/*
   * This file is part of the MicroPython project, http://micropython.org/
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2013, 2014 Damien P. George
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  #include <stdint.h>
  #include <stdio.h>
  #include <assert.h>
  #include <string.h>
  
  #include "py/mpconfig.h"
  
  // wrapper around everything in this file
  #if MICROPY_EMIT_X64
  
  #include "py/asmx64.h"
  
  /* all offsets are measured in multiples of 8 bytes */
  #define WORD_SIZE                (8)
  
  #define OPCODE_NOP               (0x90)
  #define OPCODE_PUSH_R64          (0x50) /* +rq */
  #define OPCODE_PUSH_I64          (0x68)
  #define OPCODE_PUSH_M64          (0xff) /* /6 */
  #define OPCODE_POP_R64           (0x58) /* +rq */
  #define OPCODE_RET               (0xc3)
  #define OPCODE_MOV_I8_TO_R8      (0xb0) /* +rb */
  #define OPCODE_MOV_I64_TO_R64    (0xb8) /* +rq */
  #define OPCODE_MOV_I32_TO_RM32   (0xc7)
  #define OPCODE_MOV_R8_TO_RM8     (0x88) /* /r */
  #define OPCODE_MOV_R64_TO_RM64   (0x89) /* /r */
  #define OPCODE_MOV_RM64_TO_R64   (0x8b) /* /r */
  #define OPCODE_MOVZX_RM8_TO_R64  (0xb6) /* 0x0f 0xb6/r */
  #define OPCODE_MOVZX_RM16_TO_R64 (0xb7) /* 0x0f 0xb7/r */
  #define OPCODE_LEA_MEM_TO_R64    (0x8d) /* /r */
  #define OPCODE_AND_R64_TO_RM64   (0x21) /* /r */
  #define OPCODE_OR_R64_TO_RM64    (0x09) /* /r */
  #define OPCODE_XOR_R64_TO_RM64   (0x31) /* /r */
  #define OPCODE_ADD_R64_TO_RM64   (0x01) /* /r */
  #define OPCODE_ADD_I32_TO_RM32   (0x81) /* /0 */
  #define OPCODE_ADD_I8_TO_RM32    (0x83) /* /0 */
  #define OPCODE_SUB_R64_FROM_RM64 (0x29)
  #define OPCODE_SUB_I32_FROM_RM64 (0x81) /* /5 */
  #define OPCODE_SUB_I8_FROM_RM64  (0x83) /* /5 */
  //#define OPCODE_SHL_RM32_BY_I8    (0xc1) /* /4 */
  //#define OPCODE_SHR_RM32_BY_I8    (0xc1) /* /5 */
  //#define OPCODE_SAR_RM32_BY_I8    (0xc1) /* /7 */
  #define OPCODE_SHL_RM64_CL       (0xd3) /* /4 */
  #define OPCODE_SAR_RM64_CL       (0xd3) /* /7 */
  //#define OPCODE_CMP_I32_WITH_RM32 (0x81) /* /7 */
  //#define OPCODE_CMP_I8_WITH_RM32  (0x83) /* /7 */
  #define OPCODE_CMP_R64_WITH_RM64 (0x39) /* /r */
  //#define OPCODE_CMP_RM32_WITH_R32 (0x3b)
  #define OPCODE_TEST_R8_WITH_RM8  (0x84) /* /r */
  #define OPCODE_JMP_REL8          (0xeb)
  #define OPCODE_JMP_REL32         (0xe9)
  #define OPCODE_JCC_REL8          (0x70) /* | jcc type */
  #define OPCODE_JCC_REL32_A       (0x0f)
  #define OPCODE_JCC_REL32_B       (0x80) /* | jcc type */
  #define OPCODE_SETCC_RM8_A       (0x0f)
  #define OPCODE_SETCC_RM8_B       (0x90) /* | jcc type, /0 */
  #define OPCODE_CALL_REL32        (0xe8)
  #define OPCODE_CALL_RM32         (0xff) /* /2 */
  #define OPCODE_LEAVE             (0xc9)
  
