py/asmx64.c - lite/micropython - Linaro Git Browser

 #include <stdint.h>
 #include <stdio.h>
 #include <assert.h>
 #include <string.h>

 #include "misc.h"
 #include "mpconfig.h"

 // wrapper around everything in this file
 #if MICROPY_EMIT_X64

 #include <sys/types.h>
 #include <sys/mman.h>

 #include "asmx64.h"

 #if defined(__OpenBSD__) || defined(__MACH__)
 #define MAP_ANONYMOUS MAP_ANON
 #endif

 /* all offsets are measured in multiples of 8 bytes */
 #define WORD_SIZE                (8)

 #define OPCODE_NOP               (0x90)
 #define OPCODE_PUSH_R64          (0x50)
 #define OPCODE_PUSH_I64          (0x68)
 #define OPCODE_PUSH_M64          (0xff) /* /6 */
 #define OPCODE_POP_R64           (0x58)
 #define OPCODE_RET               (0xc3)
 #define OPCODE_MOV_I8_TO_R8      (0xb0) /* +rb */
 #define OPCODE_MOV_I64_TO_R64    (0xb8)
 #define OPCODE_MOV_I32_TO_RM32   (0xc7)
 #define OPCODE_MOV_R64_TO_RM64   (0x89)
 #define OPCODE_MOV_RM64_TO_R64   (0x8b)
 #define OPCODE_LEA_MEM_TO_R64    (0x8d) /* /r */
 #define OPCODE_XOR_R64_TO_RM64   (0x31) /* /r */
 #define OPCODE_ADD_R64_TO_RM64   (0x01)
 #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_CMP_I32_WITH_RM32 (0x81) /* /7 */
 #define OPCODE_CMP_I8_WITH_RM32  (0x83) /* /7 */
 #define OPCODE_CMP_R64_WITH_RM64 (0x39)
 #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) << 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)

 #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 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)

 struct _asm_x64_t {
     int pass;
     uint code_offset;
     uint code_size;
     byte *code_base;
     byte dummy_data[8];

     uint max_num_labels;
     int *label_offsets;
     int num_locals;
 };

 // for allocating memory, see src/v8/src/platform-linux.cc
 void *alloc_mem(uint req_size, uint *alloc_size, bool is_exec) {
     req_size = (req_size + 0xfff) & (~0xfff);
     int prot = PROT_READ | PROT_WRITE | (is_exec ? PROT_EXEC : 0);
     void *ptr = mmap(NULL, req_size, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (ptr == MAP_FAILED) {
         assert(0);
     }
     *alloc_size = req_size;
     return ptr;
 }

 asm_x64_t *asm_x64_new(uint max_num_labels) {
     asm_x64_t *as;

     as = m_new(asm_x64_t, 1);
     as->pass = 0;
     as->code_offset = 0;
     as->code_size = 0;
     as->code_base = NULL;
     as->max_num_labels = max_num_labels;
     as->label_offsets = m_new(int, max_num_labels);
     as->num_locals = 0;

     return as;
 }

 void asm_x64_free(asm_x64_t *as, bool free_code) {
     if (free_code) {
         // need to un-mmap
         //m_free(as->code_base);
     }
     /*
     if (as->label != NULL) {
         int i;
         for (i = 0; i < as->label->len; ++i)
         {
             Label* lab = &g_array_index(as->label, Label, i);
             if (lab->unresolved != NULL)
                 g_array_free(lab->unresolved, true);
         }
         g_array_free(as->label, true);
     }
     */
     m_del_obj(asm_x64_t, as);
 }

 void asm_x64_start_pass(asm_x64_t *as, int pass) {
     as->pass = pass;
     as->code_offset = 0;
     if (pass == ASM_X64_PASS_2) {
         // reset all labels
         memset(as->label_offsets, -1, as->max_num_labels * sizeof(int));
     }
 }

 void asm_x64_end_pass(asm_x64_t *as) {
     if (as->pass == ASM_X64_PASS_2) {
         // calculate size of code in bytes
         as->code_size = as->code_offset;
         //as->code_base = m_new(byte, as->code_size); need to allocale executable memory
         uint actual_alloc;
         as->code_base = alloc_mem(as->code_size, &actual_alloc, true);
         //printf("code_size: %u\n", as->code_size);
     }

