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Reed Kotler5bf80202013-02-27 04:20:14 +00001//===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
Reed Kotlerbb3094a2013-02-27 03:33:58 +00002//
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.
Reed Kotler4d0313d2013-11-05 12:04:37 +000012// For now, only Mips16 will use this.
Reed Kotlerbb3094a2013-02-27 03:33:58 +000013//
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
Alp Tokerf907b892013-12-05 05:44:44 +000020// non-linux targets.
Reed Kotlerbb3094a2013-02-27 03:33:58 +000021//
22//
23
Reed Kotlerbb3094a2013-02-27 03:33:58 +000024#include "Mips.h"
25#include "MCTargetDesc/MipsBaseInfo.h"
Reed Kotler5c8ae092013-11-13 04:37:52 +000026#include "Mips16InstrInfo.h"
Reed Kotler0f007fc2013-11-05 08:14:14 +000027#include "MipsMachineFunction.h"
Reed Kotlerbb3094a2013-02-27 03:33:58 +000028#include "MipsTargetMachine.h"
29#include "llvm/ADT/Statistic.h"
Reed Kotler91ae9822013-10-27 21:57:36 +000030#include "llvm/CodeGen/MachineBasicBlock.h"
Eric Christopher79cc1e32014-09-02 22:28:02 +000031#include "llvm/CodeGen/MachineConstantPool.h"
Reed Kotlerbb3094a2013-02-27 03:33:58 +000032#include "llvm/CodeGen/MachineFunctionPass.h"
33#include "llvm/CodeGen/MachineInstrBuilder.h"
Reed Kotler91ae9822013-10-27 21:57:36 +000034#include "llvm/CodeGen/MachineRegisterInfo.h"
Reed Kotlerbb3094a2013-02-27 03:33:58 +000035#include "llvm/IR/Function.h"
Chandler Carruth83948572014-03-04 10:30:26 +000036#include "llvm/IR/InstIterator.h"
Reed Kotlerbb3094a2013-02-27 03:33:58 +000037#include "llvm/Support/CommandLine.h"
Reed Kotler91ae9822013-10-27 21:57:36 +000038#include "llvm/Support/Debug.h"
Chandler Carruth8a8cd2b2014-01-07 11:48:04 +000039#include "llvm/Support/Format.h"
Reed Kotlerbb3094a2013-02-27 03:33:58 +000040#include "llvm/Support/MathExtras.h"
Reed Kotler91ae9822013-10-27 21:57:36 +000041#include "llvm/Support/raw_ostream.h"
Reed Kotlerbb3094a2013-02-27 03:33:58 +000042#include "llvm/Target/TargetInstrInfo.h"
43#include "llvm/Target/TargetMachine.h"
44#include "llvm/Target/TargetRegisterInfo.h"
Reed Kotler91ae9822013-10-27 21:57:36 +000045#include <algorithm>
Reed Kotlerbb3094a2013-02-27 03:33:58 +000046
47using namespace llvm;
48
Chandler Carruth84e68b22014-04-22 02:41:26 +000049#define DEBUG_TYPE "mips-constant-islands"
50
Reed Kotler91ae9822013-10-27 21:57:36 +000051STATISTIC(NumCPEs, "Number of constpool entries");
Reed Kotler0f007fc2013-11-05 08:14:14 +000052STATISTIC(NumSplit, "Number of uncond branches inserted");
53STATISTIC(NumCBrFixed, "Number of cond branches fixed");
54STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
Reed Kotler91ae9822013-10-27 21:57:36 +000055
56// FIXME: This option should be removed once it has received sufficient testing.
57static cl::opt<bool>
58AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
59 cl::desc("Align constant islands in code"));
60
Reed Kotler0f007fc2013-11-05 08:14:14 +000061
62// Rather than do make check tests with huge amounts of code, we force
63// the test to use this amount.
64//
65static 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
Reed Kotler45c59272013-11-10 00:09:26 +000071//
72// For testing purposes we tell it to not use relaxed load forms so that it
73// will split blocks.
74//
75static 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
Reed Kotler0d409e22013-11-28 00:56:37 +000081static 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:
Reed Kotlerad450f22013-11-29 22:32:56 +000089 case Mips::JalB16:
Reed Kotler0d409e22013-11-28 00:56:37 +000090 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
100static unsigned int longformBranchOpcode(unsigned int Opcode) {
101 switch (Opcode) {
102 case Mips::Bimm16:
103 case Mips::BimmX16:
104 return Mips::BimmX16;
105 case Mips::Bteqz16:
106 case Mips::BteqzX16:
107 return Mips::BteqzX16;
108 case Mips::Btnez16:
109 case Mips::BtnezX16:
110 return Mips::BtnezX16;
Reed Kotlerad450f22013-11-29 22:32:56 +0000111 case Mips::JalB16:
112 return Mips::JalB16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000113 case Mips::BeqzRxImm16:
114 case Mips::BeqzRxImmX16:
115 return Mips::BeqzRxImmX16;
116 case Mips::BnezRxImm16:
117 case Mips::BnezRxImmX16:
118 return Mips::BnezRxImmX16;
119 }
120 llvm_unreachable("Unknown branch type");
121}
122
123//
124// FIXME: need to go through this whole constant islands port and check the math
125// for branch ranges and clean this up and make some functions to calculate things
126// that are done many times identically.
127// Need to refactor some of the code to call this routine.
128//
129static unsigned int branchMaxOffsets(unsigned int Opcode) {
130 unsigned Bits, Scale;
131 switch (Opcode) {
132 case Mips::Bimm16:
133 Bits = 11;
134 Scale = 2;
135 break;
136 case Mips::BimmX16:
137 Bits = 16;
138 Scale = 2;
139 break;
140 case Mips::BeqzRxImm16:
141 Bits = 8;
142 Scale = 2;
143 break;
144 case Mips::BeqzRxImmX16:
145 Bits = 16;
146 Scale = 2;
147 break;
148 case Mips::BnezRxImm16:
149 Bits = 8;
150 Scale = 2;
151 break;
152 case Mips::BnezRxImmX16:
153 Bits = 16;
154 Scale = 2;
155 break;
156 case Mips::Bteqz16:
157 Bits = 8;
158 Scale = 2;
159 break;
160 case Mips::BteqzX16:
161 Bits = 16;
162 Scale = 2;
163 break;
164 case Mips::Btnez16:
165 Bits = 8;
166 Scale = 2;
167 break;
168 case Mips::BtnezX16:
169 Bits = 16;
170 Scale = 2;
171 break;
172 default:
173 llvm_unreachable("Unknown branch type");
174 }
175 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
176 return MaxOffs;
177}
Reed Kotler0f007fc2013-11-05 08:14:14 +0000178
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000179namespace {
Reed Kotler0f007fc2013-11-05 08:14:14 +0000180
181
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000182 typedef MachineBasicBlock::iterator Iter;
183 typedef MachineBasicBlock::reverse_iterator ReverseIter;
184
Reed Kotler0f007fc2013-11-05 08:14:14 +0000185 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
186 /// requires constant pool entries to be scattered among the instructions
187 /// inside a function. To do this, it completely ignores the normal LLVM
188 /// constant pool; instead, it places constants wherever it feels like with
189 /// special instructions.
190 ///
191 /// The terminology used in this pass includes:
192 /// Islands - Clumps of constants placed in the function.
193 /// Water - Potential places where an island could be formed.
194 /// CPE - A constant pool entry that has been placed somewhere, which
195 /// tracks a list of users.
196
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000197 class MipsConstantIslands : public MachineFunctionPass {
198
Reed Kotler0f007fc2013-11-05 08:14:14 +0000199 /// BasicBlockInfo - Information about the offset and size of a single
200 /// basic block.
201 struct BasicBlockInfo {
202 /// Offset - Distance from the beginning of the function to the beginning
203 /// of this basic block.
204 ///
205 /// Offsets are computed assuming worst case padding before an aligned
206 /// block. This means that subtracting basic block offsets always gives a
207 /// conservative estimate of the real distance which may be smaller.
208 ///
209 /// Because worst case padding is used, the computed offset of an aligned
210 /// block may not actually be aligned.
211 unsigned Offset;
212
213 /// Size - Size of the basic block in bytes. If the block contains
214 /// inline assembly, this is a worst case estimate.
215 ///
216 /// The size does not include any alignment padding whether from the
217 /// beginning of the block, or from an aligned jump table at the end.
218 unsigned Size;
219
Reed Kotler7ded5b62013-11-05 23:36:58 +0000220 // FIXME: ignore LogAlign for this patch
221 //
Reed Kotler0f007fc2013-11-05 08:14:14 +0000222 unsigned postOffset(unsigned LogAlign = 0) const {
223 unsigned PO = Offset + Size;
224 return PO;
225 }
226
Reed Kotler7ded5b62013-11-05 23:36:58 +0000227 BasicBlockInfo() : Offset(0), Size(0) {}
228
Reed Kotler0f007fc2013-11-05 08:14:14 +0000229 };
230
231 std::vector<BasicBlockInfo> BBInfo;
232
233 /// WaterList - A sorted list of basic blocks where islands could be placed
234 /// (i.e. blocks that don't fall through to the following block, due
235 /// to a return, unreachable, or unconditional branch).
