Bug Summary

File:llvm/lib/Transforms/IPO/MergeFunctions.cpp
Warning:line 708, 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 -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-10/lib/clang/10.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/build-llvm/lib/Transforms/IPO -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/build-llvm/include -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/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-10/lib/clang/10.0.0/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-10~+201911111502510600c19528f1809/build-llvm/lib/Transforms/IPO -fdebug-prefix-map=/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809=. -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-2019-12-07-102640-14763-1 -x c++ /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/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/Pass.h"
119#include "llvm/Support/Casting.h"
120#include "llvm/Support/CommandLine.h"
121#include "llvm/Support/Debug.h"
122#include "llvm/Support/raw_ostream.h"
123#include "llvm/Transforms/IPO.h"
124#include "llvm/Transforms/Utils/FunctionComparator.h"
125#include <algorithm>
126#include <cassert>
127#include <iterator>
128#include <set>
129#include <utility>
130#include <vector>
131
132using namespace llvm;
133
134#define DEBUG_TYPE"mergefunc" "mergefunc"
135
136STATISTIC(NumFunctionsMerged, "Number of functions merged")static llvm::Statistic NumFunctionsMerged = {"mergefunc", "NumFunctionsMerged"
, "Number of functions merged"}
;
137STATISTIC(NumThunksWritten, "Number of thunks generated")static llvm::Statistic NumThunksWritten = {"mergefunc", "NumThunksWritten"
, "Number of thunks generated"}
;
138STATISTIC(NumAliasesWritten, "Number of aliases generated")static llvm::Statistic NumAliasesWritten = {"mergefunc", "NumAliasesWritten"
, "Number of aliases generated"}
;
139STATISTIC(NumDoubleWeak, "Number of new functions created")static llvm::Statistic NumDoubleWeak = {"mergefunc", "NumDoubleWeak"
, "Number of new functions created"}
;
140
141static cl::opt<unsigned> NumFunctionsForSanityCheck(
142 "mergefunc-sanity",
143 cl::desc("How many functions in module could be used for "
144 "MergeFunctions pass sanity check. "
145 "'0' disables this check. Works only with '-debug' key."),
146 cl::init(0), cl::Hidden);
147
148// Under option -mergefunc-preserve-debug-info we:
149// - Do not create a new function for a thunk.
150// - Retain the debug info for a thunk's parameters (and associated
151// instructions for the debug info) from the entry block.
152// Note: -debug will display the algorithm at work.
153// - Create debug-info for the call (to the shared implementation) made by
154// a thunk and its return value.
155// - Erase the rest of the function, retaining the (minimally sized) entry
156// block to create a thunk.
157// - Preserve a thunk's call site to point to the thunk even when both occur
158// within the same translation unit, to aid debugability. Note that this
159// behaviour differs from the underlying -mergefunc implementation which
160// modifies the thunk's call site to point to the shared implementation
161// when both occur within the same translation unit.
162static cl::opt<bool>
163 MergeFunctionsPDI("mergefunc-preserve-debug-info", cl::Hidden,
164 cl::init(false),
165 cl::desc("Preserve debug info in thunk when mergefunc "
166 "transformations are made."));
167
168static cl::opt<bool>
169 MergeFunctionsAliases("mergefunc-use-aliases", cl::Hidden,
170 cl::init(false),
171 cl::desc("Allow mergefunc to create aliases"));
172
173namespace {
174
175class FunctionNode {
176 mutable AssertingVH<Function> F;
177 FunctionComparator::FunctionHash Hash;
178
179public:
180 // Note the hash is recalculated potentially multiple times, but it is cheap.
181 FunctionNode(Function *F)
182 : F(F), Hash(FunctionComparator::functionHash(*F)) {}
183
184 Function *getFunc() const { return F; }
185 FunctionComparator::FunctionHash getHash() const { return Hash; }
186
187 /// Replace the reference to the function F by the function G, assuming their
188 /// implementations are equal.
189 void replaceBy(Function *G) const {
190 F = G;
191 }
192};
193
194/// MergeFunctions finds functions which will generate identical machine code,
195/// by considering all pointer types to be equivalent. Once identified,
196/// MergeFunctions will fold them by replacing a call to one to a call to a
197/// bitcast of the other.
198class MergeFunctions : public ModulePass {
199public:
200 static char ID;
201
202 MergeFunctions()
203 : ModulePass(ID), FnTree(FunctionNodeCmp(&GlobalNumbers)) {
204 initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
205 }
206
207 bool runOnModule(Module &M) override;
208
209private:
210 // The function comparison operator is provided here so that FunctionNodes do
211 // not need to become larger with another pointer.
212 class FunctionNodeCmp {
213 GlobalNumberState* GlobalNumbers;
214
215 public:
216 FunctionNodeCmp(GlobalNumberState* GN) : GlobalNumbers(GN) {}
217
218 bool operator()(const FunctionNode &LHS, const FunctionNode &RHS) const {
219 // Order first by hashes, then full function comparison.
