py/asmx86.c - lite/micropython - Linaro Git Browser

 /*
  * This file is part of the MicroPython project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
  * Copyright (c) 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_X86

 #include "py/asmx86.h"

 /* all offsets are measured in multiples of 4 bytes */
 #define WORD_SIZE                (4)

 #define OPCODE_NOP               (0x90)
 #define OPCODE_PUSH_R32          (0x50)
 // #define OPCODE_PUSH_I32          (0x68)
 // #define OPCODE_PUSH_M32          (0xff) /* /6 */
 #define OPCODE_POP_R32           (0x58)
 #define OPCODE_RET               (0xc3)
 // #define OPCODE_MOV_I8_TO_R8      (0xb0) /* +rb */
 #define OPCODE_MOV_I32_TO_R32    (0xb8)
 // #define OPCODE_MOV_I32_TO_RM32   (0xc7)
 #define OPCODE_MOV_R8_TO_RM8     (0x88) /* /r */
 #define OPCODE_MOV_R32_TO_RM32   (0x89) /* /r */
 #define OPCODE_MOV_RM32_TO_R32   (0x8b) /* /r */
 #define OPCODE_MOVZX_RM8_TO_R32  (0xb6) /* 0x0f 0xb6/r */
 #define OPCODE_MOVZX_RM16_TO_R32 (0xb7) /* 0x0f 0xb7/r */
 #define OPCODE_LEA_MEM_TO_R32    (0x8d) /* /r */
 #define OPCODE_AND_R32_TO_RM32   (0x21) /* /r */
 #define OPCODE_OR_R32_TO_RM32    (0x09) /* /r */
 #define OPCODE_XOR_R32_TO_RM32   (0x31) /* /r */
 #define OPCODE_ADD_R32_TO_RM32   (0x01)
 #define OPCODE_ADD_I32_TO_RM32   (0x81) /* /0 */
 #define OPCODE_ADD_I8_TO_RM32    (0x83) /* /0 */
 #define OPCODE_SUB_R32_FROM_RM32 (0x29)
 #define OPCODE_SUB_I32_FROM_RM32 (0x81) /* /5 */
 #define OPCODE_SUB_I8_FROM_RM32  (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_RM32_CL       (0xd3) /* /4 */
 #define OPCODE_SHR_RM32_CL       (0xd3) /* /5 */
 #define OPCODE_SAR_RM32_CL       (0xd3) /* /7 */
 // #define OPCODE_CMP_I32_WITH_RM32 (0x81) /* /7 */
 // #define OPCODE_CMP_I8_WITH_RM32  (0x83) /* /7 */
 #define OPCODE_CMP_R32_WITH_RM32 (0x39)
 // #define OPCODE_CMP_RM32_WITH_R32 (0x3b)
 #define OPCODE_TEST_R8_WITH_RM8  (0x84) /* /r */
 #define OPCODE_TEST_R32_WITH_RM32 (0x85) /* /r */
 #define OPCODE_JMP_REL8          (0xeb)
 #define OPCODE_JMP_REL32         (0xe9)
 #define OPCODE_JMP_RM32          (0xff) /* /4 */
 #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_R32(x)    ((x) << 3)
 #define MODRM_RM_DISP0  (0x00)
 #define MODRM_RM_DISP8  (0x40)
 #define MODRM_RM_DISP32 (0x80)
 #define MODRM_RM_REG    (0xc0)
 #define MODRM_RM_R32(x) (x)

 #define OP_SIZE_PREFIX (0x66)

 #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 SIGNED_FIT8(x) (((x) & 0xffffff80) == 0) || (((x) & 0xffffff80) == 0xffffff80)

 static void asm_x86_write_byte_1(asm_x86_t *as, byte b1) {
     byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 1);
     if (c != NULL) {
         c[0] = b1;
     }
 }

 static void asm_x86_write_byte_2(asm_x86_t *as, byte b1, byte b2) {
     byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 2);
     if (c != NULL) {
         c[0] = b1;
         c[1] = b2;
     }
 }

 static void asm_x86_write_byte_3(asm_x86_t *as, byte b1, byte b2, byte b3) {
     byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 3);
     if (c != NULL) {
         c[0] = b1;
         c[1] = b2;
         c[2] = b3;
     }
 }

 static void asm_x86_write_word32(asm_x86_t *as, int w32) {
     byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 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_x86_write_r32_disp(asm_x86_t *as, int r32, int disp_r32, int disp_offset) {
     uint8_t rm_disp;
     if (disp_offset == 0 && disp_r32 != ASM_X86_REG_EBP) {
         rm_disp = MODRM_RM_DISP0;
     } else if (SIGNED_FIT8(disp_offset)) {
         rm_disp = MODRM_RM_DISP8;
     } else {
         rm_disp = MODRM_RM_DISP32;
     }
     asm_x86_write_byte_1(as, MODRM_R32(r32) | rm_disp | MODRM_RM_R32(disp_r32));
     if (disp_r32 == ASM_X86_REG_ESP) {
         // Special case for esp, it needs a SIB byte
         asm_x86_write_byte_1(as, 0x24);
     }
     if (rm_disp == MODRM_RM_DISP8) {
         asm_x86_write_byte_1(as, IMM32_L0(disp_offset));
     } else if (rm_disp == MODRM_RM_DISP32) {
         asm_x86_write_word32(as, disp_offset);
     }
 }

 static void asm_x86_generic_r32_r32(asm_x86_t *as, int dest_r32, int src_r32, int op) {
     asm_x86_write_byte_2(as, op, MODRM_R32(src_r32) | MODRM_RM_REG | MODRM_RM_R32(dest_r32));
 }

