1//===- CSKYConstantIslandPass.cpp - Emit PC Relative loads ----------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9//
10// Loading constants inline is expensive on CSKY and it's in general better
11// to place the constant nearby in code space and then it can be loaded with a
12// simple 16/32 bit load instruction like lrw.
13//
14// The constants can be not just numbers but addresses of functions and labels.
15// This can be particularly helpful in static relocation mode for embedded
16// non-linux targets.
17//
18//===----------------------------------------------------------------------===//
19
20#include "CSKY.h"
21#include "CSKYConstantPoolValue.h"
22#include "CSKYMachineFunctionInfo.h"
23#include "CSKYSubtarget.h"
24#include "llvm/ADT/STLExtras.h"
25#include "llvm/ADT/SmallSet.h"
26#include "llvm/ADT/SmallVector.h"
27#include "llvm/ADT/Statistic.h"
28#include "llvm/ADT/StringRef.h"
29#include "llvm/CodeGen/MachineBasicBlock.h"
30#include "llvm/CodeGen/MachineConstantPool.h"
31#include "llvm/CodeGen/MachineDominators.h"
32#include "llvm/CodeGen/MachineFrameInfo.h"
33#include "llvm/CodeGen/MachineFunction.h"
34#include "llvm/CodeGen/MachineFunctionPass.h"
35#include "llvm/CodeGen/MachineInstr.h"
36#include "llvm/CodeGen/MachineInstrBuilder.h"
37#include "llvm/CodeGen/MachineOperand.h"
38#include "llvm/CodeGen/MachineRegisterInfo.h"
39#include "llvm/Config/llvm-config.h"
40#include "llvm/IR/Constants.h"
41#include "llvm/IR/DataLayout.h"
42#include "llvm/IR/DebugLoc.h"
43#include "llvm/IR/Function.h"
44#include "llvm/IR/Type.h"
45#include "llvm/Support/CommandLine.h"
46#include "llvm/Support/Compiler.h"
47#include "llvm/Support/Debug.h"
48#include "llvm/Support/ErrorHandling.h"
49#include "llvm/Support/Format.h"
50#include "llvm/Support/MathExtras.h"
51#include "llvm/Support/raw_ostream.h"
52#include <algorithm>
53#include <cassert>
54#include <cstdint>
55#include <iterator>
56#include <vector>
57
58using namespace llvm;
59
60#define DEBUG_TYPE "CSKY-constant-islands"
61
62STATISTIC(NumCPEs, "Number of constpool entries");
63STATISTIC(NumSplit, "Number of uncond branches inserted");
64STATISTIC(NumCBrFixed, "Number of cond branches fixed");
65STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
66
67namespace {
68
69using Iter = MachineBasicBlock::iterator;
70using ReverseIter = MachineBasicBlock::reverse_iterator;
71
72/// CSKYConstantIslands - Due to limited PC-relative displacements, CSKY
73/// requires constant pool entries to be scattered among the instructions
74/// inside a function. To do this, it completely ignores the normal LLVM
75/// constant pool; instead, it places constants wherever it feels like with
76/// special instructions.
77///
78/// The terminology used in this pass includes:
79/// Islands - Clumps of constants placed in the function.
80/// Water - Potential places where an island could be formed.
81/// CPE - A constant pool entry that has been placed somewhere, which
82/// tracks a list of users.
83
84class CSKYConstantIslands : public MachineFunctionPass {
85 /// BasicBlockInfo - Information about the offset and size of a single
86 /// basic block.
87 struct BasicBlockInfo {
88 /// Offset - Distance from the beginning of the function to the beginning
89 /// of this basic block.
90 ///
91 /// Offsets are computed assuming worst case padding before an aligned
92 /// block. This means that subtracting basic block offsets always gives a
93 /// conservative estimate of the real distance which may be smaller.
94 ///
95 /// Because worst case padding is used, the computed offset of an aligned
96 /// block may not actually be aligned.
97 unsigned Offset = 0;
98
99 /// Size - Size of the basic block in bytes. If the block contains
100 /// inline assembly, this is a worst case estimate.
101 ///
102 /// The size does not include any alignment padding whether from the
103 /// beginning of the block, or from an aligned jump table at the end.
104 unsigned Size = 0;
105
106 BasicBlockInfo() = default;
107
108 unsigned postOffset() const { return Offset + Size; }
109 };
110
111 std::vector<BasicBlockInfo> BBInfo;
112
113 /// WaterList - A sorted list of basic blocks where islands could be placed
114 /// (i.e. blocks that don't fall through to the following block, due
115 /// to a return, unreachable, or unconditional branch).
116 std::vector<MachineBasicBlock *> WaterList;
117
118 /// NewWaterList - The subset of WaterList that was created since the
119 /// previous iteration by inserting unconditional branches.
120 SmallSet<MachineBasicBlock *, 4> NewWaterList;
121
122 using water_iterator = std::vector<MachineBasicBlock *>::iterator;
123
124 /// CPUser - One user of a constant pool, keeping the machine instruction
125 /// pointer, the constant pool being referenced, and the max displacement
126 /// allowed from the instruction to the CP. The HighWaterMark records the
127 /// highest basic block where a new CPEntry can be placed. To ensure this
128 /// pass terminates, the CP entries are initially placed at the end of the
129 /// function and then move monotonically to lower addresses. The
130 /// exception to this rule is when the current CP entry for a particular
131 /// CPUser is out of range, but there is another CP entry for the same
132 /// constant value in range. We want to use the existing in-range CP
133 /// entry, but if it later moves out of range, the search for new water
134 /// should resume where it left off. The HighWaterMark is used to record
135 /// that point.
136 struct CPUser {
137 MachineInstr *MI;
138 MachineInstr *CPEMI;
139 MachineBasicBlock *HighWaterMark;
140
141 private:
142 unsigned MaxDisp;
143
144 public:
145 bool NegOk;
146
147 CPUser(MachineInstr *Mi, MachineInstr *Cpemi, unsigned Maxdisp, bool Neg)
148 : MI(Mi), CPEMI(Cpemi), MaxDisp(Maxdisp), NegOk(Neg) {
149 HighWaterMark = CPEMI->getParent();
150 }
151
152 /// getMaxDisp - Returns the maximum displacement supported by MI.
153 unsigned getMaxDisp() const { return MaxDisp - 16; }
154
155 void setMaxDisp(unsigned Val) { MaxDisp = Val; }
156 };
157
158 /// CPUsers - Keep track of all of the machine instructions that use various
159 /// constant pools and their max displacement.
160 std::vector<CPUser> CPUsers;
161
162 /// CPEntry - One per constant pool entry, keeping the machine instruction
163 /// pointer, the constpool index, and the number of CPUser's which
164 /// reference this entry.
165 struct CPEntry {
166 MachineInstr *CPEMI;
167 unsigned CPI;
168 unsigned RefCount;
169
170 CPEntry(MachineInstr *Cpemi, unsigned Cpi, unsigned Rc = 0)
171 : CPEMI(Cpemi), CPI(Cpi), RefCount(Rc) {}
172 };
173
174 /// CPEntries - Keep track of all of the constant pool entry machine
175 /// instructions. For each original constpool index (i.e. those that
176 /// existed upon entry to this pass), it keeps a vector of entries.