  #define MODRM_R64(x)    (((x) & 0x7) << 3)
  #define MODRM_RM_DISP0  (0x00)
  #define MODRM_RM_DISP8  (0x40)
  #define MODRM_RM_DISP32 (0x80)
  #define MODRM_RM_REG    (0xc0)
  #define MODRM_RM_R64(x) ((x) & 0x7)
  
  #define OP_SIZE_PREFIX (0x66)
  
  #define REX_PREFIX  (0x40)
  #define REX_W       (0x08)  // width
  #define REX_R       (0x04)  // register
  #define REX_X       (0x02)  // index
  #define REX_B       (0x01)  // base
  #define REX_W_FROM_R64(r64) ((r64) >> 0 & 0x08)
  #define REX_R_FROM_R64(r64) ((r64) >> 1 & 0x04)
  #define REX_X_FROM_R64(r64) ((r64) >> 2 & 0x02)
  #define REX_B_FROM_R64(r64) ((r64) >> 3 & 0x01)
  
  #define IMM32_L0(x) ((x) & 0xff)
  #define IMM32_L1(x) (((x) >> 8) & 0xff)
  #define IMM32_L2(x) (((x) >> 16) & 0xff)
  #define IMM32_L3(x) (((x) >> 24) & 0xff)
  #define IMM64_L4(x) (((x) >> 32) & 0xff)
  #define IMM64_L5(x) (((x) >> 40) & 0xff)
  #define IMM64_L6(x) (((x) >> 48) & 0xff)
  #define IMM64_L7(x) (((x) >> 56) & 0xff)
  
  #define UNSIGNED_FIT8(x) (((x) & 0xffffffffffffff00) == 0)
  #define UNSIGNED_FIT32(x) (((x) & 0xffffffff00000000) == 0)
  #define SIGNED_FIT8(x) (((x) & 0xffffff80) == 0) || (((x) & 0xffffff80) == 0xffffff80)
  
  static inline byte *asm_x64_get_cur_to_write_bytes(asm_x64_t *as, int n) {
      return mp_asm_base_get_cur_to_write_bytes(&as->base, n);
  }
  
  STATIC void asm_x64_write_byte_1(asm_x64_t *as, byte b1) {
      byte* c = asm_x64_get_cur_to_write_bytes(as, 1);
      if (c != NULL) {
          c[0] = b1;
      }
  }
  
  STATIC void asm_x64_write_byte_2(asm_x64_t *as, byte b1, byte b2) {
      byte* c = asm_x64_get_cur_to_write_bytes(as, 2);
      if (c != NULL) {
          c[0] = b1;
          c[1] = b2;
      }
  }
  
  STATIC void asm_x64_write_byte_3(asm_x64_t *as, byte b1, byte b2, byte b3) {
      byte* c = asm_x64_get_cur_to_write_bytes(as, 3);
      if (c != NULL) {
          c[0] = b1;
          c[1] = b2;
          c[2] = b3;
      }
  }
  
  STATIC void asm_x64_write_word32(asm_x64_t *as, int w32) {
      byte* c = asm_x64_get_cur_to_write_bytes(as, 4);
      if (c != NULL) {
          c[0] = IMM32_L0(w32);
          c[1] = IMM32_L1(w32);
          c[2] = IMM32_L2(w32);
          c[3] = IMM32_L3(w32);
      }
  }
  
  STATIC void asm_x64_write_word64(asm_x64_t *as, int64_t w64) {
      byte* c = asm_x64_get_cur_to_write_bytes(as, 8);
      if (c != NULL) {
          c[0] = IMM32_L0(w64);
          c[1] = IMM32_L1(w64);
          c[2] = IMM32_L2(w64);
          c[3] = IMM32_L3(w64);
          c[4] = IMM64_L4(w64);
          c[5] = IMM64_L5(w64);
          c[6] = IMM64_L6(w64);
          c[7] = IMM64_L7(w64);
      }
  }
  
