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");
54 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
56 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
58 // FIXME: This option should be removed once it has received sufficient testing.
60 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
61 cl::desc("Align constant islands in code"));
64 // Rather than do make check tests with huge amounts of code, we force
65 // the test to use this amount.
67 static cl::opt<int> ConstantIslandsSmallOffset(
68 "mips-constant-islands-small-offset",
70 cl::desc("Make small offsets be this amount for testing purposes"),
73 /// UnknownPadding - Return the worst case padding that could result from
74 /// unknown offset bits. This does not include alignment padding caused by
75 /// known offset bits.
77 /// @param LogAlign log2(alignment)
78 /// @param KnownBits Number of known low offset bits.
79 static inline unsigned UnknownPadding(unsigned LogAlign, unsigned KnownBits) {
80 if (KnownBits < LogAlign)
81 return (1u << LogAlign) - (1u << KnownBits);
88 typedef MachineBasicBlock::iterator Iter;
89 typedef MachineBasicBlock::reverse_iterator ReverseIter;
91 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
92 /// requires constant pool entries to be scattered among the instructions
93 /// inside a function. To do this, it completely ignores the normal LLVM
94 /// constant pool; instead, it places constants wherever it feels like with
95 /// special instructions.
97 /// The terminology used in this pass includes:
98 /// Islands - Clumps of constants placed in the function.
99 /// Water - Potential places where an island could be formed.
100 /// CPE - A constant pool entry that has been placed somewhere, which
101 /// tracks a list of users.
103 class MipsConstantIslands : public MachineFunctionPass {
105 /// BasicBlockInfo - Information about the offset and size of a single
107 struct BasicBlockInfo {
108 /// Offset - Distance from the beginning of the function to the beginning
109 /// of this basic block.
111 /// Offsets are computed assuming worst case padding before an aligned
112 /// block. This means that subtracting basic block offsets always gives a
113 /// conservative estimate of the real distance which may be smaller.
115 /// Because worst case padding is used, the computed offset of an aligned
116 /// block may not actually be aligned.
119 /// Size - Size of the basic block in bytes. If the block contains
120 /// inline assembly, this is a worst case estimate.
122 /// The size does not include any alignment padding whether from the
123 /// beginning of the block, or from an aligned jump table at the end.
126 /// KnownBits - The number of low bits in Offset that are known to be
127 /// exact. The remaining bits of Offset are an upper bound.
130 /// Unalign - When non-zero, the block contains instructions (inline asm)
131 /// of unknown size. The real size may be smaller than Size bytes by a
132 /// multiple of 1 << Unalign.
135 /// PostAlign - When non-zero, the block terminator contains a .align
136 /// directive, so the end of the block is aligned to 1 << PostAlign
140 BasicBlockInfo() : Offset(0), Size(0), KnownBits(0), Unalign(0),
143 /// Compute the number of known offset bits internally to this block.
144 /// This number should be used to predict worst case padding when
145 /// splitting the block.
146 unsigned internalKnownBits() const {
147 unsigned Bits = Unalign ? Unalign : KnownBits;
148 // If the block size isn't a multiple of the known bits, assume the
149 // worst case padding.
150 if (Size & ((1u << Bits) - 1))
151 Bits = countTrailingZeros(Size);
155 /// Compute the offset immediately following this block. If LogAlign is
156 /// specified, return the offset the successor block will get if it has
158 unsigned postOffset(unsigned LogAlign = 0) const {
159 unsigned PO = Offset + Size;
163 /// Compute the number of known low bits of postOffset. If this block
164 /// contains inline asm, the number of known bits drops to the
165 /// instruction alignment. An aligned terminator may increase the number
167 /// If LogAlign is given, also consider the alignment of the next block.
168 unsigned postKnownBits(unsigned LogAlign = 0) const {
169 return std::max(std::max(unsigned(PostAlign), LogAlign),
170 internalKnownBits());
174 std::vector<BasicBlockInfo> BBInfo;
176 /// WaterList - A sorted list of basic blocks where islands could be placed
177 /// (i.e. blocks that don't fall through to the following block, due
178 /// to a return, unreachable, or unconditional branch).
179 std::vector<MachineBasicBlock*> WaterList;
181 /// NewWaterList - The subset of WaterList that was created since the
182 /// previous iteration by inserting unconditional branches.
183 SmallSet<MachineBasicBlock*, 4> NewWaterList;
185 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
187 /// CPUser - One user of a constant pool, keeping the machine instruction
188 /// pointer, the constant pool being referenced, and the max displacement
189 /// allowed from the instruction to the CP. The HighWaterMark records the
190 /// highest basic block where a new CPEntry can be placed. To ensure this
191 /// pass terminates, the CP entries are initially placed at the end of the
192 /// function and then move monotonically to lower addresses. The
193 /// exception to this rule is when the current CP entry for a particular
194 /// CPUser is out of range, but there is another CP entry for the same
195 /// constant value in range. We want to use the existing in-range CP
196 /// entry, but if it later moves out of range, the search for new water
197 /// should resume where it left off. The HighWaterMark is used to record
202 MachineBasicBlock *HighWaterMark;
205 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
206 // with different displacements
207 unsigned LongFormOpcode;
212 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
213 bool neg, bool soimm, unsigned longformmaxdisp, unsigned longformopcode)
214 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
215 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
216 NegOk(neg), IsSoImm(soimm), KnownAlignment(false) {
217 HighWaterMark = CPEMI->getParent();
219 /// getMaxDisp - Returns the maximum displacement supported by MI.
220 /// Correct for unknown alignment.
221 /// Conservatively subtract 2 bytes to handle weird alignment effects.