     /*
     // check labels are resolved
     if (as->label != NULL)
     {
         int i;
         for (i = 0; i < as->label->len; ++i)
             if (g_array_index(as->label, Label, i).unresolved != NULL)
                 return false;
     }
     */
 }

 // all functions must go through this one to emit bytes
 STATIC byte *asm_x64_get_cur_to_write_bytes(asm_x64_t *as, int num_bytes_to_write) {
     //printf("emit %d\n", num_bytes_to_write);
     if (as->pass < ASM_X64_PASS_3) {
         as->code_offset += num_bytes_to_write;
         return as->dummy_data;
     } else {
         assert(as->code_offset + num_bytes_to_write <= as->code_size);
         byte *c = as->code_base + as->code_offset;
         as->code_offset += num_bytes_to_write;
         return c;
     }
 }

 uint asm_x64_get_code_size(asm_x64_t *as) {
     return as->code_size;
 }

 void *asm_x64_get_code(asm_x64_t *as) {
     return as->code_base;
 }

 STATIC void asm_x64_write_byte_1(asm_x64_t *as, byte b1) {
     byte* c = asm_x64_get_cur_to_write_bytes(as, 1);
     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);
     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);
     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);
     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);
     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 != REG_RSP);

     if (disp_offset == 0 && disp_r64 != 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);
     }
 }

 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) {
     asm_x64_write_byte_1(as, OPCODE_PUSH_R64 | src_r64);
 }

 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) {
     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) {
     asm_x64_write_byte_1(as, OPCODE_POP_R64 | dest_r64);
 }

 STATIC void asm_x64_ret(asm_x64_t *as) {
     asm_x64_write_byte_1(as, OPCODE_RET);
 }

 void asm_x64_mov_r32_to_r32(asm_x64_t *as, int src_r32, int dest_r32) {
     // defaults to 32 bit operation
     asm_x64_write_byte_2(as, OPCODE_MOV_R64_TO_RM64, MODRM_R64(src_r32) | MODRM_RM_REG | MODRM_RM_R64(dest_r32));
 }

 void asm_x64_mov_r64_to_r64(asm_x64_t *as, int src_r64, int dest_r64) {
     // use REX prefix for 64 bit operation
     asm_x64_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_MOV_R64_TO_RM64, MODRM_R64(src_r64) | MODRM_RM_REG | MODRM_RM_R64(dest_r64));
 }

 void asm_x64_mov_r64_to_disp(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, OPCODE_MOV_R64_TO_RM64);
     asm_x64_write_r64_disp(as, src_r64, dest_r64, dest_disp);
 }

 void asm_x64_mov_disp_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, OPCODE_MOV_RM64_TO_R64);
     asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
 }

 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
     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) {
     asm_x64_write_byte_2(as, OPCODE_MOV_I8_TO_R8 | dest_r64, src_i8);
 }

 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
     asm_x64_write_byte_1(as, OPCODE_MOV_I64_TO_R64 | dest_r64);
     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, OPCODE_MOV_I64_TO_R64 | dest_r64);
     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) {
     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);
     }
 }

 void asm_x64_mov_i32_to_disp(asm_x64_t *as, int src_i32, int dest_r32, int dest_disp)
 {
     assert(0);
     asm_x64_write_byte_1(as, OPCODE_MOV_I32_TO_RM32);
     //asm_x64_write_r32_disp(as, 0, dest_r32, dest_disp);
     asm_x64_write_word32(as, src_i32);
 }

 void asm_x64_xor_r64_to_r64(asm_x64_t *as, int src_r64, int dest_r64) {
     asm_x64_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_XOR_R64_TO_RM64, MODRM_R64(src_r64) | MODRM_RM_REG | MODRM_RM_R64(dest_r64));
 }

 void asm_x64_add_r64_to_r64(asm_x64_t *as, int src_r64, int dest_r64) {
     asm_x64_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_ADD_R64_TO_RM64, MODRM_R64(src_r64) | MODRM_RM_REG | MODRM_RM_R64(dest_r64));
 }

