[AIX] Implement the ifunc attribute.

clang/include/clang/Basic/TargetInfo.h

@@ -1547,6 +1547,9 @@ class TargetInfo : public TransferrableTargetInfo,
       return true;
     if (getTriple().getArch() == llvm::Triple::ArchType::avr)
       return true;
+    if (getTriple().isOSAIX())
+      return getTriple().getOSMajorVersion() == 0 ||
+             getTriple().getOSVersion() >= VersionTuple(7, 2);
     return getTriple().isOSBinFormatELF() &&
            ((getTriple().isOSLinux() && !getTriple().isMusl()) ||
             getTriple().isOSFreeBSD());

clang/lib/Driver/ToolChains/AIX.cpp

@@ -146,25 +146,10 @@ void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-bforceimprw");
   }
 
-  // PGO instrumentation generates symbols belonging to special sections, and
-  // the linker needs to place all symbols in a particular section together in
-  // memory; the AIX linker does that under an option.
-  if (Args.hasFlag(options::OPT_fprofile_arcs, options::OPT_fno_profile_arcs,
-                    false) ||
-       Args.hasFlag(options::OPT_fprofile_generate,
-                    options::OPT_fno_profile_generate, false) ||
-       Args.hasFlag(options::OPT_fprofile_generate_EQ,
-                    options::OPT_fno_profile_generate, false) ||
-       Args.hasFlag(options::OPT_fprofile_instr_generate,
-                    options::OPT_fno_profile_instr_generate, false) ||
-       Args.hasFlag(options::OPT_fprofile_instr_generate_EQ,
-                    options::OPT_fno_profile_instr_generate, false) ||
-       Args.hasFlag(options::OPT_fcs_profile_generate,
-                    options::OPT_fno_profile_generate, false) ||
-       Args.hasFlag(options::OPT_fcs_profile_generate_EQ,
-                    options::OPT_fno_profile_generate, false) ||
-       Args.hasArg(options::OPT_fcreate_profile) ||
-       Args.hasArg(options::OPT_coverage))
+  // PGO and ifunc support depends on the named sections linker feature that is
+  // available on AIX 7.2 TL5 SP5 onwards.
+  if (ToolChain.getTriple().getOSMajorVersion() == 0 ||
+      ToolChain.getTriple().getOSVersion() >= VersionTuple(7, 2))
     CmdArgs.push_back("-bdbg:namedsects:ss");
 
   if (Arg *A =

clang/test/CodeGen/attr-ifunc.c

@@ -4,6 +4,8 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx -verify -emit-llvm-only %s
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -verify -emit-llvm-only %s
 // RUN: %clang_cc1 -triple aarch64-pc-windows-msvcu -verify -emit-llvm-only %s
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -verify -emit-llvm-only %s
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -verify -emit-llvm-only -DCHECK_ALIASES %s
 
 #if defined(_WIN32) && !defined(__aarch64__)
 void foo(void) {}

clang/test/CodeGen/attr-ifunc.cpp

@@ -1,9 +1,11 @@
 // RUN: %clang_cc1 -triple x86_64-linux -verify -emit-llvm-only %s
 // RUN: %clang_cc1 -triple x86_64-apple-macosx -verify -emit-llvm-only %s
 // RUN: %clang_cc1 -triple arm64-apple-macosx -verify -emit-llvm-only %s
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -verify -emit-llvm-only %s
 // RUN: not %clang_cc1 -triple x86_64-linux -emit-llvm-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
 // RUN: not %clang_cc1 -triple x86_64-apple-macosx -emit-llvm-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
 // RUN: not %clang_cc1 -triple arm64-apple-macosx -emit-llvm-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+// RUN: not %clang_cc1 -triple powerpc64-ibm-aix-xcoff -emit-llvm-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
 
 void *f1_ifunc(void) { return nullptr; }
 void f1(void) __attribute__((ifunc("f1_ifunc")));

clang/test/CodeGen/ifunc.c

@@ -16,6 +16,8 @@
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -O2 -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -fsanitize=thread -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -fsanitize=address -O2 -emit-llvm -o - %s | FileCheck %s --check-prefix=SAN
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -O2 -emit-llvm -o - %s | FileCheck %s
 
 
 /// The ifunc is emitted before its resolver.
@@ -65,7 +67,7 @@ extern void hoo(int) __attribute__ ((ifunc("hoo_ifunc")));
 // AVR: @goo = ifunc void (), ptr addrspace(1) @goo_ifunc
 // AVR: @hoo = ifunc void (i16), ptr addrspace(1) @hoo_ifunc
 
-// CHECK: call i32 @foo(i32
+// CHECK: call {{(signext )?}}i32 @foo(i32
 // CHECK: call void @goo()
 
