[llvm] 3040272 - [ThinLTO] Support aliased GlobalIFunc
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 20 15:30:43 PDT 2022
Author: Schrodinger ZHU Yifan
Date: 2022-07-20T15:30:38-07:00
New Revision: 304027206c883b61b76465b3c2a139927ea71344
URL: https://github.com/llvm/llvm-project/commit/304027206c883b61b76465b3c2a139927ea71344
DIFF: https://github.com/llvm/llvm-project/commit/304027206c883b61b76465b3c2a139927ea71344.diff
LOG: [ThinLTO] Support aliased GlobalIFunc
Fixes https://github.com/llvm/llvm-project/issues/56290: when an ifunc is
aliased in LTO, clang will attempt to create an alias summary; however, as ifunc
is not included in the module summary, doing so will lead to crash.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D129009
Added:
llvm/test/ThinLTO/X86/alias-ifunc.ll
Modified:
llvm/include/llvm/IR/GlobalIFunc.h
llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/lib/IR/Globals.cpp
llvm/lib/Transforms/IPO/FunctionImport.cpp
llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/GlobalIFunc.h b/llvm/include/llvm/IR/GlobalIFunc.h
index 976772b343fd9..c148ee7907789 100644
--- a/llvm/include/llvm/IR/GlobalIFunc.h
+++ b/llvm/include/llvm/IR/GlobalIFunc.h
@@ -93,6 +93,12 @@ class GlobalIFunc final : public GlobalObject, public ilist_node<GlobalIFunc> {
static bool classof(const Value *V) {
return V->getValueID() == Value::GlobalIFuncVal;
}
+
+ // Apply specific operation to all resolver-related values. If resolver target
+ // is already a global object, then apply the operation to it directly. If
+ // target is a GlobalExpr or a GlobalAlias, evaluate it to its base object and
+ // apply the operation for the base object and all aliases along the path.
+ void applyAlongResolverPath(function_ref<void(const GlobalValue &)> Op) const;
};
template <>
diff --git a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
index f364d890d95e6..c52b27a38fe9d 100644
--- a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
+++ b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -646,15 +646,18 @@ static void computeVariableSummary(ModuleSummaryIndex &Index,
Index.addGlobalValueSummary(V, std::move(GVarSummary));
}
-static void
-computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
- DenseSet<GlobalValue::GUID> &CantBePromoted) {
+static void computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
+ DenseSet<GlobalValue::GUID> &CantBePromoted) {
+ // Skip summary for indirect function aliases as summary for aliasee will not
+ // be emitted.
+ const GlobalObject *Aliasee = A.getAliaseeObject();
+ if (isa<GlobalIFunc>(Aliasee))
+ return;
bool NonRenamableLocal = isNonRenamableLocal(A);
GlobalValueSummary::GVFlags Flags(
A.getLinkage(), A.getVisibility(), NonRenamableLocal,
/* Live = */ false, A.isDSOLocal(), A.canBeOmittedFromSymbolTable());
auto AS = std::make_unique<AliasSummary>(Flags);
- auto *Aliasee = A.getAliaseeObject();
auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID());
assert(AliaseeVI && "Alias expects aliasee summary to be available");
assert(AliaseeVI.getSummaryList().size() == 1 &&
@@ -811,6 +814,13 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
for (const GlobalAlias &A : M.aliases())
computeAliasSummary(Index, A, CantBePromoted);
+ // Iterate through ifuncs, set their resolvers all alive.
+ for (const GlobalIFunc &I : M.ifuncs()) {
+ I.applyAlongResolverPath([&Index](const GlobalValue &GV) {
+ Index.getGlobalValueSummary(GV)->setLive(true);
+ });
+ }
+
for (auto *V : LocalsUsed) {
auto *Summary = Index.getGlobalValueSummary(*V);
assert(Summary && "Missing summary for global value");
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 590562ce27963..d7e012fb6a9ed 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -4104,8 +4104,9 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
for (const GlobalAlias &A : M.aliases()) {
auto *Aliasee = A.getAliaseeObject();
- if (!Aliasee->hasName())
- // Nameless function don't have an entry in the summary, skip it.
+ // Skip ifunc and nameless functions which don't have an entry in the
+ // summary.
