Bug Summary

File:build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/Transforms/IPO/MergeFunctions.cpp
Warning:line 700, column 23
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -clear-ast-before-backend -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 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/build-llvm -resource-dir /usr/lib/llvm-15/lib/clang/15.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I lib/Transforms/IPO -I /build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/Transforms/IPO -I include -I /build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/include -D _FORTIFY_SOURCE=2 -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-15/lib/clang/15.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fmacro-prefix-map=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/build-llvm=build-llvm -fmacro-prefix-map=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/= -fcoverage-prefix-map=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/build-llvm=build-llvm -fcoverage-prefix-map=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/= -O3 -Wno-unused-command-line-argument -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/build-llvm -fdebug-prefix-map=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/build-llvm=build-llvm -fdebug-prefix-map=/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/= -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2022-04-20-140412-16051-1 -x c++ /build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/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/Transforms/IPO/MergeFunctions.h"
92#include "llvm/ADT/ArrayRef.h"
93#include "llvm/ADT/SmallVector.h"
94#include "llvm/ADT/Statistic.h"
95#include "llvm/IR/Argument.h"
96#include "llvm/IR/BasicBlock.h"
97#include "llvm/IR/Constant.h"
98#include "llvm/IR/Constants.h"
99#include "llvm/IR/DebugInfoMetadata.h"
100#include "llvm/IR/DebugLoc.h"
101#include "llvm/IR/DerivedTypes.h"
102#include "llvm/IR/Function.h"
103#include "llvm/IR/GlobalValue.h"
104#include "llvm/IR/IRBuilder.h"
105#include "llvm/IR/InstrTypes.h"
106#include "llvm/IR/Instruction.h"
107#include "llvm/IR/Instructions.h"
108#include "llvm/IR/IntrinsicInst.h"
109#include "llvm/IR/Module.h"
110#include "llvm/IR/Type.h"
111#include "llvm/IR/Use.h"
112#include "llvm/IR/User.h"
113#include "llvm/IR/Value.h"
114#include "llvm/IR/ValueHandle.h"
115#include "llvm/InitializePasses.h"
116#include "llvm/Pass.h"
117#include "llvm/Support/Casting.h"
118#include "llvm/Support/CommandLine.h"
119#include "llvm/Support/Debug.h"
120#include "llvm/Support/raw_ostream.h"
121#include "llvm/Transforms/IPO.h"
122#include "llvm/Transforms/Utils/FunctionComparator.h"
123#include <algorithm>
124#include <cassert>
125#include <iterator>
126#include <set>
127#include <utility>
128#include <vector>
129
130using namespace llvm;
131
132#define DEBUG_TYPE"mergefunc" "mergefunc"
133
134STATISTIC(NumFunctionsMerged, "Number of functions merged")static llvm::Statistic NumFunctionsMerged = {"mergefunc", "NumFunctionsMerged"
, "Number of functions merged"};
135STATISTIC(NumThunksWritten, "Number of thunks generated")static llvm::Statistic NumThunksWritten = {"mergefunc", "NumThunksWritten"
, "Number of thunks generated"};
136STATISTIC(NumAliasesWritten, "Number of aliases generated")static llvm::Statistic NumAliasesWritten = {"mergefunc", "NumAliasesWritten"
, "Number of aliases generated"};
137STATISTIC(NumDoubleWeak, "Number of new functions created")static llvm::Statistic NumDoubleWeak = {"mergefunc", "NumDoubleWeak"
, "Number of new functions created"};
138
139static cl::opt<unsigned> NumFunctionsForVerificationCheck(
140 "mergefunc-verify",
141 cl::desc("How many functions in a module could be used for "
142 "MergeFunctions to pass a basic correctness check. "
143 "'0' disables this check. Works only with '-debug' key."),
144 cl::init(0), cl::Hidden);
145
146// Under option -mergefunc-preserve-debug-info we:
147// - Do not create a new function for a thunk.
148// - Retain the debug info for a thunk's parameters (and associated
149// instructions for the debug info) from the entry block.
150// Note: -debug will display the algorithm at work.
151// - Create debug-info for the call (to the shared implementation) made by
152// a thunk and its return value.
153// - Erase the rest of the function, retaining the (minimally sized) entry
154// block to create a thunk.
155// - Preserve a thunk's call site to point to the thunk even when both occur
156// within the same translation unit, to aid debugability. Note that this
157// behaviour differs from the underlying -mergefunc implementation which
158// modifies the thunk's call site to point to the shared implementation
159// when both occur within the same translation unit.
160static cl::opt<bool>
161 MergeFunctionsPDI("mergefunc-preserve-debug-info", cl::Hidden,
162 cl::init(false),
163 cl::desc("Preserve debug info in thunk when mergefunc "
164 "transformations are made."));
165
166static cl::opt<bool>
167 MergeFunctionsAliases("mergefunc-use-aliases", cl::Hidden,
168 cl::init(false),
169 cl::desc("Allow mergefunc to create aliases"));
170
171namespace {
172
173class FunctionNode {
174 mutable AssertingVH<Function> F;
175 FunctionComparator::FunctionHash Hash;
176
177public:
178 // Note the hash is recalculated potentially multiple times, but it is cheap.