 void asm_x64_add_i32_to_r32(asm_x64_t *as, int src_i32, int dest_r32)
 {
     assert(dest_r32 != REG_RSP); // in this case i think src_i32 must be 64 bits
     if (SIGNED_FIT8(src_i32))
     {
         asm_x64_write_byte_2(as, OPCODE_ADD_I8_TO_RM32, MODRM_R64(0) | MODRM_RM_REG | MODRM_RM_R64(dest_r32));
         asm_x64_write_byte_1(as, src_i32 & 0xff);
     }
     else
     {
         asm_x64_write_byte_2(as, OPCODE_ADD_I32_TO_RM32, MODRM_R64(0) | MODRM_RM_REG | MODRM_RM_R64(dest_r32));
         asm_x64_write_word32(as, src_i32);
     }
 }

 void asm_x64_sub_r32_from_r32(asm_x64_t *as, int src_r32, int dest_r32) {
     // defaults to 32 bit operation
     asm_x64_write_byte_2(as, OPCODE_SUB_R64_FROM_RM64, MODRM_R64(src_r32) | MODRM_RM_REG | MODRM_RM_R64(dest_r32));
 }

 void asm_x64_sub_r64_from_r64(asm_x64_t *as, int src_r64, int dest_r64) {
     // use REX prefix for 64 bit operation
     asm_x64_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_SUB_R64_FROM_RM64, MODRM_R64(src_r64) | MODRM_RM_REG | MODRM_RM_R64(dest_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);
     }
 }

 void asm_x64_sub_i32_from_r64(asm_x64_t *as, int src_i32, int dest_r64) {
     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);
     }
 }

 /* shifts not tested */
 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_write_byte_3(as, REX_PREFIX | REX_W, OPCODE_CMP_R64_WITH_RM64, MODRM_R64(src_r64_a) | MODRM_RM_REG | MODRM_RM_R64(src_r64_b));
 }

 void asm_x64_cmp_r32_with_disp(asm_x64_t *as, int src_r32_a, int src_r32_b, int src_disp_b) {
     assert(0);
     asm_x64_write_byte_1(as, OPCODE_CMP_R64_WITH_RM64);
     //asm_x64_write_r32_disp(as, src_r32_a, src_r32_b, src_disp_b);
 }

 void asm_x64_cmp_disp_with_r32(asm_x64_t *as, int src_r32_a, int src_disp_a, int src_r32_b) {
     assert(0);
     asm_x64_write_byte_1(as, OPCODE_CMP_RM32_WITH_R32);
     //asm_x64_write_r32_disp(as, src_r32_b, src_r32_a, src_disp_a);
 }

 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 == REG_RAX);
     assert(src_r64_b == 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) {
     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));
 }

 void asm_x64_label_assign(asm_x64_t *as, int label) {
     assert(label < as->max_num_labels);
     if (as->pass == ASM_X64_PASS_2) {
         // assign label offset
         assert(as->label_offsets[label] == -1);
         as->label_offsets[label] = as->code_offset;
     } else if (as->pass == ASM_X64_PASS_3) {
         // ensure label offset has not changed from PASS_2 to PASS_3
         //printf("l%d: (at %d=%ld)\n", label, as->label_offsets[label], as->code_offset);
         assert(as->label_offsets[label] == as->code_offset);
     }
 }

 STATIC int get_label_dest(asm_x64_t *as, int label) {
     assert(label < as->max_num_labels);
     return as->label_offsets[label];
 }

 void asm_x64_jmp_label(asm_x64_t *as, int label) {
     int dest = get_label_dest(as, label);
     int rel = dest - as->code_offset;
     if (dest >= 0 && 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, int label) {
     int dest = get_label_dest(as, label);
     int rel = dest - as->code_offset;
     if (dest >= 0 && 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) {
     asm_x64_push_r64(as, REG_RBP);
     asm_x64_mov_r64_to_r64(as, REG_RSP, REG_RBP);
     if (num_locals < 0) {
         num_locals = 0;
     }
     num_locals |= 1; // make it odd so stack is aligned on 16 byte boundary
     asm_x64_sub_i32_from_r64(as, num_locals * WORD_SIZE, REG_RSP);
     asm_x64_push_r64(as, REG_RBX);
     as->num_locals = num_locals;
 }

