
274 /// the branch fix up pass.
277 const TargetMachine &TM;
280 const MipsSubtarget *STI;
281 const MipsInstrInfo *TII;
282 MipsFunctionInfo *MFI;
284 MachineConstantPool *MCP;
286 unsigned PICLabelUId;
287 bool PrescannedForConstants;
289 void initPICLabelUId(unsigned UId) {
294 unsigned createPICLabelUId() {
295 return PICLabelUId++;
300 MipsConstantIslands(TargetMachine &tm)
301 : MachineFunctionPass(ID), TM(tm),
302 IsPIC(TM.getRelocationModel() == Reloc::PIC_),
303 ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
304 STI(&TM.getSubtarget<MipsSubtarget>()), MF(0), MCP(0),
305 PrescannedForConstants(false){}
307 virtual const char *getPassName() const {
308 return "Mips Constant Islands";
311 bool runOnMachineFunction(MachineFunction &F);
313 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
314 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
315 unsigned getCPELogAlign(const MachineInstr *CPEMI);
316 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
317 unsigned getOffsetOf(MachineInstr *MI) const;
318 unsigned getUserOffset(CPUser&) const;
322 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
323 unsigned Disp, bool NegativeOK, bool IsSoImm = false);
324 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
327 bool isLongFormOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
330 void computeBlockSize(MachineBasicBlock *MBB);
331 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
332 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
333 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
334 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
335 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
336 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
337 bool findAvailableWater(CPUser&U, unsigned UserOffset,
338 water_iterator &WaterIter);
339 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
340 MachineBasicBlock *&NewMBB);
341 bool handleConstantPoolUser(unsigned CPUserIndex);
342 void removeDeadCPEMI(MachineInstr *CPEMI);
343 bool removeUnusedCPEntries();
344 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
345 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
346 bool DoDump = false);
347 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
348 CPUser &U, unsigned &Growth);
349 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
350 bool fixupImmediateBr(ImmBranch &Br);
351 bool fixupConditionalBr(ImmBranch &Br);
352 bool fixupUnconditionalBr(ImmBranch &Br);
354 void prescanForConstants();
360 char MipsConstantIslands::ID = 0;
361 } // end of anonymous namespace
364 bool MipsConstantIslands::isLongFormOffsetInRange
365 (unsigned UserOffset, unsigned TrialOffset,
367 return isOffsetInRange(UserOffset, TrialOffset,
368 U.getLongFormMaxDisp(), U.NegOk, U.IsSoImm);
371 bool MipsConstantIslands::isOffsetInRange
372 (unsigned UserOffset, unsigned TrialOffset,
374 return isOffsetInRange(UserOffset, TrialOffset,
375 U.getMaxDisp(), U.NegOk, U.IsSoImm);
377 /// print block size and offset information - debugging
378 void MipsConstantIslands::dumpBBs() {
380 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
381 const BasicBlockInfo &BBI = BBInfo[J];
382 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
383 << " kb=" << unsigned(BBI.KnownBits)
384 << " ua=" << unsigned(BBI.Unalign)
385 << " pa=" << unsigned(BBI.PostAlign)
386 << format(" size=%#x\n", BBInfo[J].Size);
390 /// createMipsLongBranchPass - Returns a pass that converts branches to long
392 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
393 return new MipsConstantIslands(tm);
396 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
397 // The intention is for this to be a mips16 only pass for now
400 MCP = mf.getConstantPool();
401 DEBUG(dbgs() << "constant island machine function " << "\n");
402 if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode() ||
403 !MipsSubtarget::useConstantIslands()) {
406 TII = (const MipsInstrInfo*)MF->getTarget().getInstrInfo();
407 MFI = MF->getInfo<MipsFunctionInfo>();
408 DEBUG(dbgs() << "constant island processing " << "\n");
410 // will need to make predermination if there is any constants we need to
411 // put in constant islands. TBD.
413 if (!PrescannedForConstants) prescanForConstants();
416 // This pass invalidates liveness information when it splits basic blocks.
417 MF->getRegInfo().invalidateLiveness();
419 // Renumber all of the machine basic blocks in the function, guaranteeing that
420 // the numbers agree with the position of the block in the function.
421 MF->RenumberBlocks();
423 bool MadeChange = false;
425 // Perform the initial placement of the constant pool entries. To start with,
426 // we put them all at the end of the function.
427 std::vector<MachineInstr*> CPEMIs;
429 doInitialPlacement(CPEMIs);
431 /// The next UID to take is the first unused one.
432 initPICLabelUId(CPEMIs.size());
434 // Do the initial scan of the function, building up information about the
435 // sizes of each block, the location of all the water, and finding all of the
436 // constant pool users.
437 initializeFunctionInfo(CPEMIs);
441 /// Remove dead constant pool entries.
