1 //===- MergeFunctions.cpp - Merge identical functions ---------------------===//
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 pass looks for equivalent functions that are mergable and folds them.
12 // Order relation is defined on set of functions. It was made through
13 // special function comparison procedure that returns
14 // 0 when functions are equal,
15 // -1 when Left function is less than right function, and
16 // 1 for opposite case. We need total-ordering, so we need to maintain
17 // four properties on the functions set:
18 // a <= a (reflexivity)
19 // if a <= b and b <= a then a = b (antisymmetry)
20 // if a <= b and b <= c then a <= c (transitivity).
21 // for all a and b: a <= b or b <= a (totality).
23 // Comparison iterates through each instruction in each basic block.
24 // Functions are kept on binary tree. For each new function F we perform
25 // lookup in binary tree.
26 // In practice it works the following way:
27 // -- We define Function* container class with custom "operator<" (FunctionPtr).
28 // -- "FunctionPtr" instances are stored in std::set collection, so every
29 // std::set::insert operation will give you result in log(N) time.
31 // As an optimization, a hash of the function structure is calculated first, and
32 // two functions are only compared if they have the same hash. This hash is
33 // cheap to compute, and has the property that if function F == G according to
34 // the comparison function, then hash(F) == hash(G). This consistency property
35 // is critical to ensuring all possible merging opportunities are exploited.
36 // Collisions in the hash affect the speed of the pass but not the correctness
37 // or determinism of the resulting transformation.
39 // When a match is found the functions are folded. If both functions are
40 // overridable, we move the functionality into a new internal function and
41 // leave two overridable thunks to it.
43 //===----------------------------------------------------------------------===//
47 // * virtual functions.
49 // Many functions have their address taken by the virtual function table for
50 // the object they belong to. However, as long as it's only used for a lookup
51 // and call, this is irrelevant, and we'd like to fold such functions.
53 // * be smarter about bitcasts.
55 // In order to fold functions, we will sometimes add either bitcast instructions
56 // or bitcast constant expressions. Unfortunately, this can confound further
57 // analysis since the two functions differ where one has a bitcast and the
58 // other doesn't. We should learn to look through bitcasts.
60 // * Compare complex types with pointer types inside.
61 // * Compare cross-reference cases.
62 // * Compare complex expressions.
64 // All the three issues above could be described as ability to prove that
65 // fA == fB == fC == fE == fF == fG in example below:
84 // Simplest cross-reference case (fA <--> fB) was implemented in previous
85 // versions of MergeFunctions, though it presented only in two function pairs
86 // in test-suite (that counts >50k functions)
87 // Though possibility to detect complex cross-referencing (e.g.: A->B->C->D->A)
88 // could cover much more cases.
90 //===----------------------------------------------------------------------===//
92 #include "llvm/ADT/Hashing.h"
93 #include "llvm/ADT/STLExtras.h"
94 #include "llvm/ADT/SmallSet.h"
95 #include "llvm/ADT/Statistic.h"
96 #include "llvm/IR/CallSite.h"
97 #include "llvm/IR/Constants.h"
98 #include "llvm/IR/DataLayout.h"
99 #include "llvm/IR/IRBuilder.h"
100 #include "llvm/IR/InlineAsm.h"
101 #include "llvm/IR/Instructions.h"
102 #include "llvm/IR/LLVMContext.h"
103 #include "llvm/IR/Module.h"
104 #include "llvm/IR/Operator.h"
105 #include "llvm/IR/ValueHandle.h"
106 #include "llvm/IR/ValueMap.h"
107 #include "llvm/Pass.h"
108 #include "llvm/Support/CommandLine.h"
109 #include "llvm/Support/Debug.h"
110 #include "llvm/Support/ErrorHandling.h"
111 #include "llvm/Support/raw_ostream.h"
112 #include "llvm/Transforms/IPO.h"
115 using namespace llvm;
117 #define DEBUG_TYPE "mergefunc"
119 STATISTIC(NumFunctionsMerged, "Number of functions merged");
120 STATISTIC(NumThunksWritten, "Number of thunks generated");
121 STATISTIC(NumAliasesWritten, "Number of aliases generated");
122 STATISTIC(NumDoubleWeak, "Number of new functions created");
124 static cl::opt<unsigned> NumFunctionsForSanityCheck(
126 cl::desc("How many functions in module could be used for "
127 "MergeFunctions pass sanity check. "
128 "'0' disables this check. Works only with '-debug' key."),
129 cl::init(0), cl::Hidden);
133 /// GlobalNumberState assigns an integer to each global value in the program,
134 /// which is used by the comparison routine to order references to globals. This
135 /// state must be preserved throughout the pass, because Functions and other
136 /// globals need to maintain their relative order. Globals are assigned a number
137 /// when they are first visited. This order is deterministic, and so the
138 /// assigned numbers are as well. When two functions are merged, neither number
139 /// is updated. If the symbols are weak, this would be incorrect. If they are
140 /// strong, then one will be replaced at all references to the other, and so
141 /// direct callsites will now see one or the other symbol, and no update is
142 /// necessary. Note that if we were guaranteed unique names, we could just
143 /// compare those, but this would not work for stripped bitcodes or for those
144 /// few symbols without a name.
145 class GlobalNumberState {
146 struct Config : ValueMapConfig<GlobalValue*> {
147 enum { FollowRAUW = false };
149 // Each GlobalValue is mapped to an identifier. The Config ensures when RAUW
150 // occurs, the mapping does not change. Tracking changes is unnecessary, and
151 // also problematic for weak symbols (which may be overwritten).
152 typedef ValueMap<GlobalValue *, uint64_t, Config> ValueNumberMap;
153 ValueNumberMap GlobalNumbers;
154 // The next unused serial number to assign to a global.
157 GlobalNumberState() : GlobalNumbers(), NextNumber(0) {}
158 uint64_t getNumber(GlobalValue* Global) {
159 ValueNumberMap::iterator MapIter;
161 std::tie(MapIter, Inserted) = GlobalNumbers.insert({Global, NextNumber});
164 return MapIter->second;
167 GlobalNumbers.clear();
171 /// FunctionComparator - Compares two functions to determine whether or not
172 /// they will generate machine code with the same behaviour. DataLayout is
173 /// used if available. The comparator always fails conservatively (erring on the
174 /// side of claiming that two functions are different).
175 class FunctionComparator {
177 FunctionComparator(const Function *F1, const Function *F2,
178 GlobalNumberState* GN)
179 : FnL(F1), FnR(F2), GlobalNumbers(GN) {}
181 /// Test whether the two functions have equivalent behaviour.
183 /// Hash a function. Equivalent functions will have the same hash, and unequal
184 /// functions will have different hashes with high probability.
185 typedef uint64_t FunctionHash;
186 static FunctionHash functionHash(Function &);
189 /// Test whether two basic blocks have equivalent behaviour.
190 int cmpBasicBlocks(const BasicBlock *BBL, const BasicBlock *BBR) const;
192 /// Constants comparison.
193 /// Its analog to lexicographical comparison between hypothetical numbers
195 /// <bitcastability-trait><raw-bit-contents>
197 /// 1. Bitcastability.
198 /// Check whether L's type could be losslessly bitcasted to R's type.
199 /// On this stage method, in case when lossless bitcast is not possible
200 /// method returns -1 or 1, thus also defining which type is greater in
201 /// context of bitcastability.
202 /// Stage 0: If types are equal in terms of cmpTypes, then we can go straight
203 /// to the contents comparison.
204 /// If types differ, remember types comparison result and check
205 /// whether we still can bitcast types.
206 /// Stage 1: Types that satisfies isFirstClassType conditions are always
207 /// greater then others.
208 /// Stage 2: Vector is greater then non-vector.
209 /// If both types are vectors, then vector with greater bitwidth is
211 /// If both types are vectors with the same bitwidth, then types
212 /// are bitcastable, and we can skip other stages, and go to contents
214 /// Stage 3: Pointer types are greater than non-pointers. If both types are
215 /// pointers of the same address space - go to contents comparison.
216 /// Different address spaces: pointer with greater address space is
218 /// Stage 4: Types are neither vectors, nor pointers. And they differ.
219 /// We don't know how to bitcast them. So, we better don't do it,
220 /// and return types comparison result (so it determines the
221 /// relationship among constants we don't know how to bitcast).
223 /// Just for clearance, let's see how the set of constants could look
224 /// on single dimension axis:
226 /// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors]
227 /// Where: NFCT - Not a FirstClassType
228 /// FCT - FirstClassTyp:
230 /// 2. Compare raw contents.
231 /// It ignores types on this stage and only compares bits from L and R.
232 /// Returns 0, if L and R has equivalent contents.
233 /// -1 or 1 if values are different.
