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/InstIterator.h"
40 #include "llvm/Support/MathExtras.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/Target/TargetInstrInfo.h"
43 #include "llvm/Target/TargetMachine.h"
44 #include "llvm/Target/TargetRegisterInfo.h"
45 #include "llvm/Support/Format.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"),
84 typedef MachineBasicBlock::iterator Iter;
85 typedef MachineBasicBlock::reverse_iterator ReverseIter;
87 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
88 /// requires constant pool entries to be scattered among the instructions
89 /// inside a function. To do this, it completely ignores the normal LLVM
90 /// constant pool; instead, it places constants wherever it feels like with
91 /// special instructions.
93 /// The terminology used in this pass includes:
94 /// Islands - Clumps of constants placed in the function.
95 /// Water - Potential places where an island could be formed.
96 /// CPE - A constant pool entry that has been placed somewhere, which
97 /// tracks a list of users.
99 class MipsConstantIslands : public MachineFunctionPass {
101 /// BasicBlockInfo - Information about the offset and size of a single
103 struct BasicBlockInfo {
104 /// Offset - Distance from the beginning of the function to the beginning
105 /// of this basic block.
107 /// Offsets are computed assuming worst case padding before an aligned
108 /// block. This means that subtracting basic block offsets always gives a
109 /// conservative estimate of the real distance which may be smaller.
111 /// Because worst case padding is used, the computed offset of an aligned
112 /// block may not actually be aligned.
115 /// Size - Size of the basic block in bytes. If the block contains
116 /// inline assembly, this is a worst case estimate.
118 /// The size does not include any alignment padding whether from the
119 /// beginning of the block, or from an aligned jump table at the end.
122 // FIXME: ignore LogAlign for this patch
124 unsigned postOffset(unsigned LogAlign = 0) const {
125 unsigned PO = Offset + Size;
129 BasicBlockInfo() : Offset(0), Size(0) {}
133 std::vector<BasicBlockInfo> BBInfo;
135 /// WaterList - A sorted list of basic blocks where islands could be placed
136 /// (i.e. blocks that don't fall through to the following block, due
137 /// to a return, unreachable, or unconditional branch).
138 std::vector<MachineBasicBlock*> WaterList;
140 /// NewWaterList - The subset of WaterList that was created since the
141 /// previous iteration by inserting unconditional branches.
142 SmallSet<MachineBasicBlock*, 4> NewWaterList;
144 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
146 /// CPUser - One user of a constant pool, keeping the machine instruction
147 /// pointer, the constant pool being referenced, and the max displacement
148 /// allowed from the instruction to the CP. The HighWaterMark records the
149 /// highest basic block where a new CPEntry can be placed. To ensure this
150 /// pass terminates, the CP entries are initially placed at the end of the
151 /// function and then move monotonically to lower addresses. The
152 /// exception to this rule is when the current CP entry for a particular
153 /// CPUser is out of range, but there is another CP entry for the same
154 /// constant value in range. We want to use the existing in-range CP
155 /// entry, but if it later moves out of range, the search for new water
156 /// should resume where it left off. The HighWaterMark is used to record
161 MachineBasicBlock *HighWaterMark;
164 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
165 // with different displacements
166 unsigned LongFormOpcode;
169 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
171 unsigned longformmaxdisp, unsigned longformopcode)
172 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
173 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
175 HighWaterMark = CPEMI->getParent();
177 /// getMaxDisp - Returns the maximum displacement supported by MI.
178 unsigned getMaxDisp() const {
179 unsigned xMaxDisp = ConstantIslandsSmallOffset?
180 ConstantIslandsSmallOffset: MaxDisp;
183 void setMaxDisp(unsigned val) {
186 unsigned getLongFormMaxDisp() const {
187 return LongFormMaxDisp;
189 unsigned getLongFormOpcode() const {
190 return LongFormOpcode;
194 /// CPUsers - Keep track of all of the machine instructions that use various
195 /// constant pools and their max displacement.
196 std::vector<CPUser> CPUsers;
198 /// CPEntry - One per constant pool entry, keeping the machine instruction
199 /// pointer, the constpool index, and the number of CPUser's which
200 /// reference this entry.
205 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
206 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
209 /// CPEntries - Keep track of all of the constant pool entry machine
210 /// instructions. For each original constpool index (i.e. those that
211 /// existed upon entry to this pass), it keeps a vector of entries.
212 /// Original elements are cloned as we go along; the clones are
213 /// put in the vector of the original element, but have distinct CPIs.
214 std::vector<std::vector<CPEntry> > CPEntries;
216 /// ImmBranch - One per immediate branch, keeping the machine instruction
217 /// pointer, conditional or unconditional, the max displacement,
218 /// and (if isCond is true) the corresponding unconditional branch
222 unsigned MaxDisp : 31;
225 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
226 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
229 /// ImmBranches - Keep track of all the immediate branch instructions.
231 std::vector<ImmBranch> ImmBranches;
233 /// HasFarJump - True if any far jump instruction has been emitted during
234 /// the branch fix up pass.