220 if (LHS.getHash() != RHS.getHash())
221 return LHS.getHash() < RHS.getHash();
222 FunctionComparator FCmp(LHS.getFunc(), RHS.getFunc(), GlobalNumbers);
223 return FCmp.compare() == -1;
224 }
225 };
226 using FnTreeType = std::set<FunctionNode, FunctionNodeCmp>;
227
228 GlobalNumberState GlobalNumbers;
229
230 /// A work queue of functions that may have been modified and should be
231 /// analyzed again.
232 std::vector<WeakTrackingVH> Deferred;
233
234#ifndef NDEBUG
235 /// Checks the rules of order relation introduced among functions set.
236 /// Returns true, if sanity check has been passed, and false if failed.
237 bool doSanityCheck(std::vector<WeakTrackingVH> &Worklist);
238#endif
239
240 /// Insert a ComparableFunction into the FnTree, or merge it away if it's
241 /// equal to one that's already present.
242 bool insert(Function *NewFunction);
243
244 /// Remove a Function from the FnTree and queue it up for a second sweep of
245 /// analysis.
246 void remove(Function *F);
247
248 /// Find the functions that use this Value and remove them from FnTree and
249 /// queue the functions.
250 void removeUsers(Value *V);
251
252 /// Replace all direct calls of Old with calls of New. Will bitcast New if
253 /// necessary to make types match.
254 void replaceDirectCallers(Function *Old, Function *New);
255
256 /// Merge two equivalent functions. Upon completion, G may be deleted, or may
257 /// be converted into a thunk. In either case, it should never be visited
258 /// again.
259 void mergeTwoFunctions(Function *F, Function *G);
260
261 /// Fill PDIUnrelatedWL with instructions from the entry block that are
262 /// unrelated to parameter related debug info.
263 void filterInstsUnrelatedToPDI(BasicBlock *GEntryBlock,
264 std::vector<Instruction *> &PDIUnrelatedWL);
265
266 /// Erase the rest of the CFG (i.e. barring the entry block).
267 void eraseTail(Function *G);
268
269 /// Erase the instructions in PDIUnrelatedWL as they are unrelated to the
270 /// parameter debug info, from the entry block.
271 void eraseInstsUnrelatedToPDI(std::vector<Instruction *> &PDIUnrelatedWL);
272
273 /// Replace G with a simple tail call to bitcast(F). Also (unless
274 /// MergeFunctionsPDI holds) replace direct uses of G with bitcast(F),
275 /// delete G.
276 void writeThunk(Function *F, Function *G);
277
278 // Replace G with an alias to F (deleting function G)
279 void writeAlias(Function *F, Function *G);
280
281 // Replace G with an alias to F if possible, or a thunk to F if possible.
282 // Returns false if neither is the case.
283 bool writeThunkOrAlias(Function *F, Function *G);
284
285 /// Replace function F with function G in the function tree.
286 void replaceFunctionInTree(const FunctionNode &FN, Function *G);
287
288 /// The set of all distinct functions. Use the insert() and remove() methods
289 /// to modify it. The map allows efficient lookup and deferring of Functions.
290 FnTreeType FnTree;
291
292 // Map functions to the iterators of the FunctionNode which contains them
293 // in the FnTree. This must be updated carefully whenever the FnTree is
294 // modified, i.e. in insert(), remove(), and replaceFunctionInTree(), to avoid
295 // dangling iterators into FnTree. The invariant that preserves this is that
296 // there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
297 DenseMap<AssertingVH<Function>, FnTreeType::iterator> FNodesInTree;
298};
299
300} // end anonymous namespace
301
302char MergeFunctions::ID = 0;
303
304INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)static void *initializeMergeFunctionsPassOnce(PassRegistry &
Registry) { PassInfo *PI = new PassInfo( "Merge Functions", "mergefunc"
, &MergeFunctions::ID, PassInfo::NormalCtor_t(callDefaultCtor
<MergeFunctions>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeMergeFunctionsPassFlag
; void llvm::initializeMergeFunctionsPass(PassRegistry &Registry
) { llvm::call_once(InitializeMergeFunctionsPassFlag, initializeMergeFunctionsPassOnce
, std::ref(Registry)); }
305
306ModulePass *llvm::createMergeFunctionsPass() {
307 return new MergeFunctions();
308}
309
310#ifndef NDEBUG
311bool MergeFunctions::doSanityCheck(std::vector<WeakTrackingVH> &Worklist) {
312 if (const unsigned Max = NumFunctionsForSanityCheck) {
313 unsigned TripleNumber = 0;
314 bool Valid = true;
315
316 dbgs() << "MERGEFUNC-SANITY: Started for first " << Max << " functions.\n";
317
318 unsigned i = 0;
319 for (std::vector<WeakTrackingVH>::iterator I = Worklist.begin(),
320 E = Worklist.end();
321 I != E && i < Max; ++I, ++i) {
322 unsigned j = i;
323 for (std::vector<WeakTrackingVH>::iterator J = I; J != E && j < Max;
324 ++J, ++j) {
325 Function *F1 = cast<Function>(*I);
326 Function *F2 = cast<Function>(*J);
327 int Res1 = FunctionComparator(F1, F2, &GlobalNumbers).compare();
328 int Res2 = FunctionComparator(F2, F1, &GlobalNumbers).compare();
329
330 // If F1 <= F2, then F2 >= F1, otherwise report failure.
