1 //===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //
11 // This pass is used to make Pc relative loads of constants.
12 // For now, only Mips16 will use this.
13 //
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.
17 //
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
20 // non-linux targets.
21 //
22 //
23
24 #include "Mips.h"
25 #include "MCTargetDesc/MipsBaseInfo.h"
26 #include "Mips16InstrInfo.h"
27 #include "MipsMachineFunction.h"
28 #include "MipsTargetMachine.h"
29 #include "llvm/ADT/Statistic.h"
30 #include "llvm/CodeGen/MachineBasicBlock.h"
31 #include "llvm/CodeGen/MachineConstantPool.h"
32 #include "llvm/CodeGen/MachineFunctionPass.h"
33 #include "llvm/CodeGen/MachineInstrBuilder.h"
34 #include "llvm/CodeGen/MachineRegisterInfo.h"
35 #include "llvm/IR/Function.h"
36 #include "llvm/IR/InstIterator.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/Format.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 <algorithm>
46
47 using namespace llvm;
48
49 #define DEBUG_TYPE "mips-constant-islands"
50
51 STATISTIC(NumCPEs, "Number of constpool entries");
52 STATISTIC(NumSplit, "Number of uncond branches inserted");
53 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
54 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
55
56 // FIXME: This option should be removed once it has received sufficient testing.
57 static cl::opt<bool>
58 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
59 cl::desc("Align constant islands in code"));
60
61
62 // Rather than do make check tests with huge amounts of code, we force
63 // the test to use this amount.
64 //
65 static cl::opt<int> ConstantIslandsSmallOffset(
66 "mips-constant-islands-small-offset",
67 cl::init(0),
68 cl::desc("Make small offsets be this amount for testing purposes"),
69 cl::Hidden);
70
71 //
72 // For testing purposes we tell it to not use relaxed load forms so that it
73 // will split blocks.
74 //
75 static cl::opt<bool> NoLoadRelaxation(
76 "mips-constant-islands-no-load-relaxation",
77 cl::init(false),
78 cl::desc("Don't relax loads to long loads - for testing purposes"),
79 cl::Hidden);
80
branchTargetOperand(MachineInstr * MI)81 static unsigned int branchTargetOperand(MachineInstr *MI) {
82 switch (MI->getOpcode()) {
83 case Mips::Bimm16:
84 case Mips::BimmX16:
85 case Mips::Bteqz16:
86 case Mips::BteqzX16:
87 case Mips::Btnez16:
88 case Mips::BtnezX16:
89 case Mips::JalB16:
90 return 0;
91 case Mips::BeqzRxImm16:
92 case Mips::BeqzRxImmX16:
93 case Mips::BnezRxImm16:
94 case Mips::BnezRxImmX16:
95 return 1;
96 }
97 llvm_unreachable("Unknown branch type");
98 }
99
isUnconditionalBranch(unsigned int Opcode)100 static bool isUnconditionalBranch(unsigned int Opcode) {
101 switch (Opcode) {
102 default: return false;
103 case Mips::Bimm16:
104 case Mips::BimmX16:
105 case Mips::JalB16:
106 return true;
107 }
108 }
109
longformBranchOpcode(unsigned int Opcode)110 static unsigned int longformBranchOpcode(unsigned int Opcode) {
111 switch (Opcode) {
112 case Mips::Bimm16:
113 case Mips::BimmX16:
114 return Mips::BimmX16;
115 case Mips::Bteqz16:
116 case Mips::BteqzX16:
117 return Mips::BteqzX16;
118 case Mips::Btnez16:
119 case Mips::BtnezX16:
120 return Mips::BtnezX16;
121 case Mips::JalB16:
122 return Mips::JalB16;
123 case Mips::BeqzRxImm16:
124 case Mips::BeqzRxImmX16:
125 return Mips::BeqzRxImmX16;
126 case Mips::BnezRxImm16:
127 case Mips::BnezRxImmX16:
128 return Mips::BnezRxImmX16;
129 }
130 llvm_unreachable("Unknown branch type");
131 }
132
133 //
134 // FIXME: need to go through this whole constant islands port and check the math
135 // for branch ranges and clean this up and make some functions to calculate things
136 // that are done many times identically.
137 // Need to refactor some of the code to call this routine.
138 //
branchMaxOffsets(unsigned int Opcode)139 static unsigned int branchMaxOffsets(unsigned int Opcode) {
140 unsigned Bits, Scale;
141 switch (Opcode) {
142 case Mips::Bimm16:
143 Bits = 11;
144 Scale = 2;
145 break;
146 case Mips::BimmX16:
147 Bits = 16;
148 Scale = 2;
149 break;
150 case Mips::BeqzRxImm16:
151 Bits = 8;
152 Scale = 2;
153 break;
154 case Mips::BeqzRxImmX16:
155 Bits = 16;
156 Scale = 2;
157 break;
158 case Mips::BnezRxImm16:
159 Bits = 8;
160 Scale = 2;
161 break;
162 case Mips::BnezRxImmX16:
163 Bits = 16;
164 Scale = 2;
165 break;
166 case Mips::Bteqz16:
167 Bits = 8;
168 Scale = 2;
169 break;
170 case Mips::BteqzX16:
171 Bits = 16;
172 Scale = 2;
173 break;
174 case Mips::Btnez16:
175 Bits = 8;
176 Scale = 2;
177 break;
178 case Mips::BtnezX16:
179 Bits = 16;
180 Scale = 2;
181 break;
182 default:
183 llvm_unreachable("Unknown branch type");
184 }
185 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
186 return MaxOffs;
187 }
188
189 namespace {
190
191
192 typedef MachineBasicBlock::iterator Iter;
193 typedef MachineBasicBlock::reverse_iterator ReverseIter;
194
195 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
196 /// requires constant pool entries to be scattered among the instructions
197 /// inside a function. To do this, it completely ignores the normal LLVM
198 /// constant pool; instead, it places constants wherever it feels like with
199 /// special instructions.
200 ///
201 /// The terminology used in this pass includes:
202 /// Islands - Clumps of constants placed in the function.
203 /// Water - Potential places where an island could be formed.
204 /// CPE - A constant pool entry that has been placed somewhere, which
205 /// tracks a list of users.
206
207 class MipsConstantIslands : public MachineFunctionPass {
208
209 /// BasicBlockInfo - Information about the offset and size of a single
210 /// basic block.
211 struct BasicBlockInfo {
212 /// Offset - Distance from the beginning of the function to the beginning
213 /// of this basic block.
214 ///
215 /// Offsets are computed assuming worst case padding before an aligned
216 /// block. This means that subtracting basic block offsets always gives a
217 /// conservative estimate of the real distance which may be smaller.
218 ///
219 /// Because worst case padding is used, the computed offset of an aligned
220 /// block may not actually be aligned.
221 unsigned Offset;
222
223 /// Size - Size of the basic block in bytes. If the block contains
224 /// inline assembly, this is a worst case estimate.
225 ///
226 /// The size does not include any alignment padding whether from the
227 /// beginning of the block, or from an aligned jump table at the end.
228 unsigned Size;
229
230 // FIXME: ignore LogAlign for this patch
231 //
postOffset__anon449aa4850111::MipsConstantIslands::BasicBlockInfo232 unsigned postOffset(unsigned LogAlign = 0) const {
233 unsigned PO = Offset + Size;
234 return PO;
235 }
236
BasicBlockInfo__anon449aa4850111::MipsConstantIslands::BasicBlockInfo237 BasicBlockInfo() : Offset(0), Size(0) {}
238
239 };
240
241 std::vector<BasicBlockInfo> BBInfo;
242
243 /// WaterList - A sorted list of basic blocks where islands could be placed
244 /// (i.e. blocks that don't fall through to the following block, due
245 /// to a return, unreachable, or unconditional branch).
