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asmthumb.c

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  • asmthumb.c 14.96 KiB
    #include <stdio.h>
    #include <assert.h>
    #include <string.h>
    
    #include "misc.h"
    #include "mpconfig.h"
    #include "asmthumb.h"
    
    // wrapper around everything in this file
    #if MICROPY_EMIT_THUMB || MICROPY_EMIT_INLINE_THUMB
    
    #define UNSIGNED_FIT8(x) (((x) & 0xffffff00) == 0)
    #define UNSIGNED_FIT16(x) (((x) & 0xffff0000) == 0)
    #define SIGNED_FIT8(x) (((x) & 0xffffff80) == 0) || (((x) & 0xffffff80) == 0xffffff80)
    #define SIGNED_FIT9(x) (((x) & 0xffffff00) == 0) || (((x) & 0xffffff00) == 0xffffff00)
    #define SIGNED_FIT12(x) (((x) & 0xfffff800) == 0) || (((x) & 0xfffff800) == 0xfffff800)
    
    struct _asm_thumb_t {
        int pass;
        uint code_offset;
        uint code_size;
        byte *code_base;
        byte dummy_data[8];
    
        int max_num_labels;
        int *label_offsets;
        int num_locals;
        uint push_reglist;
        uint stack_adjust;
    };
    
    asm_thumb_t *asm_thumb_new(uint max_num_labels) {
        asm_thumb_t *as;
    
        as = m_new(asm_thumb_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_thumb_free(asm_thumb_t *as, bool free_code) {
        if (free_code) {
            m_del(byte, as->code_base, as->code_size);
        }
        /*
        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_thumb_t, as);
    }
    
    void asm_thumb_start_pass(asm_thumb_t *as, int pass) {
        as->pass = pass;
        as->code_offset = 0;
        if (pass == ASM_THUMB_PASS_2) {
            memset(as->label_offsets, -1, as->max_num_labels * sizeof(int));
        }
    }
    
    void asm_thumb_end_pass(asm_thumb_t *as) {
        if (as->pass == ASM_THUMB_PASS_2) {
            // calculate size of code in bytes
            as->code_size = as->code_offset;
            as->code_base = m_new(byte, as->code_size);
            //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_thumb_get_cur_to_write_bytes(asm_thumb_t *as, int num_bytes_to_write) {
        //printf("emit %d\n", num_bytes_to_write);
        if (as->pass < ASM_THUMB_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_thumb_get_code_size(asm_thumb_t *as) {
        return as->code_size;
    }
    
    void *asm_thumb_get_code(asm_thumb_t *as) {
        // need to set low bit to indicate that it's thumb code
        return (void *)(((machine_uint_t)as->code_base) | 1);
    }
    
    /*
    STATIC void asm_thumb_write_byte_1(asm_thumb_t *as, byte b1) {
        byte *c = asm_thumb_get_cur_to_write_bytes(as, 1);
        c[0] = b1;
    }
    */
    
    STATIC void asm_thumb_write_op16(asm_thumb_t *as, uint op) {
        byte *c = asm_thumb_get_cur_to_write_bytes(as, 2);
        // little endian
        c[0] = op;
        c[1] = op >> 8;
    }
    
    STATIC void asm_thumb_write_op32(asm_thumb_t *as, uint op1, uint op2) {
        byte *c = asm_thumb_get_cur_to_write_bytes(as, 4);
        // little endian, op1 then op2
        c[0] = op1;
        c[1] = op1 >> 8;
        c[2] = op2;
        c[3] = op2 >> 8;
    }
    
    /*
    #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)
    
    STATIC void asm_thumb_write_word32(asm_thumb_t *as, int w32) {
        byte *c = asm_thumb_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);
    }
    */
    
    // rlolist is a bit map indicating desired lo-registers
    #define OP_PUSH_RLIST(rlolist)      (0xb400 | (rlolist))
    #define OP_PUSH_RLIST_LR(rlolist)   (0xb400 | 0x0100 | (rlolist))
    #define OP_POP_RLIST(rlolist)       (0xbc00 | (rlolist))
    #define OP_POP_RLIST_PC(rlolist)    (0xbc00 | 0x0100 | (rlolist))
    