222 unsigned getMaxDisp() const {
223 unsigned xMaxDisp = ConstantIslandsSmallOffset? 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), PrescannedForConstants(false){}
306 virtual const char *getPassName() const {
307 return "Mips Constant Islands";
310 bool runOnMachineFunction(MachineFunction &F);
312 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
313 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
314 unsigned getCPELogAlign(const MachineInstr *CPEMI);
315 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
316 unsigned getOffsetOf(MachineInstr *MI) const;
317 unsigned getUserOffset(CPUser&) const;
321 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
322 unsigned Disp, bool NegativeOK, bool IsSoImm = false);
323 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
325 return isOffsetInRange(UserOffset, TrialOffset,
326 U.getMaxDisp(), U.NegOk, U.IsSoImm);
328 bool isLongFormOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
330 return isOffsetInRange(UserOffset, TrialOffset,
331 U.getLongFormMaxDisp(), U.NegOk, U.IsSoImm);
333 void computeBlockSize(MachineBasicBlock *MBB);
334 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
335 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
336 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
337 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
338 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
339 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
340 bool findAvailableWater(CPUser&U, unsigned UserOffset,
341 water_iterator &WaterIter);
342 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
343 MachineBasicBlock *&NewMBB);
344 bool handleConstantPoolUser(unsigned CPUserIndex);
345 void removeDeadCPEMI(MachineInstr *CPEMI);
346 bool removeUnusedCPEntries();
347 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
348 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
349 bool DoDump = false);
350 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
351 CPUser &U, unsigned &Growth);
352 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
353 bool fixupImmediateBr(ImmBranch &Br);
354 bool fixupConditionalBr(ImmBranch &Br);
355 bool fixupUnconditionalBr(ImmBranch &Br);
357 void prescanForConstants();
363 char MipsConstantIslands::ID = 0;
364 } // end of anonymous namespace
366 /// print block size and offset information - debugging
367 void MipsConstantIslands::dumpBBs() {
369 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
370 const BasicBlockInfo &BBI = BBInfo[J];
371 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
372 << " kb=" << unsigned(BBI.KnownBits)
373 << " ua=" << unsigned(BBI.Unalign)
374 << " pa=" << unsigned(BBI.PostAlign)
375 << format(" size=%#x\n", BBInfo[J].Size);
379 /// createMipsLongBranchPass - Returns a pass that converts branches to long
381 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
382 return new MipsConstantIslands(tm);
385 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
386 // The intention is for this to be a mips16 only pass for now
389 MCP = mf.getConstantPool();
390 DEBUG(dbgs() << "constant island machine function " << "\n");
391 if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode() ||
392 !MipsSubtarget::useConstantIslands()) {
395 TII = (const MipsInstrInfo*)MF->getTarget().getInstrInfo();
396 MFI = MF->getInfo<MipsFunctionInfo>();
397 DEBUG(dbgs() << "constant island processing " << "\n");
399 // will need to make predermination if there is any constants we need to
400 // put in constant islands. TBD.
402 if (!PrescannedForConstants) prescanForConstants();
405 // This pass invalidates liveness information when it splits basic blocks.
406 MF->getRegInfo().invalidateLiveness();
408 // Renumber all of the machine basic blocks in the function, guaranteeing that
409 // the numbers agree with the position of the block in the function.
410 MF->RenumberBlocks();
412 bool MadeChange = false;
414 // Perform the initial placement of the constant pool entries. To start with,
415 // we put them all at the end of the function.
416 std::vector<MachineInstr*> CPEMIs;
418 doInitialPlacement(CPEMIs);
420 /// The next UID to take is the first unused one.
421 initPICLabelUId(CPEMIs.size());
423 // Do the initial scan of the function, building up information about the
424 // sizes of each block, the location of all the water, and finding all of the
425 // constant pool users.
426 initializeFunctionInfo(CPEMIs);
430 /// Remove dead constant pool entries.
431 MadeChange |= removeUnusedCPEntries();
433 // Iteratively place constant pool entries and fix up branches until there
435 unsigned NoCPIters = 0, NoBRIters = 0;
437 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
438 bool CPChange = false;
439 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
440 CPChange |= handleConstantPoolUser(i);
441 if (CPChange && ++NoCPIters > 30)
442 report_fatal_error("Constant Island pass failed to converge!");
445 // Clear NewWaterList now. If we split a block for branches, it should
446 // appear as "new water" for the next iteration of constant pool placement.
447 NewWaterList.clear();
449 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
450 bool BRChange = false;
452 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
453 BRChange |= fixupImmediateBr(ImmBranches[i]);
454 if (BRChange && ++NoBRIters > 30)
455 report_fatal_error("Branch Fix Up pass failed to converge!");
458 if (!CPChange && !BRChange)
463 DEBUG(dbgs() << '\n'; dumpBBs());
473 /// doInitialPlacement - Perform the initial placement of the constant pool
474 /// entries. To start with, we put them all at the end of the function.
476 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
477 // Create the basic block to hold the CPE's.
478 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
482 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
483 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
485 // Mark the basic block as required by the const-pool.
486 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
487 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
489 // The function needs to be as aligned as the basic blocks. The linker may
490 // move functions around based on their alignment.
491 MF->ensureAlignment(BB->getAlignment());
493 // Order the entries in BB by descending alignment. That ensures correct
494 // alignment of all entries as long as BB is sufficiently aligned. Keep
495 // track of the insertion point for each alignment. We are going to bucket
496 // sort the entries as they are created.
497 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
499 // Add all of the constants from the constant pool to the end block, use an
500 // identity mapping of CPI's to CPE's.
501 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
503 const DataLayout &TD = *MF->getTarget().getDataLayout();
504 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
505 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
506 assert(Size >= 4 && "Too small constant pool entry");
507 unsigned Align = CPs[i].getAlignment();
508 assert(isPowerOf2_32(Align) && "Invalid alignment");
509 // Verify that all constant pool entries are a multiple of their alignment.
510 // If not, we would have to pad them out so that instructions stay aligned.
