1 //===- ConstantFolding.cpp - LLVM constant folder -------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements folding of constants for LLVM. This implements the
11 // (internal) ConstantFolding.h interface, which is used by the
12 // ConstantExpr::get* methods to automatically fold constants when possible.
14 // The current constant folding implementation is implemented in two pieces: the
15 // template-based folder for simple primitive constants like ConstantInt, and
16 // the special case hackery that we use to symbolically evaluate expressions
17 // that use ConstantExprs.
19 //===----------------------------------------------------------------------===//
21 #include "ConstantFolding.h"
22 #include "llvm/Constants.h"
23 #include "llvm/iPHINode.h"
24 #include "llvm/iOperators.h"
25 #include "llvm/InstrTypes.h"
26 #include "llvm/DerivedTypes.h"
27 #include "llvm/Support/GetElementPtrTypeIterator.h"
35 // Binary Operators...
36 virtual Constant *add(const Constant *V1, const Constant *V2) const = 0;
37 virtual Constant *sub(const Constant *V1, const Constant *V2) const = 0;
38 virtual Constant *mul(const Constant *V1, const Constant *V2) const = 0;
39 virtual Constant *div(const Constant *V1, const Constant *V2) const = 0;
40 virtual Constant *rem(const Constant *V1, const Constant *V2) const = 0;
41 virtual Constant *op_and(const Constant *V1, const Constant *V2) const = 0;
42 virtual Constant *op_or (const Constant *V1, const Constant *V2) const = 0;
43 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const = 0;
44 virtual Constant *shl(const Constant *V1, const Constant *V2) const = 0;
45 virtual Constant *shr(const Constant *V1, const Constant *V2) const = 0;
46 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const =0;
47 virtual Constant *equalto(const Constant *V1, const Constant *V2) const = 0;
50 virtual Constant *castToBool (const Constant *V) const = 0;
51 virtual Constant *castToSByte (const Constant *V) const = 0;
52 virtual Constant *castToUByte (const Constant *V) const = 0;
53 virtual Constant *castToShort (const Constant *V) const = 0;
54 virtual Constant *castToUShort(const Constant *V) const = 0;
55 virtual Constant *castToInt (const Constant *V) const = 0;
56 virtual Constant *castToUInt (const Constant *V) const = 0;
57 virtual Constant *castToLong (const Constant *V) const = 0;
58 virtual Constant *castToULong (const Constant *V) const = 0;
59 virtual Constant *castToFloat (const Constant *V) const = 0;
60 virtual Constant *castToDouble(const Constant *V) const = 0;
61 virtual Constant *castToPointer(const Constant *V,
62 const PointerType *Ty) const = 0;
64 // ConstRules::get - Return an instance of ConstRules for the specified
67 static ConstRules &get(const Constant *V1, const Constant *V2);
69 ConstRules(const ConstRules &); // Do not implement
70 ConstRules &operator=(const ConstRules &); // Do not implement
75 //===----------------------------------------------------------------------===//
76 // TemplateRules Class
77 //===----------------------------------------------------------------------===//
79 // TemplateRules - Implement a subclass of ConstRules that provides all
80 // operations as noops. All other rules classes inherit from this class so
81 // that if functionality is needed in the future, it can simply be added here
82 // and to ConstRules without changing anything else...
84 // This class also provides subclasses with typesafe implementations of methods
85 // so that don't have to do type casting.
