i386-gen.c

tcc

/*
 *  X86 code generator for TCC
 * 
 *  Copyright (c) 2001, 2002, 2003 Fabrice Bellard
 *
 * 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
 */

/* number of available registers */
#define NB_REGS             4

/* a register can belong to several classes. The classes must be
   sorted from more general to more precise (see gv2() code which does
   assumptions on it). */
#define RC_INT     0x0001 /* generic integer register */
#define RC_FLOAT   0x0002 /* generic float register */
#define RC_EAX     0x0004
#define RC_ST0     0x0008 
#define RC_ECX     0x0010
#define RC_EDX     0x0020
#define RC_IRET    RC_EAX /* function return: integer register */
#define RC_LRET    RC_EDX /* function return: second integer register */
#define RC_FRET    RC_ST0 /* function return: float register */

/* pretty names for the registers */
enum {
    TREG_EAX = 0,
    TREG_ECX,
    TREG_EDX,
    TREG_ST0,
};

int reg_classes[NB_REGS] = {
    /* eax */ RC_INT | RC_EAX,
    /* ecx */ RC_INT | RC_ECX,
    /* edx */ RC_INT | RC_EDX,
    /* st0 */ RC_FLOAT | RC_ST0,
};

/* return registers for function */
#define REG_IRET TREG_EAX /* single word int return register */
#define REG_LRET TREG_EDX /* second word return register (for long long) */
#define REG_FRET TREG_ST0 /* float return register */

/* defined if function parameters must be evaluated in reverse order */
#define INVERT_FUNC_PARAMS

/* defined if structures are passed as pointers. Otherwise structures
   are directly pushed on stack. */
//#define FUNC_STRUCT_PARAM_AS_PTR

/* pointer size, in bytes */
#define PTR_SIZE 4

/* long double size and alignment, in bytes */
#define LDOUBLE_SIZE  12
#define LDOUBLE_ALIGN 4
/* maximum alignment (for aligned attribute support) */
#define MAX_ALIGN     8

/* relocation type for 32 bit data relocation */
#define R_DATA_32 R_386_32

/******************************************************/

static unsigned long func_sub_sp_offset;
static unsigned long func_bound_offset;
static int func_ret_sub;

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

void o(int c)
{
    while (c) {
        g(c);
        c = c / 256;
    }
}

void gen_le32(int c)
{
    g(c);
    g(c >> 8);
    g(c >> 16);
    g(c >> 24);
}

/* output a symbol and patch all calls to it */
void gsym_addr(int t, int a)
{
    int n, *ptr;
    while (t) {
        ptr = (int *)(cur_text_section->data + t);
        n = *ptr; /* next value */
        *ptr = a - t - 4;
        t = n;
    }
}

void gsym(int t)
{
    gsym_addr(t, ind);
}

/* psym is used to put an instruction with a data field which is a
   reference to a symbol. It is in fact the same as oad ! */
#define psym oad

/* instruction + 4 bytes data. Return the address of the data */
static int oad(int c, int s)
{
    int ind1;

    o(c);
    ind1 = ind + 4;
    if (ind1 > cur_text_section->data_allocated)
        section_realloc(cur_text_section, ind1);
    *(int *)(cur_text_section->data + ind) = s;
    s = ind;
    ind = ind1;
    return s;
}

/* output constant with relocation if 'r & VT_SYM' is true */
static void gen_addr32(int r, Sym *sym, int c)
{
    if (r & VT_SYM)
        greloc(cur_text_section, sym, ind, R_386_32);
    gen_le32(c);
}

/* generate a modrm reference. 'op_reg' contains the addtionnal 3
   opcode bits */
static void gen_modrm(int op_reg, int r, Sym *sym, int c)
{
    op_reg = op_reg << 3;
    if ((r & VT_VALMASK) == VT_CONST) {
        /* constant memory reference */
        o(0x05 | op_reg);
        gen_addr32(r, sym, c);
    } else if ((r & VT_VALMASK) == VT_LOCAL) {
        /* currently, we use only ebp as base */
        if (c == (char)c) {
            /* short reference */
            o(0x45 | op_reg);
            g(c);
        } else {
            oad(0x85 | op_reg, c);
        }
    } else {
        g(0x00 | op_reg | (r & VT_VALMASK));
    }
}