177 /// Original elements are cloned as we go along; the clones are
178 /// put in the vector of the original element, but have distinct CPIs.
179 std::vector<std::vector<CPEntry>> CPEntries;
180
181 /// ImmBranch - One per immediate branch, keeping the machine instruction
182 /// pointer, conditional or unconditional, the max displacement,
183 /// and (if isCond is true) the corresponding unconditional branch
184 /// opcode.
185 struct ImmBranch {
186 MachineInstr *MI;
187 unsigned MaxDisp : 31;
188 bool IsCond : 1;
189 int UncondBr;
190
191 ImmBranch(MachineInstr *Mi, unsigned Maxdisp, bool Cond, int Ubr)
192 : MI(Mi), MaxDisp(Maxdisp), IsCond(Cond), UncondBr(Ubr) {}
193 };
194
195 /// ImmBranches - Keep track of all the immediate branch instructions.
196 ///
197 std::vector<ImmBranch> ImmBranches;
198
199 const CSKYSubtarget *STI = nullptr;
200 const CSKYInstrInfo *TII;
201 CSKYMachineFunctionInfo *MFI;
202 MachineFunction *MF = nullptr;
203 MachineConstantPool *MCP = nullptr;
204
205 unsigned PICLabelUId;
206
207 void initPICLabelUId(unsigned UId) { PICLabelUId = UId; }
208
209 unsigned createPICLabelUId() { return PICLabelUId++; }
210
211public:
212 static char ID;
213
214 CSKYConstantIslands() : MachineFunctionPass(ID) {}
215
216 StringRef getPassName() const override { return "CSKY Constant Islands"; }
217
218 bool runOnMachineFunction(MachineFunction &F) override;
219
220 void getAnalysisUsage(AnalysisUsage &AU) const override {
221 AU.addRequired<MachineDominatorTree>();
222 MachineFunctionPass::getAnalysisUsage(AU);
223 }
224
225 MachineFunctionProperties getRequiredProperties() const override {
226 return MachineFunctionProperties().set(
227 MachineFunctionProperties::Property::NoVRegs);
228 }
229
230 void doInitialPlacement(std::vector<MachineInstr *> &CPEMIs);
231 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
232 Align getCPEAlign(const MachineInstr &CPEMI);
233 void initializeFunctionInfo(const std::vector<MachineInstr *> &CPEMIs);
234 unsigned getOffsetOf(MachineInstr *MI) const;
235 unsigned getUserOffset(CPUser &) const;
236 void dumpBBs();
237
238 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset, unsigned Disp,
239 bool NegativeOK);
240 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
241 const CPUser &U);
242
243 void computeBlockSize(MachineBasicBlock *MBB);
244 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr &MI);
245 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
246 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
247 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr *CPEMI);
248 int findInRangeCPEntry(CPUser &U, unsigned UserOffset);
249 bool findAvailableWater(CPUser &U, unsigned UserOffset,
250 water_iterator &WaterIter);
251 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
252 MachineBasicBlock *&NewMBB);
253 bool handleConstantPoolUser(unsigned CPUserIndex);
254 void removeDeadCPEMI(MachineInstr *CPEMI);
255 bool removeUnusedCPEntries();
256 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
257 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
258 bool DoDump = false);
259 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water, CPUser &U,
260 unsigned &Growth);
261 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
262 bool fixupImmediateBr(ImmBranch &Br);
263 bool fixupConditionalBr(ImmBranch &Br);
264 bool fixupUnconditionalBr(ImmBranch &Br);
265};
266} // end anonymous namespace
267
268char CSKYConstantIslands::ID = 0;
269
270bool CSKYConstantIslands::isOffsetInRange(unsigned UserOffset,
271 unsigned TrialOffset,
272 const CPUser &U) {
273 return isOffsetInRange(UserOffset, TrialOffset, Disp: U.getMaxDisp(), NegativeOK: U.NegOk);
274}
275
276#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
277/// print block size and offset information - debugging
278LLVM_DUMP_METHOD void CSKYConstantIslands::dumpBBs() {
279 for (unsigned J = 0, E = BBInfo.size(); J != E; ++J) {
280 const BasicBlockInfo &BBI = BBInfo[J];
281 dbgs() << format(Fmt: "%08x %bb.%u\t", Vals: BBI.Offset, Vals: J)
282 << format(Fmt: " size=%#x\n", Vals: BBInfo[J].Size);
283 }
284}
285#endif
286
287bool CSKYConstantIslands::runOnMachineFunction(MachineFunction &Mf) {
288 MF = &Mf;
289 MCP = Mf.getConstantPool();
290 STI = &Mf.getSubtarget<CSKYSubtarget>();
291
292 LLVM_DEBUG(dbgs() << "***** CSKYConstantIslands: "
293 << MCP->getConstants().size() << " CP entries, aligned to "
294 << MCP->getConstantPoolAlign().value() << " bytes *****\n");
295
296 TII = STI->getInstrInfo();
297 MFI = MF->getInfo<CSKYMachineFunctionInfo>();
298
299 // This pass invalidates liveness information when it splits basic blocks.
300 MF->getRegInfo().invalidateLiveness();
301
302 // Renumber all of the machine basic blocks in the function, guaranteeing that
303 // the numbers agree with the position of the block in the function.
304 MF->RenumberBlocks();
305
306 bool MadeChange = false;
307
308 // Perform the initial placement of the constant pool entries. To start with,
309 // we put them all at the end of the function.
310 std::vector<MachineInstr *> CPEMIs;
311 if (!MCP->isEmpty())
312 doInitialPlacement(CPEMIs);
313
314 /// The next UID to take is the first unused one.
315 initPICLabelUId(UId: CPEMIs.size());
316
317 // Do the initial scan of the function, building up information about the
318 // sizes of each block, the location of all the water, and finding all of the
319 // constant pool users.
320 initializeFunctionInfo(CPEMIs);
321 CPEMIs.clear();
322 LLVM_DEBUG(dumpBBs());
323
324 /// Remove dead constant pool entries.
325 MadeChange |= removeUnusedCPEntries();
326
327 // Iteratively place constant pool entries and fix up branches until there
328 // is no change.
329 unsigned NoCPIters = 0, NoBRIters = 0;
330 (void)NoBRIters;
331 while (true) {
332 LLVM_DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
333 bool CPChange = false;
334 for (unsigned I = 0, E = CPUsers.size(); I != E; ++I)
335 CPChange |= handleConstantPoolUser(CPUserIndex: I);
336 if (CPChange && ++NoCPIters > 30)
337 report_fatal_error(reason: "Constant Island pass failed to converge!");
338 LLVM_DEBUG(dumpBBs());
339
340 // Clear NewWaterList now. If we split a block for branches, it should
341 // appear as "new water" for the next iteration of constant pool placement.
342 NewWaterList.clear();
343
344 LLVM_DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
345 bool BRChange = false;
346 for (unsigned I = 0, E = ImmBranches.size(); I != E; ++I)
347 BRChange |= fixupImmediateBr(Br&: ImmBranches[I]);
348 if (BRChange && ++NoBRIters > 30)
349 report_fatal_error(reason: "Branch Fix Up pass failed to converge!");
350 LLVM_DEBUG(dumpBBs());
351 if (!CPChange && !BRChange)
352 break;
353 MadeChange = true;
354 }
355
356 LLVM_DEBUG(dbgs() << '\n'; dumpBBs());
357
358 BBInfo.clear();
359 WaterList.clear();
360 CPUsers.clear();
361 CPEntries.clear();
362 ImmBranches.clear();
363 return MadeChange;
364}
365
366/// doInitialPlacement - Perform the initial placement of the constant pool
367/// entries. To start with, we put them all at the end of the function.
