code.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

#include "debug.h"
#include "code.h"
#include "mem.h"
#include "desc.h"

struct Thunk* create_thunk(Code* expr, int frame_ptr, int root_frame_ptr)
{
    assert(expr != NULL);
    
    switch (expr->type) {
    case CT_APP:
    {
        // TODO: check over application
        // TODO: enforce strictness in ADT/Record

        VarEntry* var = &((AppEntry*) expr)->var;

        if (var->base.local_type == VAR_LOCAL) 
        {
            Thunk* basethunk = eval(local(frame_ptr, var->index));

            Desc* slice =
                    get_slice(basethunk->desc->type == FT_SLICE ?
                              ((SliceEntry*) basethunk->desc)->forward_ptr : basethunk->desc, basethunk->desc->arity + expr->nr_args);

            Thunk* thunk = updateF(NULL, slice);

            assert(thunk->desc->arity == basethunk->desc->arity + expr->nr_args);            

            for (int i = 0; i < basethunk->desc->arity; i++) {
                thunk->_args[i] = basethunk->_args[i];
            }

            for (int i = 0; i < expr->nr_args; i++) {
                thunk->_args[basethunk->desc->arity + i] 
                        = create_thunk(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a);
            }

            destroy_stack_frame(root_frame_ptr);
            return thunk;
        }
        else
        {
            Thunk* thunk = updateF(NULL, get_slice(var->f, expr->nr_args));

            assert(thunk->desc->arity == expr->nr_args);

            for (int i = 0; i < expr->nr_args; i++) {
                thunk->_args[i] = create_thunk(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a);
            }

            destroy_stack_frame(root_frame_ptr);
            return thunk;                    
        }
    }        
    case CT_VAR:
        if (expr->local_type == VAR_LOCAL) {
            Thunk* thunk = forward_to(NULL, local(frame_ptr, ((VarEntry*) expr)->index));
            destroy_stack_frame(root_frame_ptr);                        
            return thunk;
        }else{
            destroy_stack_frame(root_frame_ptr);
            return updateF(NULL, get_slice(((VarEntry*) expr)->f, 0));
        }
    case CT_LIT:
        destroy_stack_frame(root_frame_ptr);
        return updateT(NULL, &((LitEntry*) expr)->thunk);        
    }
}

void exec(Code* expr, int frame_ptr, int root_frame_ptr)
{
    while(1)
    {
        assert(expr != NULL);
        assert(stack_top_a < STACK_SIZE_A);
        
        switch (expr->type) {
        case CT_APP:
        {
            // TODO: check over application
            // TODO: enforce strictness in ADT/Record

            VarEntry* var = &((AppEntry*) expr)->var;

            if (var->base.local_type == VAR_LOCAL) 
            {
                // TODO: force
                
                Thunk* basethunk = eval(local(frame_ptr, var->index));

                Desc* slice =
                        get_slice(basethunk->desc->type == FT_SLICE ?
                                  ((SliceEntry*) basethunk->desc)->forward_ptr : basethunk->desc, basethunk->desc->arity + expr->nr_args);

                Thunk* thunk = updateF(get_dst(root_frame_ptr), slice);

                assert(thunk->desc->arity == basethunk->desc->arity + expr->nr_args);            

                for (int i = 0; i < basethunk->desc->arity; i++) {
                    thunk->_args[i] = basethunk->_args[i];
                }

                for (int i = 0; i < expr->nr_args; i++) {
                    thunk->_args[basethunk->desc->arity + i] 
                            = create_thunk(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a);
                }

                set_return(root_frame_ptr, thunk);
                destroy_stack_frame(root_frame_ptr);
                return;
            }
            else
            {
                Desc* slice = get_slice(var->f, expr->nr_args);
                
                if (slice->type == FT_PRIM) {
                    Thunk args[expr->nr_args];

                    for (int i = 0; i < expr->nr_args; i++) {
                        push_a(&args[i]);                        
                        exec(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a);
                    }

