Bug Summary

File:llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
Warning:line 1229, column 18
Access to field 'TheKind' results in a dereference of a null pointer (loaded from variable 'Res')

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 WholeProgramDevirt.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 -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-2019-12-05-225554-32688-1 -x c++ /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
1//===- WholeProgramDevirt.cpp - Whole program virtual call optimization ---===//
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 implements whole program optimization of virtual calls in cases
10// where we know (via !type metadata) that the list of callees is fixed. This
11// includes the following:
12// - Single implementation devirtualization: if a virtual call has a single
13// possible callee, replace all calls with a direct call to that callee.
14// - Virtual constant propagation: if the virtual function's return type is an
15// integer <=64 bits and all possible callees are readnone, for each class and
16// each list of constant arguments: evaluate the function, store the return
17// value alongside the virtual table, and rewrite each virtual call as a load
18// from the virtual table.
19// - Uniform return value optimization: if the conditions for virtual constant
20// propagation hold and each function returns the same constant value, replace
21// each virtual call with that constant.
22// - Unique return value optimization for i1 return values: if the conditions
23// for virtual constant propagation hold and a single vtable's function
24// returns 0, or a single vtable's function returns 1, replace each virtual
25// call with a comparison of the vptr against that vtable's address.
26//
27// This pass is intended to be used during the regular and thin LTO pipelines:
28//
29// During regular LTO, the pass determines the best optimization for each
30// virtual call and applies the resolutions directly to virtual calls that are
31// eligible for virtual call optimization (i.e. calls that use either of the
32// llvm.assume(llvm.type.test) or llvm.type.checked.load intrinsics).
33//
34// During hybrid Regular/ThinLTO, the pass operates in two phases:
35// - Export phase: this is run during the thin link over a single merged module
36// that contains all vtables with !type metadata that participate in the link.
37// The pass computes a resolution for each virtual call and stores it in the
38// type identifier summary.
39// - Import phase: this is run during the thin backends over the individual
40// modules. The pass applies the resolutions previously computed during the
41// import phase to each eligible virtual call.
42//
43// During ThinLTO, the pass operates in two phases:
44// - Export phase: this is run during the thin link over the index which
45// contains a summary of all vtables with !type metadata that participate in
46// the link. It computes a resolution for each virtual call and stores it in
47// the type identifier summary. Only single implementation devirtualization
48// is supported.
49// - Import phase: (same as with hybrid case above).
50//
51//===----------------------------------------------------------------------===//
52
53#include "llvm/Transforms/IPO/WholeProgramDevirt.h"
54#include "llvm/ADT/ArrayRef.h"
55#include "llvm/ADT/DenseMap.h"
56#include "llvm/ADT/DenseMapInfo.h"
57#include "llvm/ADT/DenseSet.h"
58#include "llvm/ADT/MapVector.h"
59#include "llvm/ADT/SmallVector.h"
60#include "llvm/ADT/iterator_range.h"
61#include "llvm/Analysis/AliasAnalysis.h"
62#include "llvm/Analysis/BasicAliasAnalysis.h"
63#include "llvm/Analysis/OptimizationRemarkEmitter.h"
64#include "llvm/Analysis/TypeMetadataUtils.h"
65#include "llvm/IR/CallSite.h"
66#include "llvm/IR/Constants.h"
67#include "llvm/IR/DataLayout.h"
68#include "llvm/IR/DebugLoc.h"
69#include "llvm/IR/DerivedTypes.h"
70#include "llvm/IR/Dominators.h"
71#include "llvm/IR/Function.h"
72#include "llvm/IR/GlobalAlias.h"
73#include "llvm/IR/GlobalVariable.h"
74#include "llvm/IR/IRBuilder.h"
75#include "llvm/IR/InstrTypes.h"
76#include "llvm/IR/Instruction.h"
77#include "llvm/IR/Instructions.h"
78#include "llvm/IR/Intrinsics.h"
79#include "llvm/IR/LLVMContext.h"
80#include "llvm/IR/Metadata.h"
81#include "llvm/IR/Module.h"
82#include "llvm/IR/ModuleSummaryIndexYAML.h"
83#include "llvm/Pass.h"
84#include "llvm/PassRegistry.h"
85#include "llvm/PassSupport.h"
86#include "llvm/Support/Casting.h"
87#include "llvm/Support/Error.h"
88#include "llvm/Support/FileSystem.h"
89#include "llvm/Support/MathExtras.h"
90#include "llvm/Transforms/IPO.h"
91#include "llvm/Transforms/IPO/FunctionAttrs.h"
92#include "llvm/Transforms/Utils/Evaluator.h"
93#include <algorithm>
94#include <cstddef>
95#include <map>
96#include <set>
97#include <string>
98
99using namespace llvm;
100using namespace wholeprogramdevirt;
101
102#define DEBUG_TYPE"wholeprogramdevirt" "wholeprogramdevirt"
103
104static cl::opt<PassSummaryAction> ClSummaryAction(
105 "wholeprogramdevirt-summary-action",
106 cl::desc("What to do with the summary when running this pass"),
107 cl::values(clEnumValN(PassSummaryAction::None, "none", "Do nothing")llvm::cl::OptionEnumValue { "none", int(PassSummaryAction::None
), "Do nothing" }
,
108 clEnumValN(PassSummaryAction::Import, "import",llvm::cl::OptionEnumValue { "import", int(PassSummaryAction::
Import), "Import typeid resolutions from summary and globals"
}
109 "Import typeid resolutions from summary and globals")llvm::cl::OptionEnumValue { "import", int(PassSummaryAction::
Import), "Import typeid resolutions from summary and globals"
}
,
110 clEnumValN(PassSummaryAction::Export, "export",llvm::cl::OptionEnumValue { "export", int(PassSummaryAction::
Export), "Export typeid resolutions to summary and globals" }
111 "Export typeid resolutions to summary and globals")llvm::cl::OptionEnumValue { "export", int(PassSummaryAction::
Export), "Export typeid resolutions to summary and globals" }
),
112 cl::Hidden);
113
114static cl::opt<std::string> ClReadSummary(
115 "wholeprogramdevirt-read-summary",
116 cl::desc("Read summary from given YAML file before running pass"),
117 cl::Hidden);
118
119static cl::opt<std::string> ClWriteSummary(
120 "wholeprogramdevirt-write-summary",
121 cl::desc("Write summary to given YAML file after running pass"),
122 cl::Hidden);
123
124static cl::opt<unsigned>
125 ClThreshold("wholeprogramdevirt-branch-funnel-threshold", cl::Hidden,
126 cl::init(10), cl::ZeroOrMore,
127 cl::desc("Maximum number of call targets per "
128 "call site to enable branch funnels"));
129
130static cl::opt<bool>
131 PrintSummaryDevirt("wholeprogramdevirt-print-index-based", cl::Hidden,
132 cl::init(false), cl::ZeroOrMore,
133 cl::desc("Print index-based devirtualization messages"));
134
135// Find the minimum offset that we may store a value of size Size bits at. If
136// IsAfter is set, look for an offset before the object, otherwise look for an
137// offset after the object.
138uint64_t
139wholeprogramdevirt::findLowestOffset(ArrayRef<VirtualCallTarget> Targets,
140 bool IsAfter, uint64_t Size) {
141 // Find a minimum offset taking into account only vtable sizes.
142 uint64_t MinByte = 0;
143 for (const VirtualCallTarget &Target : Targets) {
144 if (IsAfter)
145 MinByte = std::max(MinByte, Target.minAfterBytes());
146 else
147 MinByte = std::max(MinByte, Target.minBeforeBytes());
148 }
149
150 // Build a vector of arrays of bytes covering, for each target, a slice of the
151 // used region (see AccumBitVector::BytesUsed in
152 // llvm/Transforms/IPO/WholeProgramDevirt.h) starting at MinByte. Effectively,
153 // this aligns the used regions to start at MinByte.
154 //
155 // In this example, A, B and C are vtables, # is a byte already allocated for
156 // a virtual function pointer, AAAA... (etc.) are the used regions for the
157 // vtables and Offset(X) is the value computed for the Offset variable below
158 // for X.
159 //
160 // Offset(A)
161 // | |
162 // |MinByte
163 // A: ################AAAAAAAA|AAAAAAAA
164 // B: ########BBBBBBBBBBBBBBBB|BBBB
165 // C: ########################|CCCCCCCCCCCCCCCC
166 // | Offset(B) |
167 //
168 // This code produces the slices of A, B and C that appear after the divider
169 // at MinByte.
170 std::vector<ArrayRef<uint8_t>> Used;
171 for (const VirtualCallTarget &Target : Targets) {
172 ArrayRef<uint8_t> VTUsed = IsAfter ? Target.TM->Bits->After.BytesUsed
173 : Target.TM->Bits->Before.BytesUsed;
174 uint64_t Offset = IsAfter ? MinByte - Target.minAfterBytes()
175 : MinByte - Target.minBeforeBytes();
176
177 // Disregard used regions that are smaller than Offset. These are
178 // effectively all-free regions that do not need to be checked.
179 if (VTUsed.size() > Offset)
180 Used.push_back(VTUsed.slice(Offset));
181 }
182
183 if (Size == 1) {
184 // Find a free bit in each member of Used.
185 for (unsigned I = 0;; ++I) {
186 uint8_t BitsUsed = 0;
187 for (auto &&B : Used)
188 if (I < B.size())
189 BitsUsed |= B[I];
190 if (BitsUsed != 0xff)
191 return (MinByte + I) * 8 +
192 countTrailingZeros(uint8_t(~BitsUsed), ZB_Undefined);
193 }
194 } else {
195 // Find a free (Size/8) byte region in each member of Used.
196 // FIXME: see if alignment helps.
197 for (unsigned I = 0;; ++I) {
198 for (auto &&B : Used) {
199 unsigned Byte = 0;
200 while ((I + Byte) < B.size() && Byte < (Size / 8)) {
201 if (B[I + Byte])
202 goto NextI;
203 ++Byte;
204 }
205 }
206 return (MinByte + I) * 8;
207 NextI:;
208 }
209 }
210}
211
212void wholeprogramdevirt::setBeforeReturnValues(
213 MutableArrayRef<VirtualCallTarget> Targets, uint64_t AllocBefore,
214 unsigned BitWidth, int64_t &OffsetByte, uint64_t &OffsetBit) {
215 if (BitWidth == 1)
216 OffsetByte = -(AllocBefore / 8 + 1);
217 else
218 OffsetByte = -((AllocBefore + 7) / 8 + (BitWidth + 7) / 8);
219 OffsetBit = AllocBefore % 8;
220
221 for (VirtualCallTarget &Target : Targets) {
222 if (BitWidth == 1)
223 Target.setBeforeBit(AllocBefore);
224 else
225 Target.setBeforeBytes(AllocBefore, (BitWidth + 7) / 8);
226 }
227}
228
229void wholeprogramdevirt::setAfterReturnValues(
230 MutableArrayRef<VirtualCallTarget> Targets, uint64_t AllocAfter,
231 unsigned BitWidth, int64_t &OffsetByte, uint64_t &OffsetBit) {
232 if (BitWidth == 1)
233 OffsetByte = AllocAfter / 8;
234 else
235 OffsetByte = (AllocAfter + 7) / 8;
236 OffsetBit = AllocAfter % 8;
237
238 for (VirtualCallTarget &Target : Targets) {
239 if (BitWidth == 1)
240 Target.setAfterBit(AllocAfter);
241 else
242 Target.setAfterBytes(AllocAfter, (BitWidth + 7) / 8);
243 }
244}
245
246VirtualCallTarget::VirtualCallTarget(Function *Fn, const TypeMemberInfo *TM)
247 : Fn(Fn), TM(TM),
248 IsBigEndian(Fn->getParent()->getDataLayout().isBigEndian()), WasDevirt(false) {}
249
250namespace {
251
252// A slot in a set of virtual tables. The TypeID identifies the set of virtual
253// tables, and the ByteOffset is the offset in bytes from the address point to
254// the virtual function pointer.