 // SAN: define {{(dso_local )?}}noalias {{(noundef )?}}ptr @goo_ifunc() #[[#GOO_IFUNC:]] {

clang/test/SemaCXX/ifunc-has-attribute.cpp

@@ -2,6 +2,7 @@
 // RUN: %clang_cc1 -emit-llvm-only -triple x86_64-apple-macosx -verify %s -DSUPPORTED=1
 // RUN: %clang_cc1 -emit-llvm-only -triple arm64-apple-macosx -verify %s -DSUPPORTED=1
 // RUN: %clang_cc1 -emit-llvm-only -triple x86_64-pc-win32 -verify %s -DNOT_SUPPORTED=1
+// RUN: %clang_cc1 -emit-llvm-only -triple powerpc64-ibm-aix-xcoff -verify %s -DSUPPORTED=1
 
 // expected-no-diagnostics
 

compiler-rt/lib/builtins/CMakeLists.txt

@@ -789,6 +789,16 @@ if (NOT OS_NAME MATCHES "AIX")
     ${powerpc64_SOURCES}
   )
 endif()
+if (OS_NAME MATCHES "AIX")
+  set(powerpc_SOURCES
+    ppc/init_ifuncs.c
+    ${powerpc_SOURCES}
+  )
+  set(powerpc64_SOURCES
+    ppc/init_ifuncs.c
+    ${powerpc64_SOURCES}
+  )
+endif()
 set(powerpc64le_SOURCES ${powerpc64_SOURCES})
 
 set(riscv_SOURCES

compiler-rt/lib/builtins/ppc/init_ifuncs.c

@@ -0,0 +1,38 @@
+typedef void *Ptr;
+typedef struct {
+  Ptr addr, toc, env;
+} Descr;
+typedef struct {
+  Descr *desc;
+  Ptr (*resolver)();
+} IFUNCPair;
+
+#define CONC2(A, B) A##B
+#define CONC(A, B) CONC2(A, B)
+
+#define IFUNC_SEC __ifunc_sec
+#define IFUNC_SEC_STR "__ifunc_sec"
+#define START_SEC CONC(__start_, IFUNC_SEC)
+#define STOP_SEC CONC(__stop_, IFUNC_SEC)
+
+// A zero-length entry in section "__ifunc_sec" to satisfy the START_SEC and
+// STOP_SEC references in this file,  when no user code has any ifuncs.
+__attribute__((section(IFUNC_SEC_STR))) static int dummy_ifunc_sec[0];
+
+extern IFUNCPair START_SEC, STOP_SEC;
+
+__attribute__((constructor)) void __init_ifuncs() {
+  void *volatile ref = &dummy_ifunc_sec; // hack to keep dummy_ifunc_sec alive
+
+  // hack to prevent compiler from assuming START_SEC and STOP_SEC
+  // occupy different addresses.
+  IFUNCPair *volatile volatile_end = &STOP_SEC;
+  for (IFUNCPair *pair = &START_SEC, *end = volatile_end; pair != end; pair++) {
+    // Call the resolver and copy the entire descriptor because:
+    //  - the resolved function might be in another DSO, so copy the TOC address
+    //  - we might be linking with objects from a language that uses the
+    //    enviroment pointer, so copy it too.
+    Descr *result = (Descr *)pair->resolver();
+    *(pair->desc) = *result;
+  }
+}

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -984,7 +984,7 @@ class LLVM_ABI AsmPrinter : public MachineFunctionPass {
   virtual void emitModuleCommandLines(Module &M);
 
   GCMetadataPrinter *getOrCreateGCPrinter(GCStrategy &S);
-  void emitGlobalIFunc(Module &M, const GlobalIFunc &GI);
+  virtual void emitGlobalIFunc(Module &M, const GlobalIFunc &GI);
 
   /// This method decides whether the specified basic block requires a label.
   bool shouldEmitLabelForBasicBlock(const MachineBasicBlock &MBB) const;

llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -289,7 +289,7 @@ class TargetLoweringObjectFileXCOFF : public TargetLoweringObjectFile {
   static XCOFF::StorageClass getStorageClassForGlobal(const GlobalValue *GV);
 
   MCSection *
-  getSectionForFunctionDescriptor(const Function *F,
+  getSectionForFunctionDescriptor(const GlobalObject *F,
                                   const TargetMachine &TM) const override;
   MCSection *getSectionForTOCEntry(const MCSymbol *Sym,
                                    const TargetMachine &TM) const override;

llvm/include/llvm/Target/TargetLoweringObjectFile.h

@@ -269,7 +269,7 @@ class LLVM_ABI TargetLoweringObjectFile : public MCObjectFileInfo {
   /// On targets that use separate function descriptor symbols, return a section
   /// for the descriptor given its symbol. Use only with defined functions.
   virtual MCSection *
-  getSectionForFunctionDescriptor(const Function *F,
+  getSectionForFunctionDescriptor(const GlobalObject *F,
                                   const TargetMachine &TM) const {
     return nullptr;
   }

