tinycc/arm-asm.c

/*
 *  ARM specific functions for TCC assembler
 *
 *  Copyright (c) 2001, 2002 Fabrice Bellard
 *  Copyright (c) 2020 Danny Milosavljevic
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef TARGET_DEFS_ONLY

#define CONFIG_TCC_ASM
#define NB_ASM_REGS 16

ST_FUNC void g(int c);
ST_FUNC void gen_le16(int c);
ST_FUNC void gen_le32(int c);

/*************************************************************/
#else
/*************************************************************/

#define USING_GLOBALS
#include "tcc.h"

enum {
    OPT_REG32,
    OPT_REGSET32,
    OPT_IM8,
    OPT_IM8N,
    OPT_IM32,
};
#define OP_REG32  (1 << OPT_REG32)
#define OP_REG    (OP_REG32)
#define OP_IM32   (1 << OPT_IM32)
#define OP_IM8   (1 << OPT_IM8)
#define OP_IM8N   (1 << OPT_IM8N)
#define OP_REGSET32  (1 << OPT_REGSET32)

typedef struct Operand {
    uint32_t type;
    union {
        uint8_t reg;
        uint16_t regset;
        ExprValue e;
    };
} Operand;

/* Parse a text containing operand and store the result in OP */
static void parse_operand(TCCState *s1, Operand *op)
{
    ExprValue e;
    int8_t reg;
    uint16_t regset = 0;

    op->type = 0;

    if (tok == '{') { // regset literal
        next(); // skip '{'
        while (tok != '}' && tok != TOK_EOF) {
            reg = asm_parse_regvar(tok);
            if (reg == -1) {
                expect("register");
                return;
            } else
                next(); // skip register name

            if ((1 << reg) < regset)
                tcc_warning("registers will be processed in ascending order by hardware--but are not specified in ascending order here");
            regset |= 1 << reg;
            if (tok != ',')
                break;
            next(); // skip ','
        }
        if (tok != '}')
            expect("'}'");
        next(); // skip '}'
        if (regset == 0) {
            // ARM instructions don't support empty regset.
            tcc_error("empty register list is not supported");
        } else {
            op->type = OP_REGSET32;
            op->regset = regset;
        }
    } else if (tok == '#' || tok == '$') {
        /* constant value */
        next(); // skip '#' or '$'
        asm_expr(s1, &e);
        op->type = OP_IM32;
        op->e = e;
        if (!op->e.sym) {
            if ((int) op->e.v < 0 && (int) op->e.v >= -255)
                op->type = OP_IM8N;
            else if (op->e.v == (uint8_t)op->e.v)
                op->type = OP_IM8;
        } else
            expect("constant");
    } else if ((reg = asm_parse_regvar(tok)) != -1) {
        next(); // skip register name
        op->type = OP_REG32;
        op->reg = (uint8_t) reg;
    } else
        expect("operand");
}

/* XXX: make it faster ? */
ST_FUNC void g(int c)
{
    int ind1;
    if (nocode_wanted)
        return;
    ind1 = ind + 1;
    if (ind1 > cur_text_section->data_allocated)
        section_realloc(cur_text_section, ind1);
    cur_text_section->data[ind] = c;
    ind = ind1;
}

ST_FUNC void gen_le16 (int i)
{
    g(i);
    g(i>>8);
}

ST_FUNC void gen_le32 (int i)
{
    int ind1;
    if (nocode_wanted)
        return;
    ind1 = ind + 4;
    if (ind1 > cur_text_section->data_allocated)
        section_realloc(cur_text_section, ind1);
    cur_text_section->data[ind++] = i & 0xFF;
    cur_text_section->data[ind++] = (i >> 8) & 0xFF;
    cur_text_section->data[ind++] = (i >> 16) & 0xFF;
    cur_text_section->data[ind++] = (i >> 24) & 0xFF;
}

ST_FUNC void gen_expr32(ExprValue *pe)
{
    gen_le32(pe->v);
}

static uint32_t condition_code_of_token(int token) {
    if (token < TOK_ASM_nopeq) {
        expect("condition-enabled instruction");
        return 0;
    } else
        return (token - TOK_ASM_nopeq) & 15;
}

static void asm_emit_opcode(int token, uint32_t opcode) {
    gen_le32((condition_code_of_token(token) << 28) | opcode);
}

static void asm_emit_unconditional_opcode(uint32_t opcode) {
    gen_le32(opcode);
}

static void asm_emit_coprocessor_opcode(uint32_t high_nibble, uint8_t cp_number, uint8_t cp_opcode, uint8_t cp_destination_register, uint8_t cp_n_operand_register, uint8_t cp_m_operand_register, uint8_t cp_opcode2, int inter_processor_transfer)
{
    uint32_t opcode = 0xe000000;
    if (inter_processor_transfer)
        opcode |= 1 << 4;
    //assert(cp_opcode < 16);
    opcode |= cp_opcode << 20;
    //assert(cp_n_operand_register < 16);
    opcode |= cp_n_operand_register << 16;
    //assert(cp_destination_register < 16);
    opcode |= cp_destination_register << 12;
    //assert(cp_number < 16);
    opcode |= cp_number << 8;
    //assert(cp_information < 8);
    opcode |= cp_opcode2 << 5;
    //assert(cp_m_operand_register < 16);
    opcode |= cp_m_operand_register;
    asm_emit_unconditional_opcode((high_nibble << 28) | opcode);
}

static void asm_nullary_opcode(int token)
{
    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_nopeq:
        asm_emit_opcode(token, 0xd << 21); // mov r0, r0
        break;
    case TOK_ASM_wfeeq:
        asm_emit_opcode(token, 0x320f002);
    case TOK_ASM_wfieq:
        asm_emit_opcode(token, 0x320f003);
        break;
    default:
        expect("nullary instruction");
    }
}

static void asm_unary_opcode(TCCState *s1, int token)
{
    Operand op;
    parse_operand(s1, &op);

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_swieq:
        if (op.type != OP_IM8)
            expect("immediate 8-bit unsigned integer");
        else {
            /* Note: Dummy operand (ignored by processor): ARM ref documented 0...255, ARM instruction set documented 24 bit */
            asm_emit_opcode(token, (0xf << 24) | op.e.v);
        }
        break;
    default:
        expect("unary instruction");
    }
}

static void asm_binary_opcode(TCCState *s1, int token)
{
    Operand ops[2];
    Operand rotation;
    uint32_t encoded_rotation = 0;
    uint64_t amount;
    parse_operand(s1, &ops[0]);
    if (tok == ',')
        next();
    else
        expect("','");
    parse_operand(s1, &ops[1]);
    if (ops[0].type != OP_REG32) {
        expect("(destination operand) register");
        return;
    }

    if (ops[0].reg == 15) {
        tcc_error("'%s' does not support 'pc' as operand", get_tok_str(token, NULL));
        return;
    }

    if (ops[0].reg == 13)
        tcc_warning("Using 'sp' as operand with '%s' is deprecated by ARM", get_tok_str(token, NULL));

    if (ops[1].type != OP_REG32) {
        switch (ARM_INSTRUCTION_GROUP(token)) {
        case TOK_ASM_movteq:
        case TOK_ASM_movweq:
            if (ops[1].type == OP_IM8 || ops[1].type == OP_IM8N || ops[1].type == OP_IM32) {
                if (ops[1].e.v >= 0 && ops[1].e.v <= 0xFFFF) {
                    uint16_t immediate_value = ops[1].e.v;
                    switch (ARM_INSTRUCTION_GROUP(token)) {
                    case TOK_ASM_movteq:
                        asm_emit_opcode(token, 0x3400000 | (ops[0].reg << 12) | (immediate_value & 0xF000) << 4 | (immediate_value & 0xFFF));
                        break;
                    case TOK_ASM_movweq:
                        asm_emit_opcode(token, 0x3000000 | (ops[0].reg << 12) | (immediate_value & 0xF000) << 4 | (immediate_value & 0xFFF));
                        break;
                    }
                } else
                    expect("(source operand) immediate 16 bit value");
            } else
                expect("(source operand) immediate");
            break;
        default:
            expect("(source operand) register");
        }
        return;
    }

    if (ops[1].reg == 15) {
        tcc_error("'%s' does not support 'pc' as operand", get_tok_str(token, NULL));
        return;
    }

    if (ops[1].reg == 13)
        tcc_warning("Using 'sp' as operand with '%s' is deprecated by ARM", get_tok_str(token, NULL));

    if (tok == ',') {
        next(); // skip ','
        if (tok == TOK_ASM_ror) {
            next(); // skip 'ror'
            parse_operand(s1, &rotation);
            if (rotation.type != OP_IM8) {
                expect("immediate value for rotation");
                return;
            } else {
                amount = rotation.e.v;
                switch (amount) {
                case 8:
                    encoded_rotation = 1 << 10;
                    break;
                case 16:
                    encoded_rotation = 2 << 10;
                    break;
                case 24:
                    encoded_rotation = 3 << 10;
                    break;
                default:
                    expect("'8' or '16' or '24'");
                    return;
                }
            }
        }
    }
    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_clzeq:
        if (encoded_rotation)
            tcc_error("clz does not support rotation");
        asm_emit_opcode(token, 0x16f0f10 | (ops[0].reg << 12) | ops[1].reg);
        break;
    case TOK_ASM_sxtbeq:
        asm_emit_opcode(token, 0x6af0070 | (ops[0].reg << 12) | ops[1].reg | encoded_rotation);
        break;
    case TOK_ASM_sxtheq:
        asm_emit_opcode(token, 0x6bf0070 | (ops[0].reg << 12) | ops[1].reg | encoded_rotation);
        break;
    case TOK_ASM_uxtbeq:
        asm_emit_opcode(token, 0x6ef0070 | (ops[0].reg << 12) | ops[1].reg | encoded_rotation);
        break;
    case TOK_ASM_uxtheq:
        asm_emit_opcode(token, 0x6ff0070 | (ops[0].reg << 12) | ops[1].reg | encoded_rotation);
        break;
    default:
        expect("binary instruction");
    }
}