 #if 0
 static void asm_x86_nop(asm_x86_t *as) {
     asm_x86_write_byte_1(as, OPCODE_NOP);
 }
 #endif

 static void asm_x86_push_r32(asm_x86_t *as, int src_r32) {
     asm_x86_write_byte_1(as, OPCODE_PUSH_R32 | src_r32);
 }

 #if 0
 void asm_x86_push_i32(asm_x86_t *as, int src_i32) {
     asm_x86_write_byte_1(as, OPCODE_PUSH_I32);
     asm_x86_write_word32(as, src_i32);
 }

 void asm_x86_push_disp(asm_x86_t *as, int src_r32, int src_offset) {
     asm_x86_write_byte_1(as, OPCODE_PUSH_M32);
     asm_x86_write_r32_disp(as, 6, src_r32, src_offset);
 }
 #endif

 static void asm_x86_pop_r32(asm_x86_t *as, int dest_r32) {
     asm_x86_write_byte_1(as, OPCODE_POP_R32 | dest_r32);
 }

 static void asm_x86_ret(asm_x86_t *as) {
     asm_x86_write_byte_1(as, OPCODE_RET);
 }

 void asm_x86_mov_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_MOV_R32_TO_RM32);
 }

 void asm_x86_mov_r8_to_mem8(asm_x86_t *as, int src_r32, int dest_r32, int dest_disp) {
     asm_x86_write_byte_1(as, OPCODE_MOV_R8_TO_RM8);
     asm_x86_write_r32_disp(as, src_r32, dest_r32, dest_disp);
 }

 void asm_x86_mov_r16_to_mem16(asm_x86_t *as, int src_r32, int dest_r32, int dest_disp) {
     asm_x86_write_byte_2(as, OP_SIZE_PREFIX, OPCODE_MOV_R32_TO_RM32);
     asm_x86_write_r32_disp(as, src_r32, dest_r32, dest_disp);
 }

 void asm_x86_mov_r32_to_mem32(asm_x86_t *as, int src_r32, int dest_r32, int dest_disp) {
     asm_x86_write_byte_1(as, OPCODE_MOV_R32_TO_RM32);
     asm_x86_write_r32_disp(as, src_r32, dest_r32, dest_disp);
 }

 void asm_x86_mov_mem8_to_r32zx(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
     asm_x86_write_byte_2(as, 0x0f, OPCODE_MOVZX_RM8_TO_R32);
     asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
 }

 void asm_x86_mov_mem16_to_r32zx(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
     asm_x86_write_byte_2(as, 0x0f, OPCODE_MOVZX_RM16_TO_R32);
     asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
 }

 void asm_x86_mov_mem32_to_r32(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
     asm_x86_write_byte_1(as, OPCODE_MOV_RM32_TO_R32);
     asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
 }

 static void asm_x86_lea_disp_to_r32(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
     asm_x86_write_byte_1(as, OPCODE_LEA_MEM_TO_R32);
     asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
 }

 #if 0
 void asm_x86_mov_i8_to_r8(asm_x86_t *as, int src_i8, int dest_r32) {
     asm_x86_write_byte_2(as, OPCODE_MOV_I8_TO_R8 | dest_r32, src_i8);
 }
 #endif

 size_t asm_x86_mov_i32_to_r32(asm_x86_t *as, int32_t src_i32, int dest_r32) {
     asm_x86_write_byte_1(as, OPCODE_MOV_I32_TO_R32 | dest_r32);
     size_t loc = mp_asm_base_get_code_pos(&as->base);
     asm_x86_write_word32(as, src_i32);
     return loc;
 }

 void asm_x86_and_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_AND_R32_TO_RM32);
 }

 void asm_x86_or_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_OR_R32_TO_RM32);
 }

 void asm_x86_xor_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_XOR_R32_TO_RM32);
 }

 void asm_x86_shl_r32_cl(asm_x86_t *as, int dest_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, 4, OPCODE_SHL_RM32_CL);
 }

 void asm_x86_shr_r32_cl(asm_x86_t *as, int dest_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, 5, OPCODE_SHR_RM32_CL);
 }

 void asm_x86_sar_r32_cl(asm_x86_t *as, int dest_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, 7, OPCODE_SAR_RM32_CL);
 }

 void asm_x86_add_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_ADD_R32_TO_RM32);
 }

 static void asm_x86_add_i32_to_r32(asm_x86_t *as, int src_i32, int dest_r32) {
     if (SIGNED_FIT8(src_i32)) {
         asm_x86_write_byte_2(as, OPCODE_ADD_I8_TO_RM32, MODRM_R32(0) | MODRM_RM_REG | MODRM_RM_R32(dest_r32));
         asm_x86_write_byte_1(as, src_i32 & 0xff);
     } else {
         asm_x86_write_byte_2(as, OPCODE_ADD_I32_TO_RM32, MODRM_R32(0) | MODRM_RM_REG | MODRM_RM_R32(dest_r32));
         asm_x86_write_word32(as, src_i32);
     }
 }

 void asm_x86_sub_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_SUB_R32_FROM_RM32);
 }

 static void asm_x86_sub_r32_i32(asm_x86_t *as, int dest_r32, int src_i32) {
     if (SIGNED_FIT8(src_i32)) {
         // defaults to 32 bit operation
         asm_x86_write_byte_2(as, OPCODE_SUB_I8_FROM_RM32, MODRM_R32(5) | MODRM_RM_REG | MODRM_RM_R32(dest_r32));
         asm_x86_write_byte_1(as, src_i32 & 0xff);
     } else {
         // defaults to 32 bit operation
         asm_x86_write_byte_2(as, OPCODE_SUB_I32_FROM_RM32, MODRM_R32(5) | MODRM_RM_REG | MODRM_RM_R32(dest_r32));
         asm_x86_write_word32(as, src_i32);
     }
 }

 void asm_x86_mul_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
     // imul reg32, reg/mem32 -- 0x0f 0xaf /r
     asm_x86_write_byte_3(as, 0x0f, 0xaf, MODRM_R32(dest_r32) | MODRM_RM_REG | MODRM_RM_R32(src_r32));
 }

