1 //===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 // This pass is used to make Pc relative loads of constants.
12 // For now, only Mips16 will use this.
14 // Loading constants inline is expensive on Mips16 and it's in general better
15 // to place the constant nearby in code space and then it can be loaded with a
16 // simple 16 bit load instruction.
18 // The constants can be not just numbers but addresses of functions and labels.
19 // This can be particularly helpful in static relocation mode for embedded
24 #define DEBUG_TYPE "mips-constant-islands"
27 #include "MCTargetDesc/MipsBaseInfo.h"
28 #include "Mips16InstrInfo.h"
29 #include "MipsMachineFunction.h"
30 #include "MipsTargetMachine.h"
31 #include "llvm/ADT/Statistic.h"
32 #include "llvm/CodeGen/MachineBasicBlock.h"
33 #include "llvm/CodeGen/MachineFunctionPass.h"
34 #include "llvm/CodeGen/MachineInstrBuilder.h"
35 #include "llvm/CodeGen/MachineRegisterInfo.h"
36 #include "llvm/IR/Function.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/Format.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"
50 STATISTIC(NumCPEs, "Number of constpool entries");
51 STATISTIC(NumSplit, "Number of uncond branches inserted");
52 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
53 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
55 // FIXME: This option should be removed once it has received sufficient testing.
57 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
58 cl::desc("Align constant islands in code"));
61 // Rather than do make check tests with huge amounts of code, we force
62 // the test to use this amount.
64 static cl::opt<int> ConstantIslandsSmallOffset(
65 "mips-constant-islands-small-offset",
67 cl::desc("Make small offsets be this amount for testing purposes"),
71 // For testing purposes we tell it to not use relaxed load forms so that it
74 static cl::opt<bool> NoLoadRelaxation(
75 "mips-constant-islands-no-load-relaxation",
77 cl::desc("Don't relax loads to long loads - for testing purposes"),
80 static unsigned int branchTargetOperand(MachineInstr *MI) {
81 switch (MI->getOpcode()) {
90 case Mips::BeqzRxImm16:
91 case Mips::BeqzRxImmX16:
92 case Mips::BnezRxImm16:
93 case Mips::BnezRxImmX16:
96 llvm_unreachable("Unknown branch type");
99 static bool isUnconditionalBranch(unsigned int Opcode) {
101 default: return false;
109 static unsigned int longformBranchOpcode(unsigned int Opcode) {
113 return Mips::BimmX16;
116 return Mips::BteqzX16;
119 return Mips::BtnezX16;
122 case Mips::BeqzRxImm16:
123 case Mips::BeqzRxImmX16:
124 return Mips::BeqzRxImmX16;
125 case Mips::BnezRxImm16:
126 case Mips::BnezRxImmX16:
127 return Mips::BnezRxImmX16;
129 llvm_unreachable("Unknown branch type");
133 // FIXME: need to go through this whole constant islands port and check the math
134 // for branch ranges and clean this up and make some functions to calculate things
135 // that are done many times identically.
136 // Need to refactor some of the code to call this routine.
138 static unsigned int branchMaxOffsets(unsigned int Opcode) {
139 unsigned Bits, Scale;
149 case Mips::BeqzRxImm16:
153 case Mips::BeqzRxImmX16:
157 case Mips::BnezRxImm16:
161 case Mips::BnezRxImmX16:
182 llvm_unreachable("Unknown branch type");
184 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
191 typedef MachineBasicBlock::iterator Iter;
192 typedef MachineBasicBlock::reverse_iterator ReverseIter;
194 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
195 /// requires constant pool entries to be scattered among the instructions
196 /// inside a function. To do this, it completely ignores the normal LLVM
197 /// constant pool; instead, it places constants wherever it feels like with
198 /// special instructions.
200 /// The terminology used in this pass includes:
201 /// Islands - Clumps of constants placed in the function.
202 /// Water - Potential places where an island could be formed.
203 /// CPE - A constant pool entry that has been placed somewhere, which
204 /// tracks a list of users.
206 class MipsConstantIslands : public MachineFunctionPass {
208 /// BasicBlockInfo - Information about the offset and size of a single
210 struct BasicBlockInfo {
211 /// Offset - Distance from the beginning of the function to the beginning
212 /// of this basic block.
214 /// Offsets are computed assuming worst case padding before an aligned
215 /// block. This means that subtracting basic block offsets always gives a
216 /// conservative estimate of the real distance which may be smaller.
218 /// Because worst case padding is used, the computed offset of an aligned
219 /// block may not actually be aligned.
222 /// Size - Size of the basic block in bytes. If the block contains
223 /// inline assembly, this is a worst case estimate.
225 /// The size does not include any alignment padding whether from the
226 /// beginning of the block, or from an aligned jump table at the end.
229 // FIXME: ignore LogAlign for this patch
231 unsigned postOffset(unsigned LogAlign = 0) const {
232 unsigned PO = Offset + Size;
236 BasicBlockInfo() : Offset(0), Size(0) {}
240 std::vector<BasicBlockInfo> BBInfo;
242 /// WaterList - A sorted list of basic blocks where islands could be placed
243 /// (i.e. blocks that don't fall through to the following block, due
244 /// to a return, unreachable, or unconditional branch).
245 std::vector<MachineBasicBlock*> WaterList;
247 /// NewWaterList - The subset of WaterList that was created since the
248 /// previous iteration by inserting unconditional branches.