static void asm_coprocessor_opcode(TCCState *s1, int token) {
    uint8_t coprocessor;
    Operand opcode1;
    Operand opcode2;
    uint8_t registers[3];
    unsigned int i;
    uint8_t high_nibble;
    uint8_t mrc = 0;

    if (tok >= TOK_ASM_p0 && tok <= TOK_ASM_p15) {
        coprocessor = tok - TOK_ASM_p0;
        next();
    } else {
        expect("'p<number>'");
        return;
    }

    if (tok == ',')
        next();
    else
        expect("','");

    parse_operand(s1, &opcode1);
    if (opcode1.type != OP_IM8 || opcode1.e.v > 15) {
        tcc_error("opcode1 of instruction '%s' must be an immediate value between 0 and 15", get_tok_str(token, NULL));
        return;
    }

    for (i = 0; i < 3; ++i) {
        if (tok == ',')
            next();
        else
            expect("','");
        if (i == 0 && token != TOK_ASM_cdp2 && (ARM_INSTRUCTION_GROUP(token) == TOK_ASM_mrceq || ARM_INSTRUCTION_GROUP(token) == TOK_ASM_mcreq)) {
            if (tok >= TOK_ASM_r0 && tok <= TOK_ASM_r15) {
                registers[i] = tok - TOK_ASM_r0;
                next();
            } else {
                expect("'r<number>'");
                return;
            }
        } else {
            if (tok >= TOK_ASM_c0 && tok <= TOK_ASM_c15) {
                registers[i] = tok - TOK_ASM_c0;
                next();
            } else {
                expect("'c<number>'");
                return;
            }
        }
    }
    if (tok == ',') {
        next();
        parse_operand(s1, &opcode2);
    } else {
        opcode2.type = OP_IM8;
        opcode2.e.v = 0;
    }
    if (opcode2.type != OP_IM8 || opcode2.e.v > 15) {
        tcc_error("opcode2 of instruction '%s' must be an immediate value between 0 and 15", get_tok_str(token, NULL));
        return;
    }

    if (token == TOK_ASM_cdp2) {
        high_nibble = 0xF;
        asm_emit_coprocessor_opcode(high_nibble, coprocessor, opcode1.e.v, registers[0], registers[1], registers[2], opcode2.e.v, 0);
        return;
    } else
        high_nibble = condition_code_of_token(token);

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_cdpeq:
        asm_emit_coprocessor_opcode(high_nibble, coprocessor, opcode1.e.v, registers[0], registers[1], registers[2], opcode2.e.v, 0);
        break;
    case TOK_ASM_mrceq:
        // opcode1 encoding changes! highest and lowest bit gone.
        mrc = 1;
        /* fallthrough */
    case TOK_ASM_mcreq:
        // opcode1 encoding changes! highest and lowest bit gone.
        if (opcode1.e.v > 7) {
            tcc_error("opcode1 of instruction '%s' must be an immediate value between 0 and 7", get_tok_str(token, NULL));
            return;
        }
        asm_emit_coprocessor_opcode(high_nibble, coprocessor, (opcode1.e.v << 1) | mrc, registers[0], registers[1], registers[2], opcode2.e.v, 1);
        break;
    default:
        expect("known instruction");
    }
}

/* data processing and single data transfer instructions only */
#define ENCODE_RN(register_index) ((register_index) << 16)
#define ENCODE_RD(register_index) ((register_index) << 12)
#define ENCODE_SET_CONDITION_CODES (1 << 20)

/* Note: For data processing instructions, "1" means immediate.
   Note: For single data transfer instructions, "0" means immediate. */
#define ENCODE_IMMEDIATE_FLAG (1 << 25)

#define ENCODE_BARREL_SHIFTER_SHIFT_BY_REGISTER (1 << 4)
#define ENCODE_BARREL_SHIFTER_MODE_LSL (0 << 5)
#define ENCODE_BARREL_SHIFTER_MODE_LSR (1 << 5)
#define ENCODE_BARREL_SHIFTER_MODE_ASR (2 << 5)
#define ENCODE_BARREL_SHIFTER_MODE_ROR (3 << 5)
#define ENCODE_BARREL_SHIFTER_REGISTER(register_index) ((register_index) << 8)
#define ENCODE_BARREL_SHIFTER_IMMEDIATE(value) ((value) << 7)

static void asm_block_data_transfer_opcode(TCCState *s1, int token)
{
    uint32_t opcode;
    int op0_exclam = 0;
    Operand ops[2];
    int nb_ops = 1;
    parse_operand(s1, &ops[0]);
    if (tok == '!') {
        op0_exclam = 1;
        next(); // skip '!'
    }
    if (tok == ',') {
        next(); // skip comma
        parse_operand(s1, &ops[1]);
        ++nb_ops;
    }
    if (nb_ops < 1) {
        expect("at least one operand");
        return;
    } else if (ops[nb_ops - 1].type != OP_REGSET32) {
        expect("(last operand) register list");
        return;
    }

    // block data transfer: 1 0 0 P U S W L << 20 (general case):
    // operands:
    //   Rn: bits 19...16 base register
    //   Register List: bits 15...0

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_pusheq: // TODO: Optimize 1-register case to: str ?, [sp, #-4]!
        // Instruction: 1 I=0 P=1 U=0 S=0 W=1 L=0 << 20, op 1101
        //   operands:
        //      Rn: base register
        //      Register List: bits 15...0
        if (nb_ops != 1)
            expect("exactly one operand");
        else
            asm_emit_opcode(token, (0x92d << 16) | ops[0].regset); // TODO: base register ?
        break;
    case TOK_ASM_popeq: // TODO: Optimize 1-register case to: ldr ?, [sp], #4
        // Instruction: 1 I=0 P=0 U=1 S=0 W=0 L=1 << 20, op 1101
        //   operands:
        //      Rn: base register
        //      Register List: bits 15...0
        if (nb_ops != 1)
            expect("exactly one operand");
        else
            asm_emit_opcode(token, (0x8bd << 16) | ops[0].regset); // TODO: base register ?
        break;
    case TOK_ASM_stmdaeq:
    case TOK_ASM_ldmdaeq:
    case TOK_ASM_stmeq:
    case TOK_ASM_ldmeq:
    case TOK_ASM_stmiaeq:
    case TOK_ASM_ldmiaeq:
    case TOK_ASM_stmdbeq:
    case TOK_ASM_ldmdbeq:
    case TOK_ASM_stmibeq:
    case TOK_ASM_ldmibeq:
        switch (ARM_INSTRUCTION_GROUP(token)) {
        case TOK_ASM_stmdaeq: // post-decrement store
            opcode = 0x80 << 20;
            break;
        case TOK_ASM_ldmdaeq: // post-decrement load
            opcode = 0x81 << 20;
            break;
        case TOK_ASM_stmeq: // post-increment store
        case TOK_ASM_stmiaeq: // post-increment store
            opcode = 0x88 << 20;
            break;
        case TOK_ASM_ldmeq: // post-increment load
        case TOK_ASM_ldmiaeq: // post-increment load
            opcode = 0x89 << 20;
            break;
        case TOK_ASM_stmdbeq: // pre-decrement store
            opcode = 0x90 << 20;
            break;
        case TOK_ASM_ldmdbeq: // pre-decrement load
            opcode = 0x91 << 20;
            break;
        case TOK_ASM_stmibeq: // pre-increment store
            opcode = 0x98 << 20;
            break;
        case TOK_ASM_ldmibeq: // pre-increment load
            opcode = 0x99 << 20;
            break;
        default:
            tcc_error("internal error: This place should not be reached (fallback in asm_block_data_transfer_opcode)");
        }
        // operands:
        //    Rn: first operand
        //    Register List: lower bits
        if (nb_ops != 2)
            expect("exactly two operands");
        else if (ops[0].type != OP_REG32)
            expect("(first operand) register");
        else {
            if (op0_exclam)
                opcode |= 1 << 21; // writeback
            asm_emit_opcode(token, opcode | ENCODE_RN(ops[0].reg) | ops[1].regset);
        }
        break;
    default:
        expect("block data transfer instruction");
    }
}

/* Parses shift directive and returns the parts that would have to be set in the opcode because of it.
   Does not encode the actual shift amount.
   It's not an error if there is no shift directive.

