Do some kind of signed cast too.

[smatch.git] / example.c

/*
 * Example of how to write a compiler with sparse
 */
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>

#include "symbol.h"
#include "expression.h"
#include "linearize.h"
#include "flow.h"
#include "storage.h"

struct hardreg {
        const char *name;
        struct pseudo_list *contains;
        unsigned busy:16,
                 dead:8,
                 used:1;
};

#define TAG_DEAD 1
#define TAG_DIRTY 2

/* Our "switch" generation is very very stupid. */
#define SWITCH_REG (1)

static void output_bb(struct basic_block *bb, unsigned long generation);

/*
 * We only know about the caller-clobbered registers
 * right now.
 */
static struct hardreg hardregs[] = {
        { .name = "%eax" },
        { .name = "%edx" },
        { .name = "%ecx" },
        { .name = "%ebx" },
        { .name = "%esi" },
        { .name = "%edi" },
};
#define REGNO (sizeof(hardregs)/sizeof(struct hardreg))

struct bb_state {
        struct basic_block *bb;
        unsigned long stack_offset;
        struct storage_hash_list *inputs;
        struct storage_hash_list *outputs;
        struct storage_hash_list *internal;
};

static struct storage_hash *find_storage_hash(pseudo_t pseudo, struct storage_hash_list *list)
{
        struct storage_hash *entry;
        FOR_EACH_PTR(list, entry) {
                if (entry->pseudo == pseudo)
                        return entry;
        } END_FOR_EACH_PTR(entry);
        return NULL;
}

static struct storage_hash *find_or_create_hash(pseudo_t pseudo, struct storage_hash_list **listp)
{
        struct storage_hash *entry;

        entry = find_storage_hash(pseudo, *listp);
        if (!entry) {
                entry = alloc_storage_hash(alloc_storage());
                entry->pseudo = pseudo;
                add_ptr_list(listp, entry);
        }
        return entry;
}

/* Eventually we should just build it up in memory */
static void output_line(struct bb_state *state, const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        vprintf(fmt, args);
        va_end(args);
}

static void output_label(struct bb_state *state, const char *fmt, ...)
{
        static char buffer[512];
        va_list args;

        va_start(args, fmt);
        vsnprintf(buffer, sizeof(buffer), fmt, args);
        va_end(args);

        output_line(state, "%s:\n", buffer);
}

static void output_insn(struct bb_state *state, const char *fmt, ...)
{
        static char buffer[512];
        va_list args;

        va_start(args, fmt);
        vsnprintf(buffer, sizeof(buffer), fmt, args);
        va_end(args);

        output_line(state, "\t%s\n", buffer);
}

static void output_comment(struct bb_state *state, const char *fmt, ...)
{
        static char buffer[512];
        va_list args;

        if (!verbose)
                return;
        va_start(args, fmt);
        vsnprintf(buffer, sizeof(buffer), fmt, args);
        va_end(args);

        output_line(state, "\t# %s\n", buffer);
}

static const char *show_memop(struct storage *storage)
{
        static char buffer[1000];

        if (!storage)
                return "undef";
        switch (storage->type) {
        case REG_FRAME:
                sprintf(buffer, "%d(FP)", storage->offset);
                break;
        case REG_STACK:
                sprintf(buffer, "%d(SP)", storage->offset);
                break;
        case REG_REG:
                return hardregs[storage->regno].name;
        default:
                return show_storage(storage);
        }
        return buffer;
}

static void alloc_stack(struct bb_state *state, struct storage *storage)
{
        storage->type = REG_STACK;
        storage->offset = state->stack_offset;
        state->stack_offset += 4;
}

/*
 * Can we re-generate the pseudo, so that we don't need to
 * flush it to memory? We can regenerate:
 *  - immediates and symbol addresses
 *  - pseudos we got as input in non-registers
 *  - pseudos we've already saved off earlier..
 */
static int can_regenerate(struct bb_state *state, pseudo_t pseudo)
{
        struct storage_hash *in;

        switch (pseudo->type) {
        case PSEUDO_VAL:
        case PSEUDO_SYM:
                return 1;

        default:
                in = find_storage_hash(pseudo, state->inputs);
                if (in && in->storage->type != REG_REG)
                        return 1;
                in = find_storage_hash(pseudo, state->internal);
                if (in)
                        return 1;
        }
        return 0;
}

static void flush_one_pseudo(struct bb_state *state, struct hardreg *hardreg, pseudo_t pseudo)
{
        struct storage_hash *out;
        struct storage *storage;

        if (can_regenerate(state, pseudo))
                return;

        output_comment(state, "flushing %s from %s", show_pseudo(pseudo), hardreg->name);
        out = find_storage_hash(pseudo, state->internal);
        if (!out) {
                out = find_storage_hash(pseudo, state->outputs);
                if (!out)
                        out = find_or_create_hash(pseudo, &state->internal);
        }
        storage = out->storage;
        switch (storage->type) {
        default:
                /*
                 * Aieee - the next user wants it in a register, but we
                 * need to flush it to memory in between. Which means that
                 * we need to allocate an internal one, dammit..
                 */
                out = find_or_create_hash(pseudo, &state->internal);
                storage = out->storage;
                /* Fall through */
        case REG_UDEF:
                alloc_stack(state, storage);
                /* Fall through */
        case REG_STACK:
                output_insn(state, "movl %s,%s", hardreg->name, show_memop(storage));
                break;
        }
}

