1 //===- InstCombineCasts.cpp -----------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the visit functions for cast operations.
12 //===----------------------------------------------------------------------===//
14 #include "InstCombine.h"
15 #include "llvm/Analysis/ConstantFolding.h"
16 #include "llvm/IR/DataLayout.h"
17 #include "llvm/Support/PatternMatch.h"
18 #include "llvm/Target/TargetLibraryInfo.h"
20 using namespace PatternMatch;
22 /// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
23 /// expression. If so, decompose it, returning some value X, such that Val is
26 static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
28 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
29 Offset = CI->getZExtValue();
31 return ConstantInt::get(Val->getType(), 0);
34 if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
35 // Cannot look past anything that might overflow.
36 OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
37 if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) {
43 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
44 if (I->getOpcode() == Instruction::Shl) {
45 // This is a value scaled by '1 << the shift amt'.
46 Scale = UINT64_C(1) << RHS->getZExtValue();
48 return I->getOperand(0);
51 if (I->getOpcode() == Instruction::Mul) {
52 // This value is scaled by 'RHS'.
53 Scale = RHS->getZExtValue();
55 return I->getOperand(0);
58 if (I->getOpcode() == Instruction::Add) {
59 // We have X+C. Check to see if we really have (X*C2)+C1,
60 // where C1 is divisible by C2.
63 DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset);
64 Offset += RHS->getZExtValue();
71 // Otherwise, we can't look past this.
77 /// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
78 /// try to eliminate the cast by moving the type information into the alloc.
79 Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
81 // This requires DataLayout to get the alloca alignment and size information.
84 PointerType *PTy = cast<PointerType>(CI.getType());
86 BuilderTy AllocaBuilder(*Builder);
87 AllocaBuilder.SetInsertPoint(AI.getParent(), &AI);
89 // Get the type really allocated and the type casted to.
90 Type *AllocElTy = AI.getAllocatedType();
91 Type *CastElTy = PTy->getElementType();
92 if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0;
94 unsigned AllocElTyAlign = DL->getABITypeAlignment(AllocElTy);
95 unsigned CastElTyAlign = DL->getABITypeAlignment(CastElTy);
96 if (CastElTyAlign < AllocElTyAlign) return 0;
98 // If the allocation has multiple uses, only promote it if we are strictly
99 // increasing the alignment of the resultant allocation. If we keep it the
100 // same, we open the door to infinite loops of various kinds.
101 if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0;
103 uint64_t AllocElTySize = DL->getTypeAllocSize(AllocElTy);
104 uint64_t CastElTySize = DL->getTypeAllocSize(CastElTy);
105 if (CastElTySize == 0 || AllocElTySize == 0) return 0;
107 // If the allocation has multiple uses, only promote it if we're not
108 // shrinking the amount of memory being allocated.
109 uint64_t AllocElTyStoreSize = DL->getTypeStoreSize(AllocElTy);
110 uint64_t CastElTyStoreSize = DL->getTypeStoreSize(CastElTy);
111 if (!AI.hasOneUse() && CastElTyStoreSize < AllocElTyStoreSize) return 0;
113 // See if we can satisfy the modulus by pulling a scale out of the array
115 unsigned ArraySizeScale;
116 uint64_t ArrayOffset;
117 Value *NumElements = // See if the array size is a decomposable linear expr.
118 DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
120 // If we can now satisfy the modulus, by using a non-1 scale, we really can
122 if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
123 (AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0;
125 unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
130 Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale);
131 // Insert before the alloca, not before the cast.
132 Amt = AllocaBuilder.CreateMul(Amt, NumElements);
135 if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
136 Value *Off = ConstantInt::get(AI.getArraySize()->getType(),
138 Amt = AllocaBuilder.CreateAdd(Amt, Off);
141 AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt);
142 New->setAlignment(AI.getAlignment());
145 // If the allocation has multiple real uses, insert a cast and change all
146 // things that used it to use the new cast. This will also hack on CI, but it
148 if (!AI.hasOneUse()) {
149 // New is the allocation instruction, pointer typed. AI is the original
150 // allocation instruction, also pointer typed. Thus, cast to use is BitCast.
151 Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast");
152 ReplaceInstUsesWith(AI, NewCast);
154 return ReplaceInstUsesWith(CI, New);
157 /// EvaluateInDifferentType - Given an expression that
158 /// CanEvaluateTruncated or CanEvaluateSExtd returns true for, actually
159 /// insert the code to evaluate the expression.
160 Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty,
162 if (Constant *C = dyn_cast<Constant>(V)) {
163 C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
164 // If we got a constantexpr back, try to simplify it with DL info.
165 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
166 C = ConstantFoldConstantExpression(CE, DL, TLI);
170 // Otherwise, it must be an instruction.
171 Instruction *I = cast<Instruction>(V);
172 Instruction *Res = 0;
173 unsigned Opc = I->getOpcode();
175 case Instruction::Add:
176 case Instruction::Sub:
177 case Instruction::Mul:
178 case Instruction::And:
179 case Instruction::Or:
180 case Instruction::Xor:
181 case Instruction::AShr:
182 case Instruction::LShr:
183 case Instruction::Shl:
184 case Instruction::UDiv:
185 case Instruction::URem: {
186 Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
187 Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
188 Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
191 case Instruction::Trunc:
192 case Instruction::ZExt:
193 case Instruction::SExt:
194 // If the source type of the cast is the type we're trying for then we can
195 // just return the source. There's no need to insert it because it is not
197 if (I->getOperand(0)->getType() == Ty)
198 return I->getOperand(0);
200 // Otherwise, must be the same type of cast, so just reinsert a new one.
201 // This also handles the case of zext(trunc(x)) -> zext(x).
202 Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty,
203 Opc == Instruction::SExt);
205 case Instruction::Select: {
206 Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
207 Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned);
208 Res = SelectInst::Create(I->getOperand(0), True, False);
211 case Instruction::PHI: {
212 PHINode *OPN = cast<PHINode>(I);
213 PHINode *NPN = PHINode::Create(Ty, OPN->getNumIncomingValues());
214 for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
215 Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned);
216 NPN->addIncoming(V, OPN->getIncomingBlock(i));
222 // TODO: Can handle more cases here.
223 llvm_unreachable("Unreachable!");
227 return InsertNewInstWith(Res, *I);
231 /// This function is a wrapper around CastInst::isEliminableCastPair. It
232 /// simply extracts arguments and returns what that function returns.
233 static Instruction::CastOps
234 isEliminableCastPair(
235 const CastInst *CI, ///< The first cast instruction
236 unsigned opcode, ///< The opcode of the second cast instruction
237 Type *DstTy, ///< The target type for the second cast instruction
238 DataLayout *DL ///< The target data for pointer size
241 Type *SrcTy = CI->getOperand(0)->getType(); // A from above
242 Type *MidTy = CI->getType(); // B from above
244 // Get the opcodes of the two Cast instructions
245 Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode());
246 Instruction::CastOps secondOp = Instruction::CastOps(opcode);
247 Type *SrcIntPtrTy = DL && SrcTy->isPtrOrPtrVectorTy() ?
248 DL->getIntPtrType(SrcTy) : 0;
249 Type *MidIntPtrTy = DL && MidTy->isPtrOrPtrVectorTy() ?
250 DL->getIntPtrType(MidTy) : 0;
251 Type *DstIntPtrTy = DL && DstTy->isPtrOrPtrVectorTy() ?
252 DL->getIntPtrType(DstTy) : 0;
253 unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
254 DstTy, SrcIntPtrTy, MidIntPtrTy,
257 // We don't want to form an inttoptr or ptrtoint that converts to an integer
258 // type that differs from the pointer size.
259 if ((Res == Instruction::IntToPtr && SrcTy != DstIntPtrTy) ||
260 (Res == Instruction::PtrToInt && DstTy != SrcIntPtrTy))
263 return Instruction::CastOps(Res);
266 /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
267 /// results in any code being generated and is interesting to optimize out. If
268 /// the cast can be eliminated by some other simple transformation, we prefer
269 /// to do the simplification first.
270 bool InstCombiner::ShouldOptimizeCast(Instruction::CastOps opc, const Value *V,
272 // Noop casts and casts of constants should be eliminated trivially.
273 if (V->getType() == Ty || isa<Constant>(V)) return false;
275 // If this is another cast that can be eliminated, we prefer to have it
277 if (const CastInst *CI = dyn_cast<CastInst>(V))
278 if (isEliminableCastPair(CI, opc, Ty, DL))
281 // If this is a vector sext from a compare, then we don't want to break the
282 // idiom where each element of the extended vector is either zero or all ones.
283 if (opc == Instruction::SExt && isa<CmpInst>(V) && Ty->isVectorTy())
290 /// @brief Implement the transforms common to all CastInst visitors.
291 Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
292 Value *Src = CI.getOperand(0);
294 // Many cases of "cast of a cast" are eliminable. If it's eliminable we just
296 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
297 if (Instruction::CastOps opc =
298 isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), DL)) {
299 // The first cast (CSrc) is eliminable so we need to fix up or replace
300 // the second cast (CI). CSrc will then have a good chance of being dead.