   NB_SHIFT: will be set to 1 iff SHIFT is filled.  Note that for rrx, there's no need to fill SHIFT.
   SHIFT: will be filled in with the shift operand to use, if any. */
static uint32_t asm_parse_optional_shift(TCCState* s1, int* nb_shift, Operand* shift)
{
    uint32_t opcode = 0;
    *nb_shift = 0;
    switch (tok) {
    case TOK_ASM_asl:
    case TOK_ASM_lsl:
    case TOK_ASM_asr:
    case TOK_ASM_lsr:
    case TOK_ASM_ror:
        switch (tok) {
        case TOK_ASM_asl:
            /* fallthrough */
        case TOK_ASM_lsl:
            opcode = ENCODE_BARREL_SHIFTER_MODE_LSL;
            break;
        case TOK_ASM_asr:
            opcode = ENCODE_BARREL_SHIFTER_MODE_ASR;
            break;
        case TOK_ASM_lsr:
            opcode = ENCODE_BARREL_SHIFTER_MODE_LSR;
            break;
        case TOK_ASM_ror:
            opcode = ENCODE_BARREL_SHIFTER_MODE_ROR;
            break;
        }
        next();
        parse_operand(s1, shift);
        *nb_shift = 1;
        break;
    case TOK_ASM_rrx:
        next();
        opcode = ENCODE_BARREL_SHIFTER_MODE_ROR;
        break;
    }
    return opcode;
}

static uint32_t asm_encode_shift(Operand* shift)
{
    uint64_t amount;
    uint32_t operands = 0;
    switch (shift->type) {
    case OP_REG32:
        if (shift->reg == 15)
            tcc_error("r15 cannot be used as a shift count");
        else {
            operands = ENCODE_BARREL_SHIFTER_SHIFT_BY_REGISTER;
            operands |= ENCODE_BARREL_SHIFTER_REGISTER(shift->reg);
        }
        break;
    case OP_IM8:
        amount = shift->e.v;
        if (amount > 0 && amount < 32)
            operands = ENCODE_BARREL_SHIFTER_IMMEDIATE(amount);
        else
            tcc_error("shift count out of range");
        break;
    default:
        tcc_error("unknown shift amount");
    }
    return operands;
}

static void asm_data_processing_opcode(TCCState *s1, int token)
{
    Operand ops[3];
    int nb_ops;
    Operand shift = {};
    int nb_shift = 0;
    uint32_t operands = 0;

    /* modulo 16 entries per instruction for the different condition codes */
    uint32_t opcode_idx = (ARM_INSTRUCTION_GROUP(token) - TOK_ASM_andeq) >> 4;
    uint32_t opcode_nos = opcode_idx >> 1; // without "s"; "OpCode" in ARM docs

    for (nb_ops = 0; nb_ops < sizeof(ops)/sizeof(ops[0]); ) {
        if (tok == TOK_ASM_asl || tok == TOK_ASM_lsl || tok == TOK_ASM_lsr || tok == TOK_ASM_asr || tok == TOK_ASM_ror || tok == TOK_ASM_rrx)
            break;
        parse_operand(s1, &ops[nb_ops]);
        ++nb_ops;
        if (tok != ',')
            break;
        next(); // skip ','
    }
    if (tok == ',')
        next();
    operands |= asm_parse_optional_shift(s1, &nb_shift, &shift);
    if (nb_ops < 2)
        expect("at least two operands");
    else if (nb_ops == 2) {
        memcpy(&ops[2], &ops[1], sizeof(ops[1])); // move ops[2]
        memcpy(&ops[1], &ops[0], sizeof(ops[0])); // ops[1] was implicit
        nb_ops = 3;
    } else if (nb_ops == 3) {
        if (opcode_nos == 0xd || opcode_nos == 0xf || opcode_nos == 0xa || opcode_nos == 0xb || opcode_nos == 0x8 || opcode_nos == 0x9) { // mov, mvn, cmp, cmn, tst, teq
            tcc_error("'%s' cannot be used with three operands", get_tok_str(token, NULL));
            return;
        }
    }
    if (nb_ops != 3) {
        expect("two or three operands");
        return;
    } else {
        uint32_t opcode = 0;
        uint32_t immediate_value;
        uint8_t half_immediate_rotation;
        if (nb_shift && shift.type == OP_REG32) {
            if ((ops[0].type == OP_REG32 && ops[0].reg == 15) ||
                (ops[1].type == OP_REG32 && ops[1].reg == 15)) {
                tcc_error("Using the 'pc' register in data processing instructions that have a register-controlled shift is not implemented by ARM");
                return;
            }
        }

        // data processing (general case):
        // operands:
        //   Rn: bits 19...16 (first operand)
        //   Rd: bits 15...12 (destination)
        //   Operand2: bits 11...0 (second operand);  depending on I that's either a register or an immediate
        // operator:
        //   bits 24...21: "OpCode"--see below

        /* operations in the token list are ordered by opcode */
        opcode = opcode_nos << 21; // drop "s"
        if (ops[0].type != OP_REG32)
            expect("(destination operand) register");
        else if (opcode_nos == 0xa || opcode_nos == 0xb || opcode_nos == 0x8 || opcode_nos == 0x9) // cmp, cmn, tst, teq
            operands |= ENCODE_SET_CONDITION_CODES; // force S set, otherwise it's a completely different instruction.
        else
            operands |= ENCODE_RD(ops[0].reg);
        if (ops[1].type != OP_REG32)
            expect("(first source operand) register");
        else if (!(opcode_nos == 0xd || opcode_nos == 0xf)) // not: mov, mvn (those have only one source operand)
            operands |= ENCODE_RN(ops[1].reg);
        switch (ops[2].type) {
        case OP_REG32:
            operands |= ops[2].reg;
            break;
        case OP_IM8:
        case OP_IM32:
            operands |= ENCODE_IMMEDIATE_FLAG;
            immediate_value = ops[2].e.v;
            for (half_immediate_rotation = 0; half_immediate_rotation < 16; ++half_immediate_rotation) {
                if (immediate_value >= 0x00 && immediate_value < 0x100)
                    break;
                // rotate left by two
                immediate_value = ((immediate_value & 0x3FFFFFFF) << 2) | ((immediate_value & 0xC0000000) >> 30);
            }
            if (half_immediate_rotation >= 16) {
                /* fallthrough */
            } else {
                operands |= immediate_value;
                operands |= half_immediate_rotation << 8;
                break;
            }
        case OP_IM8N: // immediate negative value
            operands |= ENCODE_IMMEDIATE_FLAG;
            immediate_value = ops[2].e.v;
            /* Instruction swapping:
               0001 = EOR - Rd:= Op1 EOR Op2     -> difficult
               0011 = RSB - Rd:= Op2 - Op1       -> difficult
               0111 = RSC - Rd:= Op2 - Op1 + C   -> difficult
               1000 = TST - CC on: Op1 AND Op2   -> difficult
               1001 = TEQ - CC on: Op1 EOR Op2   -> difficult
               1100 = ORR - Rd:= Op1 OR Op2      -> difficult
            */
            switch (opcode_nos) {
            case 0x0: // AND - Rd:= Op1 AND Op2
                opcode = 0xe << 21; // BIC
                immediate_value = ~immediate_value;
                break;
            case 0x2: // SUB - Rd:= Op1 - Op2
                opcode = 0x4 << 21; // ADD
                immediate_value = -immediate_value;
                break;
            case 0x4: // ADD - Rd:= Op1 + Op2
                opcode = 0x2 << 21; // SUB
                immediate_value = -immediate_value;
                break;
            case 0x5: // ADC - Rd:= Op1 + Op2 + C
                opcode = 0x6 << 21; // SBC
                immediate_value = ~immediate_value;
                break;
            case 0x6: // SBC - Rd:= Op1 - Op2 + C
                opcode = 0x5 << 21; // ADC
                immediate_value = ~immediate_value;
                break;
            case 0xa: // CMP - CC on: Op1 - Op2
                opcode = 0xb << 21; // CMN
                immediate_value = -immediate_value;
                break;
            case 0xb: // CMN - CC on: Op1 + Op2
                opcode = 0xa << 21; // CMP
                immediate_value = -immediate_value;
                break;
            case 0xd: // MOV - Rd:= Op2
                opcode = 0xf << 21; // MVN
                immediate_value = ~immediate_value;
                break;
            case 0xe: // BIC - Rd:= Op1 AND NOT Op2
                opcode = 0x0 << 21; // AND
                immediate_value = ~immediate_value;
                break;
            case 0xf: // MVN - Rd:= NOT Op2
                opcode = 0xd << 21; // MOV
                immediate_value = ~immediate_value;
                break;
            default:
                tcc_error("cannot use '%s' with a negative immediate value", get_tok_str(token, NULL));
            }
            for (half_immediate_rotation = 0; half_immediate_rotation < 16; ++half_immediate_rotation) {
                if (immediate_value >= 0x00 && immediate_value < 0x100)
                    break;
                // rotate left by two
                immediate_value = ((immediate_value & 0x3FFFFFFF) << 2) | ((immediate_value & 0xC0000000) >> 30);
            }
            if (half_immediate_rotation >= 16) {
                immediate_value = ops[2].e.v;
                tcc_error("immediate value 0x%X cannot be encoded into ARM immediate", (unsigned) immediate_value);
                return;
            }
            operands |= immediate_value;
            operands |= half_immediate_rotation << 8;
            break;
        default:
            expect("(second source operand) register or immediate value");
        }

        if (nb_shift) {
            if (operands & ENCODE_IMMEDIATE_FLAG)
                tcc_error("immediate rotation not implemented");
            else
                operands |= asm_encode_shift(&shift);
        }

        /* S=0 and S=1 entries alternate one after another, in that order */
        opcode |= (opcode_idx & 1) ? ENCODE_SET_CONDITION_CODES : 0;
        asm_emit_opcode(token, opcode | operands);
    }
}

static void asm_shift_opcode(TCCState *s1, int token)
{
    Operand ops[3];
    int nb_ops;
    int definitely_neutral = 0;
    uint32_t opcode = 0xd << 21; // MOV
    uint32_t operands = 0;

    for (nb_ops = 0; nb_ops < sizeof(ops)/sizeof(ops[0]); ++nb_ops) {
        parse_operand(s1, &ops[nb_ops]);
        if (tok != ',') {
            ++nb_ops;
            break;
        }
        next(); // skip ','
    }
    if (nb_ops < 2) {
        expect("at least two operands");
        return;
    }

    if (ops[0].type != OP_REG32) {
        expect("(destination operand) register");
        return;
    } else
        operands |= ENCODE_RD(ops[0].reg);

    if (nb_ops == 2) {
        switch (ARM_INSTRUCTION_GROUP(token)) {
        case TOK_ASM_rrxseq:
            opcode |= ENCODE_SET_CONDITION_CODES;
            /* fallthrough */
        case TOK_ASM_rrxeq:
            if (ops[1].type == OP_REG32) {
                operands |= ops[1].reg;
                operands |= ENCODE_BARREL_SHIFTER_MODE_ROR;
                asm_emit_opcode(token, opcode | operands);
            } else
                tcc_error("(first source operand) register");
            return;
        default:
            memcpy(&ops[2], &ops[1], sizeof(ops[1])); // move ops[2]
            memcpy(&ops[1], &ops[0], sizeof(ops[0])); // ops[1] was implicit
            nb_ops = 3;
        }
    }
    if (nb_ops != 3) {
        expect("two or three operands");
        return;
    }