/* Flush a hardreg out to the storage it has.. */
static void flush_reg(struct bb_state *state, struct hardreg *hardreg)
{
        pseudo_t pseudo;

        if (!hardreg->busy)
                return;
        hardreg->busy = 0;
        hardreg->dead = 0;
        hardreg->used = 1;
        FOR_EACH_PTR(hardreg->contains, pseudo) {
                if (CURRENT_TAG(pseudo) & TAG_DEAD)
                        continue;
                if (!(CURRENT_TAG(pseudo) & TAG_DIRTY))
                        continue;
                flush_one_pseudo(state, hardreg, pseudo);
        } END_FOR_EACH_PTR(pseudo);
        free_ptr_list(&hardreg->contains);
}

static struct storage_hash *find_pseudo_storage(struct bb_state *state, pseudo_t pseudo, struct hardreg *reg)
{
        struct storage_hash *src;

        src = find_storage_hash(pseudo, state->internal);
        if (!src) {
                src = find_storage_hash(pseudo, state->inputs);
                if (!src) {
                        src = find_storage_hash(pseudo, state->outputs);
                        /* Undefined? Screw it! */
                        if (!src)
                                return NULL;

                        /*
                         * If we found output storage, it had better be local stack
                         * that we flushed to earlier..
                         */
                        if (src->storage->type != REG_STACK)
                                return NULL;
                }
        }

        /*
         * Incoming pseudo with out any pre-set storage allocation?
         * We can make up our own, and obviously prefer to get it
         * in the register we already selected (if it hasn't been
         * used yet).
         */
        if (src->storage->type == REG_UDEF) {
                if (reg && !reg->used) {
                        src->storage->type = REG_REG;
                        src->storage->regno = reg - hardregs;
                } else
                        alloc_stack(state, src->storage);
        }
        return src;
}

static void mark_reg_dead(struct bb_state *state, pseudo_t pseudo, struct hardreg *reg)
{
        pseudo_t p;

        FOR_EACH_PTR(reg->contains, p) {
                if (p != pseudo)
                        continue;
                if (CURRENT_TAG(p) & TAG_DEAD)
                        continue;
                output_comment(state, "marking pseudo %s in reg %s dead", show_pseudo(pseudo), reg->name);
                TAG_CURRENT(p, TAG_DEAD);
                reg->dead++;
        } END_FOR_EACH_PTR(p);
}

/* Fill a hardreg with the pseudo it has */
static struct hardreg *fill_reg(struct bb_state *state, struct hardreg *hardreg, pseudo_t pseudo)
{
        struct storage_hash *src;
        struct instruction *def;

        switch (pseudo->type) {
        case PSEUDO_VAL:
                output_insn(state, "movl $%lld,%s", pseudo->value, hardreg->name);
                break;
        case PSEUDO_SYM:
                output_insn(state, "movl $<%s>,%s", show_pseudo(pseudo), hardreg->name);
                break;
        case PSEUDO_ARG:
        case PSEUDO_REG:
                def = pseudo->def;
                if (def->opcode == OP_SETVAL) {
                        output_insn(state, "movl $<%s>,%s", show_pseudo(def->symbol), hardreg->name);
                        break;
                }
                src = find_pseudo_storage(state, pseudo, hardreg);
                if (!src)
                        break;
                if (src->flags & TAG_DEAD)
                        mark_reg_dead(state, pseudo, hardreg);
                output_insn(state, "mov.%d %s,%s", 32, show_memop(src->storage), hardreg->name);
                break;
        default:
                output_insn(state, "reload %s from %s", hardreg->name, show_pseudo(pseudo));
                break;
        }
        return hardreg;
}

static void add_pseudo_reg(struct bb_state *state, pseudo_t pseudo, struct hardreg *reg)
{
        output_comment(state, "added pseudo %s to reg %s", show_pseudo(pseudo), reg->name);
        add_ptr_list_tag(&reg->contains, pseudo, TAG_DIRTY);
        reg->busy++;
}

static int last_reg;

static struct hardreg *preferred_reg(struct bb_state *state, pseudo_t target)
{
        struct storage_hash *dst;

        dst = find_storage_hash(target, state->outputs);
        if (dst) {
                struct storage *storage = dst->storage;
                if (storage->type == REG_REG)
                        return hardregs + storage->regno;
        }
        return NULL;
}

static struct hardreg *empty_reg(struct bb_state *state)
{
        int i;
        struct hardreg *reg = hardregs;

        for (i = 0; i < REGNO; i++, reg++) {
                if (!reg->busy)
                        return reg;
        }
        return NULL;
}

static struct hardreg *target_reg(struct bb_state *state, pseudo_t pseudo, pseudo_t target)
{
        int i;
        struct hardreg *reg;