442 MadeChange |= removeUnusedCPEntries();
444 // Iteratively place constant pool entries and fix up branches until there
446 unsigned NoCPIters = 0, NoBRIters = 0;
449 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
450 bool CPChange = false;
451 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
452 CPChange |= handleConstantPoolUser(i);
453 if (CPChange && ++NoCPIters > 30)
454 report_fatal_error("Constant Island pass failed to converge!");
457 // Clear NewWaterList now. If we split a block for branches, it should
458 // appear as "new water" for the next iteration of constant pool placement.
459 NewWaterList.clear();
461 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
462 bool BRChange = false;
464 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
465 BRChange |= fixupImmediateBr(ImmBranches[i]);
466 if (BRChange && ++NoBRIters > 30)
467 report_fatal_error("Branch Fix Up pass failed to converge!");
470 if (!CPChange && !BRChange)
475 DEBUG(dbgs() << '\n'; dumpBBs());
485 /// doInitialPlacement - Perform the initial placement of the constant pool
486 /// entries. To start with, we put them all at the end of the function.
488 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
489 // Create the basic block to hold the CPE's.
490 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
494 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
495 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
497 // Mark the basic block as required by the const-pool.
498 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
499 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
501 // The function needs to be as aligned as the basic blocks. The linker may
502 // move functions around based on their alignment.
503 MF->ensureAlignment(BB->getAlignment());
505 // Order the entries in BB by descending alignment. That ensures correct
506 // alignment of all entries as long as BB is sufficiently aligned. Keep
507 // track of the insertion point for each alignment. We are going to bucket
508 // sort the entries as they are created.
509 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
511 // Add all of the constants from the constant pool to the end block, use an
512 // identity mapping of CPI's to CPE's.
513 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
515 const DataLayout &TD = *MF->getTarget().getDataLayout();
516 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
517 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
518 assert(Size >= 4 && "Too small constant pool entry");
519 unsigned Align = CPs[i].getAlignment();
520 assert(isPowerOf2_32(Align) && "Invalid alignment");
521 // Verify that all constant pool entries are a multiple of their alignment.
522 // If not, we would have to pad them out so that instructions stay aligned.
523 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
525 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
526 unsigned LogAlign = Log2_32(Align);
527 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
529 MachineInstr *CPEMI =
530 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
531 .addImm(i).addConstantPoolIndex(i).addImm(Size);
533 CPEMIs.push_back(CPEMI);
535 // Ensure that future entries with higher alignment get inserted before
536 // CPEMI. This is bucket sort with iterators.
537 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
538 if (InsPoint[a] == InsAt)
540 // Add a new CPEntry, but no corresponding CPUser yet.
541 std::vector<CPEntry> CPEs;
542 CPEs.push_back(CPEntry(CPEMI, i));
543 CPEntries.push_back(CPEs);
545 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
546 << Size << ", align = " << Align <<'\n');
551 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
552 /// into the block immediately after it.
553 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
554 // Get the next machine basic block in the function.
555 MachineFunction::iterator MBBI = MBB;
556 // Can't fall off end of function.
557 if (llvm::next(MBBI) == MBB->getParent()->end())
560 MachineBasicBlock *NextBB = llvm::next(MBBI);
561 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
562 E = MBB->succ_end(); I != E; ++I)
569 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
570 /// look up the corresponding CPEntry.
571 MipsConstantIslands::CPEntry
572 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
573 const MachineInstr *CPEMI) {
574 std::vector<CPEntry> &CPEs = CPEntries[CPI];
575 // Number of entries per constpool index should be small, just do a
577 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
578 if (CPEs[i].CPEMI == CPEMI)
584 /// getCPELogAlign - Returns the required alignment of the constant pool entry
585 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
586 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
587 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
589 // Everything is 4-byte aligned unless AlignConstantIslands is set.
590 if (!AlignConstantIslands)
593 unsigned CPI = CPEMI->getOperand(1).getIndex();
594 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
595 unsigned Align = MCP->getConstants()[CPI].getAlignment();
596 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
597 return Log2_32(Align);
600 /// initializeFunctionInfo - Do the initial scan of the function, building up
601 /// information about the sizes of each block, the location of all the water,
602 /// and finding all of the constant pool users.
603 void MipsConstantIslands::
604 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
606 BBInfo.resize(MF->getNumBlockIDs());
608 // First thing, compute the size of all basic blocks, and see if the function
609 // has any inline assembly in it. If so, we have to be conservative about
610 // alignment assumptions, as we don't know for sure the size of any
611 // instructions in the inline assembly.
612 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
615 // The known bits of the entry block offset are determined by the function
617 BBInfo.front().KnownBits = MF->getAlignment();
619 // Compute block offsets.
620 adjustBBOffsetsAfter(MF->begin());
622 // Now go back through the instructions and build up our data structures.
623 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
625 MachineBasicBlock &MBB = *MBBI;
627 // If this block doesn't fall through into the next MBB, then this is
628 // 'water' that a constant pool island could be placed.
629 if (!BBHasFallthrough(&MBB))
630 WaterList.push_back(&MBB);
631 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
633 if (I->isDebugValue())
636 int Opc = I->getOpcode();
645 continue; // Ignore other JT branches
647 // Record this immediate branch.