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_lslseq:
    case TOK_ASM_lsrseq:
    case TOK_ASM_asrseq:
    case TOK_ASM_rorseq:
        opcode |= ENCODE_SET_CONDITION_CODES;
        break;
    }

    switch (ops[1].type) {
    case OP_REG32:
        operands |= ops[1].reg;
        break;
    case OP_IM8:
        operands |= ENCODE_IMMEDIATE_FLAG;
        operands |= ops[1].e.v;
        break;
    }

    switch (ops[2].type) {
    case OP_REG32:
        if ((ops[0].type == OP_REG32 && ops[0].reg == 15) ||
            (ops[1].type == OP_REG32 && ops[1].reg == 15)) {
            tcc_error("Using the 'pc' register in data processing instructions that have a register-controlled shift is not implemented by ARM");
        }
        operands |= asm_encode_shift(&ops[2]);
        break;
    case OP_IM8:
        if (ops[2].e.v)
            operands |= asm_encode_shift(&ops[2]);
        else
            definitely_neutral = 1;
        break;
    }

    if (!definitely_neutral) switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_lslseq:
    case TOK_ASM_lsleq:
        operands |= ENCODE_BARREL_SHIFTER_MODE_LSL;
        break;
    case TOK_ASM_lsrseq:
    case TOK_ASM_lsreq:
        operands |= ENCODE_BARREL_SHIFTER_MODE_LSR;
        break;
    case TOK_ASM_asrseq:
    case TOK_ASM_asreq:
        operands |= ENCODE_BARREL_SHIFTER_MODE_ASR;
        break;
    case TOK_ASM_rorseq:
    case TOK_ASM_roreq:
        operands |= ENCODE_BARREL_SHIFTER_MODE_ROR;
        break;
    default:
        expect("shift instruction");
        return;
    }
    asm_emit_opcode(token, opcode | operands);
}

static void asm_multiplication_opcode(TCCState *s1, int token)
{
    Operand ops[4];
    int nb_ops = 0;
    uint32_t opcode = 0x90;

    for (nb_ops = 0; nb_ops < sizeof(ops)/sizeof(ops[0]); ++nb_ops) {
        parse_operand(s1, &ops[nb_ops]);
        if (tok != ',') {
            ++nb_ops;
            break;
        }
        next(); // skip ','
    }
    if (nb_ops < 2)
        expect("at least two operands");
    else if (nb_ops == 2) {
        switch (ARM_INSTRUCTION_GROUP(token)) {
        case TOK_ASM_mulseq:
        case TOK_ASM_muleq:
            memcpy(&ops[2], &ops[0], sizeof(ops[1])); // ARM is actually like this!
            break;
        default:
            expect("at least three operands");
            return;
        }
        nb_ops = 3;
    }

    // multiply (special case):
    // operands:
    //   Rd: bits 19...16
    //   Rm: bits 3...0
    //   Rs: bits 11...8
    //   Rn: bits 15...12

    if (ops[0].type == OP_REG32)
        opcode |= ops[0].reg << 16;
    else
        expect("(destination operand) register");
    if (ops[1].type == OP_REG32)
        opcode |= ops[1].reg;
    else
        expect("(first source operand) register");
    if (ops[2].type == OP_REG32)
        opcode |= ops[2].reg << 8;
    else
        expect("(second source operand) register");
    if (nb_ops > 3) {
        if (ops[3].type == OP_REG32)
            opcode |= ops[3].reg << 12;
        else
            expect("(third source operand) register");
    }

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_mulseq:
        opcode |= 1 << 20; // Status
        /* fallthrough */
    case TOK_ASM_muleq:
        if (nb_ops != 3)
            expect("three operands");
        else {
            asm_emit_opcode(token, opcode);
        }
        break;
    case TOK_ASM_mlaseq:
        opcode |= 1 << 20; // Status
        /* fallthrough */
    case TOK_ASM_mlaeq:
        if (nb_ops != 4)
            expect("four operands");
        else {
            opcode |= 1 << 21; // Accumulate
            asm_emit_opcode(token, opcode);
        }
        break;
    default:
        expect("known multiplication instruction");
    }
}

static void asm_long_multiplication_opcode(TCCState *s1, int token)
{
    Operand ops[4];
    int nb_ops = 0;
    uint32_t opcode = 0x90 | (1 << 23);

    for (nb_ops = 0; nb_ops < sizeof(ops)/sizeof(ops[0]); ++nb_ops) {
        parse_operand(s1, &ops[nb_ops]);
        if (tok != ',') {
            ++nb_ops;
            break;
        }
        next(); // skip ','
    }
    if (nb_ops != 4) {
        expect("four operands");
        return;
    }

    // long multiply (special case):
    // operands:
    //   RdLo: bits 15...12
    //   RdHi: bits 19...16
    //   Rs: bits 11...8
    //   Rm: bits 3...0

    if (ops[0].type == OP_REG32)
        opcode |= ops[0].reg << 12;
    else
        expect("(destination lo accumulator) register");
    if (ops[1].type == OP_REG32)
        opcode |= ops[1].reg << 16;
    else
        expect("(destination hi accumulator) register");
    if (ops[2].type == OP_REG32)
        opcode |= ops[2].reg;
    else
        expect("(first source operand) register");
    if (ops[3].type == OP_REG32)
        opcode |= ops[3].reg << 8;
    else
        expect("(second source operand) register");

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_smullseq:
        opcode |= 1 << 20; // Status
        /* fallthrough */
    case TOK_ASM_smulleq:
        opcode |= 1 << 22; // signed
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_umullseq:
        opcode |= 1 << 20; // Status
        /* fallthrough */
    case TOK_ASM_umulleq:
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_smlalseq:
        opcode |= 1 << 20; // Status
        /* fallthrough */
    case TOK_ASM_smlaleq:
        opcode |= 1 << 22; // signed
        opcode |= 1 << 21; // Accumulate
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_umlalseq:
        opcode |= 1 << 20; // Status
        /* fallthrough */
    case TOK_ASM_umlaleq:
        opcode |= 1 << 21; // Accumulate
        asm_emit_opcode(token, opcode);
        break;
    default:
        expect("known long multiplication instruction");
    }
}

static void asm_single_data_transfer_opcode(TCCState *s1, int token)
{
    Operand ops[3];
    Operand strex_operand;
    Operand shift;
    int nb_shift = 0;
    int exclam = 0;
    int closed_bracket = 0;
    int op2_minus = 0;
    uint32_t opcode = 0;
    // Note: ldr r0, [r4, #4]  ; simple offset: r0 = *(int*)(r4+4); r4 unchanged
    // Note: ldr r0, [r4, #4]! ; pre-indexed:   r0 = *(int*)(r4+4); r4 = r4+4
    // Note: ldr r0, [r4], #4  ; post-indexed:  r0 = *(int*)(r4+0); r4 = r4+4

    parse_operand(s1, &ops[0]);
    if (ops[0].type == OP_REG32)
        opcode |= ENCODE_RD(ops[0].reg);
    else {
        expect("(destination operand) register");
        return;
    }
    if (tok != ',')
        expect("at least two arguments");
    else
        next(); // skip ','

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_strexbeq:
    case TOK_ASM_strexeq:
        parse_operand(s1, &strex_operand);
        if (strex_operand.type != OP_REG32) {
            expect("register");
            return;
        }
        if (tok != ',')
            expect("at least three arguments");
        else
            next(); // skip ','
        break;
    }

    if (tok != '[')
        expect("'['");
    else
        next(); // skip '['

    parse_operand(s1, &ops[1]);
    if (ops[1].type == OP_REG32)
        opcode |= ENCODE_RN(ops[1].reg);
    else {
        expect("(first source operand) register");
        return;
    }
    if (tok == ']') {
        next();
        closed_bracket = 1;
        // exclam = 1; // implicit in hardware; don't do it in software
    }
    if (tok == ',') {
        next(); // skip ','
        if (tok == '-') {
            op2_minus = 1;
            next();
        }
        parse_operand(s1, &ops[2]);
        if (ops[2].type == OP_REG32) {
            if (ops[2].reg == 15) {
                tcc_error("Using 'pc' for register offset in '%s' is not implemented by ARM", get_tok_str(token, NULL));
                return;
            }
            if (tok == ',') {
                next();
                opcode |= asm_parse_optional_shift(s1, &nb_shift, &shift);
                if (opcode == 0)
                    expect("shift directive, or no comma");
            }
        }
    } else {
        // end of input expression in brackets--assume 0 offset
        ops[2].type = OP_IM8;
        ops[2].e.v = 0;
        opcode |= 1 << 24; // add offset before transfer
    }
    if (!closed_bracket) {
        if (tok != ']')
            expect("']'");
        else
            next(); // skip ']'
        opcode |= 1 << 24; // add offset before transfer
        if (tok == '!') {
            exclam = 1;
            next(); // skip '!'
        }
    }