368void CSKYConstantIslands::doInitialPlacement(
369 std::vector<MachineInstr *> &CPEMIs) {
370 // Create the basic block to hold the CPE's.
371 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
372 MF->push_back(MBB: BB);
373
374 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
375 const Align MaxAlign = MCP->getConstantPoolAlign();
376
377 // Mark the basic block as required by the const-pool.
378 BB->setAlignment(Align(2));
379
380 // The function needs to be as aligned as the basic blocks. The linker may
381 // move functions around based on their alignment.
382 MF->ensureAlignment(A: BB->getAlignment());
383
384 // Order the entries in BB by descending alignment. That ensures correct
385 // alignment of all entries as long as BB is sufficiently aligned. Keep
386 // track of the insertion point for each alignment. We are going to bucket
387 // sort the entries as they are created.
388 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(Log2(A: MaxAlign) + 1,
389 BB->end());
390
391 // Add all of the constants from the constant pool to the end block, use an
392 // identity mapping of CPI's to CPE's.
393 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
394
395 const DataLayout &TD = MF->getDataLayout();
396 for (unsigned I = 0, E = CPs.size(); I != E; ++I) {
397 unsigned Size = CPs[I].getSizeInBytes(DL: TD);
398 assert(Size >= 4 && "Too small constant pool entry");
399 Align Alignment = CPs[I].getAlign();
400 // Verify that all constant pool entries are a multiple of their alignment.
401 // If not, we would have to pad them out so that instructions stay aligned.
402 assert(isAligned(Alignment, Size) && "CP Entry not multiple of 4 bytes!");
403
404 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
405 unsigned LogAlign = Log2(A: Alignment);
406 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
407
408 MachineInstr *CPEMI =
409 BuildMI(*BB, InsAt, DebugLoc(), TII->get(CSKY::CONSTPOOL_ENTRY))
410 .addImm(I)
411 .addConstantPoolIndex(I)
412 .addImm(Size);
413
414 CPEMIs.push_back(x: CPEMI);
415
416 // Ensure that future entries with higher alignment get inserted before
417 // CPEMI. This is bucket sort with iterators.
418 for (unsigned A = LogAlign + 1; A <= Log2(A: MaxAlign); ++A)
419 if (InsPoint[A] == InsAt)
420 InsPoint[A] = CPEMI;
421 // Add a new CPEntry, but no corresponding CPUser yet.
422 CPEntries.emplace_back(args: 1, args: CPEntry(CPEMI, I));
423 ++NumCPEs;
424 LLVM_DEBUG(dbgs() << "Moved CPI#" << I << " to end of function, size = "
425 << Size << ", align = " << Alignment.value() << '\n');
426 }
427 LLVM_DEBUG(BB->dump());
428}
429
430/// BBHasFallthrough - Return true if the specified basic block can fallthrough
431/// into the block immediately after it.
432static bool bbHasFallthrough(MachineBasicBlock *MBB) {
433 // Get the next machine basic block in the function.
434 MachineFunction::iterator MBBI = MBB->getIterator();
435 // Can't fall off end of function.
436 if (std::next(x: MBBI) == MBB->getParent()->end())
437 return false;
438
439 MachineBasicBlock *NextBB = &*std::next(x: MBBI);
440 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
441 E = MBB->succ_end();
442 I != E; ++I)
443 if (*I == NextBB)
444 return true;
445
446 return false;
447}
448
449/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
450/// look up the corresponding CPEntry.
451CSKYConstantIslands::CPEntry *
452CSKYConstantIslands::findConstPoolEntry(unsigned CPI,
453 const MachineInstr *CPEMI) {
454 std::vector<CPEntry> &CPEs = CPEntries[CPI];
455 // Number of entries per constpool index should be small, just do a
456 // linear search.
457 for (unsigned I = 0, E = CPEs.size(); I != E; ++I) {
458 if (CPEs[I].CPEMI == CPEMI)
459 return &CPEs[I];
460 }
461 return nullptr;
462}
463
464/// getCPEAlign - Returns the required alignment of the constant pool entry
465/// represented by CPEMI. Alignment is measured in log2(bytes) units.
466Align CSKYConstantIslands::getCPEAlign(const MachineInstr &CPEMI) {
467 assert(CPEMI.getOpcode() == CSKY::CONSTPOOL_ENTRY);
468
469 unsigned CPI = CPEMI.getOperand(i: 1).getIndex();
470 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
471 return MCP->getConstants()[CPI].getAlign();
472}
473
474/// initializeFunctionInfo - Do the initial scan of the function, building up
475/// information about the sizes of each block, the location of all the water,
476/// and finding all of the constant pool users.
477void CSKYConstantIslands::initializeFunctionInfo(
478 const std::vector<MachineInstr *> &CPEMIs) {
479 BBInfo.clear();
480 BBInfo.resize(new_size: MF->getNumBlockIDs());
481
482 // First thing, compute the size of all basic blocks, and see if the function
483 // has any inline assembly in it. If so, we have to be conservative about
484 // alignment assumptions, as we don't know for sure the size of any
485 // instructions in the inline assembly.
486 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
487 computeBlockSize(MBB: &*I);
488
489 // Compute block offsets.
490 adjustBBOffsetsAfter(BB: &MF->front());
491
492 // Now go back through the instructions and build up our data structures.
493 for (MachineBasicBlock &MBB : *MF) {
494 // If this block doesn't fall through into the next MBB, then this is
495 // 'water' that a constant pool island could be placed.
496 if (!bbHasFallthrough(MBB: &MBB))
497 WaterList.push_back(x: &MBB);
498 for (MachineInstr &MI : MBB) {
499 if (MI.isDebugInstr())
500 continue;
501
502 int Opc = MI.getOpcode();
503 if (MI.isBranch() && !MI.isIndirectBranch()) {
504 bool IsCond = MI.isConditionalBranch();
505 unsigned Bits = 0;
506 unsigned Scale = 1;
507 int UOpc = CSKY::BR32;
508
509 switch (MI.getOpcode()) {
510 case CSKY::BR16:
511 case CSKY::BF16:
512 case CSKY::BT16:
513 Bits = 10;
514 Scale = 2;
515 break;
516 default:
517 Bits = 16;
518 Scale = 2;
519 break;
520 }
521
522 // Record this immediate branch.
523 unsigned MaxOffs = ((1 << (Bits - 1)) - 1) * Scale;
524 ImmBranches.push_back(x: ImmBranch(&MI, MaxOffs, IsCond, UOpc));
525 }
526
527 if (Opc == CSKY::CONSTPOOL_ENTRY)
528 continue;
529
530 // Scan the instructions for constant pool operands.
531 for (unsigned Op = 0, E = MI.getNumOperands(); Op != E; ++Op)
532 if (MI.getOperand(i: Op).isCPI()) {
533 // We found one. The addressing mode tells us the max displacement
534 // from the PC that this instruction permits.