236 std::vector<MachineBasicBlock*> WaterList;
237
238 /// NewWaterList - The subset of WaterList that was created since the
239 /// previous iteration by inserting unconditional branches.
240 SmallSet<MachineBasicBlock*, 4> NewWaterList;
241
242 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
243
244 /// CPUser - One user of a constant pool, keeping the machine instruction
245 /// pointer, the constant pool being referenced, and the max displacement
246 /// allowed from the instruction to the CP. The HighWaterMark records the
247 /// highest basic block where a new CPEntry can be placed. To ensure this
248 /// pass terminates, the CP entries are initially placed at the end of the
249 /// function and then move monotonically to lower addresses. The
250 /// exception to this rule is when the current CP entry for a particular
251 /// CPUser is out of range, but there is another CP entry for the same
252 /// constant value in range. We want to use the existing in-range CP
253 /// entry, but if it later moves out of range, the search for new water
254 /// should resume where it left off. The HighWaterMark is used to record
255 /// that point.
256 struct CPUser {
257 MachineInstr *MI;
258 MachineInstr *CPEMI;
259 MachineBasicBlock *HighWaterMark;
260 private:
261 unsigned MaxDisp;
262 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
263 // with different displacements
264 unsigned LongFormOpcode;
265 public:
266 bool NegOk;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000267 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
Reed Kotlerb09ebe92013-11-05 22:34:29 +0000268 bool neg,
Reed Kotler0f007fc2013-11-05 08:14:14 +0000269 unsigned longformmaxdisp, unsigned longformopcode)
270 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
271 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
Reed Kotler7ded5b62013-11-05 23:36:58 +0000272 NegOk(neg){
Reed Kotler0f007fc2013-11-05 08:14:14 +0000273 HighWaterMark = CPEMI->getParent();
274 }
275 /// getMaxDisp - Returns the maximum displacement supported by MI.
Reed Kotler0f007fc2013-11-05 08:14:14 +0000276 unsigned getMaxDisp() const {
277 unsigned xMaxDisp = ConstantIslandsSmallOffset?
278 ConstantIslandsSmallOffset: MaxDisp;
Reed Kotler7ded5b62013-11-05 23:36:58 +0000279 return xMaxDisp;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000280 }
Reed Kotler45c59272013-11-10 00:09:26 +0000281 void setMaxDisp(unsigned val) {
282 MaxDisp = val;
283 }
Reed Kotler0f007fc2013-11-05 08:14:14 +0000284 unsigned getLongFormMaxDisp() const {
Reed Kotler7ded5b62013-11-05 23:36:58 +0000285 return LongFormMaxDisp;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000286 }
287 unsigned getLongFormOpcode() const {
288 return LongFormOpcode;
289 }
290 };
291
292 /// CPUsers - Keep track of all of the machine instructions that use various
293 /// constant pools and their max displacement.
294 std::vector<CPUser> CPUsers;
Reed Kotler91ae9822013-10-27 21:57:36 +0000295
296 /// CPEntry - One per constant pool entry, keeping the machine instruction
297 /// pointer, the constpool index, and the number of CPUser's which
298 /// reference this entry.
299 struct CPEntry {
300 MachineInstr *CPEMI;
301 unsigned CPI;
302 unsigned RefCount;
303 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
304 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
305 };
306
307 /// CPEntries - Keep track of all of the constant pool entry machine
308 /// instructions. For each original constpool index (i.e. those that
309 /// existed upon entry to this pass), it keeps a vector of entries.
310 /// Original elements are cloned as we go along; the clones are
311 /// put in the vector of the original element, but have distinct CPIs.
312 std::vector<std::vector<CPEntry> > CPEntries;
313
Reed Kotler0f007fc2013-11-05 08:14:14 +0000314 /// ImmBranch - One per immediate branch, keeping the machine instruction
315 /// pointer, conditional or unconditional, the max displacement,
316 /// and (if isCond is true) the corresponding unconditional branch
317 /// opcode.
318 struct ImmBranch {
319 MachineInstr *MI;
320 unsigned MaxDisp : 31;
321 bool isCond : 1;
322 int UncondBr;
323 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
324 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
325 };
326
327 /// ImmBranches - Keep track of all the immediate branch instructions.
328 ///
329 std::vector<ImmBranch> ImmBranches;
330
331 /// HasFarJump - True if any far jump instruction has been emitted during
332 /// the branch fix up pass.
333 bool HasFarJump;
334
335 const TargetMachine &TM;
336 bool IsPIC;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000337 const MipsSubtarget *STI;
Reed Kotler5c8ae092013-11-13 04:37:52 +0000338 const Mips16InstrInfo *TII;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000339 MipsFunctionInfo *MFI;
340 MachineFunction *MF;
341 MachineConstantPool *MCP;
342
343 unsigned PICLabelUId;
344 bool PrescannedForConstants;
345
346 void initPICLabelUId(unsigned UId) {
347 PICLabelUId = UId;
348 }
349
350
351 unsigned createPICLabelUId() {
352 return PICLabelUId++;
353 }
354
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000355 public:
356 static char ID;
357 MipsConstantIslands(TargetMachine &tm)
Eric Christopher4e7d1e72014-07-18 23:41:32 +0000358 : MachineFunctionPass(ID), TM(tm),
Daniel Sanderse2e25da2014-10-24 16:15:27 +0000359 IsPIC(TM.getRelocationModel() == Reloc::PIC_), STI(nullptr),
Eric Christopher4e7d1e72014-07-18 23:41:32 +0000360 MF(nullptr), MCP(nullptr), PrescannedForConstants(false) {}
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000361
Craig Topper56c590a2014-04-29 07:58:02 +0000362 const char *getPassName() const override {
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000363 return "Mips Constant Islands";
364 }
365
Craig Topper56c590a2014-04-29 07:58:02 +0000366 bool runOnMachineFunction(MachineFunction &F) override;
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000367
Derek Schuff1dbf7a52016-04-04 17:09:25 +0000368 MachineFunctionProperties getRequiredProperties() const override {
369 return MachineFunctionProperties().set(
370 MachineFunctionProperties::Property::AllVRegsAllocated);
371 }
372
Reed Kotler91ae9822013-10-27 21:57:36 +0000373 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000374 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
375 unsigned getCPELogAlign(const MachineInstr *CPEMI);
376 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
377 unsigned getOffsetOf(MachineInstr *MI) const;
378 unsigned getUserOffset(CPUser&) const;
379 void dumpBBs();
Reed Kotler0f007fc2013-11-05 08:14:14 +0000380
381 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
Reed Kotlerb09ebe92013-11-05 22:34:29 +0000382 unsigned Disp, bool NegativeOK);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000383 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
384 const CPUser &U);
385
Reed Kotler0f007fc2013-11-05 08:14:14 +0000386 void computeBlockSize(MachineBasicBlock *MBB);
387 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
388 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
389 void adjustBBOffsetsAfter(MachineBasicBlock *BB);
390 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
391 int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
392 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
393 bool findAvailableWater(CPUser&U, unsigned UserOffset,
394 water_iterator &WaterIter);
395 void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
396 MachineBasicBlock *&NewMBB);
397 bool handleConstantPoolUser(unsigned CPUserIndex);
398 void removeDeadCPEMI(MachineInstr *CPEMI);
399 bool removeUnusedCPEntries();
400 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
401 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
402 bool DoDump = false);
403 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
404 CPUser &U, unsigned &Growth);
405 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
406 bool fixupImmediateBr(ImmBranch &Br);
407 bool fixupConditionalBr(ImmBranch &Br);
408 bool fixupUnconditionalBr(ImmBranch &Br);
Reed Kotler91ae9822013-10-27 21:57:36 +0000409
410 void prescanForConstants();
411
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000412 private:
Reed Kotler91ae9822013-10-27 21:57:36 +0000413
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000414 };
415
416 char MipsConstantIslands::ID = 0;
417} // end of anonymous namespace
418
Reed Kotler0f007fc2013-11-05 08:14:14 +0000419bool MipsConstantIslands::isOffsetInRange
420 (unsigned UserOffset, unsigned TrialOffset,
421 const CPUser &U) {
422 return isOffsetInRange(UserOffset, TrialOffset,
Reed Kotlerb09ebe92013-11-05 22:34:29 +0000423 U.getMaxDisp(), U.NegOk);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000424}
425/// print block size and offset information - debugging
426void MipsConstantIslands::dumpBBs() {
427 DEBUG({
428 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
429 const BasicBlockInfo &BBI = BBInfo[J];
430 dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
Reed Kotler0f007fc2013-11-05 08:14:14 +0000431 << format(" size=%#x\n", BBInfo[J].Size);
432 }
433 });
434}
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000435/// createMipsLongBranchPass - Returns a pass that converts branches to long
436/// branches.
437FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
438 return new MipsConstantIslands(tm);
439}
440
Reed Kotler91ae9822013-10-27 21:57:36 +0000441bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
Reed Kotler1595f362013-04-09 19:46:01 +0000442 // The intention is for this to be a mips16 only pass for now
443 // FIXME:
Reed Kotler91ae9822013-10-27 21:57:36 +0000444 MF = &mf;
445 MCP = mf.getConstantPool();
Eric Christopher96e72c62015-01-29 23:27:36 +0000446 STI = &static_cast<const MipsSubtarget &>(mf.getSubtarget());
Reed Kotler91ae9822013-10-27 21:57:36 +0000447 DEBUG(dbgs() << "constant island machine function " << "\n");
Eric Christopher4e7d1e72014-07-18 23:41:32 +0000448 if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) {
Reed Kotler91ae9822013-10-27 21:57:36 +0000449 return false;
450 }
Eric Christopher96e72c62015-01-29 23:27:36 +0000451 TII = (const Mips16InstrInfo *)STI->getInstrInfo();
Reed Kotler0f007fc2013-11-05 08:14:14 +0000452 MFI = MF->getInfo<MipsFunctionInfo>();
Reed Kotler91ae9822013-10-27 21:57:36 +0000453 DEBUG(dbgs() << "constant island processing " << "\n");
454 //
455 // will need to make predermination if there is any constants we need to
456 // put in constant islands. TBD.
457 //
Reed Kotler0f007fc2013-11-05 08:14:14 +0000458 if (!PrescannedForConstants) prescanForConstants();
Reed Kotler91ae9822013-10-27 21:57:36 +0000459
Reed Kotler0f007fc2013-11-05 08:14:14 +0000460 HasFarJump = false;
Reed Kotler91ae9822013-10-27 21:57:36 +0000461 // This pass invalidates liveness information when it splits basic blocks.
462 MF->getRegInfo().invalidateLiveness();
463
464 // Renumber all of the machine basic blocks in the function, guaranteeing that
465 // the numbers agree with the position of the block in the function.
466 MF->RenumberBlocks();
467
Reed Kotler0f007fc2013-11-05 08:14:14 +0000468 bool MadeChange = false;
469
Reed Kotler91ae9822013-10-27 21:57:36 +0000470 // Perform the initial placement of the constant pool entries. To start with,
471 // we put them all at the end of the function.
472 std::vector<MachineInstr*> CPEMIs;
473 if (!MCP->isEmpty())
474 doInitialPlacement(CPEMIs);
475
Reed Kotler0f007fc2013-11-05 08:14:14 +0000476 /// The next UID to take is the first unused one.
477 initPICLabelUId(CPEMIs.size());
478
479 // Do the initial scan of the function, building up information about the
480 // sizes of each block, the location of all the water, and finding all of the
481 // constant pool users.
482 initializeFunctionInfo(CPEMIs);
483 CPEMIs.clear();
484 DEBUG(dumpBBs());
485
486 /// Remove dead constant pool entries.
487 MadeChange |= removeUnusedCPEntries();
488
489 // Iteratively place constant pool entries and fix up branches until there
490 // is no change.
491 unsigned NoCPIters = 0, NoBRIters = 0;
492 (void)NoBRIters;
493 while (true) {
494 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
495 bool CPChange = false;
496 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
497 CPChange |= handleConstantPoolUser(i);
498 if (CPChange && ++NoCPIters > 30)
499 report_fatal_error("Constant Island pass failed to converge!");
500 DEBUG(dumpBBs());
501
502 // Clear NewWaterList now. If we split a block for branches, it should
503 // appear as "new water" for the next iteration of constant pool placement.
504 NewWaterList.clear();
505
506 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
507 bool BRChange = false;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000508 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
509 BRChange |= fixupImmediateBr(ImmBranches[i]);
510 if (BRChange && ++NoBRIters > 30)
511 report_fatal_error("Branch Fix Up pass failed to converge!");
512 DEBUG(dumpBBs());
Reed Kotler0f007fc2013-11-05 08:14:14 +0000513 if (!CPChange && !BRChange)
514 break;
515 MadeChange = true;
516 }
517
518 DEBUG(dbgs() << '\n'; dumpBBs());
519
520 BBInfo.clear();
521 WaterList.clear();
522 CPUsers.clear();
523 CPEntries.clear();
524 ImmBranches.clear();
525 return MadeChange;
Reed Kotlerbb3094a2013-02-27 03:33:58 +0000526}
527
Reed Kotler91ae9822013-10-27 21:57:36 +0000528/// doInitialPlacement - Perform the initial placement of the constant pool
529/// entries. To start with, we put them all at the end of the function.
530void
531MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
532 // Create the basic block to hold the CPE's.
533 MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
534 MF->push_back(BB);
535
536
537 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
538 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
539
540 // Mark the basic block as required by the const-pool.
541 // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
542 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
543
544 // The function needs to be as aligned as the basic blocks. The linker may
545 // move functions around based on their alignment.
546 MF->ensureAlignment(BB->getAlignment());
547
548 // Order the entries in BB by descending alignment. That ensures correct
549 // alignment of all entries as long as BB is sufficiently aligned. Keep
550 // track of the insertion point for each alignment. We are going to bucket
551 // sort the entries as they are created.
552 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
553
554 // Add all of the constants from the constant pool to the end block, use an
555 // identity mapping of CPI's to CPE's.
556 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
557
Mehdi Aminibd7287e2015-07-16 06:11:10 +0000558 const DataLayout &TD = MF->getDataLayout();
Reed Kotler91ae9822013-10-27 21:57:36 +0000559 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
560 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
561 assert(Size >= 4 && "Too small constant pool entry");
562 unsigned Align = CPs[i].getAlignment();
563 assert(isPowerOf2_32(Align) && "Invalid alignment");
564 // Verify that all constant pool entries are a multiple of their alignment.
565 // If not, we would have to pad them out so that instructions stay aligned.
566 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
567
568 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
569 unsigned LogAlign = Log2_32(Align);
570 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
571
572 MachineInstr *CPEMI =
573 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
574 .addImm(i).addConstantPoolIndex(i).addImm(Size);
575
576 CPEMIs.push_back(CPEMI);
577
578 // Ensure that future entries with higher alignment get inserted before
579 // CPEMI. This is bucket sort with iterators.
580 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
581 if (InsPoint[a] == InsAt)
582 InsPoint[a] = CPEMI;
583 // Add a new CPEntry, but no corresponding CPUser yet.
Benjamin Kramere12a6ba2014-10-03 18:33:16 +0000584 CPEntries.emplace_back(1, CPEntry(CPEMI, i));
Reed Kotler91ae9822013-10-27 21:57:36 +0000585 ++NumCPEs;
586 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
587 << Size << ", align = " << Align <<'\n');
588 }
589 DEBUG(BB->dump());
590}
591
Reed Kotler0f007fc2013-11-05 08:14:14 +0000592/// BBHasFallthrough - Return true if the specified basic block can fallthrough
593/// into the block immediately after it.
594static bool BBHasFallthrough(MachineBasicBlock *MBB) {
595 // Get the next machine basic block in the function.
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +0000596 MachineFunction::iterator MBBI = MBB->getIterator();
Reed Kotler0f007fc2013-11-05 08:14:14 +0000597 // Can't fall off end of function.
Benjamin Kramerb6d0bd42014-03-02 12:27:27 +0000598 if (std::next(MBBI) == MBB->getParent()->end())
Reed Kotler0f007fc2013-11-05 08:14:14 +0000599 return false;
600
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +0000601 MachineBasicBlock *NextBB = &*std::next(MBBI);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000602 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
603 E = MBB->succ_end(); I != E; ++I)
604 if (*I == NextBB)
605 return true;
606
607 return false;
608}
609
610/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
611/// look up the corresponding CPEntry.
612MipsConstantIslands::CPEntry
613*MipsConstantIslands::findConstPoolEntry(unsigned CPI,
614 const MachineInstr *CPEMI) {
615 std::vector<CPEntry> &CPEs = CPEntries[CPI];
616 // Number of entries per constpool index should be small, just do a
617 // linear search.
618 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
619 if (CPEs[i].CPEMI == CPEMI)
620 return &CPEs[i];
621 }
Craig Topper062a2ba2014-04-25 05:30:21 +0000622 return nullptr;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000623}
624
625/// getCPELogAlign - Returns the required alignment of the constant pool entry
626/// represented by CPEMI. Alignment is measured in log2(bytes) units.
627unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
628 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY);
629
630 // Everything is 4-byte aligned unless AlignConstantIslands is set.
631 if (!AlignConstantIslands)
632 return 2;
633
634 unsigned CPI = CPEMI->getOperand(1).getIndex();
635 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
636 unsigned Align = MCP->getConstants()[CPI].getAlignment();
637 assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
638 return Log2_32(Align);
639}
640
641/// initializeFunctionInfo - Do the initial scan of the function, building up
642/// information about the sizes of each block, the location of all the water,
643/// and finding all of the constant pool users.