179 FunctionNode(Function *F)
180 : F(F), Hash(FunctionComparator::functionHash(*F)) {}
181
182 Function *getFunc() const { return F; }
183 FunctionComparator::FunctionHash getHash() const { return Hash; }
184
185 /// Replace the reference to the function F by the function G, assuming their
186 /// implementations are equal.
187 void replaceBy(Function *G) const {
188 F = G;
189 }
190};
191
192/// MergeFunctions finds functions which will generate identical machine code,
193/// by considering all pointer types to be equivalent. Once identified,
194/// MergeFunctions will fold them by replacing a call to one to a call to a
195/// bitcast of the other.
196class MergeFunctions {
197public:
198 MergeFunctions() : FnTree(FunctionNodeCmp(&GlobalNumbers)) {
199 }
200
201 bool runOnModule(Module &M);
202
203private:
204 // The function comparison operator is provided here so that FunctionNodes do
205 // not need to become larger with another pointer.
206 class FunctionNodeCmp {
207 GlobalNumberState* GlobalNumbers;
208
209 public:
210 FunctionNodeCmp(GlobalNumberState* GN) : GlobalNumbers(GN) {}
211
212 bool operator()(const FunctionNode &LHS, const FunctionNode &RHS) const {
213 // Order first by hashes, then full function comparison.
214 if (LHS.getHash() != RHS.getHash())
215 return LHS.getHash() < RHS.getHash();
216 FunctionComparator FCmp(LHS.getFunc(), RHS.getFunc(), GlobalNumbers);
217 return FCmp.compare() == -1;
218 }
219 };
220 using FnTreeType = std::set<FunctionNode, FunctionNodeCmp>;
221
222 GlobalNumberState GlobalNumbers;
223
224 /// A work queue of functions that may have been modified and should be
225 /// analyzed again.
226 std::vector<WeakTrackingVH> Deferred;
227
228#ifndef NDEBUG
229 /// Checks the rules of order relation introduced among functions set.
230 /// Returns true, if check has been passed, and false if failed.
231 bool doFunctionalCheck(std::vector<WeakTrackingVH> &Worklist);
232#endif
233
234 /// Insert a ComparableFunction into the FnTree, or merge it away if it's
235 /// equal to one that's already present.
236 bool insert(Function *NewFunction);
237
238 /// Remove a Function from the FnTree and queue it up for a second sweep of
239 /// analysis.
240 void remove(Function *F);
241
242 /// Find the functions that use this Value and remove them from FnTree and
243 /// queue the functions.
244 void removeUsers(Value *V);
245
246 /// Replace all direct calls of Old with calls of New. Will bitcast New if
247 /// necessary to make types match.
248 void replaceDirectCallers(Function *Old, Function *New);
249
250 /// Merge two equivalent functions. Upon completion, G may be deleted, or may
251 /// be converted into a thunk. In either case, it should never be visited
252 /// again.
253 void mergeTwoFunctions(Function *F, Function *G);
254
255 /// Fill PDIUnrelatedWL with instructions from the entry block that are
256 /// unrelated to parameter related debug info.
257 void filterInstsUnrelatedToPDI(BasicBlock *GEntryBlock,
258 std::vector<Instruction *> &PDIUnrelatedWL);
259
260 /// Erase the rest of the CFG (i.e. barring the entry block).
261 void eraseTail(Function *G);
262
263 /// Erase the instructions in PDIUnrelatedWL as they are unrelated to the
264 /// parameter debug info, from the entry block.
265 void eraseInstsUnrelatedToPDI(std::vector<Instruction *> &PDIUnrelatedWL);
266
267 /// Replace G with a simple tail call to bitcast(F). Also (unless
268 /// MergeFunctionsPDI holds) replace direct uses of G with bitcast(F),
269 /// delete G.
270 void writeThunk(Function *F, Function *G);
271
272 // Replace G with an alias to F (deleting function G)
273 void writeAlias(Function *F, Function *G);
274
275 // Replace G with an alias to F if possible, or a thunk to F if possible.
276 // Returns false if neither is the case.
277 bool writeThunkOrAlias(Function *F, Function *G);
278
279 /// Replace function F with function G in the function tree.
280 void replaceFunctionInTree(const FunctionNode &FN, Function *G);
281
282 /// The set of all distinct functions. Use the insert() and remove() methods
283 /// to modify it. The map allows efficient lookup and deferring of Functions.