301 return CastInst::Create(opc, CSrc->getOperand(0), CI.getType());
305 // If we are casting a select then fold the cast into the select
306 if (SelectInst *SI = dyn_cast<SelectInst>(Src))
307 if (Instruction *NV = FoldOpIntoSelect(CI, SI))
310 // If we are casting a PHI then fold the cast into the PHI
311 if (isa<PHINode>(Src)) {
312 // We don't do this if this would create a PHI node with an illegal type if
313 // it is currently legal.
314 if (!Src->getType()->isIntegerTy() ||
315 !CI.getType()->isIntegerTy() ||
316 ShouldChangeType(CI.getType(), Src->getType()))
317 if (Instruction *NV = FoldOpIntoPhi(CI))
324 /// CanEvaluateTruncated - Return true if we can evaluate the specified
325 /// expression tree as type Ty instead of its larger type, and arrive with the
326 /// same value. This is used by code that tries to eliminate truncates.
328 /// Ty will always be a type smaller than V. We should return true if trunc(V)
329 /// can be computed by computing V in the smaller type. If V is an instruction,
330 /// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only
331 /// makes sense if x and y can be efficiently truncated.
333 /// This function works on both vectors and scalars.
335 static bool CanEvaluateTruncated(Value *V, Type *Ty) {
336 // We can always evaluate constants in another type.
337 if (isa<Constant>(V))
340 Instruction *I = dyn_cast<Instruction>(V);
341 if (!I) return false;
343 Type *OrigTy = V->getType();
345 // If this is an extension from the dest type, we can eliminate it, even if it
346 // has multiple uses.
347 if ((isa<ZExtInst>(I) || isa<SExtInst>(I)) &&
348 I->getOperand(0)->getType() == Ty)
351 // We can't extend or shrink something that has multiple uses: doing so would
352 // require duplicating the instruction in general, which isn't profitable.
353 if (!I->hasOneUse()) return false;
355 unsigned Opc = I->getOpcode();
357 case Instruction::Add:
358 case Instruction::Sub:
359 case Instruction::Mul:
360 case Instruction::And:
361 case Instruction::Or:
362 case Instruction::Xor:
363 // These operators can all arbitrarily be extended or truncated.
364 return CanEvaluateTruncated(I->getOperand(0), Ty) &&
365 CanEvaluateTruncated(I->getOperand(1), Ty);
367 case Instruction::UDiv:
368 case Instruction::URem: {
369 // UDiv and URem can be truncated if all the truncated bits are zero.
370 uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
371 uint32_t BitWidth = Ty->getScalarSizeInBits();
372 if (BitWidth < OrigBitWidth) {
373 APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth);
374 if (MaskedValueIsZero(I->getOperand(0), Mask) &&
375 MaskedValueIsZero(I->getOperand(1), Mask)) {
376 return CanEvaluateTruncated(I->getOperand(0), Ty) &&
377 CanEvaluateTruncated(I->getOperand(1), Ty);
382 case Instruction::Shl:
383 // If we are truncating the result of this SHL, and if it's a shift of a
384 // constant amount, we can always perform a SHL in a smaller type.
385 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
386 uint32_t BitWidth = Ty->getScalarSizeInBits();
387 if (CI->getLimitedValue(BitWidth) < BitWidth)
388 return CanEvaluateTruncated(I->getOperand(0), Ty);
391 case Instruction::LShr:
392 // If this is a truncate of a logical shr, we can truncate it to a smaller
393 // lshr iff we know that the bits we would otherwise be shifting in are
395 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
396 uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
397 uint32_t BitWidth = Ty->getScalarSizeInBits();
398 if (MaskedValueIsZero(I->getOperand(0),
399 APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) &&
400 CI->getLimitedValue(BitWidth) < BitWidth) {
401 return CanEvaluateTruncated(I->getOperand(0), Ty);
405 case Instruction::Trunc:
406 // trunc(trunc(x)) -> trunc(x)
408 case Instruction::ZExt:
409 case Instruction::SExt:
410 // trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest
411 // trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest
413 case Instruction::Select: {
414 SelectInst *SI = cast<SelectInst>(I);
415 return CanEvaluateTruncated(SI->getTrueValue(), Ty) &&
416 CanEvaluateTruncated(SI->getFalseValue(), Ty);
418 case Instruction::PHI: {
419 // We can change a phi if we can change all operands. Note that we never
420 // get into trouble with cyclic PHIs here because we only consider
421 // instructions with a single use.
422 PHINode *PN = cast<PHINode>(I);
423 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
424 if (!CanEvaluateTruncated(PN->getIncomingValue(i), Ty))
429 // TODO: Can handle more cases here.
436 Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
437 if (Instruction *Result = commonCastTransforms(CI))
440 // See if we can simplify any instructions used by the input whose sole
441 // purpose is to compute bits we don't care about.
442 if (SimplifyDemandedInstructionBits(CI))
445 Value *Src = CI.getOperand(0);
446 Type *DestTy = CI.getType(), *SrcTy = Src->getType();
448 // Attempt to truncate the entire input expression tree to the destination
449 // type. Only do this if the dest type is a simple type, don't convert the
450 // expression tree to something weird like i93 unless the source is also
452 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
453 CanEvaluateTruncated(Src, DestTy)) {
455 // If this cast is a truncate, evaluting in a different type always
456 // eliminates the cast, so it is always a win.
457 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
458 " to avoid cast: " << CI << '\n');
459 Value *Res = EvaluateInDifferentType(Src, DestTy, false);
460 assert(Res->getType() == DestTy);
461 return ReplaceInstUsesWith(CI, Res);
464 // Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0), likewise for vector.
465 if (DestTy->getScalarSizeInBits() == 1) {
466 Constant *One = ConstantInt::get(Src->getType(), 1);
467 Src = Builder->CreateAnd(Src, One);
468 Value *Zero = Constant::getNullValue(Src->getType());
469 return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
472 // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion.
473 Value *A = 0; ConstantInt *Cst = 0;
474 if (Src->hasOneUse() &&
475 match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) {
476 // We have three types to worry about here, the type of A, the source of
477 // the truncate (MidSize), and the destination of the truncate. We know that
478 // ASize < MidSize and MidSize > ResultSize, but don't know the relation
479 // between ASize and ResultSize.
480 unsigned ASize = A->getType()->getPrimitiveSizeInBits();
482 // If the shift amount is larger than the size of A, then the result is
483 // known to be zero because all the input bits got shifted out.
484 if (Cst->getZExtValue() >= ASize)
485 return ReplaceInstUsesWith(CI, Constant::getNullValue(CI.getType()));
487 // Since we're doing an lshr and a zero extend, and know that the shift
488 // amount is smaller than ASize, it is always safe to do the shift in A's
489 // type, then zero extend or truncate to the result.
490 Value *Shift = Builder->CreateLShr(A, Cst->getZExtValue());
491 Shift->takeName(Src);
492 return CastInst::CreateIntegerCast(Shift, CI.getType(), false);
495 // Transform "trunc (and X, cst)" -> "and (trunc X), cst" so long as the dest
496 // type isn't non-native.
497 if (Src->hasOneUse() && isa<IntegerType>(Src->getType()) &&
498 ShouldChangeType(Src->getType(), CI.getType()) &&
499 match(Src, m_And(m_Value(A), m_ConstantInt(Cst)))) {
500 Value *NewTrunc = Builder->CreateTrunc(A, CI.getType(), A->getName()+".tr");
501 return BinaryOperator::CreateAnd(NewTrunc,
502 ConstantExpr::getTrunc(Cst, CI.getType()));
508 /// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations
509 /// in order to eliminate the icmp.
510 Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI,
512 // If we are just checking for a icmp eq of a single bit and zext'ing it
513 // to an integer, then shift the bit to the appropriate place and then
514 // cast to integer to avoid the comparison.
515 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
516 const APInt &Op1CV = Op1C->getValue();
518 // zext (x <s 0) to i32 --> x>>u31 true if signbit set.
519 // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
520 if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
521 (ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) {
522 if (!DoXform) return ICI;
524 Value *In = ICI->getOperand(0);
525 Value *Sh = ConstantInt::get(In->getType(),
526 In->getType()->getScalarSizeInBits()-1);
527 In = Builder->CreateLShr(In, Sh, In->getName()+".lobit");
528 if (In->getType() != CI.getType())
529 In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/);
531 if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
532 Constant *One = ConstantInt::get(In->getType(), 1);
533 In = Builder->CreateXor(In, One, In->getName()+".not");
536 return ReplaceInstUsesWith(CI, In);
539 // zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
540 // zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
541 // zext (X == 1) to i32 --> X iff X has only the low bit set.
542 // zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set.
543 // zext (X != 0) to i32 --> X iff X has only the low bit set.
544 // zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
545 // zext (X != 1) to i32 --> X^1 iff X has only the low bit set.
546 // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
547 if ((Op1CV == 0 || Op1CV.isPowerOf2()) &&
548 // This only works for EQ and NE
550 // If Op1C some other power of two, convert:
551 uint32_t BitWidth = Op1C->getType()->getBitWidth();
552 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
553 ComputeMaskedBits(ICI->getOperand(0), KnownZero, KnownOne);
555 APInt KnownZeroMask(~KnownZero);
556 if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
557 if (!DoXform) return ICI;
559 bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
560 if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
561 // (X&4) == 2 --> false
562 // (X&4) != 2 --> true
563 Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()),
565 Res = ConstantExpr::getZExt(Res, CI.getType());
566 return ReplaceInstUsesWith(CI, Res);
569 uint32_t ShiftAmt = KnownZeroMask.logBase2();
570 Value *In = ICI->getOperand(0);
572 // Perform a logical shr by shiftamt.