246 std::vector<MachineBasicBlock*> WaterList;
247
248 /// NewWaterList - The subset of WaterList that was created since the
249 /// previous iteration by inserting unconditional branches.
250 SmallSet<MachineBasicBlock*, 4> NewWaterList;
251
252 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
253
254 /// CPUser - One user of a constant pool, keeping the machine instruction
255 /// pointer, the constant pool being referenced, and the max displacement
256 /// allowed from the instruction to the CP. The HighWaterMark records the
257 /// highest basic block where a new CPEntry can be placed. To ensure this
258 /// pass terminates, the CP entries are initially placed at the end of the
259 /// function and then move monotonically to lower addresses. The
260 /// exception to this rule is when the current CP entry for a particular
261 /// CPUser is out of range, but there is another CP entry for the same
262 /// constant value in range. We want to use the existing in-range CP
263 /// entry, but if it later moves out of range, the search for new water
264 /// should resume where it left off. The HighWaterMark is used to record
265 /// that point.
266 struct CPUser {
267 MachineInstr *MI;
268 MachineInstr *CPEMI;
269 MachineBasicBlock *HighWaterMark;
270 private:
271 unsigned MaxDisp;
272 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
273 // with different displacements
274 unsigned LongFormOpcode;
275 public:
276 bool NegOk;
CPUser__anon449aa4850111::MipsConstantIslands::CPUser277 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
278 bool neg,
279 unsigned longformmaxdisp, unsigned longformopcode)
280 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
281 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
282 NegOk(neg){
283 HighWaterMark = CPEMI->getParent();
284 }
285 /// getMaxDisp - Returns the maximum displacement supported by MI.
getMaxDisp__anon449aa4850111::MipsConstantIslands::CPUser286 unsigned getMaxDisp() const {
287 unsigned xMaxDisp = ConstantIslandsSmallOffset?
288 ConstantIslandsSmallOffset: MaxDisp;
289 return xMaxDisp;
290 }
setMaxDisp__anon449aa4850111::MipsConstantIslands::CPUser291 void setMaxDisp(unsigned val) {
292 MaxDisp = val;
293 }
getLongFormMaxDisp__anon449aa4850111::MipsConstantIslands::CPUser294 unsigned getLongFormMaxDisp() const {
295 return LongFormMaxDisp;
296 }
getLongFormOpcode__anon449aa4850111::MipsConstantIslands::CPUser297 unsigned getLongFormOpcode() const {
298 return LongFormOpcode;
299 }
300 };
301
302 /// CPUsers - Keep track of all of the machine instructions that use various
303 /// constant pools and their max displacement.
304 std::vector<CPUser> CPUsers;
305
306 /// CPEntry - One per constant pool entry, keeping the machine instruction
307 /// pointer, the constpool index, and the number of CPUser's which
308 /// reference this entry.
309 struct CPEntry {
310 MachineInstr *CPEMI;
311 unsigned CPI;
312 unsigned RefCount;
CPEntry__anon449aa4850111::MipsConstantIslands::CPEntry313 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
314 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
315 };
316
317 /// CPEntries - Keep track of all of the constant pool entry machine
318 /// instructions. For each original constpool index (i.e. those that
319 /// existed upon entry to this pass), it keeps a vector of entries.
320 /// Original elements are cloned as we go along; the clones are
321 /// put in the vector of the original element, but have distinct CPIs.
322 std::vector<std::vector<CPEntry> > CPEntries;
323
324 /// ImmBranch - One per immediate branch, keeping the machine instruction
325 /// pointer, conditional or unconditional, the max displacement,
326 /// and (if isCond is true) the corresponding unconditional branch
327 /// opcode.
328 struct ImmBranch {
329 MachineInstr *MI;
330 unsigned MaxDisp : 31;
331 bool isCond : 1;
332 int UncondBr;
ImmBranch__anon449aa4850111::MipsConstantIslands::ImmBranch333 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
334 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
335 };
336
337 /// ImmBranches - Keep track of all the immediate branch instructions.
338 ///
339 std::vector<ImmBranch> ImmBranches;
340
341 /// HasFarJump - True if any far jump instruction has been emitted during
342 /// the branch fix up pass.
343 bool HasFarJump;
344
345 const TargetMachine &TM;
346 bool IsPIC;
347 const MipsSubtarget *STI;
348 const Mips16InstrInfo *TII;
349 MipsFunctionInfo *MFI;
350 MachineFunction *MF;
351 MachineConstantPool *MCP;
352
353 unsigned PICLabelUId;
354 bool PrescannedForConstants;
355
initPICLabelUId(unsigned UId)356 void initPICLabelUId(unsigned UId) {
357 PICLabelUId = UId;
358 }
359
360
createPICLabelUId()361 unsigned createPICLabelUId() {
362 return PICLabelUId++;
363 }
364
365 public:
366 static char ID;
MipsConstantIslands(TargetMachine & tm)367 MipsConstantIslands(TargetMachine &tm)
368 : MachineFunctionPass(ID), TM(tm),
369 IsPIC(TM.getRelocationModel() == Reloc::PIC_), STI(nullptr),
370 MF(nullptr), MCP(nullptr), PrescannedForConstants(false) {}
371
getPassName() const372 const char *getPassName() const override {
373 return "Mips Constant Islands";
374 }
375
376 bool runOnMachineFunction(MachineFunction &F) override;
377
378 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
379 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
380 unsigned getCPELogAlign(const MachineInstr *CPEMI);
381 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
382 unsigned getOffsetOf(MachineInstr *MI) const;
383 unsigned getUserOffset(CPUser&) const;
384 void dumpBBs();
385
386 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
387 unsigned Disp, bool NegativeOK);
388 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
389 const CPUser &U);
390
391 void computeBlockSize(MachineBasicBlock *MBB);
392 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
393 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
394 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
395 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
396 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
397 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
398 bool findAvailableWater(CPUser&U, unsigned UserOffset,
399 water_iterator &WaterIter);
400 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
401 MachineBasicBlock *&NewMBB);
402 bool handleConstantPoolUser(unsigned CPUserIndex);
403 void removeDeadCPEMI(MachineInstr *CPEMI);
404 bool removeUnusedCPEntries();
405 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
406 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
407 bool DoDump = false);
408 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
409 CPUser &U, unsigned &Growth);
410 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
411 bool fixupImmediateBr(ImmBranch &Br);
412 bool fixupConditionalBr(ImmBranch &Br);
413 bool fixupUnconditionalBr(ImmBranch &Br);
414
415 void prescanForConstants();
416
417 private:
418
419 };
420
421 char MipsConstantIslands::ID = 0;
422 } // end of anonymous namespace
423
isOffsetInRange(unsigned UserOffset,unsigned TrialOffset,const CPUser & U)424 bool MipsConstantIslands::isOffsetInRange
425 (unsigned UserOffset, unsigned TrialOffset,
426 const CPUser &U) {
427 return isOffsetInRange(UserOffset, TrialOffset,
428 U.getMaxDisp(), U.NegOk);
429 }
430 /// print block size and offset information - debugging
dumpBBs()431 void MipsConstantIslands::dumpBBs() {
432 DEBUG({
433 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
434 const BasicBlockInfo &BBI = BBInfo[J];
435 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
436 << format(" size=%#x\n", BBInfo[J].Size);
437 }
438 });
439 }
440 /// createMipsLongBranchPass - Returns a pass that converts branches to long
441 /// branches.
createMipsConstantIslandPass(MipsTargetMachine & tm)442 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
443 return new MipsConstantIslands(tm);
444 }
445
runOnMachineFunction(MachineFunction & mf)446 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
447 // The intention is for this to be a mips16 only pass for now
448 // FIXME:
449 MF = &mf;
450 MCP = mf.getConstantPool();
451 STI = &static_cast<const MipsSubtarget &>(mf.getSubtarget());
452 DEBUG(dbgs() << "constant island machine function " << "\n");
453 if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) {
454 return false;
455 }
456 TII = (const Mips16InstrInfo *)STI->getInstrInfo();
457 MFI = MF->getInfo<MipsFunctionInfo>();
458 DEBUG(dbgs() << "constant island processing " << "\n");
459 //
460 // will need to make predermination if there is any constants we need to
461 // put in constant islands. TBD.