    // single data transfer: 0 1 I P U B W L << 20 (general case):
    // operands:
    //    Rd: destination operand [ok]
    //    Rn: first source operand [ok]
    //    Operand2: bits 11...0 [ok]
    // I: immediate operand? [ok]
    // P: Pre/post indexing is PRE: Add offset before transfer [ok]
    // U: Up/down is up? (*adds* offset to base) [ok]
    // B: Byte/word is byte?  TODO
    // W: Write address back into base? [ok]
    // L: Load/store is load? [ok]
    if (exclam)
        opcode |= 1 << 21; // write offset back into register

    if (ops[2].type == OP_IM32 || ops[2].type == OP_IM8 || ops[2].type == OP_IM8N) {
        int v = ops[2].e.v;
        if (op2_minus)
            tcc_error("minus before '#' not supported for immediate values");
        if (v >= 0) {
            opcode |= 1 << 23; // up
            if (v >= 0x1000)
                tcc_error("offset out of range for '%s'", get_tok_str(token, NULL));
            else
                opcode |= v;
        } else { // down
            if (v <= -0x1000)
                tcc_error("offset out of range for '%s'", get_tok_str(token, NULL));
            else
                opcode |= -v;
        }
    } else if (ops[2].type == OP_REG32) {
        if (!op2_minus)
            opcode |= 1 << 23; // up
        opcode |= ENCODE_IMMEDIATE_FLAG; /* if set, it means it's NOT immediate */
        opcode |= ops[2].reg;
    } else
        expect("register");

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_strbeq:
        opcode |= 1 << 22; // B
        /* fallthrough */
    case TOK_ASM_streq:
        opcode |= 1 << 26; // Load/Store
        if (nb_shift)
            opcode |= asm_encode_shift(&shift);
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_ldrbeq:
        opcode |= 1 << 22; // B
        /* fallthrough */
    case TOK_ASM_ldreq:
        opcode |= 1 << 20; // L
        opcode |= 1 << 26; // Load/Store
        if (nb_shift)
            opcode |= asm_encode_shift(&shift);
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_strexbeq:
        opcode |= 1 << 22; // B
        /* fallthrough */
    case TOK_ASM_strexeq:
        if ((opcode & 0xFFF) || nb_shift) {
            tcc_error("neither offset nor shift allowed with 'strex'");
            return;
        } else if (opcode & ENCODE_IMMEDIATE_FLAG) { // if set, it means it's NOT immediate
            tcc_error("offset not allowed with 'strex'");
            return;
        }
        if ((opcode & (1 << 24)) == 0) { // add offset after transfer
            tcc_error("adding offset after transfer not allowed with 'strex'");
            return;
        }

        opcode |= 0xf90; // Used to mean: barrel shifter is enabled, barrel shift register is r15, mode is LSL
        opcode |= strex_operand.reg;
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_ldrexbeq:
        opcode |= 1 << 22; // B
        /* fallthrough */
    case TOK_ASM_ldrexeq:
        if ((opcode & 0xFFF) || nb_shift) {
            tcc_error("neither offset nor shift allowed with 'ldrex'");
            return;
        } else if (opcode & ENCODE_IMMEDIATE_FLAG) { // if set, it means it's NOT immediate
            tcc_error("offset not allowed with 'ldrex'");
            return;
        }
        if ((opcode & (1 << 24)) == 0) { // add offset after transfer
            tcc_error("adding offset after transfer not allowed with 'ldrex'");
            return;
        }
        opcode |= 1 << 20; // L
        opcode |= 0x00f;
        opcode |= 0xf90; // Used to mean: barrel shifter is enabled, barrel shift register is r15, mode is LSL
        asm_emit_opcode(token, opcode);
        break;
    default:
        expect("data transfer instruction");
    }
}

static void asm_emit_coprocessor_data_transfer(uint32_t high_nibble, uint8_t cp_number, uint8_t CRd, const Operand* Rn, const Operand* offset, int offset_minus, int preincrement, int writeback, int long_transfer, int load) {
    uint32_t opcode = 0x0;
    opcode |= 1 << 26; // Load/Store
    opcode |= 1 << 27; // coprocessor

    if (long_transfer)
        opcode |= 1 << 22; // long transfer

    if (load)
        opcode |= 1 << 20; // L

    opcode |= cp_number << 8;

    opcode |= ENCODE_RD(CRd);

    if (Rn->type != OP_REG32) {
        expect("register");
        return;
    }
    opcode |= ENCODE_RN(Rn->reg);
    if (preincrement)
        opcode |= 1 << 24; // add offset before transfer

    if (writeback)
        opcode |= 1 << 21; // write offset back into register

    if (offset->type == OP_IM8 || offset->type == OP_IM8N || offset->type == OP_IM32) {
        int v = offset->e.v;
        if (offset_minus)
            tcc_error("minus before '#' not supported for immediate values");
        if (offset->type == OP_IM8N || v < 0)
            v = -v;
        else
            opcode |= 1 << 23; // up
        if (v & 3) {
            tcc_error("immediate offset must be a multiple of 4");
            return;
        }
        v >>= 2;
        if (v > 255) {
            tcc_error("immediate offset must be between -1020 and 1020");
            return;
        }
        opcode |= v;
    } else if (offset->type == OP_REG32) {
        if (!offset_minus)
            opcode |= 1 << 23; // up
        opcode |= ENCODE_IMMEDIATE_FLAG; /* if set, it means it's NOT immediate */
        opcode |= offset->reg;
        tcc_error("Using register offset to register address is not possible here");
        return;
    } else
        expect("immediate or register");

    asm_emit_unconditional_opcode((high_nibble << 28) | opcode);
}

// Almost exactly the same as asm_single_data_transfer_opcode.
// Difference: Offsets are smaller and multiples of 4; no shifts, no STREX, ENCODE_IMMEDIATE_FLAG is inverted again.
static void asm_coprocessor_data_transfer_opcode(TCCState *s1, int token)
{
    Operand ops[3];
    uint8_t coprocessor;
    uint8_t coprocessor_destination_register;
    int preincrement = 0;
    int exclam = 0;
    int closed_bracket = 0;
    int op2_minus = 0;
    int long_transfer = 0;
    // Note: ldc p1, c0, [r4, #4]  ; simple offset: r0 = *(int*)(r4+4); r4 unchanged
    // Note: ldc p2, c0, [r4, #4]! ; pre-indexed:   r0 = *(int*)(r4+4); r4 = r4+4
    // Note: ldc p3, c0, [r4], #4  ; post-indexed:  r0 = *(int*)(r4+0); r4 = r4+4

    if (tok >= TOK_ASM_p0 && tok <= TOK_ASM_p15) {
        coprocessor = tok - TOK_ASM_p0;
        next();
    } else {
        expect("'c<number>'");
        return;
    }

    if (tok == ',')
        next();
    else
        expect("','");

    if (tok >= TOK_ASM_c0 && tok <= TOK_ASM_c15) {
        coprocessor_destination_register = tok - TOK_ASM_c0;
        next();
    } else {
        expect("'c<number>'");
        return;
    }

    if (tok == ',')
        next();
    else
        expect("','");

    if (tok != '[')
        expect("'['");
    else
        next(); // skip '['

    parse_operand(s1, &ops[1]);
    if (ops[1].type != OP_REG32) {
        expect("(first source operand) register");
        return;
    }
    if (tok == ']') {
        next();
        closed_bracket = 1;
        // exclam = 1; // implicit in hardware; don't do it in software
    }
    if (tok == ',') {
        next(); // skip ','
        if (tok == '-') {
            op2_minus = 1;
            next();
        }
        parse_operand(s1, &ops[2]);
        if (ops[2].type == OP_REG32) {
            if (ops[2].reg == 15) {
                tcc_error("Using 'pc' for register offset in '%s' is not implemented by ARM", get_tok_str(token, NULL));
                return;
            }
        }
    } else {
        // end of input expression in brackets--assume 0 offset
        ops[2].type = OP_IM8;
        ops[2].e.v = 0;
        preincrement = 1; // add offset before transfer
    }
    if (!closed_bracket) {
        if (tok != ']')
            expect("']'");
        else
            next(); // skip ']'
        preincrement = 1; // add offset before transfer
        if (tok == '!') {
            exclam = 1;
            next(); // skip '!'
        }
    }

    // TODO: Support options.

    if (token == TOK_ASM_ldc2 || token == TOK_ASM_stc2 || token == TOK_ASM_ldc2l || token == TOK_ASM_stc2l) {
        switch (token) {
        case TOK_ASM_ldc2l:
            long_transfer = 1; // long transfer
            /* fallthrough */
        case TOK_ASM_ldc2:
            asm_emit_coprocessor_data_transfer(0xF, coprocessor, coprocessor_destination_register, &ops[1], &ops[2], op2_minus, preincrement, exclam, long_transfer, 1);
            break;
        case TOK_ASM_stc2l:
            long_transfer = 1; // long transfer
            /* fallthrough */
        case TOK_ASM_stc2:
            asm_emit_coprocessor_data_transfer(0xF, coprocessor, coprocessor_destination_register, &ops[1], &ops[2], op2_minus, preincrement, exclam, long_transfer, 0);
            break;
        }
    } else switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_stcleq:
        long_transfer = 1;
        /* fallthrough */
    case TOK_ASM_stceq:
        asm_emit_coprocessor_data_transfer(condition_code_of_token(token), coprocessor, coprocessor_destination_register, &ops[1], &ops[2], op2_minus, preincrement, exclam, long_transfer, 0);
        break;
    case TOK_ASM_ldcleq:
        long_transfer = 1;
        /* fallthrough */
    case TOK_ASM_ldceq:
        asm_emit_coprocessor_data_transfer(condition_code_of_token(token), coprocessor, coprocessor_destination_register, &ops[1], &ops[2], op2_minus, preincrement, exclam, long_transfer, 1);
        break;
    default:
        expect("coprocessor data transfer instruction");
    }
}

static void asm_misc_single_data_transfer_opcode(TCCState *s1, int token)
{
    Operand ops[3];
    int exclam = 0;
    int closed_bracket = 0;
    int op2_minus = 0;
    uint32_t opcode = (1 << 7) | (1 << 4);