 #if 0
 /* shifts not tested */
 void asm_x86_shl_r32_by_imm(asm_x86_t *as, int r32, int imm) {
     asm_x86_write_byte_2(as, OPCODE_SHL_RM32_BY_I8, MODRM_R32(4) | MODRM_RM_REG | MODRM_RM_R32(r32));
     asm_x86_write_byte_1(as, imm);
 }

 void asm_x86_shr_r32_by_imm(asm_x86_t *as, int r32, int imm) {
     asm_x86_write_byte_2(as, OPCODE_SHR_RM32_BY_I8, MODRM_R32(5) | MODRM_RM_REG | MODRM_RM_R32(r32));
     asm_x86_write_byte_1(as, imm);
 }

 void asm_x86_sar_r32_by_imm(asm_x86_t *as, int r32, int imm) {
     asm_x86_write_byte_2(as, OPCODE_SAR_RM32_BY_I8, MODRM_R32(7) | MODRM_RM_REG | MODRM_RM_R32(r32));
     asm_x86_write_byte_1(as, imm);
 }
 #endif

 void asm_x86_cmp_r32_with_r32(asm_x86_t *as, int src_r32_a, int src_r32_b) {
     asm_x86_generic_r32_r32(as, src_r32_b, src_r32_a, OPCODE_CMP_R32_WITH_RM32);
 }

 #if 0
 void asm_x86_cmp_i32_with_r32(asm_x86_t *as, int src_i32, int src_r32) {
     if (SIGNED_FIT8(src_i32)) {
         asm_x86_write_byte_2(as, OPCODE_CMP_I8_WITH_RM32, MODRM_R32(7) | MODRM_RM_REG | MODRM_RM_R32(src_r32));
         asm_x86_write_byte_1(as, src_i32 & 0xff);
     } else {
         asm_x86_write_byte_2(as, OPCODE_CMP_I32_WITH_RM32, MODRM_R32(7) | MODRM_RM_REG | MODRM_RM_R32(src_r32));
         asm_x86_write_word32(as, src_i32);
     }
 }
 #endif

 void asm_x86_test_r8_with_r8(asm_x86_t *as, int src_r32_a, int src_r32_b) {
     asm_x86_write_byte_2(as, OPCODE_TEST_R8_WITH_RM8, MODRM_R32(src_r32_a) | MODRM_RM_REG | MODRM_RM_R32(src_r32_b));
 }

 void asm_x86_test_r32_with_r32(asm_x86_t *as, int src_r32_a, int src_r32_b) {
     asm_x86_generic_r32_r32(as, src_r32_b, src_r32_a, OPCODE_TEST_R32_WITH_RM32);
 }

 void asm_x86_setcc_r8(asm_x86_t *as, mp_uint_t jcc_type, int dest_r8) {
     asm_x86_write_byte_3(as, OPCODE_SETCC_RM8_A, OPCODE_SETCC_RM8_B | jcc_type, MODRM_R32(0) | MODRM_RM_REG | MODRM_RM_R32(dest_r8));
 }

 void asm_x86_jmp_reg(asm_x86_t *as, int src_r32) {
     asm_x86_write_byte_2(as, OPCODE_JMP_RM32, MODRM_R32(4) | MODRM_RM_REG | MODRM_RM_R32(src_r32));
 }

 static mp_uint_t get_label_dest(asm_x86_t *as, mp_uint_t label) {
     assert(label < as->base.max_num_labels);
     return as->base.label_offsets[label];
 }

 void asm_x86_jmp_label(asm_x86_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_x86_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_x86_write_byte_1(as, OPCODE_JMP_REL32);
         asm_x86_write_word32(as, rel);
     }
 }

 void asm_x86_jcc_label(asm_x86_t *as, mp_uint_t 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_x86_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_x86_write_byte_2(as, OPCODE_JCC_REL32_A, OPCODE_JCC_REL32_B | jcc_type);
         asm_x86_write_word32(as, rel);
     }
 }

 void asm_x86_entry(asm_x86_t *as, int num_locals) {
     assert(num_locals >= 0);
     asm_x86_push_r32(as, ASM_X86_REG_EBP);
     asm_x86_push_r32(as, ASM_X86_REG_EBX);
     asm_x86_push_r32(as, ASM_X86_REG_ESI);
     asm_x86_push_r32(as, ASM_X86_REG_EDI);
     num_locals |= 3; // make it odd so stack is aligned on 16 byte boundary
     asm_x86_sub_r32_i32(as, ASM_X86_REG_ESP, num_locals * WORD_SIZE);
     as->num_locals = num_locals;
 }

 void asm_x86_exit(asm_x86_t *as) {
     asm_x86_sub_r32_i32(as, ASM_X86_REG_ESP, -as->num_locals * WORD_SIZE);
     asm_x86_pop_r32(as, ASM_X86_REG_EDI);
     asm_x86_pop_r32(as, ASM_X86_REG_ESI);
     asm_x86_pop_r32(as, ASM_X86_REG_EBX);
     asm_x86_pop_r32(as, ASM_X86_REG_EBP);
     asm_x86_ret(as);
 }

 static int asm_x86_arg_offset_from_esp(asm_x86_t *as, size_t arg_num) {
     // Above esp are: locals, 4 saved registers, return eip, arguments
     return (as->num_locals + 4 + 1 + arg_num) * WORD_SIZE;
 }