249 SmallSet<MachineBasicBlock*, 4> NewWaterList;
251 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
253 /// CPUser - One user of a constant pool, keeping the machine instruction
254 /// pointer, the constant pool being referenced, and the max displacement
255 /// allowed from the instruction to the CP. The HighWaterMark records the
256 /// highest basic block where a new CPEntry can be placed. To ensure this
257 /// pass terminates, the CP entries are initially placed at the end of the
258 /// function and then move monotonically to lower addresses. The
259 /// exception to this rule is when the current CP entry for a particular
260 /// CPUser is out of range, but there is another CP entry for the same
261 /// constant value in range. We want to use the existing in-range CP
262 /// entry, but if it later moves out of range, the search for new water
263 /// should resume where it left off. The HighWaterMark is used to record
268 MachineBasicBlock *HighWaterMark;
271 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
272 // with different displacements
273 unsigned LongFormOpcode;
276 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
278 unsigned longformmaxdisp, unsigned longformopcode)
279 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
280 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
282 HighWaterMark = CPEMI->getParent();
284 /// getMaxDisp - Returns the maximum displacement supported by MI.
285 unsigned getMaxDisp() const {
286 unsigned xMaxDisp = ConstantIslandsSmallOffset?
287 ConstantIslandsSmallOffset: MaxDisp;
290 void setMaxDisp(unsigned val) {
293 unsigned getLongFormMaxDisp() const {
294 return LongFormMaxDisp;
296 unsigned getLongFormOpcode() const {
297 return LongFormOpcode;
301 /// CPUsers - Keep track of all of the machine instructions that use various
302 /// constant pools and their max displacement.
303 std::vector<CPUser> CPUsers;
305 /// CPEntry - One per constant pool entry, keeping the machine instruction
306 /// pointer, the constpool index, and the number of CPUser's which
307 /// reference this entry.
312 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
313 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
316 /// CPEntries - Keep track of all of the constant pool entry machine
317 /// instructions. For each original constpool index (i.e. those that
318 /// existed upon entry to this pass), it keeps a vector of entries.
319 /// Original elements are cloned as we go along; the clones are
320 /// put in the vector of the original element, but have distinct CPIs.
321 std::vector<std::vector<CPEntry> > CPEntries;
323 /// ImmBranch - One per immediate branch, keeping the machine instruction
324 /// pointer, conditional or unconditional, the max displacement,
325 /// and (if isCond is true) the corresponding unconditional branch
329 unsigned MaxDisp : 31;
332 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
333 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
336 /// ImmBranches - Keep track of all the immediate branch instructions.
338 std::vector<ImmBranch> ImmBranches;
340 /// HasFarJump - True if any far jump instruction has been emitted during
341 /// the branch fix up pass.
344 const TargetMachine &TM;
347 const MipsSubtarget *STI;
348 const Mips16InstrInfo *TII;
349 MipsFunctionInfo *MFI;
351 MachineConstantPool *MCP;
353 unsigned PICLabelUId;
354 bool PrescannedForConstants;
356 void initPICLabelUId(unsigned UId) {
361 unsigned createPICLabelUId() {
362 return PICLabelUId++;
367 MipsConstantIslands(TargetMachine &tm)
368 : MachineFunctionPass(ID), TM(tm),
369 IsPIC(TM.getRelocationModel() == Reloc::PIC_),
370 ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
371 STI(&TM.getSubtarget<MipsSubtarget>()), MF(0), MCP(0),
372 PrescannedForConstants(false){}
374 virtual const char *getPassName() const {
375 return "Mips Constant Islands";
378 bool runOnMachineFunction(MachineFunction &F);
380 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
381 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
382 unsigned getCPELogAlign(const MachineInstr *CPEMI);
383 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
384 unsigned getOffsetOf(MachineInstr *MI) const;
385 unsigned getUserOffset(CPUser&) const;
389 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
390 unsigned Disp, bool NegativeOK);
391 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
394 bool isLongFormOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
397 void computeBlockSize(MachineBasicBlock *MBB);
398 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
399 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
400 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
401 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
402 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
403 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
404 bool findAvailableWater(CPUser&U, unsigned UserOffset,
405 water_iterator &WaterIter);
406 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
407 MachineBasicBlock *&NewMBB);
408 bool handleConstantPoolUser(unsigned CPUserIndex);
409 void removeDeadCPEMI(MachineInstr *CPEMI);
410 bool removeUnusedCPEntries();
411 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
412 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
413 bool DoDump = false);
414 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
415 CPUser &U, unsigned &Growth);
416 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
417 bool fixupImmediateBr(ImmBranch &Br);
418 bool fixupConditionalBr(ImmBranch &Br);
419 bool fixupUnconditionalBr(ImmBranch &Br);
421 void prescanForConstants();
427 char MipsConstantIslands::ID = 0;
428 } // end of anonymous namespace
431 bool MipsConstantIslands::isLongFormOffsetInRange
432 (unsigned UserOffset, unsigned TrialOffset,
434 return isOffsetInRange(UserOffset, TrialOffset,
435 U.getLongFormMaxDisp(), U.NegOk);
438 bool MipsConstantIslands::isOffsetInRange
439 (unsigned UserOffset, unsigned TrialOffset,
441 return isOffsetInRange(UserOffset, TrialOffset,
442 U.getMaxDisp(), U.NegOk);
444 /// print block size and offset information - debugging
445 void MipsConstantIslands::dumpBBs() {
447 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
448 const BasicBlockInfo &BBI = BBInfo[J];
449 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
450 << format(" size=%#x\n", BBInfo[J].Size);
454 /// createMipsLongBranchPass - Returns a pass that converts branches to long
456 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
457 return new MipsConstantIslands(tm);
460 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
461 // The intention is for this to be a mips16 only pass for now
464 MCP = mf.getConstantPool();
465 DEBUG(dbgs() << "constant island machine function " << "\n");
466 if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode() ||
467 !MipsSubtarget::useConstantIslands()) {
470 TII = (const Mips16InstrInfo*)MF->getTarget().getInstrInfo();
471 MFI = MF->getInfo<MipsFunctionInfo>();
472 DEBUG(dbgs() << "constant island processing " << "\n");
474 // will need to make predermination if there is any constants we need to
475 // put in constant islands. TBD.
477 if (!PrescannedForConstants) prescanForConstants();
480 // This pass invalidates liveness information when it splits basic blocks.
