[clang] Support VFE in thinLTO (PR #69735)
Manman Ren via cfe-commits
cfe-commits at lists.llvm.org
Fri Oct 20 10:49:28 PDT 2023
https://github.com/manman-ren updated https://github.com/llvm/llvm-project/pull/69735
>From 1adce63e663203f858de86cfa231527ee2284505 Mon Sep 17 00:00:00 2001
From: Manman Ren <mren at fb.com>
Date: Thu, 5 Oct 2023 10:56:53 -0700
Subject: [PATCH] Support VFE in thinLTO
We add a run of GlobalDCEPass with ImportSummary. When ImportSummary is true, we remove
virtual functions in vtables with VCallVisibility not Public. In this run, the regular
GlobalDCEPass::AddVirtualFunctionDependencies will be bypassed, we will use
ImportSummary to decide which virtual functions to remove.
Discussion points:
1> FuncsWithNonVtableRef: this is currently in ModuleSummaryIndex, does it
make sense to be part of FunctionSummary?
std::set<GlobalValue::GUID> FuncsWithNonVtableRef;
2> ComputeDependencies is copied from GlobalDCE to ModuleSummaryAnalysis, for the former,
ConstantDependenciesCache is a member variable
3> match from summary to Function in IR
Resolution is saved in std::set<GlobalValue::GUID> VFuncsToBeRemoved
Use F->getGUID() or GlobalValue::getGUID(F->getName()) when searching in VFuncsToBeRemoved
TODO:
1> support hybrid Regular/ThinLTO
2> support legacy thinLTO backend (ThinLTOCodeGenerator)
---
clang/lib/Driver/ToolChains/Clang.cpp | 4 +-
clang/test/CodeGenCXX/vfe-thin.cpp | 123 +++++++++
.../Driver/virtual-function-elimination.cpp | 3 +-
llvm/include/llvm/AsmParser/LLParser.h | 1 +
llvm/include/llvm/AsmParser/LLToken.h | 1 +
llvm/include/llvm/Bitcode/LLVMBitCodes.h | 1 +
llvm/include/llvm/IR/ModuleSummaryIndex.h | 22 ++
llvm/include/llvm/Transforms/IPO/GlobalDCE.h | 15 +-
llvm/lib/Analysis/ModuleSummaryAnalysis.cpp | 65 ++++-
llvm/lib/AsmParser/LLParser.cpp | 16 ++
llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 5 +
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 15 +
llvm/lib/IR/AsmWriter.cpp | 13 +
llvm/lib/LTO/LTO.cpp | 8 +
llvm/lib/Passes/PassBuilderPipelines.cpp | 6 +
llvm/lib/Transforms/IPO/GlobalDCE.cpp | 261 +++++++++++++++++-
16 files changed, 551 insertions(+), 8 deletions(-)
create mode 100644 clang/test/CodeGenCXX/vfe-thin.cpp
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index c74f6ff447261dc..d59eb98eb2777e1 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7378,10 +7378,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
if (VirtualFunctionElimination) {
// VFE requires full LTO (currently, this might be relaxed to allow ThinLTO
// in the future).
- if (LTOMode != LTOK_Full)
+ if (LTOMode != LTOK_Full && LTOMode != LTOK_Thin)
D.Diag(diag::err_drv_argument_only_allowed_with)
<< "-fvirtual-function-elimination"
- << "-flto=full";
+ << "-flto";
CmdArgs.push_back("-fvirtual-function-elimination");
}
diff --git a/clang/test/CodeGenCXX/vfe-thin.cpp b/clang/test/CodeGenCXX/vfe-thin.cpp
new file mode 100644
index 000000000000000..b05d196060353c1
--- /dev/null
+++ b/clang/test/CodeGenCXX/vfe-thin.cpp
@@ -0,0 +1,123 @@
+// REQUIRES: system-darwin
+// RUN: rm -rf %t_devirt && mkdir %t_devirt
+// RUN: rm -rf %t.dir
+// RUN: split-file %s %t.dir
+
+// RUN: %clang -flto=thin -target arm64-apple-ios16 -emit-llvm -c -fwhole-program-vtables -fvirtual-function-elimination -mllvm -enable-vfe-summary -o %t.main.bc %t.dir/vfe-main.cpp
+// RUN: llvm-dis %t.main.bc -o - | FileCheck %s --check-prefix=CHECK
+// RUN: %clang -flto=thin -target arm64-apple-ios16 -emit-llvm -c -fwhole-program-vtables -fvirtual-function-elimination -mllvm -enable-vfe-summary -o %t.input.bc %t.dir/vfe-input.cpp
+// RUN: llvm-dis %t.input.bc -o - | FileCheck %s --check-prefix=INPUT
+
+// RUN: llvm-lto2 run %t.main.bc %t.input.bc -save-temps -enable-vfe-on-thinlto -o %t.out \