237 const TargetMachine &TM;
240 const MipsSubtarget *STI;
241 const Mips16InstrInfo *TII;
242 MipsFunctionInfo *MFI;
244 MachineConstantPool *MCP;
246 unsigned PICLabelUId;
247 bool PrescannedForConstants;
249 void initPICLabelUId(unsigned UId) {
254 unsigned createPICLabelUId() {
255 return PICLabelUId++;
260 MipsConstantIslands(TargetMachine &tm)
261 : MachineFunctionPass(ID), TM(tm),
262 IsPIC(TM.getRelocationModel() == Reloc::PIC_),
263 ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
264 STI(&TM.getSubtarget<MipsSubtarget>()), MF(0), MCP(0),
265 PrescannedForConstants(false){}
267 virtual const char *getPassName() const {
268 return "Mips Constant Islands";
271 bool runOnMachineFunction(MachineFunction &F);
273 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
274 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
275 unsigned getCPELogAlign(const MachineInstr *CPEMI);
276 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
277 unsigned getOffsetOf(MachineInstr *MI) const;
278 unsigned getUserOffset(CPUser&) const;
282 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
283 unsigned Disp, bool NegativeOK);
284 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
287 bool isLongFormOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
290 void computeBlockSize(MachineBasicBlock *MBB);
291 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
292 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
293 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
294 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
295 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
296 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
297 bool findAvailableWater(CPUser&U, unsigned UserOffset,
298 water_iterator &WaterIter);
299 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
300 MachineBasicBlock *&NewMBB);
301 bool handleConstantPoolUser(unsigned CPUserIndex);
302 void removeDeadCPEMI(MachineInstr *CPEMI);
303 bool removeUnusedCPEntries();
304 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
305 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
306 bool DoDump = false);
307 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
308 CPUser &U, unsigned &Growth);
309 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
310 bool fixupImmediateBr(ImmBranch &Br);
311 bool fixupConditionalBr(ImmBranch &Br);
312 bool fixupUnconditionalBr(ImmBranch &Br);
314 void prescanForConstants();
320 char MipsConstantIslands::ID = 0;
321 } // end of anonymous namespace
324 bool MipsConstantIslands::isLongFormOffsetInRange
325 (unsigned UserOffset, unsigned TrialOffset,
327 return isOffsetInRange(UserOffset, TrialOffset,
328 U.getLongFormMaxDisp(), U.NegOk);
331 bool MipsConstantIslands::isOffsetInRange
332 (unsigned UserOffset, unsigned TrialOffset,
334 return isOffsetInRange(UserOffset, TrialOffset,
335 U.getMaxDisp(), U.NegOk);
337 /// print block size and offset information - debugging
338 void MipsConstantIslands::dumpBBs() {
340 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
341 const BasicBlockInfo &BBI = BBInfo[J];
342 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
343 << format(" size=%#x\n", BBInfo[J].Size);
347 /// createMipsLongBranchPass - Returns a pass that converts branches to long
349 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
350 return new MipsConstantIslands(tm);
353 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
354 // The intention is for this to be a mips16 only pass for now
357 MCP = mf.getConstantPool();
358 DEBUG(dbgs() << "constant island machine function " << "\n");
359 if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode() ||
360 !MipsSubtarget::useConstantIslands()) {
363 TII = (const Mips16InstrInfo*)MF->getTarget().getInstrInfo();
364 MFI = MF->getInfo<MipsFunctionInfo>();
365 DEBUG(dbgs() << "constant island processing " << "\n");
367 // will need to make predermination if there is any constants we need to
368 // put in constant islands. TBD.
370 if (!PrescannedForConstants) prescanForConstants();
373 // This pass invalidates liveness information when it splits basic blocks.
374 MF->getRegInfo().invalidateLiveness();
376 // Renumber all of the machine basic blocks in the function, guaranteeing that
377 // the numbers agree with the position of the block in the function.
378 MF->RenumberBlocks();
380 bool MadeChange = false;
382 // Perform the initial placement of the constant pool entries. To start with,
383 // we put them all at the end of the function.
384 std::vector<MachineInstr*> CPEMIs;
386 doInitialPlacement(CPEMIs);
388 /// The next UID to take is the first unused one.
389 initPICLabelUId(CPEMIs.size());
391 // Do the initial scan of the function, building up information about the
392 // sizes of each block, the location of all the water, and finding all of the
393 // constant pool users.
394 initializeFunctionInfo(CPEMIs);
398 /// Remove dead constant pool entries.
399 MadeChange |= removeUnusedCPEntries();
401 // Iteratively place constant pool entries and fix up branches until there
403 unsigned NoCPIters = 0, NoBRIters = 0;
406 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
407 bool CPChange = false;
408 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
409 CPChange |= handleConstantPoolUser(i);
410 if (CPChange && ++NoCPIters > 30)
411 report_fatal_error("Constant Island pass failed to converge!");
414 // Clear NewWaterList now. If we split a block for branches, it should
415 // appear as "new water" for the next iteration of constant pool placement.
416 NewWaterList.clear();
418 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
419 bool BRChange = false;
421 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
422 BRChange |= fixupImmediateBr(ImmBranches[i]);
423 if (BRChange && ++NoBRIters > 30)
424 report_fatal_error("Branch Fix Up pass failed to converge!");
427 if (!CPChange && !BRChange)
432 DEBUG(dbgs() << '\n'; dumpBBs());
442 /// doInitialPlacement - Perform the initial placement of the constant pool
443 /// entries. To start with, we put them all at the end of the function.
