1 //===-- Thumb2SizeReduction.cpp - Thumb2 code size reduction pass -*- C++ -*-=//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #define DEBUG_TYPE "t2-reduce-size"
11 #include "ARM.h"
12 #include "ARMBaseRegisterInfo.h"
13 #include "ARMBaseInstrInfo.h"
14 #include "ARMSubtarget.h"
15 #include "Thumb2InstrInfo.h"
16 #include "MCTargetDesc/ARMAddressingModes.h"
17 #include "llvm/CodeGen/MachineInstr.h"
18 #include "llvm/CodeGen/MachineInstrBuilder.h"
19 #include "llvm/CodeGen/MachineFunctionPass.h"
20 #include "llvm/Support/CommandLine.h"
21 #include "llvm/Support/Debug.h"
22 #include "llvm/Support/raw_ostream.h"
23 #include "llvm/ADT/DenseMap.h"
24 #include "llvm/ADT/Statistic.h"
25 using namespace llvm;
26
27 STATISTIC(NumNarrows, "Number of 32-bit instrs reduced to 16-bit ones");
28 STATISTIC(Num2Addrs, "Number of 32-bit instrs reduced to 2addr 16-bit ones");
29 STATISTIC(NumLdSts, "Number of 32-bit load / store reduced to 16-bit ones");
30
31 static cl::opt<int> ReduceLimit("t2-reduce-limit",
32 cl::init(-1), cl::Hidden);
33 static cl::opt<int> ReduceLimit2Addr("t2-reduce-limit2",
34 cl::init(-1), cl::Hidden);
35 static cl::opt<int> ReduceLimitLdSt("t2-reduce-limit3",
36 cl::init(-1), cl::Hidden);
37
38 namespace {
39 /// ReduceTable - A static table with information on mapping from wide
40 /// opcodes to narrow
41 struct ReduceEntry {
42 unsigned WideOpc; // Wide opcode
43 unsigned NarrowOpc1; // Narrow opcode to transform to
44 unsigned NarrowOpc2; // Narrow opcode when it's two-address
45 uint8_t Imm1Limit; // Limit of immediate field (bits)
46 uint8_t Imm2Limit; // Limit of immediate field when it's two-address
47 unsigned LowRegs1 : 1; // Only possible if low-registers are used
48 unsigned LowRegs2 : 1; // Only possible if low-registers are used (2addr)
49 unsigned PredCC1 : 2; // 0 - If predicated, cc is on and vice versa.
50 // 1 - No cc field.
51 // 2 - Always set CPSR.
52 unsigned PredCC2 : 2;
53 unsigned PartFlag : 1; // 16-bit instruction does partial flag update
54 unsigned Special : 1; // Needs to be dealt with specially
55 };
56
57 static const ReduceEntry ReduceTable[] = {
58 // Wide, Narrow1, Narrow2, imm1,imm2, lo1, lo2, P/C, PF, S
59 { ARM::t2ADCrr, 0, ARM::tADC, 0, 0, 0, 1, 0,0, 0,0 },
60 { ARM::t2ADDri, ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 0,0, 0,1 },
61 { ARM::t2ADDrr, ARM::tADDrr, ARM::tADDhirr, 0, 0, 1, 0, 0,1, 0,0 },
62 { ARM::t2ADDSri,ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 2,2, 0,1 },
63 { ARM::t2ADDSrr,ARM::tADDrr, 0, 0, 0, 1, 0, 2,0, 0,1 },
64 { ARM::t2ANDrr, 0, ARM::tAND, 0, 0, 0, 1, 0,0, 1,0 },
65 { ARM::t2ASRri, ARM::tASRri, 0, 5, 0, 1, 0, 0,0, 1,0 },
66 { ARM::t2ASRrr, 0, ARM::tASRrr, 0, 0, 0, 1, 0,0, 1,0 },
67 { ARM::t2BICrr, 0, ARM::tBIC, 0, 0, 0, 1, 0,0, 1,0 },
68 //FIXME: Disable CMN, as CCodes are backwards from compare expectations
69 //{ ARM::t2CMNrr, ARM::tCMN, 0, 0, 0, 1, 0, 2,0, 0,0 },
70 { ARM::t2CMPri, ARM::tCMPi8, 0, 8, 0, 1, 0, 2,0, 0,0 },
71 { ARM::t2CMPrr, ARM::tCMPhir, 0, 0, 0, 0, 0, 2,0, 0,1 },
72 { ARM::t2EORrr, 0, ARM::tEOR, 0, 0, 0, 1, 0,0, 1,0 },
73 // FIXME: adr.n immediate offset must be multiple of 4.
74 //{ ARM::t2LEApcrelJT,ARM::tLEApcrelJT, 0, 0, 0, 1, 0, 1,0, 0,0 },
75 { ARM::t2LSLri, ARM::tLSLri, 0, 5, 0, 1, 0, 0,0, 1,0 },
76 { ARM::t2LSLrr, 0, ARM::tLSLrr, 0, 0, 0, 1, 0,0, 1,0 },
77 { ARM::t2LSRri, ARM::tLSRri, 0, 5, 0, 1, 0, 0,0, 1,0 },
78 { ARM::t2LSRrr, 0, ARM::tLSRrr, 0, 0, 0, 1, 0,0, 1,0 },
79 // FIXME: tMOVi8 and tMVN also partially update CPSR but they are less
80 // likely to cause issue in the loop. As a size / performance workaround,
81 // they are not marked as such.