    #define OP_ADD_SP(num_words) (0xb000 | (num_words))
    #define OP_SUB_SP(num_words) (0xb080 | (num_words))
    
    void asm_thumb_entry(asm_thumb_t *as, int num_locals) {
        // work out what to push and how many extra space to reserve on stack
        // so that we have enough for all locals and it's aligned an 8-byte boundary
        uint reglist;
        uint stack_adjust;
        if (num_locals < 0) {
            num_locals = 0;
        }
        // don't ppop r0 because it's used for return value
        switch (num_locals) {
            case 0:
                reglist = 0xf2;
                stack_adjust = 0;
                break;
    
            case 1:
                reglist = 0xf2;
                stack_adjust = 0;
                break;
    
            case 2:
                reglist = 0xfe;
                stack_adjust = 0;
                break;
    
            case 3:
                reglist = 0xfe;
                stack_adjust = 0;
                break;
    
            default:
                reglist = 0xfe;
                stack_adjust = ((num_locals - 3) + 1) & (~1);
                break;
        }
        asm_thumb_write_op16(as, OP_PUSH_RLIST_LR(reglist));
        if (stack_adjust > 0) {
            asm_thumb_write_op16(as, OP_SUB_SP(stack_adjust));
        }
        as->push_reglist = reglist;
        as->stack_adjust = stack_adjust;
        as->num_locals = num_locals;
    }
    
    void asm_thumb_exit(asm_thumb_t *as) {
        if (as->stack_adjust > 0) {
            asm_thumb_write_op16(as, OP_ADD_SP(as->stack_adjust));
        }
        asm_thumb_write_op16(as, OP_POP_RLIST_PC(as->push_reglist));
    }
    
    void asm_thumb_label_assign(asm_thumb_t *as, int label) {
        assert(label < as->max_num_labels);
        if (as->pass == ASM_THUMB_PASS_2) {
            // assign label offset
            assert(as->label_offsets[label] == -1);
            as->label_offsets[label] = as->code_offset;
        } else if (as->pass == ASM_THUMB_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_thumb_t *as, int label) {
        assert(label < as->max_num_labels);
        return as->label_offsets[label];
    }
    
    #define OP_MOVS_RLO_I8(rlo_dest, i8_src) (0x2000 | ((rlo_dest) << 8) | (i8_src))
    
    // the i8_src value will be zero extended into the r32 register!
    void asm_thumb_movs_rlo_i8(asm_thumb_t *as, uint rlo_dest, int i8_src) {
        assert(rlo_dest < REG_R8);
        // movs rlo_dest, #i8_src
        asm_thumb_write_op16(as, OP_MOVS_RLO_I8(rlo_dest, i8_src));
    }
    
    #define OP_MOVW (0xf240)
    #define OP_MOVT (0xf2c0)
    
    // if loading lo half with movw, the i16 value will be zero extended into the r32 register!
    STATIC void asm_thumb_mov_reg_i16(asm_thumb_t *as, uint mov_op, uint reg_dest, int i16_src) {
        assert(reg_dest < REG_R15);
        // mov[wt] reg_dest, #i16_src
        asm_thumb_write_op32(as, mov_op | ((i16_src >> 1) & 0x0400) | ((i16_src >> 12) & 0xf), ((i16_src << 4) & 0x7000) | (reg_dest << 8) | (i16_src & 0xff));
    }
    
    // the i16_src value will be zero extended into the r32 register!
    void asm_thumb_movw_reg_i16(asm_thumb_t *as, uint reg_dest, int i16_src) {
        asm_thumb_mov_reg_i16(as, OP_MOVW, reg_dest, i16_src);
    }
    
    // the i16_src value will be zero extended into the r32 register!
    void asm_thumb_movt_reg_i16(asm_thumb_t *as, uint reg_dest, int i16_src) {
        asm_thumb_mov_reg_i16(as, OP_MOVT, reg_dest, i16_src);
    }
    
    void asm_thumb_mov_reg_reg(asm_thumb_t *as, uint reg_dest, uint reg_src) {
        uint op_lo;
        if (reg_src < 8) {
            op_lo = reg_src << 3;
        } else {
            op_lo = 0x40 | ((reg_src - 8) << 3);
        }
        if (reg_dest < 8) {
            op_lo |= reg_dest;
        } else {
            op_lo |= 0x80 | (reg_dest - 8);
        }
        // mov reg_dest, reg_src
        asm_thumb_write_op16(as, 0x4600 | op_lo);
    }
    
    #define OP_ADD_REG_REG_REG(rlo_dest, rlo_src_a, rlo_src_b) (0x1800 | ((rlo_src_b) << 6) | ((rlo_src_a) << 3) | (rlo_dest))
    
    void asm_thumb_add_reg_reg_reg(asm_thumb_t *as, uint rlo_dest, uint rlo_src_a, uint rlo_src_b) {
        asm_thumb_write_op16(as, OP_ADD_REG_REG_REG(rlo_dest, rlo_src_a, rlo_src_b));
    }
    