 void asm_x64_exit(asm_x64_t *as) {
     asm_x64_pop_r64(as, REG_RBX);
     asm_x64_write_byte_1(as, OPCODE_LEAVE);
     asm_x64_ret(as);
 }

 void asm_x64_push_arg(asm_x64_t *as, int src_arg_num) {
     assert(0);
     asm_x64_push_disp(as, REG_RBP, 8 + src_arg_num * WORD_SIZE);
 }

 void asm_x64_mov_arg_to_r32(asm_x64_t *as, int src_arg_num, int dest_r32) {
     assert(0);
     //asm_x64_mov_disp_to_r32(as, REG_RBP, 8 + src_arg_num * WORD_SIZE, dest_r32);
 }

 void asm_x64_mov_r32_to_arg(asm_x64_t *as, int src_r32, int dest_arg_num) {
     assert(0);
     //asm_x64_mov_r32_to_disp(as, src_r32, REG_RBP, 8 + dest_arg_num * WORD_SIZE);
 }

 // locals:
 //  - stored on the stack in ascending order
 //  - numbered 0 through as->num_locals-1
 //  - RBP points above the last local
 //
 //                          | RPB
 //                          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_disp_to_r64(as, 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_disp(as, src_r64, 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_to_r64(as, REG_RBP, dest_r64);
     } else {
         asm_x64_lea_disp_to_r64(as, REG_RBP, offset, dest_r64);
     }
 }

 void asm_x64_push_local(asm_x64_t *as, int local_num) {
     asm_x64_push_disp(as, 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_to_r64(as, REG_RBP, temp_r64);
     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, 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_to_r64(as, REG_RBP, REG_RSP);
 }

 void asm_x64_call_i1(asm_x64_t *as, void* func, int i1)
 {
     asm_x64_sub_i32_from_r32(as, 8, REG_RSP);
     asm_x64_sub_i32_from_r32(as, 12, 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, REG_RSP);
     asm_x64_mov_r64_to_r64(as, REG_RBP, REG_RSP);
 }
 */

 void asm_x64_call_ind(asm_x64_t *as, void *ptr, int temp_r64) {
 #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
	#include <stdint.h>
	#include <stdio.h>
	#include <assert.h>
	#include <string.h>

	#include "misc.h"
	#include "mpconfig.h"

	// wrapper around everything in this file
	#if MICROPY_EMIT_X64

	#include <sys/types.h>
	#include <sys/mman.h>

	#include "asmx64.h"

	#if defined(__OpenBSD__) \|\| defined(__MACH__)
	#define MAP_ANONYMOUS MAP_ANON
	#endif

	/* all offsets are measured in multiples of 8 bytes */
	#define WORD_SIZE (8)

	#define OPCODE_NOP (0x90)
	#define OPCODE_PUSH_R64 (0x50)
	#define OPCODE_PUSH_I64 (0x68)
	#define OPCODE_PUSH_M64 (0xff) /* /6 */
	#define OPCODE_POP_R64 (0x58)
	#define OPCODE_RET (0xc3)
	#define OPCODE_MOV_I8_TO_R8 (0xb0) /* +rb */
	#define OPCODE_MOV_I64_TO_R64 (0xb8)
	#define OPCODE_MOV_I32_TO_RM32 (0xc7)
	#define OPCODE_MOV_R64_TO_RM64 (0x89)
	#define OPCODE_MOV_RM64_TO_R64 (0x8b)
	#define OPCODE_LEA_MEM_TO_R64 (0x8d) /* /r */
	#define OPCODE_XOR_R64_TO_RM64 (0x31) /* /r */
	#define OPCODE_ADD_R64_TO_RM64 (0x01)
	#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_CMP_I32_WITH_RM32 (0x81) /* /7 */
	#define OPCODE_CMP_I8_WITH_RM32 (0x83) /* /7 */
	#define OPCODE_CMP_R64_WITH_RM64 (0x39)
	#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) << 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)

	#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 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)

	struct _asm_x64_t {
	int pass;
	uint code_offset;
	uint code_size;
	byte *code_base;
	byte dummy_data[8];

	uint max_num_labels;
	int *label_offsets;
	int num_locals;
	};