  /* unused
  STATIC void asm_x64_write_word32_to(asm_x64_t *as, int offset, int w32) {
      byte* c;
      assert(offset + 4 <= as->code_size);
      c = as->code_base + offset;
      c[0] = IMM32_L0(w32);
      c[1] = IMM32_L1(w32);
      c[2] = IMM32_L2(w32);
      c[3] = IMM32_L3(w32);
  }
  */
  
  STATIC void asm_x64_write_r64_disp(asm_x64_t *as, int r64, int disp_r64, int disp_offset) {
      assert(disp_r64 != ASM_X64_REG_RSP);
  
      if (disp_r64 == ASM_X64_REG_R12) {
          // special case for r12; not fully implemented
          assert(SIGNED_FIT8(disp_offset));
          asm_x64_write_byte_3(as, MODRM_R64(r64) | MODRM_RM_DISP8 | MODRM_RM_R64(disp_r64), 0x24, IMM32_L0(disp_offset));
          return;
      }
  
      if (disp_offset == 0 && disp_r64 != ASM_X64_REG_RBP) {
          asm_x64_write_byte_1(as, MODRM_R64(r64) | MODRM_RM_DISP0 | MODRM_RM_R64(disp_r64));
      } else if (SIGNED_FIT8(disp_offset)) {
          asm_x64_write_byte_2(as, MODRM_R64(r64) | MODRM_RM_DISP8 | MODRM_RM_R64(disp_r64), IMM32_L0(disp_offset));
      } else {
          asm_x64_write_byte_1(as, MODRM_R64(r64) | MODRM_RM_DISP32 | MODRM_RM_R64(disp_r64));
          asm_x64_write_word32(as, disp_offset);
      }
  }
  
  STATIC void asm_x64_generic_r64_r64(asm_x64_t *as, int dest_r64, int src_r64, int op) {
      asm_x64_write_byte_3(as, REX_PREFIX | REX_W | REX_R_FROM_R64(src_r64) | REX_B_FROM_R64(dest_r64), op, MODRM_R64(src_r64) | MODRM_RM_REG | MODRM_RM_R64(dest_r64));
  }
  
  void asm_x64_nop(asm_x64_t *as) {
      asm_x64_write_byte_1(as, OPCODE_NOP);
  }
  
  void asm_x64_push_r64(asm_x64_t *as, int src_r64) {
      if (src_r64 < 8) {
          asm_x64_write_byte_1(as, OPCODE_PUSH_R64 | src_r64);
      } else {
          asm_x64_write_byte_2(as, REX_PREFIX | REX_B, OPCODE_PUSH_R64 | (src_r64 & 7));
      }
  }
  
  /*
  void asm_x64_push_i32(asm_x64_t *as, int src_i32) {
      asm_x64_write_byte_1(as, OPCODE_PUSH_I64);
      asm_x64_write_word32(as, src_i32); // will be sign extended to 64 bits
  }
  */
  
  /*
  void asm_x64_push_disp(asm_x64_t *as, int src_r64, int src_offset) {
      assert(src_r64 < 8);
      asm_x64_write_byte_1(as, OPCODE_PUSH_M64);
      asm_x64_write_r64_disp(as, 6, src_r64, src_offset);
  }
  */
  
  void asm_x64_pop_r64(asm_x64_t *as, int dest_r64) {
      if (dest_r64 < 8) {
          asm_x64_write_byte_1(as, OPCODE_POP_R64 | dest_r64);
      } else {
          asm_x64_write_byte_2(as, REX_PREFIX | REX_B, OPCODE_POP_R64 | (dest_r64 & 7));
      }
  }
  