        /* First, see if we have a preferred target register.. */
        reg = preferred_reg(state, target);
        if (reg && !reg->busy)
                goto found;

        reg = empty_reg(state);
        if (reg)
                goto found;

        i = last_reg+1;
        if (i >= REGNO)
                i = 0;
        last_reg = i;
        reg = hardregs + i;
        flush_reg(state, reg);

found:
        add_pseudo_reg(state, pseudo, reg);
        return reg;
}

static struct hardreg *find_in_reg(struct bb_state *state, pseudo_t pseudo)
{
        int i;
        struct hardreg *reg;

        for (i = 0; i < REGNO; i++) {
                pseudo_t p;

                reg = hardregs + i;
                FOR_EACH_PTR(reg->contains, p) {
                        if (p == pseudo) {
                                last_reg = i;
                                output_comment(state, "found pseudo %s in reg %s", show_pseudo(pseudo), reg->name);
                                return reg;
                        }
                } END_FOR_EACH_PTR(p);
        }
        return NULL;
}

static struct hardreg *getreg(struct bb_state *state, pseudo_t pseudo, pseudo_t target)
{
        struct hardreg *reg;

        reg = find_in_reg(state, pseudo);
        if (reg)
                return reg;
        reg = target_reg(state, pseudo, target);
        return fill_reg(state, reg, pseudo);
}

static struct hardreg *copy_reg(struct bb_state *state, struct hardreg *src, pseudo_t target)
{
        int i;
        struct hardreg *reg;

        if (!src->busy)
                return src;

        reg = preferred_reg(state, target);
        if (reg && !reg->busy) {
                output_comment(state, "copying %s to preferred target %s", show_pseudo(target), reg->name);
                output_insn(state, "movl %s,%s", src->name, reg->name);
                return reg;
        }

        for (i = 0; i < REGNO; i++) {
                struct hardreg *reg = hardregs + i;
                if (!reg->busy) {
                        output_comment(state, "copying %s to %s", show_pseudo(target), reg->name);
                        output_insn(state, "movl %s,%s", src->name, reg->name);
                        return reg;
                }
        }

        flush_reg(state, src);
        return src;
}

static const char *generic(struct bb_state *state, pseudo_t pseudo)
{
        struct hardreg *reg;
        struct storage_hash *src;

        switch (pseudo->type) {
        case PSEUDO_SYM:
        case PSEUDO_VAL:
                return show_pseudo(pseudo);
        default:
                reg = find_in_reg(state, pseudo);
                if (reg)
                        return reg->name;
                src = find_pseudo_storage(state, pseudo, NULL);
                if (!src)
                        return "undef";
                return show_memop(src->storage);
        }
}

static const char *address(struct bb_state *state, struct instruction *memop)
{
        struct symbol *sym;
        struct hardreg *base;
        static char buffer[100];
        pseudo_t addr = memop->src;

        switch(addr->type) {
        case PSEUDO_SYM:
                sym = addr->sym;
                if (sym->ctype.modifiers & MOD_NONLOCAL) {
                        sprintf(buffer, "%s+%d", show_ident(sym->ident), memop->offset);
                        return buffer;
                }
                sprintf(buffer, "%d+%s(SP)", memop->offset, show_ident(sym->ident));
                return buffer;
        default:
                base = getreg(state, addr, NULL);
                sprintf(buffer, "%d(%s)", memop->offset, base->name);
                return buffer;
        }
}

static const char *reg_or_imm(struct bb_state *state, pseudo_t pseudo)
{
        switch(pseudo->type) {
        case PSEUDO_VAL:
                return show_pseudo(pseudo);
        default:
                return getreg(state, pseudo, NULL)->name;
        }
}

static const char* opcodes[] = {
        [OP_BADOP] = "bad_op",

        /* Fn entrypoint */
        [OP_ENTRY] = "<entry-point>",

        /* Terminator */
        [OP_RET] = "ret",
        [OP_BR] = "br",
        [OP_SWITCH] = "switch",
        [OP_INVOKE] = "invoke",
        [OP_COMPUTEDGOTO] = "jmp *",
        [OP_UNWIND] = "unwind",
        
        /* Binary */
        [OP_ADD] = "add",
        [OP_SUB] = "sub",
        [OP_MUL] = "mul",
        [OP_DIV] = "div",
        [OP_MOD] = "mod",
        [OP_SHL] = "shl",
        [OP_SHR] = "shr",
        
        /* Logical */
        [OP_AND] = "and",
        [OP_OR] = "or",
        [OP_XOR] = "xor",
        [OP_AND_BOOL] = "and-bool",
        [OP_OR_BOOL] = "or-bool",

        /* Binary comparison */
        [OP_SET_EQ] = "seteq",
        [OP_SET_NE] = "setne",
        [OP_SET_LE] = "setle",
        [OP_SET_GE] = "setge",
        [OP_SET_LT] = "setlt",
        [OP_SET_GT] = "setgt",
        [OP_SET_B] = "setb",
        [OP_SET_A] = "seta",
        [OP_SET_BE] = "setbe",
        [OP_SET_AE] = "setae",