235 /// 2.1. If contents are numbers, compare numbers.
236 /// Ints with greater bitwidth are greater. Ints with same bitwidths
237 /// compared by their contents.
238 /// 2.2. "And so on". Just to avoid discrepancies with comments
239 /// perhaps it would be better to read the implementation itself.
240 /// 3. And again about overall picture. Let's look back at how the ordered set
241 /// of constants will look like:
242 /// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors]
244 /// Now look, what could be inside [FCT, "others"], for example:
245 /// [FCT, "others"] =
247 /// [double 0.1], [double 1.23],
248 /// [i32 1], [i32 2],
249 /// { double 1.0 }, ; StructTyID, NumElements = 1
250 /// { i32 1 }, ; StructTyID, NumElements = 1
251 /// { double 1, i32 1 }, ; StructTyID, NumElements = 2
252 /// { i32 1, double 1 } ; StructTyID, NumElements = 2
255 /// Let's explain the order. Float numbers will be less than integers, just
256 /// because of cmpType terms: FloatTyID < IntegerTyID.
257 /// Floats (with same fltSemantics) are sorted according to their value.
258 /// Then you can see integers, and they are, like a floats,
259 /// could be easy sorted among each others.
260 /// The structures. Structures are grouped at the tail, again because of their
261 /// TypeID: StructTyID > IntegerTyID > FloatTyID.
262 /// Structures with greater number of elements are greater. Structures with
263 /// greater elements going first are greater.
264 /// The same logic with vectors, arrays and other possible complex types.
266 /// Bitcastable constants.
267 /// Let's assume, that some constant, belongs to some group of
268 /// "so-called-equal" values with different types, and at the same time
269 /// belongs to another group of constants with equal types
270 /// and "really" equal values.
272 /// Now, prove that this is impossible:
274 /// If constant A with type TyA is bitcastable to B with type TyB, then:
275 /// 1. All constants with equal types to TyA, are bitcastable to B. Since
276 /// those should be vectors (if TyA is vector), pointers
277 /// (if TyA is pointer), or else (if TyA equal to TyB), those types should
279 /// 2. All constants with non-equal, but bitcastable types to TyA, are
280 /// bitcastable to B.
281 /// Once again, just because we allow it to vectors and pointers only.
282 /// This statement could be expanded as below:
283 /// 2.1. All vectors with equal bitwidth to vector A, has equal bitwidth to
284 /// vector B, and thus bitcastable to B as well.
285 /// 2.2. All pointers of the same address space, no matter what they point to,
286 /// bitcastable. So if C is pointer, it could be bitcasted to A and to B.
287 /// So any constant equal or bitcastable to A is equal or bitcastable to B.
290 /// In another words, for pointers and vectors, we ignore top-level type and
291 /// look at their particular properties (bit-width for vectors, and
292 /// address space for pointers).
293 /// If these properties are equal - compare their contents.
294 int cmpConstants(const Constant *L, const Constant *R) const;
296 /// Compares two global values by number. Uses the GlobalNumbersState to
297 /// identify the same gobals across function calls.
298 int cmpGlobalValues(GlobalValue *L, GlobalValue *R) const;
300 /// Assign or look up previously assigned numbers for the two values, and
301 /// return whether the numbers are equal. Numbers are assigned in the order
303 /// Comparison order:
304 /// Stage 0: Value that is function itself is always greater then others.
305 /// If left and right values are references to their functions, then
307 /// Stage 1: Constants are greater than non-constants.
308 /// If both left and right are constants, then the result of
309 /// cmpConstants is used as cmpValues result.
310 /// Stage 2: InlineAsm instances are greater than others. If both left and
311 /// right are InlineAsm instances, InlineAsm* pointers casted to
312 /// integers and compared as numbers.
313 /// Stage 3: For all other cases we compare order we meet these values in
314 /// their functions. If right value was met first during scanning,
315 /// then left value is greater.
316 /// In another words, we compare serial numbers, for more details
317 /// see comments for sn_mapL and sn_mapR.
318 int cmpValues(const Value *L, const Value *R) const;
320 /// Compare two Instructions for equivalence, similar to
321 /// Instruction::isSameOperationAs.
323 /// Stages are listed in "most significant stage first" order:
324 /// On each stage below, we do comparison between some left and right
325 /// operation parts. If parts are non-equal, we assign parts comparison
326 /// result to the operation comparison result and exit from method.
327 /// Otherwise we proceed to the next stage.
329 /// 1. Operations opcodes. Compared as numbers.
330 /// 2. Number of operands.
331 /// 3. Operation types. Compared with cmpType method.
332 /// 4. Compare operation subclass optional data as stream of bytes:
333 /// just convert it to integers and call cmpNumbers.
334 /// 5. Compare in operation operand types with cmpType in
335 /// most significant operand first order.
336 /// 6. Last stage. Check operations for some specific attributes.
337 /// For example, for Load it would be:
338 /// 6.1.Load: volatile (as boolean flag)
339 /// 6.2.Load: alignment (as integer numbers)
340 /// 6.3.Load: ordering (as underlying enum class value)
341 /// 6.4.Load: synch-scope (as integer numbers)
342 /// 6.5.Load: range metadata (as integer ranges)
343 /// On this stage its better to see the code, since its not more than 10-15
344 /// strings for particular instruction, and could change sometimes.
345 int cmpOperations(const Instruction *L, const Instruction *R) const;
347 /// Compare two GEPs for equivalent pointer arithmetic.
348 /// Parts to be compared for each comparison stage,
349 /// most significant stage first:
350 /// 1. Address space. As numbers.
351 /// 2. Constant offset, (using GEPOperator::accumulateConstantOffset method).
352 /// 3. Pointer operand type (using cmpType method).
353 /// 4. Number of operands.
354 /// 5. Compare operands, using cmpValues method.
355 int cmpGEPs(const GEPOperator *GEPL, const GEPOperator *GEPR) const;
356 int cmpGEPs(const GetElementPtrInst *GEPL,
357 const GetElementPtrInst *GEPR) const {
358 return cmpGEPs(cast<GEPOperator>(GEPL), cast<GEPOperator>(GEPR));
361 /// cmpType - compares two types,
362 /// defines total ordering among the types set.
365 /// 0 if types are equal,
366 /// -1 if Left is less than Right,
367 /// +1 if Left is greater than Right.
370 /// Comparison is broken onto stages. Like in lexicographical comparison
371 /// stage coming first has higher priority.
372 /// On each explanation stage keep in mind total ordering properties.
374 /// 0. Before comparison we coerce pointer types of 0 address space to
376 /// We also don't bother with same type at left and right, so
377 /// just return 0 in this case.
379 /// 1. If types are of different kind (different type IDs).
380 /// Return result of type IDs comparison, treating them as numbers.
381 /// 2. If types are integers, check that they have the same width. If they
382 /// are vectors, check that they have the same count and subtype.
383 /// 3. Types have the same ID, so check whether they are one of:
392 /// We can treat these types as equal whenever their IDs are same.
393 /// 4. If Left and Right are pointers, return result of address space
394 /// comparison (numbers comparison). We can treat pointer types of same
395 /// address space as equal.
396 /// 5. If types are complex.
397 /// Then both Left and Right are to be expanded and their element types will
398 /// be checked with the same way. If we get Res != 0 on some stage, return it.
399 /// Otherwise return 0.
400 /// 6. For all other cases put llvm_unreachable.
401 int cmpTypes(Type *TyL, Type *TyR) const;
403 int cmpNumbers(uint64_t L, uint64_t R) const;
404 int cmpOrderings(AtomicOrdering L, AtomicOrdering R) const;
405 int cmpAPInts(const APInt &L, const APInt &R) const;
406 int cmpAPFloats(const APFloat &L, const APFloat &R) const;
407 int cmpInlineAsm(const InlineAsm *L, const InlineAsm *R) const;
408 int cmpMem(StringRef L, StringRef R) const;
409 int cmpAttrs(const AttributeSet L, const AttributeSet R) const;
410 int cmpRangeMetadata(const MDNode *L, const MDNode *R) const;
411 int cmpOperandBundlesSchema(const Instruction *L, const Instruction *R) const;
413 // The two functions undergoing comparison.
414 const Function *FnL, *FnR;
416 /// Assign serial numbers to values from left function, and values from
419 /// Being comparing functions we need to compare values we meet at left and
421 /// Its easy to sort things out for external values. It just should be
422 /// the same value at left and right.
423 /// But for local values (those were introduced inside function body)
424 /// we have to ensure they were introduced at exactly the same place,
425 /// and plays the same role.
426 /// Let's assign serial number to each value when we meet it first time.
427 /// Values that were met at same place will be with same serial numbers.