644void MipsConstantIslands::
645initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
646 BBInfo.clear();
647 BBInfo.resize(MF->getNumBlockIDs());
648
649 // First thing, compute the size of all basic blocks, and see if the function
650 // has any inline assembly in it. If so, we have to be conservative about
651 // alignment assumptions, as we don't know for sure the size of any
652 // instructions in the inline assembly.
653 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +0000654 computeBlockSize(&*I);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000655
Reed Kotler0f007fc2013-11-05 08:14:14 +0000656
657 // Compute block offsets.
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +0000658 adjustBBOffsetsAfter(&MF->front());
Reed Kotler0f007fc2013-11-05 08:14:14 +0000659
660 // Now go back through the instructions and build up our data structures.
661 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
662 MBBI != E; ++MBBI) {
663 MachineBasicBlock &MBB = *MBBI;
664
665 // If this block doesn't fall through into the next MBB, then this is
666 // 'water' that a constant pool island could be placed.
667 if (!BBHasFallthrough(&MBB))
668 WaterList.push_back(&MBB);
669 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
670 I != E; ++I) {
671 if (I->isDebugValue())
672 continue;
673
674 int Opc = I->getOpcode();
675 if (I->isBranch()) {
676 bool isCond = false;
677 unsigned Bits = 0;
678 unsigned Scale = 1;
679 int UOpc = Opc;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000680 switch (Opc) {
681 default:
Reed Kotler4b7afe52013-11-13 23:52:18 +0000682 continue; // Ignore other branches for now
683 case Mips::Bimm16:
684 Bits = 11;
685 Scale = 2;
686 isCond = false;
687 break;
688 case Mips::BimmX16:
689 Bits = 16;
690 Scale = 2;
691 isCond = false;
Reed Kotler0d409e22013-11-28 00:56:37 +0000692 break;
693 case Mips::BeqzRxImm16:
Reed Kotler59975c22013-12-03 23:42:51 +0000694 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000695 Bits = 8;
696 Scale = 2;
697 isCond = true;
698 break;
699 case Mips::BeqzRxImmX16:
Reed Kotler59975c22013-12-03 23:42:51 +0000700 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000701 Bits = 16;
702 Scale = 2;
703 isCond = true;
704 break;
705 case Mips::BnezRxImm16:
Reed Kotler59975c22013-12-03 23:42:51 +0000706 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000707 Bits = 8;
708 Scale = 2;
709 isCond = true;
710 break;
711 case Mips::BnezRxImmX16:
Reed Kotler59975c22013-12-03 23:42:51 +0000712 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000713 Bits = 16;
714 Scale = 2;
715 isCond = true;
716 break;
717 case Mips::Bteqz16:
Reed Kotler59975c22013-12-03 23:42:51 +0000718 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000719 Bits = 8;
720 Scale = 2;
721 isCond = true;
722 break;
723 case Mips::BteqzX16:
Reed Kotler59975c22013-12-03 23:42:51 +0000724 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000725 Bits = 16;
726 Scale = 2;
727 isCond = true;
728 break;
729 case Mips::Btnez16:
Reed Kotler59975c22013-12-03 23:42:51 +0000730 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000731 Bits = 8;
732 Scale = 2;
733 isCond = true;
734 break;
735 case Mips::BtnezX16:
Reed Kotler59975c22013-12-03 23:42:51 +0000736 UOpc=Mips::Bimm16;
Reed Kotler0d409e22013-11-28 00:56:37 +0000737 Bits = 16;
738 Scale = 2;
739 isCond = true;
740 break;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000741 }
742 // Record this immediate branch.
743 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
744 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
Reed Kotler0f007fc2013-11-05 08:14:14 +0000745 }
Reed Kotler0f007fc2013-11-05 08:14:14 +0000746
747 if (Opc == Mips::CONSTPOOL_ENTRY)
748 continue;
749
750
751 // Scan the instructions for constant pool operands.
752 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
753 if (I->getOperand(op).isCPI()) {
754
755 // We found one. The addressing mode tells us the max displacement
756 // from the PC that this instruction permits.
757
758 // Basic size info comes from the TSFlags field.
759 unsigned Bits = 0;
760 unsigned Scale = 1;
761 bool NegOk = false;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000762 unsigned LongFormBits = 0;
763 unsigned LongFormScale = 0;
764 unsigned LongFormOpcode = 0;
765 switch (Opc) {
766 default:
767 llvm_unreachable("Unknown addressing mode for CP reference!");
768 case Mips::LwRxPcTcp16:
769 Bits = 8;
Reed Kotler3d7b33f2013-11-06 04:29:52 +0000770 Scale = 4;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000771 LongFormOpcode = Mips::LwRxPcTcpX16;
Reed Kotler43788a22014-01-16 00:47:46 +0000772 LongFormBits = 14;
Reed Kotler45c59272013-11-10 00:09:26 +0000773 LongFormScale = 1;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000774 break;
775 case Mips::LwRxPcTcpX16:
Reed Kotler43788a22014-01-16 00:47:46 +0000776 Bits = 14;
Reed Kotler3d7b33f2013-11-06 04:29:52 +0000777 Scale = 1;
778 NegOk = true;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000779 break;
780 }
781 // Remember that this is a user of a CP entry.
782 unsigned CPI = I->getOperand(op).getIndex();
783 MachineInstr *CPEMI = CPEMIs[CPI];
784 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
785 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
786 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk,
Reed Kotlerb09ebe92013-11-05 22:34:29 +0000787 LongFormMaxOffs, LongFormOpcode));
Reed Kotler0f007fc2013-11-05 08:14:14 +0000788
789 // Increment corresponding CPEntry reference count.
790 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
791 assert(CPE && "Cannot find a corresponding CPEntry!");
792 CPE->RefCount++;
793
794 // Instructions can only use one CP entry, don't bother scanning the
795 // rest of the operands.
796 break;
797
798 }
799
800 }
801 }
802
803}
804
805/// computeBlockSize - Compute the size and some alignment information for MBB.
806/// This function updates BBInfo directly.
807void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
808 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
809 BBI.Size = 0;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000810
811 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
812 ++I)
813 BBI.Size += TII->GetInstSizeInBytes(I);
814
815}
816
817/// getOffsetOf - Return the current offset of the specified machine instruction
818/// from the start of the function. This offset changes as stuff is moved
819/// around inside the function.
820unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
821 MachineBasicBlock *MBB = MI->getParent();
822
823 // The offset is composed of two things: the sum of the sizes of all MBB's
824 // before this instruction's block, and the offset from the start of the block
825 // it is in.
826 unsigned Offset = BBInfo[MBB->getNumber()].Offset;
827
828 // Sum instructions before MI in MBB.
829 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
830 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
831 Offset += TII->GetInstSizeInBytes(I);
832 }
833 return Offset;
834}
835
836/// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
837/// ID.
838static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
839 const MachineBasicBlock *RHS) {
840 return LHS->getNumber() < RHS->getNumber();
841}
842
843/// updateForInsertedWaterBlock - When a block is newly inserted into the
844/// machine function, it upsets all of the block numbers. Renumber the blocks
845/// and update the arrays that parallel this numbering.
846void MipsConstantIslands::updateForInsertedWaterBlock
847 (MachineBasicBlock *NewBB) {
848 // Renumber the MBB's to keep them consecutive.
849 NewBB->getParent()->RenumberBlocks(NewBB);
850
851 // Insert an entry into BBInfo to align it properly with the (newly
852 // renumbered) block numbers.
853 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
854
855 // Next, update WaterList. Specifically, we need to add NewMBB as having
856 // available water after it.
857 water_iterator IP =
858 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
859 CompareMBBNumbers);
860 WaterList.insert(IP, NewBB);
861}
862
Reed Kotler0f007fc2013-11-05 08:14:14 +0000863unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
Reed Kotler0eb87392013-11-05 21:39:57 +0000864 return getOffsetOf(U.MI);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000865}
866
867/// Split the basic block containing MI into two blocks, which are joined by
868/// an unconditional branch. Update data structures and renumber blocks to
869/// account for this change and returns the newly created block.
870MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr
871 (MachineInstr *MI) {
872 MachineBasicBlock *OrigBB = MI->getParent();
873
874 // Create a new MBB for the code after the OrigBB.
875 MachineBasicBlock *NewBB =
876 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +0000877 MachineFunction::iterator MBBI = ++OrigBB->getIterator();
Reed Kotler0f007fc2013-11-05 08:14:14 +0000878 MF->insert(MBBI, NewBB);
879
880 // Splice the instructions starting with MI over to NewBB.
881 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
882
883 // Add an unconditional branch from OrigBB to NewBB.
884 // Note the new unconditional branch is not being recorded.
885 // There doesn't seem to be meaningful DebugInfo available; this doesn't
886 // correspond to anything in the source.
Reed Kotlerf0e69682013-11-12 02:27:12 +0000887 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000888 ++NumSplit;
889
890 // Update the CFG. All succs of OrigBB are now succs of NewBB.
891 NewBB->transferSuccessors(OrigBB);
892
893 // OrigBB branches to NewBB.
894 OrigBB->addSuccessor(NewBB);
895
896 // Update internal data structures to account for the newly inserted MBB.
