Bug Summary

File:llvm/lib/Transforms/IPO/MergeFunctions.cpp
Warning:line 710, column 23
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name MergeFunctions.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=none -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-11/lib/clang/11.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/Transforms/IPO -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/include -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-11/lib/clang/11.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/Transforms/IPO -fdebug-prefix-map=/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-03-09-184146-41876-1 -x c++ /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp
1//===- MergeFunctions.cpp - Merge identical functions ---------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This pass looks for equivalent functions that are mergable and folds them.
10//
11// Order relation is defined on set of functions. It was made through
12// special function comparison procedure that returns
13// 0 when functions are equal,
14// -1 when Left function is less than right function, and
15// 1 for opposite case. We need total-ordering, so we need to maintain
16// four properties on the functions set:
17// a <= a (reflexivity)
18// if a <= b and b <= a then a = b (antisymmetry)
19// if a <= b and b <= c then a <= c (transitivity).
20// for all a and b: a <= b or b <= a (totality).
21//
22// Comparison iterates through each instruction in each basic block.
23// Functions are kept on binary tree. For each new function F we perform
24// lookup in binary tree.
25// In practice it works the following way:
26// -- We define Function* container class with custom "operator<" (FunctionPtr).
27// -- "FunctionPtr" instances are stored in std::set collection, so every
28// std::set::insert operation will give you result in log(N) time.
29//
30// As an optimization, a hash of the function structure is calculated first, and
31// two functions are only compared if they have the same hash. This hash is
32// cheap to compute, and has the property that if function F == G according to
33// the comparison function, then hash(F) == hash(G). This consistency property
34// is critical to ensuring all possible merging opportunities are exploited.
35// Collisions in the hash affect the speed of the pass but not the correctness
36// or determinism of the resulting transformation.
37//
38// When a match is found the functions are folded. If both functions are
39// overridable, we move the functionality into a new internal function and
40// leave two overridable thunks to it.
41//
42//===----------------------------------------------------------------------===//
43//
44// Future work:
45//
46// * virtual functions.
47//
48// Many functions have their address taken by the virtual function table for
49// the object they belong to. However, as long as it's only used for a lookup
50// and call, this is irrelevant, and we'd like to fold such functions.
51//
52// * be smarter about bitcasts.
53//
54// In order to fold functions, we will sometimes add either bitcast instructions
55// or bitcast constant expressions. Unfortunately, this can confound further
56// analysis since the two functions differ where one has a bitcast and the
57// other doesn't. We should learn to look through bitcasts.
58//
59// * Compare complex types with pointer types inside.
60// * Compare cross-reference cases.
61// * Compare complex expressions.
62//
63// All the three issues above could be described as ability to prove that
64// fA == fB == fC == fE == fF == fG in example below:
65//
66// void fA() {
67// fB();
68// }
69// void fB() {
70// fA();
71// }
72//
73// void fE() {
74// fF();
75// }
76// void fF() {
77// fG();
78// }
79// void fG() {
80// fE();
81// }
82//
83// Simplest cross-reference case (fA <--> fB) was implemented in previous
84// versions of MergeFunctions, though it presented only in two function pairs
85// in test-suite (that counts >50k functions)
86// Though possibility to detect complex cross-referencing (e.g.: A->B->C->D->A)
87// could cover much more cases.
88//
89//===----------------------------------------------------------------------===//
90
91#include "llvm/ADT/ArrayRef.h"
92#include "llvm/ADT/SmallPtrSet.h"
93#include "llvm/ADT/SmallVector.h"
94#include "llvm/ADT/Statistic.h"
95#include "llvm/IR/Argument.h"
96#include "llvm/IR/Attributes.h"
97#include "llvm/IR/BasicBlock.h"
98#include "llvm/IR/CallSite.h"
99#include "llvm/IR/Constant.h"
100#include "llvm/IR/Constants.h"
101#include "llvm/IR/DebugInfoMetadata.h"
102#include "llvm/IR/DebugLoc.h"
103#include "llvm/IR/DerivedTypes.h"
104#include "llvm/IR/Function.h"
105#include "llvm/IR/GlobalValue.h"
106#include "llvm/IR/IRBuilder.h"
107#include "llvm/IR/InstrTypes.h"
108#include "llvm/IR/Instruction.h"
109#include "llvm/IR/Instructions.h"
110#include "llvm/IR/IntrinsicInst.h"
111#include "llvm/IR/Module.h"
112#include "llvm/IR/Type.h"
113#include "llvm/IR/Use.h"
114#include "llvm/IR/User.h"
115#include "llvm/IR/Value.h"
116#include "llvm/IR/ValueHandle.h"
117#include "llvm/IR/ValueMap.h"
118#include "llvm/InitializePasses.h"
119#include "llvm/Pass.h"
120#include "llvm/Support/Casting.h"
121#include "llvm/Support/CommandLine.h"
122#include "llvm/Support/Debug.h"
123#include "llvm/Support/raw_ostream.h"
124#include "llvm/Transforms/IPO.h"
125#include "llvm/Transforms/IPO/MergeFunctions.h"
126#include "llvm/Transforms/Utils/FunctionComparator.h"
127#include <algorithm>
128#include <cassert>
129#include <iterator>
130#include <set>
131#include <utility>
132#include <vector>
133
134using namespace llvm;
135
136#define DEBUG_TYPE"mergefunc" "mergefunc"
137
138STATISTIC(NumFunctionsMerged, "Number of functions merged")static llvm::Statistic NumFunctionsMerged = {"mergefunc", "NumFunctionsMerged"
, "Number of functions merged"}
;
139STATISTIC(NumThunksWritten, "Number of thunks generated")static llvm::Statistic NumThunksWritten = {"mergefunc", "NumThunksWritten"
, "Number of thunks generated"}
;
140STATISTIC(NumAliasesWritten, "Number of aliases generated")static llvm::Statistic NumAliasesWritten = {"mergefunc", "NumAliasesWritten"
, "Number of aliases generated"}
;
141STATISTIC(NumDoubleWeak, "Number of new functions created")static llvm::Statistic NumDoubleWeak = {"mergefunc", "NumDoubleWeak"
, "Number of new functions created"}
;
142
143static cl::opt<unsigned> NumFunctionsForSanityCheck(
144 "mergefunc-sanity",
145 cl::desc("How many functions in module could be used for "
146 "MergeFunctions pass sanity check. "
147 "'0' disables this check. Works only with '-debug' key."),
148 cl::init(0), cl::Hidden);
149
150// Under option -mergefunc-preserve-debug-info we:
151// - Do not create a new function for a thunk.