  STATIC void asm_x64_ret(asm_x64_t *as) {
      asm_x64_write_byte_1(as, OPCODE_RET);
  }
  
  void asm_x64_mov_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, src_r64, OPCODE_MOV_R64_TO_RM64);
  }
  
  void asm_x64_mov_r8_to_mem8(asm_x64_t *as, int src_r64, int dest_r64, int dest_disp) {
      if (src_r64 < 8 && dest_r64 < 8) {
          asm_x64_write_byte_1(as, OPCODE_MOV_R8_TO_RM8);
      } else {
          asm_x64_write_byte_2(as, REX_PREFIX | REX_R_FROM_R64(src_r64) | REX_B_FROM_R64(dest_r64), OPCODE_MOV_R8_TO_RM8);
      }
      asm_x64_write_r64_disp(as, src_r64, dest_r64, dest_disp);
  }
  
  void asm_x64_mov_r16_to_mem16(asm_x64_t *as, int src_r64, int dest_r64, int dest_disp) {
      if (src_r64 < 8 && dest_r64 < 8) {
          asm_x64_write_byte_2(as, OP_SIZE_PREFIX, OPCODE_MOV_R64_TO_RM64);
      } else {
          asm_x64_write_byte_3(as, OP_SIZE_PREFIX, REX_PREFIX | REX_R_FROM_R64(src_r64) | REX_B_FROM_R64(dest_r64), OPCODE_MOV_R64_TO_RM64);
      }
      asm_x64_write_r64_disp(as, src_r64, dest_r64, dest_disp);
  }
  
  void asm_x64_mov_r32_to_mem32(asm_x64_t *as, int src_r64, int dest_r64, int dest_disp) {
      if (src_r64 < 8 && dest_r64 < 8) {
          asm_x64_write_byte_1(as, OPCODE_MOV_R64_TO_RM64);
      } else {
          asm_x64_write_byte_2(as, REX_PREFIX | REX_R_FROM_R64(src_r64) | REX_B_FROM_R64(dest_r64), OPCODE_MOV_R64_TO_RM64);
      }
      asm_x64_write_r64_disp(as, src_r64, dest_r64, dest_disp);
  }
  
  void asm_x64_mov_r64_to_mem64(asm_x64_t *as, int src_r64, int dest_r64, int dest_disp) {
      // use REX prefix for 64 bit operation
      asm_x64_write_byte_2(as, REX_PREFIX | REX_W | REX_R_FROM_R64(src_r64) | REX_B_FROM_R64(dest_r64), OPCODE_MOV_R64_TO_RM64);
      asm_x64_write_r64_disp(as, src_r64, dest_r64, dest_disp);
  }
  
  void asm_x64_mov_mem8_to_r64zx(asm_x64_t *as, int src_r64, int src_disp, int dest_r64) {
      assert(src_r64 < 8);
      if (dest_r64 < 8) {
          asm_x64_write_byte_2(as, 0x0f, OPCODE_MOVZX_RM8_TO_R64);
      } else {
          asm_x64_write_byte_3(as, REX_PREFIX | REX_R, 0x0f, OPCODE_MOVZX_RM8_TO_R64);
      }
      asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
  }
  
  void asm_x64_mov_mem16_to_r64zx(asm_x64_t *as, int src_r64, int src_disp, int dest_r64) {
      assert(src_r64 < 8);
      if (dest_r64 < 8) {
          asm_x64_write_byte_2(as, 0x0f, OPCODE_MOVZX_RM16_TO_R64);
      } else {
          asm_x64_write_byte_3(as, REX_PREFIX | REX_R, 0x0f, OPCODE_MOVZX_RM16_TO_R64);
      }
      asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
  }
  
  void asm_x64_mov_mem32_to_r64zx(asm_x64_t *as, int src_r64, int src_disp, int dest_r64) {
      assert(src_r64 < 8);
      if (dest_r64 < 8) {
          asm_x64_write_byte_1(as, OPCODE_MOV_RM64_TO_R64);
      } else {
          asm_x64_write_byte_2(as, REX_PREFIX | REX_R, OPCODE_MOV_RM64_TO_R64);
      }
      asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
  }
  
  void asm_x64_mov_mem64_to_r64(asm_x64_t *as, int src_r64, int src_disp, int dest_r64) {
      // use REX prefix for 64 bit operation
      asm_x64_write_byte_2(as, REX_PREFIX | REX_W | REX_R_FROM_R64(dest_r64) | REX_B_FROM_R64(src_r64), OPCODE_MOV_RM64_TO_R64);
      asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
  }
  