/* load 'r' from value 'sv' */
void load(int r, SValue *sv)
{
    int v, t, ft, fc, fr;
    SValue v1;

    fr = sv->r;
    ft = sv->type.t;
    fc = sv->c.ul;

    v = fr & VT_VALMASK;
    if (fr & VT_LVAL) {
        if (v == VT_LLOCAL) {
            v1.type.t = VT_INT;
            v1.r = VT_LOCAL | VT_LVAL;
            v1.c.ul = fc;
            load(r, &v1);
            fr = r;
        }
        if ((ft & VT_BTYPE) == VT_FLOAT) {
            o(0xd9); /* flds */
            r = 0;
        } else if ((ft & VT_BTYPE) == VT_DOUBLE) {
            o(0xdd); /* fldl */
            r = 0;
        } else if ((ft & VT_BTYPE) == VT_LDOUBLE) {
            o(0xdb); /* fldt */
            r = 5;
        } else if ((ft & VT_TYPE) == VT_BYTE) {
            o(0xbe0f);   /* movsbl */
        } else if ((ft & VT_TYPE) == (VT_BYTE | VT_UNSIGNED)) {
            o(0xb60f);   /* movzbl */
        } else if ((ft & VT_TYPE) == VT_SHORT) {
            o(0xbf0f);   /* movswl */
        } else if ((ft & VT_TYPE) == (VT_SHORT | VT_UNSIGNED)) {
            o(0xb70f);   /* movzwl */
        } else {
            o(0x8b);     /* movl */
        }
        gen_modrm(r, fr, sv->sym, fc);
    } else {
        if (v == VT_CONST) {
            o(0xb8 + r); /* mov $xx, r */
            gen_addr32(fr, sv->sym, fc);
        } else if (v == VT_LOCAL) {
            o(0x8d); /* lea xxx(%ebp), r */
            gen_modrm(r, VT_LOCAL, sv->sym, fc);
        } else if (v == VT_CMP) {
            oad(0xb8 + r, 0); /* mov $0, r */
            o(0x0f); /* setxx %br */
            o(fc);
            o(0xc0 + r);
        } else if (v == VT_JMP || v == VT_JMPI) {
            t = v & 1;
            oad(0xb8 + r, t); /* mov $1, r */
            o(0x05eb); /* jmp after */
            gsym(fc);
            oad(0xb8 + r, t ^ 1); /* mov $0, r */
        } else if (v != r) {
            o(0x89);
            o(0xc0 + r + v * 8); /* mov v, r */
        }
    }
}

/* store register 'r' in lvalue 'v' */
void store(int r, SValue *v)
{
    int fr, bt, ft, fc;

    ft = v->type.t;
    fc = v->c.ul;
    fr = v->r & VT_VALMASK;
    bt = ft & VT_BTYPE;
    /* XXX: incorrect if float reg to reg */
    if (bt == VT_FLOAT) {
        o(0xd9); /* fsts */
        r = 2;
    } else if (bt == VT_DOUBLE) {
        o(0xdd); /* fstpl */
        r = 2;
    } else if (bt == VT_LDOUBLE) {
        o(0xc0d9); /* fld %st(0) */
        o(0xdb); /* fstpt */
        r = 7;
    } else {
        if (bt == VT_SHORT)
            o(0x66);
        if (bt == VT_BYTE)
            o(0x88);
        else
            o(0x89);
    }
    if (fr == VT_CONST ||
        fr == VT_LOCAL ||
        (v->r & VT_LVAL)) {
        gen_modrm(r, v->r, v->sym, fc);
    } else if (fr != r) {
        o(0xc0 + fr + r * 8); /* mov r, fr */
    }
}

static void gadd_sp(int val)
{
    if (val == (char)val) {
        o(0xc483);
        g(val);
    } else {
        oad(0xc481, val); /* add $xxx, %esp */
    }
}

/* 'is_jmp' is '1' if it is a jump */
static void gcall_or_jmp(int is_jmp)
{
    int r;
    if ((vtop->r & (VT_VALMASK | VT_LVAL)) == VT_CONST) {
        /* constant case */
        if (vtop->r & VT_SYM) {
            /* relocation case */
            greloc(cur_text_section, vtop->sym, 
                   ind + 1, R_386_PC32);
        } else {
            /* put an empty PC32 relocation */
            put_elf_reloc(symtab_section, cur_text_section, 
                          ind + 1, R_386_PC32, 0);
        }
        oad(0xe8 + is_jmp, vtop->c.ul - 4); /* call/jmp im */
    } else {
        /* otherwise, indirect call */
        r = gv(RC_INT);
        o(0xff); /* call/jmp *r */
        o(0xd0 + r + (is_jmp << 4));
    }
}

/* Generate function call. The function address is pushed first, then
   all the parameters in call order. This functions pops all the
   parameters and the function address. */
void gfunc_call(int nb_args)
{
    int size, align, r, args_size, i;
    Sym *func_sym;
    