511 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
513 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
514 unsigned LogAlign = Log2_32(Align);
515 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
517 MachineInstr *CPEMI =
518 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
519 .addImm(i).addConstantPoolIndex(i).addImm(Size);
521 CPEMIs.push_back(CPEMI);
523 // Ensure that future entries with higher alignment get inserted before
524 // CPEMI. This is bucket sort with iterators.
525 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
526 if (InsPoint[a] == InsAt)
528 // Add a new CPEntry, but no corresponding CPUser yet.
529 std::vector<CPEntry> CPEs;
530 CPEs.push_back(CPEntry(CPEMI, i));
531 CPEntries.push_back(CPEs);
533 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
534 << Size << ", align = " << Align <<'\n');
539 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
540 /// into the block immediately after it.
541 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
542 // Get the next machine basic block in the function.
543 MachineFunction::iterator MBBI = MBB;
544 // Can't fall off end of function.
545 if (llvm::next(MBBI) == MBB->getParent()->end())
548 MachineBasicBlock *NextBB = llvm::next(MBBI);
549 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
550 E = MBB->succ_end(); I != E; ++I)
557 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
558 /// look up the corresponding CPEntry.
559 MipsConstantIslands::CPEntry
560 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
561 const MachineInstr *CPEMI) {
562 std::vector<CPEntry> &CPEs = CPEntries[CPI];
563 // Number of entries per constpool index should be small, just do a
565 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
566 if (CPEs[i].CPEMI == CPEMI)
572 /// getCPELogAlign - Returns the required alignment of the constant pool entry
573 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
574 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
575 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
577 // Everything is 4-byte aligned unless AlignConstantIslands is set.
578 if (!AlignConstantIslands)
581 unsigned CPI = CPEMI->getOperand(1).getIndex();
582 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
583 unsigned Align = MCP->getConstants()[CPI].getAlignment();
584 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
585 return Log2_32(Align);
588 /// initializeFunctionInfo - Do the initial scan of the function, building up
589 /// information about the sizes of each block, the location of all the water,
590 /// and finding all of the constant pool users.
591 void MipsConstantIslands::
592 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
594 BBInfo.resize(MF->getNumBlockIDs());
596 // First thing, compute the size of all basic blocks, and see if the function
597 // has any inline assembly in it. If so, we have to be conservative about
598 // alignment assumptions, as we don't know for sure the size of any
599 // instructions in the inline assembly.
600 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
603 // The known bits of the entry block offset are determined by the function
605 BBInfo.front().KnownBits = MF->getAlignment();
607 // Compute block offsets.
608 adjustBBOffsetsAfter(MF->begin());
610 // Now go back through the instructions and build up our data structures.
611 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
613 MachineBasicBlock &MBB = *MBBI;
615 // If this block doesn't fall through into the next MBB, then this is
616 // 'water' that a constant pool island could be placed.
617 if (!BBHasFallthrough(&MBB))
618 WaterList.push_back(&MBB);
619 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
621 if (I->isDebugValue())
624 int Opc = I->getOpcode();
633 continue; // Ignore other JT branches
636 T2JumpTables.push_back(I);
637 continue; // Does not get an entry in ImmBranches
668 // Record this immediate branch.
669 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
670 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
675 if (Opc == Mips::CONSTPOOL_ENTRY)
679 // Scan the instructions for constant pool operands.
680 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
681 if (I->getOperand(op).isCPI()) {
683 // We found one. The addressing mode tells us the max displacement
684 // from the PC that this instruction permits.
686 // Basic size info comes from the TSFlags field.
690 bool IsSoImm = false;
691 unsigned LongFormBits = 0;
692 unsigned LongFormScale = 0;
693 unsigned LongFormOpcode = 0;
696 llvm_unreachable("Unknown addressing mode for CP reference!");
697 case Mips::LwRxPcTcp16:
700 LongFormOpcode = Mips::LwRxPcTcpX16;
702 case Mips::LwRxPcTcpX16:
707 // Taking the address of a CP entry.
709 // This takes a SoImm, which is 8 bit immediate rotated. We'll
710 // pretend the maximum offset is 255 * 4. Since each instruction
711 // 4 byte wide, this is always correct. We'll check for other
712 // displacements that fits in a SoImm as well.
718 case ARM::t2LEApcrel:
731 Bits = 12; // +-offset_12
737 Scale = 4; // +(offset_8*4)
743 Scale = 4; // +-(offset_8*4)
748 // Remember that this is a user of a CP entry.
749 unsigned CPI = I->getOperand(op).getIndex();
750 MachineInstr *CPEMI = CPEMIs[CPI];
751 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
752 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
753 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, IsSoImm, LongFormMaxOffs,
756 // Increment corresponding CPEntry reference count.
757 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
758 assert(CPE && "Cannot find a corresponding CPEntry!");
761 // Instructions can only use one CP entry, don't bother scanning the
762 // rest of the operands.
772 /// computeBlockSize - Compute the size and some alignment information for MBB.
773 /// This function updates BBInfo directly.
774 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
775 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
780 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
782 BBI.Size += TII->GetInstSizeInBytes(I);
786 /// getOffsetOf - Return the current offset of the specified machine instruction
787 /// from the start of the function. This offset changes as stuff is moved
788 /// around inside the function.
789 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
790 MachineBasicBlock *MBB = MI->getParent();
792 // The offset is composed of two things: the sum of the sizes of all MBB's
793 // before this instruction's block, and the offset from the start of the block
795 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
797 // Sum instructions before MI in MBB.
798 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
799 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
800 Offset += TII->GetInstSizeInBytes(I);
805 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
807 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
808 const MachineBasicBlock *RHS) {
809 return LHS->getNumber() < RHS->getNumber();
812 /// updateForInsertedWaterBlock - When a block is newly inserted into the
813 /// machine function, it upsets all of the block numbers. Renumber the blocks
814 /// and update the arrays that parallel this numbering.