152// - Retain the debug info for a thunk's parameters (and associated
153// instructions for the debug info) from the entry block.
154// Note: -debug will display the algorithm at work.
155// - Create debug-info for the call (to the shared implementation) made by
156// a thunk and its return value.
157// - Erase the rest of the function, retaining the (minimally sized) entry
158// block to create a thunk.
159// - Preserve a thunk's call site to point to the thunk even when both occur
160// within the same translation unit, to aid debugability. Note that this
161// behaviour differs from the underlying -mergefunc implementation which
162// modifies the thunk's call site to point to the shared implementation
163// when both occur within the same translation unit.
164static cl::opt<bool>
165 MergeFunctionsPDI("mergefunc-preserve-debug-info", cl::Hidden,
166 cl::init(false),
167 cl::desc("Preserve debug info in thunk when mergefunc "
168 "transformations are made."));
169
170static cl::opt<bool>
171 MergeFunctionsAliases("mergefunc-use-aliases", cl::Hidden,
172 cl::init(false),
173 cl::desc("Allow mergefunc to create aliases"));
174
175namespace {
176
177class FunctionNode {
178 mutable AssertingVH<Function> F;
179 FunctionComparator::FunctionHash Hash;
180
181public:
182 // Note the hash is recalculated potentially multiple times, but it is cheap.
183 FunctionNode(Function *F)
184 : F(F), Hash(FunctionComparator::functionHash(*F)) {}
185
186 Function *getFunc() const { return F; }
187 FunctionComparator::FunctionHash getHash() const { return Hash; }
188
189 /// Replace the reference to the function F by the function G, assuming their
190 /// implementations are equal.
191 void replaceBy(Function *G) const {
192 F = G;
193 }
194};
195
196/// MergeFunctions finds functions which will generate identical machine code,
197/// by considering all pointer types to be equivalent. Once identified,
198/// MergeFunctions will fold them by replacing a call to one to a call to a
199/// bitcast of the other.
200class MergeFunctions {
201public:
202 MergeFunctions() : FnTree(FunctionNodeCmp(&GlobalNumbers)) {
203 }
204
205 bool runOnModule(Module &M);
206
207private:
208 // The function comparison operator is provided here so that FunctionNodes do
209 // not need to become larger with another pointer.
210 class FunctionNodeCmp {
211 GlobalNumberState* GlobalNumbers;
212
213 public:
214 FunctionNodeCmp(GlobalNumberState* GN) : GlobalNumbers(GN) {}
215
216 bool operator()(const FunctionNode &LHS, const FunctionNode &RHS) const {
217 // Order first by hashes, then full function comparison.
218 if (LHS.getHash() != RHS.getHash())
219 return LHS.getHash() < RHS.getHash();
220 FunctionComparator FCmp(LHS.getFunc(), RHS.getFunc(), GlobalNumbers);
221 return FCmp.compare() == -1;
222 }
223 };
224 using FnTreeType = std::set<FunctionNode, FunctionNodeCmp>;
225
226 GlobalNumberState GlobalNumbers;
227
228 /// A work queue of functions that may have been modified and should be
229 /// analyzed again.
230 std::vector<WeakTrackingVH> Deferred;
231
232#ifndef NDEBUG
233 /// Checks the rules of order relation introduced among functions set.
234 /// Returns true, if sanity check has been passed, and false if failed.
235 bool doSanityCheck(std::vector<WeakTrackingVH> &Worklist);
236#endif
237
238 /// Insert a ComparableFunction into the FnTree, or merge it away if it's
239 /// equal to one that's already present.
240 bool insert(Function *NewFunction);
241
242 /// Remove a Function from the FnTree and queue it up for a second sweep of
243 /// analysis.
244 void remove(Function *F);
245
246 /// Find the functions that use this Value and remove them from FnTree and
247 /// queue the functions.
248 void removeUsers(Value *V);
249
250 /// Replace all direct calls of Old with calls of New. Will bitcast New if
251 /// necessary to make types match.
252 void replaceDirectCallers(Function *Old, Function *New);
253
254 /// Merge two equivalent functions. Upon completion, G may be deleted, or may
255 /// be converted into a thunk. In either case, it should never be visited
256 /// again.
257 void mergeTwoFunctions(Function *F, Function *G);
258
259 /// Fill PDIUnrelatedWL with instructions from the entry block that are
260 /// unrelated to parameter related debug info.
261 void filterInstsUnrelatedToPDI(BasicBlock *GEntryBlock,
262 std::vector<Instruction *> &PDIUnrelatedWL);
263
264 /// Erase the rest of the CFG (i.e. barring the entry block).
265 void eraseTail(Function *G);
266
267 /// Erase the instructions in PDIUnrelatedWL as they are unrelated to the
268 /// parameter debug info, from the entry block.