+// RUN: -r=%t.main.bc,__Z6test_1P1A,pl \
+// RUN: -r=%t.main.bc,__Z4testv,pl \
+// RUN: -r=%t.main.bc,__Znwm, \
+// RUN: -r=%t.main.bc,__ZN1AC1Ev,pl \
+// RUN: -r=%t.main.bc,___gxx_personality_v0, \
+// RUN: -r=%t.main.bc,__ZN1AC2Ev,pl \
+// RUN: -r=%t.main.bc,__ZN1BC2Ev,pl \
+// RUN: -r=%t.main.bc,__ZN1BC1Ev,pl \
+// RUN: -r=%t.main.bc,__ZN1A3fooEv,pl \
+// RUN: -r=%t.main.bc,__ZN1A3barEv,pl \
+// RUN: -r=%t.main.bc,__Z6test_2P1B,pl \
+// RUN: -r=%t.main.bc,_main,plx \
+// RUN: -r=%t.main.bc,__ZdlPv \
+// RUN: -r=%t.main.bc,__ZTV1A,pl \
+// RUN: -r=%t.main.bc,__ZTV1B, \
+// RUN: -r=%t.main.bc,__ZTVN10__cxxabiv117__class_type_infoE, \
+// RUN: -r=%t.main.bc,__ZTS1A,pl \
+// RUN: -r=%t.main.bc,__ZTI1A,pl \
+// RUN: -r=%t.input.bc,__ZN1CC2Ev,pl \
+// RUN: -r=%t.input.bc,__ZN1CC1Ev,pl \
+// RUN: -r=%t.input.bc,__Z6test_3P1C,pl \
+// RUN: -r=%t.input.bc,__Z6test_4P1C,pl \
+// RUN: -r=%t.input.bc,__Z6test_5P1CMS_FvvE,pl \
+// RUN: -r=%t.input.bc,__ZTV1C,
+
+// RUN: llvm-dis %t.out.1.0.preopt.bc -o - | FileCheck %s --check-prefix=ORIGINAL
+// RUN: llvm-dis %t.out.1.4.opt.bc -o - | FileCheck %s --check-prefix=AFTERVFE
+// ORIGINAL: define{{.*}}_ZN1A3barEv
+// AFTERVFE-NOT: define{{.*}}_ZN1A3barEv
+
+//--- vfe-main.cpp
+// CHECK: @_ZTV1A = {{.*}}constant {{.*}}@_ZTI1A{{.*}}@_ZN1A3fooEv{{.*}}_ZN1A3barEv{{.*}}!type [[A16:![0-9]+]]
+// CHECK-NOT: @_ZTV1B = {{.*}}!type
+struct __attribute__((visibility("hidden"))) A {
+ A();
+ virtual void foo();
+ virtual void bar();
+};
+
+__attribute__((used)) void test_1(A *p) {
+ // CHECK-LABEL: define{{.*}} void @_Z6test_1P1A
+ // CHECK: [[VTABLE:%.+]] = load
+ // CHECK: @llvm.type.checked.load(ptr {{%.+}}, i32 0, metadata !"_ZTS1A")
+ p->foo();
+}
+
+__attribute__((used)) A *test() {
+ return new (A)();
+}
+
+struct __attribute__((visibility("hidden"))) B {
+ B();
+ virtual void foo();
+};
+
+A::A() {}
+B::B() {}
+void A::foo() {}
+void A::bar() {}
+void test_2(B *p) {
+ // CHECK-LABEL: define{{.*}} void @_Z6test_2P1B
+ // CHECK: [[VTABLE:%.+]] = load
+ // CHECK: @llvm.type.checked.load(ptr {{%.+}}, i32 0, metadata !"_ZTS1B")
+ p->foo();
+}
+
+// INPUT-NOT: @_ZTV1C = {{.*}}!type
+// INPUT-LABEL: define{{.*}} void @_Z6test_3P1C
+// INPUT: [[LOAD:%.+]] = {{.*}}call { ptr, i1 } @llvm.type.checked.load(ptr {{%.+}}, i32 0, metadata !"_ZTS1C")
+// INPUT: [[FN_PTR:%.+]] = extractvalue { ptr, i1 } [[LOAD]], 0
+// INPUT: call void [[FN_PTR]](
+
+// INPUT-LABEL: define{{.*}} void @_Z6test_4P1C
+// INPUT: [[LOAD:%.+]] = {{.*}}call { ptr, i1 } @llvm.type.checked.load(ptr {{%.+}}, i32 8, metadata !"_ZTS1C")
+// INPUT: [[FN_PTR:%.+]] = extractvalue { ptr, i1 } [[LOAD]], 0
+// INPUT: call void [[FN_PTR]](
+
+int main() {
+}
+
+// CHECK: [[BAR:\^[0-9]+]] = gv: (name: "_ZN1A3barEv", {{.*}}
+// CHECK: FuncsWithNonVtableRef
+// CHECK-NOT: [[BAR]]
+//--- vfe-input.cpp
+struct __attribute__((visibility("hidden"))) C {
+ C();
+ virtual void foo();
+ virtual void bar();
+};
+
+C::C() {}
+void test_3(C *p) {
+ // C has hidden visibility, so we generate type.checked.load to allow VFE.
+ p->foo();
+}
+
+void test_4(C *p) {
+ // When using type.checked.load, we pass the vtable offset to the intrinsic,
+ // rather than adding it to the pointer with a GEP.
+ p->bar();
+}
+
+void test_5(C *p, void (C::*q)(void)) {
+ // We also use type.checked.load for the virtual side of member function
+ // pointer calls. We use a GEP to calculate the address to load from and pass
+ // 0 as the offset to the intrinsic, because we know that the load must be
+ // from exactly the point marked by one of the function-type metadatas (in
+ // this case "_ZTSM1CFvvE.virtual"). If we passed the offset from the member
+ // function pointer to the intrinsic, this information would be lost. No
+ // codegen changes on the non-virtual side.