82 { ARM::t2MOVi, ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 0,0 },
83 { ARM::t2MOVi16,ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 0,1 },
84 // FIXME: Do we need the 16-bit 'S' variant?
85 { ARM::t2MOVr,ARM::tMOVr, 0, 0, 0, 0, 0, 1,0, 0,0 },
86 { ARM::t2MUL, 0, ARM::tMUL, 0, 0, 0, 1, 0,0, 1,0 },
87 { ARM::t2MVNr, ARM::tMVN, 0, 0, 0, 1, 0, 0,0, 0,0 },
88 { ARM::t2ORRrr, 0, ARM::tORR, 0, 0, 0, 1, 0,0, 1,0 },
89 { ARM::t2REV, ARM::tREV, 0, 0, 0, 1, 0, 1,0, 0,0 },
90 { ARM::t2REV16, ARM::tREV16, 0, 0, 0, 1, 0, 1,0, 0,0 },
91 { ARM::t2REVSH, ARM::tREVSH, 0, 0, 0, 1, 0, 1,0, 0,0 },
92 { ARM::t2RORrr, 0, ARM::tROR, 0, 0, 0, 1, 0,0, 1,0 },
93 { ARM::t2RSBri, ARM::tRSB, 0, 0, 0, 1, 0, 0,0, 0,1 },
94 { ARM::t2RSBSri,ARM::tRSB, 0, 0, 0, 1, 0, 2,0, 0,1 },
95 { ARM::t2SBCrr, 0, ARM::tSBC, 0, 0, 0, 1, 0,0, 0,0 },
96 { ARM::t2SUBri, ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 0,0, 0,0 },
97 { ARM::t2SUBrr, ARM::tSUBrr, 0, 0, 0, 1, 0, 0,0, 0,0 },
98 { ARM::t2SUBSri,ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 2,2, 0,0 },
99 { ARM::t2SUBSrr,ARM::tSUBrr, 0, 0, 0, 1, 0, 2,0, 0,0 },
100 { ARM::t2SXTB, ARM::tSXTB, 0, 0, 0, 1, 0, 1,0, 0,1 },
101 { ARM::t2SXTH, ARM::tSXTH, 0, 0, 0, 1, 0, 1,0, 0,1 },
102 { ARM::t2TSTrr, ARM::tTST, 0, 0, 0, 1, 0, 2,0, 0,0 },
103 { ARM::t2UXTB, ARM::tUXTB, 0, 0, 0, 1, 0, 1,0, 0,1 },
104 { ARM::t2UXTH, ARM::tUXTH, 0, 0, 0, 1, 0, 1,0, 0,1 },
105
106 // FIXME: Clean this up after splitting each Thumb load / store opcode
107 // into multiple ones.
108 { ARM::t2LDRi12,ARM::tLDRi, ARM::tLDRspi, 5, 8, 1, 0, 0,0, 0,1 },
109 { ARM::t2LDRs, ARM::tLDRr, 0, 0, 0, 1, 0, 0,0, 0,1 },
110 { ARM::t2LDRBi12,ARM::tLDRBi, 0, 5, 0, 1, 0, 0,0, 0,1 },
111 { ARM::t2LDRBs, ARM::tLDRBr, 0, 0, 0, 1, 0, 0,0, 0,1 },
112 { ARM::t2LDRHi12,ARM::tLDRHi, 0, 5, 0, 1, 0, 0,0, 0,1 },
113 { ARM::t2LDRHs, ARM::tLDRHr, 0, 0, 0, 1, 0, 0,0, 0,1 },
114 { ARM::t2LDRSBs,ARM::tLDRSB, 0, 0, 0, 1, 0, 0,0, 0,1 },
115 { ARM::t2LDRSHs,ARM::tLDRSH, 0, 0, 0, 1, 0, 0,0, 0,1 },
116 { ARM::t2STRi12,ARM::tSTRi, ARM::tSTRspi, 5, 8, 1, 0, 0,0, 0,1 },
117 { ARM::t2STRs, ARM::tSTRr, 0, 0, 0, 1, 0, 0,0, 0,1 },
118 { ARM::t2STRBi12,ARM::tSTRBi, 0, 5, 0, 1, 0, 0,0, 0,1 },
119 { ARM::t2STRBs, ARM::tSTRBr, 0, 0, 0, 1, 0, 0,0, 0,1 },
120 { ARM::t2STRHi12,ARM::tSTRHi, 0, 5, 0, 1, 0, 0,0, 0,1 },
121 { ARM::t2STRHs, ARM::tSTRHr, 0, 0, 0, 1, 0, 0,0, 0,1 },
122
123 { ARM::t2LDMIA, ARM::tLDMIA, 0, 0, 0, 1, 1, 1,1, 0,1 },
124 { ARM::t2LDMIA_RET,0, ARM::tPOP_RET, 0, 0, 1, 1, 1,1, 0,1 },
125 { ARM::t2LDMIA_UPD,ARM::tLDMIA_UPD,ARM::tPOP,0, 0, 1, 1, 1,1, 0,1 },
126 // ARM::t2STM (with no basereg writeback) has no Thumb1 equivalent
127 { ARM::t2STMIA_UPD,ARM::tSTMIA_UPD, 0, 0, 0, 1, 1, 1,1, 0,1 },
128 { ARM::t2STMDB_UPD, 0, ARM::tPUSH, 0, 0, 1, 1, 1,1, 0,1 },
129 };
130
131 class Thumb2SizeReduce : public MachineFunctionPass {
132 public:
133 static char ID;
134 Thumb2SizeReduce();
135
136 const Thumb2InstrInfo *TII;
137 const ARMSubtarget *STI;
138
139 virtual bool runOnMachineFunction(MachineFunction &MF);
140
getPassName() const141 virtual const char *getPassName() const {
142 return "Thumb2 instruction size reduction pass";
143 }
144
145 private:
146 /// ReduceOpcodeMap - Maps wide opcode to index of entry in ReduceTable.