481 MF->getRegInfo().invalidateLiveness();
483 // Renumber all of the machine basic blocks in the function, guaranteeing that
484 // the numbers agree with the position of the block in the function.
485 MF->RenumberBlocks();
487 bool MadeChange = false;
489 // Perform the initial placement of the constant pool entries. To start with,
490 // we put them all at the end of the function.
491 std::vector<MachineInstr*> CPEMIs;
493 doInitialPlacement(CPEMIs);
495 /// The next UID to take is the first unused one.
496 initPICLabelUId(CPEMIs.size());
498 // Do the initial scan of the function, building up information about the
499 // sizes of each block, the location of all the water, and finding all of the
500 // constant pool users.
501 initializeFunctionInfo(CPEMIs);
505 /// Remove dead constant pool entries.
506 MadeChange |= removeUnusedCPEntries();
508 // Iteratively place constant pool entries and fix up branches until there
510 unsigned NoCPIters = 0, NoBRIters = 0;
513 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
514 bool CPChange = false;
515 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
516 CPChange |= handleConstantPoolUser(i);
517 if (CPChange && ++NoCPIters > 30)
518 report_fatal_error("Constant Island pass failed to converge!");
521 // Clear NewWaterList now. If we split a block for branches, it should
522 // appear as "new water" for the next iteration of constant pool placement.
523 NewWaterList.clear();
525 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
526 bool BRChange = false;
527 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
528 BRChange |= fixupImmediateBr(ImmBranches[i]);
529 if (BRChange && ++NoBRIters > 30)
530 report_fatal_error("Branch Fix Up pass failed to converge!");
532 if (!CPChange && !BRChange)
537 DEBUG(dbgs() << '\n'; dumpBBs());
547 /// doInitialPlacement - Perform the initial placement of the constant pool
548 /// entries. To start with, we put them all at the end of the function.
550 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
551 // Create the basic block to hold the CPE's.
552 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
556 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
557 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
559 // Mark the basic block as required by the const-pool.
560 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
561 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
563 // The function needs to be as aligned as the basic blocks. The linker may
564 // move functions around based on their alignment.
565 MF->ensureAlignment(BB->getAlignment());
567 // Order the entries in BB by descending alignment. That ensures correct
568 // alignment of all entries as long as BB is sufficiently aligned. Keep
569 // track of the insertion point for each alignment. We are going to bucket
570 // sort the entries as they are created.
571 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
573 // Add all of the constants from the constant pool to the end block, use an
574 // identity mapping of CPI's to CPE's.
575 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
577 const DataLayout &TD = *MF->getTarget().getDataLayout();
578 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
579 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
580 assert(Size >= 4 && "Too small constant pool entry");
581 unsigned Align = CPs[i].getAlignment();
582 assert(isPowerOf2_32(Align) && "Invalid alignment");
583 // Verify that all constant pool entries are a multiple of their alignment.
584 // If not, we would have to pad them out so that instructions stay aligned.
585 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
587 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
588 unsigned LogAlign = Log2_32(Align);
589 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
591 MachineInstr *CPEMI =
592 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
593 .addImm(i).addConstantPoolIndex(i).addImm(Size);
595 CPEMIs.push_back(CPEMI);
597 // Ensure that future entries with higher alignment get inserted before
598 // CPEMI. This is bucket sort with iterators.
599 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
600 if (InsPoint[a] == InsAt)
602 // Add a new CPEntry, but no corresponding CPUser yet.
603 std::vector<CPEntry> CPEs;
604 CPEs.push_back(CPEntry(CPEMI, i));
605 CPEntries.push_back(CPEs);
607 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
608 << Size << ", align = " << Align <<'\n');
613 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
614 /// into the block immediately after it.
615 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
616 // Get the next machine basic block in the function.
617 MachineFunction::iterator MBBI = MBB;
618 // Can't fall off end of function.
619 if (std::next(MBBI) == MBB->getParent()->end())
622 MachineBasicBlock *NextBB = std::next(MBBI);
623 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
624 E = MBB->succ_end(); I != E; ++I)
631 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
632 /// look up the corresponding CPEntry.
633 MipsConstantIslands::CPEntry
634 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
635 const MachineInstr *CPEMI) {
636 std::vector<CPEntry> &CPEs = CPEntries[CPI];
637 // Number of entries per constpool index should be small, just do a
639 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
640 if (CPEs[i].CPEMI == CPEMI)
646 /// getCPELogAlign - Returns the required alignment of the constant pool entry
647 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
648 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
649 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
651 // Everything is 4-byte aligned unless AlignConstantIslands is set.
652 if (!AlignConstantIslands)
655 unsigned CPI = CPEMI->getOperand(1).getIndex();
656 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
657 unsigned Align = MCP->getConstants()[CPI].getAlignment();
658 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
659 return Log2_32(Align);
662 /// initializeFunctionInfo - Do the initial scan of the function, building up
663 /// information about the sizes of each block, the location of all the water,
664 /// and finding all of the constant pool users.
665 void MipsConstantIslands::
666 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
668 BBInfo.resize(MF->getNumBlockIDs());
670 // First thing, compute the size of all basic blocks, and see if the function
671 // has any inline assembly in it. If so, we have to be conservative about
672 // alignment assumptions, as we don't know for sure the size of any
673 // instructions in the inline assembly.
674 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
678 // Compute block offsets.
679 adjustBBOffsetsAfter(MF->begin());
681 // Now go back through the instructions and build up our data structures.
682 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
684 MachineBasicBlock &MBB = *MBBI;
686 // If this block doesn't fall through into the next MBB, then this is
687 // 'water' that a constant pool island could be placed.
