PPC: allow for calling CFunctions without function descriptors on AIX.

The calling conventions on AIX uses function descriptors,
which means that pointers to functions do not point to code,
but instead point to metadata about them. When calling JITed code,
we must assure to use function descriptors instead of raw pointers when
needed. Before this CL 213504b9, all CallCFunction on AIX were guaranteed to have
function descriptors. Starting form the CL mentioned above, CallCFunction can also
Jump to a Trampoline which does not have a function descriptor, hence a new
"CallCFunctionWithoutFunctionDescriptor" method is proposed to deal with this issue.

BUG= v8:9766

Change-Id: I9343c31c812f5d4dda8503a5adf024b24dbde072
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1825961
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64357}

src/builtins/builtins-regexp-gen.cc

@@ -613,13 +613,18 @@ TNode<HeapObject> RegExpBuiltinsAssembler::RegExpExecInternal(
 
     TNode<RawPtrT> code_entry = LoadCodeObjectEntry(code);
 
-    TNode<Int32T> result = UncheckedCast<Int32T>(CallCFunction(
-        code_entry, retval_type, std::make_pair(arg0_type, arg0),
-        std::make_pair(arg1_type, arg1), std::make_pair(arg2_type, arg2),
-        std::make_pair(arg3_type, arg3), std::make_pair(arg4_type, arg4),
-        std::make_pair(arg5_type, arg5), std::make_pair(arg6_type, arg6),
-        std::make_pair(arg7_type, arg7), std::make_pair(arg8_type, arg8),
-        std::make_pair(arg9_type, arg9)));
+    // AIX uses function descriptors on CFunction calls. code_entry in this case
+    // may also point to a Regex interpreter entry trampoline which does not
+    // have a function descriptor. This method is ineffective on other platforms
+    // and is equivalent to CallCFunction.
+    TNode<Int32T> result =
+        UncheckedCast<Int32T>(CallCFunctionWithoutFunctionDescriptor(
+            code_entry, retval_type, std::make_pair(arg0_type, arg0),
+            std::make_pair(arg1_type, arg1), std::make_pair(arg2_type, arg2),
+            std::make_pair(arg3_type, arg3), std::make_pair(arg4_type, arg4),
+            std::make_pair(arg5_type, arg5), std::make_pair(arg6_type, arg6),
+            std::make_pair(arg7_type, arg7), std::make_pair(arg8_type, arg8),
+            std::make_pair(arg9_type, arg9)));
 
     // Check the result.
     // We expect exactly one result since we force the called regexp to behave

src/codegen/ppc/assembler-ppc.cc

@@ -1121,20 +1121,6 @@ void Assembler::divdu(Register dst, Register src1, Register src2, OEBit o,
 }
 #endif
 
-// Function descriptor for AIX.
-// Code address skips the function descriptor "header".
-// TOC and static chain are ignored and set to 0.
-void Assembler::function_descriptor() {
-  if (ABI_USES_FUNCTION_DESCRIPTORS) {
-    Label instructions;
-    DCHECK_EQ(pc_offset(), 0);
-    emit_label_addr(&instructions);
-    dp(0);
-    dp(0);
-    bind(&instructions);
-  }
-}
-
 int Assembler::instructions_required_for_mov(Register dst,
                                              const Operand& src) const {
   bool canOptimize =

src/codegen/ppc/assembler-ppc.h

@@ -840,8 +840,6 @@ class Assembler : public AssemblerBase {
   void mtfprwa(DoubleRegister dst, Register src);
 #endif
 
-  void function_descriptor();
-
   // Exception-generating instructions and debugging support
   void stop(Condition cond = al, int32_t code = kDefaultStopCode,
             CRegister cr = cr7);

src/codegen/ppc/constants-ppc.h

@@ -60,6 +60,12 @@ namespace internal {
 // TODO(sigurds): Change this value once we use relative jumps.
 constexpr size_t kMaxPCRelativeCodeRangeInMB = 0;
 