428 /// In this case it would be good to explain few points about values assigned
429 /// to BBs and other ways of implementation (see below).
431 /// 1. Safety of BB reordering.
432 /// It's safe to change the order of BasicBlocks in function.
433 /// Relationship with other functions and serial numbering will not be
434 /// changed in this case.
435 /// As follows from FunctionComparator::compare(), we do CFG walk: we start
436 /// from the entry, and then take each terminator. So it doesn't matter how in
437 /// fact BBs are ordered in function. And since cmpValues are called during
438 /// this walk, the numbering depends only on how BBs located inside the CFG.
439 /// So the answer is - yes. We will get the same numbering.
441 /// 2. Impossibility to use dominance properties of values.
442 /// If we compare two instruction operands: first is usage of local
443 /// variable AL from function FL, and second is usage of local variable AR
444 /// from FR, we could compare their origins and check whether they are
445 /// defined at the same place.
446 /// But, we are still not able to compare operands of PHI nodes, since those
447 /// could be operands from further BBs we didn't scan yet.
448 /// So it's impossible to use dominance properties in general.
449 mutable DenseMap<const Value*, int> sn_mapL, sn_mapR;
451 // The global state we will use
452 GlobalNumberState* GlobalNumbers;
456 mutable AssertingVH<Function> F;
457 FunctionComparator::FunctionHash Hash;
459 // Note the hash is recalculated potentially multiple times, but it is cheap.
460 FunctionNode(Function *F)
461 : F(F), Hash(FunctionComparator::functionHash(*F)) {}
462 Function *getFunc() const { return F; }
463 FunctionComparator::FunctionHash getHash() const { return Hash; }
465 /// Replace the reference to the function F by the function G, assuming their
466 /// implementations are equal.
467 void replaceBy(Function *G) const {
471 void release() { F = nullptr; }
473 } // end anonymous namespace
475 int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const {
476 if (L < R) return -1;
481 int FunctionComparator::cmpOrderings(AtomicOrdering L, AtomicOrdering R) const {
482 if ((int)L < (int)R) return -1;
483 if ((int)L > (int)R) return 1;
487 int FunctionComparator::cmpAPInts(const APInt &L, const APInt &R) const {
488 if (int Res = cmpNumbers(L.getBitWidth(), R.getBitWidth()))
490 if (L.ugt(R)) return 1;
491 if (R.ugt(L)) return -1;
495 int FunctionComparator::cmpAPFloats(const APFloat &L, const APFloat &R) const {
496 // Floats are ordered first by semantics (i.e. float, double, half, etc.),
497 // then by value interpreted as a bitstring (aka APInt).
498 const fltSemantics &SL = L.getSemantics(), &SR = R.getSemantics();
499 if (int Res = cmpNumbers(APFloat::semanticsPrecision(SL),
500 APFloat::semanticsPrecision(SR)))
502 if (int Res = cmpNumbers(APFloat::semanticsMaxExponent(SL),
503 APFloat::semanticsMaxExponent(SR)))
505 if (int Res = cmpNumbers(APFloat::semanticsMinExponent(SL),
506 APFloat::semanticsMinExponent(SR)))
508 if (int Res = cmpNumbers(APFloat::semanticsSizeInBits(SL),
509 APFloat::semanticsSizeInBits(SR)))
511 return cmpAPInts(L.bitcastToAPInt(), R.bitcastToAPInt());
514 int FunctionComparator::cmpMem(StringRef L, StringRef R) const {
515 // Prevent heavy comparison, compare sizes first.
516 if (int Res = cmpNumbers(L.size(), R.size()))
519 // Compare strings lexicographically only when it is necessary: only when
520 // strings are equal in size.
524 int FunctionComparator::cmpAttrs(const AttributeSet L,
525 const AttributeSet R) const {
526 if (int Res = cmpNumbers(L.getNumSlots(), R.getNumSlots()))
529 for (unsigned i = 0, e = L.getNumSlots(); i != e; ++i) {
530 AttributeSet::iterator LI = L.begin(i), LE = L.end(i), RI = R.begin(i),
532 for (; LI != LE && RI != RE; ++LI, ++RI) {
548 int FunctionComparator::cmpRangeMetadata(const MDNode *L,
549 const MDNode *R) const {
556 // Range metadata is a sequence of numbers. Make sure they are the same
558 // TODO: Note that as this is metadata, it is possible to drop and/or merge
559 // this data when considering functions to merge. Thus this comparison would
560 // return 0 (i.e. equivalent), but merging would become more complicated
561 // because the ranges would need to be unioned. It is not likely that
562 // functions differ ONLY in this metadata if they are actually the same
563 // function semantically.
564 if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands()))
566 for (size_t I = 0; I < L->getNumOperands(); ++I) {
567 ConstantInt *LLow = mdconst::extract<ConstantInt>(L->getOperand(I));
568 ConstantInt *RLow = mdconst::extract<ConstantInt>(R->getOperand(I));
569 if (int Res = cmpAPInts(LLow->getValue(), RLow->getValue()))
575 int FunctionComparator::cmpOperandBundlesSchema(const Instruction *L,
576 const Instruction *R) const {
577 ImmutableCallSite LCS(L);
578 ImmutableCallSite RCS(R);
580 assert(LCS && RCS && "Must be calls or invokes!");
581 assert(LCS.isCall() == RCS.isCall() && "Can't compare otherwise!");
584 cmpNumbers(LCS.getNumOperandBundles(), RCS.getNumOperandBundles()))
587 for (unsigned i = 0, e = LCS.getNumOperandBundles(); i != e; ++i) {
588 auto OBL = LCS.getOperandBundleAt(i);
589 auto OBR = RCS.getOperandBundleAt(i);
591 if (int Res = OBL.getTagName().compare(OBR.getTagName()))
594 if (int Res = cmpNumbers(OBL.Inputs.size(), OBR.Inputs.size()))
601 /// Constants comparison:
602 /// 1. Check whether type of L constant could be losslessly bitcasted to R
604 /// 2. Compare constant contents.
605 /// For more details see declaration comments.
606 int FunctionComparator::cmpConstants(const Constant *L,
607 const Constant *R) const {
609 Type *TyL = L->getType();
610 Type *TyR = R->getType();
612 // Check whether types are bitcastable. This part is just re-factored
613 // Type::canLosslesslyBitCastTo method, but instead of returning true/false,
614 // we also pack into result which type is "less" for us.
615 int TypesRes = cmpTypes(TyL, TyR);
617 // Types are different, but check whether we can bitcast them.
618 if (!TyL->isFirstClassType()) {
619 if (TyR->isFirstClassType())
621 // Neither TyL nor TyR are values of first class type. Return the result
622 // of comparing the types
625 if (!TyR->isFirstClassType()) {
626 if (TyL->isFirstClassType())
631 // Vector -> Vector conversions are always lossless if the two vector types
632 // have the same size, otherwise not.
633 unsigned TyLWidth = 0;
634 unsigned TyRWidth = 0;
636 if (auto *VecTyL = dyn_cast<VectorType>(TyL))
637 TyLWidth = VecTyL->getBitWidth();
638 if (auto *VecTyR = dyn_cast<VectorType>(TyR))
639 TyRWidth = VecTyR->getBitWidth();
641 if (TyLWidth != TyRWidth)
642 return cmpNumbers(TyLWidth, TyRWidth);
644 // Zero bit-width means neither TyL nor TyR are vectors.
646 PointerType *PTyL = dyn_cast<PointerType>(TyL);
647 PointerType *PTyR = dyn_cast<PointerType>(TyR);
649 unsigned AddrSpaceL = PTyL->getAddressSpace();
650 unsigned AddrSpaceR = PTyR->getAddressSpace();
651 if (int Res = cmpNumbers(AddrSpaceL, AddrSpaceR))
659 // TyL and TyR aren't vectors, nor pointers. We don't know how to
665 // OK, types are bitcastable, now check constant contents.
667 if (L->isNullValue() && R->isNullValue())
669 if (L->isNullValue() && !R->isNullValue())
671 if (!L->isNullValue() && R->isNullValue())
674 auto GlobalValueL = const_cast<GlobalValue*>(dyn_cast<GlobalValue>(L));
675 auto GlobalValueR = const_cast<GlobalValue*>(dyn_cast<GlobalValue>(R));
676 if (GlobalValueL && GlobalValueR) {
677 return cmpGlobalValues(GlobalValueL, GlobalValueR);
680 if (int Res = cmpNumbers(L->getValueID(), R->getValueID()))
683 if (const auto *SeqL = dyn_cast<ConstantDataSequential>(L)) {
684 const auto *SeqR = cast<ConstantDataSequential>(R);
685 // This handles ConstantDataArray and ConstantDataVector. Note that we
686 // compare the two raw data arrays, which might differ depending on the host
687 // endianness. This isn't a problem though, because the endiness of a module
688 // will affect the order of the constants, but this order is the same
689 // for a given input module and host platform.