        /* Uni */
        [OP_NOT] = "not",
        [OP_NEG] = "neg",

        /* Special three-input */
        [OP_SEL] = "select",
        
        /* Memory */
        [OP_MALLOC] = "malloc",
        [OP_FREE] = "free",
        [OP_ALLOCA] = "alloca",
        [OP_LOAD] = "load",
        [OP_STORE] = "store",
        [OP_SETVAL] = "set",
        [OP_GET_ELEMENT_PTR] = "getelem",

        /* Other */
        [OP_PHI] = "phi",
        [OP_PHISOURCE] = "phisrc",
        [OP_CAST] = "cast",
        [OP_PTRCAST] = "ptrcast",
        [OP_CALL] = "call",
        [OP_VANEXT] = "va_next",
        [OP_VAARG] = "va_arg",
        [OP_SLICE] = "slice",
        [OP_SNOP] = "snop",
        [OP_LNOP] = "lnop",
        [OP_NOP] = "nop",
        [OP_DEATHNOTE] = "dead",
        [OP_ASM] = "asm",

        /* Sparse tagging (line numbers, context, whatever) */
        [OP_CONTEXT] = "context",
};

static void kill_dead_reg(struct hardreg *reg)
{
        if (reg->dead) {
                pseudo_t p;
                
                FOR_EACH_PTR(reg->contains, p) {
                        if (CURRENT_TAG(p) & TAG_DEAD) {
                                DELETE_CURRENT_PTR(p);
                                reg->busy--;
                                reg->dead--;
                        }
                } END_FOR_EACH_PTR(p);
                PACK_PTR_LIST(&reg->contains);
                assert(!reg->dead);
        }
}

static struct hardreg *target_copy_reg(struct bb_state *state, struct hardreg *src, pseudo_t target)
{
        kill_dead_reg(src);
        return copy_reg(state, src, target);
}

static void do_binop(struct bb_state *state, struct instruction *insn, pseudo_t val1, pseudo_t val2)
{
        const char *op = opcodes[insn->opcode];
        struct hardreg *src = getreg(state, val1, insn->target);
        const char *src2 = generic(state, val2);
        struct hardreg *dst;

        dst = target_copy_reg(state, src, insn->target);
        output_insn(state, "%s.%d %s,%s", op, insn->size, src2, dst->name);
        add_pseudo_reg(state, insn->target, dst);
}

static void generate_binop(struct bb_state *state, struct instruction *insn)
{
        do_binop(state, insn, insn->src1, insn->src2);
}

static int is_dead_reg(struct bb_state *state, pseudo_t pseudo, struct hardreg *reg)
{
        pseudo_t p;
        FOR_EACH_PTR(reg->contains, p) {
                if (p == pseudo)
                        return CURRENT_TAG(p) & TAG_DEAD;
        } END_FOR_EACH_PTR(p);
        return 0;
}

/*
 * Commutative binops are much more flexible, since we can switch the
 * sources around to satisfy the target register, or to avoid having
 * to load one of them into a register..
 */
static void generate_commutative_binop(struct bb_state *state, struct instruction *insn)
{
        pseudo_t src1 = insn->src1, src2 = insn->src2;
        struct hardreg *reg1, *reg2 = find_in_reg(state, src2);

        if (!reg2)
                goto dont_switch;
        reg1 = find_in_reg(state, src1);
        if (!reg1)
                goto do_switch;
        if (!is_dead_reg(state, src2, reg2))
                goto dont_switch;
        if (!is_dead_reg(state, src1, reg1))
                goto do_switch;

        /* Both are dead. Is one preferrable? */
        if (reg2 != preferred_reg(state, insn->target))
                goto dont_switch;

do_switch:
        src1 = src2;
        src2 = insn->src1;
dont_switch:
        do_binop(state, insn, src1, src2);
}

/*
 * This marks a pseudo dead. It still stays on the hardreg list (the hardreg
 * still has its value), but it's scheduled to be killed after the next
 * "sequence point" when we call "kill_read_pseudos()"
 */
static void mark_pseudo_dead(struct bb_state *state, pseudo_t pseudo)
{
        int i;
        struct storage_hash *src;

        src = find_pseudo_storage(state, pseudo, NULL);
        if (src)
                src->flags |= TAG_DEAD;
        for (i = 0; i < REGNO; i++)
                mark_reg_dead(state, pseudo, hardregs + i);
}

static void kill_dead_pseudos(struct bb_state *state)
{
        int i;

        for (i = 0; i < REGNO; i++) {
                kill_dead_reg(hardregs + i);
        }
}