815 void MipsConstantIslands::updateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
816 // Renumber the MBB's to keep them consecutive.
817 NewBB->getParent()->RenumberBlocks(NewBB);
819 // Insert an entry into BBInfo to align it properly with the (newly
820 // renumbered) block numbers.
821 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
823 // Next, update WaterList. Specifically, we need to add NewMBB as having
824 // available water after it.
826 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
828 WaterList.insert(IP, NewBB);
831 /// getUserOffset - Compute the offset of U.MI as seen by the hardware
832 /// displacement computation. Update U.KnownAlignment to match its current
833 /// basic block location.
834 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
835 unsigned UserOffset = getOffsetOf(U.MI);
836 const BasicBlockInfo &BBI = BBInfo[U.MI->getParent()->getNumber()];
837 unsigned KnownBits = BBI.internalKnownBits();
839 // The value read from PC is offset from the actual instruction address.
841 UserOffset += (isThumb ? 4 : 8);
844 // Because of inline assembly, we may not know the alignment (mod 4) of U.MI.
845 // Make sure U.getMaxDisp() returns a constrained range.
846 U.KnownAlignment = (KnownBits >= 2);
848 // On Thumb, offsets==2 mod 4 are rounded down by the hardware for
849 // purposes of the displacement computation; compensate for that here.
850 // For unknown alignments, getMaxDisp() constrains the range instead.
852 if (isThumb && U.KnownAlignment)
859 /// Split the basic block containing MI into two blocks, which are joined by
860 /// an unconditional branch. Update data structures and renumber blocks to
861 /// account for this change and returns the newly created block.
862 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr(MachineInstr *MI) {
863 MachineBasicBlock *OrigBB = MI->getParent();
865 // Create a new MBB for the code after the OrigBB.
866 MachineBasicBlock *NewBB =
867 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
868 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
869 MF->insert(MBBI, NewBB);
871 // Splice the instructions starting with MI over to NewBB.
872 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
874 // Add an unconditional branch from OrigBB to NewBB.
875 // Note the new unconditional branch is not being recorded.
876 // There doesn't seem to be meaningful DebugInfo available; this doesn't
877 // correspond to anything in the source.
878 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::BimmX16)).addMBB(NewBB);
880 unsigned Opc = isThumb ? (isThumb2 ? ARM::t2B : ARM::tB) : ARM::B;
882 BuildMI(OrigBB, DebugLoc(), TII->get(Opc)).addMBB(NewBB);
884 BuildMI(OrigBB, DebugLoc(), TII->get(Opc)).addMBB(NewBB)
885 .addImm(ARMCC::AL).addReg(0);
889 // Update the CFG. All succs of OrigBB are now succs of NewBB.
890 NewBB->transferSuccessors(OrigBB);
892 // OrigBB branches to NewBB.
893 OrigBB->addSuccessor(NewBB);
895 // Update internal data structures to account for the newly inserted MBB.
896 // This is almost the same as updateForInsertedWaterBlock, except that
897 // the Water goes after OrigBB, not NewBB.
898 MF->RenumberBlocks(NewBB);
900 // Insert an entry into BBInfo to align it properly with the (newly
901 // renumbered) block numbers.
902 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
904 // Next, update WaterList. Specifically, we need to add OrigMBB as having
905 // available water after it (but not if it's already there, which happens
906 // when splitting before a conditional branch that is followed by an
907 // unconditional branch - in that case we want to insert NewBB).
909 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
911 MachineBasicBlock* WaterBB = *IP;
912 if (WaterBB == OrigBB)
913 WaterList.insert(llvm::next(IP), NewBB);
915 WaterList.insert(IP, OrigBB);
916 NewWaterList.insert(OrigBB);
918 // Figure out how large the OrigBB is. As the first half of the original
919 // block, it cannot contain a tablejump. The size includes
920 // the new jump we added. (It should be possible to do this without
921 // recounting everything, but it's very confusing, and this is rarely
923 computeBlockSize(OrigBB);
925 // Figure out how large the NewMBB is. As the second half of the original
926 // block, it may contain a tablejump.
927 computeBlockSize(NewBB);
929 // All BBOffsets following these blocks must be modified.
930 adjustBBOffsetsAfter(OrigBB);
938 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
939 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
940 /// constant pool entry).
941 /// UserOffset is computed by getUserOffset above to include PC adjustments. If
942 /// the mod 4 alignment of UserOffset is not known, the uncertainty must be
943 /// subtracted from MaxDisp instead. CPUser::getMaxDisp() does that.
944 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
945 unsigned TrialOffset, unsigned MaxDisp,
946 bool NegativeOK, bool IsSoImm) {
947 if (UserOffset <= TrialOffset) {
948 // User before the Trial.
949 if (TrialOffset - UserOffset <= MaxDisp)
951 // FIXME: Make use full range of soimm values.
952 } else if (NegativeOK) {
953 if (UserOffset - TrialOffset <= MaxDisp)
955 // FIXME: Make use full range of soimm values.
960 /// isWaterInRange - Returns true if a CPE placed after the specified
961 /// Water (a basic block) will be in range for the specific MI.
963 /// Compute how much the function will grow by inserting a CPE after Water.
964 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
965 MachineBasicBlock* Water, CPUser &U,
967 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
968 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
969 unsigned NextBlockOffset, NextBlockAlignment;
970 MachineFunction::const_iterator NextBlock = Water;
971 if (++NextBlock == MF->end()) {
972 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
973 NextBlockAlignment = 0;
975 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
976 NextBlockAlignment = NextBlock->getAlignment();
978 unsigned Size = U.CPEMI->getOperand(2).getImm();
979 unsigned CPEEnd = CPEOffset + Size;
981 // The CPE may be able to hide in the alignment padding before the next
982 // block. It may also cause more padding to be required if it is more aligned
983 // that the next block.