690 return cmpMem(SeqL->getRawDataValues(), SeqR->getRawDataValues());
693 switch (L->getValueID()) {
694 case Value::UndefValueVal:
695 case Value::ConstantTokenNoneVal:
697 case Value::ConstantIntVal: {
698 const APInt &LInt = cast<ConstantInt>(L)->getValue();
699 const APInt &RInt = cast<ConstantInt>(R)->getValue();
700 return cmpAPInts(LInt, RInt);
702 case Value::ConstantFPVal: {
703 const APFloat &LAPF = cast<ConstantFP>(L)->getValueAPF();
704 const APFloat &RAPF = cast<ConstantFP>(R)->getValueAPF();
705 return cmpAPFloats(LAPF, RAPF);
707 case Value::ConstantArrayVal: {
708 const ConstantArray *LA = cast<ConstantArray>(L);
709 const ConstantArray *RA = cast<ConstantArray>(R);
710 uint64_t NumElementsL = cast<ArrayType>(TyL)->getNumElements();
711 uint64_t NumElementsR = cast<ArrayType>(TyR)->getNumElements();
712 if (int Res = cmpNumbers(NumElementsL, NumElementsR))
714 for (uint64_t i = 0; i < NumElementsL; ++i) {
715 if (int Res = cmpConstants(cast<Constant>(LA->getOperand(i)),
716 cast<Constant>(RA->getOperand(i))))
721 case Value::ConstantStructVal: {
722 const ConstantStruct *LS = cast<ConstantStruct>(L);
723 const ConstantStruct *RS = cast<ConstantStruct>(R);
724 unsigned NumElementsL = cast<StructType>(TyL)->getNumElements();
725 unsigned NumElementsR = cast<StructType>(TyR)->getNumElements();
726 if (int Res = cmpNumbers(NumElementsL, NumElementsR))
728 for (unsigned i = 0; i != NumElementsL; ++i) {
729 if (int Res = cmpConstants(cast<Constant>(LS->getOperand(i)),
730 cast<Constant>(RS->getOperand(i))))
735 case Value::ConstantVectorVal: {
736 const ConstantVector *LV = cast<ConstantVector>(L);
737 const ConstantVector *RV = cast<ConstantVector>(R);
738 unsigned NumElementsL = cast<VectorType>(TyL)->getNumElements();
739 unsigned NumElementsR = cast<VectorType>(TyR)->getNumElements();
740 if (int Res = cmpNumbers(NumElementsL, NumElementsR))
742 for (uint64_t i = 0; i < NumElementsL; ++i) {
743 if (int Res = cmpConstants(cast<Constant>(LV->getOperand(i)),
744 cast<Constant>(RV->getOperand(i))))
749 case Value::ConstantExprVal: {
750 const ConstantExpr *LE = cast<ConstantExpr>(L);
751 const ConstantExpr *RE = cast<ConstantExpr>(R);
752 unsigned NumOperandsL = LE->getNumOperands();
753 unsigned NumOperandsR = RE->getNumOperands();
754 if (int Res = cmpNumbers(NumOperandsL, NumOperandsR))
756 for (unsigned i = 0; i < NumOperandsL; ++i) {
757 if (int Res = cmpConstants(cast<Constant>(LE->getOperand(i)),
758 cast<Constant>(RE->getOperand(i))))
763 case Value::BlockAddressVal: {
764 const BlockAddress *LBA = cast<BlockAddress>(L);
765 const BlockAddress *RBA = cast<BlockAddress>(R);
766 if (int Res = cmpValues(LBA->getFunction(), RBA->getFunction()))
768 if (LBA->getFunction() == RBA->getFunction()) {
769 // They are BBs in the same function. Order by which comes first in the
770 // BB order of the function. This order is deterministic.
771 Function* F = LBA->getFunction();
772 BasicBlock *LBB = LBA->getBasicBlock();
773 BasicBlock *RBB = RBA->getBasicBlock();
776 for(BasicBlock &BB : F->getBasicBlockList()) {
784 llvm_unreachable("Basic Block Address does not point to a basic block in "
788 // cmpValues said the functions are the same. So because they aren't
789 // literally the same pointer, they must respectively be the left and
791 assert(LBA->getFunction() == FnL && RBA->getFunction() == FnR);
792 // cmpValues will tell us if these are equivalent BasicBlocks, in the
793 // context of their respective functions.
794 return cmpValues(LBA->getBasicBlock(), RBA->getBasicBlock());
797 default: // Unknown constant, abort.
798 DEBUG(dbgs() << "Looking at valueID " << L->getValueID() << "\n");
799 llvm_unreachable("Constant ValueID not recognized.");
804 int FunctionComparator::cmpGlobalValues(GlobalValue *L, GlobalValue *R) const {
805 return cmpNumbers(GlobalNumbers->getNumber(L), GlobalNumbers->getNumber(R));
808 /// cmpType - compares two types,
809 /// defines total ordering among the types set.
810 /// See method declaration comments for more details.
811 int FunctionComparator::cmpTypes(Type *TyL, Type *TyR) const {
812 PointerType *PTyL = dyn_cast<PointerType>(TyL);
813 PointerType *PTyR = dyn_cast<PointerType>(TyR);
815 const DataLayout &DL = FnL->getParent()->getDataLayout();
816 if (PTyL && PTyL->getAddressSpace() == 0)
817 TyL = DL.getIntPtrType(TyL);
818 if (PTyR && PTyR->getAddressSpace() == 0)
819 TyR = DL.getIntPtrType(TyR);
824 if (int Res = cmpNumbers(TyL->getTypeID(), TyR->getTypeID()))
827 switch (TyL->getTypeID()) {
829 llvm_unreachable("Unknown type!");
830 // Fall through in Release mode.
831 case Type::IntegerTyID:
832 return cmpNumbers(cast<IntegerType>(TyL)->getBitWidth(),
833 cast<IntegerType>(TyR)->getBitWidth());
834 case Type::VectorTyID: {
835 VectorType *VTyL = cast<VectorType>(TyL), *VTyR = cast<VectorType>(TyR);
836 if (int Res = cmpNumbers(VTyL->getNumElements(), VTyR->getNumElements()))
838 return cmpTypes(VTyL->getElementType(), VTyR->getElementType());
840 // TyL == TyR would have returned true earlier, because types are uniqued.
842 case Type::FloatTyID:
843 case Type::DoubleTyID:
844 case Type::X86_FP80TyID:
845 case Type::FP128TyID:
846 case Type::PPC_FP128TyID:
847 case Type::LabelTyID:
848 case Type::MetadataTyID:
849 case Type::TokenTyID:
852 case Type::PointerTyID: {
853 assert(PTyL && PTyR && "Both types must be pointers here.");
854 return cmpNumbers(PTyL->getAddressSpace(), PTyR->getAddressSpace());
857 case Type::StructTyID: {
858 StructType *STyL = cast<StructType>(TyL);
859 StructType *STyR = cast<StructType>(TyR);
860 if (STyL->getNumElements() != STyR->getNumElements())
861 return cmpNumbers(STyL->getNumElements(), STyR->getNumElements());
863 if (STyL->isPacked() != STyR->isPacked())
864 return cmpNumbers(STyL->isPacked(), STyR->isPacked());
866 for (unsigned i = 0, e = STyL->getNumElements(); i != e; ++i) {
867 if (int Res = cmpTypes(STyL->getElementType(i), STyR->getElementType(i)))
873 case Type::FunctionTyID: {
874 FunctionType *FTyL = cast<FunctionType>(TyL);
875 FunctionType *FTyR = cast<FunctionType>(TyR);
876 if (FTyL->getNumParams() != FTyR->getNumParams())
877 return cmpNumbers(FTyL->getNumParams(), FTyR->getNumParams());
879 if (FTyL->isVarArg() != FTyR->isVarArg())
880 return cmpNumbers(FTyL->isVarArg(), FTyR->isVarArg());
882 if (int Res = cmpTypes(FTyL->getReturnType(), FTyR->getReturnType()))
885 for (unsigned i = 0, e = FTyL->getNumParams(); i != e; ++i) {
886 if (int Res = cmpTypes(FTyL->getParamType(i), FTyR->getParamType(i)))
892 case Type::ArrayTyID: {
893 ArrayType *ATyL = cast<ArrayType>(TyL);
894 ArrayType *ATyR = cast<ArrayType>(TyR);
895 if (ATyL->getNumElements() != ATyR->getNumElements())
896 return cmpNumbers(ATyL->getNumElements(), ATyR->getNumElements());
897 return cmpTypes(ATyL->getElementType(), ATyR->getElementType());
902 // Determine whether the two operations are the same except that pointer-to-A
903 // and pointer-to-B are equivalent. This should be kept in sync with
904 // Instruction::isSameOperationAs.