147 DenseMap<unsigned, unsigned> ReduceOpcodeMap;
148
149 bool canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use);
150
151 bool VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
152 bool is2Addr, ARMCC::CondCodes Pred,
153 bool LiveCPSR, bool &HasCC, bool &CCDead);
154
155 bool ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
156 const ReduceEntry &Entry);
157
158 bool ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
159 const ReduceEntry &Entry, bool LiveCPSR,
160 MachineInstr *CPSRDef);
161
162 /// ReduceTo2Addr - Reduce a 32-bit instruction to a 16-bit two-address
163 /// instruction.
164 bool ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
165 const ReduceEntry &Entry,
166 bool LiveCPSR, MachineInstr *CPSRDef);
167
168 /// ReduceToNarrow - Reduce a 32-bit instruction to a 16-bit
169 /// non-two-address instruction.
170 bool ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
171 const ReduceEntry &Entry,
172 bool LiveCPSR, MachineInstr *CPSRDef);
173
174 /// ReduceMBB - Reduce width of instructions in the specified basic block.
175 bool ReduceMBB(MachineBasicBlock &MBB);
176 };
177 char Thumb2SizeReduce::ID = 0;
178 }
179
Thumb2SizeReduce()180 Thumb2SizeReduce::Thumb2SizeReduce() : MachineFunctionPass(ID) {
181 for (unsigned i = 0, e = array_lengthof(ReduceTable); i != e; ++i) {
182 unsigned FromOpc = ReduceTable[i].WideOpc;
183 if (!ReduceOpcodeMap.insert(std::make_pair(FromOpc, i)).second)
184 assert(false && "Duplicated entries?");
185 }
186 }
187
HasImplicitCPSRDef(const MCInstrDesc & MCID)188 static bool HasImplicitCPSRDef(const MCInstrDesc &MCID) {
189 for (const unsigned *Regs = MCID.ImplicitDefs; *Regs; ++Regs)
190 if (*Regs == ARM::CPSR)
191 return true;
192 return false;
193 }
194
195 /// canAddPseudoFlagDep - For A9 (and other out-of-order) implementations,
196 /// the 's' 16-bit instruction partially update CPSR. Abort the
197 /// transformation to avoid adding false dependency on last CPSR setting
198 /// instruction which hurts the ability for out-of-order execution engine
199 /// to do register renaming magic.
200 /// This function checks if there is a read-of-write dependency between the
201 /// last instruction that defines the CPSR and the current instruction. If there
202 /// is, then there is no harm done since the instruction cannot be retired
203 /// before the CPSR setting instruction anyway.
204 /// Note, we are not doing full dependency analysis here for the sake of compile
205 /// time. We're not looking for cases like:
206 /// r0 = muls ...
207 /// r1 = add.w r0, ...
208 /// ...
209 /// = mul.w r1
210 /// In this case it would have been ok to narrow the mul.w to muls since there
211 /// are indirect RAW dependency between the muls and the mul.w
212 bool
canAddPseudoFlagDep(MachineInstr * Def,MachineInstr * Use)213 Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use) {
214 if (!Def || !STI->avoidCPSRPartialUpdate())
215 return false;
216
217 SmallSet<unsigned, 2> Defs;
218 for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) {
219 const MachineOperand &MO = Def->getOperand(i);
220 if (!MO.isReg() || MO.isUndef() || MO.isUse())
221 continue;
222 unsigned Reg = MO.getReg();
223 if (Reg == 0 || Reg == ARM::CPSR)
224 continue;
225 Defs.insert(Reg);
226 }
227
228 for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
229 const MachineOperand &MO = Use->getOperand(i);
230 if (!MO.isReg() || MO.isUndef() || MO.isDef())
231 continue;
232 unsigned Reg = MO.getReg();
233 if (Defs.count(Reg))
234 return false;
235 }
236
237 // No read-after-write dependency. The narrowing will add false dependency.
238 return true;
239 }
240
241 bool
VerifyPredAndCC(MachineInstr * MI,const ReduceEntry & Entry,bool is2Addr,ARMCC::CondCodes Pred,bool LiveCPSR,bool & HasCC,bool & CCDead)242 Thumb2SizeReduce::VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
243 bool is2Addr, ARMCC::CondCodes Pred,
244 bool LiveCPSR, bool &HasCC, bool &CCDead) {
245 if ((is2Addr && Entry.PredCC2 == 0) ||
246 (!is2Addr && Entry.PredCC1 == 0)) {
247 if (Pred == ARMCC::AL) {
248 // Not predicated, must set CPSR.
249 if (!HasCC) {
250 // Original instruction was not setting CPSR, but CPSR is not
251 // currently live anyway. It's ok to set it. The CPSR def is
252 // dead though.
253 if (!LiveCPSR) {
254 HasCC = true;
255 CCDead = true;
256 return true;
257 }
258 return false;
259 }
260 } else {
261 // Predicated, must not set CPSR.
262 if (HasCC)
263 return false;
264 }
265 } else if ((is2Addr && Entry.PredCC2 == 2) ||
266 (!is2Addr && Entry.PredCC1 == 2)) {
267 /// Old opcode has an optional def of CPSR.
268 if (HasCC)
269 return true;
270 // If old opcode does not implicitly define CPSR, then it's not ok since
271 // these new opcodes' CPSR def is not meant to be thrown away. e.g. CMP.
272 if (!HasImplicitCPSRDef(MI->getDesc()))
273 return false;
274 HasCC = true;
275 } else {
276 // 16-bit instruction does not set CPSR.
277 if (HasCC)
278 return false;
279 }
280
281 return true;
282 }
283
VerifyLowRegs(MachineInstr * MI)284 static bool VerifyLowRegs(MachineInstr *MI) {
285 unsigned Opc = MI->getOpcode();
286 bool isPCOk = (Opc == ARM::t2LDMIA_RET || Opc == ARM::t2LDMIA ||
287 Opc == ARM::t2LDMDB || Opc == ARM::t2LDMIA_UPD ||
288 Opc == ARM::t2LDMDB_UPD);
289 bool isLROk = (Opc == ARM::t2STMIA_UPD || Opc == ARM::t2STMDB_UPD);
290 bool isSPOk = isPCOk || isLROk;
291 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
292 const MachineOperand &MO = MI->getOperand(i);
293 if (!MO.isReg() || MO.isImplicit())
294 continue;
295 unsigned Reg = MO.getReg();
296 if (Reg == 0 || Reg == ARM::CPSR)
297 continue;
298 if (isPCOk && Reg == ARM::PC)
299 continue;
300 if (isLROk && Reg == ARM::LR)
301 continue;
302 if (Reg == ARM::SP) {
303 if (isSPOk)
304 continue;
305 if (i == 1 && (Opc == ARM::t2LDRi12 || Opc == ARM::t2STRi12))
306 // Special case for these ldr / str with sp as base register.
307 continue;
308 }
309 if (!isARMLowRegister(Reg))
310 return false;
311 }
312 return true;
313 }
314
315 bool
ReduceLoadStore(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry)316 Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
317 const ReduceEntry &Entry) {
318 if (ReduceLimitLdSt != -1 && ((int)NumLdSts >= ReduceLimitLdSt))
319 return false;
320
321 unsigned Scale = 1;
322 bool HasImmOffset = false;
323 bool HasShift = false;
324 bool HasOffReg = true;
325 bool isLdStMul = false;
326 unsigned Opc = Entry.NarrowOpc1;
327 unsigned OpNum = 3; // First 'rest' of operands.
328 uint8_t ImmLimit = Entry.Imm1Limit;
329
330 switch (Entry.WideOpc) {
331 default:
332 llvm_unreachable("Unexpected Thumb2 load / store opcode!");
333 case ARM::t2LDRi12:
334 case ARM::t2STRi12:
335 if (MI->getOperand(1).getReg() == ARM::SP) {
336 Opc = Entry.NarrowOpc2;
337 ImmLimit = Entry.Imm2Limit;
338 HasOffReg = false;
339 }
340
341 Scale = 4;
342 HasImmOffset = true;
343 HasOffReg = false;
344 break;
345 case ARM::t2LDRBi12:
346 case ARM::t2STRBi12:
347 HasImmOffset = true;
348 HasOffReg = false;
349 break;
350 case ARM::t2LDRHi12:
351 case ARM::t2STRHi12:
352 Scale = 2;
353 HasImmOffset = true;
354 HasOffReg = false;
355 break;
356 case ARM::t2LDRs:
357 case ARM::t2LDRBs:
358 case ARM::t2LDRHs:
359 case ARM::t2LDRSBs:
360 case ARM::t2LDRSHs:
361 case ARM::t2STRs:
362 case ARM::t2STRBs:
363 case ARM::t2STRHs:
364 HasShift = true;
365 OpNum = 4;
366 break;
367 case ARM::t2LDMIA:
368 case ARM::t2LDMDB: {
369 unsigned BaseReg = MI->getOperand(0).getReg();
370 if (!isARMLowRegister(BaseReg) || Entry.WideOpc != ARM::t2LDMIA)
371 return false;
372
373 // For the non-writeback version (this one), the base register must be
374 // one of the registers being loaded.
375 bool isOK = false;
376 for (unsigned i = 4; i < MI->getNumOperands(); ++i) {
377 if (MI->getOperand(i).getReg() == BaseReg) {
378 isOK = true;
379 break;
380 }
381 }
382
383 if (!isOK)
384 return false;
385
386 OpNum = 0;
387 isLdStMul = true;
388 break;
389 }
390 case ARM::t2LDMIA_RET: {
391 unsigned BaseReg = MI->getOperand(1).getReg();
392 if (BaseReg != ARM::SP)
393 return false;
394 Opc = Entry.NarrowOpc2; // tPOP_RET
395 OpNum = 2;
396 isLdStMul = true;
397 break;
398 }
399 case ARM::t2LDMIA_UPD:
400 case ARM::t2LDMDB_UPD:
401 case ARM::t2STMIA_UPD:
402 case ARM::t2STMDB_UPD: {
403 OpNum = 0;
404
405 unsigned BaseReg = MI->getOperand(1).getReg();
406 if (BaseReg == ARM::SP &&
407 (Entry.WideOpc == ARM::t2LDMIA_UPD ||
408 Entry.WideOpc == ARM::t2STMDB_UPD)) {
409 Opc = Entry.NarrowOpc2; // tPOP or tPUSH
410 OpNum = 2;
411 } else if (!isARMLowRegister(BaseReg) ||
412 (Entry.WideOpc != ARM::t2LDMIA_UPD &&
413 Entry.WideOpc != ARM::t2STMIA_UPD)) {
414 return false;
415 }
416
417 isLdStMul = true;
418 break;
419 }
420 }
421
422 unsigned OffsetReg = 0;
423 bool OffsetKill = false;
424 if (HasShift) {
425 OffsetReg = MI->getOperand(2).getReg();
426 OffsetKill = MI->getOperand(2).isKill();
427
428 if (MI->getOperand(3).getImm())
429 // Thumb1 addressing mode doesn't support shift.
430 return false;
431 }
432
433 unsigned OffsetImm = 0;
434 if (HasImmOffset) {
435 OffsetImm = MI->getOperand(2).getImm();
436 unsigned MaxOffset = ((1 << ImmLimit) - 1) * Scale;
437
438 if ((OffsetImm & (Scale - 1)) || OffsetImm > MaxOffset)
439 // Make sure the immediate field fits.
440 return false;
441 }
442
443 // Add the 16-bit load / store instruction.
444 DebugLoc dl = MI->getDebugLoc();
445 MachineInstrBuilder MIB = BuildMI(MBB, *MI, dl, TII->get(Opc));
446 if (!isLdStMul) {
447 MIB.addOperand(MI->getOperand(0));
448 MIB.addOperand(MI->getOperand(1));
449
450 if (HasImmOffset)
451 MIB.addImm(OffsetImm / Scale);
452
453 assert((!HasShift || OffsetReg) && "Invalid so_reg load / store address!");
454
455 if (HasOffReg)
456 MIB.addReg(OffsetReg, getKillRegState(OffsetKill));
457 }
458
459 // Transfer the rest of operands.
460 for (unsigned e = MI->getNumOperands(); OpNum != e; ++OpNum)
461 MIB.addOperand(MI->getOperand(OpNum));
462
463 // Transfer memoperands.
464 MIB->setMemRefs(MI->memoperands_begin(), MI->memoperands_end());
465
466 // Transfer MI flags.
467 MIB.setMIFlags(MI->getFlags());
468
469 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB);
470
471 MBB.erase(MI);
472 ++NumLdSts;
473 return true;
474 }
475
476 bool
ReduceSpecial(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry,bool LiveCPSR,MachineInstr * CPSRDef)477 Thumb2SizeReduce::ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
478 const ReduceEntry &Entry,
479 bool LiveCPSR, MachineInstr *CPSRDef) {
480 unsigned Opc = MI->getOpcode();
481 if (Opc == ARM::t2ADDri) {
482 // If the source register is SP, try to reduce to tADDrSPi, otherwise
483 // it's a normal reduce.
484 if (MI->getOperand(1).getReg() != ARM::SP) {
485 if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef))
486 return true;
487 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef);
488 }
489 // Try to reduce to tADDrSPi.
490 unsigned Imm = MI->getOperand(2).getImm();
491 // The immediate must be in range, the destination register must be a low
492 // reg, the predicate must be "always" and the condition flags must not
493 // be being set.
494 if (Imm & 3 || Imm > 1020)
495 return false;
496 if (!isARMLowRegister(MI->getOperand(0).getReg()))
497 return false;
498 if (MI->getOperand(3).getImm() != ARMCC::AL)
499 return false;
500 const MCInstrDesc &MCID = MI->getDesc();
501 if (MCID.hasOptionalDef() &&
502 MI->getOperand(MCID.getNumOperands()-1).getReg() == ARM::CPSR)
503 return false;
504
505 MachineInstrBuilder MIB = BuildMI(MBB, *MI, MI->getDebugLoc(),
506 TII->get(ARM::tADDrSPi))
507 .addOperand(MI->getOperand(0))
508 .addOperand(MI->getOperand(1))
509 .addImm(Imm / 4); // The tADDrSPi has an implied scale by four.
510 AddDefaultPred(MIB);
511
512 // Transfer MI flags.
513 MIB.setMIFlags(MI->getFlags());
514
515 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " <<*MIB);
516
517 MBB.erase(MI);
518 ++NumNarrows;
519 return true;
520 }
521
522 if (Entry.LowRegs1 && !VerifyLowRegs(MI))
523 return false;
524
525 const MCInstrDesc &MCID = MI->getDesc();
526 if (MCID.mayLoad() || MCID.mayStore())
527 return ReduceLoadStore(MBB, MI, Entry);
528
529 switch (Opc) {
530 default: break;
531 case ARM::t2ADDSri:
532 case ARM::t2ADDSrr: {
533 unsigned PredReg = 0;
534 if (getInstrPredicate(MI, PredReg) == ARMCC::AL) {
535 switch (Opc) {
536 default: break;
537 case ARM::t2ADDSri: {
538 if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef))
539 return true;
540 // fallthrough
541 }
542 case ARM::t2ADDSrr:
543 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef);
544 }
545 }
546 break;
547 }
548 case ARM::t2RSBri:
549 case ARM::t2RSBSri:
550 case ARM::t2SXTB:
551 case ARM::t2SXTH:
552 case ARM::t2UXTB:
553 case ARM::t2UXTH:
554 if (MI->getOperand(2).getImm() == 0)
555 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef);
556 break;
557 case ARM::t2MOVi16:
558 // Can convert only 'pure' immediate operands, not immediates obtained as
559 // globals' addresses.
560 if (MI->getOperand(1).isImm())
561 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef);
562 break;
563 case ARM::t2CMPrr: {
564 // Try to reduce to the lo-reg only version first. Why there are two
565 // versions of the instruction is a mystery.
566 // It would be nice to just have two entries in the master table that
567 // are prioritized, but the table assumes a unique entry for each
568 // source insn opcode. So for now, we hack a local entry record to use.
569 static const ReduceEntry NarrowEntry =
570 { ARM::t2CMPrr,ARM::tCMPr, 0, 0, 0, 1, 1,2, 0, 0,1 };
571 if (ReduceToNarrow(MBB, MI, NarrowEntry, LiveCPSR, CPSRDef))
572 return true;
573 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef);
574 }
575 }
576 return false;
577 }
578
579 bool
ReduceTo2Addr(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry,bool LiveCPSR,MachineInstr * CPSRDef)580 Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
581 const ReduceEntry &Entry,
582 bool LiveCPSR, MachineInstr *CPSRDef) {
583
584 if (ReduceLimit2Addr != -1 && ((int)Num2Addrs >= ReduceLimit2Addr))
585 return false;
586
587 unsigned Reg0 = MI->getOperand(0).getReg();
588 unsigned Reg1 = MI->getOperand(1).getReg();
589 if (Reg0 != Reg1) {
590 // Try to commute the operands to make it a 2-address instruction.
591 unsigned CommOpIdx1, CommOpIdx2;
592 if (!TII->findCommutedOpIndices(MI, CommOpIdx1, CommOpIdx2) ||
593 CommOpIdx1 != 1 || MI->getOperand(CommOpIdx2).getReg() != Reg0)
594 return false;
595 MachineInstr *CommutedMI = TII->commuteInstruction(MI);
596 if (!CommutedMI)
597 return false;
598 }
599 if (Entry.LowRegs2 && !isARMLowRegister(Reg0))
600 return false;
601 if (Entry.Imm2Limit) {
602 unsigned Imm = MI->getOperand(2).getImm();
603 unsigned Limit = (1 << Entry.Imm2Limit) - 1;
604 if (Imm > Limit)
605 return false;
606 } else {
607 unsigned Reg2 = MI->getOperand(2).getReg();
608 if (Entry.LowRegs2 && !isARMLowRegister(Reg2))
609 return false;
610 }
611
612 // Check if it's possible / necessary to transfer the predicate.
613 const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc2);
614 unsigned PredReg = 0;
615 ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
616 bool SkipPred = false;
617 if (Pred != ARMCC::AL) {
618 if (!NewMCID.isPredicable())
619 // Can't transfer predicate, fail.
620 return false;
621 } else {
622 SkipPred = !NewMCID.isPredicable();
623 }
624
625 bool HasCC = false;
626 bool CCDead = false;
627 const MCInstrDesc &MCID = MI->getDesc();
628 if (MCID.hasOptionalDef()) {
629 unsigned NumOps = MCID.getNumOperands();
630 HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR);
631 if (HasCC && MI->getOperand(NumOps-1).isDead())
632 CCDead = true;
633 }
634 if (!VerifyPredAndCC(MI, Entry, true, Pred, LiveCPSR, HasCC, CCDead))
635 return false;
636
637 // Avoid adding a false dependency on partial flag update by some 16-bit
638 // instructions which has the 's' bit set.
639 if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
640 canAddPseudoFlagDep(CPSRDef, MI))
641 return false;
642
643 // Add the 16-bit instruction.
644 DebugLoc dl = MI->getDebugLoc();
645 MachineInstrBuilder MIB = BuildMI(MBB, *MI, dl, NewMCID);
646 MIB.addOperand(MI->getOperand(0));
647 if (NewMCID.hasOptionalDef()) {
648 if (HasCC)
649 AddDefaultT1CC(MIB, CCDead);
650 else
651 AddNoT1CC(MIB);
652 }
653
654 // Transfer the rest of operands.
655 unsigned NumOps = MCID.getNumOperands();
656 for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) {
657 if (i < NumOps && MCID.OpInfo[i].isOptionalDef())
658 continue;
659 if (SkipPred && MCID.OpInfo[i].isPredicate())
660 continue;
661 MIB.addOperand(MI->getOperand(i));
662 }
663
664 // Transfer MI flags.
665 MIB.setMIFlags(MI->getFlags());
666
667 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB);
668
669 MBB.erase(MI);
670 ++Num2Addrs;
671 return true;
672 }
673
674 bool
ReduceToNarrow(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry,bool LiveCPSR,MachineInstr * CPSRDef)675 Thumb2SizeReduce::ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
676 const ReduceEntry &Entry,
677 bool LiveCPSR, MachineInstr *CPSRDef) {
678 if (ReduceLimit != -1 && ((int)NumNarrows >= ReduceLimit))
679 return false;
680
681 unsigned Limit = ~0U;
682 if (Entry.Imm1Limit)
683 Limit = (1 << Entry.Imm1Limit) - 1;
684
685 const MCInstrDesc &MCID = MI->getDesc();
686 for (unsigned i = 0, e = MCID.getNumOperands(); i != e; ++i) {
687 if (MCID.OpInfo[i].isPredicate())
688 continue;
689 const MachineOperand &MO = MI->getOperand(i);
690 if (MO.isReg()) {
691 unsigned Reg = MO.getReg();
692 if (!Reg || Reg == ARM::CPSR)
693 continue;
694 if (Entry.LowRegs1 && !isARMLowRegister(Reg))
695 return false;
696 } else if (MO.isImm() &&
697 !MCID.OpInfo[i].isPredicate()) {
698 if (((unsigned)MO.getImm()) > Limit)
699 return false;
700 }
701 }
702
703 // Check if it's possible / necessary to transfer the predicate.
704 const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc1);
705 unsigned PredReg = 0;
706 ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
707 bool SkipPred = false;
708 if (Pred != ARMCC::AL) {
709 if (!NewMCID.isPredicable())
710 // Can't transfer predicate, fail.
711 return false;
712 } else {
713 SkipPred = !NewMCID.isPredicable();
714 }
715
716 bool HasCC = false;
717 bool CCDead = false;
718 if (MCID.hasOptionalDef()) {
719 unsigned NumOps = MCID.getNumOperands();
720 HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR);
721 if (HasCC && MI->getOperand(NumOps-1).isDead())
722 CCDead = true;
723 }
724 if (!VerifyPredAndCC(MI, Entry, false, Pred, LiveCPSR, HasCC, CCDead))
725 return false;
726
727 // Avoid adding a false dependency on partial flag update by some 16-bit
728 // instructions which has the 's' bit set.
729 if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
730 canAddPseudoFlagDep(CPSRDef, MI))
731 return false;
732
733 // Add the 16-bit instruction.
734 DebugLoc dl = MI->getDebugLoc();
735 MachineInstrBuilder MIB = BuildMI(MBB, *MI, dl, NewMCID);
736 MIB.addOperand(MI->getOperand(0));
737 if (NewMCID.hasOptionalDef()) {
738 if (HasCC)
739 AddDefaultT1CC(MIB, CCDead);
740 else
741 AddNoT1CC(MIB);
742 }
743
744 // Transfer the rest of operands.
745 unsigned NumOps = MCID.getNumOperands();
746 for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) {
747 if (i < NumOps && MCID.OpInfo[i].isOptionalDef())
748 continue;
749 if ((MCID.getOpcode() == ARM::t2RSBSri ||
750 MCID.getOpcode() == ARM::t2RSBri ||
751 MCID.getOpcode() == ARM::t2SXTB ||
752 MCID.getOpcode() == ARM::t2SXTH ||
753 MCID.getOpcode() == ARM::t2UXTB ||
754 MCID.getOpcode() == ARM::t2UXTH) && i == 2)
755 // Skip the zero immediate operand, it's now implicit.
756 continue;
757 bool isPred = (i < NumOps && MCID.OpInfo[i].isPredicate());
758 if (SkipPred && isPred)
759 continue;
760 const MachineOperand &MO = MI->getOperand(i);
761 if (MO.isReg() && MO.isImplicit() && MO.getReg() == ARM::CPSR)
762 // Skip implicit def of CPSR. Either it's modeled as an optional
763 // def now or it's already an implicit def on the new instruction.
764 continue;
765 MIB.addOperand(MO);
766 }
767 if (!MCID.isPredicable() && NewMCID.isPredicable())
768 AddDefaultPred(MIB);
769
770 // Transfer MI flags.
771 MIB.setMIFlags(MI->getFlags());
772
773 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB);
774
775 MBB.erase(MI);
776 ++NumNarrows;
777 return true;
778 }
779
UpdateCPSRDef(MachineInstr & MI,bool LiveCPSR,bool & DefCPSR)780 static bool UpdateCPSRDef(MachineInstr &MI, bool LiveCPSR, bool &DefCPSR) {
781 bool HasDef = false;
782 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
783 const MachineOperand &MO = MI.getOperand(i);
784 if (!MO.isReg() || MO.isUndef() || MO.isUse())
785 continue;
786 if (MO.getReg() != ARM::CPSR)
787 continue;
788
789 DefCPSR = true;
790 if (!MO.isDead())
791 HasDef = true;
792 }
793
794 return HasDef || LiveCPSR;
795 }
796
UpdateCPSRUse(MachineInstr & MI,bool LiveCPSR)797 static bool UpdateCPSRUse(MachineInstr &MI, bool LiveCPSR) {
798 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
799 const MachineOperand &MO = MI.getOperand(i);
800 if (!MO.isReg() || MO.isUndef() || MO.isDef())
801 continue;
802 if (MO.getReg() != ARM::CPSR)
803 continue;
804 assert(LiveCPSR && "CPSR liveness tracking is wrong!");
805 if (MO.isKill()) {
806 LiveCPSR = false;
807 break;
808 }
809 }
810
811 return LiveCPSR;
812 }
813
ReduceMBB(MachineBasicBlock & MBB)814 bool Thumb2SizeReduce::ReduceMBB(MachineBasicBlock &MBB) {
815 bool Modified = false;
816
817 // Yes, CPSR could be livein.
818 bool LiveCPSR = MBB.isLiveIn(ARM::CPSR);
819 MachineInstr *CPSRDef = 0;
820
821 MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
822 MachineBasicBlock::iterator NextMII;
823 for (; MII != E; MII = NextMII) {
824 NextMII = llvm::next(MII);
825
826 MachineInstr *MI = &*MII;
827 LiveCPSR = UpdateCPSRUse(*MI, LiveCPSR);
828
829 unsigned Opcode = MI->getOpcode();
830 DenseMap<unsigned, unsigned>::iterator OPI = ReduceOpcodeMap.find(Opcode);
831 if (OPI != ReduceOpcodeMap.end()) {
832 const ReduceEntry &Entry = ReduceTable[OPI->second];
833 // Ignore "special" cases for now.
834 if (Entry.Special) {
835 if (ReduceSpecial(MBB, MI, Entry, LiveCPSR, CPSRDef)) {
836 Modified = true;
837 MachineBasicBlock::iterator I = prior(NextMII);
838 MI = &*I;
839 }
840 goto ProcessNext;
841 }
842
843 // Try to transform to a 16-bit two-address instruction.
844 if (Entry.NarrowOpc2 &&
845 ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef)) {
846 Modified = true;
847 MachineBasicBlock::iterator I = prior(NextMII);
848 MI = &*I;
849 goto ProcessNext;
850 }
851
852 // Try to transform to a 16-bit non-two-address instruction.
853 if (Entry.NarrowOpc1 &&
854 ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef)) {
855 Modified = true;
856 MachineBasicBlock::iterator I = prior(NextMII);
857 MI = &*I;
858 }
859 }
860
861 ProcessNext:
862 bool DefCPSR = false;
863 LiveCPSR = UpdateCPSRDef(*MI, LiveCPSR, DefCPSR);
864 if (MI->getDesc().isCall())
865 // Calls don't really set CPSR.
866 CPSRDef = 0;
867 else if (DefCPSR)
868 // This is the last CPSR defining instruction.
869 CPSRDef = MI;
870 }
871
872 return Modified;
873 }
874
runOnMachineFunction(MachineFunction & MF)875 bool Thumb2SizeReduce::runOnMachineFunction(MachineFunction &MF) {
876 const TargetMachine &TM = MF.getTarget();
877 TII = static_cast<const Thumb2InstrInfo*>(TM.getInstrInfo());
878 STI = &TM.getSubtarget<ARMSubtarget>();
879
880 bool Modified = false;
881 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
882 Modified |= ReduceMBB(*I);
883 return Modified;
884 }
885
886 /// createThumb2SizeReductionPass - Returns an instance of the Thumb2 size
887 /// reduction pass.
createThumb2SizeReductionPass()888 FunctionPass *llvm::createThumb2SizeReductionPass() {
889 return new Thumb2SizeReduce();
890 }
891