984 if (CPEEnd > NextBlockOffset) {
985 Growth = CPEEnd - NextBlockOffset;
986 // Compute the padding that would go at the end of the CPE to align the next
988 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
990 // If the CPE is to be inserted before the instruction, that will raise
991 // the offset of the instruction. Also account for unknown alignment padding
992 // in blocks between CPE and the user.
993 if (CPEOffset < UserOffset)
994 UserOffset += Growth + UnknownPadding(MF->getAlignment(), CPELogAlign);
996 // CPE fits in existing padding.
999 return isOffsetInRange(UserOffset, CPEOffset, U);
1002 /// isCPEntryInRange - Returns true if the distance between specific MI and
1003 /// specific ConstPool entry instruction can fit in MI's displacement field.
1004 bool MipsConstantIslands::isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
1005 MachineInstr *CPEMI, unsigned MaxDisp,
1006 bool NegOk, bool DoDump) {
1007 unsigned CPEOffset = getOffsetOf(CPEMI);
1011 unsigned Block = MI->getParent()->getNumber();
1012 const BasicBlockInfo &BBI = BBInfo[Block];
1013 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
1014 << " max delta=" << MaxDisp
1015 << format(" insn address=%#x", UserOffset)
1016 << " in BB#" << Block << ": "
1017 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
1018 << format("CPE address=%#x offset=%+d: ", CPEOffset,
1019 int(CPEOffset-UserOffset));
1023 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
1026 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
1027 /// unconditionally branches to its only successor.
1028 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
1029 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
1033 MachineBasicBlock *Succ = *MBB->succ_begin();
1034 MachineBasicBlock *Pred = *MBB->pred_begin();
1035 MachineInstr *PredMI = &Pred->back();
1036 if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB
1037 || PredMI->getOpcode() == ARM::t2B)
1038 return PredMI->getOperand(0).getMBB() == Succ;
1044 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
1045 unsigned BBNum = BB->getNumber();
1046 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
1047 // Get the offset and known bits at the end of the layout predecessor.
1048 // Include the alignment of the current block.
1049 unsigned Offset = BBInfo[i - 1].postOffset();
1050 BBInfo[i].Offset = Offset;
1054 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
1055 /// and instruction CPEMI, and decrement its refcount. If the refcount
1056 /// becomes 0 remove the entry and instruction. Returns true if we removed
1057 /// the entry, false if we didn't.
1059 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
1060 MachineInstr *CPEMI) {
1061 // Find the old entry. Eliminate it if it is no longer used.
1062 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
1063 assert(CPE && "Unexpected!");
1064 if (--CPE->RefCount == 0) {
1065 removeDeadCPEMI(CPEMI);
1073 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1074 /// if not, see if an in-range clone of the CPE is in range, and if so,
1075 /// change the data structures so the user references the clone. Returns:
1076 /// 0 = no existing entry found
1077 /// 1 = entry found, and there were no code insertions or deletions
1078 /// 2 = entry found, and there were code insertions or deletions
1079 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1081 MachineInstr *UserMI = U.MI;
1082 MachineInstr *CPEMI = U.CPEMI;
1084 // Check to see if the CPE is already in-range.
1085 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1087 DEBUG(dbgs() << "In range\n");
1091 // No. Look for previously created clones of the CPE that are in range.
1092 unsigned CPI = CPEMI->getOperand(1).getIndex();
1093 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1094 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1095 // We already tried this one
1096 if (CPEs[i].CPEMI == CPEMI)
1098 // Removing CPEs can leave empty entries, skip
1099 if (CPEs[i].CPEMI == NULL)
1101 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1103 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1104 << CPEs[i].CPI << "\n");
1105 // Point the CPUser node to the replacement
1106 U.CPEMI = CPEs[i].CPEMI;
1107 // Change the CPI in the instruction operand to refer to the clone.
1108 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1109 if (UserMI->getOperand(j).isCPI()) {
1110 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1113 // Adjust the refcount of the clone...
1115 // ...and the original. If we didn't remove the old entry, none of the
1116 // addresses changed, so we don't need another pass.
1117 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1123 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1124 /// This version checks if the longer form of the instruction can be used to
1125 /// to satisfy things.
1126 /// if not, see if an in-range clone of the CPE is in range, and if so,
1127 /// change the data structures so the user references the clone. Returns:
1128 /// 0 = no existing entry found
1129 /// 1 = entry found, and there were no code insertions or deletions
1130 /// 2 = entry found, and there were code insertions or deletions
1131 int MipsConstantIslands::findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset)
1133 MachineInstr *UserMI = U.MI;
1134 MachineInstr *CPEMI = U.CPEMI;
1136 // Check to see if the CPE is already in-range.
1137 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getLongFormMaxDisp(), U.NegOk,
1139 DEBUG(dbgs() << "In range\n");
1140 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1141 return 2; // instruction is longer length now
1144 // No. Look for previously created clones of the CPE that are in range.
1145 unsigned CPI = CPEMI->getOperand(1).getIndex();
1146 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1147 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1148 // We already tried this one
1149 if (CPEs[i].CPEMI == CPEMI)
1151 // Removing CPEs can leave empty entries, skip
1152 if (CPEs[i].CPEMI == NULL)
1154 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getLongFormMaxDisp(),
1156 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1157 << CPEs[i].CPI << "\n");
1158 // Point the CPUser node to the replacement
1159 U.CPEMI = CPEs[i].CPEMI;
1160 // Change the CPI in the instruction operand to refer to the clone.
1161 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1162 if (UserMI->getOperand(j).isCPI()) {
1163 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1166 // Adjust the refcount of the clone...
1168 // ...and the original. If we didn't remove the old entry, none of the
1169 // addresses changed, so we don't need another pass.