897 // This is almost the same as updateForInsertedWaterBlock, except that
898 // the Water goes after OrigBB, not NewBB.
899 MF->RenumberBlocks(NewBB);
900
901 // Insert an entry into BBInfo to align it properly with the (newly
902 // renumbered) block numbers.
903 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
904
905 // Next, update WaterList. Specifically, we need to add OrigMBB as having
906 // available water after it (but not if it's already there, which happens
907 // when splitting before a conditional branch that is followed by an
908 // unconditional branch - in that case we want to insert NewBB).
909 water_iterator IP =
910 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
911 CompareMBBNumbers);
912 MachineBasicBlock* WaterBB = *IP;
913 if (WaterBB == OrigBB)
Benjamin Kramerb6d0bd42014-03-02 12:27:27 +0000914 WaterList.insert(std::next(IP), NewBB);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000915 else
916 WaterList.insert(IP, OrigBB);
917 NewWaterList.insert(OrigBB);
918
919 // Figure out how large the OrigBB is. As the first half of the original
920 // block, it cannot contain a tablejump. The size includes
921 // the new jump we added. (It should be possible to do this without
922 // recounting everything, but it's very confusing, and this is rarely
923 // executed.)
924 computeBlockSize(OrigBB);
925
926 // Figure out how large the NewMBB is. As the second half of the original
927 // block, it may contain a tablejump.
928 computeBlockSize(NewBB);
929
930 // All BBOffsets following these blocks must be modified.
931 adjustBBOffsetsAfter(OrigBB);
932
933 return NewBB;
934}
935
936
937
938/// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
939/// reference) is within MaxDisp of TrialOffset (a proposed location of a
940/// constant pool entry).
Reed Kotler0f007fc2013-11-05 08:14:14 +0000941bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
942 unsigned TrialOffset, unsigned MaxDisp,
Reed Kotlerb09ebe92013-11-05 22:34:29 +0000943 bool NegativeOK) {
Reed Kotler0f007fc2013-11-05 08:14:14 +0000944 if (UserOffset <= TrialOffset) {
945 // User before the Trial.
946 if (TrialOffset - UserOffset <= MaxDisp)
947 return true;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000948 } else if (NegativeOK) {
949 if (UserOffset - TrialOffset <= MaxDisp)
950 return true;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000951 }
952 return false;
953}
954
955/// isWaterInRange - Returns true if a CPE placed after the specified
956/// Water (a basic block) will be in range for the specific MI.
957///
958/// Compute how much the function will grow by inserting a CPE after Water.
959bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
960 MachineBasicBlock* Water, CPUser &U,
961 unsigned &Growth) {
962 unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
963 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
964 unsigned NextBlockOffset, NextBlockAlignment;
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +0000965 MachineFunction::const_iterator NextBlock = ++Water->getIterator();
966 if (NextBlock == MF->end()) {
Reed Kotler0f007fc2013-11-05 08:14:14 +0000967 NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
968 NextBlockAlignment = 0;
969 } else {
970 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
971 NextBlockAlignment = NextBlock->getAlignment();
972 }
973 unsigned Size = U.CPEMI->getOperand(2).getImm();
974 unsigned CPEEnd = CPEOffset + Size;
975
976 // The CPE may be able to hide in the alignment padding before the next
977 // block. It may also cause more padding to be required if it is more aligned
978 // that the next block.
979 if (CPEEnd > NextBlockOffset) {
980 Growth = CPEEnd - NextBlockOffset;
981 // Compute the padding that would go at the end of the CPE to align the next
982 // block.
Aaron Ballmanef0fe1e2016-03-30 21:30:00 +0000983 Growth += OffsetToAlignment(CPEEnd, 1ULL << NextBlockAlignment);
Reed Kotler0f007fc2013-11-05 08:14:14 +0000984
985 // If the CPE is to be inserted before the instruction, that will raise
986 // the offset of the instruction. Also account for unknown alignment padding
987 // in blocks between CPE and the user.
988 if (CPEOffset < UserOffset)
Reed Kotler7ded5b62013-11-05 23:36:58 +0000989 UserOffset += Growth;
Reed Kotler0f007fc2013-11-05 08:14:14 +0000990 } else
991 // CPE fits in existing padding.
992 Growth = 0;
993
994 return isOffsetInRange(UserOffset, CPEOffset, U);
995}
996
997/// isCPEntryInRange - Returns true if the distance between specific MI and
998/// specific ConstPool entry instruction can fit in MI's displacement field.
999bool MipsConstantIslands::isCPEntryInRange
1000 (MachineInstr *MI, unsigned UserOffset,
1001 MachineInstr *CPEMI, unsigned MaxDisp,
1002 bool NegOk, bool DoDump) {
1003 unsigned CPEOffset = getOffsetOf(CPEMI);
1004
1005 if (DoDump) {
1006 DEBUG({
1007 unsigned Block = MI->getParent()->getNumber();
1008 const BasicBlockInfo &BBI = BBInfo[Block];
1009 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
1010 << " max delta=" << MaxDisp
1011 << format(" insn address=%#x", UserOffset)
1012 << " in BB#" << Block << ": "
1013 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
1014 << format("CPE address=%#x offset=%+d: ", CPEOffset,
1015 int(CPEOffset-UserOffset));
1016 });
1017 }
1018
1019 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
1020}
1021
1022#ifndef NDEBUG
1023/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
1024/// unconditionally branches to its only successor.
1025static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
1026 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
1027 return false;
1028 MachineBasicBlock *Succ = *MBB->succ_begin();
1029 MachineBasicBlock *Pred = *MBB->pred_begin();
1030 MachineInstr *PredMI = &Pred->back();
Reed Kotlerf0e69682013-11-12 02:27:12 +00001031 if (PredMI->getOpcode() == Mips::Bimm16)
Reed Kotler0f007fc2013-11-05 08:14:14 +00001032 return PredMI->getOperand(0).getMBB() == Succ;
1033 return false;
1034}
1035#endif
1036
1037void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
1038 unsigned BBNum = BB->getNumber();
1039 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
1040 // Get the offset and known bits at the end of the layout predecessor.
1041 // Include the alignment of the current block.
Reed Kotler7ded5b62013-11-05 23:36:58 +00001042 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001043 BBInfo[i].Offset = Offset;
1044 }
1045}
1046
1047/// decrementCPEReferenceCount - find the constant pool entry with index CPI
1048/// and instruction CPEMI, and decrement its refcount. If the refcount
1049/// becomes 0 remove the entry and instruction. Returns true if we removed
1050/// the entry, false if we didn't.
1051
1052bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
1053 MachineInstr *CPEMI) {
1054 // Find the old entry. Eliminate it if it is no longer used.
1055 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
1056 assert(CPE && "Unexpected!");
1057 if (--CPE->RefCount == 0) {
1058 removeDeadCPEMI(CPEMI);
Craig Topper062a2ba2014-04-25 05:30:21 +00001059 CPE->CPEMI = nullptr;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001060 --NumCPEs;
1061 return true;
1062 }
1063 return false;
1064}
1065
1066/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1067/// if not, see if an in-range clone of the CPE is in range, and if so,
1068/// change the data structures so the user references the clone. Returns:
1069/// 0 = no existing entry found
1070/// 1 = entry found, and there were no code insertions or deletions
1071/// 2 = entry found, and there were code insertions or deletions
1072int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1073{
1074 MachineInstr *UserMI = U.MI;
1075 MachineInstr *CPEMI = U.CPEMI;
1076
1077 // Check to see if the CPE is already in-range.
1078 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1079 true)) {
1080 DEBUG(dbgs() << "In range\n");
1081 return 1;
1082 }
1083
1084 // No. Look for previously created clones of the CPE that are in range.
1085 unsigned CPI = CPEMI->getOperand(1).getIndex();
1086 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1087 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1088 // We already tried this one
1089 if (CPEs[i].CPEMI == CPEMI)
1090 continue;
1091 // Removing CPEs can leave empty entries, skip
Craig Topper062a2ba2014-04-25 05:30:21 +00001092 if (CPEs[i].CPEMI == nullptr)
Reed Kotler0f007fc2013-11-05 08:14:14 +00001093 continue;
1094 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1095 U.NegOk)) {
1096 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1097 << CPEs[i].CPI << "\n");
1098 // Point the CPUser node to the replacement
1099 U.CPEMI = CPEs[i].CPEMI;
1100 // Change the CPI in the instruction operand to refer to the clone.
1101 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1102 if (UserMI->getOperand(j).isCPI()) {
1103 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1104 break;
1105 }
1106 // Adjust the refcount of the clone...
1107 CPEs[i].RefCount++;
1108 // ...and the original. If we didn't remove the old entry, none of the
1109 // addresses changed, so we don't need another pass.
1110 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1111 }
1112 }
1113 return 0;
1114}
1115
1116/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1117/// This version checks if the longer form of the instruction can be used to
1118/// to satisfy things.