255struct VTableSlot {
256 Metadata *TypeID;
257 uint64_t ByteOffset;
258};
259
260} // end anonymous namespace
261
262namespace llvm {
263
264template <> struct DenseMapInfo<VTableSlot> {
265 static VTableSlot getEmptyKey() {
266 return {DenseMapInfo<Metadata *>::getEmptyKey(),
267 DenseMapInfo<uint64_t>::getEmptyKey()};
268 }
269 static VTableSlot getTombstoneKey() {
270 return {DenseMapInfo<Metadata *>::getTombstoneKey(),
271 DenseMapInfo<uint64_t>::getTombstoneKey()};
272 }
273 static unsigned getHashValue(const VTableSlot &I) {
274 return DenseMapInfo<Metadata *>::getHashValue(I.TypeID) ^
275 DenseMapInfo<uint64_t>::getHashValue(I.ByteOffset);
276 }
277 static bool isEqual(const VTableSlot &LHS,
278 const VTableSlot &RHS) {
279 return LHS.TypeID == RHS.TypeID && LHS.ByteOffset == RHS.ByteOffset;
280 }
281};
282
283template <> struct DenseMapInfo<VTableSlotSummary> {
284 static VTableSlotSummary getEmptyKey() {
285 return {DenseMapInfo<StringRef>::getEmptyKey(),
286 DenseMapInfo<uint64_t>::getEmptyKey()};
287 }
288 static VTableSlotSummary getTombstoneKey() {
289 return {DenseMapInfo<StringRef>::getTombstoneKey(),
290 DenseMapInfo<uint64_t>::getTombstoneKey()};
291 }
292 static unsigned getHashValue(const VTableSlotSummary &I) {
293 return DenseMapInfo<StringRef>::getHashValue(I.TypeID) ^
294 DenseMapInfo<uint64_t>::getHashValue(I.ByteOffset);
295 }
296 static bool isEqual(const VTableSlotSummary &LHS,
297 const VTableSlotSummary &RHS) {
298 return LHS.TypeID == RHS.TypeID && LHS.ByteOffset == RHS.ByteOffset;
299 }
300};
301
302} // end namespace llvm
303
304namespace {
305
306// A virtual call site. VTable is the loaded virtual table pointer, and CS is
307// the indirect virtual call.
308struct VirtualCallSite {
309 Value *VTable;
310 CallSite CS;
311
312 // If non-null, this field points to the associated unsafe use count stored in
313 // the DevirtModule::NumUnsafeUsesForTypeTest map below. See the description
314 // of that field for details.
315 unsigned *NumUnsafeUses;
316
317 void
318 emitRemark(const StringRef OptName, const StringRef TargetName,
319 function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter) {
320 Function *F = CS.getCaller();
321 DebugLoc DLoc = CS->getDebugLoc();
322 BasicBlock *Block = CS.getParent();
323
324 using namespace ore;
325 OREGetter(F).emit(OptimizationRemark(DEBUG_TYPE"wholeprogramdevirt", OptName, DLoc, Block)
326 << NV("Optimization", OptName)
327 << ": devirtualized a call to "
328 << NV("FunctionName", TargetName));
329 }
330
331 void replaceAndErase(
332 const StringRef OptName, const StringRef TargetName, bool RemarksEnabled,
333 function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter,
334 Value *New) {
335 if (RemarksEnabled)
336 emitRemark(OptName, TargetName, OREGetter);
337 CS->replaceAllUsesWith(New);
338 if (auto II = dyn_cast<InvokeInst>(CS.getInstruction())) {
339 BranchInst::Create(II->getNormalDest(), CS.getInstruction());
340 II->getUnwindDest()->removePredecessor(II->getParent());
341 }
342 CS->eraseFromParent();
343 // This use is no longer unsafe.
344 if (NumUnsafeUses)
345 --*NumUnsafeUses;
346 }
347};
348
349// Call site information collected for a specific VTableSlot and possibly a list
350// of constant integer arguments. The grouping by arguments is handled by the
351// VTableSlotInfo class.
352struct CallSiteInfo {
353 /// The set of call sites for this slot. Used during regular LTO and the
354 /// import phase of ThinLTO (as well as the export phase of ThinLTO for any
355 /// call sites that appear in the merged module itself); in each of these
356 /// cases we are directly operating on the call sites at the IR level.
357 std::vector<VirtualCallSite> CallSites;
358
359 /// Whether all call sites represented by this CallSiteInfo, including those
360 /// in summaries, have been devirtualized. This starts off as true because a
361 /// default constructed CallSiteInfo represents no call sites.
362 bool AllCallSitesDevirted = true;
363
364 // These fields are used during the export phase of ThinLTO and reflect
365 // information collected from function summaries.
366
367 /// Whether any function summary contains an llvm.assume(llvm.type.test) for
368 /// this slot.
369 bool SummaryHasTypeTestAssumeUsers = false;
370
371 /// CFI-specific: a vector containing the list of function summaries that use
372 /// the llvm.type.checked.load intrinsic and therefore will require
373 /// resolutions for llvm.type.test in order to implement CFI checks if
374 /// devirtualization was unsuccessful. If devirtualization was successful, the
375 /// pass will clear this vector by calling markDevirt(). If at the end of the
376 /// pass the vector is non-empty, we will need to add a use of llvm.type.test
377 /// to each of the function summaries in the vector.
378 std::vector<FunctionSummary *> SummaryTypeCheckedLoadUsers;
379 std::vector<FunctionSummary *> SummaryTypeTestAssumeUsers;
380
381 bool isExported() const {
382 return SummaryHasTypeTestAssumeUsers ||
32
Assuming field 'SummaryHasTypeTestAssumeUsers' is true
33
Returning the value 1, which participates in a condition later
383 !SummaryTypeCheckedLoadUsers.empty();
384 }
385
386 void addSummaryTypeCheckedLoadUser(FunctionSummary *FS) {
387 SummaryTypeCheckedLoadUsers.push_back(FS);
388 AllCallSitesDevirted = false;
389 }
390
391 void addSummaryTypeTestAssumeUser(FunctionSummary *FS) {
392 SummaryTypeTestAssumeUsers.push_back(FS);
393 SummaryHasTypeTestAssumeUsers = true;
394 AllCallSitesDevirted = false;
395 }
396
397 void markDevirt() {
398 AllCallSitesDevirted = true;
399
400 // As explained in the comment for SummaryTypeCheckedLoadUsers.
401 SummaryTypeCheckedLoadUsers.clear();
402 }
403};
404
405// Call site information collected for a specific VTableSlot.
406struct VTableSlotInfo {
407 // The set of call sites which do not have all constant integer arguments
408 // (excluding "this").
409 CallSiteInfo CSInfo;
410
411 // The set of call sites with all constant integer arguments (excluding
412 // "this"), grouped by argument list.
413 std::map<std::vector<uint64_t>, CallSiteInfo> ConstCSInfo;
414
415 void addCallSite(Value *VTable, CallSite CS, unsigned *NumUnsafeUses);
416
417private:
418 CallSiteInfo &findCallSiteInfo(CallSite CS);
419};
420
421CallSiteInfo &VTableSlotInfo::findCallSiteInfo(CallSite CS) {
422 std::vector<uint64_t> Args;
423 auto *CI = dyn_cast<IntegerType>(CS.getType());
424 if (!CI || CI->getBitWidth() > 64 || CS.arg_empty())
425 return CSInfo;
426 for (auto &&Arg : make_range(CS.arg_begin() + 1, CS.arg_end())) {
427 auto *CI = dyn_cast<ConstantInt>(Arg);
428 if (!CI || CI->getBitWidth() > 64)
429 return CSInfo;
430 Args.push_back(CI->getZExtValue());
431 }
432 return ConstCSInfo[Args];
433}
434
435void VTableSlotInfo::addCallSite(Value *VTable, CallSite CS,
436 unsigned *NumUnsafeUses) {
437 auto &CSI = findCallSiteInfo(CS);
438 CSI.AllCallSitesDevirted = false;
439 CSI.CallSites.push_back({VTable, CS, NumUnsafeUses});
440}
441
442struct DevirtModule {
443 Module &M;
444 function_ref<AAResults &(Function &)> AARGetter;
445 function_ref<DominatorTree &(Function &)> LookupDomTree;
446
447 ModuleSummaryIndex *ExportSummary;
448 const ModuleSummaryIndex *ImportSummary;
449
450 IntegerType *Int8Ty;
451 PointerType *Int8PtrTy;
452 IntegerType *Int32Ty;
453 IntegerType *Int64Ty;
454 IntegerType *IntPtrTy;
455
456 bool RemarksEnabled;
457 function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter;
458
459 MapVector<VTableSlot, VTableSlotInfo> CallSlots;
460
461 // This map keeps track of the number of "unsafe" uses of a loaded function
462 // pointer. The key is the associated llvm.type.test intrinsic call generated
463 // by this pass. An unsafe use is one that calls the loaded function pointer
464 // directly. Every time we eliminate an unsafe use (for example, by
465 // devirtualizing it or by applying virtual constant propagation), we
466 // decrement the value stored in this map. If a value reaches zero, we can
467 // eliminate the type check by RAUWing the associated llvm.type.test call with
468 // true.
469 std::map<CallInst *, unsigned> NumUnsafeUsesForTypeTest;
470
471 DevirtModule(Module &M, function_ref<AAResults &(Function &)> AARGetter,
472 function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter,
473 function_ref<DominatorTree &(Function &)> LookupDomTree,
474 ModuleSummaryIndex *ExportSummary,
475 const ModuleSummaryIndex *ImportSummary)
476 : M(M), AARGetter(AARGetter), LookupDomTree(LookupDomTree),
477 ExportSummary(ExportSummary), ImportSummary(ImportSummary),
478 Int8Ty(Type::getInt8Ty(M.getContext())),
479 Int8PtrTy(Type::getInt8PtrTy(M.getContext())),
480 Int32Ty(Type::getInt32Ty(M.getContext())),
481 Int64Ty(Type::getInt64Ty(M.getContext())),
482 IntPtrTy(M.getDataLayout().getIntPtrType(M.getContext(), 0)),
483 RemarksEnabled(areRemarksEnabled()), OREGetter(OREGetter) {
484 assert(!(ExportSummary && ImportSummary))((!(ExportSummary && ImportSummary)) ? static_cast<
void> (0) : __assert_fail ("!(ExportSummary && ImportSummary)"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 484, __PRETTY_FUNCTION__))
;
485 }
486
487 bool areRemarksEnabled();
488
489 void scanTypeTestUsers(Function *TypeTestFunc, Function *AssumeFunc);
490 void scanTypeCheckedLoadUsers(Function *TypeCheckedLoadFunc);
491
492 void buildTypeIdentifierMap(
493 std::vector<VTableBits> &Bits,
494 DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap);
495 bool
496 tryFindVirtualCallTargets(std::vector<VirtualCallTarget> &TargetsForSlot,
497 const std::set<TypeMemberInfo> &TypeMemberInfos,
498 uint64_t ByteOffset);
499
500 void applySingleImplDevirt(VTableSlotInfo &SlotInfo, Constant *TheFn,
501 bool &IsExported);
502 bool trySingleImplDevirt(ModuleSummaryIndex *ExportSummary,
503 MutableArrayRef<VirtualCallTarget> TargetsForSlot,
504 VTableSlotInfo &SlotInfo,
505 WholeProgramDevirtResolution *Res);
506
507 void applyICallBranchFunnel(VTableSlotInfo &SlotInfo, Constant *JT,
508 bool &IsExported);
509 void tryICallBranchFunnel(MutableArrayRef<VirtualCallTarget> TargetsForSlot,
510 VTableSlotInfo &SlotInfo,
511 WholeProgramDevirtResolution *Res, VTableSlot Slot);
512
513 bool tryEvaluateFunctionsWithArgs(
514 MutableArrayRef<VirtualCallTarget> TargetsForSlot,
515 ArrayRef<uint64_t> Args);
516
517 void applyUniformRetValOpt(CallSiteInfo &CSInfo, StringRef FnName,
518 uint64_t TheRetVal);
519 bool tryUniformRetValOpt(MutableArrayRef<VirtualCallTarget> TargetsForSlot,
520 CallSiteInfo &CSInfo,
521 WholeProgramDevirtResolution::ByArg *Res);
522
523 // Returns the global symbol name that is used to export information about the
524 // given vtable slot and list of arguments.
525 std::string getGlobalName(VTableSlot Slot, ArrayRef<uint64_t> Args,
526 StringRef Name);
527
528 bool shouldExportConstantsAsAbsoluteSymbols();
529
530 // This function is called during the export phase to create a symbol
531 // definition containing information about the given vtable slot and list of
532 // arguments.
533 void exportGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args, StringRef Name,
534 Constant *C);
535 void exportConstant(VTableSlot Slot, ArrayRef<uint64_t> Args, StringRef Name,
536 uint32_t Const, uint32_t &Storage);
537
538 // This function is called during the import phase to create a reference to
539 // the symbol definition created during the export phase.