573 // Insert the shift to put the result in the low bit.
574 In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt),
575 In->getName()+".lobit");
578 if ((Op1CV != 0) == isNE) { // Toggle the low bit.
579 Constant *One = ConstantInt::get(In->getType(), 1);
580 In = Builder->CreateXor(In, One);
583 if (CI.getType() == In->getType())
584 return ReplaceInstUsesWith(CI, In);
585 return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/);
590 // icmp ne A, B is equal to xor A, B when A and B only really have one bit.
591 // It is also profitable to transform icmp eq into not(xor(A, B)) because that
592 // may lead to additional simplifications.
593 if (ICI->isEquality() && CI.getType() == ICI->getOperand(0)->getType()) {
594 if (IntegerType *ITy = dyn_cast<IntegerType>(CI.getType())) {
595 uint32_t BitWidth = ITy->getBitWidth();
596 Value *LHS = ICI->getOperand(0);
597 Value *RHS = ICI->getOperand(1);
599 APInt KnownZeroLHS(BitWidth, 0), KnownOneLHS(BitWidth, 0);
600 APInt KnownZeroRHS(BitWidth, 0), KnownOneRHS(BitWidth, 0);
601 ComputeMaskedBits(LHS, KnownZeroLHS, KnownOneLHS);
602 ComputeMaskedBits(RHS, KnownZeroRHS, KnownOneRHS);
604 if (KnownZeroLHS == KnownZeroRHS && KnownOneLHS == KnownOneRHS) {
605 APInt KnownBits = KnownZeroLHS | KnownOneLHS;
606 APInt UnknownBit = ~KnownBits;
607 if (UnknownBit.countPopulation() == 1) {
608 if (!DoXform) return ICI;
610 Value *Result = Builder->CreateXor(LHS, RHS);
612 // Mask off any bits that are set and won't be shifted away.
613 if (KnownOneLHS.uge(UnknownBit))
614 Result = Builder->CreateAnd(Result,
615 ConstantInt::get(ITy, UnknownBit));
617 // Shift the bit we're testing down to the lsb.
618 Result = Builder->CreateLShr(
619 Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros()));
621 if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
622 Result = Builder->CreateXor(Result, ConstantInt::get(ITy, 1));
623 Result->takeName(ICI);
624 return ReplaceInstUsesWith(CI, Result);
633 /// CanEvaluateZExtd - Determine if the specified value can be computed in the
634 /// specified wider type and produce the same low bits. If not, return false.
636 /// If this function returns true, it can also return a non-zero number of bits
637 /// (in BitsToClear) which indicates that the value it computes is correct for
638 /// the zero extend, but that the additional BitsToClear bits need to be zero'd
639 /// out. For example, to promote something like:
641 /// %B = trunc i64 %A to i32
642 /// %C = lshr i32 %B, 8
643 /// %E = zext i32 %C to i64
645 /// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be
646 /// set to 8 to indicate that the promoted value needs to have bits 24-31
647 /// cleared in addition to bits 32-63. Since an 'and' will be generated to
648 /// clear the top bits anyway, doing this has no extra cost.
650 /// This function works on both vectors and scalars.
651 static bool CanEvaluateZExtd(Value *V, Type *Ty, unsigned &BitsToClear) {
653 if (isa<Constant>(V))
656 Instruction *I = dyn_cast<Instruction>(V);
657 if (!I) return false;
659 // If the input is a truncate from the destination type, we can trivially
661 if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty)
664 // We can't extend or shrink something that has multiple uses: doing so would
665 // require duplicating the instruction in general, which isn't profitable.
666 if (!I->hasOneUse()) return false;
668 unsigned Opc = I->getOpcode(), Tmp;
670 case Instruction::ZExt: // zext(zext(x)) -> zext(x).
671 case Instruction::SExt: // zext(sext(x)) -> sext(x).
672 case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x)
674 case Instruction::And:
675 case Instruction::Or:
676 case Instruction::Xor:
677 case Instruction::Add:
678 case Instruction::Sub:
679 case Instruction::Mul:
680 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear) ||
681 !CanEvaluateZExtd(I->getOperand(1), Ty, Tmp))
683 // These can all be promoted if neither operand has 'bits to clear'.
684 if (BitsToClear == 0 && Tmp == 0)
687 // If the operation is an AND/OR/XOR and the bits to clear are zero in the
688 // other side, BitsToClear is ok.
690 (Opc == Instruction::And || Opc == Instruction::Or ||
691 Opc == Instruction::Xor)) {
692 // We use MaskedValueIsZero here for generality, but the case we care
693 // about the most is constant RHS.
694 unsigned VSize = V->getType()->getScalarSizeInBits();
695 if (MaskedValueIsZero(I->getOperand(1),
696 APInt::getHighBitsSet(VSize, BitsToClear)))
700 // Otherwise, we don't know how to analyze this BitsToClear case yet.
703 case Instruction::Shl:
704 // We can promote shl(x, cst) if we can promote x. Since shl overwrites the
705 // upper bits we can reduce BitsToClear by the shift amount.
706 if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) {
707 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear))
709 uint64_t ShiftAmt = Amt->getZExtValue();
710 BitsToClear = ShiftAmt < BitsToClear ? BitsToClear - ShiftAmt : 0;
714 case Instruction::LShr:
715 // We can promote lshr(x, cst) if we can promote x. This requires the
716 // ultimate 'and' to clear out the high zero bits we're clearing out though.
717 if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) {
718 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear))
720 BitsToClear += Amt->getZExtValue();
721 if (BitsToClear > V->getType()->getScalarSizeInBits())
722 BitsToClear = V->getType()->getScalarSizeInBits();
725 // Cannot promote variable LSHR.
727 case Instruction::Select:
728 if (!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp) ||
729 !CanEvaluateZExtd(I->getOperand(2), Ty, BitsToClear) ||
730 // TODO: If important, we could handle the case when the BitsToClear are
731 // known zero in the disagreeing side.
736 case Instruction::PHI: {
737 // We can change a phi if we can change all operands. Note that we never
738 // get into trouble with cyclic PHIs here because we only consider
739 // instructions with a single use.
740 PHINode *PN = cast<PHINode>(I);
741 if (!CanEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear))
743 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
744 if (!CanEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp) ||
745 // TODO: If important, we could handle the case when the BitsToClear
746 // are known zero in the disagreeing input.
752 // TODO: Can handle more cases here.
757 Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
758 // If this zero extend is only used by a truncate, let the truncate be
759 // eliminated before we try to optimize this zext.
760 if (CI.hasOneUse() && isa<TruncInst>(CI.use_back()))
763 // If one of the common conversion will work, do it.
764 if (Instruction *Result = commonCastTransforms(CI))
767 // See if we can simplify any instructions used by the input whose sole
768 // purpose is to compute bits we don't care about.
769 if (SimplifyDemandedInstructionBits(CI))
772 Value *Src = CI.getOperand(0);
773 Type *SrcTy = Src->getType(), *DestTy = CI.getType();
775 // Attempt to extend the entire input expression tree to the destination
776 // type. Only do this if the dest type is a simple type, don't convert the
777 // expression tree to something weird like i93 unless the source is also
779 unsigned BitsToClear;
780 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
781 CanEvaluateZExtd(Src, DestTy, BitsToClear)) {
782 assert(BitsToClear < SrcTy->getScalarSizeInBits() &&
783 "Unreasonable BitsToClear");
785 // Okay, we can transform this! Insert the new expression now.
786 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
787 " to avoid zero extend: " << CI);
788 Value *Res = EvaluateInDifferentType(Src, DestTy, false);
789 assert(Res->getType() == DestTy);
791 uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear;
792 uint32_t DestBitSize = DestTy->getScalarSizeInBits();
794 // If the high bits are already filled with zeros, just replace this
795 // cast with the result.
796 if (MaskedValueIsZero(Res, APInt::getHighBitsSet(DestBitSize,
797 DestBitSize-SrcBitsKept)))
798 return ReplaceInstUsesWith(CI, Res);
800 // We need to emit an AND to clear the high bits.
801 Constant *C = ConstantInt::get(Res->getType(),
802 APInt::getLowBitsSet(DestBitSize, SrcBitsKept));
803 return BinaryOperator::CreateAnd(Res, C);
806 // If this is a TRUNC followed by a ZEXT then we are dealing with integral
807 // types and if the sizes are just right we can convert this into a logical
808 // 'and' which will be much cheaper than the pair of casts.
809 if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast
810 // TODO: Subsume this into EvaluateInDifferentType.
812 // Get the sizes of the types involved. We know that the intermediate type
813 // will be smaller than A or C, but don't know the relation between A and C.