445 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
446 // Create the basic block to hold the CPE's.
447 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
451 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
452 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
454 // Mark the basic block as required by the const-pool.
455 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
456 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
458 // The function needs to be as aligned as the basic blocks. The linker may
459 // move functions around based on their alignment.
460 MF->ensureAlignment(BB->getAlignment());
462 // Order the entries in BB by descending alignment. That ensures correct
463 // alignment of all entries as long as BB is sufficiently aligned. Keep
464 // track of the insertion point for each alignment. We are going to bucket
465 // sort the entries as they are created.
466 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
468 // Add all of the constants from the constant pool to the end block, use an
469 // identity mapping of CPI's to CPE's.
470 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
472 const DataLayout &TD = *MF->getTarget().getDataLayout();
473 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
474 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
475 assert(Size >= 4 && "Too small constant pool entry");
476 unsigned Align = CPs[i].getAlignment();
477 assert(isPowerOf2_32(Align) && "Invalid alignment");
478 // Verify that all constant pool entries are a multiple of their alignment.
479 // If not, we would have to pad them out so that instructions stay aligned.
480 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
482 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
483 unsigned LogAlign = Log2_32(Align);
484 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
486 MachineInstr *CPEMI =
487 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
488 .addImm(i).addConstantPoolIndex(i).addImm(Size);
490 CPEMIs.push_back(CPEMI);
492 // Ensure that future entries with higher alignment get inserted before
493 // CPEMI. This is bucket sort with iterators.
494 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
495 if (InsPoint[a] == InsAt)
497 // Add a new CPEntry, but no corresponding CPUser yet.
498 std::vector<CPEntry> CPEs;
499 CPEs.push_back(CPEntry(CPEMI, i));
500 CPEntries.push_back(CPEs);
502 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
503 << Size << ", align = " << Align <<'\n');
508 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
509 /// into the block immediately after it.
510 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
511 // Get the next machine basic block in the function.
512 MachineFunction::iterator MBBI = MBB;
513 // Can't fall off end of function.
514 if (llvm::next(MBBI) == MBB->getParent()->end())
517 MachineBasicBlock *NextBB = llvm::next(MBBI);
518 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
519 E = MBB->succ_end(); I != E; ++I)
526 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
527 /// look up the corresponding CPEntry.
528 MipsConstantIslands::CPEntry
529 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
530 const MachineInstr *CPEMI) {
531 std::vector<CPEntry> &CPEs = CPEntries[CPI];
532 // Number of entries per constpool index should be small, just do a
534 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
535 if (CPEs[i].CPEMI == CPEMI)
541 /// getCPELogAlign - Returns the required alignment of the constant pool entry
542 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
543 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
544 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
546 // Everything is 4-byte aligned unless AlignConstantIslands is set.
547 if (!AlignConstantIslands)
550 unsigned CPI = CPEMI->getOperand(1).getIndex();
551 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
552 unsigned Align = MCP->getConstants()[CPI].getAlignment();
553 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
554 return Log2_32(Align);
557 /// initializeFunctionInfo - Do the initial scan of the function, building up
558 /// information about the sizes of each block, the location of all the water,
559 /// and finding all of the constant pool users.
560 void MipsConstantIslands::
561 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
563 BBInfo.resize(MF->getNumBlockIDs());
565 // First thing, compute the size of all basic blocks, and see if the function
566 // has any inline assembly in it. If so, we have to be conservative about
567 // alignment assumptions, as we don't know for sure the size of any
568 // instructions in the inline assembly.
569 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
573 // Compute block offsets.
574 adjustBBOffsetsAfter(MF->begin());
576 // Now go back through the instructions and build up our data structures.
577 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
579 MachineBasicBlock &MBB = *MBBI;
581 // If this block doesn't fall through into the next MBB, then this is
582 // 'water' that a constant pool island could be placed.
583 if (!BBHasFallthrough(&MBB))
584 WaterList.push_back(&MBB);
585 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
587 if (I->isDebugValue())
590 int Opc = I->getOpcode();
599 continue; // Ignore other JT branches
601 // Record this immediate branch.
602 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
603 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
607 if (Opc == Mips::CONSTPOOL_ENTRY)
611 // Scan the instructions for constant pool operands.
612 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
613 if (I->getOperand(op).isCPI()) {
615 // We found one. The addressing mode tells us the max displacement
616 // from the PC that this instruction permits.
618 // Basic size info comes from the TSFlags field.
622 unsigned LongFormBits = 0;
623 unsigned LongFormScale = 0;
624 unsigned LongFormOpcode = 0;
627 llvm_unreachable("Unknown addressing mode for CP reference!");
628 case Mips::LwRxPcTcp16:
631 LongFormOpcode = Mips::LwRxPcTcpX16;
635 case Mips::LwRxPcTcpX16:
641 // Remember that this is a user of a CP entry.
642 unsigned CPI = I->getOperand(op).getIndex();
643 MachineInstr *CPEMI = CPEMIs[CPI];
644 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
645 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
646 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
647 LongFormMaxOffs, LongFormOpcode));
649 // Increment corresponding CPEntry reference count.
650 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
651 assert(CPE && "Cannot find a corresponding CPEntry!");
654 // Instructions can only use one CP entry, don't bother scanning the
655 // rest of the operands.
