DmitryPolukhin created this revision.
DmitryPolukhin added reviewers: aaron.ballman, rjmccall.
DmitryPolukhin added a subscriber: cfe-commits.
This patch add support for GCC __attribute__((ifunc("resolver"))) for targets
that use ELF as object file format. In general ifunc is a special kind of
function alias with type @gnu_indirect_function. LLVM patch will be sent
separate.
http://reviews.llvm.org/D15524
Files:
include/clang/Basic/Attr.td
include/clang/Basic/AttrDocs.td
include/clang/Basic/DiagnosticSemaKinds.td
lib/AST/Decl.cpp
lib/CodeGen/CodeGenModule.cpp
lib/Sema/SemaDecl.cpp
lib/Sema/SemaDeclAttr.cpp
test/CodeGen/ifunc.c
test/Sema/attr-ifunc.c
Index: test/Sema/attr-ifunc.c
===================================================================
--- /dev/null
+++ test/Sema/attr-ifunc.c
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -triple x86_64-windows -fsyntax-only -verify %s
+
+void g() {}
+
+void f() __attribute__((ifunc("g")));
+//expected-warning@-1 {{'ifunc' attribute ignored}}
Index: test/CodeGen/ifunc.c
===================================================================
--- /dev/null
+++ test/CodeGen/ifunc.c
@@ -0,0 +1,27 @@
+// 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);
+
+extern int global;
+
+static foo_t foo_ifunc() {
+ return global ? f1 : f2;
+}
+
+int bar() {
+ return foo(1);
+}
+
+// CHECK: @foo = linkonce alias ifunc i32 (i32), bitcast (i32 (i32)* ()* @foo_ifunc to i32 (i32)*)
+// CHECK: call i32 @foo(i32
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -1529,6 +1529,29 @@
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.
+ if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
+ if (FD->isThisDeclarationADefinition()) {
+ S.Diag(Attr.getLoc(), diag::err_alias_is_definition) << FD << 1;
+ return;
+ }
+ if (S.Context.getTargetInfo().getTriple().getObjectFormat() !=
+ llvm::Triple::ELF) {
+ S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << Attr.getName();
+ return;
+ }
+ } else
+ llvm_unreachable("ifunc must be used for function declaration");
+
+ 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 +1565,13 @@
// 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 +4998,9 @@
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.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -283,17 +283,23 @@
DiagnosticsEngine &Diags = getDiags();
for (const GlobalDecl &GD : Aliases) {
const auto *D = cast<ValueDecl>(GD.getDecl());
- const AliasAttr *AA = D->getAttr<AliasAttr>();
+ SourceLocation Location;
+ if (const AliasAttr *AA = D->getAttr<AliasAttr>())
+ Location = AA->getLocation();
+ else if (const IFuncAttr *IFA = D->getAttr<IFuncAttr>())
+ Location = IFA->getLocation();
+ else
+ llvm_unreachable("Not an aliasi or ifunc?");
StringRef MangledName = getMangledName(GD);
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
auto *Alias = cast<llvm::GlobalAlias>(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);
} else if (GV->isDeclaration()) {
Error = true;
- Diags.Report(AA->getLocation(), diag::err_alias_to_undefined);
+ Diags.Report(Location, diag::err_alias_to_undefined);
}
llvm::Constant *Aliasee = Alias->getAliasee();
@@ -317,7 +323,7 @@
// 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)
+ Diags.Report(Location, diag::warn_alias_to_weak_alias)
<< GV->getName() << GA->getName();
Aliasee = llvm::ConstantExpr::getPointerBitCastOrAddrSpaceCast(
GA->getAliasee(), Alias->getType());
@@ -1414,8 +1420,8 @@
return;
// If this is an alias definition (which otherwise looks like a declaration)
- // emit it now.
- if (Global->hasAttr<AliasAttr>())
+ // emit it now. IFunc is an alias for function with special type.
+ if (Global->hasAttr<AliasAttr>() || Global->hasAttr<IFuncAttr>())
return EmitAliasDefinition(GD);
// If this is CUDA, be selective about which declarations we emit.
@@ -2668,13 +2674,21 @@
void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
const auto *D = cast<ValueDecl>(GD.getDecl());
- const AliasAttr *AA = D->getAttr<AliasAttr>();
- assert(AA && "Not an alias?");
+ StringRef AliaseeName;
+ SourceLocation Location;
+ if (const AliasAttr *AA = D->getAttr<AliasAttr>()) {
+ AliaseeName = AA->getAliasee();
+ Location = AA->getLocation();
+ } else if (const IFuncAttr *IFA = D->getAttr<IFuncAttr>()) {
+ AliaseeName = IFA->getResolver();
+ Location = IFA->getLocation();
+ } else
+ llvm_unreachable("Not an aliasi or ifunc?");
StringRef MangledName = getMangledName(GD);
- if (AA->getAliasee() == MangledName) {
- Diags.Report(AA->getLocation(), diag::err_cyclic_alias);
+ if (AliaseeName == MangledName) {
+ Diags.Report(Location, diag::err_cyclic_alias);
return;
}
@@ -2692,10 +2706,10 @@
// if a deferred decl.
llvm::Constant *Aliasee;
if (isa<llvm::FunctionType>(DeclTy))
- Aliasee = GetOrCreateLLVMFunction(AA->getAliasee(), DeclTy, GD,
+ Aliasee = GetOrCreateLLVMFunction(AliaseeName, DeclTy, GD,
/*ForVTable=*/false);
else
- Aliasee = GetOrCreateLLVMGlobal(AA->getAliasee(),
+ Aliasee = GetOrCreateLLVMGlobal(AliaseeName,
llvm::PointerType::getUnqual(DeclTy),
/*D=*/nullptr);
@@ -2705,7 +2719,7 @@
if (Entry) {
if (GA->getAliasee() == Entry) {
- Diags.Report(AA->getLocation(), diag::err_cyclic_alias);
+ Diags.Report(Location, diag::err_cyclic_alias);
return;
}
@@ -2739,6 +2753,11 @@
if (VD->getTLSKind())
setTLSMode(GA, *VD);
+ if (D->hasAttr<IFuncAttr>()) {
+ GA->setIFunc(true);
+ GA->setLinkage(llvm::GlobalValue::LinkOnceAnyLinkage);
+ }
+
setAliasAttributes(D, GA);
}
Index: lib/AST/Decl.cpp
===================================================================
--- lib/AST/Decl.cpp
+++ lib/AST/Decl.cpp
@@ -1940,7 +1940,7 @@
if (hasInit())
return Definition;
- if (hasAttr<AliasAttr>())
+ if (hasAttr<AliasAttr>() || hasAttr<IFuncAttr>())
return Definition;
if (const auto *SAA = getAttr<SelectAnyAttr>())
@@ -2401,7 +2401,7 @@
bool FunctionDecl::isDefined(const FunctionDecl *&Definition) const {
for (auto I : redecls()) {
if (I->IsDeleted || I->IsDefaulted || I->Body || I->IsLateTemplateParsed ||
- I->hasAttr<AliasAttr>()) {
+ I->hasAttr<AliasAttr>() || I->hasAttr<IFuncAttr>()) {
Definition = I->IsDeleted ? I->getCanonicalDecl() : I;
return true;
}
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -4127,7 +4127,7 @@
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 +1859,11 @@
}];
}
+
+def IFuncDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+The attribute ``__attribute__((ifunc("resolver")))`` is used to mark a function as an indirect function using the STT_GNU_IFUNC symbol type extension to the ELF standard. For more information, see GCC ifunc attribute documentation https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
+ }];
+}
+
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]>;
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