814 Value *A = CSrc->getOperand(0);
815 unsigned SrcSize = A->getType()->getScalarSizeInBits();
816 unsigned MidSize = CSrc->getType()->getScalarSizeInBits();
817 unsigned DstSize = CI.getType()->getScalarSizeInBits();
818 // If we're actually extending zero bits, then if
819 // SrcSize < DstSize: zext(a & mask)
820 // SrcSize == DstSize: a & mask
821 // SrcSize > DstSize: trunc(a) & mask
822 if (SrcSize < DstSize) {
823 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
824 Constant *AndConst = ConstantInt::get(A->getType(), AndValue);
825 Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask");
826 return new ZExtInst(And, CI.getType());
829 if (SrcSize == DstSize) {
830 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
831 return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(),
834 if (SrcSize > DstSize) {
835 Value *Trunc = Builder->CreateTrunc(A, CI.getType());
836 APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize));
837 return BinaryOperator::CreateAnd(Trunc,
838 ConstantInt::get(Trunc->getType(),
843 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
844 return transformZExtICmp(ICI, CI);
846 BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src);
847 if (SrcI && SrcI->getOpcode() == Instruction::Or) {
848 // zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one
849 // of the (zext icmp) will be transformed.
850 ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0));
851 ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1));
852 if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() &&
853 (transformZExtICmp(LHS, CI, false) ||
854 transformZExtICmp(RHS, CI, false))) {
855 Value *LCast = Builder->CreateZExt(LHS, CI.getType(), LHS->getName());
856 Value *RCast = Builder->CreateZExt(RHS, CI.getType(), RHS->getName());
857 return BinaryOperator::Create(Instruction::Or, LCast, RCast);
861 // zext(trunc(X) & C) -> (X & zext(C)).
865 match(SrcI, m_OneUse(m_And(m_Trunc(m_Value(X)), m_Constant(C)))) &&
866 X->getType() == CI.getType())
867 return BinaryOperator::CreateAnd(X, ConstantExpr::getZExt(C, CI.getType()));
869 // zext((trunc(X) & C) ^ C) -> ((X & zext(C)) ^ zext(C)).
871 if (SrcI && match(SrcI, m_OneUse(m_Xor(m_Value(And), m_Constant(C)))) &&
872 match(And, m_OneUse(m_And(m_Trunc(m_Value(X)), m_Specific(C)))) &&
873 X->getType() == CI.getType()) {
874 Constant *ZC = ConstantExpr::getZExt(C, CI.getType());
875 return BinaryOperator::CreateXor(Builder->CreateAnd(X, ZC), ZC);
878 // zext (xor i1 X, true) to i32 --> xor (zext i1 X to i32), 1
879 if (SrcI && SrcI->hasOneUse() &&
880 SrcI->getType()->getScalarType()->isIntegerTy(1) &&
881 match(SrcI, m_Not(m_Value(X))) && (!X->hasOneUse() || !isa<CmpInst>(X))) {
882 Value *New = Builder->CreateZExt(X, CI.getType());
883 return BinaryOperator::CreateXor(New, ConstantInt::get(CI.getType(), 1));
889 /// transformSExtICmp - Transform (sext icmp) to bitwise / integer operations
890 /// in order to eliminate the icmp.
891 Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) {
892 Value *Op0 = ICI->getOperand(0), *Op1 = ICI->getOperand(1);
893 ICmpInst::Predicate Pred = ICI->getPredicate();
895 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
896 // (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if negative
897 // (x >s -1) ? -1 : 0 -> not (ashr x, 31) -> all ones if positive
898 if ((Pred == ICmpInst::ICMP_SLT && Op1C->isNullValue()) ||
899 (Pred == ICmpInst::ICMP_SGT && Op1C->isAllOnesValue())) {
901 Value *Sh = ConstantInt::get(Op0->getType(),
902 Op0->getType()->getScalarSizeInBits()-1);
903 Value *In = Builder->CreateAShr(Op0, Sh, Op0->getName()+".lobit");
904 if (In->getType() != CI.getType())
905 In = Builder->CreateIntCast(In, CI.getType(), true/*SExt*/);
907 if (Pred == ICmpInst::ICMP_SGT)
908 In = Builder->CreateNot(In, In->getName()+".not");
909 return ReplaceInstUsesWith(CI, In);
913 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
914 // If we know that only one bit of the LHS of the icmp can be set and we
915 // have an equality comparison with zero or a power of 2, we can transform
916 // the icmp and sext into bitwise/integer operations.
917 if (ICI->hasOneUse() &&
918 ICI->isEquality() && (Op1C->isZero() || Op1C->getValue().isPowerOf2())){
919 unsigned BitWidth = Op1C->getType()->getBitWidth();
920 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
921 ComputeMaskedBits(Op0, KnownZero, KnownOne);
923 APInt KnownZeroMask(~KnownZero);
924 if (KnownZeroMask.isPowerOf2()) {
925 Value *In = ICI->getOperand(0);
927 // If the icmp tests for a known zero bit we can constant fold it.
928 if (!Op1C->isZero() && Op1C->getValue() != KnownZeroMask) {
929 Value *V = Pred == ICmpInst::ICMP_NE ?
930 ConstantInt::getAllOnesValue(CI.getType()) :
931 ConstantInt::getNullValue(CI.getType());
932 return ReplaceInstUsesWith(CI, V);
935 if (!Op1C->isZero() == (Pred == ICmpInst::ICMP_NE)) {
936 // sext ((x & 2^n) == 0) -> (x >> n) - 1
937 // sext ((x & 2^n) != 2^n) -> (x >> n) - 1
938 unsigned ShiftAmt = KnownZeroMask.countTrailingZeros();
939 // Perform a right shift to place the desired bit in the LSB.
941 In = Builder->CreateLShr(In,
942 ConstantInt::get(In->getType(), ShiftAmt));
944 // At this point "In" is either 1 or 0. Subtract 1 to turn
945 // {1, 0} -> {0, -1}.
946 In = Builder->CreateAdd(In,
947 ConstantInt::getAllOnesValue(In->getType()),
950 // sext ((x & 2^n) != 0) -> (x << bitwidth-n) a>> bitwidth-1
951 // sext ((x & 2^n) == 2^n) -> (x << bitwidth-n) a>> bitwidth-1
952 unsigned ShiftAmt = KnownZeroMask.countLeadingZeros();
953 // Perform a left shift to place the desired bit in the MSB.
955 In = Builder->CreateShl(In,
956 ConstantInt::get(In->getType(), ShiftAmt));
958 // Distribute the bit over the whole bit width.
959 In = Builder->CreateAShr(In, ConstantInt::get(In->getType(),
960 BitWidth - 1), "sext");
963 if (CI.getType() == In->getType())
964 return ReplaceInstUsesWith(CI, In);
965 return CastInst::CreateIntegerCast(In, CI.getType(), true/*SExt*/);
973 /// CanEvaluateSExtd - Return true if we can take the specified value
974 /// and return it as type Ty without inserting any new casts and without
975 /// changing the value of the common low bits. This is used by code that tries
976 /// to promote integer operations to a wider types will allow us to eliminate
979 /// This function works on both vectors and scalars.
981 static bool CanEvaluateSExtd(Value *V, Type *Ty) {
982 assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() &&
983 "Can't sign extend type to a smaller type");
984 // If this is a constant, it can be trivially promoted.
985 if (isa<Constant>(V))
988 Instruction *I = dyn_cast<Instruction>(V);
989 if (!I) return false;
991 // If this is a truncate from the dest type, we can trivially eliminate it.
992 if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty)
995 // We can't extend or shrink something that has multiple uses: doing so would
996 // require duplicating the instruction in general, which isn't profitable.
997 if (!I->hasOneUse()) return false;
999 switch (I->getOpcode()) {
1000 case Instruction::SExt: // sext(sext(x)) -> sext(x)
1001 case Instruction::ZExt: // sext(zext(x)) -> zext(x)
1002 case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x)
1004 case Instruction::And:
1005 case Instruction::Or:
1006 case Instruction::Xor:
1007 case Instruction::Add:
1008 case Instruction::Sub:
1009 case Instruction::Mul:
1010 // These operators can all arbitrarily be extended if their inputs can.
1011 return CanEvaluateSExtd(I->getOperand(0), Ty) &&
1012 CanEvaluateSExtd(I->getOperand(1), Ty);
1014 //case Instruction::Shl: TODO
1015 //case Instruction::LShr: TODO
1017 case Instruction::Select:
1018 return CanEvaluateSExtd(I->getOperand(1), Ty) &&
1019 CanEvaluateSExtd(I->getOperand(2), Ty);
1021 case Instruction::PHI: {
1022 // We can change a phi if we can change all operands. Note that we never
1023 // get into trouble with cyclic PHIs here because we only consider
1024 // instructions with a single use.
1025 PHINode *PN = cast<PHINode>(I);
1026 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1027 if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty)) return false;
1031 // TODO: Can handle more cases here.
1038 Instruction *InstCombiner::visitSExt(SExtInst &CI) {
1039 // If this sign extend is only used by a truncate, let the truncate be
1040 // eliminated before we try to optimize this sext.
1041 if (CI.hasOneUse() && isa<TruncInst>(CI.use_back()))
1044 if (Instruction *I = commonCastTransforms(CI))
1047 // See if we can simplify any instructions used by the input whose sole
1048 // purpose is to compute bits we don't care about.