462 //
463 if (!PrescannedForConstants) prescanForConstants();
464
465 HasFarJump = false;
466 // This pass invalidates liveness information when it splits basic blocks.
467 MF->getRegInfo().invalidateLiveness();
468
469 // Renumber all of the machine basic blocks in the function, guaranteeing that
470 // the numbers agree with the position of the block in the function.
471 MF->RenumberBlocks();
472
473 bool MadeChange = false;
474
475 // Perform the initial placement of the constant pool entries. To start with,
476 // we put them all at the end of the function.
477 std::vector<MachineInstr*> CPEMIs;
478 if (!MCP->isEmpty())
479 doInitialPlacement(CPEMIs);
480
481 /// The next UID to take is the first unused one.
482 initPICLabelUId(CPEMIs.size());
483
484 // Do the initial scan of the function, building up information about the
485 // sizes of each block, the location of all the water, and finding all of the
486 // constant pool users.
487 initializeFunctionInfo(CPEMIs);
488 CPEMIs.clear();
489 DEBUG(dumpBBs());
490
491 /// Remove dead constant pool entries.
492 MadeChange |= removeUnusedCPEntries();
493
494 // Iteratively place constant pool entries and fix up branches until there
495 // is no change.
496 unsigned NoCPIters = 0, NoBRIters = 0;
497 (void)NoBRIters;
498 while (true) {
499 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
500 bool CPChange = false;
501 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
502 CPChange |= handleConstantPoolUser(i);
503 if (CPChange && ++NoCPIters > 30)
504 report_fatal_error("Constant Island pass failed to converge!");
505 DEBUG(dumpBBs());
506
507 // Clear NewWaterList now. If we split a block for branches, it should
508 // appear as "new water" for the next iteration of constant pool placement.
509 NewWaterList.clear();
510
511 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
512 bool BRChange = false;
513 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
514 BRChange |= fixupImmediateBr(ImmBranches[i]);
515 if (BRChange && ++NoBRIters > 30)
516 report_fatal_error("Branch Fix Up pass failed to converge!");
517 DEBUG(dumpBBs());
518 if (!CPChange && !BRChange)
519 break;
520 MadeChange = true;
521 }
522
523 DEBUG(dbgs() << '\n'; dumpBBs());
524
525 BBInfo.clear();
526 WaterList.clear();
527 CPUsers.clear();
528 CPEntries.clear();
529 ImmBranches.clear();
530 return MadeChange;
531 }
532
533 /// doInitialPlacement - Perform the initial placement of the constant pool
534 /// entries. To start with, we put them all at the end of the function.
535 void
doInitialPlacement(std::vector<MachineInstr * > & CPEMIs)536 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
537 // Create the basic block to hold the CPE's.
538 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
539 MF->push_back(BB);
540
541
542 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
543 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
544
545 // Mark the basic block as required by the const-pool.
546 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
547 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
548
549 // The function needs to be as aligned as the basic blocks. The linker may
550 // move functions around based on their alignment.
551 MF->ensureAlignment(BB->getAlignment());
552
553 // Order the entries in BB by descending alignment. That ensures correct
554 // alignment of all entries as long as BB is sufficiently aligned. Keep
555 // track of the insertion point for each alignment. We are going to bucket
556 // sort the entries as they are created.
557 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
558
559 // Add all of the constants from the constant pool to the end block, use an
560 // identity mapping of CPI's to CPE's.
561 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
562
563 const DataLayout &TD = MF->getDataLayout();
564 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
565 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
566 assert(Size >= 4 && "Too small constant pool entry");
567 unsigned Align = CPs[i].getAlignment();
568 assert(isPowerOf2_32(Align) && "Invalid alignment");
569 // Verify that all constant pool entries are a multiple of their alignment.
570 // If not, we would have to pad them out so that instructions stay aligned.
571 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
572
573 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
574 unsigned LogAlign = Log2_32(Align);
575 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
576
577 MachineInstr *CPEMI =
578 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
579 .addImm(i).addConstantPoolIndex(i).addImm(Size);
580
581 CPEMIs.push_back(CPEMI);
582
583 // Ensure that future entries with higher alignment get inserted before
584 // CPEMI. This is bucket sort with iterators.
585 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
586 if (InsPoint[a] == InsAt)
587 InsPoint[a] = CPEMI;
588 // Add a new CPEntry, but no corresponding CPUser yet.
589 CPEntries.emplace_back(1, CPEntry(CPEMI, i));
590 ++NumCPEs;
591 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
592 << Size << ", align = " << Align <<'\n');
593 }
594 DEBUG(BB->dump());
595 }
596
597 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
598 /// into the block immediately after it.
BBHasFallthrough(MachineBasicBlock * MBB)599 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
600 // Get the next machine basic block in the function.
601 MachineFunction::iterator MBBI = MBB->getIterator();
602 // Can't fall off end of function.
603 if (std::next(MBBI) == MBB->getParent()->end())
604 return false;
605
606 MachineBasicBlock *NextBB = &*std::next(MBBI);
607 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
608 E = MBB->succ_end(); I != E; ++I)
609 if (*I == NextBB)
610 return true;
611
612 return false;
613 }
614
615 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
616 /// look up the corresponding CPEntry.
617 MipsConstantIslands::CPEntry
findConstPoolEntry(unsigned CPI,const MachineInstr * CPEMI)618 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
619 const MachineInstr *CPEMI) {
620 std::vector<CPEntry> &CPEs = CPEntries[CPI];
621 // Number of entries per constpool index should be small, just do a
622 // linear search.
623 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
624 if (CPEs[i].CPEMI == CPEMI)
625 return &CPEs[i];
626 }
627 return nullptr;
628 }
629
630 /// getCPELogAlign - Returns the required alignment of the constant pool entry
631 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
getCPELogAlign(const MachineInstr * CPEMI)632 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
633 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
634
635 // Everything is 4-byte aligned unless AlignConstantIslands is set.
636 if (!AlignConstantIslands)
637 return 2;
638
639 unsigned CPI = CPEMI->getOperand(1).getIndex();
640 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
641 unsigned Align = MCP->getConstants()[CPI].getAlignment();
642 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
643 return Log2_32(Align);
644 }
645
646 /// initializeFunctionInfo - Do the initial scan of the function, building up
647 /// information about the sizes of each block, the location of all the water,
648 /// and finding all of the constant pool users.
649 void MipsConstantIslands::
initializeFunctionInfo(const std::vector<MachineInstr * > & CPEMIs)650 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
651 BBInfo.clear();
652 BBInfo.resize(MF->getNumBlockIDs());
653
654 // First thing, compute the size of all basic blocks, and see if the function
655 // has any inline assembly in it. If so, we have to be conservative about
656 // alignment assumptions, as we don't know for sure the size of any
657 // instructions in the inline assembly.
658 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
659 computeBlockSize(&*I);
660
661
662 // Compute block offsets.
663 adjustBBOffsetsAfter(&MF->front());
664
665 // Now go back through the instructions and build up our data structures.