648 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
649 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
654 if (Opc == Mips::CONSTPOOL_ENTRY)
658 // Scan the instructions for constant pool operands.
659 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
660 if (I->getOperand(op).isCPI()) {
662 // We found one. The addressing mode tells us the max displacement
663 // from the PC that this instruction permits.
665 // Basic size info comes from the TSFlags field.
669 bool IsSoImm = false;
670 unsigned LongFormBits = 0;
671 unsigned LongFormScale = 0;
672 unsigned LongFormOpcode = 0;
675 llvm_unreachable("Unknown addressing mode for CP reference!");
676 case Mips::LwRxPcTcp16:
679 LongFormOpcode = Mips::LwRxPcTcpX16;
681 case Mips::LwRxPcTcpX16:
686 // Remember that this is a user of a CP entry.
687 unsigned CPI = I->getOperand(op).getIndex();
688 MachineInstr *CPEMI = CPEMIs[CPI];
689 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
690 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
691 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
692 IsSoImm, LongFormMaxOffs,
695 // Increment corresponding CPEntry reference count.
696 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
697 assert(CPE && "Cannot find a corresponding CPEntry!");
700 // Instructions can only use one CP entry, don't bother scanning the
701 // rest of the operands.
711 /// computeBlockSize - Compute the size and some alignment information for MBB.
712 /// This function updates BBInfo directly.
713 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
714 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
719 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
721 BBI.Size += TII->GetInstSizeInBytes(I);
725 /// getOffsetOf - Return the current offset of the specified machine instruction
726 /// from the start of the function. This offset changes as stuff is moved
727 /// around inside the function.
728 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
729 MachineBasicBlock *MBB = MI->getParent();
731 // The offset is composed of two things: the sum of the sizes of all MBB's
732 // before this instruction's block, and the offset from the start of the block
734 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
736 // Sum instructions before MI in MBB.
737 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
738 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
739 Offset += TII->GetInstSizeInBytes(I);
744 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
746 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
747 const MachineBasicBlock *RHS) {
748 return LHS->getNumber() < RHS->getNumber();
751 /// updateForInsertedWaterBlock - When a block is newly inserted into the
752 /// machine function, it upsets all of the block numbers. Renumber the blocks
753 /// and update the arrays that parallel this numbering.
754 void MipsConstantIslands::updateForInsertedWaterBlock
755 (MachineBasicBlock *NewBB) {
756 // Renumber the MBB's to keep them consecutive.
757 NewBB->getParent()->RenumberBlocks(NewBB);
759 // Insert an entry into BBInfo to align it properly with the (newly
760 // renumbered) block numbers.
761 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
763 // Next, update WaterList. Specifically, we need to add NewMBB as having
764 // available water after it.
766 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
768 WaterList.insert(IP, NewBB);
771 /// getUserOffset - Compute the offset of U.MI as seen by the hardware
772 /// displacement computation. Update U.KnownAlignment to match its current
773 /// basic block location.
774 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
775 unsigned UserOffset = getOffsetOf(U.MI);
776 const BasicBlockInfo &BBI = BBInfo[U.MI->getParent()->getNumber()];
777 unsigned KnownBits = BBI.internalKnownBits();
779 // The value read from PC is offset from the actual instruction address.
782 // Because of inline assembly, we may not know the alignment (mod 4) of U.MI.
783 // Make sure U.getMaxDisp() returns a constrained range.
784 U.KnownAlignment = (KnownBits >= 2);
786 // On Thumb, offsets==2 mod 4 are rounded down by the hardware for
787 // purposes of the displacement computation; compensate for that here.
788 // For unknown alignments, getMaxDisp() constrains the range instead.
794 /// Split the basic block containing MI into two blocks, which are joined by
795 /// an unconditional branch. Update data structures and renumber blocks to
796 /// account for this change and returns the newly created block.
797 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
799 MachineBasicBlock *OrigBB = MI->getParent();
801 // Create a new MBB for the code after the OrigBB.
802 MachineBasicBlock *NewBB =
803 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
804 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
805 MF->insert(MBBI, NewBB);
807 // Splice the instructions starting with MI over to NewBB.
808 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
810 // Add an unconditional branch from OrigBB to NewBB.
811 // Note the new unconditional branch is not being recorded.
812 // There doesn't seem to be meaningful DebugInfo available; this doesn't
813 // correspond to anything in the source.
814 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::BimmX16)).addMBB(NewBB);
817 // Update the CFG. All succs of OrigBB are now succs of NewBB.
818 NewBB->transferSuccessors(OrigBB);
820 // OrigBB branches to NewBB.
821 OrigBB->addSuccessor(NewBB);
823 // Update internal data structures to account for the newly inserted MBB.
824 // This is almost the same as updateForInsertedWaterBlock, except that
825 // the Water goes after OrigBB, not NewBB.
826 MF->RenumberBlocks(NewBB);
828 // Insert an entry into BBInfo to align it properly with the (newly
829 // renumbered) block numbers.