+// Used to encode a boolean value when emitting 32 bit
+// opcodes which will indicate the presence of function descriptors
+constexpr int kHasFunctionDescriptorBitShift = 9;
+constexpr int kHasFunctionDescriptorBitMask = 1
+                                              << kHasFunctionDescriptorBitShift;
+
 // Number of registers
 const int kNumRegisters = 32;
 

src/codegen/ppc/macro-assembler-ppc.cc

@@ -209,6 +209,12 @@ void TurboAssembler::Jump(const ExternalReference& reference) {
   UseScratchRegisterScope temps(this);
   Register scratch = temps.Acquire();
   Move(scratch, reference);
+  if (ABI_USES_FUNCTION_DESCRIPTORS) {
+    // AIX uses a function descriptor. When calling C code be
+    // aware of this descriptor and pick up values from it.
+    LoadP(ToRegister(ABI_TOC_REGISTER), MemOperand(scratch, kPointerSize));
+    LoadP(scratch, MemOperand(scratch, 0));
+  }
   Jump(scratch);
 }
 
@@ -1930,28 +1936,35 @@ void TurboAssembler::MovToFloatParameters(DoubleRegister src1,
 
 void TurboAssembler::CallCFunction(ExternalReference function,
                                    int num_reg_arguments,
-                                   int num_double_arguments) {
+                                   int num_double_arguments,
+                                   bool has_function_descriptor) {
   Move(ip, function);
-  CallCFunctionHelper(ip, num_reg_arguments, num_double_arguments);
+  CallCFunctionHelper(ip, num_reg_arguments, num_double_arguments,
+                      has_function_descriptor);
 }
 
 void TurboAssembler::CallCFunction(Register function, int num_reg_arguments,
-                                   int num_double_arguments) {
-  CallCFunctionHelper(function, num_reg_arguments, num_double_arguments);
+                                   int num_double_arguments,
+                                   bool has_function_descriptor) {
+  CallCFunctionHelper(function, num_reg_arguments, num_double_arguments,
+                      has_function_descriptor);
 }
 
 void TurboAssembler::CallCFunction(ExternalReference function,
-                                   int num_arguments) {
-  CallCFunction(function, num_arguments, 0);
+                                   int num_arguments,
+                                   bool has_function_descriptor) {
+  CallCFunction(function, num_arguments, 0, has_function_descriptor);
 }
 
-void TurboAssembler::CallCFunction(Register function, int num_arguments) {
-  CallCFunction(function, num_arguments, 0);
+void TurboAssembler::CallCFunction(Register function, int num_arguments,
+                                   bool has_function_descriptor) {
+  CallCFunction(function, num_arguments, 0, has_function_descriptor);
 }
 
 void TurboAssembler::CallCFunctionHelper(Register function,
                                          int num_reg_arguments,
-                                         int num_double_arguments) {
+                                         int num_double_arguments,
+                                         bool has_function_descriptor) {
   DCHECK_LE(num_reg_arguments + num_double_arguments, kMaxCParameters);
   DCHECK(has_frame());
 
@@ -1976,7 +1989,7 @@ void TurboAssembler::CallCFunctionHelper(Register function,
   // allow preemption, so the return address in the link register
   // stays correct.
   Register dest = function;
-  if (ABI_USES_FUNCTION_DESCRIPTORS) {
+  if (ABI_USES_FUNCTION_DESCRIPTORS && has_function_descriptor) {
     // AIX/PPC64BE Linux uses a function descriptor. When calling C code be
     // aware of this descriptor and pick up values from it
     LoadP(ToRegister(ABI_TOC_REGISTER), MemOperand(function, kPointerSize));

src/codegen/ppc/macro-assembler-ppc.h

@@ -350,12 +350,16 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   // garbage collection, since that might move the code and invalidate the
   // return address (unless this is somehow accounted for by the called
   // function).
-  void CallCFunction(ExternalReference function, int num_arguments);
-  void CallCFunction(Register function, int num_arguments);
+  void CallCFunction(ExternalReference function, int num_arguments,
+                     bool has_function_descriptor = kHasFunctionDescriptor);
+  void CallCFunction(Register function, int num_arguments,
+                     bool has_function_descriptor = kHasFunctionDescriptor);
   void CallCFunction(ExternalReference function, int num_reg_arguments,
-                     int num_double_arguments);
+                     int num_double_arguments,
+                     bool has_function_descriptor = kHasFunctionDescriptor);
   void CallCFunction(Register function, int num_reg_arguments,
-                     int num_double_arguments);
+                     int num_double_arguments,
+                     bool has_function_descriptor = kHasFunctionDescriptor);
 