                    ((PrimEntry*) slice)->exec(root_frame_ptr);
                    destroy_stack_frame(root_frame_ptr);
                    return;
                }
                else if (slice->type == FT_FUN) {

                    int new_frame_ptr = stack_top_a;

                    for (int i = 0; i < expr->nr_args; i++) {
                        
                        if(is_strict_fun_arg((FunEntry*) slice, i))
                        {
                            push_a(NULL);
                            exec(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a);
                        }
                        else
                        {
                            push_a(create_thunk(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a));  
                        }
                    }
                    
                    expr = ((FunEntry*) slice)->body;
                    frame_ptr = new_frame_ptr;
                    continue;
                }
                else {
                    Thunk* thunk = updateF(get_dst(root_frame_ptr), slice);

                    assert(thunk->desc->arity == expr->nr_args);

                    for (int i = 0; i < expr->nr_args; i++) {
                        thunk->_args[i] 
                                = create_thunk(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a);
                    }
                    
                    set_return(root_frame_ptr, thunk);
                    destroy_stack_frame(root_frame_ptr);
                    return;                    
                }
            }
            break;
        }            
        case CT_VAR:
            if (expr->local_type == VAR_LOCAL) {
                Thunk* thunk = local(frame_ptr, ((VarEntry*) expr)->index);
                                
                while (thunk->desc == (Desc*) __FORWARD_PTR__) {
                    thunk = thunk->_forward_ptr;
                }

                forward_to(get_dst(root_frame_ptr), thunk);
                set_return(root_frame_ptr, thunk);
                
                if (thunk->desc->type == FT_FUN) {
                    
                    // Destroy stack frame before eval, it is not needed any more
                    // Greatly reduces stack usage
                    destroy_stack_frame(root_frame_ptr);                    
                    frame_ptr = stack_top_a;
                    // Here frame_ptr == root_frame_ptr
                    
                    for (int i = 0; i < thunk->desc->arity; i++) {
                        // TODO: handle strictness
                        push_a(thunk->_args[i]);
                    }
                    
                    expr = ((FunEntry*) thunk->desc)->body;
                    continue;
                }
                else if(thunk->desc->type == FT_PRIM) {

                    for (int i = 0; i < thunk->desc->arity; i++) {
                        // TODO: handle strictness
                        push_a(thunk->_args[i]);
                    }

                    ((PrimEntry*) thunk->desc)->exec(root_frame_ptr);
                }                
                
                destroy_stack_frame(root_frame_ptr);
                return;
            }else{
                // Safe to destroy, the next call has no arguments
                destroy_stack_frame(root_frame_ptr);
                
                Desc* slice = get_slice(((VarEntry*) expr)->f, 0);
                
                if(slice->type == FT_FUN)
                {
                    expr = ((FunEntry*)slice)->body;
                    continue;
                }
                else
                {                    
                    set_return(root_frame_ptr, updateF(get_dst(root_frame_ptr), slice));
                    return;
                }
            }
        case CT_LIT:
            set_return(root_frame_ptr, updateT(get_dst(root_frame_ptr), &((LitEntry*) expr)->thunk));
            destroy_stack_frame(root_frame_ptr);
            return;               
        case CT_SELECT:
        {
            push_a(NULL);
            exec(((SelectEntry*) expr)->expr, frame_ptr, stack_top_a);
            Thunk* pattern = eval(pop_a());

            bool handled = false;
            
            for (int i = 0; i < expr->nr_cases; i++) {
                SelectCaseEntry* caseEntry = &((SelectEntry*) expr)->cases[i];

                assert(pattern->desc->type == FT_ADT);
                
                if (caseEntry->type == SC_CONS) {
                    // Pattern match
                    if ((Desc*) caseEntry->cons != pattern->desc) continue;

                    // Put the constructor arguments to the stack if matches
                    for (int i = 0; i < pattern->desc->arity; i++) {
                        push_a(pattern->_args[i]);
                    }                  
                }
                else if (caseEntry->type == SC_LIT) {
                    printf("Exec: Unhandled entry type in CT_SELECT (SC_LIT)");
                    exit(-1);
                }
                
                // must be SC_DEFAULT now
                handled = true;
                expr = caseEntry->body;
                break;
            }

            if(handled) continue;
            
            printf("Exec: no select cases matches");
            print(pattern, false);
            exit(-1);
        }
        case CT_IF:
        {        
            Thunk tmp;
            tmp.desc = (Desc*) __BOOL__;

            push_a(&tmp);
            exec(((IfEntry*) expr)->cond, frame_ptr, stack_top_a);
            Thunk* cond = eval(pop_a());

            if (readB(cond)) {
                expr = ((IfEntry*) expr)->texpr;
                continue;                
            }
            else {
                expr = ((IfEntry*) expr)->fexpr;
                continue;     
            }
        }     
        default:
            printf("Exec: Unhandled CODE type");
            exit(-1);
        }
    
    }
}