665 /// computeBlockSize - Compute the size and some alignment information for MBB.
666 /// This function updates BBInfo directly.
667 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
668 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
671 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
673 BBI.Size += TII->GetInstSizeInBytes(I);
677 /// getOffsetOf - Return the current offset of the specified machine instruction
678 /// from the start of the function. This offset changes as stuff is moved
679 /// around inside the function.
680 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
681 MachineBasicBlock *MBB = MI->getParent();
683 // The offset is composed of two things: the sum of the sizes of all MBB's
684 // before this instruction's block, and the offset from the start of the block
686 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
688 // Sum instructions before MI in MBB.
689 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
690 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
691 Offset += TII->GetInstSizeInBytes(I);
696 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
698 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
699 const MachineBasicBlock *RHS) {
700 return LHS->getNumber() < RHS->getNumber();
703 /// updateForInsertedWaterBlock - When a block is newly inserted into the
704 /// machine function, it upsets all of the block numbers. Renumber the blocks
705 /// and update the arrays that parallel this numbering.
706 void MipsConstantIslands::updateForInsertedWaterBlock
707 (MachineBasicBlock *NewBB) {
708 // Renumber the MBB's to keep them consecutive.
709 NewBB->getParent()->RenumberBlocks(NewBB);
711 // Insert an entry into BBInfo to align it properly with the (newly
712 // renumbered) block numbers.
713 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
715 // Next, update WaterList. Specifically, we need to add NewMBB as having
716 // available water after it.
718 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
720 WaterList.insert(IP, NewBB);
723 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
724 return getOffsetOf(U.MI);
727 /// Split the basic block containing MI into two blocks, which are joined by
728 /// an unconditional branch. Update data structures and renumber blocks to
729 /// account for this change and returns the newly created block.
730 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
732 MachineBasicBlock *OrigBB = MI->getParent();
734 // Create a new MBB for the code after the OrigBB.
735 MachineBasicBlock *NewBB =
736 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
737 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
738 MF->insert(MBBI, NewBB);
740 // Splice the instructions starting with MI over to NewBB.
741 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
743 // Add an unconditional branch from OrigBB to NewBB.
744 // Note the new unconditional branch is not being recorded.
745 // There doesn't seem to be meaningful DebugInfo available; this doesn't
746 // correspond to anything in the source.
747 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
750 // Update the CFG. All succs of OrigBB are now succs of NewBB.
751 NewBB->transferSuccessors(OrigBB);
753 // OrigBB branches to NewBB.
754 OrigBB->addSuccessor(NewBB);
756 // Update internal data structures to account for the newly inserted MBB.
757 // This is almost the same as updateForInsertedWaterBlock, except that
758 // the Water goes after OrigBB, not NewBB.
759 MF->RenumberBlocks(NewBB);
761 // Insert an entry into BBInfo to align it properly with the (newly
762 // renumbered) block numbers.
763 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
765 // Next, update WaterList. Specifically, we need to add OrigMBB as having
766 // available water after it (but not if it's already there, which happens
767 // when splitting before a conditional branch that is followed by an
768 // unconditional branch - in that case we want to insert NewBB).
770 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
772 MachineBasicBlock* WaterBB = *IP;
773 if (WaterBB == OrigBB)
774 WaterList.insert(llvm::next(IP), NewBB);
776 WaterList.insert(IP, OrigBB);
777 NewWaterList.insert(OrigBB);
779 // Figure out how large the OrigBB is. As the first half of the original
780 // block, it cannot contain a tablejump. The size includes
781 // the new jump we added. (It should be possible to do this without
782 // recounting everything, but it's very confusing, and this is rarely
784 computeBlockSize(OrigBB);
786 // Figure out how large the NewMBB is. As the second half of the original
787 // block, it may contain a tablejump.
788 computeBlockSize(NewBB);
790 // All BBOffsets following these blocks must be modified.
791 adjustBBOffsetsAfter(OrigBB);
798 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
799 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
800 /// constant pool entry).
801 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
802 unsigned TrialOffset, unsigned MaxDisp,
804 if (UserOffset <= TrialOffset) {
805 // User before the Trial.
806 if (TrialOffset - UserOffset <= MaxDisp)
808 } else if (NegativeOK) {
809 if (UserOffset - TrialOffset <= MaxDisp)
815 /// isWaterInRange - Returns true if a CPE placed after the specified
816 /// Water (a basic block) will be in range for the specific MI.
818 /// Compute how much the function will grow by inserting a CPE after Water.
819 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
820 MachineBasicBlock* Water, CPUser &U,
822 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
823 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
824 unsigned NextBlockOffset, NextBlockAlignment;
825 MachineFunction::const_iterator NextBlock = Water;
826 if (++NextBlock == MF->end()) {
827 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
828 NextBlockAlignment = 0;
830 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
831 NextBlockAlignment = NextBlock->getAlignment();
833 unsigned Size = U.CPEMI->getOperand(2).getImm();
834 unsigned CPEEnd = CPEOffset + Size;
836 // The CPE may be able to hide in the alignment padding before the next
837 // block. It may also cause more padding to be required if it is more aligned
838 // that the next block.