    #define OP_SUBS_RLO_RLO_I3(rlo_dest, rlo_src, i3_src) (0x1e00 | ((i3_src) << 6) | ((rlo_src) << 3) | (rlo_dest))
    
    void asm_thumb_subs_rlo_rlo_i3(asm_thumb_t *as, uint rlo_dest, uint rlo_src, int i3_src) {
        assert(rlo_dest < REG_R8);
        assert(rlo_src < REG_R8);
        asm_thumb_write_op16(as, OP_SUBS_RLO_RLO_I3(rlo_dest, rlo_src, i3_src));
    }
    
    #define OP_CMP_REG_REG(rlo_a, rlo_b) (0x4280 | ((rlo_b) << 3) | (rlo_a))
    
    void asm_thumb_cmp_reg_reg(asm_thumb_t *as, uint rlo_a, uint rlo_b) {
        asm_thumb_write_op16(as, OP_CMP_REG_REG(rlo_a, rlo_b));
    }
    
    #define OP_CMP_RLO_I8(rlo, i8) (0x2800 | ((rlo) << 8) | (i8))
    
    void asm_thumb_cmp_rlo_i8(asm_thumb_t *as, uint rlo, int i8) {
        assert(rlo < REG_R8);
        asm_thumb_write_op16(as, OP_CMP_RLO_I8(rlo, i8));
    }
    
    void asm_thumb_ite_ge(asm_thumb_t *as) {
        asm_thumb_write_op16(as, 0xbfac);
    }
    
    #define OP_B_N(byte_offset) (0xe000 | (((byte_offset) >> 1) & 0x07ff))
    
    void asm_thumb_b_n(asm_thumb_t *as, int label) {
        int dest = get_label_dest(as, label);
        int rel = dest - as->code_offset;
        rel -= 4; // account for instruction prefetch, PC is 4 bytes ahead of this instruction
        if (SIGNED_FIT12(rel)) {
            asm_thumb_write_op16(as, OP_B_N(rel));
        } else {
            printf("asm_thumb_b_n: branch does not fit in 12 bits\n");
        }
    }
    
    #define OP_BCC_N(cond, byte_offset) (0xd000 | ((cond) << 8) | (((byte_offset) >> 1) & 0x00ff))
    
    void asm_thumb_bcc_n(asm_thumb_t *as, int cond, int label) {
        int dest = get_label_dest(as, label);
        int rel = dest - as->code_offset;
        rel -= 4; // account for instruction prefetch, PC is 4 bytes ahead of this instruction
        if (SIGNED_FIT9(rel)) {
            asm_thumb_write_op16(as, OP_BCC_N(cond, rel));
        } else {
            printf("asm_thumb_bcc_n: branch does not fit in 9 bits\n");
        }
    }
    
    void asm_thumb_mov_reg_i32(asm_thumb_t *as, uint reg_dest, machine_uint_t i32) {
        // movw, movt does it in 8 bytes
        // ldr [pc, #], dw does it in 6 bytes, but we might not reach to end of code for dw
    
        asm_thumb_mov_reg_i16(as, OP_MOVW, reg_dest, i32);
        asm_thumb_mov_reg_i16(as, OP_MOVT, reg_dest, i32 >> 16);
    }
    
    void asm_thumb_mov_reg_i32_optimised(asm_thumb_t *as, uint reg_dest, int i32) {
        if (reg_dest < 8 && UNSIGNED_FIT8(i32)) {
            asm_thumb_movs_rlo_i8(as, reg_dest, i32);
        } else if (UNSIGNED_FIT16(i32)) {
            asm_thumb_mov_reg_i16(as, OP_MOVW, reg_dest, i32);
        } else {
            asm_thumb_mov_reg_i32(as, reg_dest, i32);
        }
    }
    
    #define OP_STR_TO_SP_OFFSET(rlo_dest, word_offset) (0x9000 | ((rlo_dest) << 8) | ((word_offset) & 0x00ff))
    #define OP_LDR_FROM_SP_OFFSET(rlo_dest, word_offset) (0x9800 | ((rlo_dest) << 8) | ((word_offset) & 0x00ff))
    
    void asm_thumb_mov_local_reg(asm_thumb_t *as, int local_num, uint rlo_src) {
        assert(rlo_src < REG_R8);
        int word_offset = as->num_locals - local_num - 1;
        assert(as->pass < ASM_THUMB_PASS_3 || word_offset >= 0);
        asm_thumb_write_op16(as, OP_STR_TO_SP_OFFSET(rlo_src, word_offset));
    }
    
    void asm_thumb_mov_reg_local(asm_thumb_t *as, uint rlo_dest, int local_num) {
        assert(rlo_dest < REG_R8);
        int word_offset = as->num_locals - local_num - 1;
        assert(as->pass < ASM_THUMB_PASS_3 || word_offset >= 0);
        asm_thumb_write_op16(as, OP_LDR_FROM_SP_OFFSET(rlo_dest, word_offset));
    }
    