535
536 // Basic size info comes from the TSFlags field.
537 unsigned Bits = 0;
538 unsigned Scale = 1;
539 bool NegOk = false;
540
541 switch (Opc) {
542 default:
543 llvm_unreachable("Unknown addressing mode for CP reference!");
544 case CSKY::MOVIH32:
545 case CSKY::ORI32:
546 continue;
547 case CSKY::PseudoTLSLA32:
548 case CSKY::JSRI32:
549 case CSKY::JMPI32:
550 case CSKY::LRW32:
551 case CSKY::LRW32_Gen:
552 Bits = 16;
553 Scale = 4;
554 break;
555 case CSKY::f2FLRW_S:
556 case CSKY::f2FLRW_D:
557 Bits = 8;
558 Scale = 4;
559 break;
560 case CSKY::GRS32:
561 Bits = 17;
562 Scale = 2;
563 NegOk = true;
564 break;
565 }
566 // Remember that this is a user of a CP entry.
567 unsigned CPI = MI.getOperand(i: Op).getIndex();
568 MachineInstr *CPEMI = CPEMIs[CPI];
569 unsigned MaxOffs = ((1 << Bits) - 1) * Scale;
570 CPUsers.push_back(x: CPUser(&MI, CPEMI, MaxOffs, NegOk));
571
572 // Increment corresponding CPEntry reference count.
573 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
574 assert(CPE && "Cannot find a corresponding CPEntry!");
575 CPE->RefCount++;
576 }
577 }
578 }
579}
580
581/// computeBlockSize - Compute the size and some alignment information for MBB.
582/// This function updates BBInfo directly.
583void CSKYConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
584 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
585 BBI.Size = 0;
586
587 for (const MachineInstr &MI : *MBB)
588 BBI.Size += TII->getInstSizeInBytes(MI);
589}
590
591/// getOffsetOf - Return the current offset of the specified machine instruction
592/// from the start of the function. This offset changes as stuff is moved
593/// around inside the function.
594unsigned CSKYConstantIslands::getOffsetOf(MachineInstr *MI) const {
595 MachineBasicBlock *MBB = MI->getParent();
596
597 // The offset is composed of two things: the sum of the sizes of all MBB's
598 // before this instruction's block, and the offset from the start of the block
599 // it is in.
600 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
601
602 // Sum instructions before MI in MBB.
603 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
604 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
605 Offset += TII->getInstSizeInBytes(MI: *I);
606 }
607 return Offset;
608}
609
610/// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
611/// ID.
612static bool compareMbbNumbers(const MachineBasicBlock *LHS,
613 const MachineBasicBlock *RHS) {
614 return LHS->getNumber() < RHS->getNumber();
615}
616
617/// updateForInsertedWaterBlock - When a block is newly inserted into the
618/// machine function, it upsets all of the block numbers. Renumber the blocks
619/// and update the arrays that parallel this numbering.
620void CSKYConstantIslands::updateForInsertedWaterBlock(
621 MachineBasicBlock *NewBB) {
622 // Renumber the MBB's to keep them consecutive.
623 NewBB->getParent()->RenumberBlocks(MBBFrom: NewBB);
624
625 // Insert an entry into BBInfo to align it properly with the (newly
626 // renumbered) block numbers.
627 BBInfo.insert(position: BBInfo.begin() + NewBB->getNumber(), x: BasicBlockInfo());
628
629 // Next, update WaterList. Specifically, we need to add NewMBB as having
630 // available water after it.
631 water_iterator IP = llvm::lower_bound(Range&: WaterList, Value&: NewBB, C: compareMbbNumbers);
632 WaterList.insert(position: IP, x: NewBB);
633}
634
635unsigned CSKYConstantIslands::getUserOffset(CPUser &U) const {
636 unsigned UserOffset = getOffsetOf(MI: U.MI);
637
638 UserOffset &= ~3u;
639
640 return UserOffset;
641}
642
643/// Split the basic block containing MI into two blocks, which are joined by
644/// an unconditional branch. Update data structures and renumber blocks to
645/// account for this change and returns the newly created block.
646MachineBasicBlock *
647CSKYConstantIslands::splitBlockBeforeInstr(MachineInstr &MI) {
648 MachineBasicBlock *OrigBB = MI.getParent();
649
650 // Create a new MBB for the code after the OrigBB.
651 MachineBasicBlock *NewBB =
652 MF->CreateMachineBasicBlock(BB: OrigBB->getBasicBlock());
653 MachineFunction::iterator MBBI = ++OrigBB->getIterator();
654 MF->insert(MBBI, MBB: NewBB);
655
656 // Splice the instructions starting with MI over to NewBB.
657 NewBB->splice(Where: NewBB->end(), Other: OrigBB, From: MI, To: OrigBB->end());
658
659 // Add an unconditional branch from OrigBB to NewBB.
660 // Note the new unconditional branch is not being recorded.
661 // There doesn't seem to be meaningful DebugInfo available; this doesn't
662 // correspond to anything in the source.
663
664 // TODO: Add support for 16bit instr.
665 BuildMI(OrigBB, DebugLoc(), TII->get(CSKY::BR32)).addMBB(NewBB);
666 ++NumSplit;
667
668 // Update the CFG. All succs of OrigBB are now succs of NewBB.
669 NewBB->transferSuccessors(FromMBB: OrigBB);
670
671 // OrigBB branches to NewBB.
672 OrigBB->addSuccessor(Succ: NewBB);
673
674 // Update internal data structures to account for the newly inserted MBB.
675 // This is almost the same as updateForInsertedWaterBlock, except that
676 // the Water goes after OrigBB, not NewBB.
677 MF->RenumberBlocks(MBBFrom: NewBB);
678
679 // Insert an entry into BBInfo to align it properly with the (newly
680 // renumbered) block numbers.
681 BBInfo.insert(position: BBInfo.begin() + NewBB->getNumber(), x: BasicBlockInfo());
682
683 // Next, update WaterList. Specifically, we need to add OrigMBB as having
684 // available water after it (but not if it's already there, which happens
685 // when splitting before a conditional branch that is followed by an
686 // unconditional branch - in that case we want to insert NewBB).
687 water_iterator IP = llvm::lower_bound(Range&: WaterList, Value&: OrigBB, C: compareMbbNumbers);
688 MachineBasicBlock *WaterBB = *IP;
689 if (WaterBB == OrigBB)
690 WaterList.insert(position: std::next(x: IP), x: NewBB);
691 else
692 WaterList.insert(position: IP, x: OrigBB);
693 NewWaterList.insert(Ptr: OrigBB);
694
695 // Figure out how large the OrigBB is. As the first half of the original
696 // block, it cannot contain a tablejump. The size includes
697 // the new jump we added. (It should be possible to do this without
698 // recounting everything, but it's very confusing, and this is rarely
699 // executed.)
700 computeBlockSize(MBB: OrigBB);
701
702 // Figure out how large the NewMBB is. As the second half of the original
703 // block, it may contain a tablejump.
704 computeBlockSize(MBB: NewBB);
705
706 // All BBOffsets following these blocks must be modified.
707 adjustBBOffsetsAfter(BB: OrigBB);
708
709 return NewBB;
710}
711
712/// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
713/// reference) is within MaxDisp of TrialOffset (a proposed location of a
714/// constant pool entry).