331 if (Res1 != -Res2) {
332 dbgs() << "MERGEFUNC-SANITY: Non-symmetric; triple: " << TripleNumber
333 << "\n";
334 dbgs() << *F1 << '\n' << *F2 << '\n';
335 Valid = false;
336 }
337
338 if (Res1 == 0)
339 continue;
340
341 unsigned k = j;
342 for (std::vector<WeakTrackingVH>::iterator K = J; K != E && k < Max;
343 ++k, ++K, ++TripleNumber) {
344 if (K == J)
345 continue;
346
347 Function *F3 = cast<Function>(*K);
348 int Res3 = FunctionComparator(F1, F3, &GlobalNumbers).compare();
349 int Res4 = FunctionComparator(F2, F3, &GlobalNumbers).compare();
350
351 bool Transitive = true;
352
353 if (Res1 != 0 && Res1 == Res4) {
354 // F1 > F2, F2 > F3 => F1 > F3
355 Transitive = Res3 == Res1;
356 } else if (Res3 != 0 && Res3 == -Res4) {
357 // F1 > F3, F3 > F2 => F1 > F2
358 Transitive = Res3 == Res1;
359 } else if (Res4 != 0 && -Res3 == Res4) {
360 // F2 > F3, F3 > F1 => F2 > F1
361 Transitive = Res4 == -Res1;
362 }
363
364 if (!Transitive) {
365 dbgs() << "MERGEFUNC-SANITY: Non-transitive; triple: "
366 << TripleNumber << "\n";
367 dbgs() << "Res1, Res3, Res4: " << Res1 << ", " << Res3 << ", "
368 << Res4 << "\n";
369 dbgs() << *F1 << '\n' << *F2 << '\n' << *F3 << '\n';
370 Valid = false;
371 }
372 }
373 }
374 }
375
376 dbgs() << "MERGEFUNC-SANITY: " << (Valid ? "Passed." : "Failed.") << "\n";
377 return Valid;
378 }
379 return true;
380}
381#endif
382
383/// Check whether \p F is eligible for function merging.
384static bool isEligibleForMerging(Function &F) {
385 return !F.isDeclaration() && !F.hasAvailableExternallyLinkage();
386}
387
388bool MergeFunctions::runOnModule(Module &M) {
389 if (skipModule(M))
1
Assuming the condition is false
2
Taking false branch
390 return false;
391
392 bool Changed = false;
393
394 // All functions in the module, ordered by hash. Functions with a unique
395 // hash value are easily eliminated.
396 std::vector<std::pair<FunctionComparator::FunctionHash, Function *>>
397 HashedFuncs;
398 for (Function &Func : M) {
399 if (isEligibleForMerging(Func)) {
400 HashedFuncs.push_back({FunctionComparator::functionHash(Func), &Func});
401 }
402 }
403
404 llvm::stable_sort(HashedFuncs, less_first());
405
406 auto S = HashedFuncs.begin();
407 for (auto I = HashedFuncs.begin(), IE = HashedFuncs.end(); I != IE; ++I) {
3
Loop condition is false. Execution continues on line 417
408 // If the hash value matches the previous value or the next one, we must
409 // consider merging it. Otherwise it is dropped and never considered again.
410 if ((I != S && std::prev(I)->first == I->first) ||
411 (std::next(I) != IE && std::next(I)->first == I->first) ) {
412 Deferred.push_back(WeakTrackingVH(I->second));
413 }
414 }
415
416 do {
417 std::vector<WeakTrackingVH> Worklist;
418 Deferred.swap(Worklist);
419
420 LLVM_DEBUG(doSanityCheck(Worklist))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { doSanityCheck(Worklist); } } while (false)
;
4
Assuming 'DebugFlag' is false
5
Loop condition is false. Exiting loop
421
422 LLVM_DEBUG
5.1
'DebugFlag' is false
(dbgs() << "size of module: " << M.size() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "size of module: " << M
.size() << '\n'; } } while (false)
;
6
Loop condition is false. Exiting loop
423 LLVM_DEBUG
6.1
'DebugFlag' is false
(dbgs() << "size of worklist: " << Worklist.size() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "size of worklist: " <<
Worklist.size() << '\n'; } } while (false)
;
7
Loop condition is false. Exiting loop
424
425 // Insert functions and merge them.