+ (p->*q)();
+}
diff --git a/clang/test/Driver/virtual-function-elimination.cpp b/clang/test/Driver/virtual-function-elimination.cpp
index b65fac2393b3ca6..493bf9399f96033 100644
--- a/clang/test/Driver/virtual-function-elimination.cpp
+++ b/clang/test/Driver/virtual-function-elimination.cpp
@@ -1,6 +1,5 @@
// RUN: not %clang -target x86_64-unknown-linux -fvirtual-function-elimination -### %s 2>&1 | FileCheck --check-prefix=BAD-LTO %s
-// RUN: not %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto=thin -### %s 2>&1 | FileCheck --check-prefix=BAD-LTO %s
-// BAD-LTO: invalid argument '-fvirtual-function-elimination' only allowed with '-flto=full'
+// BAD-LTO: invalid argument '-fvirtual-function-elimination' only allowed with '-flto'
// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto -### %s 2>&1 | FileCheck --check-prefix=GOOD %s
// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto=full -### %s 2>&1 | FileCheck --check-prefix=GOOD %s
diff --git a/llvm/include/llvm/AsmParser/LLParser.h b/llvm/include/llvm/AsmParser/LLParser.h
index eca908a24aac7b2..22a446984893bda 100644
--- a/llvm/include/llvm/AsmParser/LLParser.h
+++ b/llvm/include/llvm/AsmParser/LLParser.h
@@ -362,6 +362,7 @@ namespace llvm {
bool parseGVReference(ValueInfo &VI, unsigned &GVId);
bool parseSummaryIndexFlags();
bool parseBlockCount();
+ bool parseFuncsWithNonVtableRefEntry(unsigned ID);
bool parseGVEntry(unsigned ID);
bool parseFunctionSummary(std::string Name, GlobalValue::GUID, unsigned ID);
bool parseVariableSummary(std::string Name, GlobalValue::GUID, unsigned ID);
diff --git a/llvm/include/llvm/AsmParser/LLToken.h b/llvm/include/llvm/AsmParser/LLToken.h
index 673dc58ce6451e3..f707caf3d42c834 100644
--- a/llvm/include/llvm/AsmParser/LLToken.h
+++ b/llvm/include/llvm/AsmParser/LLToken.h
@@ -399,6 +399,7 @@ enum Kind {
kw_args,
kw_typeid,
kw_typeidCompatibleVTable,
+ kw_FuncsWithNonVtableRef,
kw_summary,
kw_typeTestRes,
kw_kind,
diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
index 52e76356a892e45..68d96ed4b4fb4eb 100644
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -319,6 +319,7 @@ enum GlobalValueSummarySymtabCodes {
// numver x version]
FS_COMBINED_ALLOC_INFO = 29,
FS_STACK_IDS = 30,
+ OBJC_FUNC_NON_VTABLE_REF = 31,
};
enum MetadataCodes {
diff --git a/llvm/include/llvm/IR/ModuleSummaryIndex.h b/llvm/include/llvm/IR/ModuleSummaryIndex.h
index cd02c71adddfc25..39d492fe6ef7827 100644
--- a/llvm/include/llvm/IR/ModuleSummaryIndex.h
+++ b/llvm/include/llvm/IR/ModuleSummaryIndex.h
@@ -1362,6 +1362,8 @@ class ModuleSummaryIndex {
// Temporary map while building StackIds list. Clear when index is completely
// built via releaseTemporaryMemory.
std::map<uint64_t, unsigned> StackIdToIndex;
+ std::set<GlobalValue::GUID> FuncsWithNonVtableRef;
+ std::set<GlobalValue::GUID> VFuncsToBeRemoved; // no need to serialize
// YAML I/O support.
friend yaml::MappingTraits<ModuleSummaryIndex>;
@@ -1811,6 +1813,26 @@ class ModuleSummaryIndex {
}
}
+ bool isFuncWithNonVtableRef(GlobalValue::GUID fId) const {
+ return FuncsWithNonVtableRef.count(fId);
+ }
+ void addFuncWithNonVtableRef(GlobalValue::GUID fId) {
+ FuncsWithNonVtableRef.insert(fId);
+ }
+ const std::set<GlobalValue::GUID> &funcsWithNonVtableRef() const {
+ return FuncsWithNonVtableRef;
+ }
+
+ bool isFuncToBeRemoved(GlobalValue::GUID fId) const {
+ return VFuncsToBeRemoved.count(fId);
+ }
+ void addFuncToBeRemoved(GlobalValue::GUID fId) {
+ VFuncsToBeRemoved.insert(fId);
+ }
+ const std::set<GlobalValue::GUID> &funcsToBeRemoved() const {
+ return VFuncsToBeRemoved;
+ }
+
/// Print to an output stream.
void print(raw_ostream &OS, bool IsForDebug = false) const;
diff --git a/llvm/include/llvm/Transforms/IPO/GlobalDCE.h b/llvm/include/llvm/Transforms/IPO/GlobalDCE.h
index 92c30d4b54a2612..7b953ad45940526 100644
--- a/llvm/include/llvm/Transforms/IPO/GlobalDCE.h
+++ b/llvm/include/llvm/Transforms/IPO/GlobalDCE.h
@@ -35,7 +35,16 @@ class Value;
/// Pass to remove unused function declarations.