905 // Read method declaration comments for more details.
906 int FunctionComparator::cmpOperations(const Instruction *L,
907 const Instruction *R) const {
908 // Differences from Instruction::isSameOperationAs:
909 // * replace type comparison with calls to cmpTypes.
910 // * we test for I->getRawSubclassOptionalData (nuw/nsw/tail) at the top.
911 // * because of the above, we don't test for the tail bit on calls later on.
912 if (int Res = cmpNumbers(L->getOpcode(), R->getOpcode()))
915 if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands()))
918 if (int Res = cmpTypes(L->getType(), R->getType()))
921 if (int Res = cmpNumbers(L->getRawSubclassOptionalData(),
922 R->getRawSubclassOptionalData()))
925 // We have two instructions of identical opcode and #operands. Check to see
926 // if all operands are the same type
927 for (unsigned i = 0, e = L->getNumOperands(); i != e; ++i) {
929 cmpTypes(L->getOperand(i)->getType(), R->getOperand(i)->getType()))
933 // Check special state that is a part of some instructions.
934 if (const AllocaInst *AI = dyn_cast<AllocaInst>(L)) {
935 if (int Res = cmpTypes(AI->getAllocatedType(),
936 cast<AllocaInst>(R)->getAllocatedType()))
938 return cmpNumbers(AI->getAlignment(), cast<AllocaInst>(R)->getAlignment());
940 if (const LoadInst *LI = dyn_cast<LoadInst>(L)) {
941 if (int Res = cmpNumbers(LI->isVolatile(), cast<LoadInst>(R)->isVolatile()))
944 cmpNumbers(LI->getAlignment(), cast<LoadInst>(R)->getAlignment()))
947 cmpOrderings(LI->getOrdering(), cast<LoadInst>(R)->getOrdering()))
950 cmpNumbers(LI->getSynchScope(), cast<LoadInst>(R)->getSynchScope()))
952 return cmpRangeMetadata(LI->getMetadata(LLVMContext::MD_range),
953 cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range));
955 if (const StoreInst *SI = dyn_cast<StoreInst>(L)) {
957 cmpNumbers(SI->isVolatile(), cast<StoreInst>(R)->isVolatile()))
960 cmpNumbers(SI->getAlignment(), cast<StoreInst>(R)->getAlignment()))
963 cmpOrderings(SI->getOrdering(), cast<StoreInst>(R)->getOrdering()))
965 return cmpNumbers(SI->getSynchScope(), cast<StoreInst>(R)->getSynchScope());
967 if (const CmpInst *CI = dyn_cast<CmpInst>(L))
968 return cmpNumbers(CI->getPredicate(), cast<CmpInst>(R)->getPredicate());
969 if (const CallInst *CI = dyn_cast<CallInst>(L)) {
970 if (int Res = cmpNumbers(CI->getCallingConv(),
971 cast<CallInst>(R)->getCallingConv()))
974 cmpAttrs(CI->getAttributes(), cast<CallInst>(R)->getAttributes()))
976 if (int Res = cmpOperandBundlesSchema(CI, R))
978 return cmpRangeMetadata(
979 CI->getMetadata(LLVMContext::MD_range),
980 cast<CallInst>(R)->getMetadata(LLVMContext::MD_range));
982 if (const InvokeInst *II = dyn_cast<InvokeInst>(L)) {
983 if (int Res = cmpNumbers(II->getCallingConv(),
984 cast<InvokeInst>(R)->getCallingConv()))
987 cmpAttrs(II->getAttributes(), cast<InvokeInst>(R)->getAttributes()))
989 if (int Res = cmpOperandBundlesSchema(II, R))
991 return cmpRangeMetadata(
992 II->getMetadata(LLVMContext::MD_range),
993 cast<InvokeInst>(R)->getMetadata(LLVMContext::MD_range));
995 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(L)) {
996 ArrayRef<unsigned> LIndices = IVI->getIndices();
997 ArrayRef<unsigned> RIndices = cast<InsertValueInst>(R)->getIndices();
998 if (int Res = cmpNumbers(LIndices.size(), RIndices.size()))
1000 for (size_t i = 0, e = LIndices.size(); i != e; ++i) {
1001 if (int Res = cmpNumbers(LIndices[i], RIndices[i]))
1006 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(L)) {
1007 ArrayRef<unsigned> LIndices = EVI->getIndices();
1008 ArrayRef<unsigned> RIndices = cast<ExtractValueInst>(R)->getIndices();
1009 if (int Res = cmpNumbers(LIndices.size(), RIndices.size()))
1011 for (size_t i = 0, e = LIndices.size(); i != e; ++i) {
1012 if (int Res = cmpNumbers(LIndices[i], RIndices[i]))
1016 if (const FenceInst *FI = dyn_cast<FenceInst>(L)) {
1018 cmpOrderings(FI->getOrdering(), cast<FenceInst>(R)->getOrdering()))
1020 return cmpNumbers(FI->getSynchScope(), cast<FenceInst>(R)->getSynchScope());
1022 if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(L)) {
1023 if (int Res = cmpNumbers(CXI->isVolatile(),
1024 cast<AtomicCmpXchgInst>(R)->isVolatile()))
1026 if (int Res = cmpNumbers(CXI->isWeak(),
1027 cast<AtomicCmpXchgInst>(R)->isWeak()))
1030 cmpOrderings(CXI->getSuccessOrdering(),
1031 cast<AtomicCmpXchgInst>(R)->getSuccessOrdering()))
1034 cmpOrderings(CXI->getFailureOrdering(),
1035 cast<AtomicCmpXchgInst>(R)->getFailureOrdering()))
1037 return cmpNumbers(CXI->getSynchScope(),
1038 cast<AtomicCmpXchgInst>(R)->getSynchScope());
1040 if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(L)) {
1041 if (int Res = cmpNumbers(RMWI->getOperation(),
1042 cast<AtomicRMWInst>(R)->getOperation()))
1044 if (int Res = cmpNumbers(RMWI->isVolatile(),
1045 cast<AtomicRMWInst>(R)->isVolatile()))
1047 if (int Res = cmpOrderings(RMWI->getOrdering(),
1048 cast<AtomicRMWInst>(R)->getOrdering()))
1050 return cmpNumbers(RMWI->getSynchScope(),
1051 cast<AtomicRMWInst>(R)->getSynchScope());
1053 if (const PHINode *PNL = dyn_cast<PHINode>(L)) {
1054 const PHINode *PNR = cast<PHINode>(R);
1055 // Ensure that in addition to the incoming values being identical
1056 // (checked by the caller of this function), the incoming blocks
1057 // are also identical.
1058 for (unsigned i = 0, e = PNL->getNumIncomingValues(); i != e; ++i) {
1060 cmpValues(PNL->getIncomingBlock(i), PNR->getIncomingBlock(i)))
1067 // Determine whether two GEP operations perform the same underlying arithmetic.
1068 // Read method declaration comments for more details.
1069 int FunctionComparator::cmpGEPs(const GEPOperator *GEPL,
1070 const GEPOperator *GEPR) const {
1072 unsigned int ASL = GEPL->getPointerAddressSpace();
1073 unsigned int ASR = GEPR->getPointerAddressSpace();
1075 if (int Res = cmpNumbers(ASL, ASR))
1078 // When we have target data, we can reduce the GEP down to the value in bytes
1079 // added to the address.
1080 const DataLayout &DL = FnL->getParent()->getDataLayout();
1081 unsigned BitWidth = DL.getPointerSizeInBits(ASL);
1082 APInt OffsetL(BitWidth, 0), OffsetR(BitWidth, 0);
1083 if (GEPL->accumulateConstantOffset(DL, OffsetL) &&
1084 GEPR->accumulateConstantOffset(DL, OffsetR))
1085 return cmpAPInts(OffsetL, OffsetR);
1086 if (int Res = cmpTypes(GEPL->getSourceElementType(),
1087 GEPR->getSourceElementType()))
1090 if (int Res = cmpNumbers(GEPL->getNumOperands(), GEPR->getNumOperands()))
1093 for (unsigned i = 0, e = GEPL->getNumOperands(); i != e; ++i) {
1094 if (int Res = cmpValues(GEPL->getOperand(i), GEPR->getOperand(i)))
1101 int FunctionComparator::cmpInlineAsm(const InlineAsm *L,
1102 const InlineAsm *R) const {
1103 // InlineAsm's are uniqued. If they are the same pointer, obviously they are
1104 // the same, otherwise compare the fields.