/*
 * A PHI source can define a pseudo that we already
 * have in another register. We need to invalidate the
 * old register so that we don't end up with the same
 * pseudo in "two places".
 */
static void remove_pseudo_reg(struct bb_state *state, pseudo_t pseudo)
{
        int i;

        output_comment(state, "pseudo %s died", show_pseudo(pseudo));
        for (i = 0; i < REGNO; i++) {
                struct hardreg *reg = hardregs + i;
                pseudo_t p;
                FOR_EACH_PTR(reg->contains, p) {
                        if (p != pseudo)
                                continue;
                        if (CURRENT_TAG(p) & TAG_DEAD)
                                reg->dead--;
                        reg->busy--;
                        DELETE_CURRENT_PTR(p);
                        output_comment(state, "removed pseudo %s from reg %s", show_pseudo(pseudo), reg->name);
                } END_FOR_EACH_PTR(p);
                PACK_PTR_LIST(&reg->contains);
        }
}

static void generate_store(struct instruction *insn, struct bb_state *state)
{
        output_insn(state, "mov.%d %s,%s", insn->size, reg_or_imm(state, insn->target), address(state, insn));
}

static void generate_load(struct instruction *insn, struct bb_state *state)
{
        const char *input = address(state, insn);
        struct hardreg *dst;

        kill_dead_pseudos(state);
        dst = target_reg(state, insn->target, NULL);
        output_insn(state, "mov.%d %s,%s", insn->size, input, dst->name);
}

static void generate_phisource(struct instruction *insn, struct bb_state *state)
{
        struct instruction *user;
        struct hardreg *reg;

        /* Mark all the target pseudos dead first */
        FOR_EACH_PTR(insn->phi_users, user) {
                mark_pseudo_dead(state, user->target);
        } END_FOR_EACH_PTR(user);

        reg = NULL;
        FOR_EACH_PTR(insn->phi_users, user) {
                if (!reg)
                        reg = getreg(state, insn->phi_src, user->target);
                remove_pseudo_reg(state, user->target);
                add_pseudo_reg(state, user->target, reg);
        } END_FOR_EACH_PTR(user);
}

static void generate_cast(struct bb_state *state, struct instruction *insn)
{
        struct hardreg *src = getreg(state, insn->src, insn->target);
        struct hardreg *dst;
        unsigned int old = insn->orig_type ? insn->orig_type->bit_size : 0;
        unsigned int new = insn->size;

        /*
         * Cast to smaller type? Ignore the high bits, we
         * just keep both pseudos in the same register.
         */
        if (old >= new) {
                add_pseudo_reg(state, insn->target, src);
                return;
        }

        dst = target_copy_reg(state, src, insn->target);

        if (insn->orig_type && (insn->orig_type->ctype.modifiers & MOD_SIGNED)) {
                output_insn(state, "sext.%d.%d %s", old, new, dst->name);
        } else {
                unsigned long long mask;
                mask = ~(~0ULL << old);
                mask &= ~(~0ULL << new);
                output_insn(state, "andl.%d $%#llx,%s", insn->size, mask, dst->name);
        }
        add_pseudo_reg(state, insn->target, dst);
}

static void generate_output_storage(struct bb_state *state);

static void generate_branch(struct bb_state *state, struct instruction *br)
{
        if (br->cond) {
                struct hardreg *reg = getreg(state, br->cond, NULL);
                output_insn(state, "testl %s,%s", reg->name, reg->name);
        }
        generate_output_storage(state);
        if (br->cond)
                output_insn(state, "je .L%p", br->bb_false);
        output_insn(state, "jmp .L%p", br->bb_true);
}

/* We've made sure that there is a dummy reg live for the output */
static void generate_switch(struct bb_state *state, struct instruction *insn)
{
        struct hardreg *reg = hardregs + SWITCH_REG;

        generate_output_storage(state);
        output_insn(state, "switch on %s", reg->name);
        output_insn(state, "unimplemented: %s", show_instruction(insn));
}

static void generate_ret(struct bb_state *state, struct instruction *ret)
{
        if (ret->src && ret->src != VOID) {
                struct hardreg *wants = hardregs+0;
                struct hardreg *reg = getreg(state, ret->src, NULL);
                if (reg != wants)
                        output_insn(state, "movl %s,%s", reg->name, wants->name);
        }
        output_insn(state, "ret");
}

/*
 * Fake "call" linearization just as a taster..
 */
static void generate_call(struct bb_state *state, struct instruction *insn)
{
        int offset = 0;
        pseudo_t arg;

        FOR_EACH_PTR(insn->arguments, arg) {
                output_insn(state, "pushl %s", generic(state, arg));
                offset += 4;
        } END_FOR_EACH_PTR(arg);
        flush_reg(state, hardregs+0);
        flush_reg(state, hardregs+1);
        flush_reg(state, hardregs+2);
        output_insn(state, "call %s", show_pseudo(insn->func));
        if (offset)
                output_insn(state, "addl $%d,%%esp", offset);
        add_pseudo_reg(state, insn->target, hardregs+0);
}

static void generate_select(struct bb_state *state, struct instruction *insn)
{
        struct hardreg *src1, *src2, *cond, *dst;

        cond = getreg(state, insn->src1, NULL);
        output_insn(state, "testl %s,%s", cond->name, cond->name);

        src1 = getreg(state, insn->src2, NULL);
        dst = copy_reg(state, src1, insn->target);
        add_pseudo_reg(state, insn->target, dst);
        src2 = getreg(state, insn->src3, insn->target);
        output_insn(state, "sele %s,%s", src2->name, dst->name);
}

static void generate_one_insn(struct instruction *insn, struct bb_state *state)
{
        if (verbose)
                output_comment(state, "%s", show_instruction(insn));

        switch (insn->opcode) {
        case OP_ENTRY: {
                struct symbol *sym = insn->bb->ep->name;
                const char *name = show_ident(sym->ident);
                if (sym->ctype.modifiers & MOD_STATIC)
                        printf("\n\n%s:\n", name);
                else
                        printf("\n\n.globl %s\n%s:\n", name, name);
                break;
        }