	// for allocating memory, see src/v8/src/platform-linux.cc
	void alloc_mem(uint req_size, uint alloc_size, bool is_exec) {
	req_size = (req_size + 0xfff) & (~0xfff);
	int prot = PROT_READ \| PROT_WRITE \| (is_exec ? PROT_EXEC : 0);
	void *ptr = mmap(NULL, req_size, prot, MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
	if (ptr == MAP_FAILED) {
	assert(0);
	}
	*alloc_size = req_size;
	return ptr;
	}

	asm_x64_t *asm_x64_new(uint max_num_labels) {
	asm_x64_t *as;

	as = m_new(asm_x64_t, 1);
	as->pass = 0;
	as->code_offset = 0;
	as->code_size = 0;
	as->code_base = NULL;
	as->max_num_labels = max_num_labels;
	as->label_offsets = m_new(int, max_num_labels);
	as->num_locals = 0;

	return as;
	}

	void asm_x64_free(asm_x64_t *as, bool free_code) {
	if (free_code) {
	// need to un-mmap
	//m_free(as->code_base);
	}
	/*
	if (as->label != NULL) {
	int i;
	for (i = 0; i < as->label->len; ++i)
	{
	Label* lab = &g_array_index(as->label, Label, i);
	if (lab->unresolved != NULL)
	g_array_free(lab->unresolved, true);
	}
	g_array_free(as->label, true);
	}
	*/
	m_del_obj(asm_x64_t, as);
	}

	void asm_x64_start_pass(asm_x64_t *as, int pass) {
	as->pass = pass;
	as->code_offset = 0;
	if (pass == ASM_X64_PASS_2) {
	// reset all labels
	memset(as->label_offsets, -1, as->max_num_labels * sizeof(int));
	}
	}

	void asm_x64_end_pass(asm_x64_t *as) {
	if (as->pass == ASM_X64_PASS_2) {
	// calculate size of code in bytes
	as->code_size = as->code_offset;
	//as->code_base = m_new(byte, as->code_size); need to allocale executable memory
	uint actual_alloc;
	as->code_base = alloc_mem(as->code_size, &actual_alloc, true);
	//printf("code_size: %u\n", as->code_size);
	}

	/*
	// check labels are resolved
	if (as->label != NULL)
	{
	int i;
	for (i = 0; i < as->label->len; ++i)
	if (g_array_index(as->label, Label, i).unresolved != NULL)
	return false;
	}
	*/
	}

	// all functions must go through this one to emit bytes
	STATIC byte asm_x64_get_cur_to_write_bytes(asm_x64_t as, int num_bytes_to_write) {
	//printf("emit %d\n", num_bytes_to_write);
	if (as->pass < ASM_X64_PASS_3) {
	as->code_offset += num_bytes_to_write;
	return as->dummy_data;
	} else {
	assert(as->code_offset + num_bytes_to_write <= as->code_size);
	byte *c = as->code_base + as->code_offset;
	as->code_offset += num_bytes_to_write;
	return c;
	}
	}

	uint asm_x64_get_code_size(asm_x64_t *as) {
	return as->code_size;
	}

	void asm_x64_get_code(asm_x64_t as) {
	return as->code_base;
	}

	STATIC void asm_x64_write_byte_1(asm_x64_t *as, byte b1) {
	byte* c = asm_x64_get_cur_to_write_bytes(as, 1);
	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);
	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);
	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);
	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);
	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 != REG_RSP);

	if (disp_offset == 0 && disp_r64 != 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);
	}
	}

	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) {
	asm_x64_write_byte_1(as, OPCODE_PUSH_R64 \| src_r64);
	}

	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) {
	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) {
	asm_x64_write_byte_1(as, OPCODE_POP_R64 \| dest_r64);
	}