269 void eraseInstsUnrelatedToPDI(std::vector<Instruction *> &PDIUnrelatedWL);
270
271 /// Replace G with a simple tail call to bitcast(F). Also (unless
272 /// MergeFunctionsPDI holds) replace direct uses of G with bitcast(F),
273 /// delete G.
274 void writeThunk(Function *F, Function *G);
275
276 // Replace G with an alias to F (deleting function G)
277 void writeAlias(Function *F, Function *G);
278
279 // Replace G with an alias to F if possible, or a thunk to F if possible.
280 // Returns false if neither is the case.
281 bool writeThunkOrAlias(Function *F, Function *G);
282
283 /// Replace function F with function G in the function tree.
284 void replaceFunctionInTree(const FunctionNode &FN, Function *G);
285
286 /// The set of all distinct functions. Use the insert() and remove() methods
287 /// to modify it. The map allows efficient lookup and deferring of Functions.
288 FnTreeType FnTree;
289
290 // Map functions to the iterators of the FunctionNode which contains them
291 // in the FnTree. This must be updated carefully whenever the FnTree is
292 // modified, i.e. in insert(), remove(), and replaceFunctionInTree(), to avoid
293 // dangling iterators into FnTree. The invariant that preserves this is that
294 // there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
295 DenseMap<AssertingVH<Function>, FnTreeType::iterator> FNodesInTree;
296};
297
298class MergeFunctionsLegacyPass : public ModulePass {
299public:
300 static char ID;
301
302 MergeFunctionsLegacyPass(): ModulePass(ID) {
303 initializeMergeFunctionsLegacyPassPass(*PassRegistry::getPassRegistry());
304 }
305
306 bool runOnModule(Module &M) override {
307 if (skipModule(M))
308 return false;
309
310 MergeFunctions MF;
311 return MF.runOnModule(M);
312 }
313};
314
315} // end anonymous namespace
316
317char MergeFunctionsLegacyPass::ID = 0;
318INITIALIZE_PASS(MergeFunctionsLegacyPass, "mergefunc",static void *initializeMergeFunctionsLegacyPassPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "Merge Functions"
, "mergefunc", &MergeFunctionsLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MergeFunctionsLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeMergeFunctionsLegacyPassPassFlag; void llvm
::initializeMergeFunctionsLegacyPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeMergeFunctionsLegacyPassPassFlag
, initializeMergeFunctionsLegacyPassPassOnce, std::ref(Registry
)); }
319 "Merge Functions", false, false)static void *initializeMergeFunctionsLegacyPassPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "Merge Functions"
, "mergefunc", &MergeFunctionsLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MergeFunctionsLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeMergeFunctionsLegacyPassPassFlag; void llvm
::initializeMergeFunctionsLegacyPassPass(PassRegistry &Registry
) { llvm::call_once(InitializeMergeFunctionsLegacyPassPassFlag
, initializeMergeFunctionsLegacyPassPassOnce, std::ref(Registry
)); }
320
321ModulePass *llvm::createMergeFunctionsPass() {
322 return new MergeFunctionsLegacyPass();
323}
324
325PreservedAnalyses MergeFunctionsPass::run(Module &M,
326 ModuleAnalysisManager &AM) {
327 MergeFunctions MF;
328 if (!MF.runOnModule(M))
329 return PreservedAnalyses::all();
330 return PreservedAnalyses::none();
331}
332
333#ifndef NDEBUG
334bool MergeFunctions::doSanityCheck(std::vector<WeakTrackingVH> &Worklist) {
335 if (const unsigned Max = NumFunctionsForSanityCheck) {
336 unsigned TripleNumber = 0;
337 bool Valid = true;
338
339 dbgs() << "MERGEFUNC-SANITY: Started for first " << Max << " functions.\n";
340
341 unsigned i = 0;
342 for (std::vector<WeakTrackingVH>::iterator I = Worklist.begin(),
343 E = Worklist.end();
344 I != E && i < Max; ++I, ++i) {
345 unsigned j = i;
346 for (std::vector<WeakTrackingVH>::iterator J = I; J != E && j < Max;
347 ++J, ++j) {
348 Function *F1 = cast<Function>(*I);
349 Function *F2 = cast<Function>(*J);
350 int Res1 = FunctionComparator(F1, F2, &GlobalNumbers).compare();
351 int Res2 = FunctionComparator(F2, F1, &GlobalNumbers).compare();
352
353 // If F1 <= F2, then F2 >= F1, otherwise report failure.
354 if (Res1 != -Res2) {
355 dbgs() << "MERGEFUNC-SANITY: Non-symmetric; triple: " << TripleNumber
356 << "\n";
357 dbgs() << *F1 << '\n' << *F2 << '\n';
358 Valid = false;
359 }
360
361 if (Res1 == 0)
362 continue;
363
364 unsigned k = j;
365 for (std::vector<WeakTrackingVH>::iterator K = J; K != E && k < Max;
366 ++k, ++K, ++TripleNumber) {
367 if (K == J)
368 continue;
369
370 Function *F3 = cast<Function>(*K);
371 int Res3 = FunctionComparator(F1, F3, &GlobalNumbers).compare();
372 int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).compare();
373
374 bool Transitive = true;
375
376 if (Res1 != 0 && Res1 == Res4) {
377 // F1 > F2, F2 > F3 => F1 > F3
378 Transitive = Res3 == Res1;
379 } else if (Res3 != 0 && Res3 == -Res4) {
380 // F1 > F3, F3 > F2 => F1 > F2
381 Transitive = Res3 == Res1;
382 } else if (Res4 != 0 && -Res3 == Res4) {
383 // F2 > F3, F3 > F1 => F2 > F1
384 Transitive = Res4 == -Res1;
385 }
386
387 if (!Transitive) {
388 dbgs() << "MERGEFUNC-SANITY: Non-transitive; triple: "
389 << TripleNumber << "\n";
390 dbgs() << "Res1, Res3, Res4: " << Res1 << ", " << Res3 << ", "
391 << Res4 << "\n";
392 dbgs() << *F1 << '\n' << *F2 << '\n' << *F3 << '\n';
393 Valid = false;
394 }
395 }
396 }
397 }
398
399 dbgs() << "MERGEFUNC-SANITY: " << (Valid ? "Passed." : "Failed.") << "\n";
400 return Valid;
401 }
402 return true;
403}
404#endif
405
406/// Check whether \p F is eligible for function merging.