        /*
         * OP_PHI doesn't actually generate any code. It has been
         * done by the storage allocator and the OP_PHISOURCE.
         */
        case OP_PHI:
                break;

        case OP_PHISOURCE:
                generate_phisource(insn, state);
                break;

        /*
         * OP_SETVAL likewise doesn't actually generate any
         * code. On use, the "def" of the pseudo will be
         * looked up.
         */
        case OP_SETVAL:
                break;

        case OP_STORE:
                generate_store(insn, state);
                break;

        case OP_LOAD:
                generate_load(insn, state);
                break;

        case OP_DEATHNOTE:
                mark_pseudo_dead(state, insn->target);
                return;

        case OP_ADD: case OP_MUL:
        case OP_AND: case OP_OR: case OP_XOR:
        case OP_AND_BOOL: case OP_OR_BOOL:
        case OP_SET_EQ: case OP_SET_NE:
                generate_commutative_binop(state, insn);
                break;

        case OP_SUB: case OP_DIV: case OP_MOD:
        case OP_SHL: case OP_SHR:
        case OP_SET_LE: case OP_SET_GE:
        case OP_SET_LT: case OP_SET_GT:
        case OP_SET_B:  case OP_SET_A:
        case OP_SET_BE: case OP_SET_AE:
                generate_binop(state, insn);
                break;

        case OP_CAST: case OP_PTRCAST:
                generate_cast(state, insn);
                break;

        case OP_SEL:
                generate_select(state, insn);
                break;

        case OP_BR:
                generate_branch(state, insn);
                break;

        case OP_SWITCH:
                generate_switch(state, insn);
                break;

        case OP_CALL:
                generate_call(state, insn);
                break;

        case OP_RET:
                generate_ret(state, insn);
                break;

        default:
                output_insn(state, "unimplemented: %s", show_instruction(insn));
                break;
        }
        kill_dead_pseudos(state);
}

#define VERY_BUSY 1000
#define REG_FIXED 2000

static void write_reg_to_storage(struct bb_state *state, struct hardreg *reg, pseudo_t pseudo, struct storage *storage)
{
        int i;
        struct hardreg *out;

        switch (storage->type) {
        case REG_REG:
                out = hardregs + storage->regno;
                if (reg == out)
                        return;
                output_insn(state, "movl %s,%s", reg->name, out->name);
                return;
        case REG_UDEF:
                if (reg->busy < VERY_BUSY) {
                        storage->type = REG_REG;
                        storage->regno = reg - hardregs;
                        reg->busy = REG_FIXED;
                        return;
                }

                /* Try to find a non-busy register.. */
                for (i = 0; i < REGNO; i++) {
                        out = hardregs + i;
                        if (out->busy)
                                continue;
                        output_insn(state, "movl %s,%s", reg->name, out->name);
                        storage->type = REG_REG;
                        storage->regno = i;
                        reg->busy = REG_FIXED;
                        return;
                }

                /* Fall back on stack allocation ... */
                alloc_stack(state, storage);
                /* Fallthroigh */
        default:
                output_insn(state, "movl %s,%s", reg->name, show_memop(storage));
                return;
        }
}

static void write_val_to_storage(struct bb_state *state, pseudo_t src, struct storage *storage)
{
        struct hardreg *out;

        switch (storage->type) {
        case REG_UDEF:
                alloc_stack(state, storage);
        default:
                output_insn(state, "movl %s,%s", show_pseudo(src), show_memop(storage));
                break;
        case REG_REG:
                out = hardregs + storage->regno;
                output_insn(state, "movl %s,%s", show_pseudo(src), out->name);
        }
}

static void fill_output(struct bb_state *state, pseudo_t pseudo, struct storage *out)
{
        int i;
        struct storage_hash *in;
        struct instruction *def;

        /* Is that pseudo a constant value? */
        switch (pseudo->type) {
        case PSEUDO_VAL:
                write_val_to_storage(state, pseudo, out);
                return;
        case PSEUDO_REG:
                def = pseudo->def;
                if (def->opcode == OP_SETVAL) {
                        write_val_to_storage(state, def->symbol, out);
                        return;
                }
        default:
                break;
        }

        /* See if we have that pseudo in a register.. */
        for (i = 0; i < REGNO; i++) {
                struct hardreg *reg = hardregs + i;
                pseudo_t p;

                FOR_EACH_PTR(reg->contains, p) {
                        if (p == pseudo) {
                                write_reg_to_storage(state, reg, pseudo, out);
                                return;
                        }
                } END_FOR_EACH_PTR(p);
        }