715bool CSKYConstantIslands::isOffsetInRange(unsigned UserOffset,
716 unsigned TrialOffset,
717 unsigned MaxDisp, bool NegativeOK) {
718 if (UserOffset <= TrialOffset) {
719 // User before the Trial.
720 if (TrialOffset - UserOffset <= MaxDisp)
721 return true;
722 } else if (NegativeOK) {
723 if (UserOffset - TrialOffset <= MaxDisp)
724 return true;
725 }
726 return false;
727}
728
729/// isWaterInRange - Returns true if a CPE placed after the specified
730/// Water (a basic block) will be in range for the specific MI.
731///
732/// Compute how much the function will grow by inserting a CPE after Water.
733bool CSKYConstantIslands::isWaterInRange(unsigned UserOffset,
734 MachineBasicBlock *Water, CPUser &U,
735 unsigned &Growth) {
736 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset();
737 unsigned NextBlockOffset;
738 Align NextBlockAlignment;
739 MachineFunction::const_iterator NextBlock = ++Water->getIterator();
740 if (NextBlock == MF->end()) {
741 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
742 NextBlockAlignment = Align(4);
743 } else {
744 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
745 NextBlockAlignment = NextBlock->getAlignment();
746 }
747 unsigned Size = U.CPEMI->getOperand(i: 2).getImm();
748 unsigned CPEEnd = CPEOffset + Size;
749
750 // The CPE may be able to hide in the alignment padding before the next
751 // block. It may also cause more padding to be required if it is more aligned
752 // that the next block.
753 if (CPEEnd > NextBlockOffset) {
754 Growth = CPEEnd - NextBlockOffset;
755 // Compute the padding that would go at the end of the CPE to align the next
756 // block.
757 Growth += offsetToAlignment(Value: CPEEnd, Alignment: NextBlockAlignment);
758
759 // If the CPE is to be inserted before the instruction, that will raise
760 // the offset of the instruction. Also account for unknown alignment padding
761 // in blocks between CPE and the user.
762 if (CPEOffset < UserOffset)
763 UserOffset += Growth;
764 } else
765 // CPE fits in existing padding.
766 Growth = 0;
767
768 return isOffsetInRange(UserOffset, TrialOffset: CPEOffset, U);
769}
770
771/// isCPEntryInRange - Returns true if the distance between specific MI and
772/// specific ConstPool entry instruction can fit in MI's displacement field.
773bool CSKYConstantIslands::isCPEntryInRange(MachineInstr *MI,
774 unsigned UserOffset,
775 MachineInstr *CPEMI,
776 unsigned MaxDisp, bool NegOk,
777 bool DoDump) {
778 unsigned CPEOffset = getOffsetOf(MI: CPEMI);
779
780 if (DoDump) {
781 LLVM_DEBUG({
782 unsigned Block = MI->getParent()->getNumber();
783 const BasicBlockInfo &BBI = BBInfo[Block];
784 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
785 << " max delta=" << MaxDisp
786 << format(" insn address=%#x", UserOffset) << " in "
787 << printMBBReference(*MI->getParent()) << ": "
788 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
789 << format("CPE address=%#x offset=%+d: ", CPEOffset,
790 int(CPEOffset - UserOffset));
791 });
792 }
793
794 return isOffsetInRange(UserOffset, TrialOffset: CPEOffset, MaxDisp, NegativeOK: NegOk);
795}
796
797#ifndef NDEBUG
798/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
799/// unconditionally branches to its only successor.
800static bool bbIsJumpedOver(MachineBasicBlock *MBB) {
801 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
802 return false;
803 MachineBasicBlock *Succ = *MBB->succ_begin();
804 MachineBasicBlock *Pred = *MBB->pred_begin();
805 MachineInstr *PredMI = &Pred->back();
806 if (PredMI->getOpcode() == CSKY::BR32 /*TODO: change to 16bit instr. */)
807 return PredMI->getOperand(i: 0).getMBB() == Succ;
808 return false;
809}
810#endif
811
812void CSKYConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
813 unsigned BBNum = BB->getNumber();
814 for (unsigned I = BBNum + 1, E = MF->getNumBlockIDs(); I < E; ++I) {
815 // Get the offset and known bits at the end of the layout predecessor.
816 // Include the alignment of the current block.
817 unsigned Offset = BBInfo[I - 1].Offset + BBInfo[I - 1].Size;
818 BBInfo[I].Offset = Offset;
819 }
820}
821
822/// decrementCPEReferenceCount - find the constant pool entry with index CPI
823/// and instruction CPEMI, and decrement its refcount. If the refcount
824/// becomes 0 remove the entry and instruction. Returns true if we removed
825/// the entry, false if we didn't.
826bool CSKYConstantIslands::decrementCPEReferenceCount(unsigned CPI,
827 MachineInstr *CPEMI) {
828 // Find the old entry. Eliminate it if it is no longer used.
829 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
830 assert(CPE && "Unexpected!");
831 if (--CPE->RefCount == 0) {
832 removeDeadCPEMI(CPEMI);
833 CPE->CPEMI = nullptr;
834 --NumCPEs;
835 return true;
836 }
837 return false;
838}
839
840/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
841/// if not, see if an in-range clone of the CPE is in range, and if so,
842/// change the data structures so the user references the clone. Returns:
843/// 0 = no existing entry found
844/// 1 = entry found, and there were no code insertions or deletions
845/// 2 = entry found, and there were code insertions or deletions
846int CSKYConstantIslands::findInRangeCPEntry(CPUser &U, unsigned UserOffset) {
847 MachineInstr *UserMI = U.MI;
848 MachineInstr *CPEMI = U.CPEMI;
849
850 // Check to see if the CPE is already in-range.
851 if (isCPEntryInRange(MI: UserMI, UserOffset, CPEMI, MaxDisp: U.getMaxDisp(), NegOk: U.NegOk,
852 DoDump: true)) {
853 LLVM_DEBUG(dbgs() << "In range\n");
854 return 1;
855 }
856
857 // No. Look for previously created clones of the CPE that are in range.
858 unsigned CPI = CPEMI->getOperand(i: 1).getIndex();
859 std::vector<CPEntry> &CPEs = CPEntries[CPI];
860 for (unsigned I = 0, E = CPEs.size(); I != E; ++I) {
861 // We already tried this one
862 if (CPEs[I].CPEMI == CPEMI)
863 continue;
864 // Removing CPEs can leave empty entries, skip
865 if (CPEs[I].CPEMI == nullptr)
866 continue;
867 if (isCPEntryInRange(MI: UserMI, UserOffset, CPEMI: CPEs[I].CPEMI, MaxDisp: U.getMaxDisp(),
868 NegOk: U.NegOk)) {
869 LLVM_DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
870 << CPEs[I].CPI << "\n");
871 // Point the CPUser node to the replacement
872 U.CPEMI = CPEs[I].CPEMI;
873 // Change the CPI in the instruction operand to refer to the clone.
874 for (unsigned J = 0, E = UserMI->getNumOperands(); J != E; ++J)
875 if (UserMI->getOperand(i: J).isCPI()) {
876 UserMI->getOperand(i: J).setIndex(CPEs[I].CPI);
877 break;
878 }
879 // Adjust the refcount of the clone...
