DmitryPolukhin updated this revision to Diff 43775.
DmitryPolukhin marked 8 inline comments as done.
DmitryPolukhin added a comment.
Fixed comments.
http://reviews.llvm.org/D15524
Files:
include/clang/AST/DeclBase.h
include/clang/Basic/Attr.td
include/clang/Basic/AttrDocs.td
include/clang/Basic/DiagnosticSemaKinds.td
lib/AST/Decl.cpp
lib/AST/DeclBase.cpp
lib/CodeGen/CodeGenModule.cpp
lib/CodeGen/CodeGenModule.h
lib/Sema/SemaDecl.cpp
lib/Sema/SemaDeclAttr.cpp
test/CodeGen/ifunc.c
test/Sema/attr-alias-elf.c
test/Sema/attr-ifunc.c
Index: test/Sema/attr-ifunc.c
===================================================================
--- /dev/null
+++ test/Sema/attr-ifunc.c
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -triple x86_64-windows -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple x86_64-linux -fsyntax-only -verify -emit-llvm -DCHECK_ALIASES %s
+// RUN: %clang_cc1 -triple x86_64-linux -fsyntax-only -verify -emit-llvm %s
+
+#if defined(_WIN32)
+void foo() {}
+void bar() __attribute__((ifunc("foo")));
+//expected-warning@-1 {{'ifunc' attribute ignored}}
+
+#else
+#if defined(CHECK_ALIASES)
+void* f1_ifunc();
+void f1() __attribute__((ifunc("f1_ifunc")));
+//expected-error@-1 {{ifunc must point to a defined function}}
+
+void* f2_a() __attribute__((ifunc("f2_b")));
+//expected-error@-1 {{ifunc definition is part of a cycle}}
+void* f2_b() __attribute__((ifunc("f2_a")));
+//expected-error@-1 {{ifunc definition is part of a cycle}}
+
+void* f3_a() __attribute__((ifunc("f3_b")));
+//expected-warning@-1 {{ifunc will always resolve to f3_c even if weak definition of f3_b is overridden}}
+void* f3_b() __attribute__((weak, alias("f3_c")));
+void* f3_c() { return 0; }
+
+void f4_ifunc() {}
+void f4() __attribute__((ifunc("f4_ifunc")));
+//expected-error@-1 {{ifunc resolver function must return a pointer}}
+
+void* f5_ifunc(int i) { return 0; }
+void f5() __attribute__((ifunc("f5_ifunc")));
+//expected-error@-1 {{ifunc resolver function must have no parameters}}
+
+#else
+void f1a() __asm("f1");
+void f1a() {}
+//expected-note@-1 {{previous definition is here}}
+void f1() __attribute__((ifunc("f1_ifunc")));
+//expected-error@-1 {{definition with same mangled name as another definition}}
+void* f1_ifunc() { return 0; }
+
+#endif
+#endif
Index: test/Sema/attr-alias-elf.c
===================================================================
--- test/Sema/attr-alias-elf.c
+++ test/Sema/attr-alias-elf.c
@@ -55,7 +55,7 @@
void test2_bar() {}
void test2_foo() __attribute__((weak, alias("test2_bar")));
-void test2_zed() __attribute__((alias("test2_foo"))); // expected-warning {{alias will always resolve to test2_bar even if weak definition of alias test2_foo is overridden}}
+void test2_zed() __attribute__((alias("test2_foo"))); // expected-warning {{alias will always resolve to test2_bar even if weak definition of test2_foo is overridden}}
void test3_bar() { }
void test3_foo() __attribute__((section("test"))); // expected-warning {{alias will not be in section 'test' but in the same section as the aliasee}}
Index: test/CodeGen/ifunc.c
===================================================================
--- /dev/null
+++ test/CodeGen/ifunc.c
@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -O2 -emit-llvm -o - %s | FileCheck %s
+
+int foo(int) __attribute__ ((ifunc("foo_ifunc")));
+
+static int f1(int i) {
+ return i + 1;
+}
+
+static int f2(int i) {
+ return i + 2;
+}
+
+typedef int (*foo_t)(int);
+
+int global;
+
+static foo_t foo_ifunc() {
+ return global ? f1 : f2;
+}
+
+int bar() {
+ return foo(1);
+}
+