   // Call a runtime routine. This expects {centry} to contain a fitting CEntry
   // builtin for the target runtime function and uses an indirect call.
@@ -642,7 +646,8 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   int CalculateStackPassedWords(int num_reg_arguments,
                                 int num_double_arguments);
   void CallCFunctionHelper(Register function, int num_reg_arguments,
-                           int num_double_arguments);
+                           int num_double_arguments,
+                           bool has_function_descriptor);
   void CallRecordWriteStub(Register object, Register address,
                            RememberedSetAction remembered_set_action,
                            SaveFPRegsMode fp_mode, Handle<Code> code_target,

src/common/globals.h

@@ -400,6 +400,7 @@ enum TypeofMode : int { INSIDE_TYPEOF, NOT_INSIDE_TYPEOF };
 // Enums used by CEntry.
 enum SaveFPRegsMode { kDontSaveFPRegs, kSaveFPRegs };
 enum ArgvMode { kArgvOnStack, kArgvInRegister };
+enum FunctionDescriptorMode { kNoFunctionDescriptor, kHasFunctionDescriptor };
 
 // This constant is used as an undefined value when passing source positions.
 constexpr int kNoSourcePosition = -1;

src/compiler/backend/instruction-selector.cc

@@ -2821,10 +2821,17 @@ void InstructionSelector::VisitCall(Node* node, BasicBlock* handler) {
   // Select the appropriate opcode based on the call type.
   InstructionCode opcode = kArchNop;
   switch (call_descriptor->kind()) {
-    case CallDescriptor::kCallAddress:
-      opcode = kArchCallCFunction | MiscField::encode(static_cast<int>(
-                                        call_descriptor->ParameterCount()));
+    case CallDescriptor::kCallAddress: {
+      int misc_field = static_cast<int>(call_descriptor->ParameterCount());
+#if defined(_AIX)
+      // Highest misc_field bit is used on AIX to indicate if a CFunction call
+      // has function descriptor or not.
+      misc_field |= call_descriptor->HasFunctionDescriptor()
+                    << kHasFunctionDescriptorBitShift;
+#endif
+      opcode = kArchCallCFunction | MiscField::encode(misc_field);
       break;
+    }
     case CallDescriptor::kCallCodeObject:
       opcode = kArchCallCodeObject | MiscField::encode(flags);
       break;

src/compiler/backend/instruction.h

@@ -807,7 +807,8 @@ class V8_EXPORT_PRIVATE Instruction final {
                           size_t output_count, InstructionOperand* outputs,
                           size_t input_count, InstructionOperand* inputs,
                           size_t temp_count, InstructionOperand* temps) {
-    DCHECK_LE(0, opcode);
+    // TODO(9872)
+    // DCHECK_LE(0, opcode);
     DCHECK(output_count == 0 || outputs != nullptr);
     DCHECK(input_count == 0 || inputs != nullptr);
     DCHECK(temp_count == 0 || temps != nullptr);

src/compiler/backend/ppc/code-generator-ppc.cc

@@ -1019,13 +1019,20 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
 #endif
       break;
     case kArchCallCFunction: {
-      int const num_parameters = MiscField::decode(instr->opcode());
+      int misc_field = MiscField::decode(instr->opcode());
+      int num_parameters = misc_field;
+      bool has_function_descriptor = false;
       Label start_call;
       bool isWasmCapiFunction =
           linkage()->GetIncomingDescriptor()->IsWasmCapiFunction();
 #if defined(_AIX)
       // AIX/PPC64BE Linux uses a function descriptor
-      // and emits 2 extra Load instrcutions under CallCFunctionHelper.
+      int kNumParametersMask = kHasFunctionDescriptorBitMask - 1;
+      num_parameters = kNumParametersMask & misc_field;
+      has_function_descriptor =
+          (misc_field & kHasFunctionDescriptorBitMask) != 0;
+      // AIX emits 2 extra Load instructions under CallCFunctionHelper
+      // due to having function descriptor.
       constexpr int offset = 11 * kInstrSize;
 #else
       constexpr int offset = 9 * kInstrSize;
@@ -1041,10 +1048,10 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       }
       if (instr->InputAt(0)->IsImmediate()) {
         ExternalReference ref = i.InputExternalReference(0);
-        __ CallCFunction(ref, num_parameters);
+        __ CallCFunction(ref, num_parameters, has_function_descriptor);
       } else {
         Register func = i.InputRegister(0);
-        __ CallCFunction(func, num_parameters);
+        __ CallCFunction(func, num_parameters, has_function_descriptor);
       }
       // TODO(miladfar): In the above block, kScratchReg must be populated with
       // the strictly-correct PC, which is the return address at this spot. The

src/compiler/code-assembler.cc

@@ -1439,6 +1439,13 @@ Node* CodeAssembler::CallCFunction(
   return raw_assembler()->CallCFunction(function, return_type, args);
 }
 