540 Constant *importGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args,
541 StringRef Name);
542 Constant *importConstant(VTableSlot Slot, ArrayRef<uint64_t> Args,
543 StringRef Name, IntegerType *IntTy,
544 uint32_t Storage);
545
546 Constant *getMemberAddr(const TypeMemberInfo *M);
547
548 void applyUniqueRetValOpt(CallSiteInfo &CSInfo, StringRef FnName, bool IsOne,
549 Constant *UniqueMemberAddr);
550 bool tryUniqueRetValOpt(unsigned BitWidth,
551 MutableArrayRef<VirtualCallTarget> TargetsForSlot,
552 CallSiteInfo &CSInfo,
553 WholeProgramDevirtResolution::ByArg *Res,
554 VTableSlot Slot, ArrayRef<uint64_t> Args);
555
556 void applyVirtualConstProp(CallSiteInfo &CSInfo, StringRef FnName,
557 Constant *Byte, Constant *Bit);
558 bool tryVirtualConstProp(MutableArrayRef<VirtualCallTarget> TargetsForSlot,
559 VTableSlotInfo &SlotInfo,
560 WholeProgramDevirtResolution *Res, VTableSlot Slot);
561
562 void rebuildGlobal(VTableBits &B);
563
564 // Apply the summary resolution for Slot to all virtual calls in SlotInfo.
565 void importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo);
566
567 // If we were able to eliminate all unsafe uses for a type checked load,
568 // eliminate the associated type tests by replacing them with true.
569 void removeRedundantTypeTests();
570
571 bool run();
572
573 // Lower the module using the action and summary passed as command line
574 // arguments. For testing purposes only.
575 static bool
576 runForTesting(Module &M, function_ref<AAResults &(Function &)> AARGetter,
577 function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter,
578 function_ref<DominatorTree &(Function &)> LookupDomTree);
579};
580
581struct DevirtIndex {
582 ModuleSummaryIndex &ExportSummary;
583 // The set in which to record GUIDs exported from their module by
584 // devirtualization, used by client to ensure they are not internalized.
585 std::set<GlobalValue::GUID> &ExportedGUIDs;
586 // A map in which to record the information necessary to locate the WPD
587 // resolution for local targets in case they are exported by cross module
588 // importing.
589 std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap;
590
591 MapVector<VTableSlotSummary, VTableSlotInfo> CallSlots;
592
593 DevirtIndex(
594 ModuleSummaryIndex &ExportSummary,
595 std::set<GlobalValue::GUID> &ExportedGUIDs,
596 std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap)
597 : ExportSummary(ExportSummary), ExportedGUIDs(ExportedGUIDs),
598 LocalWPDTargetsMap(LocalWPDTargetsMap) {}
599
600 bool tryFindVirtualCallTargets(std::vector<ValueInfo> &TargetsForSlot,
601 const TypeIdCompatibleVtableInfo TIdInfo,
602 uint64_t ByteOffset);
603
604 bool trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot,
605 VTableSlotSummary &SlotSummary,
606 VTableSlotInfo &SlotInfo,
607 WholeProgramDevirtResolution *Res,
608 std::set<ValueInfo> &DevirtTargets);
609
610 void run();
611};
612
613struct WholeProgramDevirt : public ModulePass {
614 static char ID;
615
616 bool UseCommandLine = false;
617
618 ModuleSummaryIndex *ExportSummary;
619 const ModuleSummaryIndex *ImportSummary;
620
621 WholeProgramDevirt() : ModulePass(ID), UseCommandLine(true) {
622 initializeWholeProgramDevirtPass(*PassRegistry::getPassRegistry());
623 }
624
625 WholeProgramDevirt(ModuleSummaryIndex *ExportSummary,
626 const ModuleSummaryIndex *ImportSummary)
627 : ModulePass(ID), ExportSummary(ExportSummary),
628 ImportSummary(ImportSummary) {
629 initializeWholeProgramDevirtPass(*PassRegistry::getPassRegistry());
630 }
631
632 bool runOnModule(Module &M) override {
633 if (skipModule(M))
634 return false;
635
636 // In the new pass manager, we can request the optimization
637 // remark emitter pass on a per-function-basis, which the
638 // OREGetter will do for us.
639 // In the old pass manager, this is harder, so we just build
640 // an optimization remark emitter on the fly, when we need it.
641 std::unique_ptr<OptimizationRemarkEmitter> ORE;
642 auto OREGetter = [&](Function *F) -> OptimizationRemarkEmitter & {
643 ORE = std::make_unique<OptimizationRemarkEmitter>(F);
644 return *ORE;
645 };
646
647 auto LookupDomTree = [this](Function &F) -> DominatorTree & {
648 return this->getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
649 };
650
651 if (UseCommandLine)
652 return DevirtModule::runForTesting(M, LegacyAARGetter(*this), OREGetter,
653 LookupDomTree);
654
655 return DevirtModule(M, LegacyAARGetter(*this), OREGetter, LookupDomTree,
656 ExportSummary, ImportSummary)
657 .run();
658 }
659
660 void getAnalysisUsage(AnalysisUsage &AU) const override {
661 AU.addRequired<AssumptionCacheTracker>();
662 AU.addRequired<TargetLibraryInfoWrapperPass>();
663 AU.addRequired<DominatorTreeWrapperPass>();
664 }
665};
666
667} // end anonymous namespace
668
669INITIALIZE_PASS_BEGIN(WholeProgramDevirt, "wholeprogramdevirt",static void *initializeWholeProgramDevirtPassOnce(PassRegistry
&Registry) {
670 "Whole program devirtualization", false, false)static void *initializeWholeProgramDevirtPassOnce(PassRegistry
&Registry) {
671INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry);
672INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry);
673INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
674INITIALIZE_PASS_END(WholeProgramDevirt, "wholeprogramdevirt",PassInfo *PI = new PassInfo( "Whole program devirtualization"
, "wholeprogramdevirt", &WholeProgramDevirt::ID, PassInfo
::NormalCtor_t(callDefaultCtor<WholeProgramDevirt>), false
, false); Registry.registerPass(*PI, true); return PI; } static
llvm::once_flag InitializeWholeProgramDevirtPassFlag; void llvm
::initializeWholeProgramDevirtPass(PassRegistry &Registry
) { llvm::call_once(InitializeWholeProgramDevirtPassFlag, initializeWholeProgramDevirtPassOnce
, std::ref(Registry)); }
675 "Whole program devirtualization", false, false)PassInfo *PI = new PassInfo( "Whole program devirtualization"
, "wholeprogramdevirt", &WholeProgramDevirt::ID, PassInfo
::NormalCtor_t(callDefaultCtor<WholeProgramDevirt>), false
, false); Registry.registerPass(*PI, true); return PI; } static
llvm::once_flag InitializeWholeProgramDevirtPassFlag; void llvm
::initializeWholeProgramDevirtPass(PassRegistry &Registry
) { llvm::call_once(InitializeWholeProgramDevirtPassFlag, initializeWholeProgramDevirtPassOnce
, std::ref(Registry)); }
676char WholeProgramDevirt::ID = 0;
677
678ModulePass *
679llvm::createWholeProgramDevirtPass(ModuleSummaryIndex *ExportSummary,
680 const ModuleSummaryIndex *ImportSummary) {
681 return new WholeProgramDevirt(ExportSummary, ImportSummary);
682}
683
684PreservedAnalyses WholeProgramDevirtPass::run(Module &M,
685 ModuleAnalysisManager &AM) {
686 auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
687 auto AARGetter = [&](Function &F) -> AAResults & {
688 return FAM.getResult<AAManager>(F);
689 };
690 auto OREGetter = [&](Function *F) -> OptimizationRemarkEmitter & {
691 return FAM.getResult<OptimizationRemarkEmitterAnalysis>(*F);
692 };
693 auto LookupDomTree = [&FAM](Function &F) -> DominatorTree & {
694 return FAM.getResult<DominatorTreeAnalysis>(F);
695 };
696 if (!DevirtModule(M, AARGetter, OREGetter, LookupDomTree, ExportSummary,
697 ImportSummary)
698 .run())
699 return PreservedAnalyses::all();
700 return PreservedAnalyses::none();
701}
702
703namespace llvm {
704void runWholeProgramDevirtOnIndex(
705 ModuleSummaryIndex &Summary, std::set<GlobalValue::GUID> &ExportedGUIDs,
706 std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap) {
707 DevirtIndex(Summary, ExportedGUIDs, LocalWPDTargetsMap).run();
708}
709
710void updateIndexWPDForExports(
711 ModuleSummaryIndex &Summary,
712 function_ref<bool(StringRef, GlobalValue::GUID)> isExported,
713 std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap) {
714 for (auto &T : LocalWPDTargetsMap) {
715 auto &VI = T.first;
716 // This was enforced earlier during trySingleImplDevirt.
717 assert(VI.getSummaryList().size() == 1 &&((VI.getSummaryList().size() == 1 && "Devirt of local target has more than one copy"
) ? static_cast<void> (0) : __assert_fail ("VI.getSummaryList().size() == 1 && \"Devirt of local target has more than one copy\""
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 718, __PRETTY_FUNCTION__))
718 "Devirt of local target has more than one copy")((VI.getSummaryList().size() == 1 && "Devirt of local target has more than one copy"
) ? static_cast<void> (0) : __assert_fail ("VI.getSummaryList().size() == 1 && \"Devirt of local target has more than one copy\""
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 718, __PRETTY_FUNCTION__))
;
719 auto &S = VI.getSummaryList()[0];
720 if (!isExported(S->modulePath(), VI.getGUID()))
721 continue;
722
723 // It's been exported by a cross module import.
724 for (auto &SlotSummary : T.second) {
725 auto *TIdSum = Summary.getTypeIdSummary(SlotSummary.TypeID);
726 assert(TIdSum)((TIdSum) ? static_cast<void> (0) : __assert_fail ("TIdSum"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 726, __PRETTY_FUNCTION__))
;
727 auto WPDRes = TIdSum->WPDRes.find(SlotSummary.ByteOffset);
728 assert(WPDRes != TIdSum->WPDRes.end())((WPDRes != TIdSum->WPDRes.end()) ? static_cast<void>
(0) : __assert_fail ("WPDRes != TIdSum->WPDRes.end()", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 728, __PRETTY_FUNCTION__))
;
729 WPDRes->second.SingleImplName = ModuleSummaryIndex::getGlobalNameForLocal(
730 WPDRes->second.SingleImplName,
731 Summary.getModuleHash(S->modulePath()));
732 }
733 }
734}
735
736} // end namespace llvm
737
738bool DevirtModule::runForTesting(
739 Module &M, function_ref<AAResults &(Function &)> AARGetter,
740 function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter,
741 function_ref<DominatorTree &(Function &)> LookupDomTree) {
742 ModuleSummaryIndex Summary(/*HaveGVs=*/false);
743
744 // Handle the command-line summary arguments. This code is for testing
745 // purposes only, so we handle errors directly.
746 if (!ClReadSummary.empty()) {
747 ExitOnError ExitOnErr("-wholeprogramdevirt-read-summary: " + ClReadSummary +
748 ": ");
749 auto ReadSummaryFile =
750 ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary)));
751
752 yaml::Input In(ReadSummaryFile->getBuffer());
753 In >> Summary;
754 ExitOnErr(errorCodeToError(In.error()));
755 }
756
757 bool Changed =
758 DevirtModule(
759 M, AARGetter, OREGetter, LookupDomTree,
760 ClSummaryAction == PassSummaryAction::Export ? &Summary : nullptr,
761 ClSummaryAction == PassSummaryAction::Import ? &Summary : nullptr)
762 .run();
763
764 if (!ClWriteSummary.empty()) {
765 ExitOnError ExitOnErr(
766 "-wholeprogramdevirt-write-summary: " + ClWriteSummary + ": ");
767 std::error_code EC;
768 raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::OF_Text);
769 ExitOnErr(errorCodeToError(EC));
770
771 yaml::Output Out(OS);
772 Out << Summary;
773 }
774
775 return Changed;
776}
777
778void DevirtModule::buildTypeIdentifierMap(
779 std::vector<VTableBits> &Bits,
780 DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap) {
781 DenseMap<GlobalVariable *, VTableBits *> GVToBits;
782 Bits.reserve(M.getGlobalList().size());
783 SmallVector<MDNode *, 2> Types;
784 for (GlobalVariable &GV : M.globals()) {
785 Types.clear();
786 GV.getMetadata(LLVMContext::MD_type, Types);
787 if (GV.isDeclaration() || Types.empty())
788 continue;
789
790 VTableBits *&BitsPtr = GVToBits[&GV];
791 if (!BitsPtr) {
792 Bits.emplace_back();
793 Bits.back().GV = &GV;
794 Bits.back().ObjectSize =
795 M.getDataLayout().getTypeAllocSize(GV.getInitializer()->getType());
796 BitsPtr = &Bits.back();
797 }
798
799 for (MDNode *Type : Types) {
800 auto TypeID = Type->getOperand(1).get();
801
802 uint64_t Offset =
803 cast<ConstantInt>(
804 cast<ConstantAsMetadata>(Type->getOperand(0))->getValue())
805 ->getZExtValue();
806
807 TypeIdMap[TypeID].insert({BitsPtr, Offset});
808 }
809 }
810}
811
812bool DevirtModule::tryFindVirtualCallTargets(
813 std::vector<VirtualCallTarget> &TargetsForSlot,
814 const std::set<TypeMemberInfo> &TypeMemberInfos, uint64_t ByteOffset) {
815 for (const TypeMemberInfo &TM : TypeMemberInfos) {
816 if (!TM.Bits->GV->isConstant())
817 return false;
818
819 Constant *Ptr = getPointerAtOffset(TM.Bits->GV->getInitializer(),
820 TM.Offset + ByteOffset, M);
821 if (!Ptr)
822 return false;
823
824 auto Fn = dyn_cast<Function>(Ptr->stripPointerCasts());
825 if (!Fn)
826 return false;
827
828 // We can disregard __cxa_pure_virtual as a possible call target, as
829 // calls to pure virtuals are UB.