426 for (WeakTrackingVH &I : Worklist) {
427 if (!I)
8
Assuming the condition is false
9
Taking false branch
428 continue;
429 Function *F = cast<Function>(I);
430 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage()) {
10
Assuming the condition is true
11
Taking true branch
431 Changed |= insert(F);
12
Calling 'MergeFunctions::insert'
432 }
433 }
434 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)
;
435 } while (!Deferred.empty());
436
437 FnTree.clear();
438 FNodesInTree.clear();
439 GlobalNumbers.clear();
440
441 return Changed;
442}
443
444// Replace direct callers of Old with New.
445void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
446 Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
447 for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
448 Use *U = &*UI;
449 ++UI;
450 CallSite CS(U->getUser());
451 if (CS && CS.isCallee(U)) {
452 // Transfer the called function's attributes to the call site. Due to the
453 // bitcast we will 'lose' ABI changing attributes because the 'called
454 // function' is no longer a Function* but the bitcast. Code that looks up
455 // the attributes from the called function will fail.
456
457 // FIXME: This is not actually true, at least not anymore. The callsite
458 // will always have the same ABI affecting attributes as the callee,
459 // because otherwise the original input has UB. Note that Old and New
460 // always have matching ABI, so no attributes need to be changed.
461 // Transferring other attributes may help other optimizations, but that
462 // should be done uniformly and not in this ad-hoc way.
463 auto &Context = New->getContext();
464 auto NewPAL = New->getAttributes();
465 SmallVector<AttributeSet, 4> NewArgAttrs;
466 for (unsigned argIdx = 0; argIdx < CS.arg_size(); argIdx++)
467 NewArgAttrs.push_back(NewPAL.getParamAttributes(argIdx));
468 // Don't transfer attributes from the function to the callee. Function
469 // attributes typically aren't relevant to the calling convention or ABI.
470 CS.setAttributes(AttributeList::get(Context, /*FnAttrs=*/AttributeSet(),
471 NewPAL.getRetAttributes(),
472 NewArgAttrs));
473
474 remove(CS.getInstruction()->getFunction());
475 U->set(BitcastNew);
476 }
477 }
478}
479
480// Helper for writeThunk,
481// Selects proper bitcast operation,
482// but a bit simpler then CastInst::getCastOpcode.
483static Value *createCast(IRBuilder<> &Builder, Value *V, Type *DestTy) {
484 Type *SrcTy = V->getType();
485 if (SrcTy->isStructTy()) {
486 assert(DestTy->isStructTy())((DestTy->isStructTy()) ? static_cast<void> (0) : __assert_fail
("DestTy->isStructTy()", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 486, __PRETTY_FUNCTION__))
;
487 assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements())((SrcTy->getStructNumElements() == DestTy->getStructNumElements
()) ? static_cast<void> (0) : __assert_fail ("SrcTy->getStructNumElements() == DestTy->getStructNumElements()"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 487, __PRETTY_FUNCTION__))
;
488 Value *Result = UndefValue::get(DestTy);
489 for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) {
490 Value *Element = createCast(
491 Builder, Builder.CreateExtractValue(V, makeArrayRef(I)),
492 DestTy->getStructElementType(I));
493
494 Result =
495 Builder.CreateInsertValue(Result, Element, makeArrayRef(I));
496 }
497 return Result;
498 }
499 assert(!DestTy->isStructTy())((!DestTy->isStructTy()) ? static_cast<void> (0) : __assert_fail
("!DestTy->isStructTy()", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 499, __PRETTY_FUNCTION__))
;
500 if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
501 return Builder.CreateIntToPtr(V, DestTy);
502 else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
503 return Builder.CreatePtrToInt(V, DestTy);
504 else
505 return Builder.CreateBitCast(V, DestTy);
506}
507
508// Erase the instructions in PDIUnrelatedWL as they are unrelated to the
509// parameter debug info, from the entry block.
510void MergeFunctions::eraseInstsUnrelatedToPDI(
511 std::vector<Instruction *> &PDIUnrelatedWL) {
512 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)
513 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)
514 "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)
515 "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)
;
516 while (!PDIUnrelatedWL.empty()) {
517 Instruction *I = PDIUnrelatedWL.back();
518 LLVM_DEBUG(dbgs() << " Deleting Instruction: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deleting Instruction: "; }
} while (false)
;
519 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false)
;
520 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
521 I->eraseFromParent();
522 PDIUnrelatedWL.pop_back();
523 }
524 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)
525 "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)
;
526}
527
528// Reduce G to its entry block.