+extern void goo(void);
+
+void bar2(void) {
+ goo();
+}
+
+extern void goo(void) __attribute__ ((ifunc("goo_ifunc")));
+
+void* goo_ifunc(void) {
+ return 0;
+}
+// CHECK: @foo = ifunc i32 (i32), bitcast (i32 (i32)* ()* @foo_ifunc to i32 (i32)*)
+// CHECK: @goo = ifunc void (), bitcast (i8* ()* @goo_ifunc to void ()*)
+
+// CHECK: call i32 @foo(i32
+// CHECK: call void @goo()
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -1529,6 +1529,28 @@
Attr.getAttributeSpellingListIndex()));
}
+static void handleIFuncAttr(Sema &S, Decl *D, const AttributeList &Attr) {
+ StringRef Str;
+ if (!S.checkStringLiteralArgumentAttr(Attr, 0, Str))
+ return;
+
+ // Aliases should be on declarations, not definitions.
+ const auto *FD = cast<FunctionDecl>(D);
+ if (FD->isThisDeclarationADefinition()) {
+ S.Diag(Attr.getLoc(), diag::err_alias_is_definition) << FD << 1;
+ return;
+ }
+ // FIXME: it should be handled as a target specific attribute.
+ if (S.Context.getTargetInfo().getTriple().getObjectFormat() !=
+ llvm::Triple::ELF) {
+ S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << Attr.getName();
+ return;
+ }
+
+ D->addAttr(::new (S.Context) IFuncAttr(Attr.getRange(), S.Context, Str,
+ Attr.getAttributeSpellingListIndex()));
+}
+
static void handleAliasAttr(Sema &S, Decl *D, const AttributeList &Attr) {
StringRef Str;
if (!S.checkStringLiteralArgumentAttr(Attr, 0, Str))
@@ -1542,13 +1564,13 @@
// Aliases should be on declarations, not definitions.
if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
if (FD->isThisDeclarationADefinition()) {
- S.Diag(Attr.getLoc(), diag::err_alias_is_definition) << FD;
+ S.Diag(Attr.getLoc(), diag::err_alias_is_definition) << FD << 0;
return;
}
} else {
const auto *VD = cast<VarDecl>(D);
if (VD->isThisDeclarationADefinition() && VD->isExternallyVisible()) {
- S.Diag(Attr.getLoc(), diag::err_alias_is_definition) << VD;
+ S.Diag(Attr.getLoc(), diag::err_alias_is_definition) << VD << 0;
return;
}
}
@@ -4975,6 +4997,9 @@
case AttributeList::AT_IBOutletCollection:
handleIBOutletCollection(S, D, Attr);
break;
+ case AttributeList::AT_IFunc:
+ handleIFuncAttr(S, D, Attr);
+ break;
case AttributeList::AT_Alias:
handleAliasAttr(S, D, Attr);
break;
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -2297,7 +2297,7 @@
for (unsigned I = 0, E = NewAttributes.size(); I != E;) {
const Attr *NewAttribute = NewAttributes[I];
- if (isa<AliasAttr>(NewAttribute)) {
+ if (isa<AliasAttr>(NewAttribute) || isa<IFuncAttr>(NewAttribute)) {
if (FunctionDecl *FD = dyn_cast<FunctionDecl>(New)) {
Sema::SkipBodyInfo SkipBody;
S.CheckForFunctionRedefinition(FD, cast<FunctionDecl>(Def), &SkipBody);
@@ -5420,7 +5420,7 @@
if (const auto *Attr = VD->getAttr<AliasAttr>()) {
assert(VD->isThisDeclarationADefinition() &&
!VD->isExternallyVisible() && "Broken AliasAttr handled late!");
- S.Diag(Attr->getLocation(), diag::err_alias_is_definition) << VD;
+ S.Diag(Attr->getLocation(), diag::err_alias_is_definition) << VD << 0;
VD->dropAttr<AliasAttr>();
}
}
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -1148,6 +1148,7 @@
void EmitGlobalFunctionDefinition(GlobalDecl GD, llvm::GlobalValue *GV);
void EmitGlobalVarDefinition(const VarDecl *D);
void EmitAliasDefinition(GlobalDecl GD);
+ void emitIFuncDefinition(GlobalDecl GD);
void EmitObjCPropertyImplementations(const ObjCImplementationDecl *D);
void EmitObjCIvarInitializations(ObjCImplementationDecl *D);
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -259,20 +259,21 @@
// This is only used in aliases that we created and we know they have a
// linear structure.