class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
public:
- GlobalDCEPass(bool InLTOPostLink = false) : InLTOPostLink(InLTOPostLink) {}
+ GlobalDCEPass(bool InLTOPostLink = false)
+ : InLTOPostLink(InLTOPostLink), ExportSummary(nullptr),
+ ImportSummary(nullptr) {}
+ GlobalDCEPass(ModuleSummaryIndex *ExportSummary,
+ const ModuleSummaryIndex *ImportSummary,
+ bool InLTOPostLink = false)
+ : InLTOPostLink(InLTOPostLink), ExportSummary(ExportSummary),
+ ImportSummary(ImportSummary) {
+ assert(!(ExportSummary && ImportSummary));
+ }
PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
@@ -44,6 +53,8 @@ class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
private:
bool InLTOPostLink = false;
+ ModuleSummaryIndex *ExportSummary;
+ const ModuleSummaryIndex *ImportSummary;
SmallPtrSet<GlobalValue*, 32> AliveGlobals;
@@ -78,6 +89,8 @@ class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U);
};
+void runVFEOnIndex(ModuleSummaryIndex &Summary,
+ function_ref<bool(GlobalValue::GUID)> isRetained);
}
#endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H
diff --git a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
index a88622efa12db8c..d5b3be2664c44c4 100644
--- a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
+++ b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -54,6 +54,7 @@
#include <algorithm>
#include <cassert>
#include <cstdint>
+#include <unordered_map>
#include <vector>
using namespace llvm;
@@ -80,6 +81,9 @@ static cl::opt<std::string> ModuleSummaryDotFile(
"module-summary-dot-file", cl::Hidden, cl::value_desc("filename"),
cl::desc("File to emit dot graph of new summary into"));
+static cl::opt<bool> EnableVFESummary("enable-vfe-summary", cl::init(false),
+ cl::Hidden, cl::ZeroOrMore,
+ cl::desc("enable VFE with ThinLTO"));
extern cl::opt<bool> ScalePartialSampleProfileWorkingSetSize;
// Walk through the operands of a given User via worklist iteration and populate
@@ -229,7 +233,11 @@ static void addIntrinsicToSummary(
for (auto &Call : DevirtCalls)
addVCallToSet(Call, Guid, TypeCheckedLoadVCalls,
TypeCheckedLoadConstVCalls);
-
+ if (EnableVFESummary && !HasNonCallUses &&
+ DevirtCalls.empty()) { // for VFE with thinLTO
+ auto *Offset = cast<ConstantInt>(CI->getArgOperand(1));
+ TypeCheckedLoadVCalls.insert({Guid, Offset->getZExtValue()});
+ }
break;
}
default:
@@ -775,6 +783,58 @@ static void computeVariableSummary(ModuleSummaryIndex &Index,
Index.addGlobalValueSummary(V, std::move(GVarSummary));
}
+static void ComputeDependencies(
+ Value *V, SmallPtrSetImpl<const GlobalValue *> &Deps,
+ std::unordered_map<Constant *, SmallPtrSet<const GlobalValue *, 8>>
+ &ConstantDependenciesCache) {
+ if (auto *I = dyn_cast<Instruction>(V)) {
+ Function *Parent = I->getParent()->getParent();
+ Deps.insert(Parent);
+ } else if (auto *GV = dyn_cast<GlobalValue>(V)) {
+ Deps.insert(GV);
+ } else if (auto *CE = dyn_cast<Constant>(V)) {
+ // Avoid walking the whole tree of a big ConstantExprs multiple times.
+ auto Where = ConstantDependenciesCache.find(CE);
+ if (Where != ConstantDependenciesCache.end()) {
+ auto const &K = Where->second;
+ Deps.insert(K.begin(), K.end());
+ } else {
+ SmallPtrSetImpl<const GlobalValue *> &LocalDeps =
+ ConstantDependenciesCache[CE];
+ for (User *CEUser : CE->users())
+ ComputeDependencies(CEUser, LocalDeps, ConstantDependenciesCache);
+ Deps.insert(LocalDeps.begin(), LocalDeps.end());
+ }
+ }
+}
+
+static void updateNonVtableRef(const Module &M, ModuleSummaryIndex &Index) {
+ if (!EnableVFESummary)
+ return;
+ // If a function has a reference from a non-vtable, it is not safe
+ // to be eliminated by VFE.
+ std::unordered_map<Constant *, SmallPtrSet<const GlobalValue *, 8>>
+ ConstantDependenciesCache;
+ for (auto &F : M) {
+ SmallPtrSet<const GlobalValue *, 8> Deps;
+ for (const User *U : F.users())
+ ComputeDependencies(const_cast<User *>(U), Deps,
+ ConstantDependenciesCache);
+ Deps.erase(&F); // Remove self-reference.
+ for (const GlobalValue *GVU : Deps) {
+ // Check if GVU is a vtable.
+ if (auto *gv = dyn_cast<GlobalVariable>(GVU)) {
+ if (gv->hasMetadata(LLVMContext::MD_type)) {
+ continue;
+ }
+ }
+ // Otherwise, add GUID for F to a list.
+ Index.addFuncWithNonVtableRef(F.getGUID());
+ break;
+ }
+ }
+}
+
static void computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
DenseSet<GlobalValue::GUID> &CantBePromoted) {
// Skip summary for indirect function aliases as summary for aliasee will not
@@ -933,6 +993,9 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
!LocalsUsed.empty() || HasLocalInlineAsmSymbol,
CantBePromoted, IsThinLTO, GetSSICallback);
}
+ // If a function has a reference from a non-vtable, it is not safe
+ // to be eliminated by VFE.