529void MergeFunctions::eraseTail(Function *G) {
530 std::vector<BasicBlock *> WorklistBB;
531 for (Function::iterator BBI = std::next(G->begin()), BBE = G->end();
532 BBI != BBE; ++BBI) {
533 BBI->dropAllReferences();
534 WorklistBB.push_back(&*BBI);
535 }
536 while (!WorklistBB.empty()) {
537 BasicBlock *BB = WorklistBB.back();
538 BB->eraseFromParent();
539 WorklistBB.pop_back();
540 }
541}
542
543// We are interested in the following instructions from the entry block as being
544// related to parameter debug info:
545// - @llvm.dbg.declare
546// - stores from the incoming parameters to locations on the stack-frame
547// - allocas that create these locations on the stack-frame
548// - @llvm.dbg.value
549// - the entry block's terminator
550// The rest are unrelated to debug info for the parameters; fill up
551// PDIUnrelatedWL with such instructions.
552void MergeFunctions::filterInstsUnrelatedToPDI(
553 BasicBlock *GEntryBlock, std::vector<Instruction *> &PDIUnrelatedWL) {
554 std::set<Instruction *> PDIRelated;
555 for (BasicBlock::iterator BI = GEntryBlock->begin(), BIE = GEntryBlock->end();
556 BI != BIE; ++BI) {
557 if (auto *DVI = dyn_cast<DbgValueInst>(&*BI)) {
558 LLVM_DEBUG(dbgs() << " Deciding: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deciding: "; } } 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 DILocalVariable *DILocVar = DVI->getVariable();
562 if (DILocVar->isParameter()) {
563 LLVM_DEBUG(dbgs() << " Include (parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include (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 PDIRelated.insert(&*BI);
567 } else {
568 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} 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 }
572 } else if (auto *DDI = dyn_cast<DbgDeclareInst>(&*BI)) {
573 LLVM_DEBUG(dbgs() << " Deciding: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Deciding: "; } } while (false
)
;
574 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
575 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
576 DILocalVariable *DILocVar = DDI->getVariable();
577 if (DILocVar->isParameter()) {
578 LLVM_DEBUG(dbgs() << " Parameter: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Parameter: "; } } while (
false)
;
579 LLVM_DEBUG(DILocVar->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { DILocVar->print(dbgs()); } } while (false
)
;
580 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
581 if (AI) {
582 LLVM_DEBUG(dbgs() << " Processing alloca users: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Processing alloca users: "
; } } while (false)
;
583 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
584 for (User *U : AI->users()) {
585 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
586 if (Value *Arg = SI->getValueOperand()) {
587 if (dyn_cast<Argument>(Arg)) {
588 LLVM_DEBUG(dbgs() << " Include: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include: "; } } while (false
)
;
589 LLVM_DEBUG(AI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { AI->print(dbgs()); } } while (false)
;
590 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
591 PDIRelated.insert(AI);
592 LLVM_DEBUG(dbgs() << " Include (parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include (parameter): "; }
} while (false)
;
593 LLVM_DEBUG(SI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { SI->print(dbgs()); } } while (false)
;
594 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
595 PDIRelated.insert(SI);
596 LLVM_DEBUG(dbgs() << " Include: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Include: "; } } while (false
)
;
597 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
598 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
599 PDIRelated.insert(&*BI);
600 } else {
601 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} while (false)
;
602 LLVM_DEBUG(SI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { SI->print(dbgs()); } } while (false)
;
603 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
604 }
605 }
606 } else {
607 LLVM_DEBUG(dbgs() << " Defer: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Defer: "; } } while (false
)
;
608 LLVM_DEBUG(U->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { U->print(dbgs()); } } while (false)
;
609 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
610 }
611 }
612 } else {
613 LLVM_DEBUG(dbgs() << " Delete (alloca NULL): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (alloca NULL): "; }
} 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 {
618 LLVM_DEBUG(dbgs() << " Delete (!parameter): ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Delete (!parameter): "; }
} 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 }
622 } else if (BI->isTerminator() && &*BI == GEntryBlock->getTerminator()) {
623 LLVM_DEBUG(dbgs() << " Will Include Terminator: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Will Include Terminator: "
; } } 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 PDIRelated.insert(&*BI);
627 } else {
628 LLVM_DEBUG(dbgs() << " Defer: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Defer: "; } } while (false
)
;
629 LLVM_DEBUG(BI->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { BI->print(dbgs()); } } while (false)
;
630 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
631 }
632 }
633 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
634 dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " Report parameter debug info related/related instructions: {\n"
; } } while (false)
635 << " 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)
;
636 for (BasicBlock::iterator BI = GEntryBlock->begin(), BE = GEntryBlock->end();
637 BI != BE; ++BI) {
638
639 Instruction *I = &*BI;
640 if (PDIRelated.find(I) == PDIRelated.end()) {
641 LLVM_DEBUG(dbgs() << " !PDIRelated: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " !PDIRelated: "; } } while
(false)
;
642 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false)
;
643 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
644 PDIUnrelatedWL.push_back(I);
645 } else {
646 LLVM_DEBUG(dbgs() << " PDIRelated: ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " PDIRelated: "; } } while
(false)
;
647 LLVM_DEBUG(I->print(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { I->print(dbgs()); } } while (false)
;
648 LLVM_DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "\n"; } } while (false)
;
649 }
650 }
651 LLVM_DEBUG(dbgs() << " }\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " }\n"; } } while (false)
;
652}
653
654/// Whether this function may be replaced by a forwarding thunk.