  STATIC void asm_x64_lea_disp_to_r64(asm_x64_t *as, int src_r64, int src_disp, int dest_r64) {
      // use REX prefix for 64 bit operation
      assert(src_r64 < 8);
      assert(dest_r64 < 8);
      asm_x64_write_byte_2(as, REX_PREFIX | REX_W, OPCODE_LEA_MEM_TO_R64);
      asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
  }
  
  /*
  void asm_x64_mov_i8_to_r8(asm_x64_t *as, int src_i8, int dest_r64) {
      assert(dest_r64 < 8);
      asm_x64_write_byte_2(as, OPCODE_MOV_I8_TO_R8 | dest_r64, src_i8);
  }
  */
  
  STATIC void asm_x64_mov_i32_to_r64(asm_x64_t *as, int src_i32, int dest_r64) {
      // cpu defaults to i32 to r64, with zero extension
      if (dest_r64 < 8) {
          asm_x64_write_byte_1(as, OPCODE_MOV_I64_TO_R64 | dest_r64);
      } else {
          asm_x64_write_byte_2(as, REX_PREFIX | REX_B, OPCODE_MOV_I64_TO_R64 | (dest_r64 & 7));
      }
      asm_x64_write_word32(as, src_i32);
  }
  
  void asm_x64_mov_i64_to_r64(asm_x64_t *as, int64_t src_i64, int dest_r64) {
      // cpu defaults to i32 to r64
      // to mov i64 to r64 need to use REX prefix
      asm_x64_write_byte_2(as,
          REX_PREFIX | REX_W | (dest_r64 < 8 ? 0 : REX_B),
          OPCODE_MOV_I64_TO_R64 | (dest_r64 & 7));
      asm_x64_write_word64(as, src_i64);
  }
  
  void asm_x64_mov_i64_to_r64_optimised(asm_x64_t *as, int64_t src_i64, int dest_r64) {
      // TODO use movzx, movsx if possible
      if (UNSIGNED_FIT32(src_i64)) {
          // 5 bytes
          asm_x64_mov_i32_to_r64(as, src_i64 & 0xffffffff, dest_r64);
      } else {
          // 10 bytes
          asm_x64_mov_i64_to_r64(as, src_i64, dest_r64);
      }
  }
  
  // src_i64 is stored as a full word in the code, and aligned to machine-word boundary
  void asm_x64_mov_i64_to_r64_aligned(asm_x64_t *as, int64_t src_i64, int dest_r64) {
      // mov instruction uses 2 bytes for the instruction, before the i64
      while (((as->base.code_offset + 2) & (WORD_SIZE - 1)) != 0) {
          asm_x64_nop(as);
      }
      asm_x64_mov_i64_to_r64(as, src_i64, dest_r64);
  }
  
  void asm_x64_and_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, src_r64, OPCODE_AND_R64_TO_RM64);
  }
  
  void asm_x64_or_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, src_r64, OPCODE_OR_R64_TO_RM64);
  }
  
  void asm_x64_xor_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, src_r64, OPCODE_XOR_R64_TO_RM64);
  }
  
  void asm_x64_shl_r64_cl(asm_x64_t* as, int dest_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, 4, OPCODE_SHL_RM64_CL);
  }
  
  void asm_x64_sar_r64_cl(asm_x64_t* as, int dest_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, 7, OPCODE_SAR_RM64_CL);
  }
  
  void asm_x64_add_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, src_r64, OPCODE_ADD_R64_TO_RM64);
  }
  
  void asm_x64_sub_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      asm_x64_generic_r64_r64(as, dest_r64, src_r64, OPCODE_SUB_R64_FROM_RM64);
  }
  
  void asm_x64_mul_r64_r64(asm_x64_t *as, int dest_r64, int src_r64) {
      // imul reg64, reg/mem64 -- 0x0f 0xaf /r
      asm_x64_write_byte_1(as, REX_PREFIX | REX_W | REX_R_FROM_R64(dest_r64) | REX_B_FROM_R64(src_r64));
      asm_x64_write_byte_3(as, 0x0f, 0xaf, MODRM_R64(dest_r64) | MODRM_RM_REG | MODRM_RM_R64(src_r64));
  }
  