+ updateNonVtableRef(M, Index);
// Compute summaries for all variables defined in module, and save in the
// index.
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 04eabc94cfc6abe..cdf083d707f1f8f 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -950,6 +950,9 @@ bool LLParser::parseSummaryEntry() {
case lltok::kw_blockcount:
result = parseBlockCount();
break;
+ case lltok::kw_FuncsWithNonVtableRef:
+ result = parseFuncsWithNonVtableRefEntry(SummaryID);
+ break;
default:
result = error(Lex.getLoc(), "unexpected summary kind");
break;
@@ -8203,6 +8206,19 @@ bool LLParser::parseTypeIdSummary(TypeIdSummary &TIS) {
static ValueInfo EmptyVI =
ValueInfo(false, (GlobalValueSummaryMapTy::value_type *)-8);
+/// FuncsWithNonVtableRefEntry
+/// ::= 'FuncsWithNonVtableRef' ':' '('
+/// ')'
+bool LLParser::parseFuncsWithNonVtableRefEntry(unsigned ID) {
+ assert(Lex.getKind() == lltok::kw_FuncsWithNonVtableRef);
+ Lex.Lex();
+ std::string Name;
+ if (parseToken(lltok::colon, "expected ':' here") ||
+ parseToken(lltok::lparen, "expected '(' here"))
+ return true;
+ return false;
+}
+
/// TypeIdCompatibleVtableEntry
/// ::= 'typeidCompatibleVTable' ':' '(' 'name' ':' STRINGCONSTANT ','
/// TypeIdCompatibleVtableInfo
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 1d1ec988a93d847..52b5926ee284ea1 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -7497,6 +7497,11 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
LastSeenGUID = 0;
break;
}
+ case bitc::OBJC_FUNC_NON_VTABLE_REF: {
+ for (unsigned I = 0; I != Record.size(); I++)
+ TheIndex.addFuncWithNonVtableRef(Record[I]);
+ break;
+ }
case bitc::FS_TYPE_TESTS:
assert(PendingTypeTests.empty());
llvm::append_range(PendingTypeTests, Record);
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index e991d055f33474b..22d7f9b639f0405 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3906,6 +3906,19 @@ static void writeTypeIdSummaryRecord(SmallVector<uint64_t, 64> &NameVals,
W.second);
}
+static void writeFuncWithNonVTableRef(BitstreamWriter &Stream,
+ const std::set<uint64_t> &List,
+ SmallVectorImpl<uint64_t> &Record) {
+ if (List.empty())
+ return;
+
+ // For deterministic, we should sort the list.
+ for (auto l : List)
+ Record.push_back(l);
+ Stream.EmitRecord(bitc::OBJC_FUNC_NON_VTABLE_REF, Record);
+ Record.clear();
+}
+
static void writeTypeIdCompatibleVtableSummaryRecord(
SmallVector<uint64_t, 64> &NameVals, StringTableBuilder &StrtabBuilder,
const std::string &Id, const TypeIdCompatibleVtableInfo &Summary,
@@ -4246,6 +4259,8 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
Stream.EmitRecord(bitc::FS_ALIAS, NameVals, FSAliasAbbrev);
NameVals.clear();
}
+ SmallVector<uint64_t, 64> Record;
+ writeFuncWithNonVTableRef(Stream, Index->funcsWithNonVtableRef(), Record);
for (auto &S : Index->typeIdCompatibleVtableMap()) {
writeTypeIdCompatibleVtableSummaryRecord(NameVals, StrtabBuilder, S.first,
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index e190d82127908db..80610387860f68a 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2941,6 +2941,19 @@ void AssemblyWriter::printModuleSummaryIndex() {
Out << ") ; guid = " << GUID << "\n";
}
+ // Print FuncsWithNonVtableRef.
+ // Need to find a case where this is set.
+ if (!TheIndex->funcsWithNonVtableRef().empty()) {
+ Out << "^" << NumSlots << " = FuncsWithNonVtableRef: (";
+ FieldSeparator FS;
+ for (auto FID : TheIndex->funcsWithNonVtableRef()) {
+ Out << FS;
+ Out << "^" << Machine.getGUIDSlot(FID);
+ }
+ Out << ")\n";
+ ++NumSlots;
+ }
+
// Don't emit flags when it's not really needed (value is zero by default).
if (TheIndex->getFlags()) {
Out << "^" << NumSlots << " = flags: " << TheIndex->getFlags() << "\n";
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 4a64aa4593d543c..5ce4f30215d4eac 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -51,6 +51,7 @@
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/IPO/GlobalDCE.h"
#include "llvm/Transforms/IPO/MemProfContextDisambiguation.h"
#include "llvm/Transforms/IPO/WholeProgramDevirt.h"
#include "llvm/Transforms/Utils/FunctionImportUtils.h"
@@ -75,6 +76,7 @@ cl::opt<bool> EnableLTOInternalization(
"enable-lto-internalization", cl::init(true), cl::Hidden,
cl::desc("Enable global value internalization in LTO"));
}
+extern cl::opt<bool> EnableVFEOnThinLTO;
/// Indicate we are linking with an allocator that supports hot/cold operator
/// new interfaces.