1107 if (int Res = cmpTypes(L->getFunctionType(), R->getFunctionType()))
1109 if (int Res = cmpMem(L->getAsmString(), R->getAsmString()))
1111 if (int Res = cmpMem(L->getConstraintString(), R->getConstraintString()))
1113 if (int Res = cmpNumbers(L->hasSideEffects(), R->hasSideEffects()))
1115 if (int Res = cmpNumbers(L->isAlignStack(), R->isAlignStack()))
1117 if (int Res = cmpNumbers(L->getDialect(), R->getDialect()))
1119 llvm_unreachable("InlineAsm blocks were not uniqued.");
1123 /// Compare two values used by the two functions under pair-wise comparison. If
1124 /// this is the first time the values are seen, they're added to the mapping so
1125 /// that we will detect mismatches on next use.
1126 /// See comments in declaration for more details.
1127 int FunctionComparator::cmpValues(const Value *L, const Value *R) const {
1128 // Catch self-reference case.
1140 const Constant *ConstL = dyn_cast<Constant>(L);
1141 const Constant *ConstR = dyn_cast<Constant>(R);
1142 if (ConstL && ConstR) {
1145 return cmpConstants(ConstL, ConstR);
1153 const InlineAsm *InlineAsmL = dyn_cast<InlineAsm>(L);
1154 const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
1156 if (InlineAsmL && InlineAsmR)
1157 return cmpInlineAsm(InlineAsmL, InlineAsmR);
1163 auto LeftSN = sn_mapL.insert(std::make_pair(L, sn_mapL.size())),
1164 RightSN = sn_mapR.insert(std::make_pair(R, sn_mapR.size()));
1166 return cmpNumbers(LeftSN.first->second, RightSN.first->second);
1168 // Test whether two basic blocks have equivalent behaviour.
1169 int FunctionComparator::cmpBasicBlocks(const BasicBlock *BBL,
1170 const BasicBlock *BBR) const {
1171 BasicBlock::const_iterator InstL = BBL->begin(), InstLE = BBL->end();
1172 BasicBlock::const_iterator InstR = BBR->begin(), InstRE = BBR->end();
1175 if (int Res = cmpValues(&*InstL, &*InstR))
1178 const GetElementPtrInst *GEPL = dyn_cast<GetElementPtrInst>(InstL);
1179 const GetElementPtrInst *GEPR = dyn_cast<GetElementPtrInst>(InstR);
1188 cmpValues(GEPL->getPointerOperand(), GEPR->getPointerOperand()))
1190 if (int Res = cmpGEPs(GEPL, GEPR))
1193 if (int Res = cmpOperations(&*InstL, &*InstR))
1195 assert(InstL->getNumOperands() == InstR->getNumOperands());
1197 for (unsigned i = 0, e = InstL->getNumOperands(); i != e; ++i) {
1198 Value *OpL = InstL->getOperand(i);
1199 Value *OpR = InstR->getOperand(i);
1200 if (int Res = cmpValues(OpL, OpR))
1202 // cmpValues should ensure this is true.
1203 assert(cmpTypes(OpL->getType(), OpR->getType()) == 0);
1209 } while (InstL != InstLE && InstR != InstRE);
1211 if (InstL != InstLE && InstR == InstRE)
1213 if (InstL == InstLE && InstR != InstRE)
1218 // Test whether the two functions have equivalent behaviour.
1219 int FunctionComparator::compare() {
1223 if (int Res = cmpAttrs(FnL->getAttributes(), FnR->getAttributes()))
1226 if (int Res = cmpNumbers(FnL->hasGC(), FnR->hasGC()))
1230 if (int Res = cmpMem(FnL->getGC(), FnR->getGC()))
1234 if (int Res = cmpNumbers(FnL->hasSection(), FnR->hasSection()))
1237 if (FnL->hasSection()) {
1238 if (int Res = cmpMem(FnL->getSection(), FnR->getSection()))
1242 if (int Res = cmpNumbers(FnL->isVarArg(), FnR->isVarArg()))
1245 // TODO: if it's internal and only used in direct calls, we could handle this
1247 if (int Res = cmpNumbers(FnL->getCallingConv(), FnR->getCallingConv()))
1250 if (int Res = cmpTypes(FnL->getFunctionType(), FnR->getFunctionType()))
1253 assert(FnL->arg_size() == FnR->arg_size() &&
1254 "Identically typed functions have different numbers of args!");
1256 // Visit the arguments so that they get enumerated in the order they're
1258 for (Function::const_arg_iterator ArgLI = FnL->arg_begin(),
1259 ArgRI = FnR->arg_begin(),
1260 ArgLE = FnL->arg_end();
1261 ArgLI != ArgLE; ++ArgLI, ++ArgRI) {
1262 if (cmpValues(&*ArgLI, &*ArgRI) != 0)
1263 llvm_unreachable("Arguments repeat!");
1266 // We do a CFG-ordered walk since the actual ordering of the blocks in the
1267 // linked list is immaterial. Our walk starts at the entry block for both
1268 // functions, then takes each block from each terminator in order. As an
1269 // artifact, this also means that unreachable blocks are ignored.
1270 SmallVector<const BasicBlock *, 8> FnLBBs, FnRBBs;
1271 SmallPtrSet<const BasicBlock *, 32> VisitedBBs; // in terms of F1.
1273 FnLBBs.push_back(&FnL->getEntryBlock());
1274 FnRBBs.push_back(&FnR->getEntryBlock());
1276 VisitedBBs.insert(FnLBBs[0]);
1277 while (!FnLBBs.empty()) {
1278 const BasicBlock *BBL = FnLBBs.pop_back_val();
1279 const BasicBlock *BBR = FnRBBs.pop_back_val();
1281 if (int Res = cmpValues(BBL, BBR))
1284 if (int Res = cmpBasicBlocks(BBL, BBR))
1287 const TerminatorInst *TermL = BBL->getTerminator();
1288 const TerminatorInst *TermR = BBR->getTerminator();
1290 assert(TermL->getNumSuccessors() == TermR->getNumSuccessors());
1291 for (unsigned i = 0, e = TermL->getNumSuccessors(); i != e; ++i) {
1292 if (!VisitedBBs.insert(TermL->getSuccessor(i)).second)
1295 FnLBBs.push_back(TermL->getSuccessor(i));
1296 FnRBBs.push_back(TermR->getSuccessor(i));
1303 // Accumulate the hash of a sequence of 64-bit integers. This is similar to a
1304 // hash of a sequence of 64bit ints, but the entire input does not need to be
1305 // available at once. This interface is necessary for functionHash because it
1306 // needs to accumulate the hash as the structure of the function is traversed
1307 // without saving these values to an intermediate buffer. This form of hashing
1308 // is not often needed, as usually the object to hash is just read from a
1310 class HashAccumulator64 {
1313 // Initialize to random constant, so the state isn't zero.
1314 HashAccumulator64() { Hash = 0x6acaa36bef8325c5ULL; }
1315 void add(uint64_t V) {
1316 Hash = llvm::hashing::detail::hash_16_bytes(Hash, V);
1318 // No finishing is required, because the entire hash value is used.
1319 uint64_t getHash() { return Hash; }
1321 } // end anonymous namespace
1323 // A function hash is calculated by considering only the number of arguments and
1324 // whether a function is varargs, the order of basic blocks (given by the
1325 // successors of each basic block in depth first order), and the order of
1326 // opcodes of each instruction within each of these basic blocks. This mirrors
1327 // the strategy compare() uses to compare functions by walking the BBs in depth
1328 // first order and comparing each instruction in sequence. Because this hash
1329 // does not look at the operands, it is insensitive to things such as the
1330 // target of calls and the constants used in the function, which makes it useful
1331 // when possibly merging functions which are the same modulo constants and call
1333 FunctionComparator::FunctionHash FunctionComparator::functionHash(Function &F) {
1334 HashAccumulator64 H;
1335 H.add(F.isVarArg());
1336 H.add(F.arg_size());
1338 SmallVector<const BasicBlock *, 8> BBs;
1339 SmallSet<const BasicBlock *, 16> VisitedBBs;
1341 // Walk the blocks in the same order as FunctionComparator::cmpBasicBlocks(),
1342 // accumulating the hash of the function "structure." (BB and opcode sequence)
1343 BBs.push_back(&F.getEntryBlock());
1344 VisitedBBs.insert(BBs[0]);
1345 while (!BBs.empty()) {
1346 const BasicBlock *BB = BBs.pop_back_val();
1347 // This random value acts as a block header, as otherwise the partition of
1348 // opcodes into BBs wouldn't affect the hash, only the order of the opcodes
1350 for (auto &Inst : *BB) {
1351 H.add(Inst.getOpcode());
1353 const TerminatorInst *Term = BB->getTerminator();
1354 for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
1355 if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
1357 BBs.push_back(Term->getSuccessor(i));
1366 /// MergeFunctions finds functions which will generate identical machine code,
1367 /// by considering all pointer types to be equivalent. Once identified,
1368 /// MergeFunctions will fold them by replacing a call to one to a call to a
1369 /// bitcast of the other.