-static const llvm::GlobalObject *getAliasedGlobal(const llvm::GlobalAlias &GA) {
- llvm::SmallPtrSet<const llvm::GlobalAlias*, 4> Visited;
- const llvm::Constant *C = &GA;
+static const llvm::GlobalObject *getAliasedGlobal(
+ const llvm::GlobalIndirectSymbol &GIS) {
+ llvm::SmallPtrSet<const llvm::GlobalIndirectSymbol*, 4> Visited;
+ const llvm::Constant *C = &GIS;
for (;;) {
C = C->stripPointerCasts();
if (auto *GO = dyn_cast<llvm::GlobalObject>(C))
return GO;
// stripPointerCasts will not walk over weak aliases.
- auto *GA2 = dyn_cast<llvm::GlobalAlias>(C);
- if (!GA2)
+ auto *GIS2 = dyn_cast<llvm::GlobalIndirectSymbol>(C);
+ if (!GIS2)
return nullptr;
- if (!Visited.insert(GA2).second)
+ if (!Visited.insert(GIS2).second)
return nullptr;
- C = GA2->getAliasee();
+ C = GIS2->getIndirectSymbol();
}
}
@@ -284,20 +285,35 @@
DiagnosticsEngine &Diags = getDiags();
for (const GlobalDecl &GD : Aliases) {
const auto *D = cast<ValueDecl>(GD.getDecl());
- const AliasAttr *AA = D->getAttr<AliasAttr>();
+ SourceLocation Location;
+ bool IsIFunc = D->hasAttr<IFuncAttr>();
+ if (const Attr *A = D->getDefiningAttr())
+ Location = A->getLocation();
+ else
+ llvm_unreachable("Not an alias or ifunc?");
StringRef MangledName = getMangledName(GD);
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
- auto *Alias = cast<llvm::GlobalAlias>(Entry);
+ auto *Alias = cast<llvm::GlobalIndirectSymbol>(Entry);
const llvm::GlobalValue *GV = getAliasedGlobal(*Alias);
if (!GV) {
Error = true;
- Diags.Report(AA->getLocation(), diag::err_cyclic_alias);
+ Diags.Report(Location, diag::err_cyclic_alias) << IsIFunc;
} else if (GV->isDeclaration()) {
Error = true;
- Diags.Report(AA->getLocation(), diag::err_alias_to_undefined);
+ Diags.Report(Location, diag::err_alias_to_undefined)
+ << IsIFunc << IsIFunc;
+ } else if (IsIFunc) {
+ // Check resolver function type.