839 if (CPEEnd > NextBlockOffset) {
840 Growth = CPEEnd - NextBlockOffset;
841 // Compute the padding that would go at the end of the CPE to align the next
843 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
845 // If the CPE is to be inserted before the instruction, that will raise
846 // the offset of the instruction. Also account for unknown alignment padding
847 // in blocks between CPE and the user.
848 if (CPEOffset < UserOffset)
849 UserOffset += Growth;
851 // CPE fits in existing padding.
854 return isOffsetInRange(UserOffset, CPEOffset, U);
857 /// isCPEntryInRange - Returns true if the distance between specific MI and
858 /// specific ConstPool entry instruction can fit in MI's displacement field.
859 bool MipsConstantIslands::isCPEntryInRange
860 (MachineInstr *MI, unsigned UserOffset,
861 MachineInstr *CPEMI, unsigned MaxDisp,
862 bool NegOk, bool DoDump) {
863 unsigned CPEOffset = getOffsetOf(CPEMI);
867 unsigned Block = MI->getParent()->getNumber();
868 const BasicBlockInfo &BBI = BBInfo[Block];
869 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
870 << " max delta=" << MaxDisp
871 << format(" insn address=%#x", UserOffset)
872 << " in BB#" << Block << ": "
873 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
874 << format("CPE address=%#x offset=%+d: ", CPEOffset,
875 int(CPEOffset-UserOffset));
879 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
883 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
884 /// unconditionally branches to its only successor.
885 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
886 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
888 MachineBasicBlock *Succ = *MBB->succ_begin();
889 MachineBasicBlock *Pred = *MBB->pred_begin();
890 MachineInstr *PredMI = &Pred->back();
891 if (PredMI->getOpcode() == Mips::Bimm16)
892 return PredMI->getOperand(0).getMBB() == Succ;
897 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
898 unsigned BBNum = BB->getNumber();
899 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
900 // Get the offset and known bits at the end of the layout predecessor.
901 // Include the alignment of the current block.
902 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
903 BBInfo[i].Offset = Offset;
907 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
908 /// and instruction CPEMI, and decrement its refcount. If the refcount
909 /// becomes 0 remove the entry and instruction. Returns true if we removed
910 /// the entry, false if we didn't.
912 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
913 MachineInstr *CPEMI) {
914 // Find the old entry. Eliminate it if it is no longer used.
915 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
916 assert(CPE && "Unexpected!");
917 if (--CPE->RefCount == 0) {
918 removeDeadCPEMI(CPEMI);
926 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
927 /// if not, see if an in-range clone of the CPE is in range, and if so,
928 /// change the data structures so the user references the clone. Returns:
929 /// 0 = no existing entry found
930 /// 1 = entry found, and there were no code insertions or deletions
931 /// 2 = entry found, and there were code insertions or deletions
932 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
934 MachineInstr *UserMI = U.MI;
935 MachineInstr *CPEMI = U.CPEMI;
937 // Check to see if the CPE is already in-range.
938 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
940 DEBUG(dbgs() << "In range\n");
944 // No. Look for previously created clones of the CPE that are in range.
945 unsigned CPI = CPEMI->getOperand(1).getIndex();
946 std::vector<CPEntry> &CPEs = CPEntries[CPI];
947 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
948 // We already tried this one
949 if (CPEs[i].CPEMI == CPEMI)
951 // Removing CPEs can leave empty entries, skip
952 if (CPEs[i].CPEMI == NULL)
954 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
956 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
957 << CPEs[i].CPI << "\n");
958 // Point the CPUser node to the replacement
959 U.CPEMI = CPEs[i].CPEMI;
960 // Change the CPI in the instruction operand to refer to the clone.
961 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
962 if (UserMI->getOperand(j).isCPI()) {
963 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
966 // Adjust the refcount of the clone...
968 // ...and the original. If we didn't remove the old entry, none of the
969 // addresses changed, so we don't need another pass.
970 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
976 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
977 /// This version checks if the longer form of the instruction can be used to
978 /// to satisfy things.
979 /// if not, see if an in-range clone of the CPE is in range, and if so,
980 /// change the data structures so the user references the clone. Returns:
981 /// 0 = no existing entry found
982 /// 1 = entry found, and there were no code insertions or deletions
983 /// 2 = entry found, and there were code insertions or deletions
984 int MipsConstantIslands::findLongFormInRangeCPEntry
985 (CPUser& U, unsigned UserOffset)
987 MachineInstr *UserMI = U.MI;
988 MachineInstr *CPEMI = U.CPEMI;
990 // Check to see if the CPE is already in-range.
991 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
992 U.getLongFormMaxDisp(), U.NegOk,
994 DEBUG(dbgs() << "In range\n");
995 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
996 U.setMaxDisp(U.getLongFormMaxDisp());
997 return 2; // instruction is longer length now
1000 // No. Look for previously created clones of the CPE that are in range.
1001 unsigned CPI = CPEMI->getOperand(1).getIndex();
1002 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1003 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1004 // We already tried this one
1005 if (CPEs[i].CPEMI == CPEMI)
1007 // Removing CPEs can leave empty entries, skip
1008 if (CPEs[i].CPEMI == NULL)
1010 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1011 U.getLongFormMaxDisp(), U.NegOk)) {
1012 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1013 << CPEs[i].CPI << "\n");
1014 // Point the CPUser node to the replacement
1015 U.CPEMI = CPEs[i].CPEMI;
1016 // Change the CPI in the instruction operand to refer to the clone.