1049 if (SimplifyDemandedInstructionBits(CI))
1052 Value *Src = CI.getOperand(0);
1053 Type *SrcTy = Src->getType(), *DestTy = CI.getType();
1055 // Attempt to extend the entire input expression tree to the destination
1056 // type. Only do this if the dest type is a simple type, don't convert the
1057 // expression tree to something weird like i93 unless the source is also
1059 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
1060 CanEvaluateSExtd(Src, DestTy)) {
1061 // Okay, we can transform this! Insert the new expression now.
1062 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
1063 " to avoid sign extend: " << CI);
1064 Value *Res = EvaluateInDifferentType(Src, DestTy, true);
1065 assert(Res->getType() == DestTy);
1067 uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
1068 uint32_t DestBitSize = DestTy->getScalarSizeInBits();
1070 // If the high bits are already filled with sign bit, just replace this
1071 // cast with the result.
1072 if (ComputeNumSignBits(Res) > DestBitSize - SrcBitSize)
1073 return ReplaceInstUsesWith(CI, Res);
1075 // We need to emit a shl + ashr to do the sign extend.
1076 Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
1077 return BinaryOperator::CreateAShr(Builder->CreateShl(Res, ShAmt, "sext"),
1081 // If this input is a trunc from our destination, then turn sext(trunc(x))
1083 if (TruncInst *TI = dyn_cast<TruncInst>(Src))
1084 if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) {
1085 uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
1086 uint32_t DestBitSize = DestTy->getScalarSizeInBits();
1088 // We need to emit a shl + ashr to do the sign extend.
1089 Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
1090 Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext");
1091 return BinaryOperator::CreateAShr(Res, ShAmt);
1094 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
1095 return transformSExtICmp(ICI, CI);
1097 // If the input is a shl/ashr pair of a same constant, then this is a sign
1098 // extension from a smaller value. If we could trust arbitrary bitwidth
1099 // integers, we could turn this into a truncate to the smaller bit and then
1100 // use a sext for the whole extension. Since we don't, look deeper and check
1101 // for a truncate. If the source and dest are the same type, eliminate the
1102 // trunc and extend and just do shifts. For example, turn:
1103 // %a = trunc i32 %i to i8
1104 // %b = shl i8 %a, 6
1105 // %c = ashr i8 %b, 6
1106 // %d = sext i8 %c to i32
1108 // %a = shl i32 %i, 30
1109 // %d = ashr i32 %a, 30
1111 // TODO: Eventually this could be subsumed by EvaluateInDifferentType.
1112 ConstantInt *BA = 0, *CA = 0;
1113 if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)),
1114 m_ConstantInt(CA))) &&
1115 BA == CA && A->getType() == CI.getType()) {
1116 unsigned MidSize = Src->getType()->getScalarSizeInBits();
1117 unsigned SrcDstSize = CI.getType()->getScalarSizeInBits();
1118 unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize;
1119 Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt);
1120 A = Builder->CreateShl(A, ShAmtV, CI.getName());
1121 return BinaryOperator::CreateAShr(A, ShAmtV);
1128 /// FitsInFPType - Return a Constant* for the specified FP constant if it fits
1129 /// in the specified FP type without changing its value.
1130 static Constant *FitsInFPType(ConstantFP *CFP, const fltSemantics &Sem) {
1132 APFloat F = CFP->getValueAPF();
1133 (void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo);
1135 return ConstantFP::get(CFP->getContext(), F);
1139 /// LookThroughFPExtensions - If this is an fp extension instruction, look
1140 /// through it until we get the source value.
1141 static Value *LookThroughFPExtensions(Value *V) {
1142 if (Instruction *I = dyn_cast<Instruction>(V))
1143 if (I->getOpcode() == Instruction::FPExt)
1144 return LookThroughFPExtensions(I->getOperand(0));
1146 // If this value is a constant, return the constant in the smallest FP type
1147 // that can accurately represent it. This allows us to turn
1148 // (float)((double)X+2.0) into x+2.0f.
1149 if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
1150 if (CFP->getType() == Type::getPPC_FP128Ty(V->getContext()))
1151 return V; // No constant folding of this.
1152 // See if the value can be truncated to half and then reextended.
1153 if (Value *V = FitsInFPType(CFP, APFloat::IEEEhalf))
1155 // See if the value can be truncated to float and then reextended.
1156 if (Value *V = FitsInFPType(CFP, APFloat::IEEEsingle))
1158 if (CFP->getType()->isDoubleTy())
1159 return V; // Won't shrink.
1160 if (Value *V = FitsInFPType(CFP, APFloat::IEEEdouble))
1162 // Don't try to shrink to various long double types.
1168 Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
1169 if (Instruction *I = commonCastTransforms(CI))
1171 // If we have fptrunc(OpI (fpextend x), (fpextend y)), we would like to
1172 // simpilify this expression to avoid one or more of the trunc/extend
1173 // operations if we can do so without changing the numerical results.
1175 // The exact manner in which the widths of the operands interact to limit
1176 // what we can and cannot do safely varies from operation to operation, and
1177 // is explained below in the various case statements.
1178 BinaryOperator *OpI = dyn_cast<BinaryOperator>(CI.getOperand(0));
1179 if (OpI && OpI->hasOneUse()) {
1180 Value *LHSOrig = LookThroughFPExtensions(OpI->getOperand(0));
1181 Value *RHSOrig = LookThroughFPExtensions(OpI->getOperand(1));
1182 unsigned OpWidth = OpI->getType()->getFPMantissaWidth();
1183 unsigned LHSWidth = LHSOrig->getType()->getFPMantissaWidth();
1184 unsigned RHSWidth = RHSOrig->getType()->getFPMantissaWidth();
1185 unsigned SrcWidth = std::max(LHSWidth, RHSWidth);
1186 unsigned DstWidth = CI.getType()->getFPMantissaWidth();
1187 switch (OpI->getOpcode()) {
1189 case Instruction::FAdd:
1190 case Instruction::FSub:
1191 // For addition and subtraction, the infinitely precise result can
1192 // essentially be arbitrarily wide; proving that double rounding
1193 // will not occur because the result of OpI is exact (as we will for
1194 // FMul, for example) is hopeless. However, we *can* nonetheless
1195 // frequently know that double rounding cannot occur (or that it is
1196 // innocuous) by taking advantage of the specific structure of
1197 // infinitely-precise results that admit double rounding.
1199 // Specifically, if OpWidth >= 2*DstWdith+1 and DstWidth is sufficient
1200 // to represent both sources, we can guarantee that the double
1201 // rounding is innocuous (See p50 of Figueroa's 2000 PhD thesis,
1202 // "A Rigorous Framework for Fully Supporting the IEEE Standard ..."
1203 // for proof of this fact).
1205 // Note: Figueroa does not consider the case where DstFormat !=
1206 // SrcFormat. It's possible (likely even!) that this analysis
1207 // could be tightened for those cases, but they are rare (the main
1208 // case of interest here is (float)((double)float + float)).
1209 if (OpWidth >= 2*DstWidth+1 && DstWidth >= SrcWidth) {
1210 if (LHSOrig->getType() != CI.getType())
1211 LHSOrig = Builder->CreateFPExt(LHSOrig, CI.getType());
1212 if (RHSOrig->getType() != CI.getType())
1213 RHSOrig = Builder->CreateFPExt(RHSOrig, CI.getType());
1215 BinaryOperator::Create(OpI->getOpcode(), LHSOrig, RHSOrig);
1216 RI->copyFastMathFlags(OpI);
1220 case Instruction::FMul:
1221 // For multiplication, the infinitely precise result has at most
1222 // LHSWidth + RHSWidth significant bits; if OpWidth is sufficient
1223 // that such a value can be exactly represented, then no double
1224 // rounding can possibly occur; we can safely perform the operation
1225 // in the destination format if it can represent both sources.
1226 if (OpWidth >= LHSWidth + RHSWidth && DstWidth >= SrcWidth) {
1227 if (LHSOrig->getType() != CI.getType())
1228 LHSOrig = Builder->CreateFPExt(LHSOrig, CI.getType());
1229 if (RHSOrig->getType() != CI.getType())
1230 RHSOrig = Builder->CreateFPExt(RHSOrig, CI.getType());
1232 BinaryOperator::CreateFMul(LHSOrig, RHSOrig);
1233 RI->copyFastMathFlags(OpI);
1237 case Instruction::FDiv:
1238 // For division, we use again use the bound from Figueroa's
1239 // dissertation. I am entirely certain that this bound can be
1240 // tightened in the unbalanced operand case by an analysis based on
1241 // the diophantine rational approximation bound, but the well-known
1242 // condition used here is a good conservative first pass.
1243 // TODO: Tighten bound via rigorous analysis of the unbalanced case.
1244 if (OpWidth >= 2*DstWidth && DstWidth >= SrcWidth) {
1245 if (LHSOrig->getType() != CI.getType())
1246 LHSOrig = Builder->CreateFPExt(LHSOrig, CI.getType());
1247 if (RHSOrig->getType() != CI.getType())
1248 RHSOrig = Builder->CreateFPExt(RHSOrig, CI.getType());
1250 BinaryOperator::CreateFDiv(LHSOrig, RHSOrig);
1251 RI->copyFastMathFlags(OpI);
1255 case Instruction::FRem:
1256 // Remainder is straightforward. Remainder is always exact, so the
1257 // type of OpI doesn't enter into things at all. We simply evaluate
1258 // in whichever source type is larger, then convert to the
1259 // destination type.