  /*
  void asm_x64_sub_i32_from_r32(asm_x64_t *as, int src_i32, int dest_r32) {
      if (SIGNED_FIT8(src_i32)) {
          // defaults to 32 bit operation
          asm_x64_write_byte_2(as, OPCODE_SUB_I8_FROM_RM64, MODRM_R64(5) | MODRM_RM_REG | MODRM_RM_R64(dest_r32));
          asm_x64_write_byte_1(as, src_i32 & 0xff);
      } else {
          // defaults to 32 bit operation
          asm_x64_write_byte_2(as, OPCODE_SUB_I32_FROM_RM64, MODRM_R64(5) | MODRM_RM_REG | MODRM_RM_R64(dest_r32));
          asm_x64_write_word32(as, src_i32);
      }
  }
  */
  
  STATIC void asm_x64_sub_r64_i32(asm_x64_t *as, int dest_r64, int src_i32) {
      assert(dest_r64 < 8);
      if (SIGNED_FIT8(src_i32)) {
          // use REX prefix for 64 bit operation
          asm_x64_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_SUB_I8_FROM_RM64, MODRM_R64(5) | MODRM_RM_REG | MODRM_RM_R64(dest_r64));
          asm_x64_write_byte_1(as, src_i32 & 0xff);
      } else {
          // use REX prefix for 64 bit operation
          asm_x64_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_SUB_I32_FROM_RM64, MODRM_R64(5) | MODRM_RM_REG | MODRM_RM_R64(dest_r64));
          asm_x64_write_word32(as, src_i32);
      }
  }
  
  /*
  void asm_x64_shl_r32_by_imm(asm_x64_t *as, int r32, int imm) {
      asm_x64_write_byte_2(as, OPCODE_SHL_RM32_BY_I8, MODRM_R64(4) | MODRM_RM_REG | MODRM_RM_R64(r32));
      asm_x64_write_byte_1(as, imm);
  }
  
  void asm_x64_shr_r32_by_imm(asm_x64_t *as, int r32, int imm) {
      asm_x64_write_byte_2(as, OPCODE_SHR_RM32_BY_I8, MODRM_R64(5) | MODRM_RM_REG | MODRM_RM_R64(r32));
      asm_x64_write_byte_1(as, imm);
  }
  
  void asm_x64_sar_r32_by_imm(asm_x64_t *as, int r32, int imm) {
      asm_x64_write_byte_2(as, OPCODE_SAR_RM32_BY_I8, MODRM_R64(7) | MODRM_RM_REG | MODRM_RM_R64(r32));
      asm_x64_write_byte_1(as, imm);
  }
  */
  
  void asm_x64_cmp_r64_with_r64(asm_x64_t *as, int src_r64_a, int src_r64_b) {
      asm_x64_generic_r64_r64(as, src_r64_b, src_r64_a, OPCODE_CMP_R64_WITH_RM64);
  }
  
  /*
  void asm_x64_cmp_i32_with_r32(asm_x64_t *as, int src_i32, int src_r32) {
      if (SIGNED_FIT8(src_i32)) {
          asm_x64_write_byte_2(as, OPCODE_CMP_I8_WITH_RM32, MODRM_R64(7) | MODRM_RM_REG | MODRM_RM_R64(src_r32));
          asm_x64_write_byte_1(as, src_i32 & 0xff);
      } else {
          asm_x64_write_byte_2(as, OPCODE_CMP_I32_WITH_RM32, MODRM_R64(7) | MODRM_RM_REG | MODRM_RM_R64(src_r32));
          asm_x64_write_word32(as, src_i32);
      }
  }
  */
  
  void asm_x64_test_r8_with_r8(asm_x64_t *as, int src_r64_a, int src_r64_b) {
      // TODO implement for other registers
      assert(src_r64_a == ASM_X64_REG_RAX);
      assert(src_r64_b == ASM_X64_REG_RAX);
      asm_x64_write_byte_2(as, OPCODE_TEST_R8_WITH_RM8, MODRM_R64(src_r64_a) | MODRM_RM_REG | MODRM_RM_R64(src_r64_b));
  }
  
  void asm_x64_setcc_r8(asm_x64_t *as, int jcc_type, int dest_r8) {
      assert(dest_r8 < 8);
      asm_x64_write_byte_3(as, OPCODE_SETCC_RM8_A, OPCODE_SETCC_RM8_B | jcc_type, MODRM_R64(0) | MODRM_RM_REG | MODRM_RM_R64(dest_r8));
  }
  