87 template<class ArgType, class SubClassName>
88 class TemplateRules : public ConstRules {
90 //===--------------------------------------------------------------------===//
91 // Redirecting functions that cast to the appropriate types
92 //===--------------------------------------------------------------------===//
94 virtual Constant *add(const Constant *V1, const Constant *V2) const {
95 return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2);
97 virtual Constant *sub(const Constant *V1, const Constant *V2) const {
98 return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2);
100 virtual Constant *mul(const Constant *V1, const Constant *V2) const {
101 return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2);
103 virtual Constant *div(const Constant *V1, const Constant *V2) const {
104 return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2);
106 virtual Constant *rem(const Constant *V1, const Constant *V2) const {
107 return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2);
109 virtual Constant *op_and(const Constant *V1, const Constant *V2) const {
110 return SubClassName::And((const ArgType *)V1, (const ArgType *)V2);
112 virtual Constant *op_or(const Constant *V1, const Constant *V2) const {
113 return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2);
115 virtual Constant *op_xor(const Constant *V1, const Constant *V2) const {
116 return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2);
118 virtual Constant *shl(const Constant *V1, const Constant *V2) const {
119 return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2);
121 virtual Constant *shr(const Constant *V1, const Constant *V2) const {
122 return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2);
125 virtual Constant *lessthan(const Constant *V1, const Constant *V2) const {
126 return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2);
128 virtual Constant *equalto(const Constant *V1, const Constant *V2) const {
129 return SubClassName::EqualTo((const ArgType *)V1, (const ArgType *)V2);
132 // Casting operators. ick
133 virtual Constant *castToBool(const Constant *V) const {
134 return SubClassName::CastToBool((const ArgType*)V);
136 virtual Constant *castToSByte(const Constant *V) const {
137 return SubClassName::CastToSByte((const ArgType*)V);
139 virtual Constant *castToUByte(const Constant *V) const {
140 return SubClassName::CastToUByte((const ArgType*)V);
142 virtual Constant *castToShort(const Constant *V) const {
143 return SubClassName::CastToShort((const ArgType*)V);
145 virtual Constant *castToUShort(const Constant *V) const {
146 return SubClassName::CastToUShort((const ArgType*)V);
148 virtual Constant *castToInt(const Constant *V) const {
149 return SubClassName::CastToInt((const ArgType*)V);
151 virtual Constant *castToUInt(const Constant *V) const {
152 return SubClassName::CastToUInt((const ArgType*)V);
154 virtual Constant *castToLong(const Constant *V) const {
155 return SubClassName::CastToLong((const ArgType*)V);
157 virtual Constant *castToULong(const Constant *V) const {
158 return SubClassName::CastToULong((const ArgType*)V);
160 virtual Constant *castToFloat(const Constant *V) const {
161 return SubClassName::CastToFloat((const ArgType*)V);
163 virtual Constant *castToDouble(const Constant *V) const {
164 return SubClassName::CastToDouble((const ArgType*)V);
166 virtual Constant *castToPointer(const Constant *V,
167 const PointerType *Ty) const {
168 return SubClassName::CastToPointer((const ArgType*)V, Ty);
171 //===--------------------------------------------------------------------===//
172 // Default "noop" implementations
173 //===--------------------------------------------------------------------===//
175 static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; }
176 static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; }
177 static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; }
178 static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; }
179 static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; }
180 static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; }
181 static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; }
182 static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; }
183 static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; }
184 static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; }
185 static Constant *LessThan(const ArgType *V1, const ArgType *V2) {
188 static Constant *EqualTo(const ArgType *V1, const ArgType *V2) {
192 // Casting operators. ick
193 static Constant *CastToBool (const Constant *V) { return 0; }
194 static Constant *CastToSByte (const Constant *V) { return 0; }
195 static Constant *CastToUByte (const Constant *V) { return 0; }
196 static Constant *CastToShort (const Constant *V) { return 0; }
197 static Constant *CastToUShort(const Constant *V) { return 0; }
198 static Constant *CastToInt (const Constant *V) { return 0; }
199 static Constant *CastToUInt (const Constant *V) { return 0; }
200 static Constant *CastToLong (const Constant *V) { return 0; }
201 static Constant *CastToULong (const Constant *V) { return 0; }
202 static Constant *CastToFloat (const Constant *V) { return 0; }
203 static Constant *CastToDouble(const Constant *V) { return 0; }
204 static Constant *CastToPointer(const Constant *,
205 const PointerType *) {return 0;}
210 //===----------------------------------------------------------------------===//
212 //===----------------------------------------------------------------------===//
214 // EmptyRules provides a concrete base class of ConstRules that does nothing
216 struct EmptyRules : public TemplateRules<Constant, EmptyRules> {
217 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
218 if (V1 == V2) return ConstantBool::True;
225 //===----------------------------------------------------------------------===//
227 //===----------------------------------------------------------------------===//
229 // BoolRules provides a concrete base class of ConstRules for the 'bool' type.