1017 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1018 if (UserMI->getOperand(j).isCPI()) {
1019 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1022 // Adjust the refcount of the clone...
1024 // ...and the original. If we didn't remove the old entry, none of the
1025 // addresses changed, so we don't need another pass.
1026 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1032 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1033 /// the specific unconditional branch instruction.
1034 static inline unsigned getUnconditionalBrDisp(int Opc) {
1037 return ((1<<10)-1)*2;
1039 return ((1<<16)-1)*2;
1043 return ((1<<16)-1)*2;
1046 /// findAvailableWater - Look for an existing entry in the WaterList in which
1047 /// we can place the CPE referenced from U so it's within range of U's MI.
1048 /// Returns true if found, false if not. If it returns true, WaterIter
1049 /// is set to the WaterList entry.
1050 /// To ensure that this pass
1051 /// terminates, the CPE location for a particular CPUser is only allowed to
1052 /// move to a lower address, so search backward from the end of the list and
1053 /// prefer the first water that is in range.
1054 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1055 water_iterator &WaterIter) {
1056 if (WaterList.empty())
1059 unsigned BestGrowth = ~0u;
1060 for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();;
1062 MachineBasicBlock* WaterBB = *IP;
1063 // Check if water is in range and is either at a lower address than the
1064 // current "high water mark" or a new water block that was created since
1065 // the previous iteration by inserting an unconditional branch. In the
1066 // latter case, we want to allow resetting the high water mark back to
1067 // this new water since we haven't seen it before. Inserting branches
1068 // should be relatively uncommon and when it does happen, we want to be
1069 // sure to take advantage of it for all the CPEs near that block, so that
1070 // we don't insert more branches than necessary.
1072 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1073 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1074 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1075 // This is the least amount of required padding seen so far.
1076 BestGrowth = Growth;
1078 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1079 << " Growth=" << Growth << '\n');
1081 // Keep looking unless it is perfect.
1082 if (BestGrowth == 0)
1088 return BestGrowth != ~0u;
1091 /// createNewWater - No existing WaterList entry will work for
1092 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1093 /// block is used if in range, and the conditional branch munged so control
1094 /// flow is correct. Otherwise the block is split to create a hole with an
1095 /// unconditional branch around it. In either case NewMBB is set to a
1096 /// block following which the new island can be inserted (the WaterList
1097 /// is not adjusted).
1098 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1099 unsigned UserOffset,
1100 MachineBasicBlock *&NewMBB) {
1101 CPUser &U = CPUsers[CPUserIndex];
1102 MachineInstr *UserMI = U.MI;
1103 MachineInstr *CPEMI = U.CPEMI;
1104 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1105 MachineBasicBlock *UserMBB = UserMI->getParent();
1106 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1108 // If the block does not end in an unconditional branch already, and if the
1109 // end of the block is within range, make new water there.
1110 if (BBHasFallthrough(UserMBB)) {
1111 // Size of branch to insert.
1113 // Compute the offset where the CPE will begin.
1114 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1116 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1117 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1118 << format(", expected CPE offset %#x\n", CPEOffset));
1119 NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
1120 // Add an unconditional branch from UserMBB to fallthrough block. Record
1121 // it for branch lengthening; this new branch will not get out of range,
1122 // but if the preceding conditional branch is out of range, the targets
1123 // will be exchanged, and the altered branch may be out of range, so the
1124 // machinery has to know about it.
1125 int UncondBr = Mips::Bimm16;
1126 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1127 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1128 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1129 MaxDisp, false, UncondBr));
1130 BBInfo[UserMBB->getNumber()].Size += Delta;
1131 adjustBBOffsetsAfter(UserMBB);
1136 // What a big block. Find a place within the block to split it.
1138 // Try to split the block so it's fully aligned. Compute the latest split
1139 // point where we can add a 4-byte branch instruction, and then align to
1140 // LogAlign which is the largest possible alignment in the function.
1141 unsigned LogAlign = MF->getAlignment();
1142 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1143 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1144 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1147 // The 4 in the following is for the unconditional branch we'll be inserting
1148 // Alignment of the island is handled
1149 // inside isOffsetInRange.
1150 BaseInsertOffset -= 4;
1152 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1153 << " la=" << LogAlign << '\n');
1155 // This could point off the end of the block if we've already got constant
1156 // pool entries following this block; only the last one is in the water list.
1157 // Back past any possible branches (allow for a conditional and a maximally
1158 // long unconditional).
1159 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1160 BaseInsertOffset = UserBBI.postOffset() - 8;
1161 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1163 unsigned EndInsertOffset = BaseInsertOffset + 4 +
1164 CPEMI->getOperand(2).getImm();
1165 MachineBasicBlock::iterator MI = UserMI;
1167 unsigned CPUIndex = CPUserIndex+1;
1168 unsigned NumCPUsers = CPUsers.size();
1169 //MachineInstr *LastIT = 0;
1170 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1171 Offset < BaseInsertOffset;
1172 Offset += TII->GetInstSizeInBytes(MI),
1173 MI = llvm::next(MI)) {
1174 assert(MI != UserMBB->end() && "Fell off end of block");
1175 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1176 CPUser &U = CPUsers[CPUIndex];
1177 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1178 // Shift intertion point by one unit of alignment so it is within reach.