  STATIC mp_uint_t get_label_dest(asm_x64_t *as, mp_uint_t label) {
      assert(label < as->base.max_num_labels);
      return as->base.label_offsets[label];
  }
  
  void asm_x64_jmp_label(asm_x64_t *as, mp_uint_t label) {
      mp_uint_t dest = get_label_dest(as, label);
      mp_int_t rel = dest - as->base.code_offset;
      if (dest != (mp_uint_t)-1 && rel < 0) {
          // is a backwards jump, so we know the size of the jump on the first pass
          // calculate rel assuming 8 bit relative jump
          rel -= 2;
          if (SIGNED_FIT8(rel)) {
              asm_x64_write_byte_2(as, OPCODE_JMP_REL8, rel & 0xff);
          } else {
              rel += 2;
              goto large_jump;
          }
      } else {
          // is a forwards jump, so need to assume it's large
          large_jump:
          rel -= 5;
          asm_x64_write_byte_1(as, OPCODE_JMP_REL32);
          asm_x64_write_word32(as, rel);
      }
  }
  
  void asm_x64_jcc_label(asm_x64_t *as, int jcc_type, mp_uint_t label) {
      mp_uint_t dest = get_label_dest(as, label);
      mp_int_t rel = dest - as->base.code_offset;
      if (dest != (mp_uint_t)-1 && rel < 0) {
          // is a backwards jump, so we know the size of the jump on the first pass
          // calculate rel assuming 8 bit relative jump
          rel -= 2;
          if (SIGNED_FIT8(rel)) {
              asm_x64_write_byte_2(as, OPCODE_JCC_REL8 | jcc_type, rel & 0xff);
          } else {
              rel += 2;
              goto large_jump;
          }
      } else {
          // is a forwards jump, so need to assume it's large
          large_jump:
          rel -= 6;
          asm_x64_write_byte_2(as, OPCODE_JCC_REL32_A, OPCODE_JCC_REL32_B | jcc_type);
          asm_x64_write_word32(as, rel);
      }
  }
  
  void asm_x64_entry(asm_x64_t *as, int num_locals) {
      assert(num_locals >= 0);
      asm_x64_push_r64(as, ASM_X64_REG_RBP);
      asm_x64_mov_r64_r64(as, ASM_X64_REG_RBP, ASM_X64_REG_RSP);
      num_locals |= 1; // make it odd so stack is aligned on 16 byte boundary
      asm_x64_sub_r64_i32(as, ASM_X64_REG_RSP, num_locals * WORD_SIZE);
      asm_x64_push_r64(as, ASM_X64_REG_RBX);
      asm_x64_push_r64(as, ASM_X64_REG_R12);
      asm_x64_push_r64(as, ASM_X64_REG_R13);
      as->num_locals = num_locals;
  }
  
  void asm_x64_exit(asm_x64_t *as) {
      asm_x64_pop_r64(as, ASM_X64_REG_R13);
      asm_x64_pop_r64(as, ASM_X64_REG_R12);
      asm_x64_pop_r64(as, ASM_X64_REG_RBX);
      asm_x64_write_byte_1(as, OPCODE_LEAVE);
      asm_x64_ret(as);
  }
  