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -2427,8 +2427,7 @@ void AsmPrinter::emitGlobalAlias(const Module &M, const GlobalAlias &GA) {
 
 void AsmPrinter::emitGlobalIFunc(Module &M, const GlobalIFunc &GI) {
   assert(!TM.getTargetTriple().isOSBinFormatXCOFF() &&
-         "IFunc is not supported on AIX.");
-
+         "AIX has non-default implementation.");
   auto EmitLinkage = [&](MCSymbol *Sym) {
     if (GI.hasExternalLinkage() || !MAI->getWeakRefDirective())
       OutStreamer->emitSymbolAttribute(Sym, MCSA_Global);

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -2391,7 +2391,9 @@ MCSymbol *
 TargetLoweringObjectFileXCOFF::getTargetSymbol(const GlobalValue *GV,
                                                const TargetMachine &TM) const {
   // We always use a qualname symbol for a GV that represents
-  // a declaration, a function descriptor, or a common symbol.
+  // a declaration, a function descriptor, or a common symbol. An IFunc is
+  // lowered as a special trampoline function which has an entry point and a
+  // descriptor.
   // If a GV represents a GlobalVariable and -fdata-sections is enabled, we
   // also return a qualname so that a label symbol could be avoided.
   // It is inherently ambiguous when the GO represents the address of a
@@ -2410,6 +2412,11 @@ TargetLoweringObjectFileXCOFF::getTargetSymbol(const GlobalValue *GV,
                    SectionForGlobal(GVar, SectionKind::getData(), TM))
             ->getQualNameSymbol();
 
+    if (isa<GlobalIFunc>(GO))
+      return static_cast<const MCSectionXCOFF *>(
+                 getSectionForFunctionDescriptor(GO, TM))
+          ->getQualNameSymbol();
+
     SectionKind GOKind = getKindForGlobal(GO, TM);
     if (GOKind.isText())
       return static_cast<const MCSectionXCOFF *>(
@@ -2682,7 +2689,7 @@ TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(const GlobalValue *GV) {
 
 MCSymbol *TargetLoweringObjectFileXCOFF::getFunctionEntryPointSymbol(
     const GlobalValue *Func, const TargetMachine &TM) const {
-  assert((isa<Function>(Func) ||
+  assert((isa<Function>(Func) || isa<GlobalIFunc>(Func) ||
           (isa<GlobalAlias>(Func) &&
            isa_and_nonnull<Function>(
                cast<GlobalAlias>(Func)->getAliaseeObject()))) &&
@@ -2699,7 +2706,7 @@ MCSymbol *TargetLoweringObjectFileXCOFF::getFunctionEntryPointSymbol(
   // undefined symbols gets treated as csect with XTY_ER property.
   if (((TM.getFunctionSections() && !Func->hasSection()) ||
        Func->isDeclarationForLinker()) &&
-      isa<Function>(Func)) {
+      (isa<Function>(Func) || isa<GlobalIFunc>(Func))) {
     return getContext()
         .getXCOFFSection(
             NameStr, SectionKind::getText(),
@@ -2713,7 +2720,9 @@ MCSymbol *TargetLoweringObjectFileXCOFF::getFunctionEntryPointSymbol(
 }
 
 MCSection *TargetLoweringObjectFileXCOFF::getSectionForFunctionDescriptor(
-    const Function *F, const TargetMachine &TM) const {
+    const GlobalObject *F, const TargetMachine &TM) const {
+  assert((isa<Function>(F) || isa<GlobalIFunc>(F)) &&
+         "F must be a function or ifunc object.");
   SmallString<128> NameStr;
   getNameWithPrefix(NameStr, F, TM);
   return getContext().getXCOFFSection(

llvm/lib/Target/PowerPC/CMakeLists.txt

@@ -41,6 +41,7 @@ add_llvm_target(PowerPCCodeGen
   PPCMachineScheduler.cpp
   PPCMacroFusion.cpp
   PPCMIPeephole.cpp
+  PPCPrepareIFuncsOnAIX.cpp
   PPCRegisterInfo.cpp
   PPCSelectionDAGInfo.cpp
   PPCSubtarget.cpp

llvm/lib/Target/PowerPC/PPC.h

@@ -53,6 +53,7 @@ class ModulePass;
   FunctionPass *createPPCPreEmitPeepholePass();
   FunctionPass *createPPCExpandAtomicPseudoPass();
   FunctionPass *createPPCCTRLoopsPass();
+  ModulePass *createPPCPrepareIFuncsOnAIXPass();
   void LowerPPCMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
                                     AsmPrinter &AP);
   bool LowerPPCMachineOperandToMCOperand(const MachineOperand &MO,
@@ -78,6 +79,7 @@ class ModulePass;
   void initializePPCExpandAtomicPseudoPass(PassRegistry &);
   void initializePPCCTRLoopsPass(PassRegistry &);
   void initializePPCDAGToDAGISelLegacyPass(PassRegistry &);
+  void initializePPCPrepareIFuncsOnAIXPass(PassRegistry &);
   void initializePPCLinuxAsmPrinterPass(PassRegistry &);
   void initializePPCAIXAsmPrinterPass(PassRegistry &);