+ if (!Aliasee->hasName() || isa<GlobalIFunc>(Aliasee))
continue;
auto AliasId = VE.getValueID(&A);
auto AliaseeId = VE.getValueID(Aliasee);
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 3265050261c83..51a22897babdb 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -316,32 +316,38 @@ bool GlobalObject::canIncreaseAlignment() const {
return true;
}
+template <typename Operation>
static const GlobalObject *
-findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases) {
- if (auto *GO = dyn_cast<GlobalObject>(C))
+findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases,
+ const Operation &Op) {
+ if (auto *GO = dyn_cast<GlobalObject>(C)) {
+ Op(*GO);
return GO;
- if (auto *GA = dyn_cast<GlobalAlias>(C))
+ }
+ if (auto *GA = dyn_cast<GlobalAlias>(C)) {
+ Op(*GA);
if (Aliases.insert(GA).second)
- return findBaseObject(GA->getOperand(0), Aliases);
+ return findBaseObject(GA->getOperand(0), Aliases, Op);
+ }
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
switch (CE->getOpcode()) {
case Instruction::Add: {
- auto *LHS = findBaseObject(CE->getOperand(0), Aliases);
- auto *RHS = findBaseObject(CE->getOperand(1), Aliases);
+ auto *LHS = findBaseObject(CE->getOperand(0), Aliases, Op);
+ auto *RHS = findBaseObject(CE->getOperand(1), Aliases, Op);
if (LHS && RHS)
return nullptr;
return LHS ? LHS : RHS;
}
case Instruction::Sub: {
- if (findBaseObject(CE->getOperand(1), Aliases))
+ if (findBaseObject(CE->getOperand(1), Aliases, Op))
return nullptr;
- return findBaseObject(CE->getOperand(0), Aliases);
+ return findBaseObject(CE->getOperand(0), Aliases, Op);
}
case Instruction::IntToPtr:
case Instruction::PtrToInt:
case Instruction::BitCast:
case Instruction::GetElementPtr:
- return findBaseObject(CE->getOperand(0), Aliases);
+ return findBaseObject(CE->getOperand(0), Aliases, Op);
default:
break;
}
@@ -351,7 +357,7 @@ findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases) {
const GlobalObject *GlobalValue::getAliaseeObject() const {
DenseSet<const GlobalAlias *> Aliases;
- return findBaseObject(this, Aliases);
+ return findBaseObject(this, Aliases, [](const GlobalValue &) {});
}
bool GlobalValue::isAbsoluteSymbolRef() const {
@@ -544,7 +550,7 @@ void GlobalAlias::setAliasee(Constant *Aliasee) {
const GlobalObject *GlobalAlias::getAliaseeObject() const {
DenseSet<const GlobalAlias *> Aliases;
- return findBaseObject(getOperand(0), Aliases);
+ return findBaseObject(getOperand(0), Aliases, [](const GlobalValue &) {});
}
//===----------------------------------------------------------------------===//
@@ -577,5 +583,12 @@ void GlobalIFunc::eraseFromParent() {
const Function *GlobalIFunc::getResolverFunction() const {
DenseSet<const GlobalAlias *> Aliases;
- return dyn_cast<Function>(findBaseObject(getResolver(), Aliases));
+ return dyn_cast<Function>(
+ findBaseObject(getResolver(), Aliases, [](const GlobalValue &) {}));
+}
+
+void GlobalIFunc::applyAlongResolverPath(
+ function_ref<void(const GlobalValue &)> Op) const {
+ DenseSet<const GlobalAlias *> Aliases;
+ findBaseObject(getResolver(), Aliases, Op);
}
diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index d83881b036097..360ec24a05093 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -1147,6 +1147,14 @@ void llvm::thinLTOInternalizeModule(Module &TheModule,
// Declare a callback for the internalize pass that will ask for every
// candidate GlobalValue if it can be internalized or not.
auto MustPreserveGV = [&](const GlobalValue &GV) -> bool {
+ // It may be the case that GV is on a chain of an ifunc, its alias and
+ // subsequent aliases. In this case, the summary for the value is not
+ // available.