407static bool isEligibleForMerging(Function &F) {
408 return !F.isDeclaration() && !F.hasAvailableExternallyLinkage();
409}
410
411bool MergeFunctions::runOnModule(Module &M) {
412 bool Changed = false;
413
414 // All functions in the module, ordered by hash. Functions with a unique
415 // hash value are easily eliminated.
416 std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
417 HashedFuncs;
418 for (Function &Func : M) {
419 if (isEligibleForMerging(Func)) {
420 HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
421 }
422 }
423
424 llvm::stable_sort(HashedFuncs, less_first());
425
426 auto S = HashedFuncs.begin();
427 for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
428 // If the hash value matches the previous value or the next one, we must
429 // consider merging it. Otherwise it is dropped and never considered again.
430 if ((I != S && std::prev(I)->first == I->first) ||
431 (std::next(I) != IE && std::next(I)->first == I->first) ) {
432 Deferred.push_back(WeakTrackingVH(I->second));
433 }
434 }
435
436 do {
437 std::vector<WeakTrackingVH> Worklist;
438 Deferred.swap(Worklist);
439
440 LLVM_DEBUG(doSanityCheck(Worklist))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { doSanityCheck(Worklist); } } while (false)
;
441
442 LLVM_DEBUG(dbgs() << "size of module: " << M.size() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "size of module: " << M
.size() << '\n'; } } while (false)
;
443 LLVM_DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "size of worklist: " <<
Worklist.size() << '\n'; } } while (false)
;
444
445 // Insert functions and merge them.
446 for (WeakTrackingVH &I : Worklist) {
447 if (!I)
448 continue;
449 Function *F = cast<Function>(I);
450 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage()) {
451 Changed |= insert(F);
452 }
453 }
454 LLVM_DEBUG(dbgs() << "size of FnTree: " << FnTree.size() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "size of FnTree: " << FnTree
.size() << '\n'; } } while (false)
;
455 } while (!Deferred.empty());
456
457 FnTree.clear();
458 FNodesInTree.clear();
459 GlobalNumbers.clear();
460
461 return Changed;
462}
463
464// Replace direct callers of Old with New.
465void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
466 Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
467 for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
468 Use *U = &*UI;
469 ++UI;
470 CallSite CS(U->getUser());
471 if (CS && CS.isCallee(U)) {
472 // Do not copy attributes from the called function to the call-site.
473 // Function comparison ensures that the attributes are the same up to
474 // type congruences in byval(), in which case we need to keep the byval
475 // type of the call-site, not the callee function.
476 remove(CS.getInstruction()->getFunction());
477 U->set(BitcastNew);
478 }
479 }
480}
481
482// Helper for writeThunk,
483// Selects proper bitcast operation,
484// but a bit simpler then CastInst::getCastOpcode.
485static Value *createCast(IRBuilder<> &Builder, Value *V, Type *DestTy) {
486 Type *SrcTy = V->getType();
487 if (SrcTy->isStructTy()) {
488 assert(DestTy->isStructTy())((DestTy->isStructTy()) ? static_cast<void> (0) : __assert_fail
("DestTy->isStructTy()", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 488, __PRETTY_FUNCTION__))
;
489 assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements())((SrcTy->getStructNumElements() == DestTy->getStructNumElements
()) ? static_cast<void> (0) : __assert_fail ("SrcTy->getStructNumElements() == DestTy->getStructNumElements()"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 489, __PRETTY_FUNCTION__))
;
490 Value *Result = UndefValue::get(DestTy);
491 for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) {
492 Value *Element = createCast(
493 Builder, Builder.CreateExtractValue(V, makeArrayRef(I)),
494 DestTy->getStructElementType(I));
495
496 Result =
497 Builder.CreateInsertValue(Result, Element, makeArrayRef(I));
498 }
499 return Result;
500 }
501 assert(!DestTy->isStructTy())((!DestTy->isStructTy()) ? static_cast<void> (0) : __assert_fail
("!DestTy->isStructTy()", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 501, __PRETTY_FUNCTION__))
;
502 if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
503 return Builder.CreateIntToPtr(V, DestTy);
504 else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
505 return Builder.CreatePtrToInt(V, DestTy);
506 else
507 return Builder.CreateBitCast(V, DestTy);
508}
509
510// Erase the instructions in PDIUnrelatedWL as they are unrelated to the
511// parameter debug info, from the entry block.