666 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
667 MBBI != E; ++MBBI) {
668 MachineBasicBlock &MBB = *MBBI;
669
670 // If this block doesn't fall through into the next MBB, then this is
671 // 'water' that a constant pool island could be placed.
672 if (!BBHasFallthrough(&MBB))
673 WaterList.push_back(&MBB);
674 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
675 I != E; ++I) {
676 if (I->isDebugValue())
677 continue;
678
679 int Opc = I->getOpcode();
680 if (I->isBranch()) {
681 bool isCond = false;
682 unsigned Bits = 0;
683 unsigned Scale = 1;
684 int UOpc = Opc;
685 switch (Opc) {
686 default:
687 continue; // Ignore other branches for now
688 case Mips::Bimm16:
689 Bits = 11;
690 Scale = 2;
691 isCond = false;
692 break;
693 case Mips::BimmX16:
694 Bits = 16;
695 Scale = 2;
696 isCond = false;
697 break;
698 case Mips::BeqzRxImm16:
699 UOpc=Mips::Bimm16;
700 Bits = 8;
701 Scale = 2;
702 isCond = true;
703 break;
704 case Mips::BeqzRxImmX16:
705 UOpc=Mips::Bimm16;
706 Bits = 16;
707 Scale = 2;
708 isCond = true;
709 break;
710 case Mips::BnezRxImm16:
711 UOpc=Mips::Bimm16;
712 Bits = 8;
713 Scale = 2;
714 isCond = true;
715 break;
716 case Mips::BnezRxImmX16:
717 UOpc=Mips::Bimm16;
718 Bits = 16;
719 Scale = 2;
720 isCond = true;
721 break;
722 case Mips::Bteqz16:
723 UOpc=Mips::Bimm16;
724 Bits = 8;
725 Scale = 2;
726 isCond = true;
727 break;
728 case Mips::BteqzX16:
729 UOpc=Mips::Bimm16;
730 Bits = 16;
731 Scale = 2;
732 isCond = true;
733 break;
734 case Mips::Btnez16:
735 UOpc=Mips::Bimm16;
736 Bits = 8;
737 Scale = 2;
738 isCond = true;
739 break;
740 case Mips::BtnezX16:
741 UOpc=Mips::Bimm16;
742 Bits = 16;
743 Scale = 2;
744 isCond = true;
745 break;
746 }
747 // Record this immediate branch.
748 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
749 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
750 }
751
752 if (Opc == Mips::CONSTPOOL_ENTRY)
753 continue;
754
755
756 // Scan the instructions for constant pool operands.
757 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
758 if (I->getOperand(op).isCPI()) {
759
760 // We found one. The addressing mode tells us the max displacement
761 // from the PC that this instruction permits.
762
763 // Basic size info comes from the TSFlags field.
764 unsigned Bits = 0;
765 unsigned Scale = 1;
766 bool NegOk = false;
767 unsigned LongFormBits = 0;
768 unsigned LongFormScale = 0;
769 unsigned LongFormOpcode = 0;
770 switch (Opc) {
771 default:
772 llvm_unreachable("Unknown addressing mode for CP reference!");
773 case Mips::LwRxPcTcp16:
774 Bits = 8;
775 Scale = 4;
776 LongFormOpcode = Mips::LwRxPcTcpX16;
777 LongFormBits = 14;
778 LongFormScale = 1;
779 break;
780 case Mips::LwRxPcTcpX16:
781 Bits = 14;
782 Scale = 1;
783 NegOk = true;
784 break;
785 }
786 // Remember that this is a user of a CP entry.
787 unsigned CPI = I->getOperand(op).getIndex();
788 MachineInstr *CPEMI = CPEMIs[CPI];
789 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
790 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
791 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
792 LongFormMaxOffs, LongFormOpcode));
793
794 // Increment corresponding CPEntry reference count.
795 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
796 assert(CPE && "Cannot find a corresponding CPEntry!");
797 CPE->RefCount++;
798
799 // Instructions can only use one CP entry, don't bother scanning the
800 // rest of the operands.
801 break;
802
803 }
804
805 }
806 }
807
808 }
809
810 /// computeBlockSize - Compute the size and some alignment information for MBB.
811 /// This function updates BBInfo directly.
computeBlockSize(MachineBasicBlock * MBB)812 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
813 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
814 BBI.Size = 0;
815
816 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
817 ++I)
818 BBI.Size += TII->GetInstSizeInBytes(I);
819
820 }
821
822 /// getOffsetOf - Return the current offset of the specified machine instruction
823 /// from the start of the function. This offset changes as stuff is moved
824 /// around inside the function.
getOffsetOf(MachineInstr * MI) const825 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
826 MachineBasicBlock *MBB = MI->getParent();
827
828 // The offset is composed of two things: the sum of the sizes of all MBB's
829 // before this instruction's block, and the offset from the start of the block
830 // it is in.
831 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
832
833 // Sum instructions before MI in MBB.
834 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
835 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
836 Offset += TII->GetInstSizeInBytes(I);
837 }
838 return Offset;
839 }
840
841 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
842 /// ID.
CompareMBBNumbers(const MachineBasicBlock * LHS,const MachineBasicBlock * RHS)843 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
844 const MachineBasicBlock *RHS) {
845 return LHS->getNumber() < RHS->getNumber();
846 }
847
848 /// updateForInsertedWaterBlock - When a block is newly inserted into the
849 /// machine function, it upsets all of the block numbers. Renumber the blocks
850 /// and update the arrays that parallel this numbering.
updateForInsertedWaterBlock(MachineBasicBlock * NewBB)851 void MipsConstantIslands::updateForInsertedWaterBlock
852 (MachineBasicBlock *NewBB) {
853 // Renumber the MBB's to keep them consecutive.
854 NewBB->getParent()->RenumberBlocks(NewBB);
855
856 // Insert an entry into BBInfo to align it properly with the (newly
857 // renumbered) block numbers.
858 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
859
860 // Next, update WaterList. Specifically, we need to add NewMBB as having
861 // available water after it.
862 water_iterator IP =
863 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
864 CompareMBBNumbers);
865 WaterList.insert(IP, NewBB);
866 }
867
getUserOffset(CPUser & U) const868 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
869 return getOffsetOf(U.MI);
870 }
871
872 /// Split the basic block containing MI into two blocks, which are joined by
873 /// an unconditional branch. Update data structures and renumber blocks to
874 /// account for this change and returns the newly created block.
splitBlockBeforeInstr(MachineInstr * MI)875 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
876 (MachineInstr *MI) {
877 MachineBasicBlock *OrigBB = MI->getParent();
878
879 // Create a new MBB for the code after the OrigBB.
880 MachineBasicBlock *NewBB =
881 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
882 MachineFunction::iterator MBBI = ++OrigBB->getIterator();
883 MF->insert(MBBI, NewBB);
884
885 // Splice the instructions starting with MI over to NewBB.
886 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
887
888 // Add an unconditional branch from OrigBB to NewBB.
889 // Note the new unconditional branch is not being recorded.
890 // There doesn't seem to be meaningful DebugInfo available; this doesn't
891 // correspond to anything in the source.
892 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
893 ++NumSplit;
894
895 // Update the CFG. All succs of OrigBB are now succs of NewBB.
896 NewBB->transferSuccessors(OrigBB);
897
898 // OrigBB branches to NewBB.
899 OrigBB->addSuccessor(NewBB);
900
901 // Update internal data structures to account for the newly inserted MBB.
902 // This is almost the same as updateForInsertedWaterBlock, except that
903 // the Water goes after OrigBB, not NewBB.
904 MF->RenumberBlocks(NewBB);
905
906 // Insert an entry into BBInfo to align it properly with the (newly
907 // renumbered) block numbers.