284 FnTreeType FnTree;
285
286 // Map functions to the iterators of the FunctionNode which contains them
287 // in the FnTree. This must be updated carefully whenever the FnTree is
288 // modified, i.e. in insert(), remove(), and replaceFunctionInTree(), to avoid
289 // dangling iterators into FnTree. The invariant that preserves this is that
290 // there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
291 DenseMap<AssertingVH<Function>, FnTreeType::iterator> FNodesInTree;
292};
293
294class MergeFunctionsLegacyPass : public ModulePass {
295public:
296 static char ID;
297
298 MergeFunctionsLegacyPass(): ModulePass(ID) {
299 initializeMergeFunctionsLegacyPassPass(*PassRegistry::getPassRegistry());
300 }
301
302 bool runOnModule(Module &M) override {
303 if (skipModule(M))
304 return false;
305
306 MergeFunctions MF;
307 return MF.runOnModule(M);
308 }
309};
310
311} // end anonymous namespace
312
313char MergeFunctionsLegacyPass::ID = 0;
314INITIALIZE_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
)); }
315 "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
)); }
316
317ModulePass *llvm::createMergeFunctionsPass() {
318 return new MergeFunctionsLegacyPass();
319}
320
321PreservedAnalyses MergeFunctionsPass::run(Module &M,
322 ModuleAnalysisManager &AM) {
323 MergeFunctions MF;
324 if (!MF.runOnModule(M))
325 return PreservedAnalyses::all();
326 return PreservedAnalyses::none();
327}
328
329#ifndef NDEBUG
330bool MergeFunctions::doFunctionalCheck(std::vector<WeakTrackingVH> &Worklist) {
331 if (const unsigned Max = NumFunctionsForVerificationCheck) {
332 unsigned TripleNumber = 0;
333 bool Valid = true;
334
335 dbgs() << "MERGEFUNC-VERIFY: Started for first " << Max << " functions.\n";
336
337 unsigned i = 0;
338 for (std::vector<WeakTrackingVH>::iterator I = Worklist.begin(),
339 E = Worklist.end();
340 I != E && i < Max; ++I, ++i) {
341 unsigned j = i;
342 for (std::vector<WeakTrackingVH>::iterator J = I; J != E && j < Max;
343 ++J, ++j) {
344 Function *F1 = cast<Function>(*I);
345 Function *F2 = cast<Function>(*J);
346 int Res1 = FunctionComparator(F1, F2, &GlobalNumbers).compare();
347 int Res2 = FunctionComparator(F2, F1, &GlobalNumbers).compare();
348
349 // If F1 <= F2, then F2 >= F1, otherwise report failure.
350 if (Res1 != -Res2) {
351 dbgs() << "MERGEFUNC-VERIFY: Non-symmetric; triple: " << TripleNumber
352 << "\n";
353 dbgs() << *F1 << '\n' << *F2 << '\n';
354 Valid = false;
355 }
356
357 if (Res1 == 0)
358 continue;
359
360 unsigned k = j;
361 for (std::vector<WeakTrackingVH>::iterator K = J; K != E && k < Max;
362 ++k, ++K, ++TripleNumber) {
363 if (K == J)
364 continue;
365
366 Function *F3 = cast<Function>(*K);
367 int Res3 = FunctionComparator(F1, F3, &GlobalNumbers).compare();
368 int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).compare();
369
370 bool Transitive = true;
371
372 if (Res1 != 0 && Res1 == Res4) {
373 // F1 > F2, F2 > F3 => F1 > F3
374 Transitive = Res3 == Res1;
375 } else if (Res3 != 0 && Res3 == -Res4) {
376 // F1 > F3, F3 > F2 => F1 > F2
377 Transitive = Res3 == Res1;
378 } else if (Res4 != 0 && -Res3 == Res4) {
379 // F2 > F3, F3 > F1 => F2 > F1
380 Transitive = Res4 == -Res1;
381 }
382
383 if (!Transitive) {
384 dbgs() << "MERGEFUNC-VERIFY: Non-transitive; triple: "
385 << TripleNumber << "\n";
386 dbgs() << "Res1, Res3, Res4: " << Res1 << ", " << Res3 << ", "
387 << Res4 << "\n";
388 dbgs() << *F1 << '\n' << *F2 << '\n' << *F3 << '\n';
389 Valid = false;
390 }
391 }
392 }
393 }
394
395 dbgs() << "MERGEFUNC-VERIFY: " << (Valid ? "Passed." : "Failed.") << "\n";
396 return Valid;
397 }
398 return true;
399}
400#endif
401
402/// Check whether \p F is eligible for function merging.
403static bool isEligibleForMerging(Function &F) {
404 return !F.isDeclaration() && !F.hasAvailableExternallyLinkage();
405}
406
407bool MergeFunctions::runOnModule(Module &M) {
408 bool Changed = false;
409
410 // All functions in the module, ordered by hash. Functions with a unique
411 // hash value are easily eliminated.
412 std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
413 HashedFuncs;
414 for (Function &Func : M) {
415 if (isEligibleForMerging(Func)) {
416 HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
417 }
418 }
419
420 llvm::stable_sort(HashedFuncs, less_first());
421
422 auto S = HashedFuncs.begin();
423 for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
424 // If the hash value matches the previous value or the next one, we must
425 // consider merging it. Otherwise it is dropped and never considered again.