 #if 0
 void asm_x86_push_arg(asm_x86_t *as, int src_arg_num) {
     asm_x86_push_disp(as, ASM_X86_REG_ESP, asm_x86_arg_offset_from_esp(as, src_arg_num));
 }
 #endif

 void asm_x86_mov_arg_to_r32(asm_x86_t *as, int src_arg_num, int dest_r32) {
     asm_x86_mov_mem32_to_r32(as, ASM_X86_REG_ESP, asm_x86_arg_offset_from_esp(as, src_arg_num), dest_r32);
 }

 #if 0
 void asm_x86_mov_r32_to_arg(asm_x86_t *as, int src_r32, int dest_arg_num) {
     asm_x86_mov_r32_to_mem32(as, src_r32, ASM_X86_REG_ESP, asm_x86_arg_offset_from_esp(as, dest_arg_num));
 }
 #endif

 // locals:
 //  - stored on the stack in ascending order
 //  - numbered 0 through as->num_locals-1
 //  - ESP points to the first local
 //
 //  | ESP
 //  v
 //  l0  l1  l2  ...  l(n-1)
 //  ^                ^
 //  | low address    | high address in RAM
 //
 static int asm_x86_local_offset_from_esp(asm_x86_t *as, int local_num) {
     (void)as;
     // Stack is full descending, ESP points to local0
     return local_num * WORD_SIZE;
 }

 void asm_x86_mov_local_to_r32(asm_x86_t *as, int src_local_num, int dest_r32) {
     asm_x86_mov_mem32_to_r32(as, ASM_X86_REG_ESP, asm_x86_local_offset_from_esp(as, src_local_num), dest_r32);
 }

 void asm_x86_mov_r32_to_local(asm_x86_t *as, int src_r32, int dest_local_num) {
     asm_x86_mov_r32_to_mem32(as, src_r32, ASM_X86_REG_ESP, asm_x86_local_offset_from_esp(as, dest_local_num));
 }

 void asm_x86_mov_local_addr_to_r32(asm_x86_t *as, int local_num, int dest_r32) {
     int offset = asm_x86_local_offset_from_esp(as, local_num);
     if (offset == 0) {
         asm_x86_mov_r32_r32(as, dest_r32, ASM_X86_REG_ESP);
     } else {
         asm_x86_lea_disp_to_r32(as, ASM_X86_REG_ESP, offset, dest_r32);
     }
 }

 void asm_x86_mov_reg_pcrel(asm_x86_t *as, int dest_r32, mp_uint_t label) {
     asm_x86_write_byte_1(as, OPCODE_CALL_REL32);
     asm_x86_write_word32(as, 0);
     mp_uint_t dest = get_label_dest(as, label);
     mp_int_t rel = dest - as->base.code_offset;
     asm_x86_pop_r32(as, dest_r32);
     // PC rel is usually a forward reference, so need to assume it's large
     asm_x86_write_byte_2(as, OPCODE_ADD_I32_TO_RM32, MODRM_R32(0) | MODRM_RM_REG | MODRM_RM_R32(dest_r32));
     asm_x86_write_word32(as, rel);
 }

 #if 0
 void asm_x86_push_local(asm_x86_t *as, int local_num) {
     asm_x86_push_disp(as, ASM_X86_REG_ESP, asm_x86_local_offset_from_esp(as, local_num));
 }

 void asm_x86_push_local_addr(asm_x86_t *as, int local_num, int temp_r32) {
     asm_x86_mov_r32_r32(as, temp_r32, ASM_X86_REG_ESP);
     asm_x86_add_i32_to_r32(as, asm_x86_local_offset_from_esp(as, local_num), temp_r32);
     asm_x86_push_r32(as, temp_r32);
 }
 #endif

 void asm_x86_call_ind(asm_x86_t *as, size_t fun_id, mp_uint_t n_args, int temp_r32) {
     assert(n_args <= 4);

     // Align stack on 16-byte boundary during the call
     unsigned int align = ((n_args + 3) & ~3) - n_args;
     if (align) {
         asm_x86_sub_r32_i32(as, ASM_X86_REG_ESP, align * WORD_SIZE);
     }

     if (n_args > 3) {
         asm_x86_push_r32(as, ASM_X86_REG_ARG_4);
     }
     if (n_args > 2) {
         asm_x86_push_r32(as, ASM_X86_REG_ARG_3);
     }
     if (n_args > 1) {
         asm_x86_push_r32(as, ASM_X86_REG_ARG_2);
     }
     if (n_args > 0) {
         asm_x86_push_r32(as, ASM_X86_REG_ARG_1);
     }

     // Load the pointer to the function and make the call
     asm_x86_mov_mem32_to_r32(as, ASM_X86_REG_FUN_TABLE, fun_id * WORD_SIZE, temp_r32);
     asm_x86_write_byte_2(as, OPCODE_CALL_RM32, MODRM_R32(2) | MODRM_RM_REG | MODRM_RM_R32(temp_r32));

     // the caller must clean up the stack
     if (n_args > 0) {
         asm_x86_add_i32_to_r32(as, (n_args + align) * WORD_SIZE, ASM_X86_REG_ESP);
     }
 }