830 if (Fn->getName() == "__cxa_pure_virtual")
831 continue;
832
833 TargetsForSlot.push_back({Fn, &TM});
834 }
835
836 // Give up if we couldn't find any targets.
837 return !TargetsForSlot.empty();
838}
839
840bool DevirtIndex::tryFindVirtualCallTargets(
841 std::vector<ValueInfo> &TargetsForSlot, const TypeIdCompatibleVtableInfo TIdInfo,
842 uint64_t ByteOffset) {
843 for (const TypeIdOffsetVtableInfo P : TIdInfo) {
844 // Ensure that we have at most one external linkage vtable initializer.
845 assert(P.VTableVI.getSummaryList().size() == 1 ||((P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P
.VTableVI.getSummaryList(), [&](const std::unique_ptr<
GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage
(Summary->linkage()); }) <= 1) ? static_cast<void>
(0) : __assert_fail ("P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P.VTableVI.getSummaryList(), [&](const std::unique_ptr<GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage(Summary->linkage()); }) <= 1"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 850, __PRETTY_FUNCTION__))
846 llvm::count_if(((P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P
.VTableVI.getSummaryList(), [&](const std::unique_ptr<
GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage
(Summary->linkage()); }) <= 1) ? static_cast<void>
(0) : __assert_fail ("P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P.VTableVI.getSummaryList(), [&](const std::unique_ptr<GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage(Summary->linkage()); }) <= 1"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 850, __PRETTY_FUNCTION__))
847 P.VTableVI.getSummaryList(),((P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P
.VTableVI.getSummaryList(), [&](const std::unique_ptr<
GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage
(Summary->linkage()); }) <= 1) ? static_cast<void>
(0) : __assert_fail ("P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P.VTableVI.getSummaryList(), [&](const std::unique_ptr<GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage(Summary->linkage()); }) <= 1"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 850, __PRETTY_FUNCTION__))
848 [&](const std::unique_ptr<GlobalValueSummary> &Summary) {((P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P
.VTableVI.getSummaryList(), [&](const std::unique_ptr<
GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage
(Summary->linkage()); }) <= 1) ? static_cast<void>
(0) : __assert_fail ("P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P.VTableVI.getSummaryList(), [&](const std::unique_ptr<GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage(Summary->linkage()); }) <= 1"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 850, __PRETTY_FUNCTION__))
849 return GlobalValue::isExternalLinkage(Summary->linkage());((P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P
.VTableVI.getSummaryList(), [&](const std::unique_ptr<
GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage
(Summary->linkage()); }) <= 1) ? static_cast<void>
(0) : __assert_fail ("P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P.VTableVI.getSummaryList(), [&](const std::unique_ptr<GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage(Summary->linkage()); }) <= 1"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 850, __PRETTY_FUNCTION__))
850 }) <= 1)((P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P
.VTableVI.getSummaryList(), [&](const std::unique_ptr<
GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage
(Summary->linkage()); }) <= 1) ? static_cast<void>
(0) : __assert_fail ("P.VTableVI.getSummaryList().size() == 1 || llvm::count_if( P.VTableVI.getSummaryList(), [&](const std::unique_ptr<GlobalValueSummary> &Summary) { return GlobalValue::isExternalLinkage(Summary->linkage()); }) <= 1"
, "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 850, __PRETTY_FUNCTION__))
;
851 // Find the first non-available_externally linkage vtable initializer.
852 // We can have multiple available_externally, linkonce_odr and weak_odr
853 // vtable initializers, however we want to skip available_externally as they
854 // do not have type metadata attached, and therefore the summary will not
855 // contain any vtable functions.
856 //
857 // Also, handle the case of same-named local Vtables with the same path
858 // and therefore the same GUID. This can happen if there isn't enough
859 // distinguishing path when compiling the source file. In that case we
860 // conservatively return false early.
861 const GlobalVarSummary *VS = nullptr;
862 bool LocalFound = false;
863 for (auto &S : P.VTableVI.getSummaryList()) {
864 if (GlobalValue::isLocalLinkage(S->linkage())) {
865 if (LocalFound)
866 return false;
867 LocalFound = true;
868 }
869 if (!GlobalValue::isAvailableExternallyLinkage(S->linkage()))
870 VS = cast<GlobalVarSummary>(S.get());
871 }
872 if (!VS->isLive())
873 continue;
874 for (auto VTP : VS->vTableFuncs()) {
875 if (VTP.VTableOffset != P.AddressPointOffset + ByteOffset)
876 continue;
877
878 TargetsForSlot.push_back(VTP.FuncVI);
879 }
880 }
881
882 // Give up if we couldn't find any targets.
883 return !TargetsForSlot.empty();
884}
885
886void DevirtModule::applySingleImplDevirt(VTableSlotInfo &SlotInfo,
887 Constant *TheFn, bool &IsExported) {
888 auto Apply = [&](CallSiteInfo &CSInfo) {
889 for (auto &&VCallSite : CSInfo.CallSites) {
890 if (RemarksEnabled)
891 VCallSite.emitRemark("single-impl",
892 TheFn->stripPointerCasts()->getName(), OREGetter);
893 VCallSite.CS.setCalledFunction(ConstantExpr::getBitCast(
894 TheFn, VCallSite.CS.getCalledValue()->getType()));
895 // This use is no longer unsafe.
896 if (VCallSite.NumUnsafeUses)
897 --*VCallSite.NumUnsafeUses;
898 }
899 if (CSInfo.isExported())
900 IsExported = true;
901 CSInfo.markDevirt();
902 };
903 Apply(SlotInfo.CSInfo);
904 for (auto &P : SlotInfo.ConstCSInfo)
905 Apply(P.second);
906}
907
908static bool AddCalls(VTableSlotInfo &SlotInfo, const ValueInfo &Callee) {
909 // We can't add calls if we haven't seen a definition
910 if (Callee.getSummaryList().empty())
911 return false;
912
913 // Insert calls into the summary index so that the devirtualized targets
914 // are eligible for import.
915 // FIXME: Annotate type tests with hotness. For now, mark these as hot
916 // to better ensure we have the opportunity to inline them.
917 bool IsExported = false;
918 auto &S = Callee.getSummaryList()[0];
919 CalleeInfo CI(CalleeInfo::HotnessType::Hot, /* RelBF = */ 0);
920 auto AddCalls = [&](CallSiteInfo &CSInfo) {
921 for (auto *FS : CSInfo.SummaryTypeCheckedLoadUsers) {
922 FS->addCall({Callee, CI});
923 IsExported |= S->modulePath() != FS->modulePath();
924 }
925 for (auto *FS : CSInfo.SummaryTypeTestAssumeUsers) {
926 FS->addCall({Callee, CI});
927 IsExported |= S->modulePath() != FS->modulePath();
928 }
929 };
930 AddCalls(SlotInfo.CSInfo);
931 for (auto &P : SlotInfo.ConstCSInfo)
932 AddCalls(P.second);
933 return IsExported;
934}
935
936bool DevirtModule::trySingleImplDevirt(
937 ModuleSummaryIndex *ExportSummary,
938 MutableArrayRef<VirtualCallTarget> TargetsForSlot, VTableSlotInfo &SlotInfo,
939 WholeProgramDevirtResolution *Res) {
940 // See if the program contains a single implementation of this virtual
941 // function.
942 Function *TheFn = TargetsForSlot[0].Fn;
943 for (auto &&Target : TargetsForSlot)
944 if (TheFn != Target.Fn)
945 return false;
946
947 // If so, update each call site to call that implementation directly.
948 if (RemarksEnabled)
949 TargetsForSlot[0].WasDevirt = true;
950
951 bool IsExported = false;
952 applySingleImplDevirt(SlotInfo, TheFn, IsExported);
953 if (!IsExported)
954 return false;
955
956 // If the only implementation has local linkage, we must promote to external
957 // to make it visible to thin LTO objects. We can only get here during the
958 // ThinLTO export phase.
959 if (TheFn->hasLocalLinkage()) {
960 std::string NewName = (TheFn->getName() + "$merged").str();
961
962 // Since we are renaming the function, any comdats with the same name must
963 // also be renamed. This is required when targeting COFF, as the comdat name
964 // must match one of the names of the symbols in the comdat.
965 if (Comdat *C = TheFn->getComdat()) {
966 if (C->getName() == TheFn->getName()) {
967 Comdat *NewC = M.getOrInsertComdat(NewName);
968 NewC->setSelectionKind(C->getSelectionKind());
969 for (GlobalObject &GO : M.global_objects())
970 if (GO.getComdat() == C)
971 GO.setComdat(NewC);
972 }
973 }
974
975 TheFn->setLinkage(GlobalValue::ExternalLinkage);
976 TheFn->setVisibility(GlobalValue::HiddenVisibility);
977 TheFn->setName(NewName);
978 }
979 if (ValueInfo TheFnVI = ExportSummary->getValueInfo(TheFn->getGUID()))
980 // Any needed promotion of 'TheFn' has already been done during
981 // LTO unit split, so we can ignore return value of AddCalls.
982 AddCalls(SlotInfo, TheFnVI);
983
984 Res->TheKind = WholeProgramDevirtResolution::SingleImpl;
985 Res->SingleImplName = TheFn->getName();
986
987 return true;
988}
989
990bool DevirtIndex::trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot,
991 VTableSlotSummary &SlotSummary,
992 VTableSlotInfo &SlotInfo,
993 WholeProgramDevirtResolution *Res,
994 std::set<ValueInfo> &DevirtTargets) {
995 // See if the program contains a single implementation of this virtual
996 // function.
997 auto TheFn = TargetsForSlot[0];
998 for (auto &&Target : TargetsForSlot)
999 if (TheFn != Target)
1000 return false;
1001
1002 // Don't devirtualize if we don't have target definition.
1003 auto Size = TheFn.getSummaryList().size();
1004 if (!Size)
1005 return false;
1006
1007 // If the summary list contains multiple summaries where at least one is
1008 // a local, give up, as we won't know which (possibly promoted) name to use.
1009 for (auto &S : TheFn.getSummaryList())
1010 if (GlobalValue::isLocalLinkage(S->linkage()) && Size > 1)
1011 return false;
1012
1013 // Collect functions devirtualized at least for one call site for stats.
1014 if (PrintSummaryDevirt)
1015 DevirtTargets.insert(TheFn);
1016
1017 auto &S = TheFn.getSummaryList()[0];
1018 bool IsExported = AddCalls(SlotInfo, TheFn);
1019 if (IsExported)
1020 ExportedGUIDs.insert(TheFn.getGUID());
1021
1022 // Record in summary for use in devirtualization during the ThinLTO import
1023 // step.
1024 Res->TheKind = WholeProgramDevirtResolution::SingleImpl;
1025 if (GlobalValue::isLocalLinkage(S->linkage())) {
1026 if (IsExported)
1027 // If target is a local function and we are exporting it by
1028 // devirtualizing a call in another module, we need to record the
1029 // promoted name.