1260 if (LHSWidth < SrcWidth)
1261 LHSOrig = Builder->CreateFPExt(LHSOrig, RHSOrig->getType());
1262 else if (RHSWidth <= SrcWidth)
1263 RHSOrig = Builder->CreateFPExt(RHSOrig, LHSOrig->getType());
1264 Value *ExactResult = Builder->CreateFRem(LHSOrig, RHSOrig);
1265 if (Instruction *RI = dyn_cast<Instruction>(ExactResult))
1266 RI->copyFastMathFlags(OpI);
1267 return CastInst::CreateFPCast(ExactResult, CI.getType());
1270 // (fptrunc (fneg x)) -> (fneg (fptrunc x))
1271 if (BinaryOperator::isFNeg(OpI)) {
1272 Value *InnerTrunc = Builder->CreateFPTrunc(OpI->getOperand(1),
1274 Instruction *RI = BinaryOperator::CreateFNeg(InnerTrunc);
1275 RI->copyFastMathFlags(OpI);
1280 // (fptrunc (select cond, R1, Cst)) -->
1281 // (select cond, (fptrunc R1), (fptrunc Cst))
1282 SelectInst *SI = dyn_cast<SelectInst>(CI.getOperand(0));
1284 (isa<ConstantFP>(SI->getOperand(1)) ||
1285 isa<ConstantFP>(SI->getOperand(2)))) {
1286 Value *LHSTrunc = Builder->CreateFPTrunc(SI->getOperand(1),
1288 Value *RHSTrunc = Builder->CreateFPTrunc(SI->getOperand(2),
1290 return SelectInst::Create(SI->getOperand(0), LHSTrunc, RHSTrunc);
1293 IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI.getOperand(0));
1295 switch (II->getIntrinsicID()) {
1297 case Intrinsic::fabs: {
1298 // (fptrunc (fabs x)) -> (fabs (fptrunc x))
1299 Value *InnerTrunc = Builder->CreateFPTrunc(II->getArgOperand(0),
1301 Type *IntrinsicType[] = { CI.getType() };
1302 Function *Overload =
1303 Intrinsic::getDeclaration(CI.getParent()->getParent()->getParent(),
1304 II->getIntrinsicID(), IntrinsicType);
1306 Value *Args[] = { InnerTrunc };
1307 return CallInst::Create(Overload, Args, II->getName());
1312 // Fold (fptrunc (sqrt (fpext x))) -> (sqrtf x)
1313 // Note that we restrict this transformation based on
1314 // TLI->has(LibFunc::sqrtf), even for the sqrt intrinsic, because
1315 // TLI->has(LibFunc::sqrtf) is sufficient to guarantee that the
1316 // single-precision intrinsic can be expanded in the backend.
1317 CallInst *Call = dyn_cast<CallInst>(CI.getOperand(0));
1318 if (Call && Call->getCalledFunction() && TLI->has(LibFunc::sqrtf) &&
1319 (Call->getCalledFunction()->getName() == TLI->getName(LibFunc::sqrt) ||
1320 Call->getCalledFunction()->getIntrinsicID() == Intrinsic::sqrt) &&
1321 Call->getNumArgOperands() == 1 &&
1322 Call->hasOneUse()) {
1323 CastInst *Arg = dyn_cast<CastInst>(Call->getArgOperand(0));
1324 if (Arg && Arg->getOpcode() == Instruction::FPExt &&
1325 CI.getType()->isFloatTy() &&
1326 Call->getType()->isDoubleTy() &&
1327 Arg->getType()->isDoubleTy() &&
1328 Arg->getOperand(0)->getType()->isFloatTy()) {
1329 Function *Callee = Call->getCalledFunction();
1330 Module *M = CI.getParent()->getParent()->getParent();
1331 Constant *SqrtfFunc = (Callee->getIntrinsicID() == Intrinsic::sqrt) ?
1332 Intrinsic::getDeclaration(M, Intrinsic::sqrt, Builder->getFloatTy()) :
1333 M->getOrInsertFunction("sqrtf", Callee->getAttributes(),
1334 Builder->getFloatTy(), Builder->getFloatTy(),
1336 CallInst *ret = CallInst::Create(SqrtfFunc, Arg->getOperand(0),
1338 ret->setAttributes(Callee->getAttributes());
1341 // Remove the old Call. With -fmath-errno, it won't get marked readnone.
1342 ReplaceInstUsesWith(*Call, UndefValue::get(Call->getType()));
1343 EraseInstFromFunction(*Call);
1351 Instruction *InstCombiner::visitFPExt(CastInst &CI) {
1352 return commonCastTransforms(CI);
1355 Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) {
1356 Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
1358 return commonCastTransforms(FI);
1360 // fptoui(uitofp(X)) --> X
1361 // fptoui(sitofp(X)) --> X
1362 // This is safe if the intermediate type has enough bits in its mantissa to
1363 // accurately represent all values of X. For example, do not do this with
1364 // i64->float->i64. This is also safe for sitofp case, because any negative
1365 // 'X' value would cause an undefined result for the fptoui.
1366 if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) &&
1367 OpI->getOperand(0)->getType() == FI.getType() &&
1368 (int)FI.getType()->getScalarSizeInBits() < /*extra bit for sign */
1369 OpI->getType()->getFPMantissaWidth())
1370 return ReplaceInstUsesWith(FI, OpI->getOperand(0));
1372 return commonCastTransforms(FI);
1375 Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) {
1376 Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
1378 return commonCastTransforms(FI);
1380 // fptosi(sitofp(X)) --> X
1381 // fptosi(uitofp(X)) --> X
1382 // This is safe if the intermediate type has enough bits in its mantissa to
1383 // accurately represent all values of X. For example, do not do this with
1384 // i64->float->i64. This is also safe for sitofp case, because any negative
1385 // 'X' value would cause an undefined result for the fptoui.
1386 if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) &&
1387 OpI->getOperand(0)->getType() == FI.getType() &&
1388 (int)FI.getType()->getScalarSizeInBits() <=
1389 OpI->getType()->getFPMantissaWidth())
1390 return ReplaceInstUsesWith(FI, OpI->getOperand(0));
1392 return commonCastTransforms(FI);
1395 Instruction *InstCombiner::visitUIToFP(CastInst &CI) {
1396 return commonCastTransforms(CI);
1399 Instruction *InstCombiner::visitSIToFP(CastInst &CI) {
1400 return commonCastTransforms(CI);
1403 Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
1404 // If the source integer type is not the intptr_t type for this target, do a
1405 // trunc or zext to the intptr_t type, then inttoptr of it. This allows the
1406 // cast to be exposed to other transforms.
1409 unsigned AS = CI.getAddressSpace();
1410 if (CI.getOperand(0)->getType()->getScalarSizeInBits() !=
1411 DL->getPointerSizeInBits(AS)) {
1412 Type *Ty = DL->getIntPtrType(CI.getContext(), AS);
1413 if (CI.getType()->isVectorTy()) // Handle vectors of pointers.
1414 Ty = VectorType::get(Ty, CI.getType()->getVectorNumElements());
1416 Value *P = Builder->CreateZExtOrTrunc(CI.getOperand(0), Ty);
1417 return new IntToPtrInst(P, CI.getType());
1421 if (Instruction *I = commonCastTransforms(CI))
1427 /// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint)
1428 Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
1429 Value *Src = CI.getOperand(0);
1431 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1432 // If casting the result of a getelementptr instruction with no offset, turn
1433 // this into a cast of the original pointer!
1434 if (GEP->hasAllZeroIndices()) {
1435 // Changing the cast operand is usually not a good idea but it is safe
1436 // here because the pointer operand is being replaced with another
1437 // pointer operand so the opcode doesn't need to change.
1439 CI.setOperand(0, GEP->getOperand(0));
1444 return commonCastTransforms(CI);
1446 // If the GEP has a single use, and the base pointer is a bitcast, and the
1447 // GEP computes a constant offset, see if we can convert these three
1448 // instructions into fewer. This typically happens with unions and other
1449 // non-type-safe code.
1450 unsigned AS = GEP->getPointerAddressSpace();
1451 unsigned OffsetBits = DL->getPointerSizeInBits(AS);
1452 APInt Offset(OffsetBits, 0);
1453 BitCastInst *BCI = dyn_cast<BitCastInst>(GEP->getOperand(0));
1454 if (GEP->hasOneUse() &&
1456 GEP->accumulateConstantOffset(*DL, Offset)) {
1457 // Get the base pointer input of the bitcast, and the type it points to.