 #endif // MICROPY_EMIT_X86
	/*
	* This file is part of the MicroPython project, http://micropython.org/
	*
	* The MIT License (MIT)
	*
	* Copyright (c) 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_X86

	#include "py/asmx86.h"

	/* all offsets are measured in multiples of 4 bytes */
	#define WORD_SIZE (4)

	#define OPCODE_NOP (0x90)
	#define OPCODE_PUSH_R32 (0x50)
	// #define OPCODE_PUSH_I32 (0x68)
	// #define OPCODE_PUSH_M32 (0xff) /* /6 */
	#define OPCODE_POP_R32 (0x58)
	#define OPCODE_RET (0xc3)
	// #define OPCODE_MOV_I8_TO_R8 (0xb0) /* +rb */
	#define OPCODE_MOV_I32_TO_R32 (0xb8)
	// #define OPCODE_MOV_I32_TO_RM32 (0xc7)
	#define OPCODE_MOV_R8_TO_RM8 (0x88) /* /r */
	#define OPCODE_MOV_R32_TO_RM32 (0x89) /* /r */
	#define OPCODE_MOV_RM32_TO_R32 (0x8b) /* /r */
	#define OPCODE_MOVZX_RM8_TO_R32 (0xb6) /* 0x0f 0xb6/r */
	#define OPCODE_MOVZX_RM16_TO_R32 (0xb7) /* 0x0f 0xb7/r */
	#define OPCODE_LEA_MEM_TO_R32 (0x8d) /* /r */
	#define OPCODE_AND_R32_TO_RM32 (0x21) /* /r */
	#define OPCODE_OR_R32_TO_RM32 (0x09) /* /r */
	#define OPCODE_XOR_R32_TO_RM32 (0x31) /* /r */
	#define OPCODE_ADD_R32_TO_RM32 (0x01)
	#define OPCODE_ADD_I32_TO_RM32 (0x81) /* /0 */
	#define OPCODE_ADD_I8_TO_RM32 (0x83) /* /0 */
	#define OPCODE_SUB_R32_FROM_RM32 (0x29)
	#define OPCODE_SUB_I32_FROM_RM32 (0x81) /* /5 */
	#define OPCODE_SUB_I8_FROM_RM32 (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_RM32_CL (0xd3) /* /4 */
	#define OPCODE_SHR_RM32_CL (0xd3) /* /5 */
	#define OPCODE_SAR_RM32_CL (0xd3) /* /7 */
	// #define OPCODE_CMP_I32_WITH_RM32 (0x81) /* /7 */
	// #define OPCODE_CMP_I8_WITH_RM32 (0x83) /* /7 */
	#define OPCODE_CMP_R32_WITH_RM32 (0x39)
	// #define OPCODE_CMP_RM32_WITH_R32 (0x3b)
	#define OPCODE_TEST_R8_WITH_RM8 (0x84) /* /r */
	#define OPCODE_TEST_R32_WITH_RM32 (0x85) /* /r */
	#define OPCODE_JMP_REL8 (0xeb)
	#define OPCODE_JMP_REL32 (0xe9)
	#define OPCODE_JMP_RM32 (0xff) /* /4 */
	#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_R32(x) ((x) << 3)
	#define MODRM_RM_DISP0 (0x00)
	#define MODRM_RM_DISP8 (0x40)
	#define MODRM_RM_DISP32 (0x80)
	#define MODRM_RM_REG (0xc0)
	#define MODRM_RM_R32(x) (x)

	#define OP_SIZE_PREFIX (0x66)

	#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 SIGNED_FIT8(x) (((x) & 0xffffff80) == 0) \|\| (((x) & 0xffffff80) == 0xffffff80)

	static void asm_x86_write_byte_1(asm_x86_t *as, byte b1) {
	byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 1);
	if (c != NULL) {
	c[0] = b1;
	}
	}

	static void asm_x86_write_byte_2(asm_x86_t *as, byte b1, byte b2) {
	byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 2);
	if (c != NULL) {
	c[0] = b1;
	c[1] = b2;
	}
	}

	static void asm_x86_write_byte_3(asm_x86_t *as, byte b1, byte b2, byte b3) {
	byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 3);
	if (c != NULL) {
	c[0] = b1;
	c[1] = b2;
	c[2] = b3;
	}
	}

	static void asm_x86_write_word32(asm_x86_t *as, int w32) {
	byte *c = mp_asm_base_get_cur_to_write_bytes(&as->base, 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_x86_write_r32_disp(asm_x86_t *as, int r32, int disp_r32, int disp_offset) {
	uint8_t rm_disp;
	if (disp_offset == 0 && disp_r32 != ASM_X86_REG_EBP) {
	rm_disp = MODRM_RM_DISP0;
	} else if (SIGNED_FIT8(disp_offset)) {
	rm_disp = MODRM_RM_DISP8;
	} else {
	rm_disp = MODRM_RM_DISP32;
	}
	asm_x86_write_byte_1(as, MODRM_R32(r32) \| rm_disp \| MODRM_RM_R32(disp_r32));
	if (disp_r32 == ASM_X86_REG_ESP) {
	// Special case for esp, it needs a SIB byte
	asm_x86_write_byte_1(as, 0x24);
	}
	if (rm_disp == MODRM_RM_DISP8) {
	asm_x86_write_byte_1(as, IMM32_L0(disp_offset));
	} else if (rm_disp == MODRM_RM_DISP32) {
	asm_x86_write_word32(as, disp_offset);
	}
	}

	static void asm_x86_generic_r32_r32(asm_x86_t *as, int dest_r32, int src_r32, int op) {
	asm_x86_write_byte_2(as, op, MODRM_R32(src_r32) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r32));
	}