    #define OP_ADD_REG_SP_OFFSET(rlo_dest, word_offset) (0xa800 | ((rlo_dest) << 8) | ((word_offset) & 0x00ff))
    
    void asm_thumb_mov_reg_local_addr(asm_thumb_t *as, uint rlo_dest, int local_num) {
        assert(rlo_dest < REG_R8);
        int word_offset = as->num_locals - local_num - 1;
        assert(as->pass < ASM_THUMB_PASS_3 || word_offset >= 0);
        asm_thumb_write_op16(as, OP_ADD_REG_SP_OFFSET(rlo_dest, word_offset));
    }
    
    // this could be wrong, because it should have a range of +/- 16MiB...
    #define OP_BW_HI(byte_offset) (0xf000 | (((byte_offset) >> 12) & 0x07ff))
    #define OP_BW_LO(byte_offset) (0xb800 | (((byte_offset) >> 1) & 0x07ff))
    
    void asm_thumb_b_label(asm_thumb_t *as, int label) {
        int dest = get_label_dest(as, label);
        int rel = dest - as->code_offset;
        rel -= 4; // account for instruction prefetch, PC is 4 bytes ahead of this instruction
        if (dest >= 0 && rel <= -4) {
            // is a backwards jump, so we know the size of the jump on the first pass
            // calculate rel assuming 12 bit relative jump
            if (SIGNED_FIT12(rel)) {
                asm_thumb_write_op16(as, OP_B_N(rel));
            } else {
                goto large_jump;
            }
        } else {
            // is a forwards jump, so need to assume it's large
            large_jump:
            asm_thumb_write_op32(as, OP_BW_HI(rel), OP_BW_LO(rel));
        }
    }
    
    // all these bit arithmetics need coverage testing!
    #define OP_BCC_W_HI(cond, byte_offset) (0xf000 | ((cond) << 6) | (((byte_offset) >> 10) & 0x0400) | (((byte_offset) >> 14) & 0x003f))
    #define OP_BCC_W_LO(byte_offset) (0x8000 | ((byte_offset) & 0x2000) | (((byte_offset) >> 1) & 0x0fff))
    
    void asm_thumb_bcc_label(asm_thumb_t *as, int cond, int label) {
        int dest = get_label_dest(as, label);
        int rel = dest - as->code_offset;
        rel -= 4; // account for instruction prefetch, PC is 4 bytes ahead of this instruction
        if (dest >= 0 && rel <= -4) {
            // is a backwards jump, so we know the size of the jump on the first pass
            // calculate rel assuming 9 bit relative jump
            if (SIGNED_FIT9(rel)) {
                asm_thumb_write_op16(as, OP_BCC_N(cond, rel));
            } else {
                goto large_jump;
            }
        } else {
            // is a forwards jump, so need to assume it's large
            large_jump:
            asm_thumb_write_op32(as, OP_BCC_W_HI(cond, rel), OP_BCC_W_LO(rel));
        }
    }
    
    #define OP_BLX(reg) (0x4780 | ((reg) << 3))
    #define OP_SVC(arg) (0xdf00 | (arg))
    #define OP_LDR_FROM_BASE_OFFSET(rlo_dest, rlo_base, word_offset) (0x6800 | (((word_offset) << 6) & 0x07c0) | ((rlo_base) << 3) | (rlo_dest))
    
    void asm_thumb_bl_ind(asm_thumb_t *as, void *fun_ptr, uint fun_id, uint reg_temp) {
        /* TODO make this use less bytes
        uint rlo_base = REG_R3;
        uint rlo_dest = REG_R7;
        uint word_offset = 4;
        asm_thumb_write_op16(as, 0x0000);
        asm_thumb_write_op16(as, 0x6800 | (word_offset << 6) | (rlo_base << 3) | rlo_dest); // ldr rlo_dest, [rlo_base, #offset]
        asm_thumb_write_op16(as, 0x4780 | (REG_R9 << 3)); // blx reg
        */
    
        if (0) {
            // load ptr to function into register using immediate, then branch
            // not relocatable
            asm_thumb_mov_reg_i32(as, reg_temp, (machine_uint_t)fun_ptr);
            asm_thumb_write_op16(as, OP_BLX(reg_temp));
        } else if (1) {
            asm_thumb_write_op16(as, OP_LDR_FROM_BASE_OFFSET(reg_temp, REG_R7, fun_id));
            asm_thumb_write_op16(as, OP_BLX(reg_temp));
        } else {
            // use SVC
            asm_thumb_write_op16(as, OP_SVC(fun_id));
        }
    }
    
    #endif // MICROPY_EMIT_THUMB || MICROPY_EMIT_INLINE_THUMB