1030 Res->SingleImplName = ModuleSummaryIndex::getGlobalNameForLocal(
1031 TheFn.name(), ExportSummary.getModuleHash(S->modulePath()));
1032 else {
1033 LocalWPDTargetsMap[TheFn].push_back(SlotSummary);
1034 Res->SingleImplName = TheFn.name();
1035 }
1036 } else
1037 Res->SingleImplName = TheFn.name();
1038
1039 // Name will be empty if this thin link driven off of serialized combined
1040 // index (e.g. llvm-lto). However, WPD is not supported/invoked for the
1041 // legacy LTO API anyway.
1042 assert(!Res->SingleImplName.empty())((!Res->SingleImplName.empty()) ? static_cast<void> (
0) : __assert_fail ("!Res->SingleImplName.empty()", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 1042, __PRETTY_FUNCTION__))
;
1043
1044 return true;
1045}
1046
1047void DevirtModule::tryICallBranchFunnel(
1048 MutableArrayRef<VirtualCallTarget> TargetsForSlot, VTableSlotInfo &SlotInfo,
1049 WholeProgramDevirtResolution *Res, VTableSlot Slot) {
1050 Triple T(M.getTargetTriple());
1051 if (T.getArch() != Triple::x86_64)
1052 return;
1053
1054 if (TargetsForSlot.size() > ClThreshold)
1055 return;
1056
1057 bool HasNonDevirt = !SlotInfo.CSInfo.AllCallSitesDevirted;
1058 if (!HasNonDevirt)
1059 for (auto &P : SlotInfo.ConstCSInfo)
1060 if (!P.second.AllCallSitesDevirted) {
1061 HasNonDevirt = true;
1062 break;
1063 }
1064
1065 if (!HasNonDevirt)
1066 return;
1067
1068 FunctionType *FT =
1069 FunctionType::get(Type::getVoidTy(M.getContext()), {Int8PtrTy}, true);
1070 Function *JT;
1071 if (isa<MDString>(Slot.TypeID)) {
1072 JT = Function::Create(FT, Function::ExternalLinkage,
1073 M.getDataLayout().getProgramAddressSpace(),
1074 getGlobalName(Slot, {}, "branch_funnel"), &M);
1075 JT->setVisibility(GlobalValue::HiddenVisibility);
1076 } else {
1077 JT = Function::Create(FT, Function::InternalLinkage,
1078 M.getDataLayout().getProgramAddressSpace(),
1079 "branch_funnel", &M);
1080 }
1081 JT->addAttribute(1, Attribute::Nest);
1082
1083 std::vector<Value *> JTArgs;
1084 JTArgs.push_back(JT->arg_begin());
1085 for (auto &T : TargetsForSlot) {
1086 JTArgs.push_back(getMemberAddr(T.TM));
1087 JTArgs.push_back(T.Fn);
1088 }
1089
1090 BasicBlock *BB = BasicBlock::Create(M.getContext(), "", JT, nullptr);
1091 Function *Intr =
1092 Intrinsic::getDeclaration(&M, llvm::Intrinsic::icall_branch_funnel, {});
1093
1094 auto *CI = CallInst::Create(Intr, JTArgs, "", BB);
1095 CI->setTailCallKind(CallInst::TCK_MustTail);
1096 ReturnInst::Create(M.getContext(), nullptr, BB);
1097
1098 bool IsExported = false;
1099 applyICallBranchFunnel(SlotInfo, JT, IsExported);
1100 if (IsExported)
1101 Res->TheKind = WholeProgramDevirtResolution::BranchFunnel;
1102}
1103
1104void DevirtModule::applyICallBranchFunnel(VTableSlotInfo &SlotInfo,
1105 Constant *JT, bool &IsExported) {
1106 auto Apply = [&](CallSiteInfo &CSInfo) {
1107 if (CSInfo.isExported())
1108 IsExported = true;
1109 if (CSInfo.AllCallSitesDevirted)
1110 return;
1111 for (auto &&VCallSite : CSInfo.CallSites) {
1112 CallSite CS = VCallSite.CS;
1113
1114 // Jump tables are only profitable if the retpoline mitigation is enabled.
1115 Attribute FSAttr = CS.getCaller()->getFnAttribute("target-features");
1116 if (FSAttr.hasAttribute(Attribute::None) ||
1117 !FSAttr.getValueAsString().contains("+retpoline"))
1118 continue;
1119
1120 if (RemarksEnabled)
1121 VCallSite.emitRemark("branch-funnel",
1122 JT->stripPointerCasts()->getName(), OREGetter);
1123
1124 // Pass the address of the vtable in the nest register, which is r10 on
1125 // x86_64.
1126 std::vector<Type *> NewArgs;
1127 NewArgs.push_back(Int8PtrTy);
1128 for (Type *T : CS.getFunctionType()->params())
1129 NewArgs.push_back(T);
1130 FunctionType *NewFT =
1131 FunctionType::get(CS.getFunctionType()->getReturnType(), NewArgs,
1132 CS.getFunctionType()->isVarArg());
1133 PointerType *NewFTPtr = PointerType::getUnqual(NewFT);
1134
1135 IRBuilder<> IRB(CS.getInstruction());
1136 std::vector<Value *> Args;
1137 Args.push_back(IRB.CreateBitCast(VCallSite.VTable, Int8PtrTy));
1138 for (unsigned I = 0; I != CS.getNumArgOperands(); ++I)
1139 Args.push_back(CS.getArgOperand(I));
1140
1141 CallSite NewCS;
1142 if (CS.isCall())
1143 NewCS = IRB.CreateCall(NewFT, IRB.CreateBitCast(JT, NewFTPtr), Args);
1144 else
1145 NewCS = IRB.CreateInvoke(
1146 NewFT, IRB.CreateBitCast(JT, NewFTPtr),
1147 cast<InvokeInst>(CS.getInstruction())->getNormalDest(),
1148 cast<InvokeInst>(CS.getInstruction())->getUnwindDest(), Args);
1149 NewCS.setCallingConv(CS.getCallingConv());
1150
1151 AttributeList Attrs = CS.getAttributes();
1152 std::vector<AttributeSet> NewArgAttrs;
1153 NewArgAttrs.push_back(AttributeSet::get(
1154 M.getContext(), ArrayRef<Attribute>{Attribute::get(
1155 M.getContext(), Attribute::Nest)}));
1156 for (unsigned I = 0; I + 2 < Attrs.getNumAttrSets(); ++I)
1157 NewArgAttrs.push_back(Attrs.getParamAttributes(I));
1158 NewCS.setAttributes(
1159 AttributeList::get(M.getContext(), Attrs.getFnAttributes(),
1160 Attrs.getRetAttributes(), NewArgAttrs));
1161
1162 CS->replaceAllUsesWith(NewCS.getInstruction());
1163 CS->eraseFromParent();
1164
1165 // This use is no longer unsafe.
1166 if (VCallSite.NumUnsafeUses)
1167 --*VCallSite.NumUnsafeUses;
1168 }
1169 // Don't mark as devirtualized because there may be callers compiled without
1170 // retpoline mitigation, which would mean that they are lowered to
1171 // llvm.type.test and therefore require an llvm.type.test resolution for the
1172 // type identifier.
1173 };
1174 Apply(SlotInfo.CSInfo);
1175 for (auto &P : SlotInfo.ConstCSInfo)
1176 Apply(P.second);
1177}
1178
1179bool DevirtModule::tryEvaluateFunctionsWithArgs(
1180 MutableArrayRef<VirtualCallTarget> TargetsForSlot,
1181 ArrayRef<uint64_t> Args) {
1182 // Evaluate each function and store the result in each target's RetVal
1183 // field.
1184 for (VirtualCallTarget &Target : TargetsForSlot) {
22
Assuming '__begin1' is equal to '__end1'
1185 if (Target.Fn->arg_size() != Args.size() + 1)
1186 return false;
1187
1188 Evaluator Eval(M.getDataLayout(), nullptr);
1189 SmallVector<Constant *, 2> EvalArgs;
1190 EvalArgs.push_back(
1191 Constant::getNullValue(Target.Fn->getFunctionType()->getParamType(0)));
1192 for (unsigned I = 0; I != Args.size(); ++I) {
1193 auto *ArgTy = dyn_cast<IntegerType>(
1194 Target.Fn->getFunctionType()->getParamType(I + 1));
1195 if (!ArgTy)
1196 return false;
1197 EvalArgs.push_back(ConstantInt::get(ArgTy, Args[I]));
1198 }
1199
1200 Constant *RetVal;
1201 if (!Eval.EvaluateFunction(Target.Fn, RetVal, EvalArgs) ||
1202 !isa<ConstantInt>(RetVal))
1203 return false;
1204 Target.RetVal = cast<ConstantInt>(RetVal)->getZExtValue();
1205 }
1206 return true;
23
Returning the value 1, which participates in a condition later
1207}
1208
1209void DevirtModule::applyUniformRetValOpt(CallSiteInfo &CSInfo, StringRef FnName,
1210 uint64_t TheRetVal) {
1211 for (auto Call : CSInfo.CallSites)
1212 Call.replaceAndErase(
1213 "uniform-ret-val", FnName, RemarksEnabled, OREGetter,
1214 ConstantInt::get(cast<IntegerType>(Call.CS.getType()), TheRetVal));
1215 CSInfo.markDevirt();
1216}
1217
1218bool DevirtModule::tryUniformRetValOpt(
1219 MutableArrayRef<VirtualCallTarget> TargetsForSlot, CallSiteInfo &CSInfo,
1220 WholeProgramDevirtResolution::ByArg *Res) {
1221 // Uniform return value optimization. If all functions return the same
1222 // constant, replace all calls with that constant.
1223 uint64_t TheRetVal = TargetsForSlot[0].RetVal;
1224 for (const VirtualCallTarget &Target : TargetsForSlot)
30
Assuming '__begin1' is equal to '__end1'
1225 if (Target.RetVal != TheRetVal)
1226 return false;
1227
1228 if (CSInfo.isExported()) {
31
Calling 'CallSiteInfo::isExported'
34
Returning from 'CallSiteInfo::isExported'
35
Taking true branch
1229 Res->TheKind = WholeProgramDevirtResolution::ByArg::UniformRetVal;
36
Access to field 'TheKind' results in a dereference of a null pointer (loaded from variable 'Res')
1230 Res->Info = TheRetVal;
1231 }
1232
1233 applyUniformRetValOpt(CSInfo, TargetsForSlot[0].Fn->getName(), TheRetVal);
1234 if (RemarksEnabled)
1235 for (auto &&Target : TargetsForSlot)
1236 Target.WasDevirt = true;
1237 return true;
1238}
1239
1240std::string DevirtModule::getGlobalName(VTableSlot Slot,
1241 ArrayRef<uint64_t> Args,
1242 StringRef Name) {
1243 std::string FullName = "__typeid_";
1244 raw_string_ostream OS(FullName);
1245 OS << cast<MDString>(Slot.TypeID)->getString() << '_' << Slot.ByteOffset;
1246 for (uint64_t Arg : Args)
1247 OS << '_' << Arg;
1248 OS << '_' << Name;
1249 return OS.str();
1250}
1251
1252bool DevirtModule::shouldExportConstantsAsAbsoluteSymbols() {
1253 Triple T(M.getTargetTriple());
1254 return (T.getArch() == Triple::x86 || T.getArch() == Triple::x86_64) &&
1255 T.getObjectFormat() == Triple::ELF;
1256}
1257
1258void DevirtModule::exportGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args,
1259 StringRef Name, Constant *C) {
1260 GlobalAlias *GA = GlobalAlias::create(Int8Ty, 0, GlobalValue::ExternalLinkage,
1261 getGlobalName(Slot, Args, Name), C, &M);
1262 GA->setVisibility(GlobalValue::HiddenVisibility);
1263}
1264
1265void DevirtModule::exportConstant(VTableSlot Slot, ArrayRef<uint64_t> Args,
1266 StringRef Name, uint32_t Const,
1267 uint32_t &Storage) {
1268 if (shouldExportConstantsAsAbsoluteSymbols()) {
1269 exportGlobal(
1270 Slot, Args, Name,
1271 ConstantExpr::getIntToPtr(ConstantInt::get(Int32Ty, Const), Int8PtrTy));
1272 return;
1273 }
1274
1275 Storage = Const;
1276}
1277
1278Constant *DevirtModule::importGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args,
1279 StringRef Name) {
1280 Constant *C = M.getOrInsertGlobal(getGlobalName(Slot, Args, Name), Int8Ty);
1281 auto *GV = dyn_cast<GlobalVariable>(C);
1282 if (GV)
1283 GV->setVisibility(GlobalValue::HiddenVisibility);
1284 return C;
1285}
1286
1287Constant *DevirtModule::importConstant(VTableSlot Slot, ArrayRef<uint64_t> Args,
1288 StringRef Name, IntegerType *IntTy,
1289 uint32_t Storage) {
1290 if (!shouldExportConstantsAsAbsoluteSymbols())
1291 return ConstantInt::get(IntTy, Storage);
1292
1293 Constant *C = importGlobal(Slot, Args, Name);
1294 auto *GV = cast<GlobalVariable>(C->stripPointerCasts());
1295 C = ConstantExpr::getPtrToInt(C, IntTy);
1296
1297 // We only need to set metadata if the global is newly created, in which
1298 // case it would not have hidden visibility.