1119/// if not, see if an in-range clone of the CPE is in range, and if so,
1120/// change the data structures so the user references the clone. Returns:
1121/// 0 = no existing entry found
1122/// 1 = entry found, and there were no code insertions or deletions
1123/// 2 = entry found, and there were code insertions or deletions
1124int MipsConstantIslands::findLongFormInRangeCPEntry
1125 (CPUser& U, unsigned UserOffset)
1126{
1127 MachineInstr *UserMI = U.MI;
1128 MachineInstr *CPEMI = U.CPEMI;
1129
1130 // Check to see if the CPE is already in-range.
1131 if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1132 U.getLongFormMaxDisp(), U.NegOk,
1133 true)) {
1134 DEBUG(dbgs() << "In range\n");
1135 UserMI->setDesc(TII->get(U.getLongFormOpcode()));
Reed Kotler45c59272013-11-10 00:09:26 +00001136 U.setMaxDisp(U.getLongFormMaxDisp());
Reed Kotler0f007fc2013-11-05 08:14:14 +00001137 return 2; // instruction is longer length now
1138 }
1139
1140 // No. Look for previously created clones of the CPE that are in range.
1141 unsigned CPI = CPEMI->getOperand(1).getIndex();
1142 std::vector<CPEntry> &CPEs = CPEntries[CPI];
1143 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1144 // We already tried this one
1145 if (CPEs[i].CPEMI == CPEMI)
1146 continue;
1147 // Removing CPEs can leave empty entries, skip
Craig Topper062a2ba2014-04-25 05:30:21 +00001148 if (CPEs[i].CPEMI == nullptr)
Reed Kotler0f007fc2013-11-05 08:14:14 +00001149 continue;
1150 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1151 U.getLongFormMaxDisp(), U.NegOk)) {
1152 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1153 << CPEs[i].CPI << "\n");
1154 // Point the CPUser node to the replacement
1155 U.CPEMI = CPEs[i].CPEMI;
1156 // Change the CPI in the instruction operand to refer to the clone.
1157 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1158 if (UserMI->getOperand(j).isCPI()) {
1159 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1160 break;
1161 }
1162 // Adjust the refcount of the clone...
1163 CPEs[i].RefCount++;
1164 // ...and the original. If we didn't remove the old entry, none of the
1165 // addresses changed, so we don't need another pass.
1166 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1167 }
1168 }
1169 return 0;
1170}
1171
1172/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1173/// the specific unconditional branch instruction.
1174static inline unsigned getUnconditionalBrDisp(int Opc) {
1175 switch (Opc) {
Reed Kotlerf0e69682013-11-12 02:27:12 +00001176 case Mips::Bimm16:
1177 return ((1<<10)-1)*2;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001178 case Mips::BimmX16:
1179 return ((1<<16)-1)*2;
1180 default:
1181 break;
1182 }
1183 return ((1<<16)-1)*2;
1184}
1185
1186/// findAvailableWater - Look for an existing entry in the WaterList in which
1187/// we can place the CPE referenced from U so it's within range of U's MI.
1188/// Returns true if found, false if not. If it returns true, WaterIter
Reed Kotler4d0313d2013-11-05 12:04:37 +00001189/// is set to the WaterList entry.
1190/// To ensure that this pass
Reed Kotler0f007fc2013-11-05 08:14:14 +00001191/// terminates, the CPE location for a particular CPUser is only allowed to
1192/// move to a lower address, so search backward from the end of the list and
1193/// prefer the first water that is in range.
1194bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1195 water_iterator &WaterIter) {
1196 if (WaterList.empty())
1197 return false;
1198
1199 unsigned BestGrowth = ~0u;
Benjamin Kramerb6d0bd42014-03-02 12:27:27 +00001200 for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001201 --IP) {
1202 MachineBasicBlock* WaterBB = *IP;
1203 // Check if water is in range and is either at a lower address than the
1204 // current "high water mark" or a new water block that was created since
1205 // the previous iteration by inserting an unconditional branch. In the
1206 // latter case, we want to allow resetting the high water mark back to
1207 // this new water since we haven't seen it before. Inserting branches
1208 // should be relatively uncommon and when it does happen, we want to be
1209 // sure to take advantage of it for all the CPEs near that block, so that
1210 // we don't insert more branches than necessary.
1211 unsigned Growth;
1212 if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1213 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1214 NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1215 // This is the least amount of required padding seen so far.
1216 BestGrowth = Growth;
1217 WaterIter = IP;
1218 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1219 << " Growth=" << Growth << '\n');
1220
1221 // Keep looking unless it is perfect.
1222 if (BestGrowth == 0)
1223 return true;
1224 }
1225 if (IP == B)
1226 break;
1227 }
1228 return BestGrowth != ~0u;
1229}
1230
1231/// createNewWater - No existing WaterList entry will work for
1232/// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1233/// block is used if in range, and the conditional branch munged so control
1234/// flow is correct. Otherwise the block is split to create a hole with an
1235/// unconditional branch around it. In either case NewMBB is set to a
1236/// block following which the new island can be inserted (the WaterList
1237/// is not adjusted).
1238void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1239 unsigned UserOffset,
1240 MachineBasicBlock *&NewMBB) {
1241 CPUser &U = CPUsers[CPUserIndex];
1242 MachineInstr *UserMI = U.MI;
1243 MachineInstr *CPEMI = U.CPEMI;
1244 unsigned CPELogAlign = getCPELogAlign(CPEMI);
1245 MachineBasicBlock *UserMBB = UserMI->getParent();
1246 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1247
1248 // If the block does not end in an unconditional branch already, and if the
Reed Kotler4d0313d2013-11-05 12:04:37 +00001249 // end of the block is within range, make new water there.
Reed Kotler0f007fc2013-11-05 08:14:14 +00001250 if (BBHasFallthrough(UserMBB)) {
1251 // Size of branch to insert.
1252 unsigned Delta = 2;
1253 // Compute the offset where the CPE will begin.
1254 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1255
1256 if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1257 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1258 << format(", expected CPE offset %#x\n", CPEOffset));
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +00001259 NewMBB = &*++UserMBB->getIterator();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001260 // Add an unconditional branch from UserMBB to fallthrough block. Record
1261 // it for branch lengthening; this new branch will not get out of range,
1262 // but if the preceding conditional branch is out of range, the targets
1263 // will be exchanged, and the altered branch may be out of range, so the
1264 // machinery has to know about it.
Reed Kotlerf0e69682013-11-12 02:27:12 +00001265 int UncondBr = Mips::Bimm16;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001266 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1267 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1268 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1269 MaxDisp, false, UncondBr));
1270 BBInfo[UserMBB->getNumber()].Size += Delta;
1271 adjustBBOffsetsAfter(UserMBB);
1272 return;
1273 }
1274 }
1275
Reed Kotler4d0313d2013-11-05 12:04:37 +00001276 // What a big block. Find a place within the block to split it.
Reed Kotler0f007fc2013-11-05 08:14:14 +00001277
1278 // Try to split the block so it's fully aligned. Compute the latest split
1279 // point where we can add a 4-byte branch instruction, and then align to
1280 // LogAlign which is the largest possible alignment in the function.
1281 unsigned LogAlign = MF->getAlignment();
1282 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
Reed Kotler7ded5b62013-11-05 23:36:58 +00001283 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001284 DEBUG(dbgs() << format("Split in middle of big block before %#x",
1285 BaseInsertOffset));
1286
1287 // The 4 in the following is for the unconditional branch we'll be inserting
Reed Kotler4d0313d2013-11-05 12:04:37 +00001288 // Alignment of the island is handled
Reed Kotler0f007fc2013-11-05 08:14:14 +00001289 // inside isOffsetInRange.
1290 BaseInsertOffset -= 4;
1291
1292 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
Reed Kotler7ded5b62013-11-05 23:36:58 +00001293 << " la=" << LogAlign << '\n');
Reed Kotler0f007fc2013-11-05 08:14:14 +00001294
1295 // This could point off the end of the block if we've already got constant
1296 // pool entries following this block; only the last one is in the water list.
1297 // Back past any possible branches (allow for a conditional and a maximally
1298 // long unconditional).
1299 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
Reed Kotler7ded5b62013-11-05 23:36:58 +00001300 BaseInsertOffset = UserBBI.postOffset() - 8;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001301 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1302 }
Reed Kotler7ded5b62013-11-05 23:36:58 +00001303 unsigned EndInsertOffset = BaseInsertOffset + 4 +
Reed Kotler0f007fc2013-11-05 08:14:14 +00001304 CPEMI->getOperand(2).getImm();
1305 MachineBasicBlock::iterator MI = UserMI;
1306 ++MI;
1307 unsigned CPUIndex = CPUserIndex+1;
1308 unsigned NumCPUsers = CPUsers.size();
1309 //MachineInstr *LastIT = 0;
1310 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1311 Offset < BaseInsertOffset;
Benjamin Kramerb6d0bd42014-03-02 12:27:27 +00001312 Offset += TII->GetInstSizeInBytes(MI), MI = std::next(MI)) {
Reed Kotler0f007fc2013-11-05 08:14:14 +00001313 assert(MI != UserMBB->end() && "Fell off end of block");
1314 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1315 CPUser &U = CPUsers[CPUIndex];
1316 if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1317 // Shift intertion point by one unit of alignment so it is within reach.