908 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
909
910 // Next, update WaterList. Specifically, we need to add OrigMBB as having
911 // available water after it (but not if it's already there, which happens
912 // when splitting before a conditional branch that is followed by an
913 // unconditional branch - in that case we want to insert NewBB).
914 water_iterator IP =
915 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
916 CompareMBBNumbers);
917 MachineBasicBlock* WaterBB = *IP;
918 if (WaterBB == OrigBB)
919 WaterList.insert(std::next(IP), NewBB);
920 else
921 WaterList.insert(IP, OrigBB);
922 NewWaterList.insert(OrigBB);
923
924 // Figure out how large the OrigBB is. As the first half of the original
925 // block, it cannot contain a tablejump. The size includes
926 // the new jump we added. (It should be possible to do this without
927 // recounting everything, but it's very confusing, and this is rarely
928 // executed.)
929 computeBlockSize(OrigBB);
930
931 // Figure out how large the NewMBB is. As the second half of the original
932 // block, it may contain a tablejump.
933 computeBlockSize(NewBB);
934
935 // All BBOffsets following these blocks must be modified.
936 adjustBBOffsetsAfter(OrigBB);
937
938 return NewBB;
939 }
940
941
942
943 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
944 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
945 /// constant pool entry).
isOffsetInRange(unsigned UserOffset,unsigned TrialOffset,unsigned MaxDisp,bool NegativeOK)946 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
947 unsigned TrialOffset, unsigned MaxDisp,
948 bool NegativeOK) {
949 if (UserOffset <= TrialOffset) {
950 // User before the Trial.
951 if (TrialOffset - UserOffset <= MaxDisp)
952 return true;
953 } else if (NegativeOK) {
954 if (UserOffset - TrialOffset <= MaxDisp)
955 return true;
956 }
957 return false;
958 }
959
960 /// isWaterInRange - Returns true if a CPE placed after the specified
961 /// Water (a basic block) will be in range for the specific MI.
962 ///
963 /// Compute how much the function will grow by inserting a CPE after Water.
isWaterInRange(unsigned UserOffset,MachineBasicBlock * Water,CPUser & U,unsigned & Growth)964 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
965 MachineBasicBlock* Water, CPUser &U,
966 unsigned &Growth) {
967 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
968 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
969 unsigned NextBlockOffset, NextBlockAlignment;
970 MachineFunction::const_iterator NextBlock = ++Water->getIterator();
971 if (NextBlock == MF->end()) {
972 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
973 NextBlockAlignment = 0;
974 } else {
975 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
976 NextBlockAlignment = NextBlock->getAlignment();
977 }
978 unsigned Size = U.CPEMI->getOperand(2).getImm();
979 unsigned CPEEnd = CPEOffset + Size;
980
981 // The CPE may be able to hide in the alignment padding before the next
982 // block. It may also cause more padding to be required if it is more aligned
983 // that the next block.
984 if (CPEEnd > NextBlockOffset) {
985 Growth = CPEEnd - NextBlockOffset;
986 // Compute the padding that would go at the end of the CPE to align the next
987 // block.
988 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
989
990 // If the CPE is to be inserted before the instruction, that will raise
991 // the offset of the instruction. Also account for unknown alignment padding
992 // in blocks between CPE and the user.
993 if (CPEOffset < UserOffset)
994 UserOffset += Growth;
995 } else
996 // CPE fits in existing padding.
997 Growth = 0;
998
999 return isOffsetInRange(UserOffset, CPEOffset, U);
1000 }
1001
1002 /// isCPEntryInRange - Returns true if the distance between specific MI and
1003 /// specific ConstPool entry instruction can fit in MI's displacement field.
isCPEntryInRange(MachineInstr * MI,unsigned UserOffset,MachineInstr * CPEMI,unsigned MaxDisp,bool NegOk,bool DoDump)1004 bool MipsConstantIslands::isCPEntryInRange
1005 (MachineInstr *MI, unsigned UserOffset,
1006 MachineInstr *CPEMI, unsigned MaxDisp,
1007 bool NegOk, bool DoDump) {
1008 unsigned CPEOffset = getOffsetOf(CPEMI);
1009
1010 if (DoDump) {
1011 DEBUG({
1012 unsigned Block = MI->getParent()->getNumber();
1013 const BasicBlockInfo &BBI = BBInfo[Block];
1014 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
1015 << " max delta=" << MaxDisp
1016 << format(" insn address=%#x", UserOffset)
1017 << " in BB#" << Block << ": "
1018 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
1019 << format("CPE address=%#x offset=%+d: ", CPEOffset,
1020 int(CPEOffset-UserOffset));
1021 });
1022 }
1023
1024 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
1025 }
1026
1027 #ifndef NDEBUG
1028 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
1029 /// unconditionally branches to its only successor.
BBIsJumpedOver(MachineBasicBlock * MBB)1030 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
1031 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
1032 return false;
1033 MachineBasicBlock *Succ = *MBB->succ_begin();
1034 MachineBasicBlock *Pred = *MBB->pred_begin();
1035 MachineInstr *PredMI = &Pred->back();
1036 if (PredMI->getOpcode() == Mips::Bimm16)
1037 return PredMI->getOperand(0).getMBB() == Succ;
1038 return false;
1039 }
1040 #endif
1041
adjustBBOffsetsAfter(MachineBasicBlock * BB)1042 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
1043 unsigned BBNum = BB->getNumber();
1044 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
1045 // Get the offset and known bits at the end of the layout predecessor.
1046 // Include the alignment of the current block.
1047 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
1048 BBInfo[i].Offset = Offset;
1049 }
1050 }
1051
1052 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
1053 /// and instruction CPEMI, and decrement its refcount. If the refcount
1054 /// becomes 0 remove the entry and instruction. Returns true if we removed
1055 /// the entry, false if we didn't.
1056
decrementCPEReferenceCount(unsigned CPI,MachineInstr * CPEMI)1057 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
1058 MachineInstr *CPEMI) {
1059 // Find the old entry. Eliminate it if it is no longer used.
1060 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
1061 assert(CPE && "Unexpected!");
1062 if (--CPE->RefCount == 0) {
1063 removeDeadCPEMI(CPEMI);
1064 CPE->CPEMI = nullptr;
1065 --NumCPEs;
1066 return true;
1067 }
1068 return false;
1069 }
1070
1071 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1072 /// if not, see if an in-range clone of the CPE is in range, and if so,
1073 /// change the data structures so the user references the clone. Returns:
1074 /// 0 = no existing entry found
1075 /// 1 = entry found, and there were no code insertions or deletions
1076 /// 2 = entry found, and there were code insertions or deletions
findInRangeCPEntry(CPUser & U,unsigned UserOffset)1077 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1078 {
1079 MachineInstr *UserMI = U.MI;
1080 MachineInstr *CPEMI = U.CPEMI;
1081
1082 // Check to see if the CPE is already in-range.
1083 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1084 true)) {
1085 DEBUG(dbgs() << "In range\n");
1086 return 1;
1087 }
1088
1089 // No. Look for previously created clones of the CPE that are in range.
1090 unsigned CPI = CPEMI->getOperand(1).getIndex();
1091 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1092 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1093 // We already tried this one
1094 if (CPEs[i].CPEMI == CPEMI)
1095 continue;
1096 // Removing CPEs can leave empty entries, skip
1097 if (CPEs[i].CPEMI == nullptr)
1098 continue;
1099 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1100 U.NegOk)) {
1101 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1102 << CPEs[i].CPI << "\n");
1103 // Point the CPUser node to the replacement
1104 U.CPEMI = CPEs[i].CPEMI;
1105 // Change the CPI in the instruction operand to refer to the clone.