1299 if (GV->hasMetadata(LLVMContext::MD_absolute_symbol))
1300 return C;
1301
1302 auto SetAbsRange = [&](uint64_t Min, uint64_t Max) {
1303 auto *MinC = ConstantAsMetadata::get(ConstantInt::get(IntPtrTy, Min));
1304 auto *MaxC = ConstantAsMetadata::get(ConstantInt::get(IntPtrTy, Max));
1305 GV->setMetadata(LLVMContext::MD_absolute_symbol,
1306 MDNode::get(M.getContext(), {MinC, MaxC}));
1307 };
1308 unsigned AbsWidth = IntTy->getBitWidth();
1309 if (AbsWidth == IntPtrTy->getBitWidth())
1310 SetAbsRange(~0ull, ~0ull); // Full set.
1311 else
1312 SetAbsRange(0, 1ull << AbsWidth);
1313 return C;
1314}
1315
1316void DevirtModule::applyUniqueRetValOpt(CallSiteInfo &CSInfo, StringRef FnName,
1317 bool IsOne,
1318 Constant *UniqueMemberAddr) {
1319 for (auto &&Call : CSInfo.CallSites) {
1320 IRBuilder<> B(Call.CS.getInstruction());
1321 Value *Cmp =
1322 B.CreateICmp(IsOne ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
1323 B.CreateBitCast(Call.VTable, Int8PtrTy), UniqueMemberAddr);
1324 Cmp = B.CreateZExt(Cmp, Call.CS->getType());
1325 Call.replaceAndErase("unique-ret-val", FnName, RemarksEnabled, OREGetter,
1326 Cmp);
1327 }
1328 CSInfo.markDevirt();
1329}
1330
1331Constant *DevirtModule::getMemberAddr(const TypeMemberInfo *M) {
1332 Constant *C = ConstantExpr::getBitCast(M->Bits->GV, Int8PtrTy);
1333 return ConstantExpr::getGetElementPtr(Int8Ty, C,
1334 ConstantInt::get(Int64Ty, M->Offset));
1335}
1336
1337bool DevirtModule::tryUniqueRetValOpt(
1338 unsigned BitWidth, MutableArrayRef<VirtualCallTarget> TargetsForSlot,
1339 CallSiteInfo &CSInfo, WholeProgramDevirtResolution::ByArg *Res,
1340 VTableSlot Slot, ArrayRef<uint64_t> Args) {
1341 // IsOne controls whether we look for a 0 or a 1.
1342 auto tryUniqueRetValOptFor = [&](bool IsOne) {
1343 const TypeMemberInfo *UniqueMember = nullptr;
1344 for (const VirtualCallTarget &Target : TargetsForSlot) {
1345 if (Target.RetVal == (IsOne ? 1 : 0)) {
1346 if (UniqueMember)
1347 return false;
1348 UniqueMember = Target.TM;
1349 }
1350 }
1351
1352 // We should have found a unique member or bailed out by now. We already
1353 // checked for a uniform return value in tryUniformRetValOpt.
1354 assert(UniqueMember)((UniqueMember) ? static_cast<void> (0) : __assert_fail
("UniqueMember", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 1354, __PRETTY_FUNCTION__))
;
1355
1356 Constant *UniqueMemberAddr = getMemberAddr(UniqueMember);
1357 if (CSInfo.isExported()) {
1358 Res->TheKind = WholeProgramDevirtResolution::ByArg::UniqueRetVal;
1359 Res->Info = IsOne;
1360
1361 exportGlobal(Slot, Args, "unique_member", UniqueMemberAddr);
1362 }
1363
1364 // Replace each call with the comparison.
1365 applyUniqueRetValOpt(CSInfo, TargetsForSlot[0].Fn->getName(), IsOne,
1366 UniqueMemberAddr);
1367
1368 // Update devirtualization statistics for targets.
1369 if (RemarksEnabled)
1370 for (auto &&Target : TargetsForSlot)
1371 Target.WasDevirt = true;
1372
1373 return true;
1374 };
1375
1376 if (BitWidth == 1) {
1377 if (tryUniqueRetValOptFor(true))
1378 return true;
1379 if (tryUniqueRetValOptFor(false))
1380 return true;
1381 }
1382 return false;
1383}
1384
1385void DevirtModule::applyVirtualConstProp(CallSiteInfo &CSInfo, StringRef FnName,
1386 Constant *Byte, Constant *Bit) {
1387 for (auto Call : CSInfo.CallSites) {
1388 auto *RetType = cast<IntegerType>(Call.CS.getType());
1389 IRBuilder<> B(Call.CS.getInstruction());
1390 Value *Addr =
1391 B.CreateGEP(Int8Ty, B.CreateBitCast(Call.VTable, Int8PtrTy), Byte);
1392 if (RetType->getBitWidth() == 1) {
1393 Value *Bits = B.CreateLoad(Int8Ty, Addr);
1394 Value *BitsAndBit = B.CreateAnd(Bits, Bit);
1395 auto IsBitSet = B.CreateICmpNE(BitsAndBit, ConstantInt::get(Int8Ty, 0));
1396 Call.replaceAndErase("virtual-const-prop-1-bit", FnName, RemarksEnabled,
1397 OREGetter, IsBitSet);
1398 } else {
1399 Value *ValAddr = B.CreateBitCast(Addr, RetType->getPointerTo());
1400 Value *Val = B.CreateLoad(RetType, ValAddr);
1401 Call.replaceAndErase("virtual-const-prop", FnName, RemarksEnabled,
1402 OREGetter, Val);
1403 }
1404 }
1405 CSInfo.markDevirt();
1406}
1407
1408bool DevirtModule::tryVirtualConstProp(
1409 MutableArrayRef<VirtualCallTarget> TargetsForSlot, VTableSlotInfo &SlotInfo,
1410 WholeProgramDevirtResolution *Res, VTableSlot Slot) {
1411 // This only works if the function returns an integer.
1412 auto RetType = dyn_cast<IntegerType>(TargetsForSlot[0].Fn->getReturnType());
16
Assuming the object is a 'IntegerType'
1413 if (!RetType
16.1
'RetType' is non-null
)
17
Taking false branch
1414 return false;
1415 unsigned BitWidth = RetType->getBitWidth();
1416 if (BitWidth > 64)
18
Assuming 'BitWidth' is <= 64
19
Taking false branch
1417 return false;
1418
1419 // Make sure that each function is defined, does not access memory, takes at
1420 // least one argument, does not use its first argument (which we assume is
1421 // 'this'), and has the same return type.
1422 //
1423 // Note that we test whether this copy of the function is readnone, rather
1424 // than testing function attributes, which must hold for any copy of the
1425 // function, even a less optimized version substituted at link time. This is
1426 // sound because the virtual constant propagation optimizations effectively
1427 // inline all implementations of the virtual function into each call site,
1428 // rather than using function attributes to perform local optimization.
1429 for (VirtualCallTarget &Target : TargetsForSlot) {
20
Assuming '__begin1' is equal to '__end1'
1430 if (Target.Fn->isDeclaration() ||
1431 computeFunctionBodyMemoryAccess(*Target.Fn, AARGetter(*Target.Fn)) !=
1432 MAK_ReadNone ||
1433 Target.Fn->arg_empty() || !Target.Fn->arg_begin()->use_empty() ||
1434 Target.Fn->getReturnType() != RetType)
1435 return false;
1436 }
1437
1438 for (auto &&CSByConstantArg : SlotInfo.ConstCSInfo) {
1439 if (!tryEvaluateFunctionsWithArgs(TargetsForSlot, CSByConstantArg.first))
21
Calling 'DevirtModule::tryEvaluateFunctionsWithArgs'
24
Returning from 'DevirtModule::tryEvaluateFunctionsWithArgs'
25
Taking false branch
1440 continue;
1441
1442 WholeProgramDevirtResolution::ByArg *ResByArg = nullptr;
26
'ResByArg' initialized to a null pointer value
1443 if (Res
26.1
'Res' is null
)
27
Taking false branch
1444 ResByArg = &Res->ResByArg[CSByConstantArg.first];
1445
1446 if (tryUniformRetValOpt(TargetsForSlot, CSByConstantArg.second, ResByArg))
28
Passing null pointer value via 3rd parameter 'Res'
29
Calling 'DevirtModule::tryUniformRetValOpt'
1447 continue;
1448
1449 if (tryUniqueRetValOpt(BitWidth, TargetsForSlot, CSByConstantArg.second,
1450 ResByArg, Slot, CSByConstantArg.first))
1451 continue;
1452
1453 // Find an allocation offset in bits in all vtables associated with the
1454 // type.
1455 uint64_t AllocBefore =
1456 findLowestOffset(TargetsForSlot, /*IsAfter=*/false, BitWidth);
1457 uint64_t AllocAfter =
1458 findLowestOffset(TargetsForSlot, /*IsAfter=*/true, BitWidth);
1459
1460 // Calculate the total amount of padding needed to store a value at both
1461 // ends of the object.
1462 uint64_t TotalPaddingBefore = 0, TotalPaddingAfter = 0;
1463 for (auto &&Target : TargetsForSlot) {
1464 TotalPaddingBefore += std::max<int64_t>(
1465 (AllocBefore + 7) / 8 - Target.allocatedBeforeBytes() - 1, 0);
1466 TotalPaddingAfter += std::max<int64_t>(
1467 (AllocAfter + 7) / 8 - Target.allocatedAfterBytes() - 1, 0);
1468 }
1469
1470 // If the amount of padding is too large, give up.
1471 // FIXME: do something smarter here.
1472 if (std::min(TotalPaddingBefore, TotalPaddingAfter) > 128)
1473 continue;
1474
1475 // Calculate the offset to the value as a (possibly negative) byte offset
1476 // and (if applicable) a bit offset, and store the values in the targets.
1477 int64_t OffsetByte;
1478 uint64_t OffsetBit;
1479 if (TotalPaddingBefore <= TotalPaddingAfter)
1480 setBeforeReturnValues(TargetsForSlot, AllocBefore, BitWidth, OffsetByte,
1481 OffsetBit);
1482 else
1483 setAfterReturnValues(TargetsForSlot, AllocAfter, BitWidth, OffsetByte,
1484 OffsetBit);
1485
1486 if (RemarksEnabled)
1487 for (auto &&Target : TargetsForSlot)
1488 Target.WasDevirt = true;
1489
1490
1491 if (CSByConstantArg.second.isExported()) {
1492 ResByArg->TheKind = WholeProgramDevirtResolution::ByArg::VirtualConstProp;
1493 exportConstant(Slot, CSByConstantArg.first, "byte", OffsetByte,
1494 ResByArg->Byte);
1495 exportConstant(Slot, CSByConstantArg.first, "bit", 1ULL << OffsetBit,
1496 ResByArg->Bit);
1497 }
1498
1499 // Rewrite each call to a load from OffsetByte/OffsetBit.
1500 Constant *ByteConst = ConstantInt::get(Int32Ty, OffsetByte);
1501 Constant *BitConst = ConstantInt::get(Int8Ty, 1ULL << OffsetBit);
1502 applyVirtualConstProp(CSByConstantArg.second,
1503 TargetsForSlot[0].Fn->getName(), ByteConst, BitConst);
1504 }
1505 return true;
1506}
1507
1508void DevirtModule::rebuildGlobal(VTableBits &B) {
1509 if (B.Before.Bytes.empty() && B.After.Bytes.empty())
1510 return;
1511
1512 // Align the before byte array to the global's minimum alignment so that we
1513 // don't break any alignment requirements on the global.
1514 MaybeAlign Alignment(B.GV->getAlignment());
1515 if (!Alignment)
1516 Alignment =
1517 Align(M.getDataLayout().getABITypeAlignment(B.GV->getValueType()));
1518 B.Before.Bytes.resize(alignTo(B.Before.Bytes.size(), Alignment));
1519
1520 // Before was stored in reverse order; flip it now.
1521 for (size_t I = 0, Size = B.Before.Bytes.size(); I != Size / 2; ++I)
1522 std::swap(B.Before.Bytes[I], B.Before.Bytes[Size - 1 - I]);
1523
1524 // Build an anonymous global containing the before bytes, followed by the
1525 // original initializer, followed by the after bytes.