1458 Value *OrigBase = BCI->getOperand(0);
1459 SmallVector<Value*, 8> NewIndices;
1460 if (FindElementAtOffset(OrigBase->getType(),
1461 Offset.getSExtValue(),
1463 // If we were able to index down into an element, create the GEP
1464 // and bitcast the result. This eliminates one bitcast, potentially
1466 Value *NGEP = cast<GEPOperator>(GEP)->isInBounds() ?
1467 Builder->CreateInBoundsGEP(OrigBase, NewIndices) :
1468 Builder->CreateGEP(OrigBase, NewIndices);
1469 NGEP->takeName(GEP);
1471 if (isa<BitCastInst>(CI))
1472 return new BitCastInst(NGEP, CI.getType());
1473 assert(isa<PtrToIntInst>(CI));
1474 return new PtrToIntInst(NGEP, CI.getType());
1479 return commonCastTransforms(CI);
1482 Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) {
1483 // If the destination integer type is not the intptr_t type for this target,
1484 // do a ptrtoint to intptr_t then do a trunc or zext. This allows the cast
1485 // to be exposed to other transforms.
1488 return commonPointerCastTransforms(CI);
1490 Type *Ty = CI.getType();
1491 unsigned AS = CI.getPointerAddressSpace();
1493 if (Ty->getScalarSizeInBits() == DL->getPointerSizeInBits(AS))
1494 return commonPointerCastTransforms(CI);
1496 Type *PtrTy = DL->getIntPtrType(CI.getContext(), AS);
1497 if (Ty->isVectorTy()) // Handle vectors of pointers.
1498 PtrTy = VectorType::get(PtrTy, Ty->getVectorNumElements());
1500 Value *P = Builder->CreatePtrToInt(CI.getOperand(0), PtrTy);
1501 return CastInst::CreateIntegerCast(P, Ty, /*isSigned=*/false);
1504 /// OptimizeVectorResize - This input value (which is known to have vector type)
1505 /// is being zero extended or truncated to the specified vector type. Try to
1506 /// replace it with a shuffle (and vector/vector bitcast) if possible.
1508 /// The source and destination vector types may have different element types.
1509 static Instruction *OptimizeVectorResize(Value *InVal, VectorType *DestTy,
1511 // We can only do this optimization if the output is a multiple of the input
1512 // element size, or the input is a multiple of the output element size.
1513 // Convert the input type to have the same element type as the output.
1514 VectorType *SrcTy = cast<VectorType>(InVal->getType());
1516 if (SrcTy->getElementType() != DestTy->getElementType()) {
1517 // The input types don't need to be identical, but for now they must be the
1518 // same size. There is no specific reason we couldn't handle things like
1519 // <4 x i16> -> <4 x i32> by bitcasting to <2 x i32> but haven't gotten
1521 if (SrcTy->getElementType()->getPrimitiveSizeInBits() !=
1522 DestTy->getElementType()->getPrimitiveSizeInBits())
1525 SrcTy = VectorType::get(DestTy->getElementType(), SrcTy->getNumElements());
1526 InVal = IC.Builder->CreateBitCast(InVal, SrcTy);
1529 // Now that the element types match, get the shuffle mask and RHS of the
1530 // shuffle to use, which depends on whether we're increasing or decreasing the
1531 // size of the input.
1532 SmallVector<uint32_t, 16> ShuffleMask;
1535 if (SrcTy->getNumElements() > DestTy->getNumElements()) {
1536 // If we're shrinking the number of elements, just shuffle in the low
1537 // elements from the input and use undef as the second shuffle input.
1538 V2 = UndefValue::get(SrcTy);
1539 for (unsigned i = 0, e = DestTy->getNumElements(); i != e; ++i)
1540 ShuffleMask.push_back(i);
1543 // If we're increasing the number of elements, shuffle in all of the
1544 // elements from InVal and fill the rest of the result elements with zeros
1545 // from a constant zero.
1546 V2 = Constant::getNullValue(SrcTy);
1547 unsigned SrcElts = SrcTy->getNumElements();
1548 for (unsigned i = 0, e = SrcElts; i != e; ++i)
1549 ShuffleMask.push_back(i);
1551 // The excess elements reference the first element of the zero input.
1552 for (unsigned i = 0, e = DestTy->getNumElements()-SrcElts; i != e; ++i)
1553 ShuffleMask.push_back(SrcElts);
1556 return new ShuffleVectorInst(InVal, V2,
1557 ConstantDataVector::get(V2->getContext(),
1561 static bool isMultipleOfTypeSize(unsigned Value, Type *Ty) {
1562 return Value % Ty->getPrimitiveSizeInBits() == 0;
1565 static unsigned getTypeSizeIndex(unsigned Value, Type *Ty) {
1566 return Value / Ty->getPrimitiveSizeInBits();
1569 /// CollectInsertionElements - V is a value which is inserted into a vector of
1570 /// VecEltTy. Look through the value to see if we can decompose it into
1571 /// insertions into the vector. See the example in the comment for
1572 /// OptimizeIntegerToVectorInsertions for the pattern this handles.
1573 /// The type of V is always a non-zero multiple of VecEltTy's size.
1574 /// Shift is the number of bits between the lsb of V and the lsb of
1577 /// This returns false if the pattern can't be matched or true if it can,
1578 /// filling in Elements with the elements found here.
1579 static bool CollectInsertionElements(Value *V, unsigned Shift,
1580 SmallVectorImpl<Value*> &Elements,
1581 Type *VecEltTy, InstCombiner &IC) {
1582 assert(isMultipleOfTypeSize(Shift, VecEltTy) &&
1583 "Shift should be a multiple of the element type size");
1585 // Undef values never contribute useful bits to the result.
1586 if (isa<UndefValue>(V)) return true;
1588 // If we got down to a value of the right type, we win, try inserting into the
1590 if (V->getType() == VecEltTy) {
1591 // Inserting null doesn't actually insert any elements.
1592 if (Constant *C = dyn_cast<Constant>(V))
1593 if (C->isNullValue())
1596 unsigned ElementIndex = getTypeSizeIndex(Shift, VecEltTy);
1597 if (IC.getDataLayout()->isBigEndian())
1598 ElementIndex = Elements.size() - ElementIndex - 1;
1600 // Fail if multiple elements are inserted into this slot.
1601 if (Elements[ElementIndex] != 0)
1604 Elements[ElementIndex] = V;
1608 if (Constant *C = dyn_cast<Constant>(V)) {
1609 // Figure out the # elements this provides, and bitcast it or slice it up
1611 unsigned NumElts = getTypeSizeIndex(C->getType()->getPrimitiveSizeInBits(),
1613 // If the constant is the size of a vector element, we just need to bitcast
1614 // it to the right type so it gets properly inserted.
1616 return CollectInsertionElements(ConstantExpr::getBitCast(C, VecEltTy),
1617 Shift, Elements, VecEltTy, IC);
1619 // Okay, this is a constant that covers multiple elements. Slice it up into
1620 // pieces and insert each element-sized piece into the vector.
1621 if (!isa<IntegerType>(C->getType()))
1622 C = ConstantExpr::getBitCast(C, IntegerType::get(V->getContext(),
1623 C->getType()->getPrimitiveSizeInBits()));
1624 unsigned ElementSize = VecEltTy->getPrimitiveSizeInBits();
1625 Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize);
1627 for (unsigned i = 0; i != NumElts; ++i) {
1628 unsigned ShiftI = Shift+i*ElementSize;
1629 Constant *Piece = ConstantExpr::getLShr(C, ConstantInt::get(C->getType(),
1631 Piece = ConstantExpr::getTrunc(Piece, ElementIntTy);
1632 if (!CollectInsertionElements(Piece, ShiftI, Elements, VecEltTy, IC))
1638 if (!V->hasOneUse()) return false;
1640 Instruction *I = dyn_cast<Instruction>(V);
1641 if (I == 0) return false;
1642 switch (I->getOpcode()) {
1643 default: return false; // Unhandled case.
1644 case Instruction::BitCast:
1645 return CollectInsertionElements(I->getOperand(0), Shift,
1646 Elements, VecEltTy, IC);
1647 case Instruction::ZExt:
1648 if (!isMultipleOfTypeSize(
1649 I->getOperand(0)->getType()->getPrimitiveSizeInBits(),
1652 return CollectInsertionElements(I->getOperand(0), Shift,
1653 Elements, VecEltTy, IC);
1654 case Instruction::Or:
1655 return CollectInsertionElements(I->getOperand(0), Shift,
1656 Elements, VecEltTy, IC) &&
1657 CollectInsertionElements(I->getOperand(1), Shift,
1658 Elements, VecEltTy, IC);
1659 case Instruction::Shl: {
1660 // Must be shifting by a constant that is a multiple of the element size.
1661 ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1));
1662 if (CI == 0) return false;
1663 Shift += CI->getZExtValue();
1664 if (!isMultipleOfTypeSize(Shift, VecEltTy)) return false;
1665 return CollectInsertionElements(I->getOperand(0), Shift,
1666 Elements, VecEltTy, IC);
1673 /// OptimizeIntegerToVectorInsertions - If the input is an 'or' instruction, we
1674 /// may be doing shifts and ors to assemble the elements of the vector manually.
1675 /// Try to rip the code out and replace it with insertelements. This is to
1676 /// optimize code like this:
1678 /// %tmp37 = bitcast float %inc to i32
1679 /// %tmp38 = zext i32 %tmp37 to i64
1680 /// %tmp31 = bitcast float %inc5 to i32
1681 /// %tmp32 = zext i32 %tmp31 to i64
1682 /// %tmp33 = shl i64 %tmp32, 32
1683 /// %ins35 = or i64 %tmp33, %tmp38
1684 /// %tmp43 = bitcast i64 %ins35 to <2 x float>
1686 /// Into two insertelements that do "buildvector{%inc, %inc5}".