830 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
832 // Next, update WaterList. Specifically, we need to add OrigMBB as having
833 // available water after it (but not if it's already there, which happens
834 // when splitting before a conditional branch that is followed by an
835 // unconditional branch - in that case we want to insert NewBB).
837 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
839 MachineBasicBlock* WaterBB = *IP;
840 if (WaterBB == OrigBB)
841 WaterList.insert(llvm::next(IP), NewBB);
843 WaterList.insert(IP, OrigBB);
844 NewWaterList.insert(OrigBB);
846 // Figure out how large the OrigBB is. As the first half of the original
847 // block, it cannot contain a tablejump. The size includes
848 // the new jump we added. (It should be possible to do this without
849 // recounting everything, but it's very confusing, and this is rarely
851 computeBlockSize(OrigBB);
853 // Figure out how large the NewMBB is. As the second half of the original
854 // block, it may contain a tablejump.
855 computeBlockSize(NewBB);
857 // All BBOffsets following these blocks must be modified.
858 adjustBBOffsetsAfter(OrigBB);
865 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
866 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
867 /// constant pool entry).
868 /// UserOffset is computed by getUserOffset above to include PC adjustments. If
869 /// the mod 4 alignment of UserOffset is not known, the uncertainty must be
870 /// subtracted from MaxDisp instead. CPUser::getMaxDisp() does that.
871 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
872 unsigned TrialOffset, unsigned MaxDisp,
873 bool NegativeOK, bool IsSoImm) {
874 if (UserOffset <= TrialOffset) {
875 // User before the Trial.
876 if (TrialOffset - UserOffset <= MaxDisp)
878 // FIXME: Make use full range of soimm values.
879 } else if (NegativeOK) {
880 if (UserOffset - TrialOffset <= MaxDisp)
882 // FIXME: Make use full range of soimm values.
887 /// isWaterInRange - Returns true if a CPE placed after the specified
888 /// Water (a basic block) will be in range for the specific MI.
890 /// Compute how much the function will grow by inserting a CPE after Water.
891 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
892 MachineBasicBlock* Water, CPUser &U,
894 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
895 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
896 unsigned NextBlockOffset, NextBlockAlignment;
897 MachineFunction::const_iterator NextBlock = Water;
898 if (++NextBlock == MF->end()) {
899 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
900 NextBlockAlignment = 0;
902 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
903 NextBlockAlignment = NextBlock->getAlignment();
905 unsigned Size = U.CPEMI->getOperand(2).getImm();
906 unsigned CPEEnd = CPEOffset + Size;
908 // The CPE may be able to hide in the alignment padding before the next
909 // block. It may also cause more padding to be required if it is more aligned
910 // that the next block.
911 if (CPEEnd > NextBlockOffset) {
912 Growth = CPEEnd - NextBlockOffset;
913 // Compute the padding that would go at the end of the CPE to align the next
915 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
917 // If the CPE is to be inserted before the instruction, that will raise
918 // the offset of the instruction. Also account for unknown alignment padding
919 // in blocks between CPE and the user.
920 if (CPEOffset < UserOffset)
921 UserOffset += Growth + UnknownPadding(MF->getAlignment(), CPELogAlign);
923 // CPE fits in existing padding.
926 return isOffsetInRange(UserOffset, CPEOffset, U);
929 /// isCPEntryInRange - Returns true if the distance between specific MI and
930 /// specific ConstPool entry instruction can fit in MI's displacement field.
931 bool MipsConstantIslands::isCPEntryInRange
932 (MachineInstr *MI, unsigned UserOffset,
933 MachineInstr *CPEMI, unsigned MaxDisp,
934 bool NegOk, bool DoDump) {
935 unsigned CPEOffset = getOffsetOf(CPEMI);
939 unsigned Block = MI->getParent()->getNumber();
940 const BasicBlockInfo &BBI = BBInfo[Block];
941 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
942 << " max delta=" << MaxDisp
943 << format(" insn address=%#x", UserOffset)
944 << " in BB#" << Block << ": "
945 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
946 << format("CPE address=%#x offset=%+d: ", CPEOffset,
947 int(CPEOffset-UserOffset));
951 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
955 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
956 /// unconditionally branches to its only successor.
957 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
958 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
960 MachineBasicBlock *Succ = *MBB->succ_begin();
961 MachineBasicBlock *Pred = *MBB->pred_begin();
962 MachineInstr *PredMI = &Pred->back();
963 if (PredMI->getOpcode() == Mips::BimmX16)
964 return PredMI->getOperand(0).getMBB() == Succ;
969 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
970 unsigned BBNum = BB->getNumber();
971 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
972 // Get the offset and known bits at the end of the layout predecessor.
973 // Include the alignment of the current block.
974 unsigned Offset = BBInfo[i - 1].postOffset();
975 BBInfo[i].Offset = Offset;
979 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
980 /// and instruction CPEMI, and decrement its refcount. If the refcount
981 /// becomes 0 remove the entry and instruction. Returns true if we removed
982 /// the entry, false if we didn't.