512void MergeFunctions::eraseInstsUnrelatedToPDI(
513 std::vector<Instruction *> &PDIUnrelatedWL) {
514 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Erasing instructions (in reverse order of appearance in "
"entry block) unrelated to parameter debug info from entry "
"block: {\n"; } } while (false)
515 dbgs() << " Erasing instructions (in reverse order of appearance in "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Erasing instructions (in reverse order of appearance in "
"entry block) unrelated to parameter debug info from entry "
"block: {\n"; } } while (false)
516 "entry block) unrelated to parameter debug info from entry "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Erasing instructions (in reverse order of appearance in "
"entry block) unrelated to parameter debug info from entry "
"block: {\n"; } } while (false)
517 "block: {\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Erasing instructions (in reverse order of appearance in "
"entry block) unrelated to parameter debug info from entry "
"block: {\n"; } } while (false)
;
518 while (!PDIUnrelatedWL.empty()) {
519 Instruction *I = PDIUnrelatedWL.back();
520 LLVM_DEBUG(dbgs() << " Deleting Instruction: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deleting Instruction: "; }
} while (false)
;
521 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false)
;
522 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
523 I->eraseFromParent();
524 PDIUnrelatedWL.pop_back();
525 }
526 LLVM_DEBUG(dbgs() << " } // Done erasing instructions unrelated to parameter "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " } // Done erasing instructions unrelated to parameter "
"debug info from entry block. \n"; } } while (false)
527 "debug info from entry block. \n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " } // Done erasing instructions unrelated to parameter "
"debug info from entry block. \n"; } } while (false)
;
528}
529
530// Reduce G to its entry block.
531void MergeFunctions::eraseTail(Function *G) {
532 std::vector<BasicBlock *> WorklistBB;
533 for (Function::iterator BBI = std::next(G->begin()), BBE = G->end();
534 BBI != BBE; ++BBI) {
535 BBI->dropAllReferences();
536 WorklistBB.push_back(&*BBI);
537 }
538 while (!WorklistBB.empty()) {
539 BasicBlock *BB = WorklistBB.back();
540 BB->eraseFromParent();
541 WorklistBB.pop_back();
542 }
543}
544
545// We are interested in the following instructions from the entry block as being
546// related to parameter debug info:
547// - @llvm.dbg.declare
548// - stores from the incoming parameters to locations on the stack-frame
549// - allocas that create these locations on the stack-frame
550// - @llvm.dbg.value
551// - the entry block's terminator
552// The rest are unrelated to debug info for the parameters; fill up
553// PDIUnrelatedWL with such instructions.
554void MergeFunctions::filterInstsUnrelatedToPDI(
555 BasicBlock *GEntryBlock, std::vector<Instruction *> &PDIUnrelatedWL) {
556 std::set<Instruction *> PDIRelated;
557 for (BasicBlock::iterator BI = GEntryBlock->begin(), BIE = GEntryBlock->end();
558 BI != BIE; ++BI) {
559 if (auto *DVI = dyn_cast<DbgValueInst>(&*BI)) {
560 LLVM_DEBUG(dbgs() << " Deciding: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deciding: "; } } while (false
)
;
561 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
562 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
563 DILocalVariable *DILocVar = DVI->getVariable();
564 if (DILocVar->isParameter()) {
565 LLVM_DEBUG(dbgs() << " Include (parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include (parameter): "; }
} while (false)
;
566 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
567 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
568 PDIRelated.insert(&*BI);
569 } else {
570 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false)
;
571 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
572 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
573 }
574 } else if (auto *DDI = dyn_cast<DbgDeclareInst>(&*BI)) {
575 LLVM_DEBUG(dbgs() << " Deciding: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deciding: "; } } while (false
)
;
576 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
577 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
578 DILocalVariable *DILocVar = DDI->getVariable();
579 if (DILocVar->isParameter()) {
580 LLVM_DEBUG(dbgs() << " Parameter: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Parameter: "; } } while (
false)
;
581 LLVM_DEBUG(DILocVar->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { DILocVar->print(dbgs()); } } while (false
)
;
582 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
583 if (AI) {
584 LLVM_DEBUG(dbgs() << " Processing alloca users: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Processing alloca users: "
; } } while (false)
;
585 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
586 for (User *U : AI->users()) {
587 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
588 if (Value *Arg = SI->getValueOperand()) {
589 if (dyn_cast<Argument>(Arg)) {
590 LLVM_DEBUG(dbgs() << " Include: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include: "; } } while (false
)
;
591 LLVM_DEBUG(AI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { AI->print(dbgs()); } } while (false)
;
592 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
593 PDIRelated.insert(AI);
594 LLVM_DEBUG(dbgs() << " Include (parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include (parameter): "; }
} while (false)
;
595 LLVM_DEBUG(SI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { SI->print(dbgs()); } } while (false)
;
596 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
597 PDIRelated.insert(SI);
598 LLVM_DEBUG(dbgs() << " Include: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include: "; } } while (false
)
;
599 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
600 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
601 PDIRelated.insert(&*BI);
602 } else {
603 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false)
;
604 LLVM_DEBUG(SI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { SI->print(dbgs()); } } while (false)
;
605 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
606 }
607 }
608 } else {
609 LLVM_DEBUG(dbgs() << " Defer: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Defer: "; } } while (false
)
;
610 LLVM_DEBUG(U->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { U->print(dbgs()); } } while (false)
;
611 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
612 }
613 }
614 } else {
615 LLVM_DEBUG(dbgs() << " Delete (alloca NULL): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (alloca NULL): "; }
} while (false)
;
616 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
617 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
618 }
619 } else {
620 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false)
;
621 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
622 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
623 }
624 } else if (BI->isTerminator() && &*BI == GEntryBlock->getTerminator()) {
625 LLVM_DEBUG(dbgs() << " Will Include Terminator: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Will Include Terminator: "
; } } while (false)
;
626 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
627 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
628 PDIRelated.insert(&*BI);
629 } else {
630 LLVM_DEBUG(dbgs() << " Defer: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Defer: "; } } while (false
)
;
631 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
632 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
633 }
634 }
635 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
636 dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
637 << " Report parameter debug info related/related instructions: {\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
;
638 for (BasicBlock::iterator BI = GEntryBlock->begin(), BE = GEntryBlock->end();
639 BI != BE; ++BI) {
640
641 Instruction *I = &*BI;
642 if (PDIRelated.find(I) == PDIRelated.end()) {
643 LLVM_DEBUG(dbgs() << " !PDIRelated: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " !PDIRelated: "; } } while
(false)
;
644 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false)
;
645 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
646 PDIUnrelatedWL.push_back(I);
647 } else {
648 LLVM_DEBUG(dbgs() << " PDIRelated: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " PDIRelated: "; } } while
(false)
;
649 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false)
;
650 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
651 }
652 }
653 LLVM_DEBUG(dbgs() << " }\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " }\n"; } } while (false)
;
654}
655
656/// Whether this function may be replaced by a forwarding thunk.