        /* Do we have it in another storage? */
        in = find_storage_hash(pseudo, state->internal);
        if (!in) {
                in = find_storage_hash(pseudo, state->inputs);
                /* Undefined? */
                if (!in)
                        return;
        }
        switch (out->type) {
        case REG_UDEF:
                *out = *in->storage;
                break;
        case REG_REG:
                output_insn(state, "movl %s,%s", show_memop(in->storage), hardregs[out->regno].name);
                break;
        default:
                if (out == in->storage)
                        break;
                if (out->type == in->storage->type == out->regno == in->storage->regno)
                        break;
                output_insn(state, "movl %s,%s", show_memop(in->storage), show_memop(out));
                break;
        }
        return;
}

static int final_pseudo_flush(struct bb_state *state, pseudo_t pseudo, struct hardreg *reg)
{
        struct storage_hash *hash;
        struct storage *out;
        struct hardreg *dst;

        /*
         * Since this pseudo is live at exit, we'd better have output 
         * storage for it..
         */
        hash = find_storage_hash(pseudo, state->outputs);
        if (!hash)
                return 1;
        out = hash->storage;

        /* If the output is in a register, try to get it there.. */
        if (out->type == REG_REG) {
                dst = hardregs + out->regno;
                /*
                 * Two good cases: nobody is using the right register,
                 * or we've already set it aside for output..
                 */
                if (!dst->busy || dst->busy > VERY_BUSY)
                        goto copy_to_dst;

                /* Aiee. Try to keep it in a register.. */
                dst = empty_reg(state);
                if (dst)
                        goto copy_to_dst;

                return 0;
        }

        /* If the output is undefined, let's see if we can put it in a register.. */
        if (out->type == REG_UDEF) {
                dst = empty_reg(state);
                if (dst) {
                        out->type = REG_REG;
                        out->regno = dst - hardregs;
                        goto copy_to_dst;
                }
                /* Uhhuh. Not so good. No empty registers right now */
                return 0;
        }

        /* If we know we need to flush it, just do so already .. */
        output_insn(state, "movl %s,%s", reg->name, show_memop(out));
        return 1;

copy_to_dst:
        if (reg == dst)
                return 1;
        output_insn(state, "movl %s,%s", reg->name, dst->name);
        add_pseudo_reg(state, pseudo, dst);
        return 1;
}

/*
 * This tries to make sure that we put all the pseudos that are
 * live on exit into the proper storage
 */
static void generate_output_storage(struct bb_state *state)
{
        struct storage_hash *entry;

        /* Go through the fixed outputs, making sure we have those regs free */
        FOR_EACH_PTR(state->outputs, entry) {
                struct storage *out = entry->storage;
                if (out->type == REG_REG) {
                        struct hardreg *reg = hardregs + out->regno;
                        pseudo_t p;
                        int flushme = 0;

                        reg->busy = REG_FIXED;
                        FOR_EACH_PTR(reg->contains, p) {
                                if (p == entry->pseudo) {
                                        flushme = -100;
                                        continue;
                                }
                                if (CURRENT_TAG(p) & TAG_DEAD)
                                        continue;

                                /* Try to write back the pseudo to where it should go ... */
                                if (final_pseudo_flush(state, p, reg)) {
                                        DELETE_CURRENT_PTR(p);
                                        reg->busy--;
                                        continue;
                                }
                                flushme++;
                        } END_FOR_EACH_PTR(p);
                        PACK_PTR_LIST(&reg->contains);
                        if (flushme > 0)
                                flush_reg(state, reg);
                }
        } END_FOR_EACH_PTR(entry);

        FOR_EACH_PTR(state->outputs, entry) {
                fill_output(state, entry->pseudo, entry->storage);
        } END_FOR_EACH_PTR(entry);
}

static void generate(struct basic_block *bb, struct bb_state *state)
{
        int i;
        struct storage_hash *entry;
        struct instruction *insn;

        for (i = 0; i < REGNO; i++) {
                free_ptr_list(&hardregs[i].contains);
                hardregs[i].busy = 0;
                hardregs[i].dead = 0;
                hardregs[i].used = 0;
        }

        FOR_EACH_PTR(state->inputs, entry) {
                struct storage *storage = entry->storage;
                const char *name = show_storage(storage);
                output_comment(state, "incoming %s in %s", show_pseudo(entry->pseudo), name);
                if (storage->type == REG_REG) {
                        int regno = storage->regno;
                        add_pseudo_reg(state, entry->pseudo, hardregs + regno);
                        name = hardregs[regno].name;
                }
        } END_FOR_EACH_PTR(entry);

        output_label(state, ".L%p", bb);
        FOR_EACH_PTR(bb->insns, insn) {
                if (!insn->bb)
                        continue;
                generate_one_insn(insn, state);
        } END_FOR_EACH_PTR(insn);