984 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
985 MachineInstr *CPEMI) {
986 // Find the old entry. Eliminate it if it is no longer used.
987 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
988 assert(CPE && "Unexpected!");
989 if (--CPE->RefCount == 0) {
990 removeDeadCPEMI(CPEMI);
998 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
999 /// if not, see if an in-range clone of the CPE is in range, and if so,
1000 /// change the data structures so the user references the clone. Returns:
1001 /// 0 = no existing entry found
1002 /// 1 = entry found, and there were no code insertions or deletions
1003 /// 2 = entry found, and there were code insertions or deletions
1004 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1006 MachineInstr *UserMI = U.MI;
1007 MachineInstr *CPEMI = U.CPEMI;
1009 // Check to see if the CPE is already in-range.
1010 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1012 DEBUG(dbgs() << "In range\n");
1016 // No. Look for previously created clones of the CPE that are in range.
1017 unsigned CPI = CPEMI->getOperand(1).getIndex();
1018 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1019 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1020 // We already tried this one
1021 if (CPEs[i].CPEMI == CPEMI)
1023 // Removing CPEs can leave empty entries, skip
1024 if (CPEs[i].CPEMI == NULL)
1026 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1028 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1029 << CPEs[i].CPI << "\n");
1030 // Point the CPUser node to the replacement
1031 U.CPEMI = CPEs[i].CPEMI;
1032 // Change the CPI in the instruction operand to refer to the clone.
1033 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1034 if (UserMI->getOperand(j).isCPI()) {
1035 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1038 // Adjust the refcount of the clone...
1040 // ...and the original. If we didn't remove the old entry, none of the
1041 // addresses changed, so we don't need another pass.
1042 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1048 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1049 /// This version checks if the longer form of the instruction can be used to
1050 /// to satisfy things.
1051 /// if not, see if an in-range clone of the CPE is in range, and if so,
1052 /// change the data structures so the user references the clone. Returns:
1053 /// 0 = no existing entry found
1054 /// 1 = entry found, and there were no code insertions or deletions
1055 /// 2 = entry found, and there were code insertions or deletions
1056 int MipsConstantIslands::findLongFormInRangeCPEntry
1057 (CPUser& U, unsigned UserOffset)
1059 MachineInstr *UserMI = U.MI;
1060 MachineInstr *CPEMI = U.CPEMI;
1062 // Check to see if the CPE is already in-range.
1063 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1064 U.getLongFormMaxDisp(), U.NegOk,
1066 DEBUG(dbgs() << "In range\n");
1067 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1068 return 2; // instruction is longer length now
1071 // No. Look for previously created clones of the CPE that are in range.
1072 unsigned CPI = CPEMI->getOperand(1).getIndex();
1073 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1074 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1075 // We already tried this one
1076 if (CPEs[i].CPEMI == CPEMI)
1078 // Removing CPEs can leave empty entries, skip
1079 if (CPEs[i].CPEMI == NULL)
1081 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1082 U.getLongFormMaxDisp(), U.NegOk)) {
1083 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1084 << CPEs[i].CPI << "\n");
1085 // Point the CPUser node to the replacement
1086 U.CPEMI = CPEs[i].CPEMI;
1087 // Change the CPI in the instruction operand to refer to the clone.
1088 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1089 if (UserMI->getOperand(j).isCPI()) {
1090 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1093 // Adjust the refcount of the clone...
1095 // ...and the original. If we didn't remove the old entry, none of the
1096 // addresses changed, so we don't need another pass.
1097 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1103 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1104 /// the specific unconditional branch instruction.
1105 static inline unsigned getUnconditionalBrDisp(int Opc) {
1108 return ((1<<16)-1)*2;
1112 return ((1<<16)-1)*2;
1115 /// findAvailableWater - Look for an existing entry in the WaterList in which
1116 /// we can place the CPE referenced from U so it's within range of U's MI.
1117 /// Returns true if found, false if not. If it returns true, WaterIter
1118 /// is set to the WaterList entry. For Thumb, prefer water that will not
1119 /// introduce padding to water that will. To ensure that this pass
1120 /// terminates, the CPE location for a particular CPUser is only allowed to
1121 /// move to a lower address, so search backward from the end of the list and
1122 /// prefer the first water that is in range.
1123 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1124 water_iterator &WaterIter) {
1125 if (WaterList.empty())
1128 unsigned BestGrowth = ~0u;
1129 for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();;
1131 MachineBasicBlock* WaterBB = *IP;
1132 // Check if water is in range and is either at a lower address than the
1133 // current "high water mark" or a new water block that was created since
1134 // the previous iteration by inserting an unconditional branch. In the
1135 // latter case, we want to allow resetting the high water mark back to
1136 // this new water since we haven't seen it before. Inserting branches
1137 // should be relatively uncommon and when it does happen, we want to be
1138 // sure to take advantage of it for all the CPEs near that block, so that
1139 // we don't insert more branches than necessary.
1141 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1142 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1143 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1144 // This is the least amount of required padding seen so far.