657static bool canCreateThunkFor(Function *F) {
658 if (F->isVarArg())
659 return false;
660
661 // Don't merge tiny functions using a thunk, since it can just end up
662 // making the function larger.
663 if (F->size() == 1) {
664 if (F->front().size() <= 2) {
665 LLVM_DEBUG(dbgs() << "canCreateThunkFor: " << F->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "canCreateThunkFor: " <<
F->getName() << " is too small to bother creating a thunk for\n"
; } } while (false)
666 << " is too small to bother creating a thunk for\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "canCreateThunkFor: " <<
F->getName() << " is too small to bother creating a thunk for\n"
; } } while (false)
;
667 return false;
668 }
669 }
670 return true;
671}
672
673// Replace G with a simple tail call to bitcast(F). Also (unless
674// MergeFunctionsPDI holds) replace direct uses of G with bitcast(F),
675// delete G. Under MergeFunctionsPDI, we use G itself for creating
676// the thunk as we preserve the debug info (and associated instructions)
677// from G's entry block pertaining to G's incoming arguments which are
678// passed on as corresponding arguments in the call that G makes to F.
679// For better debugability, under MergeFunctionsPDI, we do not modify G's
680// call sites to point to F even when within the same translation unit.
681void MergeFunctions::writeThunk(Function *F, Function *G) {
682 BasicBlock *GEntryBlock = nullptr;
683 std::vector<Instruction *> PDIUnrelatedWL;
684 BasicBlock *BB = nullptr;
685 Function *NewG = nullptr;
1
'NewG' initialized to a null pointer value
686 if (MergeFunctionsPDI) {
2
Assuming the condition is true
3
Taking true branch
687 LLVM_DEBUG(dbgs() << "writeThunk: (MergeFunctionsPDI) Do not create a new "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) Do not create a new "
"function as thunk; retain original: " << G->getName
() << "()\n"; } } while (false)
4
Assuming 'DebugFlag' is false
5
Loop condition is false. Exiting loop
688 "function as thunk; retain original: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) Do not create a new "
"function as thunk; retain original: " << G->getName
() << "()\n"; } } while (false)
689 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) Do not create a new "
"function as thunk; retain original: " << G->getName
() << "()\n"; } } while (false)
;
690 GEntryBlock = &G->getEntryBlock();
691 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
6
Assuming 'DebugFlag' is false
7
Loop condition is false. Exiting loop
692 dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
693 "debug info for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
694 << G->getName() << "() {\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
;
695 filterInstsUnrelatedToPDI(GEntryBlock, PDIUnrelatedWL);
696 GEntryBlock->getTerminator()->eraseFromParent();
697 BB = GEntryBlock;
698 } else {
699 NewG = Function::Create(G->getFunctionType(), G->getLinkage(),
700 G->getAddressSpace(), "", G->getParent());
701 NewG->setComdat(G->getComdat());
702 BB = BasicBlock::Create(F->getContext(), "", NewG);
703 }
704
705 IRBuilder<> Builder(BB);
706 Function *H = MergeFunctionsPDI ? G : NewG;
8
Assuming the condition is false
9
'?' condition is false
10
'H' initialized to a null pointer value
707 SmallVector<Value *, 16> Args;
708 unsigned i = 0;
709 FunctionType *FFTy = F->getFunctionType();
710 for (Argument &AI : H->args()) {
11
Called C++ object pointer is null
711 Args.push_back(createCast(Builder, &AI, FFTy->getParamType(i)));
712 ++i;
713 }
714
715 CallInst *CI = Builder.CreateCall(F, Args);
716 ReturnInst *RI = nullptr;
717 CI->setTailCall();
718 CI->setCallingConv(F->getCallingConv());
719 CI->setAttributes(F->getAttributes());
720 if (H->getReturnType()->isVoidTy()) {
721 RI = Builder.CreateRetVoid();
722 } else {
723 RI = Builder.CreateRet(createCast(Builder, CI, H->getReturnType()));
724 }
725
726 if (MergeFunctionsPDI) {
727 DISubprogram *DIS = G->getSubprogram();
728 if (DIS) {
729 DebugLoc CIDbgLoc = DebugLoc::get(DIS->getScopeLine(), 0, DIS);
730 DebugLoc RIDbgLoc = DebugLoc::get(DIS->getScopeLine(), 0, DIS);
731 CI->setDebugLoc(CIDbgLoc);
732 RI->setDebugLoc(RIDbgLoc);
733 } else {
734 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
735 dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
736 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
;
737 }
738 eraseTail(G);
739 eraseInstsUnrelatedToPDI(PDIUnrelatedWL);
740 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false)
741 dbgs() << "} // End of parameter related debug info filtering for: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false)
742 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false)
;
743 } else {
744 NewG->copyAttributesFrom(G);
745 NewG->takeName(G);
746 removeUsers(G);
747 G->replaceAllUsesWith(NewG);
748 G->eraseFromParent();
749 }
750