426 if ((I != S && std::prev(I)->first == I->first) ||
427 (std::next(I) != IE && std::next(I)->first == I->first) ) {
428 Deferred.push_back(WeakTrackingVH(I->second));
429 }
430 }
431
432 do {
433 std::vector<WeakTrackingVH> Worklist;
434 Deferred.swap(Worklist);
435
436 LLVM_DEBUG(doFunctionalCheck(Worklist))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { doFunctionalCheck(Worklist); } } while (false
);
437
438 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);
439 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);
440
441 // Insert functions and merge them.
442 for (WeakTrackingVH &I : Worklist) {
443 if (!I)
444 continue;
445 Function *F = cast<Function>(I);
446 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage()) {
447 Changed |= insert(F);
448 }
449 }
450 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);
451 } while (!Deferred.empty());
452
453 FnTree.clear();
454 FNodesInTree.clear();
455 GlobalNumbers.clear();
456
457 return Changed;
458}
459
460// Replace direct callers of Old with New.
461void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
462 Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
463 for (Use &U : llvm::make_early_inc_range(Old->uses())) {
464 CallBase *CB = dyn_cast<CallBase>(U.getUser());
465 if (CB && CB->isCallee(&U)) {
466 // Do not copy attributes from the called function to the call-site.
467 // Function comparison ensures that the attributes are the same up to
468 // type congruences in byval(), in which case we need to keep the byval
469 // type of the call-site, not the callee function.
470 remove(CB->getFunction());
471 U.set(BitcastNew);
472 }
473 }
474}
475
476// Helper for writeThunk,
477// Selects proper bitcast operation,
478// but a bit simpler then CastInst::getCastOpcode.
479static Value *createCast(IRBuilder<> &Builder, Value *V, Type *DestTy) {
480 Type *SrcTy = V->getType();
481 if (SrcTy->isStructTy()) {
482 assert(DestTy->isStructTy())(static_cast <bool> (DestTy->isStructTy()) ? void (0
) : __assert_fail ("DestTy->isStructTy()", "llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 482, __extension__ __PRETTY_FUNCTION__));
483 assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements())(static_cast <bool> (SrcTy->getStructNumElements() ==
DestTy->getStructNumElements()) ? void (0) : __assert_fail
("SrcTy->getStructNumElements() == DestTy->getStructNumElements()"
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 483, __extension__
__PRETTY_FUNCTION__));
484 Value *Result = UndefValue::get(DestTy);
485 for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) {
486 Value *Element = createCast(
487 Builder, Builder.CreateExtractValue(V, makeArrayRef(I)),
488 DestTy->getStructElementType(I));
489
490 Result =
491 Builder.CreateInsertValue(Result, Element, makeArrayRef(I));
492 }
493 return Result;
494 }
495 assert(!DestTy->isStructTy())(static_cast <bool> (!DestTy->isStructTy()) ? void (
0) : __assert_fail ("!DestTy->isStructTy()", "llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 495, __extension__ __PRETTY_FUNCTION__));
496 if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
497 return Builder.CreateIntToPtr(V, DestTy);
498 else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
499 return Builder.CreatePtrToInt(V, DestTy);
500 else
501 return Builder.CreateBitCast(V, DestTy);
502}
503
504// Erase the instructions in PDIUnrelatedWL as they are unrelated to the
505// parameter debug info, from the entry block.
506void MergeFunctions::eraseInstsUnrelatedToPDI(
507 std::vector<Instruction *> &PDIUnrelatedWL) {
508 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)
509 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)
510 "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)
511 "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);
512 while (!PDIUnrelatedWL.empty()) {
513 Instruction *I = PDIUnrelatedWL.back();
514 LLVM_DEBUG(dbgs() << " Deleting Instruction: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deleting Instruction: "; }
} while (false);
515 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false);
516 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
517 I->eraseFromParent();
518 PDIUnrelatedWL.pop_back();
519 }
520 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)
521 "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);
522}
523
524// Reduce G to its entry block.
525void MergeFunctions::eraseTail(Function *G) {
526 std::vector<BasicBlock *> WorklistBB;
527 for (BasicBlock &BB : drop_begin(*G)) {
528 BB.dropAllReferences();
529 WorklistBB.push_back(&BB);
530 }
531 while (!WorklistBB.empty()) {
532 BasicBlock *BB = WorklistBB.back();
533 BB->eraseFromParent();
534 WorklistBB.pop_back();
535 }
536}
537
538// We are interested in the following instructions from the entry block as being
539// related to parameter debug info:
540// - @llvm.dbg.declare
541// - stores from the incoming parameters to locations on the stack-frame
542// - allocas that create these locations on the stack-frame
543// - @llvm.dbg.value
544// - the entry block's terminator
545// The rest are unrelated to debug info for the parameters; fill up
546// PDIUnrelatedWL with such instructions.