+Node* CodeAssembler::CallCFunctionWithoutFunctionDescriptor(
+    Node* function, MachineType return_type,
+    std::initializer_list<CodeAssembler::CFunctionArg> args) {
+  return raw_assembler()->CallCFunctionWithoutFunctionDescriptor(
+      function, return_type, args);
+}
+
 Node* CodeAssembler::CallCFunctionWithCallerSavedRegisters(
     Node* function, MachineType return_type, SaveFPRegsMode mode,
     std::initializer_list<CodeAssembler::CFunctionArg> args) {

src/compiler/code-assembler.h

@@ -1103,6 +1103,18 @@ class V8_EXPORT_PRIVATE CodeAssembler {
     return CallCFunction(function, return_type, {cargs...});
   }
 
+  // Call to a C function without a function discriptor on AIX.
+  template <class... CArgs>
+  Node* CallCFunctionWithoutFunctionDescriptor(Node* function,
+                                               MachineType return_type,
+                                               CArgs... cargs) {
+    static_assert(v8::internal::conjunction<
+                      std::is_convertible<CArgs, CFunctionArg>...>::value,
+                  "invalid argument types");
+    return CallCFunctionWithoutFunctionDescriptor(function, return_type,
+                                                  {cargs...});
+  }
+
   // Call to a C function, while saving/restoring caller registers.
   template <class... CArgs>
   Node* CallCFunctionWithCallerSavedRegisters(Node* function,
@@ -1151,6 +1163,10 @@ class V8_EXPORT_PRIVATE CodeAssembler {
   Node* CallCFunction(Node* function, MachineType return_type,
                       std::initializer_list<CFunctionArg> args);
 
+  Node* CallCFunctionWithoutFunctionDescriptor(
+      Node* function, MachineType return_type,
+      std::initializer_list<CFunctionArg> args);
+
   Node* CallCFunctionWithCallerSavedRegisters(
       Node* function, MachineType return_type, SaveFPRegsMode mode,
       std::initializer_list<CFunctionArg> args);

src/compiler/linkage.h

@@ -352,9 +352,18 @@ class V8_EXPORT_PRIVATE CallDescriptor final
 
   SaveFPRegsMode get_save_fp_mode() const { return save_fp_mode_; }
 
+  void set_has_function_descriptor(bool has_function_descriptor) {
+    has_function_descriptor_ = has_function_descriptor;
+  }
+
+  bool HasFunctionDescriptor() const { return has_function_descriptor_; }
+
  private:
   friend class Linkage;
   SaveFPRegsMode save_fp_mode_ = kSaveFPRegs;
+  // AIX has a function descriptor which we will set to true by default
+  // for all CFunction Calls.
+  bool has_function_descriptor_ = kHasFunctionDescriptor;
 
   const Kind kind_;
   const MachineType target_type_;

src/compiler/raw-machine-assembler.cc

@@ -705,7 +705,8 @@ namespace {
 Node* CallCFunctionImpl(
     RawMachineAssembler* rasm, Node* function, MachineType return_type,
     std::initializer_list<RawMachineAssembler::CFunctionArg> args,
-    bool caller_saved_regs, SaveFPRegsMode mode) {
+    bool caller_saved_regs, SaveFPRegsMode mode,
+    bool has_function_descriptor = kHasFunctionDescriptor) {
   static constexpr std::size_t kNumCArgs = 10;
 
   MachineSignature::Builder builder(rasm->zone(), 1, args.size());
@@ -719,6 +720,8 @@ Node* CallCFunctionImpl(
 
   if (caller_saved_regs) call_descriptor->set_save_fp_mode(mode);
 
+  call_descriptor->set_has_function_descriptor(has_function_descriptor);
+
   base::SmallVector<Node*, kNumCArgs> nodes(args.size() + 1);
   nodes[0] = function;
   std::transform(
@@ -739,6 +742,13 @@ Node* RawMachineAssembler::CallCFunction(
                            kDontSaveFPRegs);
 }
 