    /* Note:
       The argument syntax is exactly the same as in arm_single_data_transfer_opcode, except that there's no STREX argument form.
       The main difference between this function and asm_misc_single_data_transfer_opcode is that the immediate values here must be smaller.
       Also, the combination (P=0, W=1) is unpredictable here.
       The immediate flag has moved to bit index 22--and its meaning has flipped.
       The immediate value itself has been split into two parts: one at bits 11...8, one at bits 3...0
       bit 26 (Load/Store instruction) is unset here.
       bits 7 and 4 are set here. */

    // Here: 0 0 0 P U I W L << 20
    // [compare single data transfer: 0 1 I P U B W L << 20]

    parse_operand(s1, &ops[0]);
    if (ops[0].type == OP_REG32)
        opcode |= ENCODE_RD(ops[0].reg);
    else {
        expect("(destination operand) register");
        return;
    }
    if (tok != ',')
        expect("at least two arguments");
    else
        next(); // skip ','

    if (tok != '[')
        expect("'['");
    else
        next(); // skip '['

    parse_operand(s1, &ops[1]);
    if (ops[1].type == OP_REG32)
        opcode |= ENCODE_RN(ops[1].reg);
    else {
        expect("(first source operand) register");
        return;
    }
    if (tok == ']') {
        next();
        closed_bracket = 1;
        // exclam = 1; // implicit in hardware; don't do it in software
    }
    if (tok == ',') {
        next(); // skip ','
        if (tok == '-') {
            op2_minus = 1;
            next();
        }
        parse_operand(s1, &ops[2]);
    } else {
        // end of input expression in brackets--assume 0 offset
        ops[2].type = OP_IM8;
        ops[2].e.v = 0;
        opcode |= 1 << 24; // add offset before transfer
    }
    if (!closed_bracket) {
        if (tok != ']')
            expect("']'");
        else
            next(); // skip ']'
        opcode |= 1 << 24; // add offset before transfer
        if (tok == '!') {
            exclam = 1;
            next(); // skip '!'
        }
    }

    if (exclam) {
        if ((opcode & (1 << 24)) == 0) {
            tcc_error("result of '%s' would be unpredictable here", get_tok_str(token, NULL));
            return;
        }
        opcode |= 1 << 21; // write offset back into register
    }

    if (ops[2].type == OP_IM32 || ops[2].type == OP_IM8 || ops[2].type == OP_IM8N) {
        int v = ops[2].e.v;
        if (op2_minus)
            tcc_error("minus before '#' not supported for immediate values");
        if (v >= 0) {
            opcode |= 1 << 23; // up
            if (v >= 0x100)
                tcc_error("offset out of range for '%s'", get_tok_str(token, NULL));
            else {
                // bits 11...8: immediate hi nibble
                // bits 3...0: immediate lo nibble
                opcode |= (v & 0xF0) << 4;
                opcode |= v & 0xF;
            }
        } else { // down
            if (v <= -0x100)
                tcc_error("offset out of range for '%s'", get_tok_str(token, NULL));
            else {
                v = -v;
                // bits 11...8: immediate hi nibble
                // bits 3...0: immediate lo nibble
                opcode |= (v & 0xF0) << 4;
                opcode |= v & 0xF;
            }
        }
        opcode |= 1 << 22; // not ENCODE_IMMEDIATE_FLAG;
    } else if (ops[2].type == OP_REG32) {
        if (!op2_minus)
            opcode |= 1 << 23; // up
        opcode |= ops[2].reg;
    } else
        expect("register");

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_ldrsheq:
        opcode |= 1 << 5; // halfword, not byte
        /* fallthrough */
    case TOK_ASM_ldrsbeq:
        opcode |= 1 << 6; // sign extend
        opcode |= 1 << 20; // L
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_ldrheq:
        opcode |= 1 << 5; // halfword, not byte
        opcode |= 1 << 20; // L
        asm_emit_opcode(token, opcode);
        break;
    case TOK_ASM_strheq:
        opcode |= 1 << 5; // halfword, not byte
        asm_emit_opcode(token, opcode);
        break;
    }
}

/* Note: almost dupe of encbranch in arm-gen.c */
static uint32_t encbranchoffset(int pos, int addr, int fail)
{
  addr-=pos+8;
  addr/=4;
  if(addr>=0x7fffff || addr<-0x800000) {
    if(fail)
      tcc_error("branch offset is too far");
    return 0;
  }
  return /*not 0x0A000000|*/(addr&0xffffff);
}

static void asm_branch_opcode(TCCState *s1, int token)
{
    int jmp_disp = 0;
    Operand op;
    ExprValue e;
    ElfSym *esym;

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_beq:
    case TOK_ASM_bleq:
        asm_expr(s1, &e);
        esym = elfsym(e.sym);
        if (!esym || esym->st_shndx != cur_text_section->sh_num) {
            tcc_error("invalid branch target");
            return;
        }
        jmp_disp = encbranchoffset(ind, e.v + esym->st_value, 1);
        break;
    default:
        parse_operand(s1, &op);
        break;
    }
    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_beq:
        asm_emit_opcode(token, (0xa << 24) | (jmp_disp & 0xffffff));
        break;
    case TOK_ASM_bleq:
        asm_emit_opcode(token, (0xb << 24) | (jmp_disp & 0xffffff));
        break;
    case TOK_ASM_bxeq:
        if (op.type != OP_REG32)
            expect("register");
        else
            asm_emit_opcode(token, (0x12fff1 << 4) | op.reg);
        break;
    case TOK_ASM_blxeq:
        if (op.type != OP_REG32)
            expect("register");
        else
            asm_emit_opcode(token, (0x12fff3 << 4) | op.reg);
        break;
    default:
        expect("branch instruction");
    }
}

ST_FUNC void asm_opcode(TCCState *s1, int token)
{
    while (token == TOK_LINEFEED) {
        next();
        token = tok;
    }
    if (token == TOK_EOF)
        return;
    if (token < TOK_ASM_nopeq) { // no condition code
        switch (token) {
        case TOK_ASM_cdp2:
            return asm_coprocessor_opcode(s1, token);
        case TOK_ASM_ldc2:
        case TOK_ASM_ldc2l:
        case TOK_ASM_stc2:
        case TOK_ASM_stc2l:
            return asm_coprocessor_data_transfer_opcode(s1, token);
        default:
            expect("instruction");
            return;
        }
    }

    switch (ARM_INSTRUCTION_GROUP(token)) {
    case TOK_ASM_pusheq:
    case TOK_ASM_popeq:
    case TOK_ASM_stmdaeq:
    case TOK_ASM_ldmdaeq:
    case TOK_ASM_stmeq:
    case TOK_ASM_ldmeq:
    case TOK_ASM_stmiaeq:
    case TOK_ASM_ldmiaeq:
    case TOK_ASM_stmdbeq:
    case TOK_ASM_ldmdbeq:
    case TOK_ASM_stmibeq:
    case TOK_ASM_ldmibeq:
        return asm_block_data_transfer_opcode(s1, token);
    case TOK_ASM_nopeq:
    case TOK_ASM_wfeeq:
    case TOK_ASM_wfieq:
        return asm_nullary_opcode(token);
    case TOK_ASM_swieq:
        return asm_unary_opcode(s1, token);
    case TOK_ASM_beq:
    case TOK_ASM_bleq:
    case TOK_ASM_bxeq:
    case TOK_ASM_blxeq:
        return asm_branch_opcode(s1, token);
    case TOK_ASM_clzeq:
    case TOK_ASM_sxtbeq:
    case TOK_ASM_sxtheq:
    case TOK_ASM_uxtbeq:
    case TOK_ASM_uxtheq:
    case TOK_ASM_movteq:
    case TOK_ASM_movweq:
        return asm_binary_opcode(s1, token);

    case TOK_ASM_ldreq:
    case TOK_ASM_ldrbeq:
    case TOK_ASM_streq:
    case TOK_ASM_strbeq:
    case TOK_ASM_ldrexeq:
    case TOK_ASM_ldrexbeq:
    case TOK_ASM_strexeq:
    case TOK_ASM_strexbeq:
        return asm_single_data_transfer_opcode(s1, token);

    case TOK_ASM_ldrheq:
    case TOK_ASM_ldrsheq:
    case TOK_ASM_ldrsbeq:
    case TOK_ASM_strheq:
       return asm_misc_single_data_transfer_opcode(s1, token);

    case TOK_ASM_andeq:
    case TOK_ASM_eoreq:
    case TOK_ASM_subeq:
    case TOK_ASM_rsbeq:
    case TOK_ASM_addeq:
    case TOK_ASM_adceq:
    case TOK_ASM_sbceq:
    case TOK_ASM_rsceq:
    case TOK_ASM_tsteq:
    case TOK_ASM_teqeq:
    case TOK_ASM_cmpeq:
    case TOK_ASM_cmneq:
    case TOK_ASM_orreq:
    case TOK_ASM_moveq:
    case TOK_ASM_biceq:
    case TOK_ASM_mvneq:
    case TOK_ASM_andseq:
    case TOK_ASM_eorseq:
    case TOK_ASM_subseq:
    case TOK_ASM_rsbseq:
    case TOK_ASM_addseq:
    case TOK_ASM_adcseq:
    case TOK_ASM_sbcseq:
    case TOK_ASM_rscseq:
//  case TOK_ASM_tstseq:
//  case TOK_ASM_teqseq:
//  case TOK_ASM_cmpseq:
//  case TOK_ASM_cmnseq:
    case TOK_ASM_orrseq:
    case TOK_ASM_movseq:
    case TOK_ASM_bicseq:
    case TOK_ASM_mvnseq:
        return asm_data_processing_opcode(s1, token);