1145 BestGrowth = Growth;
1147 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1148 << " Growth=" << Growth << '\n');
1150 // Keep looking unless it is perfect.
1151 if (BestGrowth == 0)
1157 return BestGrowth != ~0u;
1160 /// createNewWater - No existing WaterList entry will work for
1161 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1162 /// block is used if in range, and the conditional branch munged so control
1163 /// flow is correct. Otherwise the block is split to create a hole with an
1164 /// unconditional branch around it. In either case NewMBB is set to a
1165 /// block following which the new island can be inserted (the WaterList
1166 /// is not adjusted).
1167 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1168 unsigned UserOffset,
1169 MachineBasicBlock *&NewMBB) {
1170 CPUser &U = CPUsers[CPUserIndex];
1171 MachineInstr *UserMI = U.MI;
1172 MachineInstr *CPEMI = U.CPEMI;
1173 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1174 MachineBasicBlock *UserMBB = UserMI->getParent();
1175 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1177 // If the block does not end in an unconditional branch already, and if the
1178 // end of the block is within range, make new water there. (The addition
1179 // below is for the unconditional branch we will be adding: 4 bytes on ARM +
1180 // Thumb2, 2 on Thumb1.
1181 if (BBHasFallthrough(UserMBB)) {
1182 // Size of branch to insert.
1184 // Compute the offset where the CPE will begin.
1185 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1187 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1188 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1189 << format(", expected CPE offset %#x\n", CPEOffset));
1190 NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
1191 // Add an unconditional branch from UserMBB to fallthrough block. Record
1192 // it for branch lengthening; this new branch will not get out of range,
1193 // but if the preceding conditional branch is out of range, the targets
1194 // will be exchanged, and the altered branch may be out of range, so the
1195 // machinery has to know about it.
1196 int UncondBr = Mips::BimmX16;
1197 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1198 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1199 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1200 MaxDisp, false, UncondBr));
1201 BBInfo[UserMBB->getNumber()].Size += Delta;
1202 adjustBBOffsetsAfter(UserMBB);
1207 // What a big block. Find a place within the block to split it. This is a
1208 // little tricky on Thumb1 since instructions are 2 bytes and constant pool
1209 // entries are 4 bytes: if instruction I references island CPE, and
1210 // instruction I+1 references CPE', it will not work well to put CPE as far
1211 // forward as possible, since then CPE' cannot immediately follow it (that
1212 // location is 2 bytes farther away from I+1 than CPE was from I) and we'd
1213 // need to create a new island. So, we make a first guess, then walk through
1214 // the instructions between the one currently being looked at and the
1215 // possible insertion point, and make sure any other instructions that
1216 // reference CPEs will be able to use the same island area; if not, we back
1217 // up the insertion point.
1219 // Try to split the block so it's fully aligned. Compute the latest split
1220 // point where we can add a 4-byte branch instruction, and then align to
1221 // LogAlign which is the largest possible alignment in the function.
1222 unsigned LogAlign = MF->getAlignment();
1223 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1224 unsigned KnownBits = UserBBI.internalKnownBits();
1225 unsigned UPad = UnknownPadding(LogAlign, KnownBits);
1226 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp() - UPad;
1227 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1230 // The 4 in the following is for the unconditional branch we'll be inserting
1231 // (allows for long branch on Thumb1). Alignment of the island is handled
1232 // inside isOffsetInRange.
1233 BaseInsertOffset -= 4;
1235 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1236 << " la=" << LogAlign
1237 << " kb=" << KnownBits
1238 << " up=" << UPad << '\n');
1240 // This could point off the end of the block if we've already got constant
1241 // pool entries following this block; only the last one is in the water list.
1242 // Back past any possible branches (allow for a conditional and a maximally
1243 // long unconditional).
1244 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1245 BaseInsertOffset = UserBBI.postOffset() - UPad - 8;
1246 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1248 unsigned EndInsertOffset = BaseInsertOffset + 4 + UPad +
1249 CPEMI->getOperand(2).getImm();
1250 MachineBasicBlock::iterator MI = UserMI;
1252 unsigned CPUIndex = CPUserIndex+1;
1253 unsigned NumCPUsers = CPUsers.size();
1254 //MachineInstr *LastIT = 0;
1255 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1256 Offset < BaseInsertOffset;
1257 Offset += TII->GetInstSizeInBytes(MI),
1258 MI = llvm::next(MI)) {
1259 assert(MI != UserMBB->end() && "Fell off end of block");
1260 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1261 CPUser &U = CPUsers[CPUIndex];
1262 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1263 // Shift intertion point by one unit of alignment so it is within reach.
1264 BaseInsertOffset -= 1u << LogAlign;
1265 EndInsertOffset -= 1u << LogAlign;
1267 // This is overly conservative, as we don't account for CPEMIs being
1268 // reused within the block, but it doesn't matter much. Also assume CPEs
1269 // are added in order with alignment padding. We may eventually be able
1270 // to pack the aligned CPEs better.