+Node* RawMachineAssembler::CallCFunctionWithoutFunctionDescriptor(
+    Node* function, MachineType return_type,
+    std::initializer_list<RawMachineAssembler::CFunctionArg> args) {
+  return CallCFunctionImpl(this, function, return_type, args, false,
+                           kDontSaveFPRegs, kNoFunctionDescriptor);
+}
+
 Node* RawMachineAssembler::CallCFunctionWithCallerSavedRegisters(
     Node* function, MachineType return_type, SaveFPRegsMode mode,
     std::initializer_list<RawMachineAssembler::CFunctionArg> args) {

src/compiler/raw-machine-assembler.h

@@ -983,6 +983,22 @@ class V8_EXPORT_PRIVATE RawMachineAssembler {
   Node* CallCFunction(Node* function, MachineType return_type,
                       std::initializer_list<CFunctionArg> args);
 
+  // Call to a C function without a function discriptor on AIX.
+  template <class... CArgs>
+  Node* CallCFunctionWithoutFunctionDescriptor(Node* function,
+                                               MachineType return_type,
+                                               CArgs... cargs) {
+    static_assert(v8::internal::conjunction<
+                      std::is_convertible<CArgs, CFunctionArg>...>::value,
+                  "invalid argument types");
+    return CallCFunctionWithoutFunctionDescriptor(function, return_type,
+                                                  {cargs...});
+  }
+
+  Node* CallCFunctionWithoutFunctionDescriptor(
+      Node* function, MachineType return_type,
+      std::initializer_list<CFunctionArg> args);
+
   // Call to a C function, while saving/restoring caller registers.
   template <class... CArgs>
   Node* CallCFunctionWithCallerSavedRegisters(Node* function,

src/execution/simulator.h

@@ -121,13 +121,6 @@ class GeneratedCode {
     return Simulator::current(isolate_)->template Call<Return>(
         reinterpret_cast<Address>(fn_ptr_), args...);
   }
-
-  DISABLE_CFI_ICALL Return CallIrregexp(Args... args) {
-#if defined(V8_TARGET_OS_WIN) && !defined(V8_OS_WIN)
-    FATAL("Generated code execution not possible during cross-compilation.");
-#endif  // defined(V8_TARGET_OS_WIN) && !defined(V8_OS_WIN)
-    return Call(args...);
-  }
 #else
 
   DISABLE_CFI_ICALL Return Call(Args... args) {
@@ -149,14 +142,6 @@ class GeneratedCode {
     return fn_ptr_(args...);
 #endif  // V8_OS_AIX
   }
-
-  DISABLE_CFI_ICALL Return CallIrregexp(Args... args) {
-    // When running without a simulator we call the entry directly.
-#if defined(V8_TARGET_OS_WIN) && !defined(V8_OS_WIN)
-    FATAL("Generated code execution not possible during cross-compilation.");
-#endif  // defined(V8_TARGET_OS_WIN) && !defined(V8_OS_WIN)
-    return fn_ptr_(args...);
-  }
 #endif  // USE_SIMULATOR
 
  private:

src/regexp/ppc/regexp-macro-assembler-ppc.cc

@@ -113,8 +113,6 @@ RegExpMacroAssemblerPPC::RegExpMacroAssemblerPPC(Isolate* isolate, Zone* zone,
       internal_failure_label_() {
   DCHECK_EQ(0, registers_to_save % 2);
 
-  // Because RegExp code respects C ABI, so needs a FD
-  __ function_descriptor();
 
   __ b(&entry_label_);  // We'll write the entry code later.
   // If the code gets too big or corrupted, an internal exception will be

src/regexp/regexp-macro-assembler.cc

@@ -289,9 +289,9 @@ int NativeRegExpMacroAssembler::Execute(
       Address regexp);
 
   auto fn = GeneratedCode<RegexpMatcherSig>::FromCode(code);
-  int result = fn.CallIrregexp(input.ptr(), start_offset, input_start,
-                               input_end, output, output_size, stack_base,
-                               call_origin, isolate, regexp.ptr());
+  int result =
+      fn.Call(input.ptr(), start_offset, input_start, input_end, output,
+              output_size, stack_base, call_origin, isolate, regexp.ptr());
   DCHECK(result >= RETRY);
 
   if (result == EXCEPTION && !isolate->has_pending_exception()) {