1526 auto NewInit = ConstantStruct::getAnon(
1527 {ConstantDataArray::get(M.getContext(), B.Before.Bytes),
1528 B.GV->getInitializer(),
1529 ConstantDataArray::get(M.getContext(), B.After.Bytes)});
1530 auto NewGV =
1531 new GlobalVariable(M, NewInit->getType(), B.GV->isConstant(),
1532 GlobalVariable::PrivateLinkage, NewInit, "", B.GV);
1533 NewGV->setSection(B.GV->getSection());
1534 NewGV->setComdat(B.GV->getComdat());
1535 NewGV->setAlignment(MaybeAlign(B.GV->getAlignment()));
1536
1537 // Copy the original vtable's metadata to the anonymous global, adjusting
1538 // offsets as required.
1539 NewGV->copyMetadata(B.GV, B.Before.Bytes.size());
1540
1541 // Build an alias named after the original global, pointing at the second
1542 // element (the original initializer).
1543 auto Alias = GlobalAlias::create(
1544 B.GV->getInitializer()->getType(), 0, B.GV->getLinkage(), "",
1545 ConstantExpr::getGetElementPtr(
1546 NewInit->getType(), NewGV,
1547 ArrayRef<Constant *>{ConstantInt::get(Int32Ty, 0),
1548 ConstantInt::get(Int32Ty, 1)}),
1549 &M);
1550 Alias->setVisibility(B.GV->getVisibility());
1551 Alias->takeName(B.GV);
1552
1553 B.GV->replaceAllUsesWith(Alias);
1554 B.GV->eraseFromParent();
1555}
1556
1557bool DevirtModule::areRemarksEnabled() {
1558 const auto &FL = M.getFunctionList();
1559 for (const Function &Fn : FL) {
1560 const auto &BBL = Fn.getBasicBlockList();
1561 if (BBL.empty())
1562 continue;
1563 auto DI = OptimizationRemark(DEBUG_TYPE"wholeprogramdevirt", "", DebugLoc(), &BBL.front());
1564 return DI.isEnabled();
1565 }
1566 return false;
1567}
1568
1569void DevirtModule::scanTypeTestUsers(Function *TypeTestFunc,
1570 Function *AssumeFunc) {
1571 // Find all virtual calls via a virtual table pointer %p under an assumption
1572 // of the form llvm.assume(llvm.type.test(%p, %md)). This indicates that %p
1573 // points to a member of the type identifier %md. Group calls by (type ID,
1574 // offset) pair (effectively the identity of the virtual function) and store
1575 // to CallSlots.
1576 DenseSet<CallSite> SeenCallSites;
1577 for (auto I = TypeTestFunc->use_begin(), E = TypeTestFunc->use_end();
1578 I != E;) {
1579 auto CI = dyn_cast<CallInst>(I->getUser());
1580 ++I;
1581 if (!CI)
1582 continue;
1583
1584 // Search for virtual calls based on %p and add them to DevirtCalls.
1585 SmallVector<DevirtCallSite, 1> DevirtCalls;
1586 SmallVector<CallInst *, 1> Assumes;
1587 auto &DT = LookupDomTree(*CI->getFunction());
1588 findDevirtualizableCallsForTypeTest(DevirtCalls, Assumes, CI, DT);
1589
1590 // If we found any, add them to CallSlots.
1591 if (!Assumes.empty()) {
1592 Metadata *TypeId =
1593 cast<MetadataAsValue>(CI->getArgOperand(1))->getMetadata();
1594 Value *Ptr = CI->getArgOperand(0)->stripPointerCasts();
1595 for (DevirtCallSite Call : DevirtCalls) {
1596 // Only add this CallSite if we haven't seen it before. The vtable
1597 // pointer may have been CSE'd with pointers from other call sites,
1598 // and we don't want to process call sites multiple times. We can't
1599 // just skip the vtable Ptr if it has been seen before, however, since
1600 // it may be shared by type tests that dominate different calls.
1601 if (SeenCallSites.insert(Call.CS).second)
1602 CallSlots[{TypeId, Call.Offset}].addCallSite(Ptr, Call.CS, nullptr);
1603 }
1604 }
1605
1606 // We no longer need the assumes or the type test.
1607 for (auto Assume : Assumes)
1608 Assume->eraseFromParent();
1609 // We can't use RecursivelyDeleteTriviallyDeadInstructions here because we
1610 // may use the vtable argument later.
1611 if (CI->use_empty())
1612 CI->eraseFromParent();
1613 }
1614}
1615
1616void DevirtModule::scanTypeCheckedLoadUsers(Function *TypeCheckedLoadFunc) {
1617 Function *TypeTestFunc = Intrinsic::getDeclaration(&M, Intrinsic::type_test);
1618
1619 for (auto I = TypeCheckedLoadFunc->use_begin(),
1620 E = TypeCheckedLoadFunc->use_end();
1621 I != E;) {
1622 auto CI = dyn_cast<CallInst>(I->getUser());
1623 ++I;
1624 if (!CI)
1625 continue;
1626
1627 Value *Ptr = CI->getArgOperand(0);
1628 Value *Offset = CI->getArgOperand(1);
1629 Value *TypeIdValue = CI->getArgOperand(2);
1630 Metadata *TypeId = cast<MetadataAsValue>(TypeIdValue)->getMetadata();
1631
1632 SmallVector<DevirtCallSite, 1> DevirtCalls;
1633 SmallVector<Instruction *, 1> LoadedPtrs;
1634 SmallVector<Instruction *, 1> Preds;
1635 bool HasNonCallUses = false;
1636 auto &DT = LookupDomTree(*CI->getFunction());
1637 findDevirtualizableCallsForTypeCheckedLoad(DevirtCalls, LoadedPtrs, Preds,
1638 HasNonCallUses, CI, DT);
1639
1640 // Start by generating "pessimistic" code that explicitly loads the function
1641 // pointer from the vtable and performs the type check. If possible, we will
1642 // eliminate the load and the type check later.
1643
1644 // If possible, only generate the load at the point where it is used.
1645 // This helps avoid unnecessary spills.
1646 IRBuilder<> LoadB(
1647 (LoadedPtrs.size() == 1 && !HasNonCallUses) ? LoadedPtrs[0] : CI);
1648 Value *GEP = LoadB.CreateGEP(Int8Ty, Ptr, Offset);
1649 Value *GEPPtr = LoadB.CreateBitCast(GEP, PointerType::getUnqual(Int8PtrTy));
1650 Value *LoadedValue = LoadB.CreateLoad(Int8PtrTy, GEPPtr);
1651
1652 for (Instruction *LoadedPtr : LoadedPtrs) {
1653 LoadedPtr->replaceAllUsesWith(LoadedValue);
1654 LoadedPtr->eraseFromParent();
1655 }
1656
1657 // Likewise for the type test.
1658 IRBuilder<> CallB((Preds.size() == 1 && !HasNonCallUses) ? Preds[0] : CI);
1659 CallInst *TypeTestCall = CallB.CreateCall(TypeTestFunc, {Ptr, TypeIdValue});
1660
1661 for (Instruction *Pred : Preds) {
1662 Pred->replaceAllUsesWith(TypeTestCall);
1663 Pred->eraseFromParent();
1664 }
1665
1666 // We have already erased any extractvalue instructions that refer to the
1667 // intrinsic call, but the intrinsic may have other non-extractvalue uses
1668 // (although this is unlikely). In that case, explicitly build a pair and
1669 // RAUW it.
1670 if (!CI->use_empty()) {
1671 Value *Pair = UndefValue::get(CI->getType());
1672 IRBuilder<> B(CI);
1673 Pair = B.CreateInsertValue(Pair, LoadedValue, {0});
1674 Pair = B.CreateInsertValue(Pair, TypeTestCall, {1});
1675 CI->replaceAllUsesWith(Pair);
1676 }
1677
1678 // The number of unsafe uses is initially the number of uses.
1679 auto &NumUnsafeUses = NumUnsafeUsesForTypeTest[TypeTestCall];
1680 NumUnsafeUses = DevirtCalls.size();
1681
1682 // If the function pointer has a non-call user, we cannot eliminate the type
1683 // check, as one of those users may eventually call the pointer. Increment
1684 // the unsafe use count to make sure it cannot reach zero.
1685 if (HasNonCallUses)
1686 ++NumUnsafeUses;
1687 for (DevirtCallSite Call : DevirtCalls) {
1688 CallSlots[{TypeId, Call.Offset}].addCallSite(Ptr, Call.CS,
1689 &NumUnsafeUses);
1690 }
1691
1692 CI->eraseFromParent();
1693 }
1694}
1695
1696void DevirtModule::importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo) {
1697 auto *TypeId = dyn_cast<MDString>(Slot.TypeID);
1698 if (!TypeId)
1699 return;
1700 const TypeIdSummary *TidSummary =
1701 ImportSummary->getTypeIdSummary(TypeId->getString());
1702 if (!TidSummary)
1703 return;
1704 auto ResI = TidSummary->WPDRes.find(Slot.ByteOffset);
1705 if (ResI == TidSummary->WPDRes.end())
1706 return;
1707 const WholeProgramDevirtResolution &Res = ResI->second;
1708
1709 if (Res.TheKind == WholeProgramDevirtResolution::SingleImpl) {
1710 assert(!Res.SingleImplName.empty())((!Res.SingleImplName.empty()) ? static_cast<void> (0) :
__assert_fail ("!Res.SingleImplName.empty()", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 1710, __PRETTY_FUNCTION__))
;
1711 // The type of the function in the declaration is irrelevant because every
1712 // call site will cast it to the correct type.
1713 Constant *SingleImpl =
1714 cast<Constant>(M.getOrInsertFunction(Res.SingleImplName,
1715 Type::getVoidTy(M.getContext()))
1716 .getCallee());
1717
1718 // This is the import phase so we should not be exporting anything.
1719 bool IsExported = false;
1720 applySingleImplDevirt(SlotInfo, SingleImpl, IsExported);
1721 assert(!IsExported)((!IsExported) ? static_cast<void> (0) : __assert_fail (
"!IsExported", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 1721, __PRETTY_FUNCTION__))
;
1722 }
1723
1724 for (auto &CSByConstantArg : SlotInfo.ConstCSInfo) {
1725 auto I = Res.ResByArg.find(CSByConstantArg.first);
1726 if (I == Res.ResByArg.end())
1727 continue;
1728 auto &ResByArg = I->second;
1729 // FIXME: We should figure out what to do about the "function name" argument
1730 // to the apply* functions, as the function names are unavailable during the
1731 // importing phase. For now we just pass the empty string. This does not
1732 // impact correctness because the function names are just used for remarks.
1733 switch (ResByArg.TheKind) {
1734 case WholeProgramDevirtResolution::ByArg::UniformRetVal:
1735 applyUniformRetValOpt(CSByConstantArg.second, "", ResByArg.Info);
1736 break;
1737 case WholeProgramDevirtResolution::ByArg::UniqueRetVal: {
1738 Constant *UniqueMemberAddr =
1739 importGlobal(Slot, CSByConstantArg.first, "unique_member");
1740 applyUniqueRetValOpt(CSByConstantArg.second, "", ResByArg.Info,
1741 UniqueMemberAddr);
1742 break;
1743 }
1744 case WholeProgramDevirtResolution::ByArg::VirtualConstProp: {
1745 Constant *Byte = importConstant(Slot, CSByConstantArg.first, "byte",
1746 Int32Ty, ResByArg.Byte);
1747 Constant *Bit = importConstant(Slot, CSByConstantArg.first, "bit", Int8Ty,
1748 ResByArg.Bit);
1749 applyVirtualConstProp(CSByConstantArg.second, "", Byte, Bit);
1750 break;
1751 }
1752 default:
1753 break;
1754 }
1755 }
1756
1757 if (Res.TheKind == WholeProgramDevirtResolution::BranchFunnel) {
1758 // The type of the function is irrelevant, because it's bitcast at calls
1759 // anyhow.