231 struct BoolRules : public TemplateRules<ConstantBool, BoolRules> {
233 static Constant *LessThan(const ConstantBool *V1, const ConstantBool *V2){
234 return ConstantBool::get(V1->getValue() < V2->getValue());
237 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
238 return ConstantBool::get(V1 == V2);
241 static Constant *And(const ConstantBool *V1, const ConstantBool *V2) {
242 return ConstantBool::get(V1->getValue() & V2->getValue());
245 static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) {
246 return ConstantBool::get(V1->getValue() | V2->getValue());
249 static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) {
250 return ConstantBool::get(V1->getValue() ^ V2->getValue());
253 // Casting operators. ick
254 #define DEF_CAST(TYPE, CLASS, CTYPE) \
255 static Constant *CastTo##TYPE (const ConstantBool *V) { \
256 return CLASS::get(Type::TYPE##Ty, (CTYPE)(bool)V->getValue()); \
259 DEF_CAST(Bool , ConstantBool, bool)
260 DEF_CAST(SByte , ConstantSInt, signed char)
261 DEF_CAST(UByte , ConstantUInt, unsigned char)
262 DEF_CAST(Short , ConstantSInt, signed short)
263 DEF_CAST(UShort, ConstantUInt, unsigned short)
264 DEF_CAST(Int , ConstantSInt, signed int)
265 DEF_CAST(UInt , ConstantUInt, unsigned int)
266 DEF_CAST(Long , ConstantSInt, int64_t)
267 DEF_CAST(ULong , ConstantUInt, uint64_t)
268 DEF_CAST(Float , ConstantFP , float)
269 DEF_CAST(Double, ConstantFP , double)
274 //===----------------------------------------------------------------------===//
275 // NullPointerRules Class
276 //===----------------------------------------------------------------------===//
278 // NullPointerRules provides a concrete base class of ConstRules for null
281 struct NullPointerRules : public TemplateRules<ConstantPointerNull,
283 static Constant *EqualTo(const Constant *V1, const Constant *V2) {
284 return ConstantBool::True; // Null pointers are always equal
286 static Constant *CastToBool(const Constant *V) {
287 return ConstantBool::False;
289 static Constant *CastToSByte (const Constant *V) {
290 return ConstantSInt::get(Type::SByteTy, 0);
292 static Constant *CastToUByte (const Constant *V) {
293 return ConstantUInt::get(Type::UByteTy, 0);
295 static Constant *CastToShort (const Constant *V) {
296 return ConstantSInt::get(Type::ShortTy, 0);
298 static Constant *CastToUShort(const Constant *V) {
299 return ConstantUInt::get(Type::UShortTy, 0);
301 static Constant *CastToInt (const Constant *V) {
302 return ConstantSInt::get(Type::IntTy, 0);
304 static Constant *CastToUInt (const Constant *V) {
305 return ConstantUInt::get(Type::UIntTy, 0);
307 static Constant *CastToLong (const Constant *V) {
308 return ConstantSInt::get(Type::LongTy, 0);
310 static Constant *CastToULong (const Constant *V) {
311 return ConstantUInt::get(Type::ULongTy, 0);
313 static Constant *CastToFloat (const Constant *V) {
314 return ConstantFP::get(Type::FloatTy, 0);
316 static Constant *CastToDouble(const Constant *V) {
317 return ConstantFP::get(Type::DoubleTy, 0);
320 static Constant *CastToPointer(const ConstantPointerNull *V,
321 const PointerType *PTy) {
322 return ConstantPointerNull::get(PTy);
327 //===----------------------------------------------------------------------===//
329 //===----------------------------------------------------------------------===//
331 // DirectRules provides a concrete base classes of ConstRules for a variety of
332 // different types. This allows the C++ compiler to automatically generate our
333 // constant handling operations in a typesafe and accurate manner.
335 template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass>
336 struct DirectRules : public TemplateRules<ConstantClass, SuperClass> {
337 static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) {
338 BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue();
339 return ConstantClass::get(*Ty, R);
342 static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) {
343 BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue();
344 return ConstantClass::get(*Ty, R);
347 static Constant *Mul(const ConstantClass *V1, const ConstantClass *V2) {
348 BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue();
349 return ConstantClass::get(*Ty, R);
352 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
353 if (V2->isNullValue()) return 0;
354 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
355 return ConstantClass::get(*Ty, R);
358 static Constant *LessThan(const ConstantClass *V1, const ConstantClass *V2) {
359 bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue();
360 return ConstantBool::get(R);
363 static Constant *EqualTo(const ConstantClass *V1, const ConstantClass *V2) {
364 bool R = (BuiltinType)V1->getValue() == (BuiltinType)V2->getValue();
365 return ConstantBool::get(R);
368 static Constant *CastToPointer(const ConstantClass *V,
369 const PointerType *PTy) {
370 if (V->isNullValue()) // Is it a FP or Integral null value?