	#if 0
	static void asm_x86_nop(asm_x86_t *as) {
	asm_x86_write_byte_1(as, OPCODE_NOP);
	}
	#endif

	static void asm_x86_push_r32(asm_x86_t *as, int src_r32) {
	asm_x86_write_byte_1(as, OPCODE_PUSH_R32 \| src_r32);
	}

	#if 0
	void asm_x86_push_i32(asm_x86_t *as, int src_i32) {
	asm_x86_write_byte_1(as, OPCODE_PUSH_I32);
	asm_x86_write_word32(as, src_i32);
	}

	void asm_x86_push_disp(asm_x86_t *as, int src_r32, int src_offset) {
	asm_x86_write_byte_1(as, OPCODE_PUSH_M32);
	asm_x86_write_r32_disp(as, 6, src_r32, src_offset);
	}
	#endif

	static void asm_x86_pop_r32(asm_x86_t *as, int dest_r32) {
	asm_x86_write_byte_1(as, OPCODE_POP_R32 \| dest_r32);
	}

	static void asm_x86_ret(asm_x86_t *as) {
	asm_x86_write_byte_1(as, OPCODE_RET);
	}

	void asm_x86_mov_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_MOV_R32_TO_RM32);
	}

	void asm_x86_mov_r8_to_mem8(asm_x86_t *as, int src_r32, int dest_r32, int dest_disp) {
	asm_x86_write_byte_1(as, OPCODE_MOV_R8_TO_RM8);
	asm_x86_write_r32_disp(as, src_r32, dest_r32, dest_disp);
	}

	void asm_x86_mov_r16_to_mem16(asm_x86_t *as, int src_r32, int dest_r32, int dest_disp) {
	asm_x86_write_byte_2(as, OP_SIZE_PREFIX, OPCODE_MOV_R32_TO_RM32);
	asm_x86_write_r32_disp(as, src_r32, dest_r32, dest_disp);
	}

	void asm_x86_mov_r32_to_mem32(asm_x86_t *as, int src_r32, int dest_r32, int dest_disp) {
	asm_x86_write_byte_1(as, OPCODE_MOV_R32_TO_RM32);
	asm_x86_write_r32_disp(as, src_r32, dest_r32, dest_disp);
	}

	void asm_x86_mov_mem8_to_r32zx(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
	asm_x86_write_byte_2(as, 0x0f, OPCODE_MOVZX_RM8_TO_R32);
	asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
	}

	void asm_x86_mov_mem16_to_r32zx(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
	asm_x86_write_byte_2(as, 0x0f, OPCODE_MOVZX_RM16_TO_R32);
	asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
	}

	void asm_x86_mov_mem32_to_r32(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
	asm_x86_write_byte_1(as, OPCODE_MOV_RM32_TO_R32);
	asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
	}

	static void asm_x86_lea_disp_to_r32(asm_x86_t *as, int src_r32, int src_disp, int dest_r32) {
	asm_x86_write_byte_1(as, OPCODE_LEA_MEM_TO_R32);
	asm_x86_write_r32_disp(as, dest_r32, src_r32, src_disp);
	}

	#if 0
	void asm_x86_mov_i8_to_r8(asm_x86_t *as, int src_i8, int dest_r32) {
	asm_x86_write_byte_2(as, OPCODE_MOV_I8_TO_R8 \| dest_r32, src_i8);
	}
	#endif

	size_t asm_x86_mov_i32_to_r32(asm_x86_t *as, int32_t src_i32, int dest_r32) {
	asm_x86_write_byte_1(as, OPCODE_MOV_I32_TO_R32 \| dest_r32);
	size_t loc = mp_asm_base_get_code_pos(&as->base);
	asm_x86_write_word32(as, src_i32);
	return loc;
	}

	void asm_x86_and_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_AND_R32_TO_RM32);
	}

	void asm_x86_or_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_OR_R32_TO_RM32);
	}

	void asm_x86_xor_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_XOR_R32_TO_RM32);
	}

	void asm_x86_shl_r32_cl(asm_x86_t *as, int dest_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, 4, OPCODE_SHL_RM32_CL);
	}

	void asm_x86_shr_r32_cl(asm_x86_t *as, int dest_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, 5, OPCODE_SHR_RM32_CL);
	}

	void asm_x86_sar_r32_cl(asm_x86_t *as, int dest_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, 7, OPCODE_SAR_RM32_CL);
	}

	void asm_x86_add_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_ADD_R32_TO_RM32);
	}

	static void asm_x86_add_i32_to_r32(asm_x86_t *as, int src_i32, int dest_r32) {
	if (SIGNED_FIT8(src_i32)) {
	asm_x86_write_byte_2(as, OPCODE_ADD_I8_TO_RM32, MODRM_R32(0) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r32));
	asm_x86_write_byte_1(as, src_i32 & 0xff);
	} else {
	asm_x86_write_byte_2(as, OPCODE_ADD_I32_TO_RM32, MODRM_R32(0) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r32));
	asm_x86_write_word32(as, src_i32);
	}
	}

	void asm_x86_sub_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	asm_x86_generic_r32_r32(as, dest_r32, src_r32, OPCODE_SUB_R32_FROM_RM32);
	}

	static void asm_x86_sub_r32_i32(asm_x86_t *as, int dest_r32, int src_i32) {
	if (SIGNED_FIT8(src_i32)) {
	// defaults to 32 bit operation
	asm_x86_write_byte_2(as, OPCODE_SUB_I8_FROM_RM32, MODRM_R32(5) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r32));
	asm_x86_write_byte_1(as, src_i32 & 0xff);
	} else {
	// defaults to 32 bit operation
	asm_x86_write_byte_2(as, OPCODE_SUB_I32_FROM_RM32, MODRM_R32(5) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r32));
	asm_x86_write_word32(as, src_i32);
	}
	}

	void asm_x86_mul_r32_r32(asm_x86_t *as, int dest_r32, int src_r32) {
	// imul reg32, reg/mem32 -- 0x0f 0xaf /r
	asm_x86_write_byte_3(as, 0x0f, 0xaf, MODRM_R32(dest_r32) \| MODRM_RM_REG \| MODRM_RM_R32(src_r32));
	}