1760 Constant *JT = cast<Constant>(
1761 M.getOrInsertFunction(getGlobalName(Slot, {}, "branch_funnel"),
1762 Type::getVoidTy(M.getContext()))
1763 .getCallee());
1764 bool IsExported = false;
1765 applyICallBranchFunnel(SlotInfo, JT, IsExported);
1766 assert(!IsExported)((!IsExported) ? static_cast<void> (0) : __assert_fail (
"!IsExported", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 1766, __PRETTY_FUNCTION__))
;
1767 }
1768}
1769
1770void DevirtModule::removeRedundantTypeTests() {
1771 auto True = ConstantInt::getTrue(M.getContext());
1772 for (auto &&U : NumUnsafeUsesForTypeTest) {
1773 if (U.second == 0) {
1774 U.first->replaceAllUsesWith(True);
1775 U.first->eraseFromParent();
1776 }
1777 }
1778}
1779
1780bool DevirtModule::run() {
1781 // If only some of the modules were split, we cannot correctly perform
1782 // this transformation. We already checked for the presense of type tests
1783 // with partially split modules during the thin link, and would have emitted
1784 // an error if any were found, so here we can simply return.
1785 if ((ExportSummary && ExportSummary->partiallySplitLTOUnits()) ||
1
Assuming field 'ExportSummary' is null
1786 (ImportSummary && ImportSummary->partiallySplitLTOUnits()))
2
Assuming field 'ImportSummary' is null
1787 return false;
1788
1789 Function *TypeTestFunc =
1790 M.getFunction(Intrinsic::getName(Intrinsic::type_test));
1791 Function *TypeCheckedLoadFunc =
1792 M.getFunction(Intrinsic::getName(Intrinsic::type_checked_load));
1793 Function *AssumeFunc = M.getFunction(Intrinsic::getName(Intrinsic::assume));
1794
1795 // Normally if there are no users of the devirtualization intrinsics in the
1796 // module, this pass has nothing to do. But if we are exporting, we also need
1797 // to handle any users that appear only in the function summaries.
1798 if (!ExportSummary
2.1
Field 'ExportSummary' is null
&&
1799 (!TypeTestFunc || TypeTestFunc->use_empty() || !AssumeFunc ||
3
Assuming 'TypeTestFunc' is non-null
4
Assuming 'AssumeFunc' is non-null
1800 AssumeFunc->use_empty()) &&
1801 (!TypeCheckedLoadFunc || TypeCheckedLoadFunc->use_empty()))
1802 return false;
1803
1804 if (TypeTestFunc
4.1
'TypeTestFunc' is non-null
&& AssumeFunc
4.2
'AssumeFunc' is non-null
)
5
Taking true branch
1805 scanTypeTestUsers(TypeTestFunc, AssumeFunc);
1806
1807 if (TypeCheckedLoadFunc)
6
Assuming 'TypeCheckedLoadFunc' is null
7
Taking false branch
1808 scanTypeCheckedLoadUsers(TypeCheckedLoadFunc);
1809
1810 if (ImportSummary
7.1
Field 'ImportSummary' is null
) {
8
Taking false branch
1811 for (auto &S : CallSlots)
1812 importResolution(S.first, S.second);
1813
1814 removeRedundantTypeTests();
1815
1816 // The rest of the code is only necessary when exporting or during regular
1817 // LTO, so we are done.
1818 return true;
1819 }
1820
1821 // Rebuild type metadata into a map for easy lookup.
1822 std::vector<VTableBits> Bits;
1823 DenseMap<Metadata *, std::set<TypeMemberInfo>> TypeIdMap;
1824 buildTypeIdentifierMap(Bits, TypeIdMap);
1825 if (TypeIdMap.empty())
9
Assuming the condition is false
10
Taking false branch
1826 return true;
1827
1828 // Collect information from summary about which calls to try to devirtualize.
1829 if (ExportSummary
10.1
Field 'ExportSummary' is null
) {
11
Taking false branch
1830 DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID;
1831 for (auto &P : TypeIdMap) {
1832 if (auto *TypeId = dyn_cast<MDString>(P.first))
1833 MetadataByGUID[GlobalValue::getGUID(TypeId->getString())].push_back(
1834 TypeId);
1835 }
1836
1837 for (auto &P : *ExportSummary) {
1838 for (auto &S : P.second.SummaryList) {
1839 auto *FS = dyn_cast<FunctionSummary>(S.get());
1840 if (!FS)
1841 continue;
1842 // FIXME: Only add live functions.
1843 for (FunctionSummary::VFuncId VF : FS->type_test_assume_vcalls()) {
1844 for (Metadata *MD : MetadataByGUID[VF.GUID]) {
1845 CallSlots[{MD, VF.Offset}].CSInfo.addSummaryTypeTestAssumeUser(FS);
1846 }
1847 }
1848 for (FunctionSummary::VFuncId VF : FS->type_checked_load_vcalls()) {
1849 for (Metadata *MD : MetadataByGUID[VF.GUID]) {
1850 CallSlots[{MD, VF.Offset}].CSInfo.addSummaryTypeCheckedLoadUser(FS);
1851 }
1852 }
1853 for (const FunctionSummary::ConstVCall &VC :
1854 FS->type_test_assume_const_vcalls()) {
1855 for (Metadata *MD : MetadataByGUID[VC.VFunc.GUID]) {
1856 CallSlots[{MD, VC.VFunc.Offset}]
1857 .ConstCSInfo[VC.Args]
1858 .addSummaryTypeTestAssumeUser(FS);
1859 }
1860 }
1861 for (const FunctionSummary::ConstVCall &VC :
1862 FS->type_checked_load_const_vcalls()) {
1863 for (Metadata *MD : MetadataByGUID[VC.VFunc.GUID]) {
1864 CallSlots[{MD, VC.VFunc.Offset}]
1865 .ConstCSInfo[VC.Args]
1866 .addSummaryTypeCheckedLoadUser(FS);
1867 }
1868 }
1869 }
1870 }
1871 }
1872
1873 // For each (type, offset) pair:
1874 bool DidVirtualConstProp = false;
1875 std::map<std::string, Function*> DevirtTargets;
1876 for (auto &S : CallSlots) {
1877 // Search each of the members of the type identifier for the virtual
1878 // function implementation at offset S.first.ByteOffset, and add to
1879 // TargetsForSlot.
1880 std::vector<VirtualCallTarget> TargetsForSlot;
1881 if (tryFindVirtualCallTargets(TargetsForSlot, TypeIdMap[S.first.TypeID],
12
Taking true branch
1882 S.first.ByteOffset)) {
1883 WholeProgramDevirtResolution *Res = nullptr;
1884 if (ExportSummary && isa<MDString>(S.first.TypeID))
13
Assuming field 'ExportSummary' is null
1885 Res = &ExportSummary
1886 ->getOrInsertTypeIdSummary(
1887 cast<MDString>(S.first.TypeID)->getString())
1888 .WPDRes[S.first.ByteOffset];
1889
1890 if (!trySingleImplDevirt(ExportSummary, TargetsForSlot, S.second, Res)) {
14
Taking true branch
1891 DidVirtualConstProp |=
1892 tryVirtualConstProp(TargetsForSlot, S.second, Res, S.first);
15
Calling 'DevirtModule::tryVirtualConstProp'
1893
1894 tryICallBranchFunnel(TargetsForSlot, S.second, Res, S.first);
1895 }
1896
1897 // Collect functions devirtualized at least for one call site for stats.
1898 if (RemarksEnabled)
1899 for (const auto &T : TargetsForSlot)
1900 if (T.WasDevirt)
1901 DevirtTargets[T.Fn->getName()] = T.Fn;
1902 }
1903
1904 // CFI-specific: if we are exporting and any llvm.type.checked.load
1905 // intrinsics were *not* devirtualized, we need to add the resulting
1906 // llvm.type.test intrinsics to the function summaries so that the
1907 // LowerTypeTests pass will export them.
1908 if (ExportSummary && isa<MDString>(S.first.TypeID)) {
1909 auto GUID =
1910 GlobalValue::getGUID(cast<MDString>(S.first.TypeID)->getString());
1911 for (auto FS : S.second.CSInfo.SummaryTypeCheckedLoadUsers)
1912 FS->addTypeTest(GUID);
1913 for (auto &CCS : S.second.ConstCSInfo)
1914 for (auto FS : CCS.second.SummaryTypeCheckedLoadUsers)
1915 FS->addTypeTest(GUID);
1916 }
1917 }
1918
1919 if (RemarksEnabled) {
1920 // Generate remarks for each devirtualized function.
1921 for (const auto &DT : DevirtTargets) {
1922 Function *F = DT.second;
1923
1924 using namespace ore;
1925 OREGetter(F).emit(OptimizationRemark(DEBUG_TYPE"wholeprogramdevirt", "Devirtualized", F)
1926 << "devirtualized "
1927 << NV("FunctionName", DT.first));
1928 }
1929 }
1930
1931 removeRedundantTypeTests();
1932
1933 // Rebuild each global we touched as part of virtual constant propagation to
1934 // include the before and after bytes.
1935 if (DidVirtualConstProp)
1936 for (VTableBits &B : Bits)
1937 rebuildGlobal(B);
1938
1939 // We have lowered or deleted the type checked load intrinsics, so we no
1940 // longer have enough information to reason about the liveness of virtual
1941 // function pointers in GlobalDCE.
1942 for (GlobalVariable &GV : M.globals())
1943 GV.eraseMetadata(LLVMContext::MD_vcall_visibility);
1944
1945 return true;
1946}
1947
1948void DevirtIndex::run() {
1949 if (ExportSummary.typeIdCompatibleVtableMap().empty())
1950 return;
1951
1952 DenseMap<GlobalValue::GUID, std::vector<StringRef>> NameByGUID;
1953 for (auto &P : ExportSummary.typeIdCompatibleVtableMap()) {
1954 NameByGUID[GlobalValue::getGUID(P.first)].push_back(P.first);
1955 }
1956
1957 // Collect information from summary about which calls to try to devirtualize.
1958 for (auto &P : ExportSummary) {
1959 for (auto &S : P.second.SummaryList) {
1960 auto *FS = dyn_cast<FunctionSummary>(S.get());
1961 if (!FS)
1962 continue;
1963 // FIXME: Only add live functions.
1964 for (FunctionSummary::VFuncId VF : FS->type_test_assume_vcalls()) {
1965 for (StringRef Name : NameByGUID[VF.GUID]) {
1966 CallSlots[{Name, VF.Offset}].CSInfo.addSummaryTypeTestAssumeUser(FS);
1967 }
1968 }
1969 for (FunctionSummary::VFuncId VF : FS->type_checked_load_vcalls()) {
1970 for (StringRef Name : NameByGUID[VF.GUID]) {
1971 CallSlots[{Name, VF.Offset}].CSInfo.addSummaryTypeCheckedLoadUser(FS);
1972 }
1973 }
1974 for (const FunctionSummary::ConstVCall &VC :
1975 FS->type_test_assume_const_vcalls()) {
1976 for (StringRef Name : NameByGUID[VC.VFunc.GUID]) {
1977 CallSlots[{Name, VC.VFunc.Offset}]
1978 .ConstCSInfo[VC.Args]
1979 .addSummaryTypeTestAssumeUser(FS);
1980 }
1981 }
1982 for (const FunctionSummary::ConstVCall &VC :
1983 FS->type_checked_load_const_vcalls()) {
1984 for (StringRef Name : NameByGUID[VC.VFunc.GUID]) {
1985 CallSlots[{Name, VC.VFunc.Offset}]
1986 .ConstCSInfo[VC.Args]
1987 .addSummaryTypeCheckedLoadUser(FS);
1988 }
1989 }
1990 }
1991 }
1992
1993 std::set<ValueInfo> DevirtTargets;
1994 // For each (type, offset) pair:
1995 for (auto &S : CallSlots) {
1996 // Search each of the members of the type identifier for the virtual
1997 // function implementation at offset S.first.ByteOffset, and add to
1998 // TargetsForSlot.
1999 std::vector<ValueInfo> TargetsForSlot;
2000 auto TidSummary = ExportSummary.getTypeIdCompatibleVtableSummary(S.first.TypeID);
2001 assert(TidSummary)((TidSummary) ? static_cast<void> (0) : __assert_fail (
"TidSummary", "/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp"
, 2001, __PRETTY_FUNCTION__))
;
2002 if (tryFindVirtualCallTargets(TargetsForSlot, *TidSummary,
2003 S.first.ByteOffset)) {
2004 WholeProgramDevirtResolution *Res =
2005 &ExportSummary.getOrInsertTypeIdSummary(S.first.TypeID)
2006 .WPDRes[S.first.ByteOffset];
2007
2008 if (!trySingleImplDevirt(TargetsForSlot, S.first, S.second, Res,
2009 DevirtTargets))
2010 continue;
2011 }
2012 }
2013
2014 // Optionally have the thin link print message for each devirtualized
2015 // function.
2016 if (PrintSummaryDevirt)
2017 for (const auto &DT : DevirtTargets)
2018 errs() << "Devirtualized call to " << DT << "\n";
2019
2020 return;
2021}