547void MergeFunctions::filterInstsUnrelatedToPDI(
548 BasicBlock *GEntryBlock, std::vector<Instruction *> &PDIUnrelatedWL) {
549 std::set<Instruction *> PDIRelated;
550 for (BasicBlock::iterator BI = GEntryBlock->begin(), BIE = GEntryBlock->end();
551 BI != BIE; ++BI) {
552 if (auto *DVI = dyn_cast<DbgValueInst>(&*BI)) {
553 LLVM_DEBUG(dbgs() << " Deciding: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deciding: "; } } while (false
);
554 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
555 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
556 DILocalVariable *DILocVar = DVI->getVariable();
557 if (DILocVar->isParameter()) {
558 LLVM_DEBUG(dbgs() << " Include (parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include (parameter): "; }
} while (false);
559 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
560 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
561 PDIRelated.insert(&*BI);
562 } else {
563 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false);
564 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
565 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
566 }
567 } else if (auto *DDI = dyn_cast<DbgDeclareInst>(&*BI)) {
568 LLVM_DEBUG(dbgs() << " Deciding: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deciding: "; } } while (false
);
569 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
570 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
571 DILocalVariable *DILocVar = DDI->getVariable();
572 if (DILocVar->isParameter()) {
573 LLVM_DEBUG(dbgs() << " Parameter: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Parameter: "; } } while (
false);
574 LLVM_DEBUG(DILocVar->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { DILocVar->print(dbgs()); } } while (false
);
575 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
576 if (AI) {
577 LLVM_DEBUG(dbgs() << " Processing alloca users: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Processing alloca users: "
; } } while (false);
578 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
579 for (User *U : AI->users()) {
580 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
581 if (Value *Arg = SI->getValueOperand()) {
582 if (isa<Argument>(Arg)) {
583 LLVM_DEBUG(dbgs() << " Include: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include: "; } } while (false
);
584 LLVM_DEBUG(AI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { AI->print(dbgs()); } } while (false);
585 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
586 PDIRelated.insert(AI);
587 LLVM_DEBUG(dbgs() << " Include (parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include (parameter): "; }
} while (false);
588 LLVM_DEBUG(SI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { SI->print(dbgs()); } } while (false);
589 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
590 PDIRelated.insert(SI);
591 LLVM_DEBUG(dbgs() << " Include: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include: "; } } while (false
);
592 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
593 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
594 PDIRelated.insert(&*BI);
595 } else {
596 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false);
597 LLVM_DEBUG(SI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { SI->print(dbgs()); } } while (false);
598 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
599 }
600 }
601 } else {
602 LLVM_DEBUG(dbgs() << " Defer: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Defer: "; } } while (false
);
603 LLVM_DEBUG(U->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { U->print(dbgs()); } } while (false);
604 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
605 }
606 }
607 } else {
608 LLVM_DEBUG(dbgs() << " Delete (alloca NULL): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (alloca NULL): "; }
} while (false);
609 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
610 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
611 }
612 } else {
613 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false);
614 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
615 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
616 }
617 } else if (BI->isTerminator() && &*BI == GEntryBlock->getTerminator()) {
618 LLVM_DEBUG(dbgs() << " Will Include Terminator: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Will Include Terminator: "
; } } while (false);
619 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
620 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
621 PDIRelated.insert(&*BI);
622 } else {
623 LLVM_DEBUG(dbgs() << " Defer: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Defer: "; } } while (false
);
624 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false);
625 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
626 }
627 }
628 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
629 dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
630 << " 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);
631 for (Instruction &I : *GEntryBlock) {
632 if (PDIRelated.find(&I) == PDIRelated.end()) {
633 LLVM_DEBUG(dbgs() << " !PDIRelated: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " !PDIRelated: "; } } while
(false);
634 LLVM_DEBUG(I.print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I.print(dbgs()); } } while (false);
635 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
636 PDIUnrelatedWL.push_back(&I);
637 } else {
638 LLVM_DEBUG(dbgs() << " PDIRelated: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " PDIRelated: "; } } while
(false);
639 LLVM_DEBUG(I.print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I.print(dbgs()); } } while (false);
640 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false);
641 }
642 }
643 LLVM_DEBUG(dbgs() << " }\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " }\n"; } } while (false);
644}
645
646/// Whether this function may be replaced by a forwarding thunk.
647static bool canCreateThunkFor(Function *F) {
648 if (F->isVarArg())
649 return false;
650
651 // Don't merge tiny functions using a thunk, since it can just end up
652 // making the function larger.
653 if (F->size() == 1) {
654 if (F->front().size() <= 2) {
655 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)
656 << " 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);
657 return false;
658 }
659 }
660 return true;
661}
662
663// Replace G with a simple tail call to bitcast(F). Also (unless
664// MergeFunctionsPDI holds) replace direct uses of G with bitcast(F),
665// delete G. Under MergeFunctionsPDI, we use G itself for creating
666// the thunk as we preserve the debug info (and associated instructions)
667// from G's entry block pertaining to G's incoming arguments which are
668// passed on as corresponding arguments in the call that G makes to F.
669// For better debugability, under MergeFunctionsPDI, we do not modify G's
670// call sites to point to F even when within the same translation unit.