688 if (!BBHasFallthrough(&MBB))
689 WaterList.push_back(&MBB);
690 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
692 if (I->isDebugValue())
695 int Opc = I->getOpcode();
703 continue; // Ignore other branches for now
714 case Mips::BeqzRxImm16:
720 case Mips::BeqzRxImmX16:
726 case Mips::BnezRxImm16:
732 case Mips::BnezRxImmX16:
763 // Record this immediate branch.
764 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
765 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
768 if (Opc == Mips::CONSTPOOL_ENTRY)
772 // Scan the instructions for constant pool operands.
773 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
774 if (I->getOperand(op).isCPI()) {
776 // We found one. The addressing mode tells us the max displacement
777 // from the PC that this instruction permits.
779 // Basic size info comes from the TSFlags field.
783 unsigned LongFormBits = 0;
784 unsigned LongFormScale = 0;
785 unsigned LongFormOpcode = 0;
788 llvm_unreachable("Unknown addressing mode for CP reference!");
789 case Mips::LwRxPcTcp16:
792 LongFormOpcode = Mips::LwRxPcTcpX16;
796 case Mips::LwRxPcTcpX16:
802 // Remember that this is a user of a CP entry.
803 unsigned CPI = I->getOperand(op).getIndex();
804 MachineInstr *CPEMI = CPEMIs[CPI];
805 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
806 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
807 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
808 LongFormMaxOffs, LongFormOpcode));
810 // Increment corresponding CPEntry reference count.
811 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
812 assert(CPE && "Cannot find a corresponding CPEntry!");
815 // Instructions can only use one CP entry, don't bother scanning the
816 // rest of the operands.
826 /// computeBlockSize - Compute the size and some alignment information for MBB.
827 /// This function updates BBInfo directly.
828 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
829 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
832 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
834 BBI.Size += TII->GetInstSizeInBytes(I);
838 /// getOffsetOf - Return the current offset of the specified machine instruction
839 /// from the start of the function. This offset changes as stuff is moved
840 /// around inside the function.
841 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
842 MachineBasicBlock *MBB = MI->getParent();
844 // The offset is composed of two things: the sum of the sizes of all MBB's
845 // before this instruction's block, and the offset from the start of the block
847 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
849 // Sum instructions before MI in MBB.
850 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
851 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
852 Offset += TII->GetInstSizeInBytes(I);
857 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
859 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
860 const MachineBasicBlock *RHS) {
861 return LHS->getNumber() < RHS->getNumber();
864 /// updateForInsertedWaterBlock - When a block is newly inserted into the
865 /// machine function, it upsets all of the block numbers. Renumber the blocks
866 /// and update the arrays that parallel this numbering.
867 void MipsConstantIslands::updateForInsertedWaterBlock
868 (MachineBasicBlock *NewBB) {
869 // Renumber the MBB's to keep them consecutive.
870 NewBB->getParent()->RenumberBlocks(NewBB);
872 // Insert an entry into BBInfo to align it properly with the (newly
873 // renumbered) block numbers.
874 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
876 // Next, update WaterList. Specifically, we need to add NewMBB as having
877 // available water after it.
879 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
881 WaterList.insert(IP, NewBB);
884 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
885 return getOffsetOf(U.MI);
888 /// Split the basic block containing MI into two blocks, which are joined by
889 /// an unconditional branch. Update data structures and renumber blocks to
890 /// account for this change and returns the newly created block.
891 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
893 MachineBasicBlock *OrigBB = MI->getParent();
895 // Create a new MBB for the code after the OrigBB.
896 MachineBasicBlock *NewBB =
897 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
898 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
899 MF->insert(MBBI, NewBB);
901 // Splice the instructions starting with MI over to NewBB.
902 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
904 // Add an unconditional branch from OrigBB to NewBB.
905 // Note the new unconditional branch is not being recorded.
906 // There doesn't seem to be meaningful DebugInfo available; this doesn't
907 // correspond to anything in the source.
908 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
911 // Update the CFG. All succs of OrigBB are now succs of NewBB.
912 NewBB->transferSuccessors(OrigBB);
914 // OrigBB branches to NewBB.
915 OrigBB->addSuccessor(NewBB);
917 // Update internal data structures to account for the newly inserted MBB.
918 // This is almost the same as updateForInsertedWaterBlock, except that
919 // the Water goes after OrigBB, not NewBB.
920 MF->RenumberBlocks(NewBB);
922 // Insert an entry into BBInfo to align it properly with the (newly
923 // renumbered) block numbers.
924 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
926 // Next, update WaterList. Specifically, we need to add OrigMBB as having
927 // available water after it (but not if it's already there, which happens
928 // when splitting before a conditional branch that is followed by an
929 // unconditional branch - in that case we want to insert NewBB).
931 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
933 MachineBasicBlock* WaterBB = *IP;
934 if (WaterBB == OrigBB)
935 WaterList.insert(std::next(IP), NewBB);
937 WaterList.insert(IP, OrigBB);
938 NewWaterList.insert(OrigBB);
940 // Figure out how large the OrigBB is. As the first half of the original
941 // block, it cannot contain a tablejump. The size includes
942 // the new jump we added. (It should be possible to do this without
943 // recounting everything, but it's very confusing, and this is rarely
945 computeBlockSize(OrigBB);
947 // Figure out how large the NewMBB is. As the second half of the original
948 // block, it may contain a tablejump.
949 computeBlockSize(NewBB);
951 // All BBOffsets following these blocks must be modified.
952 adjustBBOffsetsAfter(OrigBB);
959 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
960 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
961 /// constant pool entry).
962 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
963 unsigned TrialOffset, unsigned MaxDisp,
965 if (UserOffset <= TrialOffset) {
966 // User before the Trial.
967 if (TrialOffset - UserOffset <= MaxDisp)
969 } else if (NegativeOK) {
970 if (UserOffset - TrialOffset <= MaxDisp)
976 /// isWaterInRange - Returns true if a CPE placed after the specified
977 /// Water (a basic block) will be in range for the specific MI.
979 /// Compute how much the function will grow by inserting a CPE after Water.