1318 BaseInsertOffset -= 1u << LogAlign;
1319 EndInsertOffset -= 1u << LogAlign;
1320 }
1321 // This is overly conservative, as we don't account for CPEMIs being
1322 // reused within the block, but it doesn't matter much. Also assume CPEs
1323 // are added in order with alignment padding. We may eventually be able
1324 // to pack the aligned CPEs better.
1325 EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1326 CPUIndex++;
1327 }
1328 }
1329
1330 --MI;
1331 NewMBB = splitBlockBeforeInstr(MI);
1332}
1333
1334/// handleConstantPoolUser - Analyze the specified user, checking to see if it
1335/// is out-of-range. If so, pick up the constant pool value and move it some
1336/// place in-range. Return true if we changed any addresses (thus must run
1337/// another pass of branch lengthening), false otherwise.
1338bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1339 CPUser &U = CPUsers[CPUserIndex];
1340 MachineInstr *UserMI = U.MI;
1341 MachineInstr *CPEMI = U.CPEMI;
1342 unsigned CPI = CPEMI->getOperand(1).getIndex();
1343 unsigned Size = CPEMI->getOperand(2).getImm();
1344 // Compute this only once, it's expensive.
1345 unsigned UserOffset = getUserOffset(U);
1346
1347 // See if the current entry is within range, or there is a clone of it
1348 // in range.
1349 int result = findInRangeCPEntry(U, UserOffset);
1350 if (result==1) return false;
1351 else if (result==2) return true;
1352
1353
1354 // Look for water where we can place this CPE.
1355 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1356 MachineBasicBlock *NewMBB;
1357 water_iterator IP;
1358 if (findAvailableWater(U, UserOffset, IP)) {
1359 DEBUG(dbgs() << "Found water in range\n");
1360 MachineBasicBlock *WaterBB = *IP;
1361
1362 // If the original WaterList entry was "new water" on this iteration,
1363 // propagate that to the new island. This is just keeping NewWaterList
1364 // updated to match the WaterList, which will be updated below.
1365 if (NewWaterList.erase(WaterBB))
1366 NewWaterList.insert(NewIsland);
1367
1368 // The new CPE goes before the following block (NewMBB).
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +00001369 NewMBB = &*++WaterBB->getIterator();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001370 } else {
1371 // No water found.
1372 // we first see if a longer form of the instrucion could have reached
1373 // the constant. in that case we won't bother to split
Reed Kotler45c59272013-11-10 00:09:26 +00001374 if (!NoLoadRelaxation) {
1375 result = findLongFormInRangeCPEntry(U, UserOffset);
1376 if (result != 0) return true;
1377 }
Reed Kotler0f007fc2013-11-05 08:14:14 +00001378 DEBUG(dbgs() << "No water found\n");
1379 createNewWater(CPUserIndex, UserOffset, NewMBB);
1380
1381 // splitBlockBeforeInstr adds to WaterList, which is important when it is
1382 // called while handling branches so that the water will be seen on the
1383 // next iteration for constant pools, but in this context, we don't want
1384 // it. Check for this so it will be removed from the WaterList.
1385 // Also remove any entry from NewWaterList.
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +00001386 MachineBasicBlock *WaterBB = &*--NewMBB->getIterator();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001387 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1388 if (IP != WaterList.end())
1389 NewWaterList.erase(WaterBB);
1390
1391 // We are adding new water. Update NewWaterList.
1392 NewWaterList.insert(NewIsland);
1393 }
1394
1395 // Remove the original WaterList entry; we want subsequent insertions in
1396 // this vicinity to go after the one we're about to insert. This
1397 // considerably reduces the number of times we have to move the same CPE
1398 // more than once and is also important to ensure the algorithm terminates.
1399 if (IP != WaterList.end())
1400 WaterList.erase(IP);
1401
1402 // Okay, we know we can put an island before NewMBB now, do it!
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +00001403 MF->insert(NewMBB->getIterator(), NewIsland);
Reed Kotler0f007fc2013-11-05 08:14:14 +00001404
1405 // Update internal data structures to account for the newly inserted MBB.
1406 updateForInsertedWaterBlock(NewIsland);
1407
1408 // Decrement the old entry, and remove it if refcount becomes 0.
1409 decrementCPEReferenceCount(CPI, CPEMI);
1410
Reed Kotlerd3b28eb2013-11-24 02:53:09 +00001411 // No existing clone of this CPE is within range.
1412 // We will be generating a new clone. Get a UID for it.
1413 unsigned ID = createPICLabelUId();
1414
Reed Kotler0f007fc2013-11-05 08:14:14 +00001415 // Now that we have an island to add the CPE to, clone the original CPE and
1416 // add it to the island.
1417 U.HighWaterMark = NewIsland;
1418 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1419 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1420 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1421 ++NumCPEs;
1422
1423 // Mark the basic block as aligned as required by the const-pool entry.
1424 NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
1425
1426 // Increase the size of the island block to account for the new entry.
1427 BBInfo[NewIsland->getNumber()].Size += Size;
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +00001428 adjustBBOffsetsAfter(&*--NewIsland->getIterator());
Reed Kotler0f007fc2013-11-05 08:14:14 +00001429
1430 // Finally, change the CPI in the instruction operand to be ID.
1431 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1432 if (UserMI->getOperand(i).isCPI()) {
1433 UserMI->getOperand(i).setIndex(ID);
1434 break;
1435 }
1436
1437 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1438 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1439
1440 return true;
1441}
1442
1443/// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1444/// sizes and offsets of impacted basic blocks.
1445void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1446 MachineBasicBlock *CPEBB = CPEMI->getParent();
1447 unsigned Size = CPEMI->getOperand(2).getImm();
1448 CPEMI->eraseFromParent();
1449 BBInfo[CPEBB->getNumber()].Size -= Size;
1450 // All succeeding offsets have the current size value added in, fix this.
1451 if (CPEBB->empty()) {
1452 BBInfo[CPEBB->getNumber()].Size = 0;
1453
1454 // This block no longer needs to be aligned.
1455 CPEBB->setAlignment(0);
1456 } else
1457 // Entries are sorted by descending alignment, so realign from the front.
1458 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
1459
1460 adjustBBOffsetsAfter(CPEBB);
1461 // An island has only one predecessor BB and one successor BB. Check if
1462 // this BB's predecessor jumps directly to this BB's successor. This
1463 // shouldn't happen currently.
1464 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1465 // FIXME: remove the empty blocks after all the work is done?
1466}
1467
1468/// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1469/// are zero.
1470bool MipsConstantIslands::removeUnusedCPEntries() {
1471 unsigned MadeChange = false;
1472 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1473 std::vector<CPEntry> &CPEs = CPEntries[i];
1474 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1475 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1476 removeDeadCPEMI(CPEs[j].CPEMI);
Craig Topper062a2ba2014-04-25 05:30:21 +00001477 CPEs[j].CPEMI = nullptr;
Reed Kotler0f007fc2013-11-05 08:14:14 +00001478 MadeChange = true;
1479 }
1480 }
1481 }
1482 return MadeChange;
1483}
1484
1485/// isBBInRange - Returns true if the distance between specific MI and
1486/// specific BB can fit in MI's displacement field.
1487bool MipsConstantIslands::isBBInRange
1488 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1489
1490unsigned PCAdj = 4;
1491
1492 unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1493 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1494
1495 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1496 << " from BB#" << MI->getParent()->getNumber()
1497 << " max delta=" << MaxDisp
1498 << " from " << getOffsetOf(MI) << " to " << DestOffset
1499 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1500
1501 if (BrOffset <= DestOffset) {
1502 // Branch before the Dest.
1503 if (DestOffset-BrOffset <= MaxDisp)
1504 return true;
1505 } else {
1506 if (BrOffset-DestOffset <= MaxDisp)
1507 return true;
1508 }
1509 return false;
1510}
1511
1512/// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1513/// away to fit in its displacement field.
1514bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1515 MachineInstr *MI = Br.MI;
Reed Kotler0d409e22013-11-28 00:56:37 +00001516 unsigned TargetOperand = branchTargetOperand(MI);
1517 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001518
1519 // Check to see if the DestBB is already in-range.
1520 if (isBBInRange(MI, DestBB, Br.MaxDisp))
1521 return false;
1522
1523 if (!Br.isCond)
1524 return fixupUnconditionalBr(Br);
1525 return fixupConditionalBr(Br);
1526}
1527
1528/// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1529/// too far away to fit in its displacement field. If the LR register has been
1530/// spilled in the epilogue, then we can use BL to implement a far jump.
1531/// Otherwise, add an intermediate branch instruction to a branch.
1532bool
1533MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1534 MachineInstr *MI = Br.MI;
1535 MachineBasicBlock *MBB = MI->getParent();
Reed Kotler2fc05be2013-11-21 05:13:23 +00001536 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001537 // Use BL to implement far jump.