371 return ConstantPointerNull::get(PTy);
372 return 0; // Can't const prop other types of pointers
375 // Casting operators. ick
376 #define DEF_CAST(TYPE, CLASS, CTYPE) \
377 static Constant *CastTo##TYPE (const ConstantClass *V) { \
378 return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \
381 DEF_CAST(Bool , ConstantBool, bool)
382 DEF_CAST(SByte , ConstantSInt, signed char)
383 DEF_CAST(UByte , ConstantUInt, unsigned char)
384 DEF_CAST(Short , ConstantSInt, signed short)
385 DEF_CAST(UShort, ConstantUInt, unsigned short)
386 DEF_CAST(Int , ConstantSInt, signed int)
387 DEF_CAST(UInt , ConstantUInt, unsigned int)
388 DEF_CAST(Long , ConstantSInt, int64_t)
389 DEF_CAST(ULong , ConstantUInt, uint64_t)
390 DEF_CAST(Float , ConstantFP , float)
391 DEF_CAST(Double, ConstantFP , double)
396 //===----------------------------------------------------------------------===//
397 // DirectIntRules Class
398 //===----------------------------------------------------------------------===//
400 // DirectIntRules provides implementations of functions that are valid on
401 // integer types, but not all types in general.
403 template <class ConstantClass, class BuiltinType, Type **Ty>
404 struct DirectIntRules
405 : public DirectRules<ConstantClass, BuiltinType, Ty,
406 DirectIntRules<ConstantClass, BuiltinType, Ty> > {
408 static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
409 if (V2->isNullValue()) return 0;
410 if (V2->isAllOnesValue() && // MIN_INT / -1
411 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue())
413 BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
414 return ConstantClass::get(*Ty, R);
417 static Constant *Rem(const ConstantClass *V1,
418 const ConstantClass *V2) {
419 if (V2->isNullValue()) return 0; // X / 0
420 if (V2->isAllOnesValue() && // MIN_INT / -1
421 (BuiltinType)V1->getValue() == -(BuiltinType)V1->getValue())
423 BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue();
424 return ConstantClass::get(*Ty, R);
427 static Constant *And(const ConstantClass *V1, const ConstantClass *V2) {
428 BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue();
429 return ConstantClass::get(*Ty, R);
431 static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) {
432 BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue();
433 return ConstantClass::get(*Ty, R);
435 static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) {
436 BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue();
437 return ConstantClass::get(*Ty, R);
440 static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) {
441 BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue();
442 return ConstantClass::get(*Ty, R);
445 static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) {
446 BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue();
447 return ConstantClass::get(*Ty, R);
452 //===----------------------------------------------------------------------===//
453 // DirectFPRules Class
454 //===----------------------------------------------------------------------===//
456 /// DirectFPRules provides implementations of functions that are valid on
457 /// floating point types, but not all types in general.
459 template <class ConstantClass, class BuiltinType, Type **Ty>
461 : public DirectRules<ConstantClass, BuiltinType, Ty,
462 DirectFPRules<ConstantClass, BuiltinType, Ty> > {
463 static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) {
464 if (V2->isNullValue()) return 0;
465 BuiltinType Result = std::fmod((BuiltinType)V1->getValue(),
466 (BuiltinType)V2->getValue());
467 return ConstantClass::get(*Ty, Result);
472 /// ConstRules::get - This method returns the constant rules implementation that
473 /// implements the semantics of the two specified constants.
474 ConstRules &ConstRules::get(const Constant *V1, const Constant *V2) {
475 static EmptyRules EmptyR;
476 static BoolRules BoolR;
477 static NullPointerRules NullPointerR;
478 static DirectIntRules<ConstantSInt, signed char , &Type::SByteTy> SByteR;
479 static DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy> UByteR;
480 static DirectIntRules<ConstantSInt, signed short, &Type::ShortTy> ShortR;
481 static DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy> UShortR;
482 static DirectIntRules<ConstantSInt, signed int , &Type::IntTy> IntR;
483 static DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy> UIntR;
484 static DirectIntRules<ConstantSInt, int64_t , &Type::LongTy> LongR;
485 static DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy> ULongR;
486 static DirectFPRules <ConstantFP , float , &Type::FloatTy> FloatR;
487 static DirectFPRules <ConstantFP , double , &Type::DoubleTy> DoubleR;
489 if (isa<ConstantExpr>(V1) || isa<ConstantExpr>(V2) ||
490 isa<ConstantPointerRef>(V1) || isa<ConstantPointerRef>(V2))
493 switch (V1->getType()->getPrimitiveID()) {
494 default: assert(0 && "Unknown value type for constant folding!");
495 case Type::BoolTyID: return BoolR;
496 case Type::PointerTyID: return NullPointerR;
497 case Type::SByteTyID: return SByteR;
498 case Type::UByteTyID: return UByteR;
499 case Type::ShortTyID: return ShortR;
500 case Type::UShortTyID: return UShortR;
501 case Type::IntTyID: return IntR;
502 case Type::UIntTyID: return UIntR;
503 case Type::LongTyID: return LongR;
504 case Type::ULongTyID: return ULongR;
505 case Type::FloatTyID: return FloatR;
506 case Type::DoubleTyID: return DoubleR;
511 //===----------------------------------------------------------------------===//
512 // ConstantFold*Instruction Implementations
513 //===----------------------------------------------------------------------===//
515 // These methods contain the special case hackery required to symbolically
516 // evaluate some constant expression cases, and use the ConstantRules class to
517 // evaluate normal constants.