        if (verbose) {
                output_comment(state, "--- in ---");
                FOR_EACH_PTR(state->inputs, entry) {
                        output_comment(state, "%s <- %s", show_pseudo(entry->pseudo), show_storage(entry->storage));
                } END_FOR_EACH_PTR(entry);
                output_comment(state, "--- spill ---");
                FOR_EACH_PTR(state->internal, entry) {
                        output_comment(state, "%s <-> %s", show_pseudo(entry->pseudo), show_storage(entry->storage));
                } END_FOR_EACH_PTR(entry);
                output_comment(state, "--- out ---");
                FOR_EACH_PTR(state->outputs, entry) {
                        output_comment(state, "%s -> %s", show_pseudo(entry->pseudo), show_storage(entry->storage));
                } END_FOR_EACH_PTR(entry);
        }
        printf("\n");
}

static void generate_list(struct basic_block_list *list, unsigned long generation)
{
        struct basic_block *bb;
        FOR_EACH_PTR(list, bb) {
                if (bb->generation == generation)
                        continue;
                output_bb(bb, generation);
        } END_FOR_EACH_PTR(bb);
}

static void output_bb(struct basic_block *bb, unsigned long generation)
{
        struct bb_state state;

        bb->generation = generation;

        /* Make sure all parents have been generated first */
        generate_list(bb->parents, generation);

        state.inputs = gather_storage(bb, STOR_IN);
        state.outputs = gather_storage(bb, STOR_OUT);
        state.internal = NULL;
        state.stack_offset = 0;

        generate(bb, &state);

        free_ptr_list(&state.inputs);
        free_ptr_list(&state.outputs);

        /* Generate all children... */
        generate_list(bb->children, generation);
}

static void set_up_arch_entry(struct entrypoint *ep, struct instruction *entry)
{
        int i;
        pseudo_t arg;

        /*
         * We should set up argument sources here..
         *
         * Things like "first three arguments in registers" etc
         * are all for this place.
         */
        i = 0;
        FOR_EACH_PTR(entry->arg_list, arg) {
                struct storage *in = lookup_storage(entry->bb, arg, STOR_IN);
                if (!in) {
                        in = alloc_storage();
                        add_storage(in, entry->bb, arg, STOR_IN);
                }
                if (i < 3) {
                        in->type = REG_REG;
                        in->regno = i;
                } else {
                        in->type = REG_FRAME;
                        in->offset = (i-3)*4;
                }
                i++;
        } END_FOR_EACH_PTR(arg);
}

/*
 * Set up storage information for "return"
 *
 * Not strictly necessary, since the code generator will
 * certainly move the return value to the right register,
 * but it can help register allocation if the allocator
 * sees that the target register is going to return in %eax.
 */
static void set_up_arch_exit(struct basic_block *bb, struct instruction *ret)
{
        pseudo_t pseudo = ret->src;

        if (pseudo && pseudo != VOID) {
                struct storage *out = lookup_storage(bb, pseudo, STOR_OUT);
                if (!out) {
                        out = alloc_storage();
                        add_storage(out, bb, pseudo, STOR_OUT);
                }
                out->type = REG_REG;
                out->regno = 0;
        }
}

/*
 * Set up dummy/silly output storage information for a switch
 * instruction. We need to make sure that a register is available
 * when we generate code for switch, so force that by creating
 * a dummy output rule.
 */
static void set_up_arch_switch(struct basic_block *bb, struct instruction *insn)
{
        pseudo_t pseudo = insn->cond;
        struct storage *out = lookup_storage(bb, pseudo, STOR_OUT);
        if (!out) {
                out = alloc_storage();
                add_storage(out, bb, pseudo, STOR_OUT);
        }
        out->type = REG_REG;
        out->regno = SWITCH_REG;
}

static void arch_set_up_storage(struct entrypoint *ep)
{
        struct basic_block *bb;

        /* Argument storage etc.. */
        set_up_arch_entry(ep, ep->entry);

        FOR_EACH_PTR(ep->bbs, bb) {
                struct instruction *insn = last_instruction(bb->insns);
                if (!insn)
                        continue;
                switch (insn->opcode) {
                case OP_RET:
                        set_up_arch_exit(bb, insn);
                        break;
                case OP_SWITCH:
                        set_up_arch_switch(bb, insn);
                        break;
                default:
                        /* nothing */;
                }
        } END_FOR_EACH_PTR(bb);
}

static void output(struct entrypoint *ep)
{
        unsigned long generation = ++bb_generation;

        last_reg = -1;

        /* Set up initial inter-bb storage links */
        set_up_storage(ep);

        /* Architecture-specific storage rules.. */
        arch_set_up_storage(ep);

        /* Show the results ... */
        output_bb(ep->entry->bb, generation);

        /* Clear the storage hashes for the next function.. */
        free_storage();
}

static int compile(struct symbol_list *list)
{
        struct symbol *sym;
        FOR_EACH_PTR(list, sym) {
                struct entrypoint *ep;
                expand_symbol(sym);
                ep = linearize_symbol(sym);
                if (ep)
                        output(ep);
        } END_FOR_EACH_PTR(sym);
        
        return 0;
}

int main(int argc, char **argv)
{
        return compile(sparse(argc, argv));
}