+ llvm::FunctionType *FTy = dyn_cast<llvm::FunctionType>(
+ GV->getType()->getPointerElementType());
+ assert(FTy);
+ if (!FTy->getReturnType()->isPointerTy())
+ Diags.Report(Location, diag::err_ifunc_resolver_return);
+ if (FTy->getNumParams())
+ Diags.Report(Location, diag::err_ifunc_resolver_params);
}
- llvm::Constant *Aliasee = Alias->getAliasee();
+ llvm::Constant *Aliasee = Alias->getIndirectSymbol();
llvm::GlobalValue *AliaseeGV;
if (auto CE = dyn_cast<llvm::ConstantExpr>(Aliasee))
AliaseeGV = cast<llvm::GlobalValue>(CE->getOperand(0));
@@ -308,21 +324,21 @@
StringRef AliasSection = SA->getName();
if (AliasSection != AliaseeGV->getSection())
Diags.Report(SA->getLocation(), diag::warn_alias_with_section)
- << AliasSection;
+ << AliasSection << IsIFunc << IsIFunc;
}
// We have to handle alias to weak aliases in here. LLVM itself disallows
// this since the object semantics would not match the IL one. For
// compatibility with gcc we implement it by just pointing the alias
// to its aliasee's aliasee. We also warn, since the user is probably
// expecting the link to be weak.
- if (auto GA = dyn_cast<llvm::GlobalAlias>(AliaseeGV)) {
- if (GA->mayBeOverridden()) {
- Diags.Report(AA->getLocation(), diag::warn_alias_to_weak_alias)
- << GV->getName() << GA->getName();
+ if (auto GA = dyn_cast<llvm::GlobalIndirectSymbol>(AliaseeGV)) {
+ if (GA->mayBeOverridden() && GV) {
+ Diags.Report(Location, diag::warn_alias_to_weak_alias)
+ << GV->getName() << GA->getName() << IsIFunc;
Aliasee = llvm::ConstantExpr::getPointerBitCastOrAddrSpaceCast(
- GA->getAliasee(), Alias->getType());
- Alias->setAliasee(Aliasee);
+ GA->getIndirectSymbol(), Alias->getType());
+ Alias->setIndirectSymbol(Aliasee);
}
}
}
@@ -332,7 +348,7 @@
for (const GlobalDecl &GD : Aliases) {
StringRef MangledName = getMangledName(GD);
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
- auto *Alias = cast<llvm::GlobalAlias>(Entry);
+ auto *Alias = dyn_cast<llvm::GlobalIndirectSymbol>(Entry);
Alias->replaceAllUsesWith(llvm::UndefValue::get(Alias->getType()));
Alias->eraseFromParent();
}
@@ -1473,6 +1489,10 @@
if (Global->hasAttr<AliasAttr>())
return EmitAliasDefinition(GD);
+ // IFunc like an alias whose value is resolved at runtime by calling resolver.
+ if (Global->hasAttr<IFuncAttr>())
+ return emitIFuncDefinition(GD);
+
// If this is CUDA, be selective about which declarations we emit.
if (LangOpts.CUDA) {
if (LangOpts.CUDAIsDevice) {
@@ -2734,7 +2754,7 @@
StringRef MangledName = getMangledName(GD);
if (AA->getAliasee() == MangledName) {
- Diags.Report(AA->getLocation(), diag::err_cyclic_alias);
+ Diags.Report(AA->getLocation(), diag::err_cyclic_alias) << 0;
return;
}
@@ -2765,7 +2785,7 @@
if (Entry) {
if (GA->getAliasee() == Entry) {
- Diags.Report(AA->getLocation(), diag::err_cyclic_alias);
+ Diags.Report(AA->getLocation(), diag::err_cyclic_alias) << 0;
return;
}
@@ -2802,6 +2822,65 @@
setAliasAttributes(D, GA);
}
+void CodeGenModule::emitIFuncDefinition(GlobalDecl GD) {
+ const auto *D = cast<ValueDecl>(GD.getDecl());
+ const IFuncAttr *IFA = D->getAttr<IFuncAttr>();
+ assert(IFA && "Not an ifunc?");
+
+ StringRef MangledName = getMangledName(GD);
+
+ if (IFA->getResolver() == MangledName) {
+ Diags.Report(IFA->getLocation(), diag::err_cyclic_alias) << 1;
+ return;
+ }
+
+ // Report an error if some definition overrides ifunc.
+ llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
+ if (Entry && !Entry->isDeclaration()) {
+ GlobalDecl OtherGD;
+ if (lookupRepresentativeDecl(MangledName, OtherGD) &&
+ DiagnosedConflictingDefinitions.insert(GD).second) {
+ Diags.Report(D->getLocation(), diag::err_duplicate_mangled_name);
+ Diags.Report(OtherGD.getDecl()->getLocation(),
+ diag::note_previous_definition);
+ }
+ return;
+ }
+
+ Aliases.push_back(GD);
+
+ llvm::Type *DeclTy = getTypes().ConvertTypeForMem(D->getType());
+ llvm::Constant *Resolver =
+ GetOrCreateLLVMFunction(IFA->getResolver(), DeclTy, GD,
+ /*ForVTable=*/false);
+ llvm::GlobalIFunc *GIF =
+ llvm::GlobalIFunc::create(DeclTy, 0, llvm::Function::ExternalLinkage,
+ "", Resolver, &getModule());
+ if (Entry) {
+ if (GIF->getResolver() == Entry) {
+ Diags.Report(IFA->getLocation(), diag::err_cyclic_alias) << 1;
+ return;
+ }
+ assert(Entry->isDeclaration());
+
+ // If there is a declaration in the module, then we had an extern followed
+ // by the ifunc, as in:
+ // extern int test();
+ // ...
+ // int test() __attribute__((ifunc("resolver")));
+ //
+ // Remove it and replace uses of it with the ifunc.
+ GIF->takeName(Entry);
+
+ Entry->replaceAllUsesWith(llvm::ConstantExpr::getBitCast(GIF,
+ Entry->getType()));
+ Entry->eraseFromParent();
+ } else
+ GIF->setName(MangledName);
+
+ SetCommonAttributes(D, GIF);
+}
+
llvm::Function *CodeGenModule::getIntrinsic(unsigned IID,
ArrayRef<llvm::Type*> Tys) {
return llvm::Intrinsic::getDeclaration(&getModule(), (llvm::Intrinsic::ID)IID,
Index: lib/AST/DeclBase.cpp
===================================================================
--- lib/AST/DeclBase.cpp
+++ lib/AST/DeclBase.cpp
@@ -362,6 +362,18 @@
return false;
}
+bool Decl::hasDefiningAttr() const {
+ return hasAttr<AliasAttr>() || hasAttr<IFuncAttr>();
+}
+
+const Attr *Decl::getDefiningAttr() const {
+ if (AliasAttr *AA = getAttr<AliasAttr>())
+ return AA;
+ if (IFuncAttr *IFA = getAttr<IFuncAttr>())
+ return IFA;
+ return nullptr;
+}
+
/// \brief Determine the availability of the given declaration based on
/// the target platform.