1170 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1176 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1177 /// the specific unconditional branch instruction.
1178 static inline unsigned getUnconditionalBrDisp(int Opc) {
1182 return ((1<<10)-1)*2;
1184 return ((1<<23)-1)*2;
1189 return ((1<<23)-1)*4;
1192 /// findAvailableWater - Look for an existing entry in the WaterList in which
1193 /// we can place the CPE referenced from U so it's within range of U's MI.
1194 /// Returns true if found, false if not. If it returns true, WaterIter
1195 /// is set to the WaterList entry. For Thumb, prefer water that will not
1196 /// introduce padding to water that will. To ensure that this pass
1197 /// terminates, the CPE location for a particular CPUser is only allowed to
1198 /// move to a lower address, so search backward from the end of the list and
1199 /// prefer the first water that is in range.
1200 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1201 water_iterator &WaterIter) {
1202 if (WaterList.empty())
1205 unsigned BestGrowth = ~0u;
1206 for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();;
1208 MachineBasicBlock* WaterBB = *IP;
1209 // Check if water is in range and is either at a lower address than the
1210 // current "high water mark" or a new water block that was created since
1211 // the previous iteration by inserting an unconditional branch. In the
1212 // latter case, we want to allow resetting the high water mark back to
1213 // this new water since we haven't seen it before. Inserting branches
1214 // should be relatively uncommon and when it does happen, we want to be
1215 // sure to take advantage of it for all the CPEs near that block, so that
1216 // we don't insert more branches than necessary.
1218 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1219 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1220 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1221 // This is the least amount of required padding seen so far.
1222 BestGrowth = Growth;
1224 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1225 << " Growth=" << Growth << '\n');
1227 // Keep looking unless it is perfect.
1228 if (BestGrowth == 0)
1234 return BestGrowth != ~0u;
1237 /// createNewWater - No existing WaterList entry will work for
1238 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1239 /// block is used if in range, and the conditional branch munged so control
1240 /// flow is correct. Otherwise the block is split to create a hole with an
1241 /// unconditional branch around it. In either case NewMBB is set to a
1242 /// block following which the new island can be inserted (the WaterList
1243 /// is not adjusted).
1244 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1245 unsigned UserOffset,
1246 MachineBasicBlock *&NewMBB) {
1247 CPUser &U = CPUsers[CPUserIndex];
1248 MachineInstr *UserMI = U.MI;
1249 MachineInstr *CPEMI = U.CPEMI;
1250 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1251 MachineBasicBlock *UserMBB = UserMI->getParent();
1252 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1254 // If the block does not end in an unconditional branch already, and if the
1255 // end of the block is within range, make new water there. (The addition
1256 // below is for the unconditional branch we will be adding: 4 bytes on ARM +
1257 // Thumb2, 2 on Thumb1.
1258 if (BBHasFallthrough(UserMBB)) {
1259 // Size of branch to insert.
1261 unsigned Delta = isThumb1 ? 2 : 4;
1265 // Compute the offset where the CPE will begin.
1266 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1268 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1269 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1270 << format(", expected CPE offset %#x\n", CPEOffset));
1271 NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
1272 // Add an unconditional branch from UserMBB to fallthrough block. Record
1273 // it for branch lengthening; this new branch will not get out of range,
1274 // but if the preceding conditional branch is out of range, the targets
1275 // will be exchanged, and the altered branch may be out of range, so the
1276 // machinery has to know about it.
1278 int UncondBr = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B;
1280 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1282 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB)
1283 .addImm(ARMCC::AL).addReg(0);
1287 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1288 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1289 MaxDisp, false, UncondBr));
1290 BBInfo[UserMBB->getNumber()].Size += Delta;
1291 adjustBBOffsetsAfter(UserMBB);
1296 // What a big block. Find a place within the block to split it. This is a
1297 // little tricky on Thumb1 since instructions are 2 bytes and constant pool
1298 // entries are 4 bytes: if instruction I references island CPE, and
1299 // instruction I+1 references CPE', it will not work well to put CPE as far
1300 // forward as possible, since then CPE' cannot immediately follow it (that
1301 // location is 2 bytes farther away from I+1 than CPE was from I) and we'd
1302 // need to create a new island. So, we make a first guess, then walk through
1303 // the instructions between the one currently being looked at and the
1304 // possible insertion point, and make sure any other instructions that
1305 // reference CPEs will be able to use the same island area; if not, we back
1306 // up the insertion point.
1308 // Try to split the block so it's fully aligned. Compute the latest split
1309 // point where we can add a 4-byte branch instruction, and then align to
1310 // LogAlign which is the largest possible alignment in the function.
1311 unsigned LogAlign = MF->getAlignment();
1312 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1313 unsigned KnownBits = UserBBI.internalKnownBits();
1314 unsigned UPad = UnknownPadding(LogAlign, KnownBits);
1315 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp() - UPad;
1316 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1319 // The 4 in the following is for the unconditional branch we'll be inserting
1320 // (allows for long branch on Thumb1). Alignment of the island is handled
1321 // inside isOffsetInRange.
1322 BaseInsertOffset -= 4;
1324 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1325 << " la=" << LogAlign
1326 << " kb=" << KnownBits
1327 << " up=" << UPad << '\n');
1329 // This could point off the end of the block if we've already got constant
1330 // pool entries following this block; only the last one is in the water list.
1331 // Back past any possible branches (allow for a conditional and a maximally
1332 // long unconditional).