1371 class MergeFunctions : public ModulePass {
1375 : ModulePass(ID), FnTree(FunctionNodeCmp(&GlobalNumbers)), FNodesInTree(),
1376 HasGlobalAliases(false) {
1377 initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
1380 bool runOnModule(Module &M) override;
1383 // The function comparison operator is provided here so that FunctionNodes do
1384 // not need to become larger with another pointer.
1385 class FunctionNodeCmp {
1386 GlobalNumberState* GlobalNumbers;
1388 FunctionNodeCmp(GlobalNumberState* GN) : GlobalNumbers(GN) {}
1389 bool operator()(const FunctionNode &LHS, const FunctionNode &RHS) const {
1390 // Order first by hashes, then full function comparison.
1391 if (LHS.getHash() != RHS.getHash())
1392 return LHS.getHash() < RHS.getHash();
1393 FunctionComparator FCmp(LHS.getFunc(), RHS.getFunc(), GlobalNumbers);
1394 return FCmp.compare() == -1;
1397 typedef std::set<FunctionNode, FunctionNodeCmp> FnTreeType;
1399 GlobalNumberState GlobalNumbers;
1401 /// A work queue of functions that may have been modified and should be
1403 std::vector<WeakVH> Deferred;
1405 /// Checks the rules of order relation introduced among functions set.
1406 /// Returns true, if sanity check has been passed, and false if failed.
1407 bool doSanityCheck(std::vector<WeakVH> &Worklist);
1409 /// Insert a ComparableFunction into the FnTree, or merge it away if it's
1410 /// equal to one that's already present.
1411 bool insert(Function *NewFunction);
1413 /// Remove a Function from the FnTree and queue it up for a second sweep of
1415 void remove(Function *F);
1417 /// Find the functions that use this Value and remove them from FnTree and
1418 /// queue the functions.
1419 void removeUsers(Value *V);
1421 /// Replace all direct calls of Old with calls of New. Will bitcast New if
1422 /// necessary to make types match.
1423 void replaceDirectCallers(Function *Old, Function *New);
1425 /// Merge two equivalent functions. Upon completion, G may be deleted, or may
1426 /// be converted into a thunk. In either case, it should never be visited
1428 void mergeTwoFunctions(Function *F, Function *G);
1430 /// Replace G with a thunk or an alias to F. Deletes G.
1431 void writeThunkOrAlias(Function *F, Function *G);
1433 /// Replace G with a simple tail call to bitcast(F). Also replace direct uses
1434 /// of G with bitcast(F). Deletes G.
1435 void writeThunk(Function *F, Function *G);
1437 /// Replace G with an alias to F. Deletes G.
1438 void writeAlias(Function *F, Function *G);
1440 /// Replace function F with function G in the function tree.
1441 void replaceFunctionInTree(const FunctionNode &FN, Function *G);
1443 /// The set of all distinct functions. Use the insert() and remove() methods
1444 /// to modify it. The map allows efficient lookup and deferring of Functions.
1446 // Map functions to the iterators of the FunctionNode which contains them
1447 // in the FnTree. This must be updated carefully whenever the FnTree is
1448 // modified, i.e. in insert(), remove(), and replaceFunctionInTree(), to avoid
1449 // dangling iterators into FnTree. The invariant that preserves this is that
1450 // there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
1451 ValueMap<Function*, FnTreeType::iterator> FNodesInTree;
1453 /// Whether or not the target supports global aliases.
1454 bool HasGlobalAliases;
1457 } // end anonymous namespace
1459 char MergeFunctions::ID = 0;
1460 INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
1462 ModulePass *llvm::createMergeFunctionsPass() {
1463 return new MergeFunctions();
1466 bool MergeFunctions::doSanityCheck(std::vector<WeakVH> &Worklist) {
1467 if (const unsigned Max = NumFunctionsForSanityCheck) {
1468 unsigned TripleNumber = 0;
1471 dbgs() << "MERGEFUNC-SANITY: Started for first " << Max << " functions.\n";
1474 for (std::vector<WeakVH>::iterator I = Worklist.begin(), E = Worklist.end();
1475 I != E && i < Max; ++I, ++i) {
1477 for (std::vector<WeakVH>::iterator J = I; J != E && j < Max; ++J, ++j) {
1478 Function *F1 = cast<Function>(*I);
1479 Function *F2 = cast<Function>(*J);
1480 int Res1 = FunctionComparator(F1, F2, &GlobalNumbers).compare();
1481 int Res2 = FunctionComparator(F2, F1, &GlobalNumbers).compare();
1483 // If F1 <= F2, then F2 >= F1, otherwise report failure.
1484 if (Res1 != -Res2) {
1485 dbgs() << "MERGEFUNC-SANITY: Non-symmetric; triple: " << TripleNumber
1496 for (std::vector<WeakVH>::iterator K = J; K != E && k < Max;
1497 ++k, ++K, ++TripleNumber) {
1501 Function *F3 = cast<Function>(*K);
1502 int Res3 = FunctionComparator(F1, F3, &GlobalNumbers).compare();
1503 int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).compare();
1505 bool Transitive = true;
1507 if (Res1 != 0 && Res1 == Res4) {
1508 // F1 > F2, F2 > F3 => F1 > F3
1509 Transitive = Res3 == Res1;
1510 } else if (Res3 != 0 && Res3 == -Res4) {
1511 // F1 > F3, F3 > F2 => F1 > F2
1512 Transitive = Res3 == Res1;
1513 } else if (Res4 != 0 && -Res3 == Res4) {
1514 // F2 > F3, F3 > F1 => F2 > F1
1515 Transitive = Res4 == -Res1;
1519 dbgs() << "MERGEFUNC-SANITY: Non-transitive; triple: "
1520 << TripleNumber << "\n";
1521 dbgs() << "Res1, Res3, Res4: " << Res1 << ", " << Res3 << ", "
1532 dbgs() << "MERGEFUNC-SANITY: " << (Valid ? "Passed." : "Failed.") << "\n";
1538 bool MergeFunctions::runOnModule(Module &M) {
1542 bool Changed = false;
1544 // All functions in the module, ordered by hash. Functions with a unique
1545 // hash value are easily eliminated.
1546 std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
1548 for (Function &Func : M) {
1549 if (!Func.isDeclaration() && !Func.hasAvailableExternallyLinkage()) {
1550 HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
1555 HashedFuncs.begin(), HashedFuncs.end(),
1556 [](const std::pair<FunctionComparator::FunctionHash, Function *> &a,
1557 const std::pair<FunctionComparator::FunctionHash, Function *> &b) {
1558 return a.first < b.first;
1561 auto S = HashedFuncs.begin();
1562 for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
1563 // If the hash value matches the previous value or the next one, we must
1564 // consider merging it. Otherwise it is dropped and never considered again.
1565 if ((I != S && std::prev(I)->first == I->first) ||
1566 (std::next(I) != IE && std::next(I)->first == I->first) ) {
1567 Deferred.push_back(WeakVH(I->second));
1572 std::vector<WeakVH> Worklist;
1573 Deferred.swap(Worklist);
1575 DEBUG(doSanityCheck(Worklist));
1577 DEBUG(dbgs() << "size of module: " << M.size() << '\n');
1578 DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
1580 // Insert functions and merge them.
1581 for (WeakVH &I : Worklist) {
1584 Function *F = cast<Function>(I);
1585 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage()) {
1586 Changed |= insert(F);
1589 DEBUG(dbgs() << "size of FnTree: " << FnTree.size() << '\n');
1590 } while (!Deferred.empty());
1593 GlobalNumbers.clear();
1598 // Replace direct callers of Old with New.
1599 void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
1600 Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
1601 for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
1604 CallSite CS(U->getUser());
1605 if (CS && CS.isCallee(U)) {
1606 // Transfer the called function's attributes to the call site. Due to the
1607 // bitcast we will 'lose' ABI changing attributes because the 'called
1608 // function' is no longer a Function* but the bitcast. Code that looks up
1609 // the attributes from the called function will fail.
1611 // FIXME: This is not actually true, at least not anymore. The callsite
1612 // will always have the same ABI affecting attributes as the callee,
1613 // because otherwise the original input has UB. Note that Old and New
1614 // always have matching ABI, so no attributes need to be changed.
1615 // Transferring other attributes may help other optimizations, but that
1616 // should be done uniformly and not in this ad-hoc way.