///
Index: lib/AST/Decl.cpp
===================================================================
--- lib/AST/Decl.cpp
+++ lib/AST/Decl.cpp
@@ -1942,7 +1942,7 @@
if (hasInit())
return Definition;
- if (hasAttr<AliasAttr>())
+ if (hasDefiningAttr())
return Definition;
if (const auto *SAA = getAttr<SelectAnyAttr>())
@@ -2403,7 +2403,7 @@
bool FunctionDecl::isDefined(const FunctionDecl *&Definition) const {
for (auto I : redecls()) {
if (I->IsDeleted || I->IsDefaulted || I->Body || I->IsLateTemplateParsed ||
- I->hasAttr<AliasAttr>()) {
+ I->hasDefiningAttr()) {
Definition = I->IsDeleted ? I->getCanonicalDecl() : I;
return true;
}
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2409,17 +2409,21 @@
def err_alias_not_supported_on_darwin : Error <
"only weak aliases are supported on darwin">;
def err_alias_to_undefined : Error<
- "alias must point to a defined variable or function">;
+ "%select{alias|ifunc}0 must point to a defined %select{variable or |}1function">;
def warn_alias_to_weak_alias : Warning<
- "alias will always resolve to %0 even if weak definition of alias %1 is overridden">,
+ "%select{alias|ifunc}2 will always resolve to %0 even if weak definition of %1 is overridden">,
InGroup<IgnoredAttributes>;
def warn_alias_with_section : Warning<
- "alias will not be in section '%0' but in the same section as the aliasee">,
+ "%select{alias|ifunc}1 will not be in section '%0' but in the same section as the %select{aliasee|resolver}2">,
InGroup<IgnoredAttributes>;
def err_duplicate_mangled_name : Error<
"definition with same mangled name as another definition">;
def err_cyclic_alias : Error<
- "alias definition is part of a cycle">;
+ "%select{alias|ifunc}0 definition is part of a cycle">;
+def err_ifunc_resolver_return : Error<
+ "ifunc resolver function must return a pointer">;
+def err_ifunc_resolver_params : Error<
+ "ifunc resolver function must have no parameters">;
def warn_attribute_wrong_decl_type : Warning<
"%0 attribute only applies to %select{functions|unions|"
"variables and functions|functions and methods|parameters|"
@@ -4127,7 +4131,7 @@
def err_alias_after_tentative :
Error<"alias definition of %0 after tentative definition">;
def err_alias_is_definition :
- Error<"definition %0 cannot also be an alias">;
+ Error<"definition %0 cannot also be an %select{alias|ifunc}1">;
def err_definition_of_implicitly_declared_member : Error<
"definition of implicitly declared %select{default constructor|copy "
"constructor|move constructor|copy assignment operator|move assignment "
Index: include/clang/Basic/AttrDocs.td
===================================================================
--- include/clang/Basic/AttrDocs.td
+++ include/clang/Basic/AttrDocs.td
@@ -1859,3 +1859,17 @@
}];
}
+
+def IFuncDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+``__attribute__((ifunc("resolver")))`` is used to mark that the address of a declaration should be resolved at runtime by calling a resolver function.
+
+The symbol name of the resolver function is given in quotes. A function with this name (after mangling) must be defined in the current translation unit; it may be ``static``. The resolver function should take no arguments and return a pointer.
+
+The ``ifunc`` attribute may only be used on a function declaration. A function declaration with an ``ifunc`` attribute is considered to be a definition of the declared entity. The entity must not have weak linkage; for example, in C++, it cannot be applied to a declaration if a definition at that location would be considered inline.
+
+Not all targets support this attribute. ELF targets support this attribute when using binutils v2.20.1 or higher and glibc v2.11.1 or higher. Non-ELF targets currently do not support this attribute.
+ }];
+}
+
Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -818,6 +818,13 @@
let Documentation = [Undocumented];
}
+def IFunc : Attr {
+ let Spellings = [GCC<"ifunc">];
+ let Args = [StringArgument<"Resolver">];
+ let Subjects = SubjectList<[Function]>;
+ let Documentation = [IFuncDocs];
+}
+
def Restrict : InheritableAttr {
let Spellings = [Declspec<"restrict">, GCC<"malloc">];
let Subjects = SubjectList<[Function]>;
Index: include/clang/AST/DeclBase.h
===================================================================
--- include/clang/AST/DeclBase.h
+++ include/clang/AST/DeclBase.h
@@ -559,6 +559,13 @@
return NextInContextAndBits.getInt() & ModulePrivateFlag;
}
+ /// Return true if this declaration has an attribute which acts as
+ /// definition of the entity, such as 'alias' or 'ifunc'.
+ bool hasDefiningAttr() const;
+
+ /// Return this declaration's defining attribute if it has one.
+ const Attr *getDefiningAttr() const;
+
protected:
/// \brief Specify whether this declaration was marked as being private
/// to the module in which it was defined.
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