751 LLVM_DEBUG(dbgs() << "writeThunk: " << H->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: " << H->
getName() << '\n'; } } while (false)
;
752 ++NumThunksWritten;
753}
754
755// Whether this function may be replaced by an alias
756static bool canCreateAliasFor(Function *F) {
757 if (!MergeFunctionsAliases || !F->hasGlobalUnnamedAddr())
758 return false;
759
760 // We should only see linkages supported by aliases here
761 assert(F->hasLocalLinkage() || F->hasExternalLinkage()((F->hasLocalLinkage() || F->hasExternalLinkage() || F->
hasWeakLinkage() || F->hasLinkOnceLinkage()) ? static_cast
<void> (0) : __assert_fail ("F->hasLocalLinkage() || F->hasExternalLinkage() || F->hasWeakLinkage() || F->hasLinkOnceLinkage()"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 762, __PRETTY_FUNCTION__))
762 || F->hasWeakLinkage() || F->hasLinkOnceLinkage())((F->hasLocalLinkage() || F->hasExternalLinkage() || F->
hasWeakLinkage() || F->hasLinkOnceLinkage()) ? static_cast
<void> (0) : __assert_fail ("F->hasLocalLinkage() || F->hasExternalLinkage() || F->hasWeakLinkage() || F->hasLinkOnceLinkage()"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 762, __PRETTY_FUNCTION__))
;
763 return true;
764}
765
766// Replace G with an alias to F (deleting function G)
767void MergeFunctions::writeAlias(Function *F, Function *G) {
768 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
769 PointerType *PtrType = G->getType();
770 auto *GA = GlobalAlias::create(
771 PtrType->getElementType(), PtrType->getAddressSpace(),
772 G->getLinkage(), "", BitcastF, G->getParent());
773
774 F->setAlignment(MaybeAlign(std::max(F->getAlignment(), G->getAlignment())));
775 GA->takeName(G);
776 GA->setVisibility(G->getVisibility());
777 GA->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
778
779 removeUsers(G);
780 G->replaceAllUsesWith(GA);
781 G->eraseFromParent();
782
783 LLVM_DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeAlias: " << GA->
getName() << '\n'; } } while (false)
;
784 ++NumAliasesWritten;
785}
786
787// Replace G with an alias to F if possible, or a thunk to F if
788// profitable. Returns false if neither is the case.
789bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
790 if (canCreateAliasFor(G)) {
791 writeAlias(F, G);
792 return true;
793 }
794 if (canCreateThunkFor(F)) {
795 writeThunk(F, G);
796 return true;
797 }
798 return false;
799}
800
801// Merge two equivalent functions. Upon completion, Function G is deleted.
802void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
803 if (F->isInterposable()) {
804 assert(G->isInterposable())((G->isInterposable()) ? static_cast<void> (0) : __assert_fail
("G->isInterposable()", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 804, __PRETTY_FUNCTION__))
;
805
806 // Both writeThunkOrAlias() calls below must succeed, either because we can
807 // create aliases for G and NewF, or because a thunk for F is profitable.
808 // F here has the same signature as NewF below, so that's what we check.
809 if (!canCreateThunkFor(F) &&
810 (!canCreateAliasFor(F) || !canCreateAliasFor(G)))
811 return;
812
813 // Make them both thunks to the same internal function.
814 Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
815 F->getAddressSpace(), "", F->getParent());
816 NewF->copyAttributesFrom(F);
817 NewF->takeName(F);
818 removeUsers(F);
819 F->replaceAllUsesWith(NewF);
820
821 MaybeAlign MaxAlignment(std::max(G->getAlignment(), NewF->getAlignment()));
822
823 writeThunkOrAlias(F, G);
824 writeThunkOrAlias(F, NewF);
825
826 F->setAlignment(MaxAlignment);
827 F->setLinkage(GlobalValue::PrivateLinkage);
828 ++NumDoubleWeak;
829 ++NumFunctionsMerged;
830 } else {
831 // For better debugability, under MergeFunctionsPDI, we do not modify G's
832 // call sites to point to F even when within the same translation unit.
833 if (!G->isInterposable() && !MergeFunctionsPDI) {
834 if (G->hasGlobalUnnamedAddr()) {
835 // G might have been a key in our GlobalNumberState, and it's illegal
836 // to replace a key in ValueMap<GlobalValue *> with a non-global.
837 GlobalNumbers.erase(G);
838 // If G's address is not significant, replace it entirely.
839 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
840 removeUsers(G);
841 G->replaceAllUsesWith(BitcastF);
842 } else {
843 // Redirect direct callers of G to F. (See note on MergeFunctionsPDI
844 // above).
845 replaceDirectCallers(G, F);
846 }
847 }
848
849 // If G was internal then we may have replaced all uses of G with F. If so,
850 // stop here and delete G. There's no need for a thunk. (See note on
851 // MergeFunctionsPDI above).
852 if (G->isDiscardableIfUnused() && G->use_empty() && !MergeFunctionsPDI) {
853 G->eraseFromParent();
854 ++NumFunctionsMerged;
855 return;
856 }
857
858 if (writeThunkOrAlias(F, G)) {
859 ++NumFunctionsMerged;
860 }
861 }
862}
863
864/// Replace function F by function G.