1333 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1334 BaseInsertOffset = UserBBI.postOffset() - UPad - 8;
1335 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1337 unsigned EndInsertOffset = BaseInsertOffset + 4 + UPad +
1338 CPEMI->getOperand(2).getImm();
1339 MachineBasicBlock::iterator MI = UserMI;
1341 unsigned CPUIndex = CPUserIndex+1;
1342 unsigned NumCPUsers = CPUsers.size();
1343 MachineInstr *LastIT = 0;
1344 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1345 Offset < BaseInsertOffset;
1346 Offset += TII->GetInstSizeInBytes(MI),
1347 MI = llvm::next(MI)) {
1348 assert(MI != UserMBB->end() && "Fell off end of block");
1349 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1350 CPUser &U = CPUsers[CPUIndex];
1351 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1352 // Shift intertion point by one unit of alignment so it is within reach.
1353 BaseInsertOffset -= 1u << LogAlign;
1354 EndInsertOffset -= 1u << LogAlign;
1356 // This is overly conservative, as we don't account for CPEMIs being
1357 // reused within the block, but it doesn't matter much. Also assume CPEs
1358 // are added in order with alignment padding. We may eventually be able
1359 // to pack the aligned CPEs better.
1360 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1364 // Remember the last IT instruction.
1365 if (MI->getOpcode() == ARM::t2IT)
1372 // Avoid splitting an IT block.
1375 unsigned PredReg = 0;
1376 ARMCC::CondCodes CC = getITInstrPredicate(MI, PredReg);
1377 if (CC != ARMCC::AL)
1381 NewMBB = splitBlockBeforeInstr(MI);
1384 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1385 /// is out-of-range. If so, pick up the constant pool value and move it some
1386 /// place in-range. Return true if we changed any addresses (thus must run
1387 /// another pass of branch lengthening), false otherwise.
1388 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1389 CPUser &U = CPUsers[CPUserIndex];
1390 MachineInstr *UserMI = U.MI;
1391 MachineInstr *CPEMI = U.CPEMI;
1392 unsigned CPI = CPEMI->getOperand(1).getIndex();
1393 unsigned Size = CPEMI->getOperand(2).getImm();
1394 // Compute this only once, it's expensive.
1395 unsigned UserOffset = getUserOffset(U);
1397 // See if the current entry is within range, or there is a clone of it
1399 int result = findInRangeCPEntry(U, UserOffset);
1400 if (result==1) return false;
1401 else if (result==2) return true;
1404 // Look for water where we can place this CPE.
1405 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1406 MachineBasicBlock *NewMBB;
1408 if (findAvailableWater(U, UserOffset, IP)) {
1409 DEBUG(dbgs() << "Found water in range\n");
1410 MachineBasicBlock *WaterBB = *IP;
1412 // If the original WaterList entry was "new water" on this iteration,
1413 // propagate that to the new island. This is just keeping NewWaterList
1414 // updated to match the WaterList, which will be updated below.
1415 if (NewWaterList.erase(WaterBB))
1416 NewWaterList.insert(NewIsland);
1418 // The new CPE goes before the following block (NewMBB).
1419 NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
1423 // we first see if a longer form of the instrucion could have reached the constant.
1424 // in that case we won't bother to split
1426 result = findLongFormInRangeCPEntry(U, UserOffset);
1428 DEBUG(dbgs() << "No water found\n");
1429 createNewWater(CPUserIndex, UserOffset, NewMBB);
1431 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1432 // called while handling branches so that the water will be seen on the
1433 // next iteration for constant pools, but in this context, we don't want
1434 // it. Check for this so it will be removed from the WaterList.
1435 // Also remove any entry from NewWaterList.
1436 MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
1437 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1438 if (IP != WaterList.end())
1439 NewWaterList.erase(WaterBB);
1441 // We are adding new water. Update NewWaterList.
1442 NewWaterList.insert(NewIsland);
1445 // Remove the original WaterList entry; we want subsequent insertions in
1446 // this vicinity to go after the one we're about to insert. This
1447 // considerably reduces the number of times we have to move the same CPE
1448 // more than once and is also important to ensure the algorithm terminates.
1449 if (IP != WaterList.end())
1450 WaterList.erase(IP);
1452 // Okay, we know we can put an island before NewMBB now, do it!
1453 MF->insert(NewMBB, NewIsland);
1455 // Update internal data structures to account for the newly inserted MBB.
1456 updateForInsertedWaterBlock(NewIsland);
1458 // Decrement the old entry, and remove it if refcount becomes 0.
1459 decrementCPEReferenceCount(CPI, CPEMI);
1461 // Now that we have an island to add the CPE to, clone the original CPE and
1462 // add it to the island.
1463 U.HighWaterMark = NewIsland;
1464 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1465 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1466 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1469 // Mark the basic block as aligned as required by the const-pool entry.
1470 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1472 // Increase the size of the island block to account for the new entry.
1473 BBInfo[NewIsland->getNumber()].Size += Size;
1474 adjustBBOffsetsAfter(llvm::prior(MachineFunction::iterator(NewIsland)));
1476 // No existing clone of this CPE is within range.
1477 // We will be generating a new clone. Get a UID for it.
1478 unsigned ID = createPICLabelUId();
1480 // Finally, change the CPI in the instruction operand to be ID.
1481 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1482 if (UserMI->getOperand(i).isCPI()) {
1483 UserMI->getOperand(i).setIndex(ID);
1487 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1488 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1493 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1494 /// sizes and offsets of impacted basic blocks.
1495 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1496 MachineBasicBlock *CPEBB = CPEMI->getParent();
1497 unsigned Size = CPEMI->getOperand(2).getImm();
1498 CPEMI->eraseFromParent();
1499 BBInfo[CPEBB->getNumber()].Size -= Size;
1500 // All succeeding offsets have the current size value added in, fix this.
1501 if (CPEBB->empty()) {
1502 BBInfo[CPEBB->getNumber()].Size = 0;
1504 // This block no longer needs to be aligned.
1505 CPEBB->setAlignment(0);
1507 // Entries are sorted by descending alignment, so realign from the front.
1508 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1510 adjustBBOffsetsAfter(CPEBB);
1511 // An island has only one predecessor BB and one successor BB. Check if
1512 // this BB's predecessor jumps directly to this BB's successor. This
1513 // shouldn't happen currently.