    case TOK_ASM_lsleq:
    case TOK_ASM_lslseq:
    case TOK_ASM_lsreq:
    case TOK_ASM_lsrseq:
    case TOK_ASM_asreq:
    case TOK_ASM_asrseq:
    case TOK_ASM_roreq:
    case TOK_ASM_rorseq:
    case TOK_ASM_rrxseq:
    case TOK_ASM_rrxeq:
        return asm_shift_opcode(s1, token);

    case TOK_ASM_muleq:
    case TOK_ASM_mulseq:
    case TOK_ASM_mlaeq:
    case TOK_ASM_mlaseq:
        return asm_multiplication_opcode(s1, token);

    case TOK_ASM_smulleq:
    case TOK_ASM_smullseq:
    case TOK_ASM_umulleq:
    case TOK_ASM_umullseq:
    case TOK_ASM_smlaleq:
    case TOK_ASM_smlalseq:
    case TOK_ASM_umlaleq:
    case TOK_ASM_umlalseq:
        return asm_long_multiplication_opcode(s1, token);

    case TOK_ASM_cdpeq:
    case TOK_ASM_mcreq:
    case TOK_ASM_mrceq:
        return asm_coprocessor_opcode(s1, token);

    case TOK_ASM_ldceq:
    case TOK_ASM_ldcleq:
    case TOK_ASM_stceq:
    case TOK_ASM_stcleq:
        return asm_coprocessor_data_transfer_opcode(s1, token);

    default:
        expect("known instruction");
    }
}

ST_FUNC void subst_asm_operand(CString *add_str, SValue *sv, int modifier)
{
    int r, reg, size, val;
    char buf[64];

    r = sv->r;
    if ((r & VT_VALMASK) == VT_CONST) {
        if (!(r & VT_LVAL) && modifier != 'c' && modifier != 'n' &&
            modifier != 'P')
            cstr_ccat(add_str, '#');
        if (r & VT_SYM) {
            const char *name = get_tok_str(sv->sym->v, NULL);
            if (sv->sym->v >= SYM_FIRST_ANOM) {
                /* In case of anonymous symbols ("L.42", used
                   for static data labels) we can't find them
                   in the C symbol table when later looking up
                   this name.  So enter them now into the asm label
                   list when we still know the symbol.  */
                get_asm_sym(tok_alloc(name, strlen(name))->tok, sv->sym);
            }
            if (tcc_state->leading_underscore)
                cstr_ccat(add_str, '_');
            cstr_cat(add_str, name, -1);
            if ((uint32_t) sv->c.i == 0)
                goto no_offset;
            cstr_ccat(add_str, '+');
        }
        val = sv->c.i;
        if (modifier == 'n')
            val = -val;
        snprintf(buf, sizeof(buf), "%d", (int) sv->c.i);
        cstr_cat(add_str, buf, -1);
      no_offset:;
    } else if ((r & VT_VALMASK) == VT_LOCAL) {
        snprintf(buf, sizeof(buf), "[fp,#%d]", (int) sv->c.i);
        cstr_cat(add_str, buf, -1);
    } else if (r & VT_LVAL) {
        reg = r & VT_VALMASK;
        if (reg >= VT_CONST)
            tcc_internal_error("");
        snprintf(buf, sizeof(buf), "[%s]",
                 get_tok_str(TOK_ASM_r0 + reg, NULL));
        cstr_cat(add_str, buf, -1);
    } else {
        /* register case */
        reg = r & VT_VALMASK;
        if (reg >= VT_CONST)
            tcc_internal_error("");

        /* choose register operand size */
        if ((sv->type.t & VT_BTYPE) == VT_BYTE ||
            (sv->type.t & VT_BTYPE) == VT_BOOL)
            size = 1;
        else if ((sv->type.t & VT_BTYPE) == VT_SHORT)
            size = 2;
        else
            size = 4;

        if (modifier == 'b') {
            size = 1;
        } else if (modifier == 'w') {
            size = 2;
        } else if (modifier == 'k') {
            size = 4;
        }

        switch (size) {
        default:
            reg = TOK_ASM_r0 + reg;
            break;
        }
        snprintf(buf, sizeof(buf), "%s", get_tok_str(reg, NULL));
        cstr_cat(add_str, buf, -1);
    }
}

/* generate prolog and epilog code for asm statement */
ST_FUNC void asm_gen_code(ASMOperand *operands, int nb_operands,
                          int nb_outputs, int is_output,
                          uint8_t *clobber_regs,
                          int out_reg)
{
    uint8_t regs_allocated[NB_ASM_REGS];
    ASMOperand *op;
    int i, reg;
    uint32_t saved_regset = 0;

    // TODO: Check non-E ABI.
    // Note: Technically, r13 (sp) is also callee-saved--but that does not matter yet
    static uint8_t reg_saved[] = { 4, 5, 6, 7, 8, 9 /* Note: sometimes special reg "sb" */ , 10, 11 };

    /* mark all used registers */
    memcpy(regs_allocated, clobber_regs, sizeof(regs_allocated));
    for(i = 0; i < nb_operands;i++) {
        op = &operands[i];
        if (op->reg >= 0)
            regs_allocated[op->reg] = 1;
    }
    for(i = 0; i < sizeof(reg_saved)/sizeof(reg_saved[0]); i++) {
        reg = reg_saved[i];
        if (regs_allocated[reg])
            saved_regset |= 1 << reg;
    }

    if (!is_output) { // prolog
        /* generate reg save code */
        if (saved_regset)
            gen_le32(0xe92d0000 | saved_regset); // push {...}

        /* generate load code */
        for(i = 0; i < nb_operands; i++) {
            op = &operands[i];
            if (op->reg >= 0) {
                if ((op->vt->r & VT_VALMASK) == VT_LLOCAL &&
                    op->is_memory) {
                    /* memory reference case (for both input and
                       output cases) */
                    SValue sv;
                    sv = *op->vt;
                    sv.r = (sv.r & ~VT_VALMASK) | VT_LOCAL | VT_LVAL;
                    sv.type.t = VT_PTR;
                    load(op->reg, &sv);
                } else if (i >= nb_outputs || op->is_rw) { // not write-only
                    /* load value in register */
                    load(op->reg, op->vt);
                    if (op->is_llong)
                        tcc_error("long long not implemented");
                }
            }
        }
    } else { // epilog
        /* generate save code */
        for(i = 0 ; i < nb_outputs; i++) {
            op = &operands[i];
            if (op->reg >= 0) {
                if ((op->vt->r & VT_VALMASK) == VT_LLOCAL) {
                    if (!op->is_memory) {
                        SValue sv;
                        sv = *op->vt;
                        sv.r = (sv.r & ~VT_VALMASK) | VT_LOCAL;
                        sv.type.t = VT_PTR;
                        load(out_reg, &sv);

                        sv = *op->vt;
                        sv.r = (sv.r & ~VT_VALMASK) | out_reg;
                        store(op->reg, &sv);
                    }
                } else {
                    store(op->reg, op->vt);
                    if (op->is_llong)
                        tcc_error("long long not implemented");
                }
            }
        }

        /* generate reg restore code */
        if (saved_regset)
            gen_le32(0xe8bd0000 | saved_regset); // pop {...}
    }
}

/* return the constraint priority (we allocate first the lowest
   numbered constraints) */
static inline int constraint_priority(const char *str)
{
    int priority, c, pr;

    /* we take the lowest priority */
    priority = 0;
    for(;;) {
        c = *str;
        if (c == '\0')
            break;
        str++;
        switch(c) {
        case 'l': // in ARM mode, that's  an alias for 'r' [ARM].
        case 'r': // register [general]
        case 'p': // valid memory address for load,store [general]
            pr = 3;
            break;
        case 'M': // integer constant for shifts [ARM]
        case 'I': // integer valid for data processing instruction immediate
        case 'J': // integer in range -4095...4095

        case 'i': // immediate integer operand, including symbolic constants [general]
        case 'm': // memory operand [general]
        case 'g': // general-purpose-register, memory, immediate integer [general]
            pr = 4;
            break;
        default:
            tcc_error("unknown constraint '%c'", c);
            pr = 0;
        }
        if (pr > priority)
            priority = pr;
    }
    return priority;
}

static const char *skip_constraint_modifiers(const char *p)
{
    /* Constraint modifier:
        =   Operand is written to by this instruction
        +   Operand is both read and written to by this instruction
        %   Instruction is commutative for this operand and the following operand.