980 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
981 MachineBasicBlock* Water, CPUser &U,
983 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
984 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
985 unsigned NextBlockOffset, NextBlockAlignment;
986 MachineFunction::const_iterator NextBlock = Water;
987 if (++NextBlock == MF->end()) {
988 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
989 NextBlockAlignment = 0;
991 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
992 NextBlockAlignment = NextBlock->getAlignment();
994 unsigned Size = U.CPEMI->getOperand(2).getImm();
995 unsigned CPEEnd = CPEOffset + Size;
997 // The CPE may be able to hide in the alignment padding before the next
998 // block. It may also cause more padding to be required if it is more aligned
999 // that the next block.
1000 if (CPEEnd > NextBlockOffset) {
1001 Growth = CPEEnd - NextBlockOffset;
1002 // Compute the padding that would go at the end of the CPE to align the next
1004 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
1006 // If the CPE is to be inserted before the instruction, that will raise
1007 // the offset of the instruction. Also account for unknown alignment padding
1008 // in blocks between CPE and the user.
1009 if (CPEOffset < UserOffset)
1010 UserOffset += Growth;
1012 // CPE fits in existing padding.
1015 return isOffsetInRange(UserOffset, CPEOffset, U);
1018 /// isCPEntryInRange - Returns true if the distance between specific MI and
1019 /// specific ConstPool entry instruction can fit in MI's displacement field.
1020 bool MipsConstantIslands::isCPEntryInRange
1021 (MachineInstr *MI, unsigned UserOffset,
1022 MachineInstr *CPEMI, unsigned MaxDisp,
1023 bool NegOk, bool DoDump) {
1024 unsigned CPEOffset = getOffsetOf(CPEMI);
1028 unsigned Block = MI->getParent()->getNumber();
1029 const BasicBlockInfo &BBI = BBInfo[Block];
1030 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
1031 << " max delta=" << MaxDisp
1032 << format(" insn address=%#x", UserOffset)
1033 << " in BB#" << Block << ": "
1034 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
1035 << format("CPE address=%#x offset=%+d: ", CPEOffset,
1036 int(CPEOffset-UserOffset));
1040 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
1044 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
1045 /// unconditionally branches to its only successor.
1046 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
1047 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
1049 MachineBasicBlock *Succ = *MBB->succ_begin();
1050 MachineBasicBlock *Pred = *MBB->pred_begin();
1051 MachineInstr *PredMI = &Pred->back();
1052 if (PredMI->getOpcode() == Mips::Bimm16)
1053 return PredMI->getOperand(0).getMBB() == Succ;
1058 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
1059 unsigned BBNum = BB->getNumber();
1060 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
1061 // Get the offset and known bits at the end of the layout predecessor.
1062 // Include the alignment of the current block.
1063 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
1064 BBInfo[i].Offset = Offset;
1068 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
1069 /// and instruction CPEMI, and decrement its refcount. If the refcount
1070 /// becomes 0 remove the entry and instruction. Returns true if we removed
1071 /// the entry, false if we didn't.
1073 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
1074 MachineInstr *CPEMI) {
1075 // Find the old entry. Eliminate it if it is no longer used.
1076 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
1077 assert(CPE && "Unexpected!");
1078 if (--CPE->RefCount == 0) {
1079 removeDeadCPEMI(CPEMI);
1087 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1088 /// if not, see if an in-range clone of the CPE is in range, and if so,
1089 /// change the data structures so the user references the clone. Returns:
1090 /// 0 = no existing entry found
1091 /// 1 = entry found, and there were no code insertions or deletions
1092 /// 2 = entry found, and there were code insertions or deletions
1093 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1095 MachineInstr *UserMI = U.MI;
1096 MachineInstr *CPEMI = U.CPEMI;
1098 // Check to see if the CPE is already in-range.
1099 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1101 DEBUG(dbgs() << "In range\n");
1105 // No. Look for previously created clones of the CPE that are in range.
1106 unsigned CPI = CPEMI->getOperand(1).getIndex();
1107 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1108 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1109 // We already tried this one
1110 if (CPEs[i].CPEMI == CPEMI)
1112 // Removing CPEs can leave empty entries, skip
1113 if (CPEs[i].CPEMI == NULL)
1115 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1117 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1118 << CPEs[i].CPI << "\n");
1119 // Point the CPUser node to the replacement
1120 U.CPEMI = CPEs[i].CPEMI;
1121 // Change the CPI in the instruction operand to refer to the clone.
1122 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1123 if (UserMI->getOperand(j).isCPI()) {
1124 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1127 // Adjust the refcount of the clone...
1129 // ...and the original. If we didn't remove the old entry, none of the
1130 // addresses changed, so we don't need another pass.
1131 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1137 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1138 /// This version checks if the longer form of the instruction can be used to
1139 /// to satisfy things.
1140 /// if not, see if an in-range clone of the CPE is in range, and if so,
1141 /// change the data structures so the user references the clone. Returns:
1142 /// 0 = no existing entry found
1143 /// 1 = entry found, and there were no code insertions or deletions
1144 /// 2 = entry found, and there were code insertions or deletions
1145 int MipsConstantIslands::findLongFormInRangeCPEntry
1146 (CPUser& U, unsigned UserOffset)
1148 MachineInstr *UserMI = U.MI;
1149 MachineInstr *CPEMI = U.CPEMI;
1151 // Check to see if the CPE is already in-range.
1152 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1153 U.getLongFormMaxDisp(), U.NegOk,
1155 DEBUG(dbgs() << "In range\n");
1156 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1157 U.setMaxDisp(U.getLongFormMaxDisp());
1158 return 2; // instruction is longer length now
1161 // No. Look for previously created clones of the CPE that are in range.