880 CPEs[I].RefCount++;
881 // ...and the original. If we didn't remove the old entry, none of the
882 // addresses changed, so we don't need another pass.
883 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
884 }
885 }
886 return 0;
887}
888
889/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
890/// the specific unconditional branch instruction.
891static inline unsigned getUnconditionalBrDisp(int Opc) {
892 unsigned Bits, Scale;
893
894 switch (Opc) {
895 case CSKY::BR16:
896 Bits = 10;
897 Scale = 2;
898 break;
899 case CSKY::BR32:
900 Bits = 16;
901 Scale = 2;
902 break;
903 default:
904 llvm_unreachable("");
905 }
906
907 unsigned MaxOffs = ((1 << (Bits - 1)) - 1) * Scale;
908 return MaxOffs;
909}
910
911/// findAvailableWater - Look for an existing entry in the WaterList in which
912/// we can place the CPE referenced from U so it's within range of U's MI.
913/// Returns true if found, false if not. If it returns true, WaterIter
914/// is set to the WaterList entry.
915/// To ensure that this pass
916/// terminates, the CPE location for a particular CPUser is only allowed to
917/// move to a lower address, so search backward from the end of the list and
918/// prefer the first water that is in range.
919bool CSKYConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
920 water_iterator &WaterIter) {
921 if (WaterList.empty())
922 return false;
923
924 unsigned BestGrowth = ~0u;
925 for (water_iterator IP = std::prev(x: WaterList.end()), B = WaterList.begin();;
926 --IP) {
927 MachineBasicBlock *WaterBB = *IP;
928 // Check if water is in range and is either at a lower address than the
929 // current "high water mark" or a new water block that was created since
930 // the previous iteration by inserting an unconditional branch. In the
931 // latter case, we want to allow resetting the high water mark back to
932 // this new water since we haven't seen it before. Inserting branches
933 // should be relatively uncommon and when it does happen, we want to be
934 // sure to take advantage of it for all the CPEs near that block, so that
935 // we don't insert more branches than necessary.
936 unsigned Growth;
937 if (isWaterInRange(UserOffset, Water: WaterBB, U, Growth) &&
938 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
939 NewWaterList.count(Ptr: WaterBB)) &&
940 Growth < BestGrowth) {
941 // This is the least amount of required padding seen so far.
942 BestGrowth = Growth;
943 WaterIter = IP;
944 LLVM_DEBUG(dbgs() << "Found water after " << printMBBReference(*WaterBB)
945 << " Growth=" << Growth << '\n');
946
947 // Keep looking unless it is perfect.
948 if (BestGrowth == 0)
949 return true;
950 }
951 if (IP == B)
952 break;
953 }
954 return BestGrowth != ~0u;
955}
956
957/// createNewWater - No existing WaterList entry will work for
958/// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
959/// block is used if in range, and the conditional branch munged so control
960/// flow is correct. Otherwise the block is split to create a hole with an
961/// unconditional branch around it. In either case NewMBB is set to a
962/// block following which the new island can be inserted (the WaterList
963/// is not adjusted).
964void CSKYConstantIslands::createNewWater(unsigned CPUserIndex,
965 unsigned UserOffset,
966 MachineBasicBlock *&NewMBB) {
967 CPUser &U = CPUsers[CPUserIndex];
968 MachineInstr *UserMI = U.MI;
969 MachineInstr *CPEMI = U.CPEMI;
970 MachineBasicBlock *UserMBB = UserMI->getParent();
971 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
972
973 // If the block does not end in an unconditional branch already, and if the
974 // end of the block is within range, make new water there.
975 if (bbHasFallthrough(MBB: UserMBB)) {
976 // Size of branch to insert.
977 unsigned Delta = 4;
978 // Compute the offset where the CPE will begin.
979 unsigned CPEOffset = UserBBI.postOffset() + Delta;
980
981 if (isOffsetInRange(UserOffset, TrialOffset: CPEOffset, U)) {
982 LLVM_DEBUG(dbgs() << "Split at end of " << printMBBReference(*UserMBB)
983 << format(", expected CPE offset %#x\n", CPEOffset));
984 NewMBB = &*++UserMBB->getIterator();
985 // Add an unconditional branch from UserMBB to fallthrough block. Record
986 // it for branch lengthening; this new branch will not get out of range,
987 // but if the preceding conditional branch is out of range, the targets
988 // will be exchanged, and the altered branch may be out of range, so the
989 // machinery has to know about it.
990
991 // TODO: Add support for 16bit instr.
992 int UncondBr = CSKY::BR32;
993 auto *NewMI = BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr))
994 .addMBB(NewMBB)
995 .getInstr();
996 unsigned MaxDisp = getUnconditionalBrDisp(Opc: UncondBr);
997 ImmBranches.push_back(
998 x: ImmBranch(&UserMBB->back(), MaxDisp, false, UncondBr));
999 BBInfo[UserMBB->getNumber()].Size += TII->getInstSizeInBytes(MI: *NewMI);
1000 adjustBBOffsetsAfter(BB: UserMBB);
1001 return;
1002 }
1003 }
1004
1005 // What a big block. Find a place within the block to split it.
1006
1007 // Try to split the block so it's fully aligned. Compute the latest split
1008 // point where we can add a 4-byte branch instruction, and then align to
1009 // Align which is the largest possible alignment in the function.
1010 const Align Align = MF->getAlignment();
1011 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1012 LLVM_DEBUG(dbgs() << format("Split in middle of big block before %#x",
1013 BaseInsertOffset));
1014
1015 // The 4 in the following is for the unconditional branch we'll be inserting
1016 // Alignment of the island is handled
1017 // inside isOffsetInRange.
1018 BaseInsertOffset -= 4;
1019
1020 LLVM_DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1021 << " la=" << Log2(Align) << '\n');
1022
1023 // This could point off the end of the block if we've already got constant
1024 // pool entries following this block; only the last one is in the water list.
1025 // Back past any possible branches (allow for a conditional and a maximally
1026 // long unconditional).
1027 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1028 BaseInsertOffset = UserBBI.postOffset() - 8;
1029 LLVM_DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1030 }
1031 unsigned EndInsertOffset =
1032 BaseInsertOffset + 4 + CPEMI->getOperand(i: 2).getImm();
1033 MachineBasicBlock::iterator MI = UserMI;
1034 ++MI;
1035 unsigned CPUIndex = CPUserIndex + 1;
1036 unsigned NumCPUsers = CPUsers.size();
1037 for (unsigned Offset = UserOffset + TII->getInstSizeInBytes(MI: *UserMI);
1038 Offset < BaseInsertOffset;
1039 Offset += TII->getInstSizeInBytes(MI: *MI), MI = std::next(x: MI)) {
1040 assert(MI != UserMBB->end() && "Fell off end of block");
1041 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1042 CPUser &U = CPUsers[CPUIndex];
1043 if (!isOffsetInRange(UserOffset: Offset, TrialOffset: EndInsertOffset, U)) {
1044 // Shift intertion point by one unit of alignment so it is within reach.
1045 BaseInsertOffset -= Align.value();
1046 EndInsertOffset -= Align.value();
1047 }
1048 // This is overly conservative, as we don't account for CPEMIs being
1049 // reused within the block, but it doesn't matter much. Also assume CPEs
1050 // are added in order with alignment padding. We may eventually be able
1051 // to pack the aligned CPEs better.