519 static unsigned getSize(const Type *Ty) {
520 unsigned S = Ty->getPrimitiveSize();
521 return S ? S : 8; // Treat pointers at 8 bytes
524 Constant *llvm::ConstantFoldCastInstruction(const Constant *V,
525 const Type *DestTy) {
526 if (V->getType() == DestTy) return (Constant*)V;
528 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
529 if (CE->getOpcode() == Instruction::Cast) {
530 Constant *Op = const_cast<Constant*>(CE->getOperand(0));
531 // Try to not produce a cast of a cast, which is almost always redundant.
532 if (!Op->getType()->isFloatingPoint() &&
533 !CE->getType()->isFloatingPoint() &&
534 !DestTy->getType()->isFloatingPoint()) {
535 unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType());
536 unsigned S3 = getSize(DestTy);
537 if (Op->getType() == DestTy && S3 >= S2)
539 if (S1 >= S2 && S2 >= S3)
540 return ConstantExpr::getCast(Op, DestTy);
541 if (S1 <= S2 && S2 >= S3 && S1 <= S3)
542 return ConstantExpr::getCast(Op, DestTy);
544 } else if (CE->getOpcode() == Instruction::GetElementPtr) {
545 // If all of the indexes in the GEP are null values, there is no pointer
546 // adjustment going on. We might as well cast the source pointer.
547 bool isAllNull = true;
548 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
549 if (!CE->getOperand(i)->isNullValue()) {
554 return ConstantExpr::getCast(CE->getOperand(0), DestTy);
557 ConstRules &Rules = ConstRules::get(V, V);
559 switch (DestTy->getPrimitiveID()) {
560 case Type::BoolTyID: return Rules.castToBool(V);
561 case Type::UByteTyID: return Rules.castToUByte(V);
562 case Type::SByteTyID: return Rules.castToSByte(V);
563 case Type::UShortTyID: return Rules.castToUShort(V);
564 case Type::ShortTyID: return Rules.castToShort(V);
565 case Type::UIntTyID: return Rules.castToUInt(V);
566 case Type::IntTyID: return Rules.castToInt(V);
567 case Type::ULongTyID: return Rules.castToULong(V);
568 case Type::LongTyID: return Rules.castToLong(V);
569 case Type::FloatTyID: return Rules.castToFloat(V);
570 case Type::DoubleTyID: return Rules.castToDouble(V);
571 case Type::PointerTyID:
572 return Rules.castToPointer(V, cast<PointerType>(DestTy));
577 /// IdxCompare - Compare the two constants as though they were getelementptr
578 /// indices. This allows coersion of the types to be the same thing.
580 /// If the two constants are the "same" (after coersion), return 0. If the
581 /// first is less than the second, return -1, if the second is less than the
582 /// first, return 1. If the constants are not integral, return -2.
584 static int IdxCompare(Constant *C1, Constant *C2) {
585 if (C1 == C2) return 0;
587 // Ok, we found a different index. Are either of the operands
588 // ConstantExprs? If so, we can't do anything with them.
589 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
590 return -2; // don't know!
592 // Ok, we have two differing integer indices. Convert them to
593 // be the same type. Long is always big enough, so we use it.
594 C1 = ConstantExpr::getCast(C1, Type::LongTy);
595 C2 = ConstantExpr::getCast(C2, Type::LongTy);
596 if (C1 == C2) return 0; // Are they just differing types?