  // locals:
  //  - stored on the stack in ascending order
  //  - numbered 0 through as->num_locals-1
  //  - RBP points above the last local
  //
  //                          | RBP
  //                          v
  //  l0  l1  l2  ...  l(n-1)
  //  ^                ^
  //  | low address    | high address in RAM
  //
  STATIC int asm_x64_local_offset_from_ebp(asm_x64_t *as, int local_num) {
      return (-as->num_locals + local_num) * WORD_SIZE;
  }
  
  void asm_x64_mov_local_to_r64(asm_x64_t *as, int src_local_num, int dest_r64) {
      asm_x64_mov_mem64_to_r64(as, ASM_X64_REG_RBP, asm_x64_local_offset_from_ebp(as, src_local_num), dest_r64);
  }
  
  void asm_x64_mov_r64_to_local(asm_x64_t *as, int src_r64, int dest_local_num) {
      asm_x64_mov_r64_to_mem64(as, src_r64, ASM_X64_REG_RBP, asm_x64_local_offset_from_ebp(as, dest_local_num));
  }
  
  void asm_x64_mov_local_addr_to_r64(asm_x64_t *as, int local_num, int dest_r64) {
      int offset = asm_x64_local_offset_from_ebp(as, local_num);
      if (offset == 0) {
          asm_x64_mov_r64_r64(as, dest_r64, ASM_X64_REG_RBP);
      } else {
          asm_x64_lea_disp_to_r64(as, ASM_X64_REG_RBP, offset, dest_r64);
      }
  }
  
  /*
  void asm_x64_push_local(asm_x64_t *as, int local_num) {
      asm_x64_push_disp(as, ASM_X64_REG_RBP, asm_x64_local_offset_from_ebp(as, local_num));
  }
  
  void asm_x64_push_local_addr(asm_x64_t *as, int local_num, int temp_r64) {
      asm_x64_mov_r64_r64(as, temp_r64, ASM_X64_REG_RBP);
      asm_x64_add_i32_to_r32(as, asm_x64_local_offset_from_ebp(as, local_num), temp_r64);
      asm_x64_push_r64(as, temp_r64);
  }
  */
  
  /*
     can't use these because code might be relocated when resized
  
  void asm_x64_call(asm_x64_t *as, void* func) {
      asm_x64_sub_i32_from_r32(as, 8, ASM_X64_REG_RSP);
      asm_x64_write_byte_1(as, OPCODE_CALL_REL32);
      asm_x64_write_word32(as, func - (void*)(as->code_cur + 4));
      asm_x64_mov_r64_r64(as, ASM_X64_REG_RSP, ASM_X64_REG_RBP);
  }
  
  void asm_x64_call_i1(asm_x64_t *as, void* func, int i1) {
      asm_x64_sub_i32_from_r32(as, 8, ASM_X64_REG_RSP);
      asm_x64_sub_i32_from_r32(as, 12, ASM_X64_REG_RSP);
      asm_x64_push_i32(as, i1);
      asm_x64_write_byte_1(as, OPCODE_CALL_REL32);
      asm_x64_write_word32(as, func - (void*)(as->code_cur + 4));
      asm_x64_add_i32_to_r32(as, 16, ASM_X64_REG_RSP);
      asm_x64_mov_r64_r64(as, ASM_X64_REG_RSP, ASM_X64_REG_RBP);
  }
  */
  
  void asm_x64_call_ind(asm_x64_t *as, void *ptr, int temp_r64) {
      assert(temp_r64 < 8);
  #ifdef __LP64__
      asm_x64_mov_i64_to_r64_optimised(as, (int64_t)ptr, temp_r64);
  #else
      // If we get here, sizeof(int) == sizeof(void*).
      asm_x64_mov_i64_to_r64_optimised(as, (int64_t)(unsigned int)ptr, temp_r64);
  #endif
      asm_x64_write_byte_2(as, OPCODE_CALL_RM32, MODRM_R64(2) | MODRM_RM_REG | MODRM_RM_R64(temp_r64));
      // this reduces code size by 2 bytes per call, but doesn't seem to speed it up at all
      // doesn't work anymore because calls are 64 bits away
      /*
      asm_x64_write_byte_1(as, OPCODE_CALL_REL32);
      asm_x64_write_word32(as, ptr - (void*)(as->code_base + as->code_offset + 4));
      */
  }
  
  #endif // MICROPY_EMIT_X64