865void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
866 Function *G) {
867 Function *F = FN.getFunc();
868 assert(FunctionComparator(F, G, &GlobalNumbers).compare() == 0 &&((FunctionComparator(F, G, &GlobalNumbers).compare() == 0
&& "The two functions must be equal") ? static_cast<
void> (0) : __assert_fail ("FunctionComparator(F, G, &GlobalNumbers).compare() == 0 && \"The two functions must be equal\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 869, __PRETTY_FUNCTION__))
869 "The two functions must be equal")((FunctionComparator(F, G, &GlobalNumbers).compare() == 0
&& "The two functions must be equal") ? static_cast<
void> (0) : __assert_fail ("FunctionComparator(F, G, &GlobalNumbers).compare() == 0 && \"The two functions must be equal\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 869, __PRETTY_FUNCTION__))
;
870
871 auto I = FNodesInTree.find(F);
872 assert(I != FNodesInTree.end() && "F should be in FNodesInTree")((I != FNodesInTree.end() && "F should be in FNodesInTree"
) ? static_cast<void> (0) : __assert_fail ("I != FNodesInTree.end() && \"F should be in FNodesInTree\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 872, __PRETTY_FUNCTION__))
;
873 assert(FNodesInTree.count(G) == 0 && "FNodesInTree should not contain G")((FNodesInTree.count(G) == 0 && "FNodesInTree should not contain G"
) ? static_cast<void> (0) : __assert_fail ("FNodesInTree.count(G) == 0 && \"FNodesInTree should not contain G\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 873, __PRETTY_FUNCTION__))
;
874
875 FnTreeType::iterator IterToFNInFnTree = I->second;
876 assert(&(*IterToFNInFnTree) == &FN && "F should map to FN in FNodesInTree.")((&(*IterToFNInFnTree) == &FN && "F should map to FN in FNodesInTree."
) ? static_cast<void> (0) : __assert_fail ("&(*IterToFNInFnTree) == &FN && \"F should map to FN in FNodesInTree.\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 876, __PRETTY_FUNCTION__))
;
877 // Remove F -> FN and insert G -> FN
878 FNodesInTree.erase(I);
879 FNodesInTree.insert({G, IterToFNInFnTree});
880 // Replace F with G in FN, which is stored inside the FnTree.
881 FN.replaceBy(G);
882}
883
884// Ordering for functions that are equal under FunctionComparator
885static bool isFuncOrderCorrect(const Function *F, const Function *G) {
886 if (F->isInterposable() != G->isInterposable()) {
887 // Strong before weak, because the weak function may call the strong
888 // one, but not the other way around.
889 return !F->isInterposable();
890 }
891 if (F->hasLocalLinkage() != G->hasLocalLinkage()) {
892 // External before local, because we definitely have to keep the external
893 // function, but may be able to drop the local one.
894 return !F->hasLocalLinkage();
895 }
896 // Impose a total order (by name) on the replacement of functions. This is
897 // important when operating on more than one module independently to prevent
898 // cycles of thunks calling each other when the modules are linked together.
899 return F->getName() <= G->getName();
900}
901
902// Insert a ComparableFunction into the FnTree, or merge it away if equal to one
903// that was already inserted.
904bool MergeFunctions::insert(Function *NewFunction) {
905 std::pair<FnTreeType::iterator, bool> Result =
906 FnTree.insert(FunctionNode(NewFunction));
907
908 if (Result.second) {
909 assert(FNodesInTree.count(NewFunction) == 0)((FNodesInTree.count(NewFunction) == 0) ? static_cast<void
> (0) : __assert_fail ("FNodesInTree.count(NewFunction) == 0"
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 909, __PRETTY_FUNCTION__))
;
910 FNodesInTree.insert({NewFunction, Result.first});
911 LLVM_DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Inserting as unique: " <<
NewFunction->getName() << '\n'; } } while (false)
912 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Inserting as unique: " <<
NewFunction->getName() << '\n'; } } while (false)
;
913 return false;
914 }
915
916 const FunctionNode &OldF = *Result.first;
917
918 if (!isFuncOrderCorrect(OldF.getFunc(), NewFunction)) {
919 // Swap the two functions.
920 Function *F = OldF.getFunc();
921 replaceFunctionInTree(*Result.first, NewFunction);
922 NewFunction = F;
923 assert(OldF.getFunc() != F && "Must have swapped the functions.")((OldF.getFunc() != F && "Must have swapped the functions."
) ? static_cast<void> (0) : __assert_fail ("OldF.getFunc() != F && \"Must have swapped the functions.\""
, "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 923, __PRETTY_FUNCTION__))
;
924 }
925
926 LLVM_DEBUG(dbgs() << " " << OldF.getFunc()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " " << OldF.getFunc()
->getName() << " == " << NewFunction->getName
() << '\n'; } } while (false)
927 << " == " << NewFunction->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " " << OldF.getFunc()
->getName() << " == " << NewFunction->getName
() << '\n'; } } while (false)
;
928
929 Function *DeleteF = NewFunction;
930 mergeTwoFunctions(OldF.getFunc(), DeleteF);
931 return true;
932}
933
934// Remove a function from FnTree. If it was already in FnTree, add
935// it to Deferred so that we'll look at it in the next round.
936void MergeFunctions::remove(Function *F) {
937 auto I = FNodesInTree.find(F);
938 if (I != FNodesInTree.end()) {
939 LLVM_DEBUG(dbgs() << "Deferred " << F->getName() << ".\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Deferred " << F->getName
() << ".\n"; } } while (false)
;
940 FnTree.erase(I->second);
941 // I->second has been invalidated, remove it from the FNodesInTree map to
942 // preserve the invariant.
943 FNodesInTree.erase(I);
944 Deferred.emplace_back(F);
945 }
946}
947
948// For each instruction used by the value, remove() the function that contains
949// the instruction. This should happen right before a call to RAUW.
950void MergeFunctions::removeUsers(Value *V) {
951 for (User *U : V->users())
952 if (auto *I = dyn_cast<Instruction>(U))
953 remove(I->getFunction());
954}