	#if 0
	/* shifts not tested */
	void asm_x86_shl_r32_by_imm(asm_x86_t *as, int r32, int imm) {
	asm_x86_write_byte_2(as, OPCODE_SHL_RM32_BY_I8, MODRM_R32(4) \| MODRM_RM_REG \| MODRM_RM_R32(r32));
	asm_x86_write_byte_1(as, imm);
	}

	void asm_x86_shr_r32_by_imm(asm_x86_t *as, int r32, int imm) {
	asm_x86_write_byte_2(as, OPCODE_SHR_RM32_BY_I8, MODRM_R32(5) \| MODRM_RM_REG \| MODRM_RM_R32(r32));
	asm_x86_write_byte_1(as, imm);
	}

	void asm_x86_sar_r32_by_imm(asm_x86_t *as, int r32, int imm) {
	asm_x86_write_byte_2(as, OPCODE_SAR_RM32_BY_I8, MODRM_R32(7) \| MODRM_RM_REG \| MODRM_RM_R32(r32));
	asm_x86_write_byte_1(as, imm);
	}
	#endif

	void asm_x86_cmp_r32_with_r32(asm_x86_t *as, int src_r32_a, int src_r32_b) {
	asm_x86_generic_r32_r32(as, src_r32_b, src_r32_a, OPCODE_CMP_R32_WITH_RM32);
	}

	#if 0
	void asm_x86_cmp_i32_with_r32(asm_x86_t *as, int src_i32, int src_r32) {
	if (SIGNED_FIT8(src_i32)) {
	asm_x86_write_byte_2(as, OPCODE_CMP_I8_WITH_RM32, MODRM_R32(7) \| MODRM_RM_REG \| MODRM_RM_R32(src_r32));
	asm_x86_write_byte_1(as, src_i32 & 0xff);
	} else {
	asm_x86_write_byte_2(as, OPCODE_CMP_I32_WITH_RM32, MODRM_R32(7) \| MODRM_RM_REG \| MODRM_RM_R32(src_r32));
	asm_x86_write_word32(as, src_i32);
	}
	}
	#endif

	void asm_x86_test_r8_with_r8(asm_x86_t *as, int src_r32_a, int src_r32_b) {
	asm_x86_write_byte_2(as, OPCODE_TEST_R8_WITH_RM8, MODRM_R32(src_r32_a) \| MODRM_RM_REG \| MODRM_RM_R32(src_r32_b));
	}

	void asm_x86_test_r32_with_r32(asm_x86_t *as, int src_r32_a, int src_r32_b) {
	asm_x86_generic_r32_r32(as, src_r32_b, src_r32_a, OPCODE_TEST_R32_WITH_RM32);
	}

	void asm_x86_setcc_r8(asm_x86_t *as, mp_uint_t jcc_type, int dest_r8) {
	asm_x86_write_byte_3(as, OPCODE_SETCC_RM8_A, OPCODE_SETCC_RM8_B \| jcc_type, MODRM_R32(0) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r8));
	}

	void asm_x86_jmp_reg(asm_x86_t *as, int src_r32) {
	asm_x86_write_byte_2(as, OPCODE_JMP_RM32, MODRM_R32(4) \| MODRM_RM_REG \| MODRM_RM_R32(src_r32));
	}

	static mp_uint_t get_label_dest(asm_x86_t *as, mp_uint_t label) {
	assert(label < as->base.max_num_labels);
	return as->base.label_offsets[label];
	}

	void asm_x86_jmp_label(asm_x86_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_x86_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_x86_write_byte_1(as, OPCODE_JMP_REL32);
	asm_x86_write_word32(as, rel);
	}
	}

	void asm_x86_jcc_label(asm_x86_t *as, mp_uint_t 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_x86_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_x86_write_byte_2(as, OPCODE_JCC_REL32_A, OPCODE_JCC_REL32_B \| jcc_type);
	asm_x86_write_word32(as, rel);
	}
	}

	void asm_x86_entry(asm_x86_t *as, int num_locals) {
	assert(num_locals >= 0);
	asm_x86_push_r32(as, ASM_X86_REG_EBP);
	asm_x86_push_r32(as, ASM_X86_REG_EBX);
	asm_x86_push_r32(as, ASM_X86_REG_ESI);
	asm_x86_push_r32(as, ASM_X86_REG_EDI);
	num_locals \|= 3; // make it odd so stack is aligned on 16 byte boundary
	asm_x86_sub_r32_i32(as, ASM_X86_REG_ESP, num_locals * WORD_SIZE);
	as->num_locals = num_locals;
	}

	void asm_x86_exit(asm_x86_t *as) {
	asm_x86_sub_r32_i32(as, ASM_X86_REG_ESP, -as->num_locals * WORD_SIZE);
	asm_x86_pop_r32(as, ASM_X86_REG_EDI);
	asm_x86_pop_r32(as, ASM_X86_REG_ESI);
	asm_x86_pop_r32(as, ASM_X86_REG_EBX);
	asm_x86_pop_r32(as, ASM_X86_REG_EBP);
	asm_x86_ret(as);
	}

	static int asm_x86_arg_offset_from_esp(asm_x86_t *as, size_t arg_num) {
	// Above esp are: locals, 4 saved registers, return eip, arguments
	return (as->num_locals + 4 + 1 + arg_num) * WORD_SIZE;
	}