1106 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1107 if (UserMI->getOperand(j).isCPI()) {
1108 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1109 break;
1110 }
1111 // Adjust the refcount of the clone...
1112 CPEs[i].RefCount++;
1113 // ...and the original. If we didn't remove the old entry, none of the
1114 // addresses changed, so we don't need another pass.
1115 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1116 }
1117 }
1118 return 0;
1119 }
1120
1121 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1122 /// This version checks if the longer form of the instruction can be used to
1123 /// to satisfy things.
1124 /// if not, see if an in-range clone of the CPE is in range, and if so,
1125 /// change the data structures so the user references the clone. Returns:
1126 /// 0 = no existing entry found
1127 /// 1 = entry found, and there were no code insertions or deletions
1128 /// 2 = entry found, and there were code insertions or deletions
findLongFormInRangeCPEntry(CPUser & U,unsigned UserOffset)1129 int MipsConstantIslands::findLongFormInRangeCPEntry
1130 (CPUser& U, unsigned UserOffset)
1131 {
1132 MachineInstr *UserMI = U.MI;
1133 MachineInstr *CPEMI = U.CPEMI;
1134
1135 // Check to see if the CPE is already in-range.
1136 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1137 U.getLongFormMaxDisp(), U.NegOk,
1138 true)) {
1139 DEBUG(dbgs() << "In range\n");
1140 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1141 U.setMaxDisp(U.getLongFormMaxDisp());
1142 return 2; // instruction is longer length now
1143 }
1144
1145 // No. Look for previously created clones of the CPE that are in range.
1146 unsigned CPI = CPEMI->getOperand(1).getIndex();
1147 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1148 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1149 // We already tried this one
1150 if (CPEs[i].CPEMI == CPEMI)
1151 continue;
1152 // Removing CPEs can leave empty entries, skip
1153 if (CPEs[i].CPEMI == nullptr)
1154 continue;
1155 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1156 U.getLongFormMaxDisp(), U.NegOk)) {
1157 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1158 << CPEs[i].CPI << "\n");
1159 // Point the CPUser node to the replacement
1160 U.CPEMI = CPEs[i].CPEMI;
1161 // Change the CPI in the instruction operand to refer to the clone.
1162 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1163 if (UserMI->getOperand(j).isCPI()) {
1164 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1165 break;
1166 }
1167 // Adjust the refcount of the clone...
1168 CPEs[i].RefCount++;
1169 // ...and the original. If we didn't remove the old entry, none of the
1170 // addresses changed, so we don't need another pass.
1171 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1172 }
1173 }
1174 return 0;
1175 }
1176
1177 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1178 /// the specific unconditional branch instruction.
getUnconditionalBrDisp(int Opc)1179 static inline unsigned getUnconditionalBrDisp(int Opc) {
1180 switch (Opc) {
1181 case Mips::Bimm16:
1182 return ((1<<10)-1)*2;
1183 case Mips::BimmX16:
1184 return ((1<<16)-1)*2;
1185 default:
1186 break;
1187 }
1188 return ((1<<16)-1)*2;
1189 }
1190
1191 /// findAvailableWater - Look for an existing entry in the WaterList in which
1192 /// we can place the CPE referenced from U so it's within range of U's MI.
1193 /// Returns true if found, false if not. If it returns true, WaterIter
1194 /// is set to the WaterList entry.
1195 /// To ensure that this pass
1196 /// terminates, the CPE location for a particular CPUser is only allowed to
1197 /// move to a lower address, so search backward from the end of the list and
1198 /// prefer the first water that is in range.
findAvailableWater(CPUser & U,unsigned UserOffset,water_iterator & WaterIter)1199 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1200 water_iterator &WaterIter) {
1201 if (WaterList.empty())
1202 return false;
1203
1204 unsigned BestGrowth = ~0u;
1205 for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();;
1206 --IP) {
1207 MachineBasicBlock* WaterBB = *IP;
1208 // Check if water is in range and is either at a lower address than the
1209 // current "high water mark" or a new water block that was created since
1210 // the previous iteration by inserting an unconditional branch. In the
1211 // latter case, we want to allow resetting the high water mark back to
1212 // this new water since we haven't seen it before. Inserting branches
1213 // should be relatively uncommon and when it does happen, we want to be
1214 // sure to take advantage of it for all the CPEs near that block, so that
1215 // we don't insert more branches than necessary.
1216 unsigned Growth;
1217 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1218 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1219 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1220 // This is the least amount of required padding seen so far.
1221 BestGrowth = Growth;
1222 WaterIter = IP;
1223 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1224 << " Growth=" << Growth << '\n');
1225
1226 // Keep looking unless it is perfect.
1227 if (BestGrowth == 0)
1228 return true;
1229 }
1230 if (IP == B)
1231 break;
1232 }
1233 return BestGrowth != ~0u;
1234 }
1235
1236 /// createNewWater - No existing WaterList entry will work for
1237 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1238 /// block is used if in range, and the conditional branch munged so control
1239 /// flow is correct. Otherwise the block is split to create a hole with an
1240 /// unconditional branch around it. In either case NewMBB is set to a
1241 /// block following which the new island can be inserted (the WaterList
1242 /// is not adjusted).
createNewWater(unsigned CPUserIndex,unsigned UserOffset,MachineBasicBlock * & NewMBB)1243 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1244 unsigned UserOffset,
1245 MachineBasicBlock *&NewMBB) {
1246 CPUser &U = CPUsers[CPUserIndex];
1247 MachineInstr *UserMI = U.MI;
1248 MachineInstr *CPEMI = U.CPEMI;
1249 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1250 MachineBasicBlock *UserMBB = UserMI->getParent();
1251 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1252
1253 // If the block does not end in an unconditional branch already, and if the
1254 // end of the block is within range, make new water there.
1255 if (BBHasFallthrough(UserMBB)) {
1256 // Size of branch to insert.
1257 unsigned Delta = 2;
1258 // Compute the offset where the CPE will begin.
1259 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1260
1261 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1262 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1263 << format(", expected CPE offset %#x\n", CPEOffset));
1264 NewMBB = &*++UserMBB->getIterator();
1265 // Add an unconditional branch from UserMBB to fallthrough block. Record
1266 // it for branch lengthening; this new branch will not get out of range,
1267 // but if the preceding conditional branch is out of range, the targets
1268 // will be exchanged, and the altered branch may be out of range, so the
1269 // machinery has to know about it.
1270 int UncondBr = Mips::Bimm16;
1271 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1272 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1273 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1274 MaxDisp, false, UncondBr));
1275 BBInfo[UserMBB->getNumber()].Size += Delta;
1276 adjustBBOffsetsAfter(UserMBB);
1277 return;
1278 }
1279 }
1280
1281 // What a big block. Find a place within the block to split it.
1282
1283 // Try to split the block so it's fully aligned. Compute the latest split
1284 // point where we can add a 4-byte branch instruction, and then align to
1285 // LogAlign which is the largest possible alignment in the function.
1286 unsigned LogAlign = MF->getAlignment();
1287 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1288 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1289 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1290 BaseInsertOffset));
1291
1292 // The 4 in the following is for the unconditional branch we'll be inserting
1293 // Alignment of the island is handled
1294 // inside isOffsetInRange.
1295 BaseInsertOffset -= 4;
1296
1297 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1298 << " la=" << LogAlign << '\n');
1299
1300 // This could point off the end of the block if we've already got constant
1301 // pool entries following this block; only the last one is in the water list.
1302 // Back past any possible branches (allow for a conditional and a maximally
1303 // long unconditional).