	STATIC void asm_x64_ret(asm_x64_t *as) {
	asm_x64_write_byte_1(as, OPCODE_RET);
	}

	void asm_x64_mov_r32_to_r32(asm_x64_t *as, int src_r32, int dest_r32) {
	// defaults to 32 bit operation
	asm_x64_write_byte_2(as, OPCODE_MOV_R64_TO_RM64, MODRM_R64(src_r32) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r32));
	}

	void asm_x64_mov_r64_to_r64(asm_x64_t *as, int src_r64, int dest_r64) {
	// use REX prefix for 64 bit operation
	asm_x64_write_byte_3(as, REX_PREFIX \| REX_W, OPCODE_MOV_R64_TO_RM64, MODRM_R64(src_r64) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r64));
	}

	void asm_x64_mov_r64_to_disp(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, OPCODE_MOV_R64_TO_RM64);
	asm_x64_write_r64_disp(as, src_r64, dest_r64, dest_disp);
	}

	void asm_x64_mov_disp_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, OPCODE_MOV_RM64_TO_R64);
	asm_x64_write_r64_disp(as, dest_r64, src_r64, src_disp);
	}

	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
	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) {
	asm_x64_write_byte_2(as, OPCODE_MOV_I8_TO_R8 \| dest_r64, src_i8);
	}

	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
	asm_x64_write_byte_1(as, OPCODE_MOV_I64_TO_R64 \| dest_r64);
	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, OPCODE_MOV_I64_TO_R64 \| dest_r64);
	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) {
	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);
	}
	}

	void asm_x64_mov_i32_to_disp(asm_x64_t *as, int src_i32, int dest_r32, int dest_disp)
	{
	assert(0);
	asm_x64_write_byte_1(as, OPCODE_MOV_I32_TO_RM32);
	//asm_x64_write_r32_disp(as, 0, dest_r32, dest_disp);
	asm_x64_write_word32(as, src_i32);
	}

	void asm_x64_xor_r64_to_r64(asm_x64_t *as, int src_r64, int dest_r64) {
	asm_x64_write_byte_3(as, REX_PREFIX \| REX_W, OPCODE_XOR_R64_TO_RM64, MODRM_R64(src_r64) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r64));
	}

	void asm_x64_add_r64_to_r64(asm_x64_t *as, int src_r64, int dest_r64) {
	asm_x64_write_byte_3(as, REX_PREFIX \| REX_W, OPCODE_ADD_R64_TO_RM64, MODRM_R64(src_r64) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r64));
	}

	void asm_x64_add_i32_to_r32(asm_x64_t *as, int src_i32, int dest_r32)
	{
	assert(dest_r32 != REG_RSP); // in this case i think src_i32 must be 64 bits
	if (SIGNED_FIT8(src_i32))
	{
	asm_x64_write_byte_2(as, OPCODE_ADD_I8_TO_RM32, MODRM_R64(0) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r32));
	asm_x64_write_byte_1(as, src_i32 & 0xff);
	}
	else
	{
	asm_x64_write_byte_2(as, OPCODE_ADD_I32_TO_RM32, MODRM_R64(0) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r32));
	asm_x64_write_word32(as, src_i32);
	}
	}

	void asm_x64_sub_r32_from_r32(asm_x64_t *as, int src_r32, int dest_r32) {
	// defaults to 32 bit operation
	asm_x64_write_byte_2(as, OPCODE_SUB_R64_FROM_RM64, MODRM_R64(src_r32) \| MODRM_RM_REG \| MODRM_RM_R64(dest_r32));
	}

	void asm_x64_sub_r64_from_r64(asm_x64_t *as, int src_r64, int dest_r64) {
	// use REX prefix for 64 bit operation
	asm_x64_write_byte_3(as, REX_PREFIX \| REX_W, OPCODE_SUB_R64_FROM_RM64, MODRM_R64(src_r64) \| MODRM_RM_REG \| MODRM_RM_R64(dest_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);
	}
	}

	void asm_x64_sub_i32_from_r64(asm_x64_t *as, int src_i32, int dest_r64) {
	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);
	}
	}

	/* shifts not tested */
	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_write_byte_3(as, REX_PREFIX \| REX_W, OPCODE_CMP_R64_WITH_RM64, MODRM_R64(src_r64_a) \| MODRM_RM_REG \| MODRM_RM_R64(src_r64_b));
	}

	void asm_x64_cmp_r32_with_disp(asm_x64_t *as, int src_r32_a, int src_r32_b, int src_disp_b) {
	assert(0);
	asm_x64_write_byte_1(as, OPCODE_CMP_R64_WITH_RM64);
	//asm_x64_write_r32_disp(as, src_r32_a, src_r32_b, src_disp_b);
	}

	void asm_x64_cmp_disp_with_r32(asm_x64_t *as, int src_r32_a, int src_disp_a, int src_r32_b) {
	assert(0);
	asm_x64_write_byte_1(as, OPCODE_CMP_RM32_WITH_R32);
	//asm_x64_write_r32_disp(as, src_r32_b, src_r32_a, src_disp_a);
	}