1162 unsigned CPI = CPEMI->getOperand(1).getIndex();
1163 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1164 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1165 // We already tried this one
1166 if (CPEs[i].CPEMI == CPEMI)
1168 // Removing CPEs can leave empty entries, skip
1169 if (CPEs[i].CPEMI == NULL)
1171 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1172 U.getLongFormMaxDisp(), U.NegOk)) {
1173 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1174 << CPEs[i].CPI << "\n");
1175 // Point the CPUser node to the replacement
1176 U.CPEMI = CPEs[i].CPEMI;
1177 // Change the CPI in the instruction operand to refer to the clone.
1178 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1179 if (UserMI->getOperand(j).isCPI()) {
1180 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1183 // Adjust the refcount of the clone...
1185 // ...and the original. If we didn't remove the old entry, none of the
1186 // addresses changed, so we don't need another pass.
1187 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1193 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1194 /// the specific unconditional branch instruction.
1195 static inline unsigned getUnconditionalBrDisp(int Opc) {
1198 return ((1<<10)-1)*2;
1200 return ((1<<16)-1)*2;
1204 return ((1<<16)-1)*2;
1207 /// findAvailableWater - Look for an existing entry in the WaterList in which
1208 /// we can place the CPE referenced from U so it's within range of U's MI.
1209 /// Returns true if found, false if not. If it returns true, WaterIter
1210 /// is set to the WaterList entry.
1211 /// To ensure that this pass
1212 /// terminates, the CPE location for a particular CPUser is only allowed to
1213 /// move to a lower address, so search backward from the end of the list and
1214 /// prefer the first water that is in range.
1215 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1216 water_iterator &WaterIter) {
1217 if (WaterList.empty())
1220 unsigned BestGrowth = ~0u;
1221 for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();;
1223 MachineBasicBlock* WaterBB = *IP;
1224 // Check if water is in range and is either at a lower address than the
1225 // current "high water mark" or a new water block that was created since
1226 // the previous iteration by inserting an unconditional branch. In the
1227 // latter case, we want to allow resetting the high water mark back to
1228 // this new water since we haven't seen it before. Inserting branches
1229 // should be relatively uncommon and when it does happen, we want to be
1230 // sure to take advantage of it for all the CPEs near that block, so that
1231 // we don't insert more branches than necessary.
1233 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1234 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1235 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1236 // This is the least amount of required padding seen so far.
1237 BestGrowth = Growth;
1239 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1240 << " Growth=" << Growth << '\n');
1242 // Keep looking unless it is perfect.
1243 if (BestGrowth == 0)
1249 return BestGrowth != ~0u;
1252 /// createNewWater - No existing WaterList entry will work for
1253 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1254 /// block is used if in range, and the conditional branch munged so control
1255 /// flow is correct. Otherwise the block is split to create a hole with an
1256 /// unconditional branch around it. In either case NewMBB is set to a
1257 /// block following which the new island can be inserted (the WaterList
1258 /// is not adjusted).
1259 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1260 unsigned UserOffset,
1261 MachineBasicBlock *&NewMBB) {
1262 CPUser &U = CPUsers[CPUserIndex];
1263 MachineInstr *UserMI = U.MI;
1264 MachineInstr *CPEMI = U.CPEMI;
1265 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1266 MachineBasicBlock *UserMBB = UserMI->getParent();
1267 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1269 // If the block does not end in an unconditional branch already, and if the
1270 // end of the block is within range, make new water there.
1271 if (BBHasFallthrough(UserMBB)) {
1272 // Size of branch to insert.
1274 // Compute the offset where the CPE will begin.
1275 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1277 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1278 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1279 << format(", expected CPE offset %#x\n", CPEOffset));
1280 NewMBB = std::next(MachineFunction::iterator(UserMBB));
1281 // Add an unconditional branch from UserMBB to fallthrough block. Record
1282 // it for branch lengthening; this new branch will not get out of range,
1283 // but if the preceding conditional branch is out of range, the targets
1284 // will be exchanged, and the altered branch may be out of range, so the
1285 // machinery has to know about it.
1286 int UncondBr = Mips::Bimm16;
1287 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1288 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1289 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1290 MaxDisp, false, UncondBr));
1291 BBInfo[UserMBB->getNumber()].Size += Delta;
1292 adjustBBOffsetsAfter(UserMBB);
1297 // What a big block. Find a place within the block to split it.
1299 // Try to split the block so it's fully aligned. Compute the latest split
1300 // point where we can add a 4-byte branch instruction, and then align to
1301 // LogAlign which is the largest possible alignment in the function.
1302 unsigned LogAlign = MF->getAlignment();
1303 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1304 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1305 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1308 // The 4 in the following is for the unconditional branch we'll be inserting
1309 // Alignment of the island is handled
1310 // inside isOffsetInRange.
1311 BaseInsertOffset -= 4;
1313 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1314 << " la=" << LogAlign << '\n');
1316 // This could point off the end of the block if we've already got constant
1317 // pool entries following this block; only the last one is in the water list.
1318 // Back past any possible branches (allow for a conditional and a maximally
1319 // long unconditional).
1320 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1321 BaseInsertOffset = UserBBI.postOffset() - 8;
1322 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1324 unsigned EndInsertOffset = BaseInsertOffset + 4 +
1325 CPEMI->getOperand(2).getImm();
1326 MachineBasicBlock::iterator MI = UserMI;
1328 unsigned CPUIndex = CPUserIndex+1;
1329 unsigned NumCPUsers = CPUsers.size();
1330 //MachineInstr *LastIT = 0;
1331 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1332 Offset < BaseInsertOffset;
1333 Offset += TII->GetInstSizeInBytes(MI), MI = std::next(MI)) {
1334 assert(MI != UserMBB->end() && "Fell off end of block");
1335 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1336 CPUser &U = CPUsers[CPUIndex];
1337 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1338 // Shift intertion point by one unit of alignment so it is within reach.