598 // If they are really different, now that they are the same type, then we
599 // found a difference!
600 if (cast<ConstantSInt>(C1)->getValue() < cast<ConstantSInt>(C2)->getValue())
606 /// evaluateRelation - This function determines if there is anything we can
607 /// decide about the two constants provided. This doesn't need to handle simple
608 /// things like integer comparisons, but should instead handle ConstantExpr's
609 /// and ConstantPointerRef's. If we can determine that the two constants have a
610 /// particular relation to each other, we should return the corresponding SetCC
611 /// code, otherwise return Instruction::BinaryOpsEnd.
613 /// To simplify this code we canonicalize the relation so that the first
614 /// operand is always the most "complex" of the two. We consider simple
615 /// constants (like ConstantInt) to be the simplest, followed by
616 /// ConstantPointerRef's, followed by ConstantExpr's (the most complex).
618 static Instruction::BinaryOps evaluateRelation(const Constant *V1,
619 const Constant *V2) {
620 assert(V1->getType() == V2->getType() &&
621 "Cannot compare different types of values!");
622 if (V1 == V2) return Instruction::SetEQ;
624 if (!isa<ConstantExpr>(V1) && !isa<ConstantPointerRef>(V1)) {
625 // If the first operand is simple, swap operands.
626 assert((isa<ConstantPointerRef>(V2) || isa<ConstantExpr>(V2)) &&
627 "Simple cases should have been handled by caller!");
628 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
629 if (SwappedRelation != Instruction::BinaryOpsEnd)
630 return SetCondInst::getSwappedCondition(SwappedRelation);
632 } else if (const ConstantPointerRef *CPR1 = dyn_cast<ConstantPointerRef>(V1)){
633 if (isa<ConstantExpr>(V2)) { // Swap as necessary.
634 Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
635 if (SwappedRelation != Instruction::BinaryOpsEnd)
636 return SetCondInst::getSwappedCondition(SwappedRelation);
638 return Instruction::BinaryOpsEnd;
641 // Now we know that the RHS is a ConstantPointerRef or simple constant,
642 // which (since the types must match) means that it's a ConstantPointerNull.
643 if (const ConstantPointerRef *CPR2 = dyn_cast<ConstantPointerRef>(V2)) {
644 assert(CPR1->getValue() != CPR2->getValue() &&
645 "CPRs for the same value exist at different addresses??");
646 // FIXME: If both globals are external weak, they might both be null!
647 return Instruction::SetNE;
649 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
650 // Global can never be null. FIXME: if we implement external weak
651 // linkage, this is not necessarily true!
652 return Instruction::SetNE;
656 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
657 // constantexpr, a CPR, or a simple constant.
658 const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
659 Constant *CE1Op0 = CE1->getOperand(0);
661 switch (CE1->getOpcode()) {
662 case Instruction::Cast:
663 // If the cast is not actually changing bits, and the second operand is a
664 // null pointer, do the comparison with the pre-casted value.
665 if (V2->isNullValue() &&
666 CE1->getType()->isLosslesslyConvertibleTo(CE1Op0->getType()))
667 return evaluateRelation(CE1Op0,
668 Constant::getNullValue(CE1Op0->getType()));
670 case Instruction::GetElementPtr:
671 // Ok, since this is a getelementptr, we know that the constant has a
672 // pointer type. Check the various cases.
673 if (isa<ConstantPointerNull>(V2)) {
674 // If we are comparing a GEP to a null pointer, check to see if the base
675 // of the GEP equals the null pointer.
676 if (isa<ConstantPointerRef>(CE1Op0)) {
677 // FIXME: this is not true when we have external weak references!
678 // No offset can go from a global to a null pointer.
679 return Instruction::SetGT;
680 } else if (isa<ConstantPointerNull>(CE1Op0)) {
681 // If we are indexing from a null pointer, check to see if we have any
683 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
684 if (!CE1->getOperand(i)->isNullValue())
685 // Offsetting from null, must not be equal.
686 return Instruction::SetGT;
687 // Only zero indexes from null, must still be zero.
688 return Instruction::SetEQ;
690 // Otherwise, we can't really say if the first operand is null or not.
691 } else if (const ConstantPointerRef *CPR2 =
692 dyn_cast<ConstantPointerRef>(V2)) {
693 if (isa<ConstantPointerNull>(CE1Op0)) {
694 // FIXME: This is not true with external weak references.