1052 EndInsertOffset += U.CPEMI->getOperand(i: 2).getImm();
1053 CPUIndex++;
1054 }
1055 }
1056
1057 NewMBB = splitBlockBeforeInstr(MI&: *--MI);
1058}
1059
1060/// handleConstantPoolUser - Analyze the specified user, checking to see if it
1061/// is out-of-range. If so, pick up the constant pool value and move it some
1062/// place in-range. Return true if we changed any addresses (thus must run
1063/// another pass of branch lengthening), false otherwise.
1064bool CSKYConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1065 CPUser &U = CPUsers[CPUserIndex];
1066 MachineInstr *UserMI = U.MI;
1067 MachineInstr *CPEMI = U.CPEMI;
1068 unsigned CPI = CPEMI->getOperand(i: 1).getIndex();
1069 unsigned Size = CPEMI->getOperand(i: 2).getImm();
1070 // Compute this only once, it's expensive.
1071 unsigned UserOffset = getUserOffset(U);
1072
1073 // See if the current entry is within range, or there is a clone of it
1074 // in range.
1075 int result = findInRangeCPEntry(U, UserOffset);
1076 if (result == 1)
1077 return false;
1078 if (result == 2)
1079 return true;
1080
1081 // Look for water where we can place this CPE.
1082 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1083 MachineBasicBlock *NewMBB;
1084 water_iterator IP;
1085 if (findAvailableWater(U, UserOffset, WaterIter&: IP)) {
1086 LLVM_DEBUG(dbgs() << "Found water in range\n");
1087 MachineBasicBlock *WaterBB = *IP;
1088
1089 // If the original WaterList entry was "new water" on this iteration,
1090 // propagate that to the new island. This is just keeping NewWaterList
1091 // updated to match the WaterList, which will be updated below.
1092 if (NewWaterList.erase(Ptr: WaterBB))
1093 NewWaterList.insert(Ptr: NewIsland);
1094
1095 // The new CPE goes before the following block (NewMBB).
1096 NewMBB = &*++WaterBB->getIterator();
1097 } else {
1098 LLVM_DEBUG(dbgs() << "No water found\n");
1099 createNewWater(CPUserIndex, UserOffset, NewMBB);
1100
1101 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1102 // called while handling branches so that the water will be seen on the
1103 // next iteration for constant pools, but in this context, we don't want
1104 // it. Check for this so it will be removed from the WaterList.
1105 // Also remove any entry from NewWaterList.
1106 MachineBasicBlock *WaterBB = &*--NewMBB->getIterator();
1107 IP = llvm::find(Range&: WaterList, Val: WaterBB);
1108 if (IP != WaterList.end())
1109 NewWaterList.erase(Ptr: WaterBB);
1110
1111 // We are adding new water. Update NewWaterList.
1112 NewWaterList.insert(Ptr: NewIsland);
1113 }
1114
1115 // Remove the original WaterList entry; we want subsequent insertions in
1116 // this vicinity to go after the one we're about to insert. This
1117 // considerably reduces the number of times we have to move the same CPE
1118 // more than once and is also important to ensure the algorithm terminates.
1119 if (IP != WaterList.end())
1120 WaterList.erase(position: IP);
1121
1122 // Okay, we know we can put an island before NewMBB now, do it!
1123 MF->insert(MBBI: NewMBB->getIterator(), MBB: NewIsland);
1124
1125 // Update internal data structures to account for the newly inserted MBB.
1126 updateForInsertedWaterBlock(NewBB: NewIsland);
1127
1128 // Decrement the old entry, and remove it if refcount becomes 0.
1129 decrementCPEReferenceCount(CPI, CPEMI);
1130
1131 // No existing clone of this CPE is within range.
1132 // We will be generating a new clone. Get a UID for it.
1133 unsigned ID = createPICLabelUId();
1134
1135 // Now that we have an island to add the CPE to, clone the original CPE and
1136 // add it to the island.
1137 U.HighWaterMark = NewIsland;
1138 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(CSKY::CONSTPOOL_ENTRY))
1139 .addImm(ID)
1140 .addConstantPoolIndex(CPI)
1141 .addImm(Size);
1142 CPEntries[CPI].push_back(x: CPEntry(U.CPEMI, ID, 1));
1143 ++NumCPEs;
1144
1145 // Mark the basic block as aligned as required by the const-pool entry.
1146 NewIsland->setAlignment(getCPEAlign(CPEMI: *U.CPEMI));
1147
1148 // Increase the size of the island block to account for the new entry.
1149 BBInfo[NewIsland->getNumber()].Size += Size;
1150 adjustBBOffsetsAfter(BB: &*--NewIsland->getIterator());
1151
1152 // Finally, change the CPI in the instruction operand to be ID.
1153 for (unsigned I = 0, E = UserMI->getNumOperands(); I != E; ++I)
1154 if (UserMI->getOperand(i: I).isCPI()) {
1155 UserMI->getOperand(i: I).setIndex(ID);
1156 break;
1157 }
1158
1159 LLVM_DEBUG(
1160 dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1161 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1162
1163 return true;
1164}
1165
1166/// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1167/// sizes and offsets of impacted basic blocks.
1168void CSKYConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1169 MachineBasicBlock *CPEBB = CPEMI->getParent();
1170 unsigned Size = CPEMI->getOperand(i: 2).getImm();
1171 CPEMI->eraseFromParent();
1172 BBInfo[CPEBB->getNumber()].Size -= Size;
1173 // All succeeding offsets have the current size value added in, fix this.
1174 if (CPEBB->empty()) {
1175 BBInfo[CPEBB->getNumber()].Size = 0;
1176
1177 // This block no longer needs to be aligned.
1178 CPEBB->setAlignment(Align(4));
1179 } else {
1180 // Entries are sorted by descending alignment, so realign from the front.
1181 CPEBB->setAlignment(getCPEAlign(CPEMI: *CPEBB->begin()));
1182 }
1183
1184 adjustBBOffsetsAfter(BB: CPEBB);
1185 // An island has only one predecessor BB and one successor BB. Check if
1186 // this BB's predecessor jumps directly to this BB's successor. This
1187 // shouldn't happen currently.
1188 assert(!bbIsJumpedOver(CPEBB) && "How did this happen?");
1189 // FIXME: remove the empty blocks after all the work is done?
1190}
1191
1192/// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1193/// are zero.
1194bool CSKYConstantIslands::removeUnusedCPEntries() {
1195 unsigned MadeChange = false;
1196 for (unsigned I = 0, E = CPEntries.size(); I != E; ++I) {
1197 std::vector<CPEntry> &CPEs = CPEntries[I];
1198 for (unsigned J = 0, Ee = CPEs.size(); J != Ee; ++J) {
1199 if (CPEs[J].RefCount == 0 && CPEs[J].CPEMI) {
1200 removeDeadCPEMI(CPEMI: CPEs[J].CPEMI);
1201 CPEs[J].CPEMI = nullptr;
1202 MadeChange = true;
1203 }
1204 }
1205 }
1206 return MadeChange;
1207}
1208
1209/// isBBInRange - Returns true if the distance between specific MI and
1210/// specific BB can fit in MI's displacement field.