1687 static Value *OptimizeIntegerToVectorInsertions(BitCastInst &CI,
1689 // We need to know the target byte order to perform this optimization.
1690 if (!IC.getDataLayout()) return 0;
1692 VectorType *DestVecTy = cast<VectorType>(CI.getType());
1693 Value *IntInput = CI.getOperand(0);
1695 SmallVector<Value*, 8> Elements(DestVecTy->getNumElements());
1696 if (!CollectInsertionElements(IntInput, 0, Elements,
1697 DestVecTy->getElementType(), IC))
1700 // If we succeeded, we know that all of the element are specified by Elements
1701 // or are zero if Elements has a null entry. Recast this as a set of
1703 Value *Result = Constant::getNullValue(CI.getType());
1704 for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
1705 if (Elements[i] == 0) continue; // Unset element.
1707 Result = IC.Builder->CreateInsertElement(Result, Elements[i],
1708 IC.Builder->getInt32(i));
1715 /// OptimizeIntToFloatBitCast - See if we can optimize an integer->float/double
1716 /// bitcast. The various long double bitcasts can't get in here.
1717 static Instruction *OptimizeIntToFloatBitCast(BitCastInst &CI,InstCombiner &IC){
1718 // We need to know the target byte order to perform this optimization.
1719 if (!IC.getDataLayout()) return 0;
1721 Value *Src = CI.getOperand(0);
1722 Type *DestTy = CI.getType();
1724 // If this is a bitcast from int to float, check to see if the int is an
1725 // extraction from a vector.
1726 Value *VecInput = 0;
1727 // bitcast(trunc(bitcast(somevector)))
1728 if (match(Src, m_Trunc(m_BitCast(m_Value(VecInput)))) &&
1729 isa<VectorType>(VecInput->getType())) {
1730 VectorType *VecTy = cast<VectorType>(VecInput->getType());
1731 unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
1733 if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0) {
1734 // If the element type of the vector doesn't match the result type,
1735 // bitcast it to be a vector type we can extract from.
1736 if (VecTy->getElementType() != DestTy) {
1737 VecTy = VectorType::get(DestTy,
1738 VecTy->getPrimitiveSizeInBits() / DestWidth);
1739 VecInput = IC.Builder->CreateBitCast(VecInput, VecTy);
1743 if (IC.getDataLayout()->isBigEndian())
1744 Elt = VecTy->getPrimitiveSizeInBits() / DestWidth - 1;
1745 return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
1749 // bitcast(trunc(lshr(bitcast(somevector), cst))
1750 ConstantInt *ShAmt = 0;
1751 if (match(Src, m_Trunc(m_LShr(m_BitCast(m_Value(VecInput)),
1752 m_ConstantInt(ShAmt)))) &&
1753 isa<VectorType>(VecInput->getType())) {
1754 VectorType *VecTy = cast<VectorType>(VecInput->getType());
1755 unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
1756 if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0 &&
1757 ShAmt->getZExtValue() % DestWidth == 0) {
1758 // If the element type of the vector doesn't match the result type,
1759 // bitcast it to be a vector type we can extract from.
1760 if (VecTy->getElementType() != DestTy) {
1761 VecTy = VectorType::get(DestTy,
1762 VecTy->getPrimitiveSizeInBits() / DestWidth);
1763 VecInput = IC.Builder->CreateBitCast(VecInput, VecTy);
1766 unsigned Elt = ShAmt->getZExtValue() / DestWidth;
1767 if (IC.getDataLayout()->isBigEndian())
1768 Elt = VecTy->getPrimitiveSizeInBits() / DestWidth - 1 - Elt;
1769 return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
1775 Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
1776 // If the operands are integer typed then apply the integer transforms,
1777 // otherwise just apply the common ones.
1778 Value *Src = CI.getOperand(0);
1779 Type *SrcTy = Src->getType();
1780 Type *DestTy = CI.getType();
1782 // Get rid of casts from one type to the same type. These are useless and can
1783 // be replaced by the operand.
1784 if (DestTy == Src->getType())
1785 return ReplaceInstUsesWith(CI, Src);
1787 if (PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
1788 PointerType *SrcPTy = cast<PointerType>(SrcTy);
1789 Type *DstElTy = DstPTy->getElementType();
1790 Type *SrcElTy = SrcPTy->getElementType();
1792 // If we are casting a alloca to a pointer to a type of the same
1793 // size, rewrite the allocation instruction to allocate the "right" type.
1794 // There is no need to modify malloc calls because it is their bitcast that
1795 // needs to be cleaned up.
1796 if (AllocaInst *AI = dyn_cast<AllocaInst>(Src))
1797 if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
1800 // If the source and destination are pointers, and this cast is equivalent
1801 // to a getelementptr X, 0, 0, 0... turn it into the appropriate gep.
1802 // This can enhance SROA and other transforms that want type-safe pointers.
1803 Constant *ZeroUInt =
1804 Constant::getNullValue(Type::getInt32Ty(CI.getContext()));
1805 unsigned NumZeros = 0;
1806 while (SrcElTy != DstElTy &&
1807 isa<CompositeType>(SrcElTy) && !SrcElTy->isPointerTy() &&
1808 SrcElTy->getNumContainedTypes() /* not "{}" */) {
1809 SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt);
1813 // If we found a path from the src to dest, create the getelementptr now.
1814 if (SrcElTy == DstElTy) {
1815 SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt);
1816 return GetElementPtrInst::CreateInBounds(Src, Idxs);
1820 // Try to optimize int -> float bitcasts.
1821 if ((DestTy->isFloatTy() || DestTy->isDoubleTy()) && isa<IntegerType>(SrcTy))
1822 if (Instruction *I = OptimizeIntToFloatBitCast(CI, *this))
1825 if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
1826 if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) {
1827 Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType());
1828 return InsertElementInst::Create(UndefValue::get(DestTy), Elem,
1829 Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
1830 // FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast)
1833 if (isa<IntegerType>(SrcTy)) {
1834 // If this is a cast from an integer to vector, check to see if the input
1835 // is a trunc or zext of a bitcast from vector. If so, we can replace all
1836 // the casts with a shuffle and (potentially) a bitcast.
1837 if (isa<TruncInst>(Src) || isa<ZExtInst>(Src)) {
1838 CastInst *SrcCast = cast<CastInst>(Src);
1839 if (BitCastInst *BCIn = dyn_cast<BitCastInst>(SrcCast->getOperand(0)))
1840 if (isa<VectorType>(BCIn->getOperand(0)->getType()))
1841 if (Instruction *I = OptimizeVectorResize(BCIn->getOperand(0),
1842 cast<VectorType>(DestTy), *this))
1846 // If the input is an 'or' instruction, we may be doing shifts and ors to
1847 // assemble the elements of the vector manually. Try to rip the code out
1848 // and replace it with insertelements.
1849 if (Value *V = OptimizeIntegerToVectorInsertions(CI, *this))
1850 return ReplaceInstUsesWith(CI, V);
1854 if (VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) {
1855 if (SrcVTy->getNumElements() == 1) {
1856 // If our destination is not a vector, then make this a straight
1857 // scalar-scalar cast.
1858 if (!DestTy->isVectorTy()) {
1860 Builder->CreateExtractElement(Src,
1861 Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
1862 return CastInst::Create(Instruction::BitCast, Elem, DestTy);
1865 // Otherwise, see if our source is an insert. If so, then use the scalar
1866 // component directly.
1867 if (InsertElementInst *IEI =
1868 dyn_cast<InsertElementInst>(CI.getOperand(0)))
1869 return CastInst::Create(Instruction::BitCast, IEI->getOperand(1),
1874 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) {
1875 // Okay, we have (bitcast (shuffle ..)). Check to see if this is
1876 // a bitcast to a vector with the same # elts.
1877 if (SVI->hasOneUse() && DestTy->isVectorTy() &&
1878 DestTy->getVectorNumElements() == SVI->getType()->getNumElements() &&
1879 SVI->getType()->getNumElements() ==
1880 SVI->getOperand(0)->getType()->getVectorNumElements()) {
1882 // If either of the operands is a cast from CI.getType(), then
1883 // evaluating the shuffle in the casted destination's type will allow
1884 // us to eliminate at least one cast.
1885 if (((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(0))) &&
1886 Tmp->getOperand(0)->getType() == DestTy) ||
1887 ((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(1))) &&
1888 Tmp->getOperand(0)->getType() == DestTy)) {
1889 Value *LHS = Builder->CreateBitCast(SVI->getOperand(0), DestTy);
1890 Value *RHS = Builder->CreateBitCast(SVI->getOperand(1), DestTy);
1891 // Return a new shuffle vector. Use the same element ID's, as we
1892 // know the vector types match #elts.
1893 return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2));
1898 if (SrcTy->isPointerTy())
1899 return commonPointerCastTransforms(CI);
1900 return commonCastTransforms(CI);
1903 Instruction *InstCombiner::visitAddrSpaceCast(AddrSpaceCastInst &CI) {
1904 return commonPointerCastTransforms(CI);