@@ -1736,6 +1738,12 @@ Error LTO::runThinLTO(AddStreamFn AddStream, FileCache Cache,
std::map<ValueInfo, std::vector<VTableSlotSummary>> LocalWPDTargetsMap;
runWholeProgramDevirtOnIndex(ThinLTO.CombinedIndex, ExportedGUIDs,
LocalWPDTargetsMap);
+ if (EnableVFEOnThinLTO) {
+ auto isRetained = [&](GlobalValue::GUID CalleeGUID) {
+ return GUIDPreservedSymbols.count(CalleeGUID);
+ };
+ runVFEOnIndex(ThinLTO.CombinedIndex, isRetained);
+ }
auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) {
return ThinLTO.PrevailingModuleForGUID[GUID] == S->modulePath();
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 78e0e6353056343..348a11bcd17631d 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -281,6 +281,9 @@ cl::opt<bool> EnableMemProfContextDisambiguation(
cl::ZeroOrMore, cl::desc("Enable MemProf context disambiguation"));
extern cl::opt<bool> EnableInferAlignmentPass;
+cl::opt<bool> EnableVFEOnThinLTO("enable-vfe-on-thinlto", cl::init(false),
+ cl::Hidden, cl::ZeroOrMore,
+ cl::desc("enable VFE with ThinLTO"));
PipelineTuningOptions::PipelineTuningOptions() {
LoopInterleaving = true;
@@ -1583,6 +1586,9 @@ ModulePassManager PassBuilder::buildThinLTODefaultPipeline(
OptimizationLevel Level, const ModuleSummaryIndex *ImportSummary) {
ModulePassManager MPM;
+ if (EnableVFEOnThinLTO && ImportSummary)
+ MPM.addPass(GlobalDCEPass(nullptr, ImportSummary));
+
if (ImportSummary) {
// For ThinLTO we must apply the context disambiguation decisions early, to
// ensure we can correctly match the callsites to summary data.
diff --git a/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
index e36d524d7667ab3..17da4ed7912b3b5 100644
--- a/llvm/lib/Transforms/IPO/GlobalDCE.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalDCE.cpp
@@ -18,6 +18,7 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/TypeMetadataUtils.h"
+#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
@@ -26,6 +27,11 @@
#include "llvm/Transforms/Utils/CtorUtils.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/IR/ModuleSummaryIndex.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/GlobPattern.h"
+#include "llvm/Support/MemoryBuffer.h"
+
using namespace llvm;
#define DEBUG_TYPE "globaldce"
@@ -34,12 +40,223 @@ static cl::opt<bool>
ClEnableVFE("enable-vfe", cl::Hidden, cl::init(true),
cl::desc("Enable virtual function elimination"));
+static cl::opt<std::string> ClReadSummary(
+ "globaldce-read-summary",
+ cl::desc("Read summary from given bitcode before running pass"),
+ cl::Hidden);
+
STATISTIC(NumAliases , "Number of global aliases removed");
STATISTIC(NumFunctions, "Number of functions removed");
STATISTIC(NumIFuncs, "Number of indirect functions removed");
STATISTIC(NumVariables, "Number of global variables removed");
STATISTIC(NumVFuncs, "Number of virtual functions removed");
+namespace llvm {
+
+// Returning a representative summary for the vtable, also set isSafe.
+static const GlobalVarSummary *
+getVTableFuncsForTId(const TypeIdOffsetVtableInfo &P, bool &isSafe) {
+ // Find a representative copy of the vtable initializer.
+ const GlobalVarSummary *VS = nullptr;
+ bool LocalFound = false;
+ for (auto &S : P.VTableVI.getSummaryList()) {
+ if (GlobalValue::isLocalLinkage(S->linkage())) {
+ if (LocalFound) {
+ isSafe = false;
+ return nullptr;
+ }
+ LocalFound = true;
+ }
+ auto *CurVS = cast<GlobalVarSummary>(S->getBaseObject());
+ // Ignore if vTableFuncs is empty and vtable is available_externally.
+ if (!CurVS->vTableFuncs().empty() ||
+ !GlobalValue::isAvailableExternallyLinkage(S->linkage())) {
+ VS = CurVS;
+ if (VS->getVCallVisibility() == GlobalObject::VCallVisibilityPublic) {
+ isSafe = false;
+ return VS;
+ }
+ }
+ }
+
+ if (!VS) {
+ isSafe = false;
+ return nullptr;
+ }
+ if (!VS->isLive()) {
+ isSafe = true;
+ return nullptr;
+ }
+ isSafe = true;
+ return VS;
+}
+
+static void collectSafeVTables(
+ ModuleSummaryIndex &Summary,
+ DenseMap<GlobalValue::GUID, std::vector<StringRef>> &NameByGUID,
+ std::map<ValueInfo, std::vector<VirtFuncOffset>> &VFESafeVTablesAndFns) {
+ // Update VFESafeVTablesAndFns with information from summary.
+ for (auto &P : Summary.typeIdCompatibleVtableMap()) {
+ NameByGUID[GlobalValue::getGUID(P.first)].push_back(P.first);
+ LLVM_DEBUG(dbgs() << "TId " << GlobalValue::getGUID(P.first) << " "
+ << P.first << "\n");
+ }
+ llvm::errs() << "VFEThinLTO number of TIds: " << NameByGUID.size() << "\n";
+
+ // VFESafeVTablesAndFns: map from VI for vTable to VI for vfunc
+ std::map<ValueInfo, std::set<GlobalValue::GUID>> vFuncSet;
+ unsigned numSafeVFuncs = 0;
+ // Collect stats for VTables (safe, public-visibility, other).