1179 BaseInsertOffset -= 1u << LogAlign;
1180 EndInsertOffset -= 1u << LogAlign;
1182 // This is overly conservative, as we don't account for CPEMIs being
1183 // reused within the block, but it doesn't matter much. Also assume CPEs
1184 // are added in order with alignment padding. We may eventually be able
1185 // to pack the aligned CPEs better.
1186 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1192 NewMBB = splitBlockBeforeInstr(MI);
1195 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1196 /// is out-of-range. If so, pick up the constant pool value and move it some
1197 /// place in-range. Return true if we changed any addresses (thus must run
1198 /// another pass of branch lengthening), false otherwise.
1199 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1200 CPUser &U = CPUsers[CPUserIndex];
1201 MachineInstr *UserMI = U.MI;
1202 MachineInstr *CPEMI = U.CPEMI;
1203 unsigned CPI = CPEMI->getOperand(1).getIndex();
1204 unsigned Size = CPEMI->getOperand(2).getImm();
1205 // Compute this only once, it's expensive.
1206 unsigned UserOffset = getUserOffset(U);
1208 // See if the current entry is within range, or there is a clone of it
1210 int result = findInRangeCPEntry(U, UserOffset);
1211 if (result==1) return false;
1212 else if (result==2) return true;
1215 // Look for water where we can place this CPE.
1216 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1217 MachineBasicBlock *NewMBB;
1219 if (findAvailableWater(U, UserOffset, IP)) {
1220 DEBUG(dbgs() << "Found water in range\n");
1221 MachineBasicBlock *WaterBB = *IP;
1223 // If the original WaterList entry was "new water" on this iteration,
1224 // propagate that to the new island. This is just keeping NewWaterList
1225 // updated to match the WaterList, which will be updated below.
1226 if (NewWaterList.erase(WaterBB))
1227 NewWaterList.insert(NewIsland);
1229 // The new CPE goes before the following block (NewMBB).
1230 NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
1234 // we first see if a longer form of the instrucion could have reached
1235 // the constant. in that case we won't bother to split
1236 if (!NoLoadRelaxation) {
1237 result = findLongFormInRangeCPEntry(U, UserOffset);
1238 if (result != 0) return true;
1240 DEBUG(dbgs() << "No water found\n");
1241 createNewWater(CPUserIndex, UserOffset, NewMBB);
1243 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1244 // called while handling branches so that the water will be seen on the
1245 // next iteration for constant pools, but in this context, we don't want
1246 // it. Check for this so it will be removed from the WaterList.
1247 // Also remove any entry from NewWaterList.
1248 MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
1249 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1250 if (IP != WaterList.end())
1251 NewWaterList.erase(WaterBB);
1253 // We are adding new water. Update NewWaterList.
1254 NewWaterList.insert(NewIsland);
1257 // Remove the original WaterList entry; we want subsequent insertions in
1258 // this vicinity to go after the one we're about to insert. This
1259 // considerably reduces the number of times we have to move the same CPE
1260 // more than once and is also important to ensure the algorithm terminates.
1261 if (IP != WaterList.end())
1262 WaterList.erase(IP);
1264 // Okay, we know we can put an island before NewMBB now, do it!
1265 MF->insert(NewMBB, NewIsland);
1267 // Update internal data structures to account for the newly inserted MBB.
1268 updateForInsertedWaterBlock(NewIsland);
1270 // Decrement the old entry, and remove it if refcount becomes 0.
1271 decrementCPEReferenceCount(CPI, CPEMI);
1273 // Now that we have an island to add the CPE to, clone the original CPE and
1274 // add it to the island.
1275 U.HighWaterMark = NewIsland;
1276 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1277 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1278 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1281 // Mark the basic block as aligned as required by the const-pool entry.
1282 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1284 // Increase the size of the island block to account for the new entry.
1285 BBInfo[NewIsland->getNumber()].Size += Size;
1286 adjustBBOffsetsAfter(llvm::prior(MachineFunction::iterator(NewIsland)));
1288 // No existing clone of this CPE is within range.
1289 // We will be generating a new clone. Get a UID for it.
1290 unsigned ID = createPICLabelUId();
1292 // Finally, change the CPI in the instruction operand to be ID.
1293 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1294 if (UserMI->getOperand(i).isCPI()) {
1295 UserMI->getOperand(i).setIndex(ID);
1299 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1300 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1305 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1306 /// sizes and offsets of impacted basic blocks.
1307 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1308 MachineBasicBlock *CPEBB = CPEMI->getParent();
1309 unsigned Size = CPEMI->getOperand(2).getImm();
1310 CPEMI->eraseFromParent();
1311 BBInfo[CPEBB->getNumber()].Size -= Size;
1312 // All succeeding offsets have the current size value added in, fix this.
1313 if (CPEBB->empty()) {
1314 BBInfo[CPEBB->getNumber()].Size = 0;
1316 // This block no longer needs to be aligned.
1317 CPEBB->setAlignment(0);
1319 // Entries are sorted by descending alignment, so realign from the front.
1320 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1322 adjustBBOffsetsAfter(CPEBB);
1323 // An island has only one predecessor BB and one successor BB. Check if
1324 // this BB's predecessor jumps directly to this BB's successor. This
1325 // shouldn't happen currently.