1271 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1277 NewMBB = splitBlockBeforeInstr(MI);
1280 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1281 /// is out-of-range. If so, pick up the constant pool value and move it some
1282 /// place in-range. Return true if we changed any addresses (thus must run
1283 /// another pass of branch lengthening), false otherwise.
1284 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1285 CPUser &U = CPUsers[CPUserIndex];
1286 MachineInstr *UserMI = U.MI;
1287 MachineInstr *CPEMI = U.CPEMI;
1288 unsigned CPI = CPEMI->getOperand(1).getIndex();
1289 unsigned Size = CPEMI->getOperand(2).getImm();
1290 // Compute this only once, it's expensive.
1291 unsigned UserOffset = getUserOffset(U);
1293 // See if the current entry is within range, or there is a clone of it
1295 int result = findInRangeCPEntry(U, UserOffset);
1296 if (result==1) return false;
1297 else if (result==2) return true;
1300 // Look for water where we can place this CPE.
1301 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1302 MachineBasicBlock *NewMBB;
1304 if (findAvailableWater(U, UserOffset, IP)) {
1305 DEBUG(dbgs() << "Found water in range\n");
1306 MachineBasicBlock *WaterBB = *IP;
1308 // If the original WaterList entry was "new water" on this iteration,
1309 // propagate that to the new island. This is just keeping NewWaterList
1310 // updated to match the WaterList, which will be updated below.
1311 if (NewWaterList.erase(WaterBB))
1312 NewWaterList.insert(NewIsland);
1314 // The new CPE goes before the following block (NewMBB).
1315 NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
1319 // we first see if a longer form of the instrucion could have reached
1320 // the constant. in that case we won't bother to split
1322 result = findLongFormInRangeCPEntry(U, UserOffset);
1324 DEBUG(dbgs() << "No water found\n");
1325 createNewWater(CPUserIndex, UserOffset, NewMBB);
1327 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1328 // called while handling branches so that the water will be seen on the
1329 // next iteration for constant pools, but in this context, we don't want
1330 // it. Check for this so it will be removed from the WaterList.
1331 // Also remove any entry from NewWaterList.
1332 MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
1333 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1334 if (IP != WaterList.end())
1335 NewWaterList.erase(WaterBB);
1337 // We are adding new water. Update NewWaterList.
1338 NewWaterList.insert(NewIsland);
1341 // Remove the original WaterList entry; we want subsequent insertions in
1342 // this vicinity to go after the one we're about to insert. This
1343 // considerably reduces the number of times we have to move the same CPE
1344 // more than once and is also important to ensure the algorithm terminates.
1345 if (IP != WaterList.end())
1346 WaterList.erase(IP);
1348 // Okay, we know we can put an island before NewMBB now, do it!
1349 MF->insert(NewMBB, NewIsland);
1351 // Update internal data structures to account for the newly inserted MBB.
1352 updateForInsertedWaterBlock(NewIsland);
1354 // Decrement the old entry, and remove it if refcount becomes 0.
1355 decrementCPEReferenceCount(CPI, CPEMI);
1357 // Now that we have an island to add the CPE to, clone the original CPE and
1358 // add it to the island.
1359 U.HighWaterMark = NewIsland;
1360 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1361 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1362 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1365 // Mark the basic block as aligned as required by the const-pool entry.
1366 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1368 // Increase the size of the island block to account for the new entry.
1369 BBInfo[NewIsland->getNumber()].Size += Size;
1370 adjustBBOffsetsAfter(llvm::prior(MachineFunction::iterator(NewIsland)));
1372 // No existing clone of this CPE is within range.
1373 // We will be generating a new clone. Get a UID for it.
1374 unsigned ID = createPICLabelUId();
1376 // Finally, change the CPI in the instruction operand to be ID.
1377 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1378 if (UserMI->getOperand(i).isCPI()) {
1379 UserMI->getOperand(i).setIndex(ID);
1383 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1384 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1389 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1390 /// sizes and offsets of impacted basic blocks.
1391 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1392 MachineBasicBlock *CPEBB = CPEMI->getParent();
1393 unsigned Size = CPEMI->getOperand(2).getImm();
1394 CPEMI->eraseFromParent();
1395 BBInfo[CPEBB->getNumber()].Size -= Size;
1396 // All succeeding offsets have the current size value added in, fix this.
1397 if (CPEBB->empty()) {
1398 BBInfo[CPEBB->getNumber()].Size = 0;
1400 // This block no longer needs to be aligned.
1401 CPEBB->setAlignment(0);
1403 // Entries are sorted by descending alignment, so realign from the front.
1404 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1406 adjustBBOffsetsAfter(CPEBB);
1407 // An island has only one predecessor BB and one successor BB. Check if
1408 // this BB's predecessor jumps directly to this BB's successor. This
1409 // shouldn't happen currently.
1410 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1411 // FIXME: remove the empty blocks after all the work is done?