671void MergeFunctions::writeThunk(Function *F, Function *G) {
672 BasicBlock *GEntryBlock = nullptr;
673 std::vector<Instruction *> PDIUnrelatedWL;
674 BasicBlock *BB = nullptr;
675 Function *NewG = nullptr;
1
'NewG' initialized to a null pointer value
→
676 if (MergeFunctionsPDI) {
2
←
Assuming the condition is true
→
677 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)
3
←
Taking true branch
→
4
←
Assuming 'DebugFlag' is false
→
5
←
Loop condition is false. Exiting loop
→
678 "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)
679 << 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);
680 GEntryBlock = &G->getEntryBlock();
681 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
→
682 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)
683 "debug info for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
684 << G->getName() << "() {\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false);
685 filterInstsUnrelatedToPDI(GEntryBlock, PDIUnrelatedWL);
686 GEntryBlock->getTerminator()->eraseFromParent();
687 BB = GEntryBlock;
688 } else {
689 NewG = Function::Create(G->getFunctionType(), G->getLinkage(),
690 G->getAddressSpace(), "", G->getParent());
691 NewG->setComdat(G->getComdat());
692 BB = BasicBlock::Create(F->getContext(), "", NewG);
693 }
694
695 IRBuilder<> Builder(BB);
696 Function *H = MergeFunctionsPDI ? G : NewG;
8
←
Assuming the condition is false
→
9
←
'?' condition is false
→
10
←
'H' initialized to a null pointer value
→
697 SmallVector<Value *, 16> Args;
698 unsigned i = 0;
699 FunctionType *FFTy = F->getFunctionType();
700 for (Argument &AI : H->args()) {
11
←
Called C++ object pointer is null
701 Args.push_back(createCast(Builder, &AI, FFTy->getParamType(i)));
702 ++i;
703 }
704
705 CallInst *CI = Builder.CreateCall(F, Args);
706 ReturnInst *RI = nullptr;
707 bool isSwiftTailCall = F->getCallingConv() == CallingConv::SwiftTail &&
708 G->getCallingConv() == CallingConv::SwiftTail;
709 CI->setTailCallKind(isSwiftTailCall ? llvm::CallInst::TCK_MustTail
710 : llvm::CallInst::TCK_Tail);
711 CI->setCallingConv(F->getCallingConv());
712 CI->setAttributes(F->getAttributes());
713 if (H->getReturnType()->isVoidTy()) {
714 RI = Builder.CreateRetVoid();
715 } else {
716 RI = Builder.CreateRet(createCast(Builder, CI, H->getReturnType()));
717 }
718
719 if (MergeFunctionsPDI) {
720 DISubprogram *DIS = G->getSubprogram();
721 if (DIS) {
722 DebugLoc CIDbgLoc =
723 DILocation::get(DIS->getContext(), DIS->getScopeLine(), 0, DIS);
724 DebugLoc RIDbgLoc =
725 DILocation::get(DIS->getContext(), DIS->getScopeLine(), 0, DIS);
726 CI->setDebugLoc(CIDbgLoc);
727 RI->setDebugLoc(RIDbgLoc);
728 } else {
729 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
730 dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
731 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false);
732 }
733 eraseTail(G);
734 eraseInstsUnrelatedToPDI(PDIUnrelatedWL);
735 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false)
736 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)
737 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false);
738 } else {
739 NewG->copyAttributesFrom(G);
740 NewG->takeName(G);
741 removeUsers(G);
742 G->replaceAllUsesWith(NewG);
743 G->eraseFromParent();
744 }
745
746 LLVM_DEBUG(dbgs() << "writeThunk: " << H->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: " << H->
getName() << '\n'; } } while (false);
747 ++NumThunksWritten;
748}
749
750// Whether this function may be replaced by an alias
751static bool canCreateAliasFor(Function *F) {
752 if (!MergeFunctionsAliases || !F->hasGlobalUnnamedAddr())
753 return false;
754
755 // We should only see linkages supported by aliases here
756 assert(F->hasLocalLinkage() || F->hasExternalLinkage()(static_cast <bool> (F->hasLocalLinkage() || F->hasExternalLinkage
() || F->hasWeakLinkage() || F->hasLinkOnceLinkage()) ?
void (0) : __assert_fail ("F->hasLocalLinkage() || F->hasExternalLinkage() || F->hasWeakLinkage() || F->hasLinkOnceLinkage()"
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 757, __extension__
__PRETTY_FUNCTION__))
757 || F->hasWeakLinkage() || F->hasLinkOnceLinkage())(static_cast <bool> (F->hasLocalLinkage() || F->hasExternalLinkage
() || F->hasWeakLinkage() || F->hasLinkOnceLinkage()) ?