1514 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1515 // FIXME: remove the empty blocks after all the work is done?
1518 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1520 bool MipsConstantIslands::removeUnusedCPEntries() {
1521 unsigned MadeChange = false;
1522 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1523 std::vector<CPEntry> &CPEs = CPEntries[i];
1524 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1525 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1526 removeDeadCPEMI(CPEs[j].CPEMI);
1527 CPEs[j].CPEMI = NULL;
1535 /// isBBInRange - Returns true if the distance between specific MI and
1536 /// specific BB can fit in MI's displacement field.
1537 bool MipsConstantIslands::isBBInRange(MachineInstr *MI,MachineBasicBlock *DestBB,
1540 unsigned PCAdj = isThumb ? 4 : 8;
1544 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1545 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1547 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1548 << " from BB#" << MI->getParent()->getNumber()
1549 << " max delta=" << MaxDisp
1550 << " from " << getOffsetOf(MI) << " to " << DestOffset
1551 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1553 if (BrOffset <= DestOffset) {
1554 // Branch before the Dest.
1555 if (DestOffset-BrOffset <= MaxDisp)
1558 if (BrOffset-DestOffset <= MaxDisp)
1564 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1565 /// away to fit in its displacement field.
1566 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1567 MachineInstr *MI = Br.MI;
1568 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1570 // Check to see if the DestBB is already in-range.
1571 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1575 return fixupUnconditionalBr(Br);
1576 return fixupConditionalBr(Br);
1579 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1580 /// too far away to fit in its displacement field. If the LR register has been
1581 /// spilled in the epilogue, then we can use BL to implement a far jump.
1582 /// Otherwise, add an intermediate branch instruction to a branch.
1584 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1585 MachineInstr *MI = Br.MI;
1586 MachineBasicBlock *MBB = MI->getParent();
1589 llvm_unreachable("fixupUnconditionalBr is Thumb1 only!");
1591 // Use BL to implement far jump.
1592 Br.MaxDisp = (1 << 21) * 2;
1594 MI->setDesc(TII->get(ARM::tBfar));
1596 BBInfo[MBB->getNumber()].Size += 2;
1597 adjustBBOffsetsAfter(MBB);
1601 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1606 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1607 /// far away to fit in its displacement field. It is converted to an inverse
1608 /// conditional branch + an unconditional branch to the destination.
1610 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1612 MachineInstr *MI = Br.MI;
1613 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1615 // Add an unconditional branch to the destination and invert the branch
1616 // condition to jump over it:
1622 ARMCC::CondCodes CC = (ARMCC::CondCodes)MI->getOperand(1).getImm();
1623 CC = ARMCC::getOppositeCondition(CC);
1624 unsigned CCReg = MI->getOperand(2).getReg();
1626 // If the branch is at the end of its MBB and that has a fall-through block,
1627 // direct the updated conditional branch to the fall-through block. Otherwise,
1628 // split the MBB before the next instruction.
1629 MachineBasicBlock *MBB = MI->getParent();
1630 MachineInstr *BMI = &MBB->back();
1631 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1635 if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
1636 BMI->getOpcode() == Br.UncondBr) {
1637 // Last MI in the BB is an unconditional branch. Can we simply invert the
1638 // condition and swap destinations:
1644 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
1645 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1646 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1648 BMI->getOperand(0).setMBB(DestBB);
1649 MI->getOperand(0).setMBB(NewDest);
1650 MI->getOperand(1).setImm(CC);
1657 splitBlockBeforeInstr(MI);
1658 // No need for the branch to the next block. We're adding an unconditional
1659 // branch to the destination.
1660 int delta = TII->GetInstSizeInBytes(&MBB->back());
1661 BBInfo[MBB->getNumber()].Size -= delta;
1662 MBB->back().eraseFromParent();
1663 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1665 MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
1667 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1668 << " also invert condition and change dest. to BB#"
1669 << NextBB->getNumber() << "\n");
1671 // Insert a new conditional branch and a new unconditional branch.
1672 // Also update the ImmBranch as well as adding a new entry for the new branch.
1673 BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode()))
1674 .addMBB(NextBB).addImm(CC).addReg(CCReg);
1675 Br.MI = &MBB->back();
1676 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1678 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB)
1679 .addImm(ARMCC::AL).addReg(0);
1681 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1682 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1683 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1684 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1686 // Remove the old conditional branch. It may or may not still be in MBB.
1687 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1688 MI->eraseFromParent();
1689 adjustBBOffsetsAfter(MBB);
1695 void MipsConstantIslands::prescanForConstants() {
1697 PrescannedForConstants = true;
1698 for (MachineFunction::iterator B =
1699 MF->begin(), E = MF->end(); B != E; ++B) {
1700 for (MachineBasicBlock::instr_iterator I =
1701 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1702 switch(I->getDesc().getOpcode()) {
1703 case Mips::LwConstant32: {
1704 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1705 J = I->getNumOperands();
1706 DEBUG(dbgs() << "num operands " << J << "\n");
1707 MachineOperand& Literal = I->getOperand(1);
1708 if (Literal.isImm()) {
1709 int64_t V = Literal.getImm();
1710 DEBUG(dbgs() << "literal " << V << "\n");
1712 Type::getInt32Ty(MF->getFunction()->getContext());
1713 const Constant *C = ConstantInt::get(Int32Ty, V);
1714 unsigned index = MCP->getConstantPoolIndex(C, 4);
1715 I->getOperand(2).ChangeToImmediate(index);
1716 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1717 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1718 I->RemoveOperand(1);
1719 I->RemoveOperand(1);
1720 I->addOperand(MachineOperand::CreateCPI(index, 0));
1721 I->addOperand(MachineOperand::CreateImm(4));