    args_size = 0;
    for(i = 0;i < nb_args; i++) {
        if ((vtop->type.t & VT_BTYPE) == VT_STRUCT) {
            size = type_size(&vtop->type, &align);
            /* align to stack align size */
            size = (size + 3) & ~3;
            /* allocate the necessary size on stack */
            oad(0xec81, size); /* sub $xxx, %esp */
            /* generate structure store */
            r = get_reg(RC_INT);
            o(0x89); /* mov %esp, r */
            o(0xe0 + r);
            vset(&vtop->type, r | VT_LVAL, 0);
            vswap();
            vstore();
            args_size += size;
        } else if (is_float(vtop->type.t)) {
            gv(RC_FLOAT); /* only one float register */
            if ((vtop->type.t & VT_BTYPE) == VT_FLOAT)
                size = 4;
            else if ((vtop->type.t & VT_BTYPE) == VT_DOUBLE)
                size = 8;
            else
                size = 12;
            oad(0xec81, size); /* sub $xxx, %esp */
            if (size == 12)
                o(0x7cdb);
            else
                o(0x5cd9 + size - 4); /* fstp[s|l] 0(%esp) */
            g(0x24);
            g(0x00);
            args_size += size;
        } else {
            /* simple type (currently always same size) */
            /* XXX: implicit cast ? */
            r = gv(RC_INT);
            if ((vtop->type.t & VT_BTYPE) == VT_LLONG) {
                size = 8;
                o(0x50 + vtop->r2); /* push r */
            } else {
                size = 4;
            }
            o(0x50 + r); /* push r */
            args_size += size;
        }
        vtop--;
    }
    save_regs(0); /* save used temporary registers */
    func_sym = vtop->type.ref;
    gcall_or_jmp(0);
    if (args_size && func_sym->r == FUNC_CDECL)
        gadd_sp(args_size);
    vtop--;
}

/* generate function prolog of type 't' */
void gfunc_prolog(CType *func_type)
{
    int addr, align, size, func_call;
    Sym *sym;
    CType *type;

    sym = func_type->ref;
    func_call = sym->r;
    addr = 8;
    /* if the function returns a structure, then add an
       implicit pointer parameter */
    func_vt = sym->type;
    if ((func_vt.t & VT_BTYPE) == VT_STRUCT) {
        func_vc = addr;
        addr += 4;
    }
    /* define parameters */
    while ((sym = sym->next) != NULL) {
        type = &sym->type;
        sym_push(sym->v & ~SYM_FIELD, type,
                 VT_LOCAL | VT_LVAL, addr);
        size = type_size(type, &align);
        size = (size + 3) & ~3;
#ifdef FUNC_STRUCT_PARAM_AS_PTR
        /* structs are passed as pointer */
        if ((type->t & VT_BTYPE) == VT_STRUCT) {
            size = 4;
        }
#endif
        addr += size;
    }
    func_ret_sub = 0;
    /* pascal type call ? */
    if (func_call == FUNC_STDCALL)
        func_ret_sub = addr - 8;
    o(0xe58955); /* push   %ebp, mov    %esp, %ebp */
    func_sub_sp_offset = oad(0xec81, 0); /* sub $xxx, %esp */
    /* leave some room for bound checking code */
    if (do_bounds_check) {
        oad(0xb8, 0); /* lbound section pointer */
        oad(0xb8, 0); /* call to function */
        func_bound_offset = lbounds_section->data_offset;
    }
}

/* generate function epilog */
void gfunc_epilog(void)
{
#ifdef CONFIG_TCC_BCHECK
    if (do_bounds_check && func_bound_offset != lbounds_section->data_offset) {
        int saved_ind;
        int *bounds_ptr;
        Sym *sym, *sym_data;
        /* add end of table info */
        bounds_ptr = section_ptr_add(lbounds_section, sizeof(int));
        *bounds_ptr = 0;
        /* generate bound local allocation */
        saved_ind = ind;
        ind = func_sub_sp_offset + 4;
        sym_data = get_sym_ref(&char_pointer_type, lbounds_section, 
                               func_bound_offset, lbounds_section->data_offset);
        greloc(cur_text_section, sym_data,
               ind + 1, R_386_32);
        oad(0xb8, 0); /* mov %eax, xxx */
        sym = external_global_sym(TOK___bound_local_new, &func_old_type, 0);
        greloc(cur_text_section, sym, 
               ind + 1, R_386_PC32);
        oad(0xe8, -4);
        ind = saved_ind;
        /* generate bound check local freeing */
        o(0x5250); /* save returned value, if any */
        greloc(cur_text_section, sym_data,
               ind + 1, R_386_32);
        oad(0xb8, 0); /* mov %eax, xxx */
        sym = external_global_sym(TOK___bound_local_delete, &func_old_type, 0);
        greloc(cur_text_section, sym, 
               ind + 1, R_386_PC32);
        oad(0xe8, -4);
        o(0x585a); /* restore returned value, if any */
    }
#endif
    o(0xc9); /* leave */
    if (func_ret_sub == 0) {
        o(0xc3); /* ret */
    } else {
        o(0xc2); /* ret n */
        g(func_ret_sub);
        g(func_ret_sub >> 8);
    }
    /* align local size to word & save local variables */
    *(int *)(cur_text_section->data + func_sub_sp_offset) = (-loc + 3) & -4; 
}

/* generate a jump to a label */
int gjmp(int t)
{