+ std::set<ValueInfo> vTablePublicVis;
+ std::set<ValueInfo> vTableOther;
+ for (auto &TidSummary : Summary.typeIdCompatibleVtableMap()) {
+ for (const TypeIdOffsetVtableInfo &P : TidSummary.second) {
+ LLVM_DEBUG(dbgs() << "TId-vTable " << TidSummary.first << " "
+ << P.VTableVI.name() << " " << P.AddressPointOffset
+ << "\n");
+ bool isSafe = false;
+ const GlobalVarSummary *VS = getVTableFuncsForTId(P, isSafe);
+ if (!isSafe && VS)
+ vTablePublicVis.insert(P.VTableVI);
+ if ((isSafe && !VS) || (!isSafe && !VS))
+ vTableOther.insert(P.VTableVI);
+ if (!isSafe || !VS) {
+ continue;
+ }
+
+ // Go through VS->vTableFuncs
+ for (auto VTP : VS->vTableFuncs()) {
+ if (vFuncSet.find(P.VTableVI) == vFuncSet.end() ||
+ !vFuncSet[P.VTableVI].count(VTP.FuncVI.getGUID())) {
+ VFESafeVTablesAndFns[P.VTableVI].push_back(VTP);
+ LLVM_DEBUG(dbgs()
+ << "vTable " << P.VTableVI.name() << " "
+ << VTP.FuncVI.name() << " " << VTP.VTableOffset << "\n");
+ ++numSafeVFuncs;
+ }
+ vFuncSet[P.VTableVI].insert(VTP.FuncVI.getGUID());
+ }
+ }
+ }
+ llvm::errs() << "VFEThinLTO number of vTables: " << vFuncSet.size() << " "
+ << vTablePublicVis.size() << " " << vTableOther.size() << "\n";
+ llvm::errs() << "VFEThinLTO numSafeVFuncs: " << numSafeVFuncs << "\n";
+}
+
+static void checkVTableLoadsIndex(
+ ModuleSummaryIndex &Summary,
+ DenseMap<GlobalValue::GUID, std::vector<StringRef>> &NameByGUID,
+ std::map<ValueInfo, std::vector<VirtFuncOffset>> &VFESafeVTablesAndFns,
+ std::map<ValueInfo, std::vector<ValueInfo>> &VFuncsAndCallers) {
+ // Go through Function summarys for intrinsics, also funcHasNonVTableRef to
+ // erase entries from VFESafeVTableAndFns.
+ for (auto &PI : Summary) {
+ for (auto &S : PI.second.SummaryList) {
+ auto *FS = dyn_cast<FunctionSummary>(S.get());
+ if (!FS)
+ continue;
+ // We should ignore Tid if there is a type.checked.load with Offset not
+ // ConstantInt. Currently ModuleSummaryAnalysis will update TypeTests.
+ for (GlobalValue::GUID G : FS->type_tests()) {
+ if (NameByGUID.find(G) == NameByGUID.end())
+ continue;
+ auto TidSummary =
+ Summary.getTypeIdCompatibleVtableSummary(NameByGUID[G][0]);
+ for (const TypeIdOffsetVtableInfo &P : *TidSummary) {
+ LLVM_DEBUG(dbgs() << "unsafe-vtable due to type_tests: "
+ << P.VTableVI.name() << "\n");
+ VFESafeVTablesAndFns.erase(P.VTableVI);
+ }
+ }
+ // Go through vTableFuncs to find the potential callees
+ auto CheckVLoad = [&](GlobalValue::GUID TId, uint64_t Offset) {
+ if (!NameByGUID.count(TId)) {
+ return;
+ }
+ auto TidSummary =
+ Summary.getTypeIdCompatibleVtableSummary(NameByGUID[TId][0]);
+ for (const TypeIdOffsetVtableInfo &P : *TidSummary) {
+ uint64_t VTableOffset = P.AddressPointOffset;
+ bool isSafe = false;
+ const GlobalVarSummary *VS = getVTableFuncsForTId(P, isSafe);
+ if (!isSafe || !VS)
+ continue;
+ unsigned foundCnt = 0;
+ for (auto VTP : VS->vTableFuncs()) {
+ if (VTP.VTableOffset != VTableOffset + Offset)
+ continue;
+ assert(foundCnt == 0);
+ foundCnt = 1;
+ VFuncsAndCallers[VTP.FuncVI].push_back(Summary.getValueInfo(PI));
+ }
+ if (foundCnt == 0) {
+ // A vtable is unsafe if a given vtable for the typeId doesn't have
+ // the offset.
+ VFESafeVTablesAndFns.erase(P.VTableVI);
+ LLVM_DEBUG(dbgs() << "unsafe-vtable can't find offset "
+ << P.VTableVI.name() << " "
+ << (VTableOffset + Offset) << "\n");
+ }
+ }
+ };
+ for (FunctionSummary::VFuncId VF : FS->type_checked_load_vcalls()) {
+ CheckVLoad(VF.GUID, VF.Offset);
+ }
+ for (const FunctionSummary::ConstVCall &VC :
+ FS->type_checked_load_const_vcalls()) {
+ CheckVLoad(VC.VFunc.GUID, VC.VFunc.Offset);
+ }
+ }
+ }
+}
+
+void runVFEOnIndex(ModuleSummaryIndex &Summary,
+ function_ref<bool(GlobalValue::GUID)> isRetained) {
+ if (Summary.typeIdCompatibleVtableMap().empty())
+ return;
+
+ DenseMap<GlobalValue::GUID, std::vector<StringRef>> NameByGUID;
+ std::map<ValueInfo, std::vector<VirtFuncOffset>> VFESafeVTablesAndFns;
+ collectSafeVTables(Summary, NameByGUID, VFESafeVTablesAndFns);
+
+ // Go through Function summarys for intrinsics, also funcHasNonVTableRef to
+ // erase entries from VFESafeVTableAndFns.