655static bool canCreateThunkFor(Function *F) {
656 if (F->isVarArg())
657 return false;
658
659 // Don't merge tiny functions using a thunk, since it can just end up
660 // making the function larger.
661 if (F->size() == 1) {
662 if (F->front().size() <= 2) {
663 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)
664 << " 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)
;
665 return false;
666 }
667 }
668 return true;
669}
670
671// Replace G with a simple tail call to bitcast(F). Also (unless
672// MergeFunctionsPDI holds) replace direct uses of G with bitcast(F),
673// delete G. Under MergeFunctionsPDI, we use G itself for creating
674// the thunk as we preserve the debug info (and associated instructions)
675// from G's entry block pertaining to G's incoming arguments which are
676// passed on as corresponding arguments in the call that G makes to F.
677// For better debugability, under MergeFunctionsPDI, we do not modify G's
678// call sites to point to F even when within the same translation unit.
679void MergeFunctions::writeThunk(Function *F, Function *G) {
680 BasicBlock *GEntryBlock = nullptr;
681 std::vector<Instruction *> PDIUnrelatedWL;
682 BasicBlock *BB = nullptr;
683 Function *NewG = nullptr;
27
'NewG' initialized to a null pointer value
684 if (MergeFunctionsPDI) {
28
Assuming the condition is true
29
Taking true branch
685 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)
30
Assuming 'DebugFlag' is false
31
Loop condition is false. Exiting loop
686 "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)
687 << 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)
;
688 GEntryBlock = &G->getEntryBlock();
689 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
32
Assuming 'DebugFlag' is false
33
Loop condition is false. Exiting loop
690 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)
691 "debug info for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
692 << G->getName() << "() {\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) filter parameter related "
"debug info for " << G->getName() << "() {\n"
; } } while (false)
;
693 filterInstsUnrelatedToPDI(GEntryBlock, PDIUnrelatedWL);
694 GEntryBlock->getTerminator()->eraseFromParent();
695 BB = GEntryBlock;
696 } else {
697 NewG = Function::Create(G->getFunctionType(), G->getLinkage(),
698 G->getAddressSpace(), "", G->getParent());
699 NewG->setComdat(G->getComdat());
700 BB = BasicBlock::Create(F->getContext(), "", NewG);
701 }
702
703 IRBuilder<> Builder(BB);
704 Function *H = MergeFunctionsPDI ? G : NewG;
34
Assuming the condition is false
35
'?' condition is false
36
'H' initialized to a null pointer value
705 SmallVector<Value *, 16> Args;
706 unsigned i = 0;
707 FunctionType *FFTy = F->getFunctionType();
708 for (Argument &AI : H->args()) {
37
Called C++ object pointer is null
709 Args.push_back(createCast(Builder, &AI, FFTy->getParamType(i)));
710 ++i;
711 }
712
713 CallInst *CI = Builder.CreateCall(F, Args);
714 ReturnInst *RI = nullptr;
715 CI->setTailCall();
716 CI->setCallingConv(F->getCallingConv());
717 CI->setAttributes(F->getAttributes());
718 if (H->getReturnType()->isVoidTy()) {
719 RI = Builder.CreateRetVoid();
720 } else {
721 RI = Builder.CreateRet(createCast(Builder, CI, H->getReturnType()));
722 }
723
724 if (MergeFunctionsPDI) {
725 DISubprogram *DIS = G->getSubprogram();
726 if (DIS) {
727 DebugLoc CIDbgLoc = DebugLoc::get(DIS->getScopeLine(), 0, DIS);
728 DebugLoc RIDbgLoc = DebugLoc::get(DIS->getScopeLine(), 0, DIS);
729 CI->setDebugLoc(CIDbgLoc);
730 RI->setDebugLoc(RIDbgLoc);
731 } else {
732 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
733 dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
734 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: (MergeFunctionsPDI) No DISubprogram for "
<< G->getName() << "()\n"; } } while (false)
;
735 }
736 eraseTail(G);
737 eraseInstsUnrelatedToPDI(PDIUnrelatedWL);
738 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false)
739 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)
740 << G->getName() << "()\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "} // End of parameter related debug info filtering for: "
<< G->getName() << "()\n"; } } while (false)
;
741 } else {
742 NewG->copyAttributesFrom(G);
743 NewG->takeName(G);
744 removeUsers(G);
745 G->replaceAllUsesWith(NewG);
746 G->eraseFromParent();
747 }
748
749 LLVM_DEBUG(dbgs() << "writeThunk: " << H->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeThunk: " << H->