1339 BaseInsertOffset -= 1u << LogAlign;
1340 EndInsertOffset -= 1u << LogAlign;
1342 // This is overly conservative, as we don't account for CPEMIs being
1343 // reused within the block, but it doesn't matter much. Also assume CPEs
1344 // are added in order with alignment padding. We may eventually be able
1345 // to pack the aligned CPEs better.
1346 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1352 NewMBB = splitBlockBeforeInstr(MI);
1355 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1356 /// is out-of-range. If so, pick up the constant pool value and move it some
1357 /// place in-range. Return true if we changed any addresses (thus must run
1358 /// another pass of branch lengthening), false otherwise.
1359 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1360 CPUser &U = CPUsers[CPUserIndex];
1361 MachineInstr *UserMI = U.MI;
1362 MachineInstr *CPEMI = U.CPEMI;
1363 unsigned CPI = CPEMI->getOperand(1).getIndex();
1364 unsigned Size = CPEMI->getOperand(2).getImm();
1365 // Compute this only once, it's expensive.
1366 unsigned UserOffset = getUserOffset(U);
1368 // See if the current entry is within range, or there is a clone of it
1370 int result = findInRangeCPEntry(U, UserOffset);
1371 if (result==1) return false;
1372 else if (result==2) return true;
1375 // Look for water where we can place this CPE.
1376 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1377 MachineBasicBlock *NewMBB;
1379 if (findAvailableWater(U, UserOffset, IP)) {
1380 DEBUG(dbgs() << "Found water in range\n");
1381 MachineBasicBlock *WaterBB = *IP;
1383 // If the original WaterList entry was "new water" on this iteration,
1384 // propagate that to the new island. This is just keeping NewWaterList
1385 // updated to match the WaterList, which will be updated below.
1386 if (NewWaterList.erase(WaterBB))
1387 NewWaterList.insert(NewIsland);
1389 // The new CPE goes before the following block (NewMBB).
1390 NewMBB = std::next(MachineFunction::iterator(WaterBB));
1394 // we first see if a longer form of the instrucion could have reached
1395 // the constant. in that case we won't bother to split
1396 if (!NoLoadRelaxation) {
1397 result = findLongFormInRangeCPEntry(U, UserOffset);
1398 if (result != 0) return true;
1400 DEBUG(dbgs() << "No water found\n");
1401 createNewWater(CPUserIndex, UserOffset, NewMBB);
1403 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1404 // called while handling branches so that the water will be seen on the
1405 // next iteration for constant pools, but in this context, we don't want
1406 // it. Check for this so it will be removed from the WaterList.
1407 // Also remove any entry from NewWaterList.
1408 MachineBasicBlock *WaterBB = std::prev(MachineFunction::iterator(NewMBB));
1409 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1410 if (IP != WaterList.end())
1411 NewWaterList.erase(WaterBB);
1413 // We are adding new water. Update NewWaterList.
1414 NewWaterList.insert(NewIsland);
1417 // Remove the original WaterList entry; we want subsequent insertions in
1418 // this vicinity to go after the one we're about to insert. This
1419 // considerably reduces the number of times we have to move the same CPE
1420 // more than once and is also important to ensure the algorithm terminates.
1421 if (IP != WaterList.end())
1422 WaterList.erase(IP);
1424 // Okay, we know we can put an island before NewMBB now, do it!
1425 MF->insert(NewMBB, NewIsland);
1427 // Update internal data structures to account for the newly inserted MBB.
1428 updateForInsertedWaterBlock(NewIsland);
1430 // Decrement the old entry, and remove it if refcount becomes 0.
1431 decrementCPEReferenceCount(CPI, CPEMI);
1433 // No existing clone of this CPE is within range.
1434 // We will be generating a new clone. Get a UID for it.
1435 unsigned ID = createPICLabelUId();
1437 // Now that we have an island to add the CPE to, clone the original CPE and
1438 // add it to the island.
1439 U.HighWaterMark = NewIsland;
1440 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1441 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1442 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1445 // Mark the basic block as aligned as required by the const-pool entry.
1446 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1448 // Increase the size of the island block to account for the new entry.
1449 BBInfo[NewIsland->getNumber()].Size += Size;
1450 adjustBBOffsetsAfter(std::prev(MachineFunction::iterator(NewIsland)));
1454 // Finally, change the CPI in the instruction operand to be ID.
1455 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1456 if (UserMI->getOperand(i).isCPI()) {
1457 UserMI->getOperand(i).setIndex(ID);
1461 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1462 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1467 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1468 /// sizes and offsets of impacted basic blocks.
1469 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1470 MachineBasicBlock *CPEBB = CPEMI->getParent();
1471 unsigned Size = CPEMI->getOperand(2).getImm();
1472 CPEMI->eraseFromParent();
1473 BBInfo[CPEBB->getNumber()].Size -= Size;
1474 // All succeeding offsets have the current size value added in, fix this.
1475 if (CPEBB->empty()) {
1476 BBInfo[CPEBB->getNumber()].Size = 0;
1478 // This block no longer needs to be aligned.
1479 CPEBB->setAlignment(0);
1481 // Entries are sorted by descending alignment, so realign from the front.
1482 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1484 adjustBBOffsetsAfter(CPEBB);
1485 // An island has only one predecessor BB and one successor BB. Check if
1486 // this BB's predecessor jumps directly to this BB's successor. This
1487 // shouldn't happen currently.
1488 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1489 // FIXME: remove the empty blocks after all the work is done?
1492 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1494 bool MipsConstantIslands::removeUnusedCPEntries() {
1495 unsigned MadeChange = false;
1496 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1497 std::vector<CPEntry> &CPEs = CPEntries[i];
1498 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1499 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1500 removeDeadCPEMI(CPEs[j].CPEMI);
1501 CPEs[j].CPEMI = NULL;
1509 /// isBBInRange - Returns true if the distance between specific MI and
1510 /// specific BB can fit in MI's displacement field.