695 return Instruction::SetLT;
696 } else if (const ConstantPointerRef *CPR1 =
697 dyn_cast<ConstantPointerRef>(CE1Op0)) {
699 // If this is a getelementptr of the same global, then it must be
700 // different. Because the types must match, the getelementptr could
701 // only have at most one index, and because we fold getelementptr's
702 // with a single zero index, it must be nonzero.
703 assert(CE1->getNumOperands() == 2 &&
704 !CE1->getOperand(1)->isNullValue() &&
705 "Suprising getelementptr!");
706 return Instruction::SetGT;
708 // If they are different globals, we don't know what the value is,
709 // but they can't be equal.
710 return Instruction::SetNE;
714 const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
715 const Constant *CE2Op0 = CE2->getOperand(0);
717 // There are MANY other foldings that we could perform here. They will
718 // probably be added on demand, as they seem needed.
719 switch (CE2->getOpcode()) {
721 case Instruction::GetElementPtr:
722 // By far the most common case to handle is when the base pointers are
723 // obviously to the same or different globals.
724 if (isa<ConstantPointerRef>(CE1Op0) &&
725 isa<ConstantPointerRef>(CE2Op0)) {
726 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
727 return Instruction::SetNE;
728 // Ok, we know that both getelementptr instructions are based on the
729 // same global. From this, we can precisely determine the relative
730 // ordering of the resultant pointers.
733 // Compare all of the operands the GEP's have in common.
734 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); ++i)
735 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i))) {
736 case -1: return Instruction::SetLT;
737 case 1: return Instruction::SetGT;
738 case -2: return Instruction::BinaryOpsEnd;
741 // Ok, we ran out of things they have in common. If any leftovers
742 // are non-zero then we have a difference, otherwise we are equal.
743 for (; i < CE1->getNumOperands(); ++i)
744 if (!CE1->getOperand(i)->isNullValue())
745 return Instruction::SetGT;
746 for (; i < CE2->getNumOperands(); ++i)
747 if (!CE2->getOperand(i)->isNullValue())
748 return Instruction::SetLT;
749 return Instruction::SetEQ;
759 return Instruction::BinaryOpsEnd;
762 Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
764 const Constant *V2) {
768 case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break;
769 case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break;
770 case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break;
771 case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break;
772 case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break;
773 case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break;
774 case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break;
775 case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break;
776 case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break;
777 case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break;
778 case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break;
779 case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break;
780 case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break;
781 case Instruction::SetNE: // V1 != V2 === !(V1 == V2)
782 C = ConstRules::get(V1, V2).equalto(V1, V2);
783 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True);
785 case Instruction::SetLE: // V1 <= V2 === !(V2 < V1)
786 C = ConstRules::get(V1, V2).lessthan(V2, V1);
787 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True);
789 case Instruction::SetGE: // V1 >= V2 === !(V1 < V2)
790 C = ConstRules::get(V1, V2).lessthan(V1, V2);
791 if (C) return ConstantExpr::get(Instruction::Xor, C, ConstantBool::True);
795 // If we successfully folded the expression, return it now.
798 if (SetCondInst::isRelational(Opcode))
799 switch (evaluateRelation(V1, V2)) {
800 default: assert(0 && "Unknown relational!");
801 case Instruction::BinaryOpsEnd:
802 break; // Couldn't determine anything about these constants.
803 case Instruction::SetEQ: // We know the constants are equal!
804 // If we know the constants are equal, we can decide the result of this
805 // computation precisely.
806 return ConstantBool::get(Opcode == Instruction::SetEQ ||
807 Opcode == Instruction::SetLE ||
808 Opcode == Instruction::SetGE);
809 case Instruction::SetLT:
810 // If we know that V1 < V2, we can decide the result of this computation
812 return ConstantBool::get(Opcode == Instruction::SetLT ||
813 Opcode == Instruction::SetNE ||
814 Opcode == Instruction::SetLE);
815 case Instruction::SetGT:
816 // If we know that V1 > V2, we can decide the result of this computation
818 return ConstantBool::get(Opcode == Instruction::SetGT ||
819 Opcode == Instruction::SetNE ||
820 Opcode == Instruction::SetGE);
821 case Instruction::SetLE:
822 // If we know that V1 <= V2, we can only partially decide this relation.
823 if (Opcode == Instruction::SetGT) return ConstantBool::False;
824 if (Opcode == Instruction::SetLT) return ConstantBool::True;
827 case Instruction::SetGE:
828 // If we know that V1 >= V2, we can only partially decide this relation.