1304 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1305 BaseInsertOffset = UserBBI.postOffset() - 8;
1306 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1307 }
1308 unsigned EndInsertOffset = BaseInsertOffset + 4 +
1309 CPEMI->getOperand(2).getImm();
1310 MachineBasicBlock::iterator MI = UserMI;
1311 ++MI;
1312 unsigned CPUIndex = CPUserIndex+1;
1313 unsigned NumCPUsers = CPUsers.size();
1314 //MachineInstr *LastIT = 0;
1315 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1316 Offset < BaseInsertOffset;
1317 Offset += TII->GetInstSizeInBytes(MI), MI = std::next(MI)) {
1318 assert(MI != UserMBB->end() && "Fell off end of block");
1319 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1320 CPUser &U = CPUsers[CPUIndex];
1321 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1322 // Shift intertion point by one unit of alignment so it is within reach.
1323 BaseInsertOffset -= 1u << LogAlign;
1324 EndInsertOffset -= 1u << LogAlign;
1325 }
1326 // This is overly conservative, as we don't account for CPEMIs being
1327 // reused within the block, but it doesn't matter much. Also assume CPEs
1328 // are added in order with alignment padding. We may eventually be able
1329 // to pack the aligned CPEs better.
1330 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1331 CPUIndex++;
1332 }
1333 }
1334
1335 --MI;
1336 NewMBB = splitBlockBeforeInstr(MI);
1337 }
1338
1339 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1340 /// is out-of-range. If so, pick up the constant pool value and move it some
1341 /// place in-range. Return true if we changed any addresses (thus must run
1342 /// another pass of branch lengthening), false otherwise.
handleConstantPoolUser(unsigned CPUserIndex)1343 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1344 CPUser &U = CPUsers[CPUserIndex];
1345 MachineInstr *UserMI = U.MI;
1346 MachineInstr *CPEMI = U.CPEMI;
1347 unsigned CPI = CPEMI->getOperand(1).getIndex();
1348 unsigned Size = CPEMI->getOperand(2).getImm();
1349 // Compute this only once, it's expensive.
1350 unsigned UserOffset = getUserOffset(U);
1351
1352 // See if the current entry is within range, or there is a clone of it
1353 // in range.
1354 int result = findInRangeCPEntry(U, UserOffset);
1355 if (result==1) return false;
1356 else if (result==2) return true;
1357
1358
1359 // Look for water where we can place this CPE.
1360 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1361 MachineBasicBlock *NewMBB;
1362 water_iterator IP;
1363 if (findAvailableWater(U, UserOffset, IP)) {
1364 DEBUG(dbgs() << "Found water in range\n");
1365 MachineBasicBlock *WaterBB = *IP;
1366
1367 // If the original WaterList entry was "new water" on this iteration,
1368 // propagate that to the new island. This is just keeping NewWaterList
1369 // updated to match the WaterList, which will be updated below.
1370 if (NewWaterList.erase(WaterBB))
1371 NewWaterList.insert(NewIsland);
1372
1373 // The new CPE goes before the following block (NewMBB).
1374 NewMBB = &*++WaterBB->getIterator();
1375 } else {
1376 // No water found.
1377 // we first see if a longer form of the instrucion could have reached
1378 // the constant. in that case we won't bother to split
1379 if (!NoLoadRelaxation) {
1380 result = findLongFormInRangeCPEntry(U, UserOffset);
1381 if (result != 0) return true;
1382 }
1383 DEBUG(dbgs() << "No water found\n");
1384 createNewWater(CPUserIndex, UserOffset, NewMBB);
1385
1386 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1387 // called while handling branches so that the water will be seen on the
1388 // next iteration for constant pools, but in this context, we don't want
1389 // it. Check for this so it will be removed from the WaterList.
1390 // Also remove any entry from NewWaterList.
1391 MachineBasicBlock *WaterBB = &*--NewMBB->getIterator();
1392 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1393 if (IP != WaterList.end())
1394 NewWaterList.erase(WaterBB);
1395
1396 // We are adding new water. Update NewWaterList.
1397 NewWaterList.insert(NewIsland);
1398 }
1399
1400 // Remove the original WaterList entry; we want subsequent insertions in
1401 // this vicinity to go after the one we're about to insert. This
1402 // considerably reduces the number of times we have to move the same CPE
1403 // more than once and is also important to ensure the algorithm terminates.
1404 if (IP != WaterList.end())
1405 WaterList.erase(IP);
1406
1407 // Okay, we know we can put an island before NewMBB now, do it!
1408 MF->insert(NewMBB->getIterator(), NewIsland);
1409
1410 // Update internal data structures to account for the newly inserted MBB.
1411 updateForInsertedWaterBlock(NewIsland);
1412
1413 // Decrement the old entry, and remove it if refcount becomes 0.
1414 decrementCPEReferenceCount(CPI, CPEMI);
1415
1416 // No existing clone of this CPE is within range.
1417 // We will be generating a new clone. Get a UID for it.
1418 unsigned ID = createPICLabelUId();
1419
1420 // Now that we have an island to add the CPE to, clone the original CPE and
1421 // add it to the island.
1422 U.HighWaterMark = NewIsland;
1423 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1424 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1425 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1426 ++NumCPEs;
1427
1428 // Mark the basic block as aligned as required by the const-pool entry.
1429 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1430
1431 // Increase the size of the island block to account for the new entry.
1432 BBInfo[NewIsland->getNumber()].Size += Size;
1433 adjustBBOffsetsAfter(&*--NewIsland->getIterator());
1434
1435 // Finally, change the CPI in the instruction operand to be ID.
1436 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1437 if (UserMI->getOperand(i).isCPI()) {
1438 UserMI->getOperand(i).setIndex(ID);
1439 break;
1440 }
1441
1442 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1443 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1444
1445 return true;
1446 }
1447
1448 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1449 /// sizes and offsets of impacted basic blocks.
removeDeadCPEMI(MachineInstr * CPEMI)1450 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1451 MachineBasicBlock *CPEBB = CPEMI->getParent();
1452 unsigned Size = CPEMI->getOperand(2).getImm();
1453 CPEMI->eraseFromParent();
1454 BBInfo[CPEBB->getNumber()].Size -= Size;
1455 // All succeeding offsets have the current size value added in, fix this.
1456 if (CPEBB->empty()) {
1457 BBInfo[CPEBB->getNumber()].Size = 0;
1458
1459 // This block no longer needs to be aligned.
1460 CPEBB->setAlignment(0);
1461 } else
1462 // Entries are sorted by descending alignment, so realign from the front.
1463 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1464
1465 adjustBBOffsetsAfter(CPEBB);
1466 // An island has only one predecessor BB and one successor BB. Check if
1467 // this BB's predecessor jumps directly to this BB's successor. This
1468 // shouldn't happen currently.
1469 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1470 // FIXME: remove the empty blocks after all the work is done?
1471 }
1472
1473 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1474 /// are zero.
removeUnusedCPEntries()1475 bool MipsConstantIslands::removeUnusedCPEntries() {
1476 unsigned MadeChange = false;
1477 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1478 std::vector<CPEntry> &CPEs = CPEntries[i];
1479 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1480 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1481 removeDeadCPEMI(CPEs[j].CPEMI);
1482 CPEs[j].CPEMI = nullptr;
1483 MadeChange = true;
1484 }
1485 }
1486 }
1487 return MadeChange;
1488 }
1489
1490 /// isBBInRange - Returns true if the distance between specific MI and
1491 /// specific BB can fit in MI's displacement field.
isBBInRange(MachineInstr * MI,MachineBasicBlock * DestBB,unsigned MaxDisp)1492 bool MipsConstantIslands::isBBInRange
1493 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1494
1495 unsigned PCAdj = 4;
1496
1497 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1498 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1499
1500 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1501 << " from BB#" << MI->getParent()->getNumber()
1502 << " max delta=" << MaxDisp
1503 << " from " << getOffsetOf(MI) << " to " << DestOffset
1504 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1505
1506 if (BrOffset <= DestOffset) {
1507 // Branch before the Dest.