1211bool CSKYConstantIslands::isBBInRange(MachineInstr *MI,
1212 MachineBasicBlock *DestBB,
1213 unsigned MaxDisp) {
1214 unsigned BrOffset = getOffsetOf(MI);
1215 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1216
1217 LLVM_DEBUG(dbgs() << "Branch of destination " << printMBBReference(*DestBB)
1218 << " from " << printMBBReference(*MI->getParent())
1219 << " max delta=" << MaxDisp << " from " << getOffsetOf(MI)
1220 << " to " << DestOffset << " offset "
1221 << int(DestOffset - BrOffset) << "\t" << *MI);
1222
1223 if (BrOffset <= DestOffset) {
1224 // Branch before the Dest.
1225 if (DestOffset - BrOffset <= MaxDisp)
1226 return true;
1227 } else {
1228 if (BrOffset - DestOffset <= MaxDisp)
1229 return true;
1230 }
1231 return false;
1232}
1233
1234/// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1235/// away to fit in its displacement field.
1236bool CSKYConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1237 MachineInstr *MI = Br.MI;
1238 MachineBasicBlock *DestBB = TII->getBranchDestBlock(MI: *MI);
1239
1240 // Check to see if the DestBB is already in-range.
1241 if (isBBInRange(MI, DestBB, MaxDisp: Br.MaxDisp))
1242 return false;
1243
1244 if (!Br.IsCond)
1245 return fixupUnconditionalBr(Br);
1246 return fixupConditionalBr(Br);
1247}
1248
1249/// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1250/// too far away to fit in its displacement field. If the LR register has been
1251/// spilled in the epilogue, then we can use BSR to implement a far jump.
1252/// Otherwise, add an intermediate branch instruction to a branch.
1253bool CSKYConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1254 MachineInstr *MI = Br.MI;
1255 MachineBasicBlock *MBB = MI->getParent();
1256
1257 if (!MFI->isLRSpilled())
1258 report_fatal_error(reason: "underestimated function size");
1259
1260 // Use BSR to implement far jump.
1261 Br.MaxDisp = ((1 << (26 - 1)) - 1) * 2;
1262 MI->setDesc(TII->get(CSKY::BSR32_BR));
1263 BBInfo[MBB->getNumber()].Size += 4;
1264 adjustBBOffsetsAfter(BB: MBB);
1265 ++NumUBrFixed;
1266
1267 LLVM_DEBUG(dbgs() << " Changed B to long jump " << *MI);
1268
1269 return true;
1270}
1271
1272/// fixupConditionalBr - Fix up a conditional branch whose destination is too
1273/// far away to fit in its displacement field. It is converted to an inverse
1274/// conditional branch + an unconditional branch to the destination.
1275bool CSKYConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1276 MachineInstr *MI = Br.MI;
1277 MachineBasicBlock *DestBB = TII->getBranchDestBlock(MI: *MI);
1278
1279 SmallVector<MachineOperand, 4> Cond;
1280 Cond.push_back(Elt: MachineOperand::CreateImm(Val: MI->getOpcode()));
1281 Cond.push_back(Elt: MI->getOperand(i: 0));
1282 TII->reverseBranchCondition(Cond);
1283
1284 // Add an unconditional branch to the destination and invert the branch
1285 // condition to jump over it:
1286 // bteqz L1
1287 // =>
1288 // bnez L2
1289 // b L1
1290 // L2:
1291
1292 // If the branch is at the end of its MBB and that has a fall-through block,
1293 // direct the updated conditional branch to the fall-through block. Otherwise,
1294 // split the MBB before the next instruction.
1295 MachineBasicBlock *MBB = MI->getParent();
1296 MachineInstr *BMI = &MBB->back();
1297 bool NeedSplit = (BMI != MI) || !bbHasFallthrough(MBB);
1298
1299 ++NumCBrFixed;
1300 if (BMI != MI) {
1301 if (std::next(x: MachineBasicBlock::iterator(MI)) == std::prev(x: MBB->end()) &&
1302 BMI->isUnconditionalBranch()) {
1303 // Last MI in the BB is an unconditional branch. Can we simply invert the
1304 // condition and swap destinations:
1305 // beqz L1
1306 // b L2
1307 // =>
1308 // bnez L2
1309 // b L1
1310 MachineBasicBlock *NewDest = TII->getBranchDestBlock(MI: *BMI);
1311 if (isBBInRange(MI, DestBB: NewDest, MaxDisp: Br.MaxDisp)) {
1312 LLVM_DEBUG(
1313 dbgs() << " Invert Bcc condition and swap its destination with "
1314 << *BMI);
1315 BMI->getOperand(i: BMI->getNumExplicitOperands() - 1).setMBB(DestBB);
1316 MI->getOperand(i: MI->getNumExplicitOperands() - 1).setMBB(NewDest);
1317
1318 MI->setDesc(TII->get(Cond[0].getImm()));
1319 return true;
1320 }
1321 }
1322 }
1323
1324 if (NeedSplit) {
1325 splitBlockBeforeInstr(MI&: *MI);
1326 // No need for the branch to the next block. We're adding an unconditional
1327 // branch to the destination.
1328 int Delta = TII->getInstSizeInBytes(MI: MBB->back());
1329 BBInfo[MBB->getNumber()].Size -= Delta;
1330 MBB->back().eraseFromParent();
1331 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1332
1333 // The conditional successor will be swapped between the BBs after this, so
1334 // update CFG.
1335 MBB->addSuccessor(Succ: DestBB);
1336 std::next(x: MBB->getIterator())->removeSuccessor(Succ: DestBB);
1337 }
1338 MachineBasicBlock *NextBB = &*++MBB->getIterator();
1339
1340 LLVM_DEBUG(dbgs() << " Insert B to " << printMBBReference(*DestBB)
1341 << " also invert condition and change dest. to "
1342 << printMBBReference(*NextBB) << "\n");
1343
1344 // Insert a new conditional branch and a new unconditional branch.
1345 // Also update the ImmBranch as well as adding a new entry for the new branch.
1346
1347 BuildMI(MBB, DebugLoc(), TII->get(Cond[0].getImm()))
1348 .addReg(MI->getOperand(i: 0).getReg())
1349 .addMBB(NextBB);
1350
1351 Br.MI = &MBB->back();
1352 BBInfo[MBB->getNumber()].Size += TII->getInstSizeInBytes(MI: MBB->back());
1353 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1354 BBInfo[MBB->getNumber()].Size += TII->getInstSizeInBytes(MI: MBB->back());
1355 unsigned MaxDisp = getUnconditionalBrDisp(Opc: Br.UncondBr);
1356 ImmBranches.push_back(x: ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1357
1358 // Remove the old conditional branch. It may or may not still be in MBB.
1359 BBInfo[MI->getParent()->getNumber()].Size -= TII->getInstSizeInBytes(MI: *MI);
1360 MI->eraseFromParent();
1361 adjustBBOffsetsAfter(BB: MBB);
1362 return true;
1363}
1364
1365/// Returns a pass that converts branches to long branches.
1366FunctionPass *llvm::createCSKYConstantIslandPass() {
1367 return new CSKYConstantIslands();
1368}
1369
1370INITIALIZE_PASS(CSKYConstantIslands, DEBUG_TYPE,
1371 "CSKY constant island placement and branch shortening pass",
1372 false, false)
1373

source code of llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp