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223e47cc LB |
1 | //===- InstCombineSelect.cpp ----------------------------------------------===// |
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 | // This file implements the visitSelect function. | |
11 | // | |
12 | //===----------------------------------------------------------------------===// | |
13 | ||
14 | #include "InstCombine.h" | |
223e47cc LB |
15 | #include "llvm/Analysis/ConstantFolding.h" |
16 | #include "llvm/Analysis/InstructionSimplify.h" | |
1a4d82fc | 17 | #include "llvm/IR/PatternMatch.h" |
223e47cc LB |
18 | using namespace llvm; |
19 | using namespace PatternMatch; | |
20 | ||
1a4d82fc JJ |
21 | #define DEBUG_TYPE "instcombine" |
22 | ||
223e47cc LB |
23 | /// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms, |
24 | /// returning the kind and providing the out parameter results if we | |
25 | /// successfully match. | |
26 | static SelectPatternFlavor | |
27 | MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) { | |
28 | SelectInst *SI = dyn_cast<SelectInst>(V); | |
1a4d82fc | 29 | if (!SI) return SPF_UNKNOWN; |
223e47cc LB |
30 | |
31 | ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition()); | |
1a4d82fc JJ |
32 | if (!ICI) return SPF_UNKNOWN; |
33 | ||
34 | ICmpInst::Predicate Pred = ICI->getPredicate(); | |
35 | Value *CmpLHS = ICI->getOperand(0); | |
36 | Value *CmpRHS = ICI->getOperand(1); | |
37 | Value *TrueVal = SI->getTrueValue(); | |
38 | Value *FalseVal = SI->getFalseValue(); | |
223e47cc | 39 | |
1a4d82fc JJ |
40 | LHS = CmpLHS; |
41 | RHS = CmpRHS; | |
223e47cc LB |
42 | |
43 | // (icmp X, Y) ? X : Y | |
1a4d82fc JJ |
44 | if (TrueVal == CmpLHS && FalseVal == CmpRHS) { |
45 | switch (Pred) { | |
223e47cc LB |
46 | default: return SPF_UNKNOWN; // Equality. |
47 | case ICmpInst::ICMP_UGT: | |
48 | case ICmpInst::ICMP_UGE: return SPF_UMAX; | |
49 | case ICmpInst::ICMP_SGT: | |
50 | case ICmpInst::ICMP_SGE: return SPF_SMAX; | |
51 | case ICmpInst::ICMP_ULT: | |
52 | case ICmpInst::ICMP_ULE: return SPF_UMIN; | |
53 | case ICmpInst::ICMP_SLT: | |
54 | case ICmpInst::ICMP_SLE: return SPF_SMIN; | |
55 | } | |
56 | } | |
57 | ||
58 | // (icmp X, Y) ? Y : X | |
1a4d82fc JJ |
59 | if (TrueVal == CmpRHS && FalseVal == CmpLHS) { |
60 | switch (Pred) { | |
61 | default: return SPF_UNKNOWN; // Equality. | |
62 | case ICmpInst::ICMP_UGT: | |
63 | case ICmpInst::ICMP_UGE: return SPF_UMIN; | |
64 | case ICmpInst::ICMP_SGT: | |
65 | case ICmpInst::ICMP_SGE: return SPF_SMIN; | |
66 | case ICmpInst::ICMP_ULT: | |
67 | case ICmpInst::ICMP_ULE: return SPF_UMAX; | |
68 | case ICmpInst::ICMP_SLT: | |
69 | case ICmpInst::ICMP_SLE: return SPF_SMAX; | |
70 | } | |
71 | } | |
72 | ||
73 | if (ConstantInt *C1 = dyn_cast<ConstantInt>(CmpRHS)) { | |
74 | if ((CmpLHS == TrueVal && match(FalseVal, m_Neg(m_Specific(CmpLHS)))) || | |
75 | (CmpLHS == FalseVal && match(TrueVal, m_Neg(m_Specific(CmpLHS))))) { | |
76 | ||
77 | // ABS(X) ==> (X >s 0) ? X : -X and (X >s -1) ? X : -X | |
78 | // NABS(X) ==> (X >s 0) ? -X : X and (X >s -1) ? -X : X | |
79 | if (Pred == ICmpInst::ICMP_SGT && (C1->isZero() || C1->isMinusOne())) { | |
80 | return (CmpLHS == TrueVal) ? SPF_ABS : SPF_NABS; | |
81 | } | |
82 | ||
83 | // ABS(X) ==> (X <s 0) ? -X : X and (X <s 1) ? -X : X | |
84 | // NABS(X) ==> (X <s 0) ? X : -X and (X <s 1) ? X : -X | |
85 | if (Pred == ICmpInst::ICMP_SLT && (C1->isZero() || C1->isOne())) { | |
86 | return (CmpLHS == FalseVal) ? SPF_ABS : SPF_NABS; | |
87 | } | |
223e47cc LB |
88 | } |
89 | } | |
90 | ||
91 | // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5) | |
92 | ||
93 | return SPF_UNKNOWN; | |
94 | } | |
95 | ||
96 | ||
97 | /// GetSelectFoldableOperands - We want to turn code that looks like this: | |
98 | /// %C = or %A, %B | |
99 | /// %D = select %cond, %C, %A | |
100 | /// into: | |
101 | /// %C = select %cond, %B, 0 | |
102 | /// %D = or %A, %C | |
103 | /// | |
104 | /// Assuming that the specified instruction is an operand to the select, return | |
105 | /// a bitmask indicating which operands of this instruction are foldable if they | |
106 | /// equal the other incoming value of the select. | |
107 | /// | |
108 | static unsigned GetSelectFoldableOperands(Instruction *I) { | |
109 | switch (I->getOpcode()) { | |
110 | case Instruction::Add: | |
111 | case Instruction::Mul: | |
112 | case Instruction::And: | |
113 | case Instruction::Or: | |
114 | case Instruction::Xor: | |
115 | return 3; // Can fold through either operand. | |
116 | case Instruction::Sub: // Can only fold on the amount subtracted. | |
117 | case Instruction::Shl: // Can only fold on the shift amount. | |
118 | case Instruction::LShr: | |
119 | case Instruction::AShr: | |
120 | return 1; | |
121 | default: | |
122 | return 0; // Cannot fold | |
123 | } | |
124 | } | |
125 | ||
126 | /// GetSelectFoldableConstant - For the same transformation as the previous | |
127 | /// function, return the identity constant that goes into the select. | |
128 | static Constant *GetSelectFoldableConstant(Instruction *I) { | |
129 | switch (I->getOpcode()) { | |
130 | default: llvm_unreachable("This cannot happen!"); | |
131 | case Instruction::Add: | |
132 | case Instruction::Sub: | |
133 | case Instruction::Or: | |
134 | case Instruction::Xor: | |
135 | case Instruction::Shl: | |
136 | case Instruction::LShr: | |
137 | case Instruction::AShr: | |
138 | return Constant::getNullValue(I->getType()); | |
139 | case Instruction::And: | |
140 | return Constant::getAllOnesValue(I->getType()); | |
141 | case Instruction::Mul: | |
142 | return ConstantInt::get(I->getType(), 1); | |
143 | } | |
144 | } | |
145 | ||
146 | /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI | |
147 | /// have the same opcode and only one use each. Try to simplify this. | |
148 | Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI, | |
149 | Instruction *FI) { | |
150 | if (TI->getNumOperands() == 1) { | |
151 | // If this is a non-volatile load or a cast from the same type, | |
152 | // merge. | |
153 | if (TI->isCast()) { | |
1a4d82fc JJ |
154 | Type *FIOpndTy = FI->getOperand(0)->getType(); |
155 | if (TI->getOperand(0)->getType() != FIOpndTy) | |
156 | return nullptr; | |
223e47cc LB |
157 | // The select condition may be a vector. We may only change the operand |
158 | // type if the vector width remains the same (and matches the condition). | |
159 | Type *CondTy = SI.getCondition()->getType(); | |
1a4d82fc JJ |
160 | if (CondTy->isVectorTy() && (!FIOpndTy->isVectorTy() || |
161 | CondTy->getVectorNumElements() != FIOpndTy->getVectorNumElements())) | |
162 | return nullptr; | |
223e47cc | 163 | } else { |
1a4d82fc | 164 | return nullptr; // unknown unary op. |
223e47cc LB |
165 | } |
166 | ||
167 | // Fold this by inserting a select from the input values. | |
168 | Value *NewSI = Builder->CreateSelect(SI.getCondition(), TI->getOperand(0), | |
169 | FI->getOperand(0), SI.getName()+".v"); | |
170 | return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, | |
171 | TI->getType()); | |
172 | } | |
173 | ||
174 | // Only handle binary operators here. | |
175 | if (!isa<BinaryOperator>(TI)) | |
1a4d82fc | 176 | return nullptr; |
223e47cc LB |
177 | |
178 | // Figure out if the operations have any operands in common. | |
179 | Value *MatchOp, *OtherOpT, *OtherOpF; | |
180 | bool MatchIsOpZero; | |
181 | if (TI->getOperand(0) == FI->getOperand(0)) { | |
182 | MatchOp = TI->getOperand(0); | |
183 | OtherOpT = TI->getOperand(1); | |
184 | OtherOpF = FI->getOperand(1); | |
185 | MatchIsOpZero = true; | |
186 | } else if (TI->getOperand(1) == FI->getOperand(1)) { | |
187 | MatchOp = TI->getOperand(1); | |
188 | OtherOpT = TI->getOperand(0); | |
189 | OtherOpF = FI->getOperand(0); | |
190 | MatchIsOpZero = false; | |
191 | } else if (!TI->isCommutative()) { | |
1a4d82fc | 192 | return nullptr; |
223e47cc LB |
193 | } else if (TI->getOperand(0) == FI->getOperand(1)) { |
194 | MatchOp = TI->getOperand(0); | |
195 | OtherOpT = TI->getOperand(1); | |
196 | OtherOpF = FI->getOperand(0); | |
197 | MatchIsOpZero = true; | |
198 | } else if (TI->getOperand(1) == FI->getOperand(0)) { | |
199 | MatchOp = TI->getOperand(1); | |
200 | OtherOpT = TI->getOperand(0); | |
201 | OtherOpF = FI->getOperand(1); | |
202 | MatchIsOpZero = true; | |
203 | } else { | |
1a4d82fc | 204 | return nullptr; |
223e47cc LB |
205 | } |
206 | ||
207 | // If we reach here, they do have operations in common. | |
208 | Value *NewSI = Builder->CreateSelect(SI.getCondition(), OtherOpT, | |
209 | OtherOpF, SI.getName()+".v"); | |
210 | ||
211 | if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) { | |
212 | if (MatchIsOpZero) | |
213 | return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI); | |
214 | else | |
215 | return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp); | |
216 | } | |
217 | llvm_unreachable("Shouldn't get here"); | |
218 | } | |
219 | ||
220 | static bool isSelect01(Constant *C1, Constant *C2) { | |
221 | ConstantInt *C1I = dyn_cast<ConstantInt>(C1); | |
222 | if (!C1I) | |
223 | return false; | |
224 | ConstantInt *C2I = dyn_cast<ConstantInt>(C2); | |
225 | if (!C2I) | |
226 | return false; | |
227 | if (!C1I->isZero() && !C2I->isZero()) // One side must be zero. | |
228 | return false; | |
229 | return C1I->isOne() || C1I->isAllOnesValue() || | |
230 | C2I->isOne() || C2I->isAllOnesValue(); | |
231 | } | |
232 | ||
233 | /// FoldSelectIntoOp - Try fold the select into one of the operands to | |
234 | /// facilitate further optimization. | |
235 | Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal, | |
236 | Value *FalseVal) { | |
237 | // See the comment above GetSelectFoldableOperands for a description of the | |
238 | // transformation we are doing here. | |
239 | if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) { | |
240 | if (TVI->hasOneUse() && TVI->getNumOperands() == 2 && | |
241 | !isa<Constant>(FalseVal)) { | |
242 | if (unsigned SFO = GetSelectFoldableOperands(TVI)) { | |
243 | unsigned OpToFold = 0; | |
244 | if ((SFO & 1) && FalseVal == TVI->getOperand(0)) { | |
245 | OpToFold = 1; | |
246 | } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) { | |
247 | OpToFold = 2; | |
248 | } | |
249 | ||
250 | if (OpToFold) { | |
251 | Constant *C = GetSelectFoldableConstant(TVI); | |
252 | Value *OOp = TVI->getOperand(2-OpToFold); | |
253 | // Avoid creating select between 2 constants unless it's selecting | |
254 | // between 0, 1 and -1. | |
255 | if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { | |
256 | Value *NewSel = Builder->CreateSelect(SI.getCondition(), OOp, C); | |
257 | NewSel->takeName(TVI); | |
258 | BinaryOperator *TVI_BO = cast<BinaryOperator>(TVI); | |
259 | BinaryOperator *BO = BinaryOperator::Create(TVI_BO->getOpcode(), | |
260 | FalseVal, NewSel); | |
261 | if (isa<PossiblyExactOperator>(BO)) | |
262 | BO->setIsExact(TVI_BO->isExact()); | |
263 | if (isa<OverflowingBinaryOperator>(BO)) { | |
264 | BO->setHasNoUnsignedWrap(TVI_BO->hasNoUnsignedWrap()); | |
265 | BO->setHasNoSignedWrap(TVI_BO->hasNoSignedWrap()); | |
266 | } | |
267 | return BO; | |
268 | } | |
269 | } | |
270 | } | |
271 | } | |
272 | } | |
273 | ||
274 | if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) { | |
275 | if (FVI->hasOneUse() && FVI->getNumOperands() == 2 && | |
276 | !isa<Constant>(TrueVal)) { | |
277 | if (unsigned SFO = GetSelectFoldableOperands(FVI)) { | |
278 | unsigned OpToFold = 0; | |
279 | if ((SFO & 1) && TrueVal == FVI->getOperand(0)) { | |
280 | OpToFold = 1; | |
281 | } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) { | |
282 | OpToFold = 2; | |
283 | } | |
284 | ||
285 | if (OpToFold) { | |
286 | Constant *C = GetSelectFoldableConstant(FVI); | |
287 | Value *OOp = FVI->getOperand(2-OpToFold); | |
288 | // Avoid creating select between 2 constants unless it's selecting | |
289 | // between 0, 1 and -1. | |
290 | if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { | |
291 | Value *NewSel = Builder->CreateSelect(SI.getCondition(), C, OOp); | |
292 | NewSel->takeName(FVI); | |
293 | BinaryOperator *FVI_BO = cast<BinaryOperator>(FVI); | |
294 | BinaryOperator *BO = BinaryOperator::Create(FVI_BO->getOpcode(), | |
295 | TrueVal, NewSel); | |
296 | if (isa<PossiblyExactOperator>(BO)) | |
297 | BO->setIsExact(FVI_BO->isExact()); | |
298 | if (isa<OverflowingBinaryOperator>(BO)) { | |
299 | BO->setHasNoUnsignedWrap(FVI_BO->hasNoUnsignedWrap()); | |
300 | BO->setHasNoSignedWrap(FVI_BO->hasNoSignedWrap()); | |
301 | } | |
302 | return BO; | |
303 | } | |
304 | } | |
305 | } | |
306 | } | |
307 | } | |
308 | ||
1a4d82fc | 309 | return nullptr; |
223e47cc LB |
310 | } |
311 | ||
312 | /// SimplifyWithOpReplaced - See if V simplifies when its operand Op is | |
313 | /// replaced with RepOp. | |
314 | static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp, | |
970d7e83 | 315 | const DataLayout *TD, |
1a4d82fc | 316 | const TargetLibraryInfo *TLI, |
85aaf69f | 317 | DominatorTree *DT, AssumptionCache *AC) { |
223e47cc LB |
318 | // Trivial replacement. |
319 | if (V == Op) | |
320 | return RepOp; | |
321 | ||
322 | Instruction *I = dyn_cast<Instruction>(V); | |
323 | if (!I) | |
1a4d82fc | 324 | return nullptr; |
223e47cc LB |
325 | |
326 | // If this is a binary operator, try to simplify it with the replaced op. | |
327 | if (BinaryOperator *B = dyn_cast<BinaryOperator>(I)) { | |
328 | if (B->getOperand(0) == Op) | |
329 | return SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), TD, TLI); | |
330 | if (B->getOperand(1) == Op) | |
331 | return SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, TD, TLI); | |
332 | } | |
333 | ||
334 | // Same for CmpInsts. | |
335 | if (CmpInst *C = dyn_cast<CmpInst>(I)) { | |
336 | if (C->getOperand(0) == Op) | |
337 | return SimplifyCmpInst(C->getPredicate(), RepOp, C->getOperand(1), TD, | |
85aaf69f | 338 | TLI, DT, AC); |
223e47cc LB |
339 | if (C->getOperand(1) == Op) |
340 | return SimplifyCmpInst(C->getPredicate(), C->getOperand(0), RepOp, TD, | |
85aaf69f | 341 | TLI, DT, AC); |
223e47cc LB |
342 | } |
343 | ||
344 | // TODO: We could hand off more cases to instsimplify here. | |
345 | ||
346 | // If all operands are constant after substituting Op for RepOp then we can | |
347 | // constant fold the instruction. | |
348 | if (Constant *CRepOp = dyn_cast<Constant>(RepOp)) { | |
349 | // Build a list of all constant operands. | |
350 | SmallVector<Constant*, 8> ConstOps; | |
351 | for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { | |
352 | if (I->getOperand(i) == Op) | |
353 | ConstOps.push_back(CRepOp); | |
354 | else if (Constant *COp = dyn_cast<Constant>(I->getOperand(i))) | |
355 | ConstOps.push_back(COp); | |
356 | else | |
357 | break; | |
358 | } | |
359 | ||
360 | // All operands were constants, fold it. | |
361 | if (ConstOps.size() == I->getNumOperands()) { | |
970d7e83 LB |
362 | if (CmpInst *C = dyn_cast<CmpInst>(I)) |
363 | return ConstantFoldCompareInstOperands(C->getPredicate(), ConstOps[0], | |
364 | ConstOps[1], TD, TLI); | |
365 | ||
223e47cc LB |
366 | if (LoadInst *LI = dyn_cast<LoadInst>(I)) |
367 | if (!LI->isVolatile()) | |
368 | return ConstantFoldLoadFromConstPtr(ConstOps[0], TD); | |
369 | ||
370 | return ConstantFoldInstOperands(I->getOpcode(), I->getType(), | |
371 | ConstOps, TD, TLI); | |
372 | } | |
373 | } | |
374 | ||
1a4d82fc JJ |
375 | return nullptr; |
376 | } | |
377 | ||
378 | /// foldSelectICmpAndOr - We want to turn: | |
379 | /// (select (icmp eq (and X, C1), 0), Y, (or Y, C2)) | |
380 | /// into: | |
381 | /// (or (shl (and X, C1), C3), y) | |
382 | /// iff: | |
383 | /// C1 and C2 are both powers of 2 | |
384 | /// where: | |
385 | /// C3 = Log(C2) - Log(C1) | |
386 | /// | |
387 | /// This transform handles cases where: | |
388 | /// 1. The icmp predicate is inverted | |
389 | /// 2. The select operands are reversed | |
390 | /// 3. The magnitude of C2 and C1 are flipped | |
85aaf69f | 391 | static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal, |
1a4d82fc JJ |
392 | Value *FalseVal, |
393 | InstCombiner::BuilderTy *Builder) { | |
394 | const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition()); | |
395 | if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy()) | |
396 | return nullptr; | |
397 | ||
398 | Value *CmpLHS = IC->getOperand(0); | |
399 | Value *CmpRHS = IC->getOperand(1); | |
400 | ||
401 | if (!match(CmpRHS, m_Zero())) | |
402 | return nullptr; | |
403 | ||
404 | Value *X; | |
405 | const APInt *C1; | |
406 | if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1)))) | |
407 | return nullptr; | |
408 | ||
409 | const APInt *C2; | |
1a4d82fc JJ |
410 | bool OrOnTrueVal = false; |
411 | bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2))); | |
412 | if (!OrOnFalseVal) | |
413 | OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2))); | |
414 | ||
415 | if (!OrOnFalseVal && !OrOnTrueVal) | |
416 | return nullptr; | |
417 | ||
418 | Value *V = CmpLHS; | |
419 | Value *Y = OrOnFalseVal ? TrueVal : FalseVal; | |
420 | ||
421 | unsigned C1Log = C1->logBase2(); | |
422 | unsigned C2Log = C2->logBase2(); | |
423 | if (C2Log > C1Log) { | |
424 | V = Builder->CreateZExtOrTrunc(V, Y->getType()); | |
425 | V = Builder->CreateShl(V, C2Log - C1Log); | |
426 | } else if (C1Log > C2Log) { | |
427 | V = Builder->CreateLShr(V, C1Log - C2Log); | |
428 | V = Builder->CreateZExtOrTrunc(V, Y->getType()); | |
429 | } else | |
430 | V = Builder->CreateZExtOrTrunc(V, Y->getType()); | |
431 | ||
432 | ICmpInst::Predicate Pred = IC->getPredicate(); | |
433 | if ((Pred == ICmpInst::ICMP_NE && OrOnFalseVal) || | |
434 | (Pred == ICmpInst::ICMP_EQ && OrOnTrueVal)) | |
435 | V = Builder->CreateXor(V, *C2); | |
436 | ||
437 | return Builder->CreateOr(V, Y); | |
223e47cc LB |
438 | } |
439 | ||
440 | /// visitSelectInstWithICmp - Visit a SelectInst that has an | |
441 | /// ICmpInst as its first operand. | |
442 | /// | |
443 | Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI, | |
444 | ICmpInst *ICI) { | |
445 | bool Changed = false; | |
446 | ICmpInst::Predicate Pred = ICI->getPredicate(); | |
447 | Value *CmpLHS = ICI->getOperand(0); | |
448 | Value *CmpRHS = ICI->getOperand(1); | |
449 | Value *TrueVal = SI.getTrueValue(); | |
450 | Value *FalseVal = SI.getFalseValue(); | |
451 | ||
452 | // Check cases where the comparison is with a constant that | |
453 | // can be adjusted to fit the min/max idiom. We may move or edit ICI | |
454 | // here, so make sure the select is the only user. | |
455 | if (ICI->hasOneUse()) | |
456 | if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) { | |
457 | // X < MIN ? T : F --> F | |
458 | if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT) | |
459 | && CI->isMinValue(Pred == ICmpInst::ICMP_SLT)) | |
460 | return ReplaceInstUsesWith(SI, FalseVal); | |
461 | // X > MAX ? T : F --> F | |
462 | else if ((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_UGT) | |
463 | && CI->isMaxValue(Pred == ICmpInst::ICMP_SGT)) | |
464 | return ReplaceInstUsesWith(SI, FalseVal); | |
465 | switch (Pred) { | |
466 | default: break; | |
467 | case ICmpInst::ICMP_ULT: | |
468 | case ICmpInst::ICMP_SLT: | |
469 | case ICmpInst::ICMP_UGT: | |
470 | case ICmpInst::ICMP_SGT: { | |
471 | // These transformations only work for selects over integers. | |
472 | IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType()); | |
473 | if (!SelectTy) | |
474 | break; | |
475 | ||
476 | Constant *AdjustedRHS; | |
477 | if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT) | |
478 | AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1); | |
479 | else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT) | |
480 | AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1); | |
481 | ||
482 | // X > C ? X : C+1 --> X < C+1 ? C+1 : X | |
483 | // X < C ? X : C-1 --> X > C-1 ? C-1 : X | |
484 | if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || | |
485 | (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) | |
486 | ; // Nothing to do here. Values match without any sign/zero extension. | |
487 | ||
488 | // Types do not match. Instead of calculating this with mixed types | |
489 | // promote all to the larger type. This enables scalar evolution to | |
490 | // analyze this expression. | |
491 | else if (CmpRHS->getType()->getScalarSizeInBits() | |
492 | < SelectTy->getBitWidth()) { | |
493 | Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy); | |
494 | ||
495 | // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X | |
496 | // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X | |
497 | // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X | |
498 | // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X | |
499 | if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) && | |
500 | sextRHS == FalseVal) { | |
501 | CmpLHS = TrueVal; | |
502 | AdjustedRHS = sextRHS; | |
503 | } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) && | |
504 | sextRHS == TrueVal) { | |
505 | CmpLHS = FalseVal; | |
506 | AdjustedRHS = sextRHS; | |
507 | } else if (ICI->isUnsigned()) { | |
508 | Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy); | |
509 | // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X | |
510 | // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X | |
511 | // zext + signed compare cannot be changed: | |
512 | // 0xff <s 0x00, but 0x00ff >s 0x0000 | |
513 | if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) && | |
514 | zextRHS == FalseVal) { | |
515 | CmpLHS = TrueVal; | |
516 | AdjustedRHS = zextRHS; | |
517 | } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) && | |
518 | zextRHS == TrueVal) { | |
519 | CmpLHS = FalseVal; | |
520 | AdjustedRHS = zextRHS; | |
521 | } else | |
522 | break; | |
523 | } else | |
524 | break; | |
525 | } else | |
526 | break; | |
527 | ||
528 | Pred = ICmpInst::getSwappedPredicate(Pred); | |
529 | CmpRHS = AdjustedRHS; | |
530 | std::swap(FalseVal, TrueVal); | |
531 | ICI->setPredicate(Pred); | |
532 | ICI->setOperand(0, CmpLHS); | |
533 | ICI->setOperand(1, CmpRHS); | |
534 | SI.setOperand(1, TrueVal); | |
535 | SI.setOperand(2, FalseVal); | |
536 | ||
537 | // Move ICI instruction right before the select instruction. Otherwise | |
538 | // the sext/zext value may be defined after the ICI instruction uses it. | |
539 | ICI->moveBefore(&SI); | |
540 | ||
541 | Changed = true; | |
542 | break; | |
543 | } | |
544 | } | |
545 | } | |
546 | ||
547 | // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1 | |
548 | // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1 | |
549 | // FIXME: Type and constness constraints could be lifted, but we have to | |
550 | // watch code size carefully. We should consider xor instead of | |
551 | // sub/add when we decide to do that. | |
552 | if (IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) { | |
553 | if (TrueVal->getType() == Ty) { | |
554 | if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) { | |
1a4d82fc | 555 | ConstantInt *C1 = nullptr, *C2 = nullptr; |
223e47cc LB |
556 | if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) { |
557 | C1 = dyn_cast<ConstantInt>(TrueVal); | |
558 | C2 = dyn_cast<ConstantInt>(FalseVal); | |
559 | } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) { | |
560 | C1 = dyn_cast<ConstantInt>(FalseVal); | |
561 | C2 = dyn_cast<ConstantInt>(TrueVal); | |
562 | } | |
563 | if (C1 && C2) { | |
564 | // This shift results in either -1 or 0. | |
565 | Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1); | |
566 | ||
567 | // Check if we can express the operation with a single or. | |
568 | if (C2->isAllOnesValue()) | |
569 | return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1)); | |
570 | ||
571 | Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue()); | |
572 | return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1)); | |
573 | } | |
574 | } | |
575 | } | |
576 | } | |
577 | ||
578 | // If we have an equality comparison then we know the value in one of the | |
579 | // arms of the select. See if substituting this value into the arm and | |
580 | // simplifying the result yields the same value as the other arm. | |
581 | if (Pred == ICmpInst::ICMP_EQ) { | |
85aaf69f SL |
582 | if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) == |
583 | TrueVal || | |
584 | SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) == | |
585 | TrueVal) | |
223e47cc | 586 | return ReplaceInstUsesWith(SI, FalseVal); |
85aaf69f SL |
587 | if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) == |
588 | FalseVal || | |
589 | SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) == | |
590 | FalseVal) | |
223e47cc LB |
591 | return ReplaceInstUsesWith(SI, FalseVal); |
592 | } else if (Pred == ICmpInst::ICMP_NE) { | |
85aaf69f SL |
593 | if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) == |
594 | FalseVal || | |
595 | SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) == | |
596 | FalseVal) | |
223e47cc | 597 | return ReplaceInstUsesWith(SI, TrueVal); |
85aaf69f SL |
598 | if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) == |
599 | TrueVal || | |
600 | SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) == | |
601 | TrueVal) | |
223e47cc LB |
602 | return ReplaceInstUsesWith(SI, TrueVal); |
603 | } | |
604 | ||
605 | // NOTE: if we wanted to, this is where to detect integer MIN/MAX | |
606 | ||
607 | if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) { | |
608 | if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) { | |
609 | // Transform (X == C) ? X : Y -> (X == C) ? C : Y | |
610 | SI.setOperand(1, CmpRHS); | |
611 | Changed = true; | |
612 | } else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) { | |
613 | // Transform (X != C) ? Y : X -> (X != C) ? Y : C | |
614 | SI.setOperand(2, CmpRHS); | |
615 | Changed = true; | |
616 | } | |
617 | } | |
618 | ||
85aaf69f SL |
619 | if (unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits()) { |
620 | APInt MinSignedValue = APInt::getSignBit(BitWidth); | |
621 | Value *X; | |
622 | const APInt *Y, *C; | |
623 | bool TrueWhenUnset; | |
624 | bool IsBitTest = false; | |
625 | if (ICmpInst::isEquality(Pred) && | |
626 | match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) && | |
627 | match(CmpRHS, m_Zero())) { | |
628 | IsBitTest = true; | |
629 | TrueWhenUnset = Pred == ICmpInst::ICMP_EQ; | |
630 | } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) { | |
631 | X = CmpLHS; | |
632 | Y = &MinSignedValue; | |
633 | IsBitTest = true; | |
634 | TrueWhenUnset = false; | |
635 | } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) { | |
636 | X = CmpLHS; | |
637 | Y = &MinSignedValue; | |
638 | IsBitTest = true; | |
639 | TrueWhenUnset = true; | |
640 | } | |
641 | if (IsBitTest) { | |
642 | Value *V = nullptr; | |
643 | // (X & Y) == 0 ? X : X ^ Y --> X & ~Y | |
644 | if (TrueWhenUnset && TrueVal == X && | |
645 | match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) | |
646 | V = Builder->CreateAnd(X, ~(*Y)); | |
647 | // (X & Y) != 0 ? X ^ Y : X --> X & ~Y | |
648 | else if (!TrueWhenUnset && FalseVal == X && | |
649 | match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) | |
650 | V = Builder->CreateAnd(X, ~(*Y)); | |
651 | // (X & Y) == 0 ? X ^ Y : X --> X | Y | |
652 | else if (TrueWhenUnset && FalseVal == X && | |
653 | match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) | |
654 | V = Builder->CreateOr(X, *Y); | |
655 | // (X & Y) != 0 ? X : X ^ Y --> X | Y | |
656 | else if (!TrueWhenUnset && TrueVal == X && | |
657 | match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) | |
658 | V = Builder->CreateOr(X, *Y); | |
659 | ||
660 | if (V) | |
661 | return ReplaceInstUsesWith(SI, V); | |
662 | } | |
663 | } | |
664 | ||
1a4d82fc JJ |
665 | if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder)) |
666 | return ReplaceInstUsesWith(SI, V); | |
667 | ||
668 | return Changed ? &SI : nullptr; | |
223e47cc LB |
669 | } |
670 | ||
671 | ||
672 | /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a | |
673 | /// PHI node (but the two may be in different blocks). See if the true/false | |
674 | /// values (V) are live in all of the predecessor blocks of the PHI. For | |
675 | /// example, cases like this cannot be mapped: | |
676 | /// | |
677 | /// X = phi [ C1, BB1], [C2, BB2] | |
678 | /// Y = add | |
679 | /// Z = select X, Y, 0 | |
680 | /// | |
681 | /// because Y is not live in BB1/BB2. | |
682 | /// | |
683 | static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V, | |
684 | const SelectInst &SI) { | |
685 | // If the value is a non-instruction value like a constant or argument, it | |
686 | // can always be mapped. | |
687 | const Instruction *I = dyn_cast<Instruction>(V); | |
1a4d82fc | 688 | if (!I) return true; |
223e47cc LB |
689 | |
690 | // If V is a PHI node defined in the same block as the condition PHI, we can | |
691 | // map the arguments. | |
692 | const PHINode *CondPHI = cast<PHINode>(SI.getCondition()); | |
693 | ||
694 | if (const PHINode *VP = dyn_cast<PHINode>(I)) | |
695 | if (VP->getParent() == CondPHI->getParent()) | |
696 | return true; | |
697 | ||
698 | // Otherwise, if the PHI and select are defined in the same block and if V is | |
699 | // defined in a different block, then we can transform it. | |
700 | if (SI.getParent() == CondPHI->getParent() && | |
701 | I->getParent() != CondPHI->getParent()) | |
702 | return true; | |
703 | ||
704 | // Otherwise we have a 'hard' case and we can't tell without doing more | |
705 | // detailed dominator based analysis, punt. | |
706 | return false; | |
707 | } | |
708 | ||
709 | /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form: | |
710 | /// SPF2(SPF1(A, B), C) | |
711 | Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, | |
712 | SelectPatternFlavor SPF1, | |
713 | Value *A, Value *B, | |
714 | Instruction &Outer, | |
715 | SelectPatternFlavor SPF2, Value *C) { | |
716 | if (C == A || C == B) { | |
717 | // MAX(MAX(A, B), B) -> MAX(A, B) | |
718 | // MIN(MIN(a, b), a) -> MIN(a, b) | |
719 | if (SPF1 == SPF2) | |
720 | return ReplaceInstUsesWith(Outer, Inner); | |
721 | ||
722 | // MAX(MIN(a, b), a) -> a | |
723 | // MIN(MAX(a, b), a) -> a | |
724 | if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) || | |
725 | (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) || | |
726 | (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) || | |
727 | (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN)) | |
728 | return ReplaceInstUsesWith(Outer, C); | |
729 | } | |
730 | ||
1a4d82fc JJ |
731 | if (SPF1 == SPF2) { |
732 | if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) { | |
733 | if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) { | |
734 | APInt ACB = CB->getValue(); | |
735 | APInt ACC = CC->getValue(); | |
736 | ||
737 | // MIN(MIN(A, 23), 97) -> MIN(A, 23) | |
738 | // MAX(MAX(A, 97), 23) -> MAX(A, 97) | |
739 | if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) || | |
740 | (SPF1 == SPF_SMIN && ACB.sle(ACC)) || | |
741 | (SPF1 == SPF_UMAX && ACB.uge(ACC)) || | |
742 | (SPF1 == SPF_SMAX && ACB.sge(ACC))) | |
743 | return ReplaceInstUsesWith(Outer, Inner); | |
744 | ||
745 | // MIN(MIN(A, 97), 23) -> MIN(A, 23) | |
746 | // MAX(MAX(A, 23), 97) -> MAX(A, 97) | |
747 | if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) || | |
748 | (SPF1 == SPF_SMIN && ACB.sgt(ACC)) || | |
749 | (SPF1 == SPF_UMAX && ACB.ult(ACC)) || | |
750 | (SPF1 == SPF_SMAX && ACB.slt(ACC))) { | |
751 | Outer.replaceUsesOfWith(Inner, A); | |
752 | return &Outer; | |
753 | } | |
754 | } | |
755 | } | |
756 | } | |
223e47cc | 757 | |
1a4d82fc JJ |
758 | // ABS(ABS(X)) -> ABS(X) |
759 | // NABS(NABS(X)) -> NABS(X) | |
760 | if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) { | |
761 | return ReplaceInstUsesWith(Outer, Inner); | |
762 | } | |
763 | ||
764 | // ABS(NABS(X)) -> ABS(X) | |
765 | // NABS(ABS(X)) -> NABS(X) | |
766 | if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) || | |
767 | (SPF1 == SPF_NABS && SPF2 == SPF_ABS)) { | |
768 | SelectInst *SI = cast<SelectInst>(Inner); | |
769 | Value *NewSI = Builder->CreateSelect( | |
770 | SI->getCondition(), SI->getFalseValue(), SI->getTrueValue()); | |
771 | return ReplaceInstUsesWith(Outer, NewSI); | |
772 | } | |
773 | return nullptr; | |
774 | } | |
223e47cc LB |
775 | |
776 | /// foldSelectICmpAnd - If one of the constants is zero (we know they can't | |
777 | /// both be) and we have an icmp instruction with zero, and we have an 'and' | |
778 | /// with the non-constant value and a power of two we can turn the select | |
779 | /// into a shift on the result of the 'and'. | |
780 | static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal, | |
781 | ConstantInt *FalseVal, | |
782 | InstCombiner::BuilderTy *Builder) { | |
783 | const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition()); | |
1a4d82fc JJ |
784 | if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy()) |
785 | return nullptr; | |
223e47cc LB |
786 | |
787 | if (!match(IC->getOperand(1), m_Zero())) | |
1a4d82fc | 788 | return nullptr; |
223e47cc LB |
789 | |
790 | ConstantInt *AndRHS; | |
791 | Value *LHS = IC->getOperand(0); | |
1a4d82fc JJ |
792 | if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS)))) |
793 | return nullptr; | |
223e47cc LB |
794 | |
795 | // If both select arms are non-zero see if we have a select of the form | |
796 | // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic | |
797 | // for 'x ? 2^n : 0' and fix the thing up at the end. | |
1a4d82fc | 798 | ConstantInt *Offset = nullptr; |
223e47cc LB |
799 | if (!TrueVal->isZero() && !FalseVal->isZero()) { |
800 | if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2()) | |
801 | Offset = FalseVal; | |
802 | else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2()) | |
803 | Offset = TrueVal; | |
804 | else | |
1a4d82fc | 805 | return nullptr; |
223e47cc LB |
806 | |
807 | // Adjust TrueVal and FalseVal to the offset. | |
808 | TrueVal = ConstantInt::get(Builder->getContext(), | |
809 | TrueVal->getValue() - Offset->getValue()); | |
810 | FalseVal = ConstantInt::get(Builder->getContext(), | |
811 | FalseVal->getValue() - Offset->getValue()); | |
812 | } | |
813 | ||
814 | // Make sure the mask in the 'and' and one of the select arms is a power of 2. | |
815 | if (!AndRHS->getValue().isPowerOf2() || | |
816 | (!TrueVal->getValue().isPowerOf2() && | |
817 | !FalseVal->getValue().isPowerOf2())) | |
1a4d82fc | 818 | return nullptr; |
223e47cc LB |
819 | |
820 | // Determine which shift is needed to transform result of the 'and' into the | |
821 | // desired result. | |
822 | ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal; | |
823 | unsigned ValZeros = ValC->getValue().logBase2(); | |
824 | unsigned AndZeros = AndRHS->getValue().logBase2(); | |
825 | ||
1a4d82fc JJ |
826 | // If types don't match we can still convert the select by introducing a zext |
827 | // or a trunc of the 'and'. The trunc case requires that all of the truncated | |
828 | // bits are zero, we can figure that out by looking at the 'and' mask. | |
829 | if (AndZeros >= ValC->getBitWidth()) | |
830 | return nullptr; | |
831 | ||
832 | Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType()); | |
223e47cc LB |
833 | if (ValZeros > AndZeros) |
834 | V = Builder->CreateShl(V, ValZeros - AndZeros); | |
835 | else if (ValZeros < AndZeros) | |
836 | V = Builder->CreateLShr(V, AndZeros - ValZeros); | |
837 | ||
838 | // Okay, now we know that everything is set up, we just don't know whether we | |
839 | // have a icmp_ne or icmp_eq and whether the true or false val is the zero. | |
840 | bool ShouldNotVal = !TrueVal->isZero(); | |
841 | ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE; | |
842 | if (ShouldNotVal) | |
843 | V = Builder->CreateXor(V, ValC); | |
844 | ||
845 | // Apply an offset if needed. | |
846 | if (Offset) | |
847 | V = Builder->CreateAdd(V, Offset); | |
848 | return V; | |
849 | } | |
850 | ||
851 | Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { | |
852 | Value *CondVal = SI.getCondition(); | |
853 | Value *TrueVal = SI.getTrueValue(); | |
854 | Value *FalseVal = SI.getFalseValue(); | |
855 | ||
85aaf69f SL |
856 | if (Value *V = |
857 | SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC)) | |
223e47cc LB |
858 | return ReplaceInstUsesWith(SI, V); |
859 | ||
860 | if (SI.getType()->isIntegerTy(1)) { | |
861 | if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) { | |
862 | if (C->getZExtValue()) { | |
863 | // Change: A = select B, true, C --> A = or B, C | |
864 | return BinaryOperator::CreateOr(CondVal, FalseVal); | |
865 | } | |
866 | // Change: A = select B, false, C --> A = and !B, C | |
867 | Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); | |
868 | return BinaryOperator::CreateAnd(NotCond, FalseVal); | |
1a4d82fc JJ |
869 | } |
870 | if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) { | |
223e47cc LB |
871 | if (C->getZExtValue() == false) { |
872 | // Change: A = select B, C, false --> A = and B, C | |
873 | return BinaryOperator::CreateAnd(CondVal, TrueVal); | |
874 | } | |
875 | // Change: A = select B, C, true --> A = or !B, C | |
876 | Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); | |
877 | return BinaryOperator::CreateOr(NotCond, TrueVal); | |
878 | } | |
879 | ||
880 | // select a, b, a -> a&b | |
881 | // select a, a, b -> a|b | |
882 | if (CondVal == TrueVal) | |
883 | return BinaryOperator::CreateOr(CondVal, FalseVal); | |
1a4d82fc | 884 | if (CondVal == FalseVal) |
223e47cc LB |
885 | return BinaryOperator::CreateAnd(CondVal, TrueVal); |
886 | ||
887 | // select a, ~a, b -> (~a)&b | |
888 | // select a, b, ~a -> (~a)|b | |
889 | if (match(TrueVal, m_Not(m_Specific(CondVal)))) | |
890 | return BinaryOperator::CreateAnd(TrueVal, FalseVal); | |
1a4d82fc | 891 | if (match(FalseVal, m_Not(m_Specific(CondVal)))) |
223e47cc LB |
892 | return BinaryOperator::CreateOr(TrueVal, FalseVal); |
893 | } | |
894 | ||
895 | // Selecting between two integer constants? | |
896 | if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal)) | |
897 | if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) { | |
898 | // select C, 1, 0 -> zext C to int | |
899 | if (FalseValC->isZero() && TrueValC->getValue() == 1) | |
900 | return new ZExtInst(CondVal, SI.getType()); | |
901 | ||
902 | // select C, -1, 0 -> sext C to int | |
903 | if (FalseValC->isZero() && TrueValC->isAllOnesValue()) | |
904 | return new SExtInst(CondVal, SI.getType()); | |
905 | ||
906 | // select C, 0, 1 -> zext !C to int | |
907 | if (TrueValC->isZero() && FalseValC->getValue() == 1) { | |
908 | Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); | |
909 | return new ZExtInst(NotCond, SI.getType()); | |
910 | } | |
911 | ||
912 | // select C, 0, -1 -> sext !C to int | |
913 | if (TrueValC->isZero() && FalseValC->isAllOnesValue()) { | |
914 | Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName()); | |
915 | return new SExtInst(NotCond, SI.getType()); | |
916 | } | |
917 | ||
918 | if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder)) | |
919 | return ReplaceInstUsesWith(SI, V); | |
920 | } | |
921 | ||
922 | // See if we are selecting two values based on a comparison of the two values. | |
923 | if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) { | |
924 | if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { | |
925 | // Transform (X == Y) ? X : Y -> Y | |
926 | if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { | |
927 | // This is not safe in general for floating point: | |
928 | // consider X== -0, Y== +0. | |
929 | // It becomes safe if either operand is a nonzero constant. | |
930 | ConstantFP *CFPt, *CFPf; | |
931 | if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && | |
932 | !CFPt->getValueAPF().isZero()) || | |
933 | ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && | |
934 | !CFPf->getValueAPF().isZero())) | |
935 | return ReplaceInstUsesWith(SI, FalseVal); | |
936 | } | |
937 | // Transform (X une Y) ? X : Y -> X | |
938 | if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { | |
939 | // This is not safe in general for floating point: | |
940 | // consider X== -0, Y== +0. | |
941 | // It becomes safe if either operand is a nonzero constant. | |
942 | ConstantFP *CFPt, *CFPf; | |
943 | if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && | |
944 | !CFPt->getValueAPF().isZero()) || | |
945 | ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && | |
946 | !CFPf->getValueAPF().isZero())) | |
947 | return ReplaceInstUsesWith(SI, TrueVal); | |
948 | } | |
223e47cc | 949 | |
85aaf69f SL |
950 | // Canonicalize to use ordered comparisons by swapping the select |
951 | // operands. | |
952 | // | |
953 | // e.g. | |
954 | // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X | |
955 | if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) { | |
956 | FCmpInst::Predicate InvPred = FCI->getInversePredicate(); | |
957 | Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal, | |
958 | FCI->getName() + ".inv"); | |
959 | ||
960 | return SelectInst::Create(NewCond, FalseVal, TrueVal, | |
961 | SI.getName() + ".p"); | |
962 | } | |
963 | ||
964 | // NOTE: if we wanted to, this is where to detect MIN/MAX | |
223e47cc LB |
965 | } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ |
966 | // Transform (X == Y) ? Y : X -> X | |
967 | if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { | |
968 | // This is not safe in general for floating point: | |
969 | // consider X== -0, Y== +0. | |
970 | // It becomes safe if either operand is a nonzero constant. | |
971 | ConstantFP *CFPt, *CFPf; | |
972 | if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && | |
973 | !CFPt->getValueAPF().isZero()) || | |
974 | ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && | |
975 | !CFPf->getValueAPF().isZero())) | |
976 | return ReplaceInstUsesWith(SI, FalseVal); | |
977 | } | |
978 | // Transform (X une Y) ? Y : X -> Y | |
979 | if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { | |
980 | // This is not safe in general for floating point: | |
981 | // consider X== -0, Y== +0. | |
982 | // It becomes safe if either operand is a nonzero constant. | |
983 | ConstantFP *CFPt, *CFPf; | |
984 | if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && | |
985 | !CFPt->getValueAPF().isZero()) || | |
986 | ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && | |
987 | !CFPf->getValueAPF().isZero())) | |
988 | return ReplaceInstUsesWith(SI, TrueVal); | |
989 | } | |
85aaf69f SL |
990 | |
991 | // Canonicalize to use ordered comparisons by swapping the select | |
992 | // operands. | |
993 | // | |
994 | // e.g. | |
995 | // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y | |
996 | if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) { | |
997 | FCmpInst::Predicate InvPred = FCI->getInversePredicate(); | |
998 | Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal, | |
999 | FCI->getName() + ".inv"); | |
1000 | ||
1001 | return SelectInst::Create(NewCond, FalseVal, TrueVal, | |
1002 | SI.getName() + ".p"); | |
1003 | } | |
1004 | ||
223e47cc LB |
1005 | // NOTE: if we wanted to, this is where to detect MIN/MAX |
1006 | } | |
1007 | // NOTE: if we wanted to, this is where to detect ABS | |
1008 | } | |
1009 | ||
1010 | // See if we are selecting two values based on a comparison of the two values. | |
1011 | if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal)) | |
1012 | if (Instruction *Result = visitSelectInstWithICmp(SI, ICI)) | |
1013 | return Result; | |
1014 | ||
1015 | if (Instruction *TI = dyn_cast<Instruction>(TrueVal)) | |
1016 | if (Instruction *FI = dyn_cast<Instruction>(FalseVal)) | |
1017 | if (TI->hasOneUse() && FI->hasOneUse()) { | |
1a4d82fc | 1018 | Instruction *AddOp = nullptr, *SubOp = nullptr; |
223e47cc LB |
1019 | |
1020 | // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z)) | |
1021 | if (TI->getOpcode() == FI->getOpcode()) | |
1022 | if (Instruction *IV = FoldSelectOpOp(SI, TI, FI)) | |
1023 | return IV; | |
1024 | ||
1025 | // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is | |
1026 | // even legal for FP. | |
1027 | if ((TI->getOpcode() == Instruction::Sub && | |
1028 | FI->getOpcode() == Instruction::Add) || | |
1029 | (TI->getOpcode() == Instruction::FSub && | |
1030 | FI->getOpcode() == Instruction::FAdd)) { | |
1031 | AddOp = FI; SubOp = TI; | |
1032 | } else if ((FI->getOpcode() == Instruction::Sub && | |
1033 | TI->getOpcode() == Instruction::Add) || | |
1034 | (FI->getOpcode() == Instruction::FSub && | |
1035 | TI->getOpcode() == Instruction::FAdd)) { | |
1036 | AddOp = TI; SubOp = FI; | |
1037 | } | |
1038 | ||
1039 | if (AddOp) { | |
1a4d82fc | 1040 | Value *OtherAddOp = nullptr; |
223e47cc LB |
1041 | if (SubOp->getOperand(0) == AddOp->getOperand(0)) { |
1042 | OtherAddOp = AddOp->getOperand(1); | |
1043 | } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) { | |
1044 | OtherAddOp = AddOp->getOperand(0); | |
1045 | } | |
1046 | ||
1047 | if (OtherAddOp) { | |
1048 | // So at this point we know we have (Y -> OtherAddOp): | |
1049 | // select C, (add X, Y), (sub X, Z) | |
1050 | Value *NegVal; // Compute -Z | |
1051 | if (SI.getType()->isFPOrFPVectorTy()) { | |
1052 | NegVal = Builder->CreateFNeg(SubOp->getOperand(1)); | |
1a4d82fc JJ |
1053 | if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) { |
1054 | FastMathFlags Flags = AddOp->getFastMathFlags(); | |
1055 | Flags &= SubOp->getFastMathFlags(); | |
1056 | NegInst->setFastMathFlags(Flags); | |
1057 | } | |
223e47cc LB |
1058 | } else { |
1059 | NegVal = Builder->CreateNeg(SubOp->getOperand(1)); | |
1060 | } | |
1061 | ||
1062 | Value *NewTrueOp = OtherAddOp; | |
1063 | Value *NewFalseOp = NegVal; | |
1064 | if (AddOp != TI) | |
1065 | std::swap(NewTrueOp, NewFalseOp); | |
1a4d82fc | 1066 | Value *NewSel = |
223e47cc LB |
1067 | Builder->CreateSelect(CondVal, NewTrueOp, |
1068 | NewFalseOp, SI.getName() + ".p"); | |
1069 | ||
1a4d82fc JJ |
1070 | if (SI.getType()->isFPOrFPVectorTy()) { |
1071 | Instruction *RI = | |
1072 | BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel); | |
1073 | ||
1074 | FastMathFlags Flags = AddOp->getFastMathFlags(); | |
1075 | Flags &= SubOp->getFastMathFlags(); | |
1076 | RI->setFastMathFlags(Flags); | |
1077 | return RI; | |
1078 | } else | |
223e47cc LB |
1079 | return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel); |
1080 | } | |
1081 | } | |
1082 | } | |
1083 | ||
1084 | // See if we can fold the select into one of our operands. | |
1085 | if (SI.getType()->isIntegerTy()) { | |
1086 | if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal)) | |
1087 | return FoldI; | |
1088 | ||
1089 | // MAX(MAX(a, b), a) -> MAX(a, b) | |
1090 | // MIN(MIN(a, b), a) -> MIN(a, b) | |
1091 | // MAX(MIN(a, b), a) -> a | |
1092 | // MIN(MAX(a, b), a) -> a | |
1093 | Value *LHS, *RHS, *LHS2, *RHS2; | |
1094 | if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) { | |
1095 | if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2)) | |
1a4d82fc | 1096 | if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2, |
223e47cc LB |
1097 | SI, SPF, RHS)) |
1098 | return R; | |
1099 | if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2)) | |
1100 | if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2, | |
1101 | SI, SPF, LHS)) | |
1102 | return R; | |
1103 | } | |
1104 | ||
1105 | // TODO. | |
1106 | // ABS(-X) -> ABS(X) | |
223e47cc LB |
1107 | } |
1108 | ||
1109 | // See if we can fold the select into a phi node if the condition is a select. | |
1110 | if (isa<PHINode>(SI.getCondition())) | |
1111 | // The true/false values have to be live in the PHI predecessor's blocks. | |
1112 | if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) && | |
1113 | CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI)) | |
1114 | if (Instruction *NV = FoldOpIntoPhi(SI)) | |
1115 | return NV; | |
1116 | ||
1117 | if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) { | |
1118 | if (TrueSI->getCondition() == CondVal) { | |
1119 | if (SI.getTrueValue() == TrueSI->getTrueValue()) | |
1a4d82fc | 1120 | return nullptr; |
223e47cc LB |
1121 | SI.setOperand(1, TrueSI->getTrueValue()); |
1122 | return &SI; | |
1123 | } | |
1124 | } | |
1125 | if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) { | |
1126 | if (FalseSI->getCondition() == CondVal) { | |
1127 | if (SI.getFalseValue() == FalseSI->getFalseValue()) | |
1a4d82fc | 1128 | return nullptr; |
223e47cc LB |
1129 | SI.setOperand(2, FalseSI->getFalseValue()); |
1130 | return &SI; | |
1131 | } | |
1132 | } | |
1133 | ||
1134 | if (BinaryOperator::isNot(CondVal)) { | |
1135 | SI.setOperand(0, BinaryOperator::getNotArgument(CondVal)); | |
1136 | SI.setOperand(1, FalseVal); | |
1137 | SI.setOperand(2, TrueVal); | |
1138 | return &SI; | |
1139 | } | |
1140 | ||
1a4d82fc | 1141 | if (VectorType* VecTy = dyn_cast<VectorType>(SI.getType())) { |
223e47cc LB |
1142 | unsigned VWidth = VecTy->getNumElements(); |
1143 | APInt UndefElts(VWidth, 0); | |
1144 | APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); | |
1145 | if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) { | |
1146 | if (V != &SI) | |
1147 | return ReplaceInstUsesWith(SI, V); | |
1148 | return &SI; | |
1149 | } | |
1150 | ||
223e47cc LB |
1151 | if (isa<ConstantAggregateZero>(CondVal)) { |
1152 | return ReplaceInstUsesWith(SI, FalseVal); | |
1153 | } | |
1154 | } | |
1155 | ||
1a4d82fc | 1156 | return nullptr; |
223e47cc | 1157 | } |