Reed Kotler2fc05be2013-11-21 05:13:23 +00001538 unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2;
1539 if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) {
1540 Br.MaxDisp = BimmX16MaxDisp;
1541 MI->setDesc(TII->get(Mips::BimmX16));
1542 }
1543 else {
1544 // need to give the math a more careful look here
1545 // this is really a segment address and not
1546 // a PC relative address. FIXME. But I think that
1547 // just reducing the bits by 1 as I've done is correct.
1548 // The basic block we are branching too much be longword aligned.
1549 // we know that RA is saved because we always save it right now.
1550 // this requirement will be relaxed later but we also have an alternate
1551 // way to implement this that I will implement that does not need jal.
1552 // We should have a way to back out this alignment restriction if we "can" later.
1553 // but it is not harmful.
1554 //
1555 DestBB->setAlignment(2);
1556 Br.MaxDisp = ((1<<24)-1) * 2;
Reed Kotlerad450f22013-11-29 22:32:56 +00001557 MI->setDesc(TII->get(Mips::JalB16));
Reed Kotler2fc05be2013-11-21 05:13:23 +00001558 }
Reed Kotler0f007fc2013-11-05 08:14:14 +00001559 BBInfo[MBB->getNumber()].Size += 2;
1560 adjustBBOffsetsAfter(MBB);
1561 HasFarJump = true;
1562 ++NumUBrFixed;
1563
1564 DEBUG(dbgs() << " Changed B to long jump " << *MI);
1565
1566 return true;
1567}
1568
Reed Kotler0d409e22013-11-28 00:56:37 +00001569
Reed Kotler0f007fc2013-11-05 08:14:14 +00001570/// fixupConditionalBr - Fix up a conditional branch whose destination is too
1571/// far away to fit in its displacement field. It is converted to an inverse
1572/// conditional branch + an unconditional branch to the destination.
1573bool
1574MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1575 MachineInstr *MI = Br.MI;
Reed Kotler0d409e22013-11-28 00:56:37 +00001576 unsigned TargetOperand = branchTargetOperand(MI);
1577 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1578 unsigned Opcode = MI->getOpcode();
1579 unsigned LongFormOpcode = longformBranchOpcode(Opcode);
1580 unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
1581
1582 // Check to see if the DestBB is already in-range.
1583 if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
1584 Br.MaxDisp = LongFormMaxOff;
1585 MI->setDesc(TII->get(LongFormOpcode));
1586 return true;
1587 }
Reed Kotler0f007fc2013-11-05 08:14:14 +00001588
1589 // Add an unconditional branch to the destination and invert the branch
1590 // condition to jump over it:
Reed Kotlerad450f22013-11-29 22:32:56 +00001591 // bteqz L1
Reed Kotler0f007fc2013-11-05 08:14:14 +00001592 // =>
Reed Kotlerad450f22013-11-29 22:32:56 +00001593 // bnez L2
Reed Kotler0f007fc2013-11-05 08:14:14 +00001594 // b L1
1595 // L2:
Reed Kotler0f007fc2013-11-05 08:14:14 +00001596
1597 // If the branch is at the end of its MBB and that has a fall-through block,
1598 // direct the updated conditional branch to the fall-through block. Otherwise,
1599 // split the MBB before the next instruction.
1600 MachineBasicBlock *MBB = MI->getParent();
1601 MachineInstr *BMI = &MBB->back();
1602 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
Reed Kotler47f3c64a2013-12-19 00:43:08 +00001603 unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode);
Reed Kotlerad450f22013-11-29 22:32:56 +00001604
Reed Kotler0f007fc2013-11-05 08:14:14 +00001605 ++NumCBrFixed;
1606 if (BMI != MI) {
Benjamin Kramerb6d0bd42014-03-02 12:27:27 +00001607 if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) &&
Daniel Sandersf9d8b8c2016-05-06 13:23:51 +00001608 BMI->isUnconditionalBranch()) {
Reed Kotler0f007fc2013-11-05 08:14:14 +00001609 // Last MI in the BB is an unconditional branch. Can we simply invert the
1610 // condition and swap destinations:
Reed Kotlerad450f22013-11-29 22:32:56 +00001611 // beqz L1
Reed Kotler0f007fc2013-11-05 08:14:14 +00001612 // b L2
1613 // =>
Reed Kotlerad450f22013-11-29 22:32:56 +00001614 // bnez L2
Reed Kotler0f007fc2013-11-05 08:14:14 +00001615 // b L1
Reed Kotlerad450f22013-11-29 22:32:56 +00001616 unsigned BMITargetOperand = branchTargetOperand(BMI);
1617 MachineBasicBlock *NewDest =
1618 BMI->getOperand(BMITargetOperand).getMBB();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001619 if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1620 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1621 << *BMI);
Reed Kotler59975c22013-12-03 23:42:51 +00001622 MI->setDesc(TII->get(OppositeBranchOpcode));
Reed Kotlerad450f22013-11-29 22:32:56 +00001623 BMI->getOperand(BMITargetOperand).setMBB(DestBB);
1624 MI->getOperand(TargetOperand).setMBB(NewDest);
Reed Kotler0f007fc2013-11-05 08:14:14 +00001625 return true;
1626 }
1627 }
1628 }
1629
Reed Kotlerad450f22013-11-29 22:32:56 +00001630
Reed Kotler0f007fc2013-11-05 08:14:14 +00001631 if (NeedSplit) {
1632 splitBlockBeforeInstr(MI);
1633 // No need for the branch to the next block. We're adding an unconditional
1634 // branch to the destination.
1635 int delta = TII->GetInstSizeInBytes(&MBB->back());
1636 BBInfo[MBB->getNumber()].Size -= delta;
1637 MBB->back().eraseFromParent();
1638 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1639 }
Duncan P. N. Exon Smith78691482015-10-20 00:15:20 +00001640 MachineBasicBlock *NextBB = &*++MBB->getIterator();
Reed Kotler0f007fc2013-11-05 08:14:14 +00001641
1642 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1643 << " also invert condition and change dest. to BB#"
1644 << NextBB->getNumber() << "\n");
1645
1646 // Insert a new conditional branch and a new unconditional branch.
1647 // Also update the ImmBranch as well as adding a new entry for the new branch.
Reed Kotler59975c22013-12-03 23:42:51 +00001648 if (MI->getNumExplicitOperands() == 2) {
1649 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1650 .addReg(MI->getOperand(0).getReg())
1651 .addMBB(NextBB);
Reed Kotler47f3c64a2013-12-19 00:43:08 +00001652 } else {
1653 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1654 .addMBB(NextBB);
Reed Kotler59975c22013-12-03 23:42:51 +00001655 }
Reed Kotler0f007fc2013-11-05 08:14:14 +00001656 Br.MI = &MBB->back();
1657 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1658 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1659 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
1660 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1661 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1662
1663 // Remove the old conditional branch. It may or may not still be in MBB.
1664 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
1665 MI->eraseFromParent();
1666 adjustBBOffsetsAfter(MBB);
1667 return true;
1668}
1669
Reed Kotler91ae9822013-10-27 21:57:36 +00001670
1671void MipsConstantIslands::prescanForConstants() {
Reed Kotler0f007fc2013-11-05 08:14:14 +00001672 unsigned J = 0;
1673 (void)J;
Reed Kotler91ae9822013-10-27 21:57:36 +00001674 for (MachineFunction::iterator B =
1675 MF->begin(), E = MF->end(); B != E; ++B) {
1676 for (MachineBasicBlock::instr_iterator I =
1677 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1678 switch(I->getDesc().getOpcode()) {
1679 case Mips::LwConstant32: {
Reed Kotlera787aa22013-11-24 06:18:50 +00001680 PrescannedForConstants = true;
Reed Kotler91ae9822013-10-27 21:57:36 +00001681 DEBUG(dbgs() << "constant island constant " << *I << "\n");
1682 J = I->getNumOperands();
1683 DEBUG(dbgs() << "num operands " << J << "\n");
1684 MachineOperand& Literal = I->getOperand(1);
1685 if (Literal.isImm()) {
1686 int64_t V = Literal.getImm();
1687 DEBUG(dbgs() << "literal " << V << "\n");
1688 Type *Int32Ty =
1689 Type::getInt32Ty(MF->getFunction()->getContext());
1690 const Constant *C = ConstantInt::get(Int32Ty, V);
1691 unsigned index = MCP->getConstantPoolIndex(C, 4);
1692 I->getOperand(2).ChangeToImmediate(index);
1693 DEBUG(dbgs() << "constant island constant " << *I << "\n");
Reed Kotler0f007fc2013-11-05 08:14:14 +00001694 I->setDesc(TII->get(Mips::LwRxPcTcp16));
Reed Kotler91ae9822013-10-27 21:57:36 +00001695 I->RemoveOperand(1);
1696 I->RemoveOperand(1);
1697 I->addOperand(MachineOperand::CreateCPI(index, 0));
Reed Kotler0f007fc2013-11-05 08:14:14 +00001698 I->addOperand(MachineOperand::CreateImm(4));
Reed Kotler91ae9822013-10-27 21:57:36 +00001699 }
1700 break;
1701 }
1702 default:
1703 break;
1704 }
1705 }
1706 }
1707}