getName() << '\n'; } } while (false)
;
750 ++NumThunksWritten;
751}
752
753// Whether this function may be replaced by an alias
754static bool canCreateAliasFor(Function *F) {
755 if (!MergeFunctionsAliases || !F->hasGlobalUnnamedAddr())
756 return false;
757
758 // We should only see linkages supported by aliases here
759 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 760, __PRETTY_FUNCTION__))
760 || 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 760, __PRETTY_FUNCTION__))
;
761 return true;
762}
763
764// Replace G with an alias to F (deleting function G)
765void MergeFunctions::writeAlias(Function *F, Function *G) {
766 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
767 PointerType *PtrType = G->getType();
768 auto *GA = GlobalAlias::create(
769 PtrType->getElementType(), PtrType->getAddressSpace(),
770 G->getLinkage(), "", BitcastF, G->getParent());
771
772 F->setAlignment(MaybeAlign(std::max(F->getAlignment(), G->getAlignment())));
773 GA->takeName(G);
774 GA->setVisibility(G->getVisibility());
775 GA->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
776
777 removeUsers(G);
778 G->replaceAllUsesWith(GA);
779 G->eraseFromParent();
780
781 LLVM_DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "writeAlias: " << GA->
getName() << '\n'; } } while (false)
;
782 ++NumAliasesWritten;
783}
784
785// Replace G with an alias to F if possible, or a thunk to F if
786// profitable. Returns false if neither is the case.
787bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
788 if (canCreateAliasFor(G)) {
24
Taking false branch
789 writeAlias(F, G);
790 return true;
791 }
792 if (canCreateThunkFor(F)) {
25
Taking true branch
793 writeThunk(F, G);
26
Calling 'MergeFunctions::writeThunk'
794 return true;
795 }
796 return false;
797}
798
799// Merge two equivalent functions. Upon completion, Function G is deleted.
800void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
801 if (F->isInterposable()) {
19
Taking false branch
802 assert(G->isInterposable())((G->isInterposable()) ? static_cast<void> (0) : __assert_fail
("G->isInterposable()", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 802, __PRETTY_FUNCTION__))
;
803
804 // Both writeThunkOrAlias() calls below must succeed, either because we can
805 // create aliases for G and NewF, or because a thunk for F is profitable.
806 // F here has the same signature as NewF below, so that's what we check.
807 if (!canCreateThunkFor(F) &&
808 (!canCreateAliasFor(F) || !canCreateAliasFor(G)))
809 return;
810
811 // Make them both thunks to the same internal function.
812 Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
813 F->getAddressSpace(), "", F->getParent());
814 NewF->copyAttributesFrom(F);
815 NewF->takeName(F);
816 removeUsers(F);
817 F->replaceAllUsesWith(NewF);
818
819 MaybeAlign MaxAlignment(std::max(G->getAlignment(), NewF->getAlignment()));
820
821 writeThunkOrAlias(F, G);
822 writeThunkOrAlias(F, NewF);
823
824 F->setAlignment(MaxAlignment);
825 F->setLinkage(GlobalValue::PrivateLinkage);
826 ++NumDoubleWeak;
827 ++NumFunctionsMerged;
828 } else {
829 // For better debugability, under MergeFunctionsPDI, we do not modify G's
830 // call sites to point to F even when within the same translation unit.
831 if (!G->isInterposable() && !MergeFunctionsPDI) {
20
Assuming the condition is false
21
Taking false branch
832 if (G->hasGlobalUnnamedAddr()) {
833 // G might have been a key in our GlobalNumberState, and it's illegal
834 // to replace a key in ValueMap<GlobalValue *> with a non-global.
835 GlobalNumbers.erase(G);
836 // If G's address is not significant, replace it entirely.
837 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
838 removeUsers(G);
839 G->replaceAllUsesWith(BitcastF);
840 } else {
841 // Redirect direct callers of G to F. (See note on MergeFunctionsPDI
842 // above).
843 replaceDirectCallers(G, F);
844 }
845 }
846
847 // If G was internal then we may have replaced all uses of G with F. If so,
848 // stop here and delete G. There's no need for a thunk. (See note on
849 // MergeFunctionsPDI above).
850 if (G->isDiscardableIfUnused() && G->use_empty() && !MergeFunctionsPDI) {
22
Assuming the condition is false
851 G->eraseFromParent();
852 ++NumFunctionsMerged;
853 return;
854 }
855
856 if (writeThunkOrAlias(F, G)) {
23
Calling 'MergeFunctions::writeThunkOrAlias'
857 ++NumFunctionsMerged;
858 }
859 }
860}
861
862/// Replace function F by function G.