1511 bool MipsConstantIslands::isBBInRange
1512 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1516 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1517 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1519 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1520 << " from BB#" << MI->getParent()->getNumber()
1521 << " max delta=" << MaxDisp
1522 << " from " << getOffsetOf(MI) << " to " << DestOffset
1523 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1525 if (BrOffset <= DestOffset) {
1526 // Branch before the Dest.
1527 if (DestOffset-BrOffset <= MaxDisp)
1530 if (BrOffset-DestOffset <= MaxDisp)
1536 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1537 /// away to fit in its displacement field.
1538 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1539 MachineInstr *MI = Br.MI;
1540 unsigned TargetOperand = branchTargetOperand(MI);
1541 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1543 // Check to see if the DestBB is already in-range.
1544 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1548 return fixupUnconditionalBr(Br);
1549 return fixupConditionalBr(Br);
1552 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1553 /// too far away to fit in its displacement field. If the LR register has been
1554 /// spilled in the epilogue, then we can use BL to implement a far jump.
1555 /// Otherwise, add an intermediate branch instruction to a branch.
1557 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1558 MachineInstr *MI = Br.MI;
1559 MachineBasicBlock *MBB = MI->getParent();
1560 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1561 // Use BL to implement far jump.
1562 unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2;
1563 if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) {
1564 Br.MaxDisp = BimmX16MaxDisp;
1565 MI->setDesc(TII->get(Mips::BimmX16));
1568 // need to give the math a more careful look here
1569 // this is really a segment address and not
1570 // a PC relative address. FIXME. But I think that
1571 // just reducing the bits by 1 as I've done is correct.
1572 // The basic block we are branching too much be longword aligned.
1573 // we know that RA is saved because we always save it right now.
1574 // this requirement will be relaxed later but we also have an alternate
1575 // way to implement this that I will implement that does not need jal.
1576 // We should have a way to back out this alignment restriction if we "can" later.
1577 // but it is not harmful.
1579 DestBB->setAlignment(2);
1580 Br.MaxDisp = ((1<<24)-1) * 2;
1581 MI->setDesc(TII->get(Mips::JalB16));
1583 BBInfo[MBB->getNumber()].Size += 2;
1584 adjustBBOffsetsAfter(MBB);
1588 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1594 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1595 /// far away to fit in its displacement field. It is converted to an inverse
1596 /// conditional branch + an unconditional branch to the destination.
1598 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1599 MachineInstr *MI = Br.MI;
1600 unsigned TargetOperand = branchTargetOperand(MI);
1601 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1602 unsigned Opcode = MI->getOpcode();
1603 unsigned LongFormOpcode = longformBranchOpcode(Opcode);
1604 unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
1606 // Check to see if the DestBB is already in-range.
1607 if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
1608 Br.MaxDisp = LongFormMaxOff;
1609 MI->setDesc(TII->get(LongFormOpcode));
1613 // Add an unconditional branch to the destination and invert the branch
1614 // condition to jump over it:
1621 // If the branch is at the end of its MBB and that has a fall-through block,
1622 // direct the updated conditional branch to the fall-through block. Otherwise,
1623 // split the MBB before the next instruction.
1624 MachineBasicBlock *MBB = MI->getParent();
1625 MachineInstr *BMI = &MBB->back();
1626 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1627 unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode);
1631 if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) &&
1632 isUnconditionalBranch(BMI->getOpcode())) {
1633 // Last MI in the BB is an unconditional branch. Can we simply invert the
1634 // condition and swap destinations:
1640 unsigned BMITargetOperand = branchTargetOperand(BMI);
1641 MachineBasicBlock *NewDest =
1642 BMI->getOperand(BMITargetOperand).getMBB();
1643 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1644 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1646 MI->setDesc(TII->get(OppositeBranchOpcode));
1647 BMI->getOperand(BMITargetOperand).setMBB(DestBB);
1648 MI->getOperand(TargetOperand).setMBB(NewDest);
1656 splitBlockBeforeInstr(MI);
1657 // No need for the branch to the next block. We're adding an unconditional
1658 // branch to the destination.
1659 int delta = TII->GetInstSizeInBytes(&MBB->back());
1660 BBInfo[MBB->getNumber()].Size -= delta;
1661 MBB->back().eraseFromParent();
1662 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1664 MachineBasicBlock *NextBB = std::next(MachineFunction::iterator(MBB));
1666 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1667 << " also invert condition and change dest. to BB#"
1668 << NextBB->getNumber() << "\n");
1670 // Insert a new conditional branch and a new unconditional branch.
1671 // Also update the ImmBranch as well as adding a new entry for the new branch.
1672 if (MI->getNumExplicitOperands() == 2) {
1673 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1674 .addReg(MI->getOperand(0).getReg())
1677 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1680 Br.MI = &MBB->back();
1681 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1682 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1683 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1684 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1685 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1687 // Remove the old conditional branch. It may or may not still be in MBB.
1688 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1689 MI->eraseFromParent();
1690 adjustBBOffsetsAfter(MBB);
1695 void MipsConstantIslands::prescanForConstants() {
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 PrescannedForConstants = true;
1705 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1706 J = I->getNumOperands();
1707 DEBUG(dbgs() << "num operands " << J << "\n");
1708 MachineOperand& Literal = I->getOperand(1);
1709 if (Literal.isImm()) {
1710 int64_t V = Literal.getImm();
1711 DEBUG(dbgs() << "literal " << V << "\n");
1713 Type::getInt32Ty(MF->getFunction()->getContext());
1714 const Constant *C = ConstantInt::get(Int32Ty, V);
1715 unsigned index = MCP->getConstantPoolIndex(C, 4);
1716 I->getOperand(2).ChangeToImmediate(index);
1717 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1718 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1719 I->RemoveOperand(1);
1720 I->RemoveOperand(1);
1721 I->addOperand(MachineOperand::CreateCPI(index, 0));
1722 I->addOperand(MachineOperand::CreateImm(4));