1326 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1327 // FIXME: remove the empty blocks after all the work is done?
1330 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1332 bool MipsConstantIslands::removeUnusedCPEntries() {
1333 unsigned MadeChange = false;
1334 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1335 std::vector<CPEntry> &CPEs = CPEntries[i];
1336 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1337 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1338 removeDeadCPEMI(CPEs[j].CPEMI);
1339 CPEs[j].CPEMI = NULL;
1347 /// isBBInRange - Returns true if the distance between specific MI and
1348 /// specific BB can fit in MI's displacement field.
1349 bool MipsConstantIslands::isBBInRange
1350 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1354 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1355 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1357 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1358 << " from BB#" << MI->getParent()->getNumber()
1359 << " max delta=" << MaxDisp
1360 << " from " << getOffsetOf(MI) << " to " << DestOffset
1361 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1363 if (BrOffset <= DestOffset) {
1364 // Branch before the Dest.
1365 if (DestOffset-BrOffset <= MaxDisp)
1368 if (BrOffset-DestOffset <= MaxDisp)
1374 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1375 /// away to fit in its displacement field.
1376 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1377 MachineInstr *MI = Br.MI;
1378 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1380 // Check to see if the DestBB is already in-range.
1381 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1385 return fixupUnconditionalBr(Br);
1386 return fixupConditionalBr(Br);
1389 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1390 /// too far away to fit in its displacement field. If the LR register has been
1391 /// spilled in the epilogue, then we can use BL to implement a far jump.
1392 /// Otherwise, add an intermediate branch instruction to a branch.
1394 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1395 MachineInstr *MI = Br.MI;
1396 MachineBasicBlock *MBB = MI->getParent();
1397 // Use BL to implement far jump.
1398 Br.MaxDisp = ((1 << 16)-1) * 2;
1399 MI->setDesc(TII->get(Mips::BimmX16));
1400 BBInfo[MBB->getNumber()].Size += 2;
1401 adjustBBOffsetsAfter(MBB);
1405 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1410 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1411 /// far away to fit in its displacement field. It is converted to an inverse
1412 /// conditional branch + an unconditional branch to the destination.
1414 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1415 MachineInstr *MI = Br.MI;
1416 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1418 // Add an unconditional branch to the destination and invert the branch
1419 // condition to jump over it:
1425 unsigned CCReg = 0; // FIXME
1426 unsigned CC=0; //FIXME
1428 // If the branch is at the end of its MBB and that has a fall-through block,
1429 // direct the updated conditional branch to the fall-through block. Otherwise,
1430 // split the MBB before the next instruction.
1431 MachineBasicBlock *MBB = MI->getParent();
1432 MachineInstr *BMI = &MBB->back();
1433 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1437 if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
1438 BMI->getOpcode() == Br.UncondBr) {
1439 // Last MI in the BB is an unconditional branch. Can we simply invert the
1440 // condition and swap destinations:
1446 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
1447 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1448 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1450 BMI->getOperand(0).setMBB(DestBB);
1451 MI->getOperand(0).setMBB(NewDest);
1458 splitBlockBeforeInstr(MI);
1459 // No need for the branch to the next block. We're adding an unconditional
1460 // branch to the destination.
1461 int delta = TII->GetInstSizeInBytes(&MBB->back());
1462 BBInfo[MBB->getNumber()].Size -= delta;
1463 MBB->back().eraseFromParent();
1464 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1466 MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
1468 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1469 << " also invert condition and change dest. to BB#"
1470 << NextBB->getNumber() << "\n");
1472 // Insert a new conditional branch and a new unconditional branch.
1473 // Also update the ImmBranch as well as adding a new entry for the new branch.
1474 BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode()))
1475 .addMBB(NextBB).addImm(CC).addReg(CCReg);
1476 Br.MI = &MBB->back();
1477 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1478 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1479 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1480 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1481 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1483 // Remove the old conditional branch. It may or may not still be in MBB.
1484 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1485 MI->eraseFromParent();
1486 adjustBBOffsetsAfter(MBB);
1491 void MipsConstantIslands::prescanForConstants() {
1494 PrescannedForConstants = true;
1495 for (MachineFunction::iterator B =
1496 MF->begin(), E = MF->end(); B != E; ++B) {
1497 for (MachineBasicBlock::instr_iterator I =
1498 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1499 switch(I->getDesc().getOpcode()) {
1500 case Mips::LwConstant32: {
1501 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1502 J = I->getNumOperands();
1503 DEBUG(dbgs() << "num operands " << J << "\n");
1504 MachineOperand& Literal = I->getOperand(1);
1505 if (Literal.isImm()) {
1506 int64_t V = Literal.getImm();
1507 DEBUG(dbgs() << "literal " << V << "\n");
1509 Type::getInt32Ty(MF->getFunction()->getContext());
1510 const Constant *C = ConstantInt::get(Int32Ty, V);
1511 unsigned index = MCP->getConstantPoolIndex(C, 4);
1512 I->getOperand(2).ChangeToImmediate(index);
1513 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1514 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1515 I->RemoveOperand(1);
1516 I->RemoveOperand(1);
1517 I->addOperand(MachineOperand::CreateCPI(index, 0));
1518 I->addOperand(MachineOperand::CreateImm(4));