void (0) : __assert_fail ("F->hasLocalLinkage() || F->hasExternalLinkage() || F->hasWeakLinkage() || F->hasLinkOnceLinkage()"
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 757, __extension__
__PRETTY_FUNCTION__));
758 return true;
759}
760
761// Replace G with an alias to F (deleting function G)
762void MergeFunctions::writeAlias(Function *F, Function *G) {
763 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
764 PointerType *PtrType = G->getType();
765 auto *GA = GlobalAlias::create(G->getValueType(), PtrType->getAddressSpace(),
766 G->getLinkage(), "", BitcastF, G->getParent());
767
768 F->setAlignment(MaybeAlign(std::max(F->getAlignment(), G->getAlignment())));
769 GA->takeName(G);
770 GA->setVisibility(G->getVisibility());
771 GA->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
772
773 removeUsers(G);
774 G->replaceAllUsesWith(GA);
775 G->eraseFromParent();
776
777 LLVM_DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeAlias: " << GA->
getName() << '\n'; } } while (false);
778 ++NumAliasesWritten;
779}
780
781// Replace G with an alias to F if possible, or a thunk to F if
782// profitable. Returns false if neither is the case.
783bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
784 if (canCreateAliasFor(G)) {
785 writeAlias(F, G);
786 return true;
787 }
788 if (canCreateThunkFor(F)) {
789 writeThunk(F, G);
790 return true;
791 }
792 return false;
793}
794
795// Merge two equivalent functions. Upon completion, Function G is deleted.
796void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
797 if (F->isInterposable()) {
798 assert(G->isInterposable())(static_cast <bool> (G->isInterposable()) ? void (0)
: __assert_fail ("G->isInterposable()", "llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 798, __extension__ __PRETTY_FUNCTION__));
799
800 // Both writeThunkOrAlias() calls below must succeed, either because we can
801 // create aliases for G and NewF, or because a thunk for F is profitable.
802 // F here has the same signature as NewF below, so that's what we check.
803 if (!canCreateThunkFor(F) &&
804 (!canCreateAliasFor(F) || !canCreateAliasFor(G)))
805 return;
806
807 // Make them both thunks to the same internal function.
808 Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
809 F->getAddressSpace(), "", F->getParent());
810 NewF->copyAttributesFrom(F);
811 NewF->takeName(F);
812 removeUsers(F);
813 F->replaceAllUsesWith(NewF);
814
815 MaybeAlign MaxAlignment(std::max(G->getAlignment(), NewF->getAlignment()));
816
817 writeThunkOrAlias(F, G);
818 writeThunkOrAlias(F, NewF);
819
820 F->setAlignment(MaxAlignment);
821 F->setLinkage(GlobalValue::PrivateLinkage);
822 ++NumDoubleWeak;
823 ++NumFunctionsMerged;
824 } else {
825 // For better debugability, under MergeFunctionsPDI, we do not modify G's
826 // call sites to point to F even when within the same translation unit.
827 if (!G->isInterposable() && !MergeFunctionsPDI) {
828 if (G->hasGlobalUnnamedAddr()) {
829 // G might have been a key in our GlobalNumberState, and it's illegal
830 // to replace a key in ValueMap<GlobalValue *> with a non-global.
831 GlobalNumbers.erase(G);
832 // If G's address is not significant, replace it entirely.
833 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
834 removeUsers(G);
835 G->replaceAllUsesWith(BitcastF);
836 } else {
837 // Redirect direct callers of G to F. (See note on MergeFunctionsPDI
838 // above).
839 replaceDirectCallers(G, F);
840 }
841 }
842
843 // If G was internal then we may have replaced all uses of G with F. If so,
844 // stop here and delete G. There's no need for a thunk. (See note on
845 // MergeFunctionsPDI above).
846 if (G->isDiscardableIfUnused() && G->use_empty() && !MergeFunctionsPDI) {
847 G->eraseFromParent();
848 ++NumFunctionsMerged;
849 return;
850 }
851
852 if (writeThunkOrAlias(F, G)) {
853 ++NumFunctionsMerged;
854 }
855 }
856}
857
858/// Replace function F by function G.
859void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
860 Function *G) {
861 Function *F = FN.getFunc();
862 assert(FunctionComparator(F, G, &GlobalNumbers).compare() == 0 &&(static_cast <bool> (FunctionComparator(F, G, &GlobalNumbers
).compare() == 0 && "The two functions must be equal"
) ? void (0) : __assert_fail ("FunctionComparator(F, G, &GlobalNumbers).compare() == 0 && \"The two functions must be equal\""
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 863, __extension__
__PRETTY_FUNCTION__))
863 "The two functions must be equal")(static_cast <bool> (FunctionComparator(F, G, &GlobalNumbers
).compare() == 0 && "The two functions must be equal"
) ? void (0) : __assert_fail ("FunctionComparator(F, G, &GlobalNumbers).compare() == 0 && \"The two functions must be equal\""
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 863, __extension__
__PRETTY_FUNCTION__));
864
865 auto I = FNodesInTree.find(F);
866 assert(I != FNodesInTree.end() && "F should be in FNodesInTree")(static_cast <bool> (I != FNodesInTree.end() &&
"F should be in FNodesInTree") ? void (0) : __assert_fail ("I != FNodesInTree.end() && \"F should be in FNodesInTree\""
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 866, __extension__
__PRETTY_FUNCTION__));
867 assert(FNodesInTree.count(G) == 0 && "FNodesInTree should not contain G")(static_cast <bool> (FNodesInTree.count(G) == 0 &&
"FNodesInTree should not contain G") ? void (0) : __assert_fail
("FNodesInTree.count(G) == 0 && \"FNodesInTree should not contain G\""
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 867, __extension__
__PRETTY_FUNCTION__));
868
869 FnTreeType::iterator IterToFNInFnTree = I->second;
870 assert(&(*IterToFNInFnTree) == &FN && "F should map to FN in FNodesInTree.")(static_cast <bool> (&(*IterToFNInFnTree) == &FN
&& "F should map to FN in FNodesInTree.") ? void (0)
: __assert_fail ("&(*IterToFNInFnTree) == &FN && \"F should map to FN in FNodesInTree.\""
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 870, __extension__
__PRETTY_FUNCTION__));
871 // Remove F -> FN and insert G -> FN
872 FNodesInTree.erase(I);
873 FNodesInTree.insert({G, IterToFNInFnTree});
874 // Replace F with G in FN, which is stored inside the FnTree.