1414 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1416 bool MipsConstantIslands::removeUnusedCPEntries() {
1417 unsigned MadeChange = false;
1418 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1419 std::vector<CPEntry> &CPEs = CPEntries[i];
1420 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1421 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1422 removeDeadCPEMI(CPEs[j].CPEMI);
1423 CPEs[j].CPEMI = NULL;
1431 /// isBBInRange - Returns true if the distance between specific MI and
1432 /// specific BB can fit in MI's displacement field.
1433 bool MipsConstantIslands::isBBInRange
1434 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1438 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1439 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1441 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1442 << " from BB#" << MI->getParent()->getNumber()
1443 << " max delta=" << MaxDisp
1444 << " from " << getOffsetOf(MI) << " to " << DestOffset
1445 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1447 if (BrOffset <= DestOffset) {
1448 // Branch before the Dest.
1449 if (DestOffset-BrOffset <= MaxDisp)
1452 if (BrOffset-DestOffset <= MaxDisp)
1458 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1459 /// away to fit in its displacement field.
1460 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1461 MachineInstr *MI = Br.MI;
1462 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1464 // Check to see if the DestBB is already in-range.
1465 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1469 return fixupUnconditionalBr(Br);
1470 return fixupConditionalBr(Br);
1473 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1474 /// too far away to fit in its displacement field. If the LR register has been
1475 /// spilled in the epilogue, then we can use BL to implement a far jump.
1476 /// Otherwise, add an intermediate branch instruction to a branch.
1478 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1479 MachineInstr *MI = Br.MI;
1480 MachineBasicBlock *MBB = MI->getParent();
1481 // Use BL to implement far jump.
1482 Br.MaxDisp = ((1 << 16)-1) * 2;
1483 MI->setDesc(TII->get(Mips::BimmX16));
1484 BBInfo[MBB->getNumber()].Size += 2;
1485 adjustBBOffsetsAfter(MBB);
1489 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1494 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1495 /// far away to fit in its displacement field. It is converted to an inverse
1496 /// conditional branch + an unconditional branch to the destination.
1498 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1499 MachineInstr *MI = Br.MI;
1500 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1502 // Add an unconditional branch to the destination and invert the branch
1503 // condition to jump over it:
1509 unsigned CCReg = 0; // FIXME
1510 unsigned CC=0; //FIXME
1512 // If the branch is at the end of its MBB and that has a fall-through block,
1513 // direct the updated conditional branch to the fall-through block. Otherwise,
1514 // split the MBB before the next instruction.
1515 MachineBasicBlock *MBB = MI->getParent();
1516 MachineInstr *BMI = &MBB->back();
1517 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1521 if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
1522 BMI->getOpcode() == Br.UncondBr) {
1523 // Last MI in the BB is an unconditional branch. Can we simply invert the
1524 // condition and swap destinations:
1530 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
1531 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1532 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1534 BMI->getOperand(0).setMBB(DestBB);
1535 MI->getOperand(0).setMBB(NewDest);
1542 splitBlockBeforeInstr(MI);
1543 // No need for the branch to the next block. We're adding an unconditional
1544 // branch to the destination.
1545 int delta = TII->GetInstSizeInBytes(&MBB->back());
1546 BBInfo[MBB->getNumber()].Size -= delta;
1547 MBB->back().eraseFromParent();
1548 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1550 MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
1552 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1553 << " also invert condition and change dest. to BB#"
1554 << NextBB->getNumber() << "\n");
1556 // Insert a new conditional branch and a new unconditional branch.
1557 // Also update the ImmBranch as well as adding a new entry for the new branch.
1558 BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode()))
1559 .addMBB(NextBB).addImm(CC).addReg(CCReg);
1560 Br.MI = &MBB->back();
1561 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1562 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1563 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1564 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1565 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1567 // Remove the old conditional branch. It may or may not still be in MBB.
1568 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1569 MI->eraseFromParent();
1570 adjustBBOffsetsAfter(MBB);
1575 void MipsConstantIslands::prescanForConstants() {
1578 PrescannedForConstants = true;
1579 for (MachineFunction::iterator B =
1580 MF->begin(), E = MF->end(); B != E; ++B) {
1581 for (MachineBasicBlock::instr_iterator I =
1582 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1583 switch(I->getDesc().getOpcode()) {
1584 case Mips::LwConstant32: {
1585 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1586 J = I->getNumOperands();
1587 DEBUG(dbgs() << "num operands " << J << "\n");
1588 MachineOperand& Literal = I->getOperand(1);
1589 if (Literal.isImm()) {
1590 int64_t V = Literal.getImm();
1591 DEBUG(dbgs() << "literal " << V << "\n");
1593 Type::getInt32Ty(MF->getFunction()->getContext());
1594 const Constant *C = ConstantInt::get(Int32Ty, V);
1595 unsigned index = MCP->getConstantPoolIndex(C, 4);
1596 I->getOperand(2).ChangeToImmediate(index);
1597 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1598 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1599 I->RemoveOperand(1);
1600 I->RemoveOperand(1);
1601 I->addOperand(MachineOperand::CreateCPI(index, 0));
1602 I->addOperand(MachineOperand::CreateImm(4));