// Copyright 2019 The Marl Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#if defined(__powerpc64__)

#include "osfiber_asm_ppc64.h"

#include "marl/export.h"

MARL_EXPORT
void marl_fiber_trampoline(void (*target)(void*), void* arg) {
  target(arg);
}

MARL_EXPORT
void marl_fiber_set_target(struct marl_fiber_context* ctx,
                           void* stack,
                           uint32_t stack_size,
                           void (*target)(void*),
                           void* arg) {
  uintptr_t stack_top = (uintptr_t)((uint8_t*)(stack) + stack_size);
  if ((stack_top % 16) != 0) {
    stack_top -= (stack_top % 16);
  }

  // Write a backchain and subtract a minimum stack frame size (32)
  *(uintptr_t*)stack_top = 0;
  stack_top -= 32;
  *(uintptr_t*)stack_top = stack_top + 32;

  // Load registers
  ctx->r1 = stack_top;
  ctx->lr = (uintptr_t)marl_fiber_trampoline;
  ctx->r3 = (uintptr_t)target;
  ctx->r4 = (uintptr_t)arg;

  // Thread pointer must be saved in r13
  __asm__ volatile("mr %0, 13\n" : "=r"(ctx->r13));
}

#endif  // __powerpc64__