875 FN.replaceBy(G);
876}
877
878// Ordering for functions that are equal under FunctionComparator
879static bool isFuncOrderCorrect(const Function *F, const Function *G) {
880 if (F->isInterposable() != G->isInterposable()) {
881 // Strong before weak, because the weak function may call the strong
882 // one, but not the other way around.
883 return !F->isInterposable();
884 }
885 if (F->hasLocalLinkage() != G->hasLocalLinkage()) {
886 // External before local, because we definitely have to keep the external
887 // function, but may be able to drop the local one.
888 return !F->hasLocalLinkage();
889 }
890 // Impose a total order (by name) on the replacement of functions. This is
891 // important when operating on more than one module independently to prevent
892 // cycles of thunks calling each other when the modules are linked together.
893 return F->getName() <= G->getName();
894}
895
896// Insert a ComparableFunction into the FnTree, or merge it away if equal to one
897// that was already inserted.
898bool MergeFunctions::insert(Function *NewFunction) {
899 std::pair<FnTreeType::iterator, bool> Result =
900 FnTree.insert(FunctionNode(NewFunction));
901
902 if (Result.second) {
903 assert(FNodesInTree.count(NewFunction) == 0)(static_cast <bool> (FNodesInTree.count(NewFunction) ==
0) ? void (0) : __assert_fail ("FNodesInTree.count(NewFunction) == 0"
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 903, __extension__
__PRETTY_FUNCTION__));
904 FNodesInTree.insert({NewFunction, Result.first});
905 LLVM_DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Inserting as unique: " <<
NewFunction->getName() << '\n'; } } while (false)
906 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Inserting as unique: " <<
NewFunction->getName() << '\n'; } } while (false);
907 return false;
908 }
909
910 const FunctionNode &OldF = *Result.first;
911
912 if (!isFuncOrderCorrect(OldF.getFunc(), NewFunction)) {
913 // Swap the two functions.
914 Function *F = OldF.getFunc();
915 replaceFunctionInTree(*Result.first, NewFunction);
916 NewFunction = F;
917 assert(OldF.getFunc() != F && "Must have swapped the functions.")(static_cast <bool> (OldF.getFunc() != F && "Must have swapped the functions."
) ? void (0) : __assert_fail ("OldF.getFunc() != F && \"Must have swapped the functions.\""
, "llvm/lib/Transforms/IPO/MergeFunctions.cpp", 917, __extension__
__PRETTY_FUNCTION__));
918 }
919
920 LLVM_DEBUG(dbgs() << " " << OldF.getFunc()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " " << OldF.getFunc()
->getName() << " == " << NewFunction->getName
() << '\n'; } } while (false)
921 << " == " << NewFunction->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " " << OldF.getFunc()
->getName() << " == " << NewFunction->getName
() << '\n'; } } while (false);
922
923 Function *DeleteF = NewFunction;
924 mergeTwoFunctions(OldF.getFunc(), DeleteF);
925 return true;
926}
927
928// Remove a function from FnTree. If it was already in FnTree, add
929// it to Deferred so that we'll look at it in the next round.
930void MergeFunctions::remove(Function *F) {
931 auto I = FNodesInTree.find(F);
932 if (I != FNodesInTree.end()) {
933 LLVM_DEBUG(dbgs() << "Deferred " << F->getName() << ".\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Deferred " << F->getName
() << ".\n"; } } while (false);
934 FnTree.erase(I->second);
935 // I->second has been invalidated, remove it from the FNodesInTree map to
936 // preserve the invariant.
937 FNodesInTree.erase(I);
938 Deferred.emplace_back(F);
939 }
940}
941
942// For each instruction used by the value, remove() the function that contains
943// the instruction. This should happen right before a call to RAUW.
944void MergeFunctions::removeUsers(Value *V) {
945 for (User *U : V->users())
946 if (auto *I = dyn_cast<Instruction>(U))
947 remove(I->getFunction());
948}