// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/globals.h"
#if defined(TARGET_ARCH_RISCV32) || defined(TARGET_ARCH_RISCV64)

#include "vm/runtime_entry.h"

#include "vm/simulator.h"
#include "vm/stub_code.h"

#if !defined(DART_PRECOMPILED_RUNTIME)
#include "vm/compiler/assembler/assembler.h"
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

namespace dart {

#define __ assembler->

uword RuntimeEntry::GetEntryPoint() const {
  // Compute the effective address. When running under the simulator,
  // this is a redirection address that forces the simulator to call
  // into the runtime system.
  uword entry = reinterpret_cast<uword>(function());
#if defined(USING_SIMULATOR)
  // Redirection to leaf runtime calls supports a maximum of 4 arguments passed
  // in registers (maximum 2 double arguments for leaf float runtime calls).
  ASSERT(argument_count() >= 0);
  ASSERT(!is_leaf() || (!is_float() && (argument_count() <= 4)) ||
         (argument_count() <= 2));
  Simulator::CallKind call_kind =
      is_leaf() ? (is_float() ? Simulator::kLeafFloatRuntimeCall
                              : Simulator::kLeafRuntimeCall)
                : Simulator::kRuntimeCall;
  entry =
      Simulator::RedirectExternalReference(entry, call_kind, argument_count());
#endif
  return entry;
}

#if !defined(DART_PRECOMPILED_RUNTIME)
// Generate code to call into the stub which will call the runtime
// function. Input for the stub is as follows:
//   SP : points to the arguments and return value array.
//   T5 : address of the runtime function to call.
//   T4 : number of arguments to the call.
void RuntimeEntry::CallInternal(const RuntimeEntry* runtime_entry,
                                compiler::Assembler* assembler,
                                intptr_t argument_count) {
  if (runtime_entry->is_leaf()) {
    ASSERT(argument_count == runtime_entry->argument_count());
    COMPILE_ASSERT(!IsAbiPreservedRegister(PP));
    // PP is a C volatile register.
    // SP will be aligned to the C stack alignment.
    __ mv(CALLEE_SAVED_TEMP, PP);
    __ mv(CALLEE_SAVED_TEMP2, SP);
    __ lx(TMP2,
          compiler::Address(THR, Thread::OffsetFromThread(runtime_entry)));
    __ sx(TMP2, compiler::Address(THR, Thread::vm_tag_offset()));
    __ ReserveAlignedFrameSpace(0);
    __ jalr(TMP2);
    __ LoadImmediate(TMP2, VMTag::kDartTagId);
    __ sx(TMP2, compiler::Address(THR, Thread::vm_tag_offset()));
    __ mv(PP, CALLEE_SAVED_TEMP);
    __ mv(SP, CALLEE_SAVED_TEMP2);
    // These registers must be preserved by runtime functions, otherwise
    // we'd need to restore them here.
    COMPILE_ASSERT(IsCalleeSavedRegister(THR));
    COMPILE_ASSERT(IsCalleeSavedRegister(NULL_REG));
    COMPILE_ASSERT(IsCalleeSavedRegister(WRITE_BARRIER_MASK));
    COMPILE_ASSERT(IsCalleeSavedRegister(DISPATCH_TABLE_REG));
  } else {
    // Argument count is not checked here, but in the runtime entry for a more
    // informative error message.
    __ lx(T5, compiler::Address(THR, Thread::OffsetFromThread(runtime_entry)));
    __ li(T4, argument_count);
    __ JumpAndLinkToRuntime();
  }
}
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

}  // namespace dart

#endif  // defined TARGET_ARCH_RISCV