829 if (Opcode == Instruction::SetLT) return ConstantBool::False;
830 if (Opcode == Instruction::SetGT) return ConstantBool::True;
833 case Instruction::SetNE:
834 // If we know that V1 != V2, we can only partially decide this relation.
835 if (Opcode == Instruction::SetEQ) return ConstantBool::False;
836 if (Opcode == Instruction::SetNE) return ConstantBool::True;
840 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) {
841 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
842 // There are many possible foldings we could do here. We should probably
843 // at least fold add of a pointer with an integer into the appropriate
844 // getelementptr. This will improve alias analysis a bit.
850 // Just implement a couple of simple identities.
852 case Instruction::Add:
853 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X
855 case Instruction::Sub:
856 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X
858 case Instruction::Mul:
859 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0
860 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
861 if (CI->getRawValue() == 1)
862 return const_cast<Constant*>(V1); // X * 1 == X
864 case Instruction::Div:
865 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
866 if (CI->getRawValue() == 1)
867 return const_cast<Constant*>(V1); // X / 1 == X
869 case Instruction::Rem:
870 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
871 if (CI->getRawValue() == 1)
872 return Constant::getNullValue(CI->getType()); // X % 1 == 0
874 case Instruction::And:
875 if (cast<ConstantIntegral>(V2)->isAllOnesValue())
876 return const_cast<Constant*>(V1); // X & -1 == X
877 if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0
879 case Instruction::Or:
880 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X
881 if (cast<ConstantIntegral>(V2)->isAllOnesValue())
882 return const_cast<Constant*>(V2); // X | -1 == -1
884 case Instruction::Xor:
885 if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X
890 } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
891 // If V2 is a constant expr and V1 isn't, flop them around and fold the
892 // other way if possible.
894 case Instruction::Add:
895 case Instruction::Mul:
896 case Instruction::And:
897 case Instruction::Or:
898 case Instruction::Xor:
899 case Instruction::SetEQ:
900 case Instruction::SetNE:
901 // No change of opcode required.
902 return ConstantFoldBinaryInstruction(Opcode, V2, V1);
904 case Instruction::SetLT:
905 case Instruction::SetGT:
906 case Instruction::SetLE:
907 case Instruction::SetGE:
908 // Change the opcode as necessary to swap the operands.
909 Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode);
910 return ConstantFoldBinaryInstruction(Opcode, V2, V1);
912 case Instruction::Shl:
913 case Instruction::Shr:
914 case Instruction::Sub:
915 case Instruction::Div:
916 case Instruction::Rem:
917 default: // These instructions cannot be flopped around.
924 Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
925 const std::vector<Constant*> &IdxList) {
926 if (IdxList.size() == 0 ||
927 (IdxList.size() == 1 && IdxList[0]->isNullValue()))
928 return const_cast<Constant*>(C);
930 // TODO If C is null and all idx's are null, return null of the right type.
933 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
934 // Combine Indices - If the source pointer to this getelementptr instruction
935 // is a getelementptr instruction, combine the indices of the two
936 // getelementptr instructions into a single instruction.
938 if (CE->getOpcode() == Instruction::GetElementPtr) {
939 const Type *LastTy = 0;
940 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
944 if ((LastTy && isa<ArrayType>(LastTy)) || IdxList[0]->isNullValue()) {
945 std::vector<Constant*> NewIndices;
946 NewIndices.reserve(IdxList.size() + CE->getNumOperands());
947 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
948 NewIndices.push_back(cast<Constant>(CE->getOperand(i)));
950 // Add the last index of the source with the first index of the new GEP.
951 // Make sure to handle the case when they are actually different types.
952 Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
953 if (!IdxList[0]->isNullValue()) // Otherwise it must be an array
955 ConstantExpr::get(Instruction::Add,
956 ConstantExpr::getCast(IdxList[0], Type::LongTy),
957 ConstantExpr::getCast(Combined, Type::LongTy));
959 NewIndices.push_back(Combined);
960 NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end());
961 return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices);
965 // Implement folding of:
966 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
968 // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
970 if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 &&
971 IdxList[0]->isNullValue())
972 if (const PointerType *SPT =
973 dyn_cast<PointerType>(CE->getOperand(0)->getType()))
974 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
975 if (const ArrayType *CAT =
976 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
977 if (CAT->getElementType() == SAT->getElementType())
978 return ConstantExpr::getGetElementPtr(
979 (Constant*)CE->getOperand(0), IdxList);