863void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
864 Function *G) {
865 Function *F = FN.getFunc();
866 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 867, __PRETTY_FUNCTION__))
867 "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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 867, __PRETTY_FUNCTION__))
;
868
869 auto I = FNodesInTree.find(F);
870 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 870, __PRETTY_FUNCTION__))
;
871 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 871, __PRETTY_FUNCTION__))
;
872
873 FnTreeType::iterator IterToFNInFnTree = I->second;
874 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 874, __PRETTY_FUNCTION__))
;
875 // Remove F -> FN and insert G -> FN
876 FNodesInTree.erase(I);
877 FNodesInTree.insert({G, IterToFNInFnTree});
878 // Replace F with G in FN, which is stored inside the FnTree.
879 FN.replaceBy(G);
880}
881
882// Ordering for functions that are equal under FunctionComparator
883static bool isFuncOrderCorrect(const Function *F, const Function *G) {
884 if (F->isInterposable() != G->isInterposable()) {
885 // Strong before weak, because the weak function may call the strong
886 // one, but not the other way around.
887 return !F->isInterposable();
888 }
889 if (F->hasLocalLinkage() != G->hasLocalLinkage()) {
890 // External before local, because we definitely have to keep the external
891 // function, but may be able to drop the local one.
892 return !F->hasLocalLinkage();
893 }
894 // Impose a total order (by name) on the replacement of functions. This is
895 // important when operating on more than one module independently to prevent
896 // cycles of thunks calling each other when the modules are linked together.
897 return F->getName() <= G->getName();
898}
899
900// Insert a ComparableFunction into the FnTree, or merge it away if equal to one
901// that was already inserted.
902bool MergeFunctions::insert(Function *NewFunction) {
903 std::pair<FnTreeType::iterator, bool> Result =
904 FnTree.insert(FunctionNode(NewFunction));
905
906 if (Result.second) {
13
Assuming field 'second' is false
14
Taking false branch
907 assert(FNodesInTree.count(NewFunction) == 0)((FNodesInTree.count(NewFunction) == 0) ? static_cast<void
> (0) : __assert_fail ("FNodesInTree.count(NewFunction) == 0"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 907, __PRETTY_FUNCTION__))
;
908 FNodesInTree.insert({NewFunction, Result.first});
909 LLVM_DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Inserting as unique: " <<
NewFunction->getName() << '\n'; } } while (false)
910 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Inserting as unique: " <<
NewFunction->getName() << '\n'; } } while (false)
;
911 return false;
912 }
913
914 const FunctionNode &OldF = *Result.first;
915
916 if (!isFuncOrderCorrect(OldF.getFunc(), NewFunction)) {
15
Taking false branch
917 // Swap the two functions.
918 Function *F = OldF.getFunc();
919 replaceFunctionInTree(*Result.first, NewFunction);
920 NewFunction = F;
921 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-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/MergeFunctions.cpp"
, 921, __PRETTY_FUNCTION__))
;
922 }
923
924 LLVM_DEBUG(dbgs() << " " << OldF.getFunc()->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " " << OldF.getFunc()
->getName() << " == " << NewFunction->getName
() << '\n'; } } while (false)
16
Assuming 'DebugFlag' is false
17
Loop condition is false. Exiting loop
925 << " == " << NewFunction->getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << " " << OldF.getFunc()
->getName() << " == " << NewFunction->getName
() << '\n'; } } while (false)
;
926
927 Function *DeleteF = NewFunction;
928 mergeTwoFunctions(OldF.getFunc(), DeleteF);
18
Calling 'MergeFunctions::mergeTwoFunctions'
929 return true;
930}
931
932// Remove a function from FnTree. If it was already in FnTree, add
933// it to Deferred so that we'll look at it in the next round.
934void MergeFunctions::remove(Function *F) {
935 auto I = FNodesInTree.find(F);
936 if (I != FNodesInTree.end()) {
937 LLVM_DEBUG(dbgs() << "Deferred " << F->getName() << ".\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mergefunc")) { dbgs() << "Deferred " << F->getName
() << ".\n"; } } while (false)
;
938 FnTree.erase(I->second);
939 // I->second has been invalidated, remove it from the FNodesInTree map to
940 // preserve the invariant.
941 FNodesInTree.erase(I);
942 Deferred.emplace_back(F);
943 }
944}
945
946// For each instruction used by the value, remove() the function that contains
947// the instruction. This should happen right before a call to RAUW.
948void MergeFunctions::removeUsers(Value *V) {
949 for (User *U : V->users())
950 if (auto *I = dyn_cast<Instruction>(U))
951 remove(I->getFunction());
952}