+ if (isa<GlobalIFunc>(&GV) ||
+ (isa<GlobalAlias>(&GV) &&
+ isa<GlobalIFunc>(cast<GlobalAlias>(&GV)->getAliaseeObject())))
+ return true;
+
// Lookup the linkage recorded in the summaries during global analysis.
auto GS = DefinedGlobals.find(GV.getGUID());
if (GS == DefinedGlobals.end()) {
@@ -1277,7 +1285,7 @@ Expected<bool> FunctionImporter::importFunctions(
}
}
for (GlobalAlias &GA : SrcModule->aliases()) {
- if (!GA.hasName())
+ if (!GA.hasName() || isa<GlobalIFunc>(GA.getAliaseeObject()))
continue;
auto GUID = GA.getGUID();
auto Import = ImportGUIDs.count(GUID);
diff --git a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
index 193806d9cc877..8e6d4626c9fd2 100644
--- a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
+++ b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
@@ -35,6 +35,13 @@ bool FunctionImportGlobalProcessing::doImportAsDefinition(
bool FunctionImportGlobalProcessing::shouldPromoteLocalToGlobal(
const GlobalValue *SGV, ValueInfo VI) {
assert(SGV->hasLocalLinkage());
+
+ // Ifuncs and ifunc alias does not have summary.
+ if (isa<GlobalIFunc>(SGV) ||
+ (isa<GlobalAlias>(SGV) &&
+ isa<GlobalIFunc>(cast<GlobalAlias>(SGV)->getAliaseeObject())))
+ return false;
+
// Both the imported references and the original local variable must
// be promoted.
if (!isPerformingImport() && !isModuleExporting())
diff --git a/llvm/test/ThinLTO/X86/alias-ifunc.ll b/llvm/test/ThinLTO/X86/alias-ifunc.ll
new file mode 100644
index 0000000000000..3ec0466100daf
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/alias-ifunc.ll
@@ -0,0 +1,57 @@
+; RUN: opt -module-summary -o %t.bc %s
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-BAR
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-BAZ
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-QUX
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-RESOLVER
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-QUUX
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-CORGE
+; RUN: llvm-dis < %t.bc | FileCheck %s --check-prefix=CHECK-GRAULT
+; RUN: llvm-lto2 run %t.bc -r %t.bc,foo,px -r %t.bc,bar,px -r %t.bc,baz,px -r %t.bc,qux,px -r %t.bc,grault,px -o %t2
+; RUN: llvm-nm %t2.1 | FileCheck %s --check-prefix=CHECK-SYMBOL
+
+; CHECK-SYMBOL: i bar
+; CHECK-SYMBOL: i baz
+; CHECK-SYMBOL: i foo
+; CHECK-SYMBOL: t foo_resolver
+; CHECK-SYMBOL: i grault
+; CHECK-SYMBOL: i quuz
+; CHECK-SYMBOL: i qux
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+ at foo = ifunc i32 (i32), ptr @foo_resolver
+; CHECK-RESOLVER: (name: "foo_resolver"
+; CHECK-RESOLVER-SAME: live: 1
+define internal i32 (i32)* @foo_resolver() {
+entry:
+ ret i32 (i32)* null
+}
+; CHECK-BAR: (name: "bar"
+; CHECK-BAR-NOT: summaries: (
+; CHECK-BAR-SAME: ; guid = {{[0-9]+}}
+ at bar = alias i32 (i32), ptr @foo
+
+; CHECK-BAZ: (name: "baz"
+; CHECK-BAZ-NOT: summaries: (
+; CHECK-BAZ-SAME: ; guid = {{[0-9]+}}
+ at baz = weak alias i32 (i32), ptr @foo
+
+; CHECK-QUX: (name: "qux"
+; CHECK-QUX-NOT: summaries: (
+; CHECK-QUX-SAME: ; guid = {{[0-9]+}}
+ at qux = alias i32 (i32), ptr @bar
+
+; CHECK-QUUX: (name: "quux"
+; CHECK-QUUX-SAME: live: 1
+ at quux = internal alias i32 (i32)* (), ptr @foo_resolver
+ at quuz = internal ifunc i32 (i32), ptr @quux
+
+; CHECK-CORGE: (name: "corge"
+; CHECK-CORGE-NOT: summaries: (
+; CHECK-CORGE-SAME: ; guid = {{[0-9]+}}
+ at corge = internal alias i32 (i32), ptr @quuz
+
+; CHECK-GRAULT: (name: "grault"
+; CHECK-GRAULT-NOT: summaries: (
+; CHECK-GRAULT-SAME: ; guid = {{[0-9]+}}
+ at grault = alias i32 (i32), ptr @corge
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