       Per-alternative constraint modifier:
        &   Operand is clobbered before the instruction is done using the input operands
    */
    while (*p == '=' || *p == '&' || *p == '+' || *p == '%')
        p++;
    return p;
}

#define REG_OUT_MASK 0x01
#define REG_IN_MASK  0x02

#define is_reg_allocated(reg) (regs_allocated[reg] & reg_mask)

ST_FUNC void asm_compute_constraints(ASMOperand *operands,
                                    int nb_operands, int nb_outputs,
                                    const uint8_t *clobber_regs,
                                    int *pout_reg)
{
    /* overall format: modifier, then ,-seperated list of alternatives; all operands for a single instruction must have the same number of alternatives */
    /* TODO: Simple constraints
        whitespace  ignored
        o  memory operand that is offsetable
        V  memory but not offsetable
        <  memory operand with autodecrement addressing is allowed.  Restrictions apply.
        >  memory operand with autoincrement addressing is allowed.  Restrictions apply.
        n  immediate integer operand with a known numeric value
        E  immediate floating operand (const_double) is allowed, but only if target=host
        F  immediate floating operand (const_double or const_vector) is allowed
        s  immediate integer operand whose value is not an explicit integer
        X  any operand whatsoever
        0...9 (postfix); (can also be more than 1 digit number);  an operand that matches the specified operand number is allowed
    */

    /* TODO: ARM constraints:
        k the stack pointer register
        G the floating-point constant 0.0
        Q memory reference where the exact address is in a single register ("m" is preferable for asm statements)
        R an item in the constant pool
        S symbol in the text segment of the current file
[       Uv memory reference suitable for VFP load/store insns (reg+constant offset)]
[       Uy memory reference suitable for iWMMXt load/store instructions]
        Uq memory reference suitable for the ARMv4 ldrsb instruction
    */
    ASMOperand *op;
    int sorted_op[MAX_ASM_OPERANDS];
    int i, j, k, p1, p2, tmp, reg, c, reg_mask;
    const char *str;
    uint8_t regs_allocated[NB_ASM_REGS];

    /* init fields */
    for (i = 0; i < nb_operands; i++) {
        op = &operands[i];
        op->input_index = -1;
        op->ref_index = -1;
        op->reg = -1;
        op->is_memory = 0;
        op->is_rw = 0;
    }
    /* compute constraint priority and evaluate references to output
       constraints if input constraints */
    for (i = 0; i < nb_operands; i++) {
        op = &operands[i];
        str = op->constraint;
        str = skip_constraint_modifiers(str);
        if (isnum(*str) || *str == '[') {
            /* this is a reference to another constraint */
            k = find_constraint(operands, nb_operands, str, NULL);
            if ((unsigned) k >= i || i < nb_outputs)
                tcc_error("invalid reference in constraint %d ('%s')",
                          i, str);
            op->ref_index = k;
            if (operands[k].input_index >= 0)
                tcc_error("cannot reference twice the same operand");
            operands[k].input_index = i;
            op->priority = 5;
        } else if ((op->vt->r & VT_VALMASK) == VT_LOCAL
                   && op->vt->sym
                   && (reg = op->vt->sym->r & VT_VALMASK) < VT_CONST) {
            op->priority = 1;
            op->reg = reg;
        } else {
            op->priority = constraint_priority(str);
        }
    }

    /* sort operands according to their priority */
    for (i = 0; i < nb_operands; i++)
        sorted_op[i] = i;
    for (i = 0; i < nb_operands - 1; i++) {
        for (j = i + 1; j < nb_operands; j++) {
            p1 = operands[sorted_op[i]].priority;
            p2 = operands[sorted_op[j]].priority;
            if (p2 < p1) {
                tmp = sorted_op[i];
                sorted_op[i] = sorted_op[j];
                sorted_op[j] = tmp;
            }
        }
    }

    for (i = 0; i < NB_ASM_REGS; i++) {
        if (clobber_regs[i])
            regs_allocated[i] = REG_IN_MASK | REG_OUT_MASK;
        else
            regs_allocated[i] = 0;
    }
    /* sp cannot be used */
    regs_allocated[13] = REG_IN_MASK | REG_OUT_MASK;
    /* fp cannot be used yet */
    regs_allocated[11] = REG_IN_MASK | REG_OUT_MASK;

    /* allocate registers and generate corresponding asm moves */
    for (i = 0; i < nb_operands; i++) {
        j = sorted_op[i];
        op = &operands[j];
        str = op->constraint;
        /* no need to allocate references */
        if (op->ref_index >= 0)
            continue;
        /* select if register is used for output, input or both */
        if (op->input_index >= 0) {
            reg_mask = REG_IN_MASK | REG_OUT_MASK;
        } else if (j < nb_outputs) {
            reg_mask = REG_OUT_MASK;
        } else {
            reg_mask = REG_IN_MASK;
        }
        if (op->reg >= 0) {
            if (is_reg_allocated(op->reg))
                tcc_error
                    ("asm regvar requests register that's taken already");
            reg = op->reg;
            goto reg_found;
        }
      try_next:
        c = *str++;
        switch (c) {
        case '=': // Operand is written-to
            goto try_next;
        case '+': // Operand is both READ and written-to
            op->is_rw = 1;
            /* FALL THRU */
        case '&': // Operand is clobbered before the instruction is done using the input operands
            if (j >= nb_outputs)
                tcc_error("'%c' modifier can only be applied to outputs",
                          c);
            reg_mask = REG_IN_MASK | REG_OUT_MASK;
            goto try_next;
        case 'l': // In non-thumb mode, alias for 'r'--otherwise r0-r7 [ARM]
        case 'r': // general-purpose register
        case 'p': // loadable/storable address
            /* any general register */
            for (reg = 0; reg <= 8; reg++) {
                if (!is_reg_allocated(reg))
                    goto reg_found;
            }
            goto try_next;
          reg_found:
            /* now we can reload in the register */
            op->is_llong = 0;
            op->reg = reg;
            regs_allocated[reg] |= reg_mask;
            break;
        case 'I': // integer that is valid as an data processing instruction immediate (0...255, rotated by a multiple of two)
        case 'J': // integer in the range -4095 to 4095 [ARM]
        case 'K': // integer that satisfies constraint I when inverted (one's complement)
        case 'L': // integer that satisfies constraint I when inverted (two's complement)
        case 'i': // immediate integer operand, including symbolic constants
            if (!((op->vt->r & (VT_VALMASK | VT_LVAL)) == VT_CONST))
                goto try_next;
            break;
        case 'M': // integer in the range 0 to 32
            if (!
                ((op->vt->r & (VT_VALMASK | VT_LVAL | VT_SYM)) ==
                 VT_CONST))
                goto try_next;
            break;
        case 'm': // memory operand
        case 'g':
            /* nothing special to do because the operand is already in
               memory, except if the pointer itself is stored in a
               memory variable (VT_LLOCAL case) */
            /* XXX: fix constant case */
            /* if it is a reference to a memory zone, it must lie
               in a register, so we reserve the register in the
               input registers and a load will be generated
               later */
            if (j < nb_outputs || c == 'm') {
                if ((op->vt->r & VT_VALMASK) == VT_LLOCAL) {
                    /* any general register */
                    for (reg = 0; reg <= 8; reg++) {
                        if (!(regs_allocated[reg] & REG_IN_MASK))
                            goto reg_found1;
                    }
                    goto try_next;
                  reg_found1:
                    /* now we can reload in the register */
                    regs_allocated[reg] |= REG_IN_MASK;
                    op->reg = reg;
                    op->is_memory = 1;
                }
            }
            break;
        default:
            tcc_error("asm constraint %d ('%s') could not be satisfied",
                      j, op->constraint);
            break;
        }
        /* if a reference is present for that operand, we assign it too */
        if (op->input_index >= 0) {
            operands[op->input_index].reg = op->reg;
            operands[op->input_index].is_llong = op->is_llong;
        }
    }

    /* compute out_reg. It is used to store outputs registers to memory
       locations references by pointers (VT_LLOCAL case) */
    *pout_reg = -1;
    for (i = 0; i < nb_operands; i++) {
        op = &operands[i];
        if (op->reg >= 0 &&
            (op->vt->r & VT_VALMASK) == VT_LLOCAL && !op->is_memory) {
            for (reg = 0; reg <= 8; reg++) {
                if (!(regs_allocated[reg] & REG_OUT_MASK))
                    goto reg_found2;
            }
            tcc_error("could not find free output register for reloading");
          reg_found2:
            *pout_reg = reg;
            break;
        }
    }

    /* print sorted constraints */
#ifdef ASM_DEBUG
    for (i = 0; i < nb_operands; i++) {
        j = sorted_op[i];
        op = &operands[j];
        printf("%%%d [%s]: \"%s\" r=0x%04x reg=%d\n",
               j,
               op->id ? get_tok_str(op->id, NULL) : "",
               op->constraint, op->vt->r, op->reg);
    }
    if (*pout_reg >= 0)
        printf("out_reg=%d\n", *pout_reg);
#endif
}

ST_FUNC void asm_clobber(uint8_t *clobber_regs, const char *str)
{
    int reg;
    TokenSym *ts;

    if (!strcmp(str, "memory") ||
        !strcmp(str, "cc") ||
        !strcmp(str, "flags"))
        return;
    ts = tok_alloc(str, strlen(str));
    reg = asm_parse_regvar(ts->tok);
    if (reg == -1) {
        tcc_error("invalid clobber register '%s'", str);
    }
    clobber_regs[reg] = 1;
}

/* If T refers to a register then return the register number and type.
   Otherwise return -1.  */
ST_FUNC int asm_parse_regvar (int t)
{
    if (t >= TOK_ASM_r0 && t <= TOK_ASM_pc) { /* register name */
        switch (t) {
            case TOK_ASM_fp:
                return TOK_ASM_r11 - TOK_ASM_r0;
            case TOK_ASM_ip:
                return TOK_ASM_r12 - TOK_ASM_r0;
            case TOK_ASM_sp:
                return TOK_ASM_r13 - TOK_ASM_r0;
            case TOK_ASM_lr:
                return TOK_ASM_r14 - TOK_ASM_r0;
            case TOK_ASM_pc:
                return TOK_ASM_r15 - TOK_ASM_r0;
            default:
                return t - TOK_ASM_r0;
        }
    } else
        return -1;
}

/*************************************************************/
#endif /* ndef TARGET_DEFS_ONLY */