	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 == REG_RAX);
	assert(src_r64_b == 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) {
	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));
	}

	void asm_x64_label_assign(asm_x64_t *as, int label) {
	assert(label < as->max_num_labels);
	if (as->pass == ASM_X64_PASS_2) {
	// assign label offset
	assert(as->label_offsets[label] == -1);
	as->label_offsets[label] = as->code_offset;
	} else if (as->pass == ASM_X64_PASS_3) {
	// ensure label offset has not changed from PASS_2 to PASS_3
	//printf("l%d: (at %d=%ld)\n", label, as->label_offsets[label], as->code_offset);
	assert(as->label_offsets[label] == as->code_offset);
	}
	}

	STATIC int get_label_dest(asm_x64_t *as, int label) {
	assert(label < as->max_num_labels);
	return as->label_offsets[label];
	}

	void asm_x64_jmp_label(asm_x64_t *as, int label) {
	int dest = get_label_dest(as, label);
	int rel = dest - as->code_offset;
	if (dest >= 0 && 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, int label) {
	int dest = get_label_dest(as, label);
	int rel = dest - as->code_offset;
	if (dest >= 0 && 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) {
	asm_x64_push_r64(as, REG_RBP);
	asm_x64_mov_r64_to_r64(as, REG_RSP, REG_RBP);
	if (num_locals < 0) {
	num_locals = 0;
	}
	num_locals \|= 1; // make it odd so stack is aligned on 16 byte boundary
	asm_x64_sub_i32_from_r64(as, num_locals * WORD_SIZE, REG_RSP);
	asm_x64_push_r64(as, REG_RBX);
	as->num_locals = num_locals;
	}

	void asm_x64_exit(asm_x64_t *as) {
	asm_x64_pop_r64(as, REG_RBX);
	asm_x64_write_byte_1(as, OPCODE_LEAVE);
	asm_x64_ret(as);
	}

	void asm_x64_push_arg(asm_x64_t *as, int src_arg_num) {
	assert(0);
	asm_x64_push_disp(as, REG_RBP, 8 + src_arg_num * WORD_SIZE);
	}

	void asm_x64_mov_arg_to_r32(asm_x64_t *as, int src_arg_num, int dest_r32) {
	assert(0);
	//asm_x64_mov_disp_to_r32(as, REG_RBP, 8 + src_arg_num * WORD_SIZE, dest_r32);
	}

	void asm_x64_mov_r32_to_arg(asm_x64_t *as, int src_r32, int dest_arg_num) {
	assert(0);
	//asm_x64_mov_r32_to_disp(as, src_r32, REG_RBP, 8 + dest_arg_num * WORD_SIZE);
	}

	// locals:
	// - stored on the stack in ascending order
	// - numbered 0 through as->num_locals-1
	// - RBP points above the last local
	//
	// \| RPB
	// 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_disp_to_r64(as, 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_disp(as, src_r64, 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_to_r64(as, REG_RBP, dest_r64);
	} else {
	asm_x64_lea_disp_to_r64(as, REG_RBP, offset, dest_r64);
	}
	}

	void asm_x64_push_local(asm_x64_t *as, int local_num) {
	asm_x64_push_disp(as, 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_to_r64(as, REG_RBP, temp_r64);
	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, 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_to_r64(as, REG_RBP, REG_RSP);
	}

	void asm_x64_call_i1(asm_x64_t as, void func, int i1)
	{
	asm_x64_sub_i32_from_r32(as, 8, REG_RSP);
	asm_x64_sub_i32_from_r32(as, 12, 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, REG_RSP);
	asm_x64_mov_r64_to_r64(as, REG_RBP, REG_RSP);
	}
	*/

	void asm_x64_call_ind(asm_x64_t as, void ptr, int temp_r64) {
	#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