+ std::map<ValueInfo, std::vector<ValueInfo>> VFuncsAndCallers;
+ checkVTableLoadsIndex(Summary, NameByGUID, VFESafeVTablesAndFns,
+ VFuncsAndCallers);
+ llvm::errs() << "VFEThinLTO number of vTables: "
+ << VFESafeVTablesAndFns.size() << "\n";
+
+ // Generate list of vfuncs that can be removed.
+ std::set<ValueInfo> candidateSet;
+ for (auto entry : VFESafeVTablesAndFns) {
+ for (auto vfunc : entry.second) {
+ if (Summary.isFuncWithNonVtableRef(vfunc.FuncVI.getGUID())) {
+ LLVM_DEBUG(dbgs() << "unsafe-vfunc with non-vtable ref "
+ << vfunc.FuncVI.name() << "\n");
+ continue;
+ }
+ if (!candidateSet.count(vfunc.FuncVI)) {
+ candidateSet.insert(vfunc.FuncVI);
+ }
+ }
+ }
+
+ // It is possible to use a workList to recursively mark vfuncs as removable.
+ // For now, only remove vfuncs that are not in VFuncsAndCallers.
+ std::set<ValueInfo> removable;
+ for (auto vfunc : candidateSet) {
+ if (!VFuncsAndCallers.count(vfunc) && !isRetained(vfunc.getGUID()))
+ removable.insert(vfunc);
+ }
+
+ for (auto fVI : removable) {
+ Summary.addFuncToBeRemoved(fVI.getGUID());
+ }
+ llvm::errs() << "VFEThinLTO removable " << removable.size() << "\n";
+}
+} // end namespace llvm
+
/// Returns true if F is effectively empty.
static bool isEmptyFunction(Function *F) {
// Skip external functions.
@@ -220,6 +437,8 @@ void GlobalDCEPass::ScanTypeCheckedLoadIntrinsics(Module &M) {
}
void GlobalDCEPass::AddVirtualFunctionDependencies(Module &M) {
+ if (ImportSummary)
+ return; // only use results from Index with ThinLTO
if (!ClEnableVFE)
return;
@@ -247,6 +466,23 @@ void GlobalDCEPass::AddVirtualFunctionDependencies(Module &M) {
}
PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
+ // Handle the command-line summary arguments. This code is for testing
+ // purposes only, so we handle errors directly.
+ std::unique_ptr<ModuleSummaryIndex> Summary =
+ std::make_unique<ModuleSummaryIndex>(/*HaveGVs=*/false);
+ if (!ClReadSummary.empty()) {
+ ExitOnError ExitOnErr("-globaldce-read-summary: " + ClReadSummary + ": ");
+ auto ReadSummaryFile =
+ ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary)));
+ if (Expected<std::unique_ptr<ModuleSummaryIndex>> SummaryOrErr =
+ getModuleSummaryIndex(*ReadSummaryFile)) {
+ Summary = std::move(*SummaryOrErr);
+ }
+ ImportSummary = Summary.get();
+ auto isRetained = [&](GlobalValue::GUID CalleeGUID) { return false; };
+ runVFEOnIndex(*(const_cast<ModuleSummaryIndex *>(ImportSummary)),
+ isRetained);
+ }
bool Changed = false;
// The algorithm first computes the set L of global variables that are
@@ -338,12 +574,33 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
// The second pass drops the bodies of functions which are dead...
std::vector<Function *> DeadFunctions;
- for (Function &F : M)
+ std::set<Function *> DeadFunctionsSet;
+ auto funcRemovedInIndex = [&](Function *F) -> bool {
+ if (!ImportSummary)
+ return false;
+ auto &vfuncsRemoved = ImportSummary->funcsToBeRemoved();
+ // If function is internalized, its current GUID will be different
+ // from the GUID in funcsToBeRemoved. Treat it as a global and search
+ // again.
+ if (vfuncsRemoved.count(F->getGUID()))
+ return true;
+ if (vfuncsRemoved.count(GlobalValue::getGUID(F->getName())))
+ return true;
+ return false;
+ };
+ for (Function &F : M) {
if (!AliveGlobals.count(&F)) {
- DeadFunctions.push_back(&F); // Keep track of dead globals
+ DeadFunctions.push_back(&F); // Keep track of dead globals
+ DeadFunctionsSet.insert(&F);
+ if (!F.isDeclaration())
+ F.deleteBody();
+ } else if (funcRemovedInIndex(&F)) {
+ DeadFunctions.push_back(&F); // Keep track of dead globals
+ DeadFunctionsSet.insert(&F);
if (!F.isDeclaration())
F.deleteBody();
}
+ }
// The third pass drops targets of aliases which are dead...
std::vector<GlobalAlias*> DeadAliases;
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