1617 auto &Context = New->getContext();
1618 auto NewFuncAttrs = New->getAttributes();
1619 auto CallSiteAttrs = CS.getAttributes();
1621 CallSiteAttrs = CallSiteAttrs.addAttributes(
1622 Context, AttributeSet::ReturnIndex, NewFuncAttrs.getRetAttributes());
1624 for (unsigned argIdx = 0; argIdx < CS.arg_size(); argIdx++) {
1625 AttributeSet Attrs = NewFuncAttrs.getParamAttributes(argIdx);
1626 if (Attrs.getNumSlots())
1627 CallSiteAttrs = CallSiteAttrs.addAttributes(Context, argIdx, Attrs);
1630 CS.setAttributes(CallSiteAttrs);
1632 remove(CS.getInstruction()->getParent()->getParent());
1638 // Replace G with an alias to F if possible, or else a thunk to F. Deletes G.
1639 void MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
1640 if (HasGlobalAliases && G->hasGlobalUnnamedAddr()) {
1641 if (G->hasExternalLinkage() || G->hasLocalLinkage() ||
1642 G->hasWeakLinkage()) {
1651 // Helper for writeThunk,
1652 // Selects proper bitcast operation,
1653 // but a bit simpler then CastInst::getCastOpcode.
1654 static Value *createCast(IRBuilder<> &Builder, Value *V, Type *DestTy) {
1655 Type *SrcTy = V->getType();
1656 if (SrcTy->isStructTy()) {
1657 assert(DestTy->isStructTy());
1658 assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements());
1659 Value *Result = UndefValue::get(DestTy);
1660 for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) {
1661 Value *Element = createCast(
1662 Builder, Builder.CreateExtractValue(V, makeArrayRef(I)),
1663 DestTy->getStructElementType(I));
1666 Builder.CreateInsertValue(Result, Element, makeArrayRef(I));
1670 assert(!DestTy->isStructTy());
1671 if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
1672 return Builder.CreateIntToPtr(V, DestTy);
1673 else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
1674 return Builder.CreatePtrToInt(V, DestTy);
1676 return Builder.CreateBitCast(V, DestTy);
1679 // Replace G with a simple tail call to bitcast(F). Also replace direct uses
1680 // of G with bitcast(F). Deletes G.
1681 void MergeFunctions::writeThunk(Function *F, Function *G) {
1682 if (!G->isInterposable()) {
1683 // Redirect direct callers of G to F.
1684 replaceDirectCallers(G, F);
1687 // If G was internal then we may have replaced all uses of G with F. If so,
1688 // stop here and delete G. There's no need for a thunk.
1689 if (G->hasLocalLinkage() && G->use_empty()) {
1690 G->eraseFromParent();
1694 Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
1696 BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
1697 IRBuilder<> Builder(BB);
1699 SmallVector<Value *, 16> Args;
1701 FunctionType *FFTy = F->getFunctionType();
1702 for (Argument & AI : NewG->args()) {
1703 Args.push_back(createCast(Builder, &AI, FFTy->getParamType(i)));
1707 CallInst *CI = Builder.CreateCall(F, Args);
1709 CI->setCallingConv(F->getCallingConv());
1710 CI->setAttributes(F->getAttributes());
1711 if (NewG->getReturnType()->isVoidTy()) {
1712 Builder.CreateRetVoid();
1714 Builder.CreateRet(createCast(Builder, CI, NewG->getReturnType()));
1717 NewG->copyAttributesFrom(G);
1720 G->replaceAllUsesWith(NewG);
1721 G->eraseFromParent();
1723 DEBUG(dbgs() << "writeThunk: " << NewG->getName() << '\n');
1727 // Replace G with an alias to F and delete G.
1728 void MergeFunctions::writeAlias(Function *F, Function *G) {
1729 auto *GA = GlobalAlias::create(G->getLinkage(), "", F);
1730 F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
1732 GA->setVisibility(G->getVisibility());
1734 G->replaceAllUsesWith(GA);
1735 G->eraseFromParent();
1737 DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n');
1738 ++NumAliasesWritten;
1741 // Merge two equivalent functions. Upon completion, Function G is deleted.
1742 void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
1743 if (F->isInterposable()) {
1744 assert(G->isInterposable());
1746 // Make them both thunks to the same internal function.
1747 Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
1749 H->copyAttributesFrom(F);
1752 F->replaceAllUsesWith(H);
1754 unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
1756 if (HasGlobalAliases) {
1764 F->setAlignment(MaxAlignment);
1765 F->setLinkage(GlobalValue::PrivateLinkage);
1768 writeThunkOrAlias(F, G);
1771 ++NumFunctionsMerged;
1774 /// Replace function F by function G.
1775 void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
1777 Function *F = FN.getFunc();
1778 assert(FunctionComparator(F, G, &GlobalNumbers).compare() == 0 &&
1779 "The two functions must be equal");
1781 auto I = FNodesInTree.find(F);
1782 assert(I != FNodesInTree.end() && "F should be in FNodesInTree");
1783 assert(FNodesInTree.count(G) == 0 && "FNodesInTree should not contain G");
1785 FnTreeType::iterator IterToFNInFnTree = I->second;
1786 assert(&(*IterToFNInFnTree) == &FN && "F should map to FN in FNodesInTree.");
1787 // Remove F -> FN and insert G -> FN
1788 FNodesInTree.erase(I);
1789 FNodesInTree.insert({G, IterToFNInFnTree});
1790 // Replace F with G in FN, which is stored inside the FnTree.
1794 // Insert a ComparableFunction into the FnTree, or merge it away if equal to one
1795 // that was already inserted.
1796 bool MergeFunctions::insert(Function *NewFunction) {
1797 std::pair<FnTreeType::iterator, bool> Result =
1798 FnTree.insert(FunctionNode(NewFunction));
1800 if (Result.second) {
1801 assert(FNodesInTree.count(NewFunction) == 0);
1802 FNodesInTree.insert({NewFunction, Result.first});
1803 DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName() << '\n');
1807 const FunctionNode &OldF = *Result.first;
1809 // Don't merge tiny functions, since it can just end up making the function
1811 // FIXME: Should still merge them if they are unnamed_addr and produce an
1813 if (NewFunction->size() == 1) {
1814 if (NewFunction->front().size() <= 2) {
1815 DEBUG(dbgs() << NewFunction->getName()
1816 << " is to small to bother merging\n");
1821 // Impose a total order (by name) on the replacement of functions. This is
1822 // important when operating on more than one module independently to prevent
1823 // cycles of thunks calling each other when the modules are linked together.
1825 // First of all, we process strong functions before weak functions.
1826 if ((OldF.getFunc()->isInterposable() && !NewFunction->isInterposable()) ||
1827 (OldF.getFunc()->isInterposable() == NewFunction->isInterposable() &&
1828 OldF.getFunc()->getName() > NewFunction->getName())) {
1829 // Swap the two functions.
1830 Function *F = OldF.getFunc();
1831 replaceFunctionInTree(*Result.first, NewFunction);
1833 assert(OldF.getFunc() != F && "Must have swapped the functions.");
1836 DEBUG(dbgs() << " " << OldF.getFunc()->getName()
1837 << " == " << NewFunction->getName() << '\n');
1839 Function *DeleteF = NewFunction;
1840 mergeTwoFunctions(OldF.getFunc(), DeleteF);
1844 // Remove a function from FnTree. If it was already in FnTree, add
1845 // it to Deferred so that we'll look at it in the next round.
1846 void MergeFunctions::remove(Function *F) {
1847 auto I = FNodesInTree.find(F);
1848 if (I != FNodesInTree.end()) {
1849 DEBUG(dbgs() << "Deferred " << F->getName()<< ".\n");
1850 FnTree.erase(I->second);
1851 // I->second has been invalidated, remove it from the FNodesInTree map to
1852 // preserve the invariant.
1853 FNodesInTree.erase(I);
1854 Deferred.emplace_back(F);
1858 // For each instruction used by the value, remove() the function that contains
1859 // the instruction. This should happen right before a call to RAUW.
1860 void MergeFunctions::removeUsers(Value *V) {
1861 std::vector<Value *> Worklist;
1862 Worklist.push_back(V);
1863 SmallSet<Value*, 8> Visited;
1865 while (!Worklist.empty()) {
1866 Value *V = Worklist.back();
1867 Worklist.pop_back();
1869 for (User *U : V->users()) {
1870 if (Instruction *I = dyn_cast<Instruction>(U)) {
1871 remove(I->getParent()->getParent());
1872 } else if (isa<GlobalValue>(U)) {
1874 } else if (Constant *C = dyn_cast<Constant>(U)) {
1875 for (User *UU : C->users()) {
1876 if (!Visited.insert(UU).second)
1877 Worklist.push_back(UU);