	#if 0
	void asm_x86_push_arg(asm_x86_t *as, int src_arg_num) {
	asm_x86_push_disp(as, ASM_X86_REG_ESP, asm_x86_arg_offset_from_esp(as, src_arg_num));
	}
	#endif

	void asm_x86_mov_arg_to_r32(asm_x86_t *as, int src_arg_num, int dest_r32) {
	asm_x86_mov_mem32_to_r32(as, ASM_X86_REG_ESP, asm_x86_arg_offset_from_esp(as, src_arg_num), dest_r32);
	}

	#if 0
	void asm_x86_mov_r32_to_arg(asm_x86_t *as, int src_r32, int dest_arg_num) {
	asm_x86_mov_r32_to_mem32(as, src_r32, ASM_X86_REG_ESP, asm_x86_arg_offset_from_esp(as, dest_arg_num));
	}
	#endif

	// locals:
	// - stored on the stack in ascending order
	// - numbered 0 through as->num_locals-1
	// - ESP points to the first local
	//
	// \| ESP
	// v
	// l0 l1 l2 ... l(n-1)
	// ^ ^
	// \| low address \| high address in RAM
	//
	static int asm_x86_local_offset_from_esp(asm_x86_t *as, int local_num) {
	(void)as;
	// Stack is full descending, ESP points to local0
	return local_num * WORD_SIZE;
	}

	void asm_x86_mov_local_to_r32(asm_x86_t *as, int src_local_num, int dest_r32) {
	asm_x86_mov_mem32_to_r32(as, ASM_X86_REG_ESP, asm_x86_local_offset_from_esp(as, src_local_num), dest_r32);
	}

	void asm_x86_mov_r32_to_local(asm_x86_t *as, int src_r32, int dest_local_num) {
	asm_x86_mov_r32_to_mem32(as, src_r32, ASM_X86_REG_ESP, asm_x86_local_offset_from_esp(as, dest_local_num));
	}

	void asm_x86_mov_local_addr_to_r32(asm_x86_t *as, int local_num, int dest_r32) {
	int offset = asm_x86_local_offset_from_esp(as, local_num);
	if (offset == 0) {
	asm_x86_mov_r32_r32(as, dest_r32, ASM_X86_REG_ESP);
	} else {
	asm_x86_lea_disp_to_r32(as, ASM_X86_REG_ESP, offset, dest_r32);
	}
	}

	void asm_x86_mov_reg_pcrel(asm_x86_t *as, int dest_r32, mp_uint_t label) {
	asm_x86_write_byte_1(as, OPCODE_CALL_REL32);
	asm_x86_write_word32(as, 0);
	mp_uint_t dest = get_label_dest(as, label);
	mp_int_t rel = dest - as->base.code_offset;
	asm_x86_pop_r32(as, dest_r32);
	// PC rel is usually a forward reference, so need to assume it's large
	asm_x86_write_byte_2(as, OPCODE_ADD_I32_TO_RM32, MODRM_R32(0) \| MODRM_RM_REG \| MODRM_RM_R32(dest_r32));
	asm_x86_write_word32(as, rel);
	}

	#if 0
	void asm_x86_push_local(asm_x86_t *as, int local_num) {
	asm_x86_push_disp(as, ASM_X86_REG_ESP, asm_x86_local_offset_from_esp(as, local_num));
	}

	void asm_x86_push_local_addr(asm_x86_t *as, int local_num, int temp_r32) {
	asm_x86_mov_r32_r32(as, temp_r32, ASM_X86_REG_ESP);
	asm_x86_add_i32_to_r32(as, asm_x86_local_offset_from_esp(as, local_num), temp_r32);
	asm_x86_push_r32(as, temp_r32);
	}
	#endif

	void asm_x86_call_ind(asm_x86_t *as, size_t fun_id, mp_uint_t n_args, int temp_r32) {
	assert(n_args <= 4);

	// Align stack on 16-byte boundary during the call
	unsigned int align = ((n_args + 3) & ~3) - n_args;
	if (align) {
	asm_x86_sub_r32_i32(as, ASM_X86_REG_ESP, align * WORD_SIZE);
	}

	if (n_args > 3) {
	asm_x86_push_r32(as, ASM_X86_REG_ARG_4);
	}
	if (n_args > 2) {
	asm_x86_push_r32(as, ASM_X86_REG_ARG_3);
	}
	if (n_args > 1) {
	asm_x86_push_r32(as, ASM_X86_REG_ARG_2);
	}
	if (n_args > 0) {
	asm_x86_push_r32(as, ASM_X86_REG_ARG_1);
	}

	// Load the pointer to the function and make the call
	asm_x86_mov_mem32_to_r32(as, ASM_X86_REG_FUN_TABLE, fun_id * WORD_SIZE, temp_r32);
	asm_x86_write_byte_2(as, OPCODE_CALL_RM32, MODRM_R32(2) \| MODRM_RM_REG \| MODRM_RM_R32(temp_r32));

	// the caller must clean up the stack
	if (n_args > 0) {
	asm_x86_add_i32_to_r32(as, (n_args + align) * WORD_SIZE, ASM_X86_REG_ESP);
	}
	}

	#endif // MICROPY_EMIT_X86