1508 if (DestOffset-BrOffset <= MaxDisp)
1509 return true;
1510 } else {
1511 if (BrOffset-DestOffset <= MaxDisp)
1512 return true;
1513 }
1514 return false;
1515 }
1516
1517 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1518 /// away to fit in its displacement field.
fixupImmediateBr(ImmBranch & Br)1519 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1520 MachineInstr *MI = Br.MI;
1521 unsigned TargetOperand = branchTargetOperand(MI);
1522 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1523
1524 // Check to see if the DestBB is already in-range.
1525 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1526 return false;
1527
1528 if (!Br.isCond)
1529 return fixupUnconditionalBr(Br);
1530 return fixupConditionalBr(Br);
1531 }
1532
1533 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1534 /// too far away to fit in its displacement field. If the LR register has been
1535 /// spilled in the epilogue, then we can use BL to implement a far jump.
1536 /// Otherwise, add an intermediate branch instruction to a branch.
1537 bool
fixupUnconditionalBr(ImmBranch & Br)1538 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1539 MachineInstr *MI = Br.MI;
1540 MachineBasicBlock *MBB = MI->getParent();
1541 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1542 // Use BL to implement far jump.
1543 unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2;
1544 if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) {
1545 Br.MaxDisp = BimmX16MaxDisp;
1546 MI->setDesc(TII->get(Mips::BimmX16));
1547 }
1548 else {
1549 // need to give the math a more careful look here
1550 // this is really a segment address and not
1551 // a PC relative address. FIXME. But I think that
1552 // just reducing the bits by 1 as I've done is correct.
1553 // The basic block we are branching too much be longword aligned.
1554 // we know that RA is saved because we always save it right now.
1555 // this requirement will be relaxed later but we also have an alternate
1556 // way to implement this that I will implement that does not need jal.
1557 // We should have a way to back out this alignment restriction if we "can" later.
1558 // but it is not harmful.
1559 //
1560 DestBB->setAlignment(2);
1561 Br.MaxDisp = ((1<<24)-1) * 2;
1562 MI->setDesc(TII->get(Mips::JalB16));
1563 }
1564 BBInfo[MBB->getNumber()].Size += 2;
1565 adjustBBOffsetsAfter(MBB);
1566 HasFarJump = true;
1567 ++NumUBrFixed;
1568
1569 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1570
1571 return true;
1572 }
1573
1574
1575 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1576 /// far away to fit in its displacement field. It is converted to an inverse
1577 /// conditional branch + an unconditional branch to the destination.
1578 bool
fixupConditionalBr(ImmBranch & Br)1579 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1580 MachineInstr *MI = Br.MI;
1581 unsigned TargetOperand = branchTargetOperand(MI);
1582 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1583 unsigned Opcode = MI->getOpcode();
1584 unsigned LongFormOpcode = longformBranchOpcode(Opcode);
1585 unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
1586
1587 // Check to see if the DestBB is already in-range.
1588 if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
1589 Br.MaxDisp = LongFormMaxOff;
1590 MI->setDesc(TII->get(LongFormOpcode));
1591 return true;
1592 }
1593
1594 // Add an unconditional branch to the destination and invert the branch
1595 // condition to jump over it:
1596 // bteqz L1
1597 // =>
1598 // bnez L2
1599 // b L1
1600 // L2:
1601
1602 // If the branch is at the end of its MBB and that has a fall-through block,
1603 // direct the updated conditional branch to the fall-through block. Otherwise,
1604 // split the MBB before the next instruction.
1605 MachineBasicBlock *MBB = MI->getParent();
1606 MachineInstr *BMI = &MBB->back();
1607 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1608 unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode);
1609
1610 ++NumCBrFixed;
1611 if (BMI != MI) {
1612 if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) &&
1613 isUnconditionalBranch(BMI->getOpcode())) {
1614 // Last MI in the BB is an unconditional branch. Can we simply invert the
1615 // condition and swap destinations:
1616 // beqz L1
1617 // b L2
1618 // =>
1619 // bnez L2
1620 // b L1
1621 unsigned BMITargetOperand = branchTargetOperand(BMI);
1622 MachineBasicBlock *NewDest =
1623 BMI->getOperand(BMITargetOperand).getMBB();
1624 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1625 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1626 << *BMI);
1627 MI->setDesc(TII->get(OppositeBranchOpcode));
1628 BMI->getOperand(BMITargetOperand).setMBB(DestBB);
1629 MI->getOperand(TargetOperand).setMBB(NewDest);
1630 return true;
1631 }
1632 }
1633 }
1634
1635
1636 if (NeedSplit) {
1637 splitBlockBeforeInstr(MI);
1638 // No need for the branch to the next block. We're adding an unconditional
1639 // branch to the destination.
1640 int delta = TII->GetInstSizeInBytes(&MBB->back());
1641 BBInfo[MBB->getNumber()].Size -= delta;
1642 MBB->back().eraseFromParent();
1643 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1644 }
1645 MachineBasicBlock *NextBB = &*++MBB->getIterator();
1646
1647 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1648 << " also invert condition and change dest. to BB#"
1649 << NextBB->getNumber() << "\n");
1650
1651 // Insert a new conditional branch and a new unconditional branch.
1652 // Also update the ImmBranch as well as adding a new entry for the new branch.
1653 if (MI->getNumExplicitOperands() == 2) {
1654 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1655 .addReg(MI->getOperand(0).getReg())
1656 .addMBB(NextBB);
1657 } else {
1658 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1659 .addMBB(NextBB);
1660 }
1661 Br.MI = &MBB->back();
1662 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1663 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1664 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1665 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1666 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1667
1668 // Remove the old conditional branch. It may or may not still be in MBB.
1669 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1670 MI->eraseFromParent();
1671 adjustBBOffsetsAfter(MBB);
1672 return true;
1673 }
1674
1675
prescanForConstants()1676 void MipsConstantIslands::prescanForConstants() {
1677 unsigned J = 0;
1678 (void)J;
1679 for (MachineFunction::iterator B =
1680 MF->begin(), E = MF->end(); B != E; ++B) {
1681 for (MachineBasicBlock::instr_iterator I =
1682 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1683 switch(I->getDesc().getOpcode()) {
1684 case Mips::LwConstant32: {
1685 PrescannedForConstants = true;
1686 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1687 J = I->getNumOperands();
1688 DEBUG(dbgs() << "num operands " << J << "\n");
1689 MachineOperand& Literal = I->getOperand(1);
1690 if (Literal.isImm()) {
1691 int64_t V = Literal.getImm();
1692 DEBUG(dbgs() << "literal " << V << "\n");
1693 Type *Int32Ty =
1694 Type::getInt32Ty(MF->getFunction()->getContext());
1695 const Constant *C = ConstantInt::get(Int32Ty, V);
1696 unsigned index = MCP->getConstantPoolIndex(C, 4);
1697 I->getOperand(2).ChangeToImmediate(index);
1698 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1699 I->setDesc(TII->get(Mips::LwRxPcTcp16));
1700 I->RemoveOperand(1);
1701 I->RemoveOperand(1);
1702 I->addOperand(MachineOperand::CreateCPI(index, 0));
1703 I->addOperand(MachineOperand::CreateImm(4));
1704 }
1705 break;
1706 }
1707 default:
1708 break;
1709 }
1710 }
1711 }
1712 }
1713
1714