[libfirm] / ir / be / bestack.c

/*
 * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @author      Sebastian Hack, Matthias Braun
 * @version     $Id$
 *
 * Handling of the stack frame. It is composed of three types:
 * 1) The type of the arguments which are pushed on the stack.
 * 2) The "between type" which consists of stuff the call of the
 *    function pushes on the stack (like the return address and
 *    the old base pointer for ia32).
 * 3) The Firm frame type which consists of all local variables
 *    and the spills.
 */
#include "config.h"

#include "bestack.h"
#include "beirg.h"
#include "besched.h"
#include "benode.h"
#include "bessaconstr.h"

#include "ircons_t.h"
#include "irnode_t.h"
#include "irgwalk.h"
#include "irgmod.h"

int be_get_stack_entity_offset(be_stack_layout_t *frame, ir_entity *ent,
                               int bias)
{
        ir_type *t = get_entity_owner(ent);
        int ofs    = get_entity_offset(ent);

        int index;

        /* Find the type the entity is contained in. */
        for (index = 0; index < N_FRAME_TYPES; ++index) {
                if (frame->order[index] == t)
                        break;
                /* Add the size of all the types below the one of the entity to the entity's offset */
                ofs += get_type_size_bytes(frame->order[index]);
        }

        /* correct the offset by the initial position of the frame pointer */
        ofs -= frame->initial_offset;

        /* correct the offset with the current bias. */
        ofs += bias;

        return ofs;
}

/**
 * Retrieve the entity with given offset from a frame type.
 */
static ir_entity *search_ent_with_offset(ir_type *t, int offset)
{
        int i, n;

        for (i = 0, n = get_compound_n_members(t); i < n; ++i) {
                ir_entity *ent = get_compound_member(t, i);
                if (get_entity_offset(ent) == offset)
                        return ent;
        }

        return NULL;
}

static int stack_frame_compute_initial_offset(be_stack_layout_t *frame)
{
        ir_type  *base = frame->between_type;
        ir_entity *ent = search_ent_with_offset(base, 0);

        if (ent == NULL) {
                frame->initial_offset = get_type_size_bytes(frame->frame_type);
        } else {
                frame->initial_offset = be_get_stack_entity_offset(frame, ent, 0);
        }

        return frame->initial_offset;
}

/**
 * Walker: finally lower all Sels of outer frame or parameter
 * entities.
 */
static void lower_outer_frame_sels(ir_node *sel, void *ctx)
{
        ir_node           *ptr;
        ir_entity         *ent;
        ir_type           *owner;
        be_stack_layout_t *layout;
        ir_graph          *irg;
        (void) ctx;

        if (! is_Sel(sel))
                return;

        ent    = get_Sel_entity(sel);
        owner  = get_entity_owner(ent);
        ptr    = get_Sel_ptr(sel);
        irg    = get_irn_irg(sel);
        layout = be_get_irg_stack_layout(irg);

        if (owner == layout->frame_type || owner == layout->arg_type) {
                /* found access to outer frame or arguments */
                int offset = be_get_stack_entity_offset(layout, ent, 0);

                if (offset != 0) {
                        ir_node  *bl   = get_nodes_block(sel);
                        dbg_info *dbgi = get_irn_dbg_info(sel);
                        ir_mode  *mode = get_irn_mode(sel);
                        ir_mode  *mode_UInt = get_reference_mode_unsigned_eq(mode);
                        ir_node  *cnst = new_r_Const_long(current_ir_graph, mode_UInt, offset);

                        ptr = new_rd_Add(dbgi, bl, ptr, cnst, mode);
                }
                exchange(sel, ptr);
        }
}

/**
 * A helper struct for the bias walker.
 */
typedef struct bias_walk {
        int           start_block_bias;  /**< The bias at the end of the start block. */
        int           between_size;
        ir_node      *start_block;  /**< The start block of the current graph. */
} bias_walk;

/**
 * Fix all stack accessing operations in the block bl.
 *
 * @param bl         the block to process
 * @param real_bias  the bias value
 *
 * @return the bias at the end of this block
 */
static int process_stack_bias(ir_node *bl, int real_bias)
{
        int                wanted_bias = real_bias;
        ir_graph          *irg         = get_Block_irg(bl);
        be_stack_layout_t *layout      = be_get_irg_stack_layout(irg);
        bool               sp_relative = layout->sp_relative;
        const arch_env_t  *arch_env    = be_get_irg_arch_env(irg);
        ir_node           *irn;

        sched_foreach(bl, irn) {
                int ofs;

                /*
                   Check, if the node relates to an entity on the stack frame.
                   If so, set the true offset (including the bias) for that
                   node.
                 */
                ir_entity *ent = arch_get_frame_entity(irn);
                if (ent != NULL) {
                        int bias   = sp_relative ? real_bias : 0;
                        int offset = be_get_stack_entity_offset(layout, ent, bias);
                        arch_set_frame_offset(irn, offset);
                }

                /*
                 * If the node modifies the stack pointer by a constant offset,
                 * record that in the bias.
                 */
                if (be_is_IncSP(irn)) {
                        ofs = be_get_IncSP_offset(irn);
                        /* fill in real stack frame size */
                        if (be_get_IncSP_align(irn)) {
                                /* patch IncSP to produce an aligned stack pointer */
                                ir_type *between_type = layout->between_type;
                                int      between_size = get_type_size_bytes(between_type);
                                int      alignment    = 1 << arch_env->stack_alignment;
                                int      delta        = (real_bias + ofs + between_size) & (alignment - 1);
                                assert(ofs >= 0);
                                if (delta > 0) {
                                        be_set_IncSP_offset(irn, ofs + alignment - delta);
                                        real_bias += alignment - delta;
                                }
                        } else {
                                /* adjust so real_bias corresponds with wanted_bias */
                                int delta = wanted_bias - real_bias;
                                assert(delta <= 0);
                                if (delta != 0) {
                                        be_set_IncSP_offset(irn, ofs + delta);
                                        real_bias += delta;
                                }
                        }
                        real_bias   += ofs;
                        wanted_bias += ofs;
                } else {
                        ofs = arch_get_sp_bias(irn);
                        if (ofs == SP_BIAS_RESET) {
                                real_bias   = 0;
                                wanted_bias = 0;
                        } else {
                                real_bias   += ofs;
                                wanted_bias += ofs;
                        }
                }
        }

        assert(real_bias == wanted_bias);
        return real_bias;
}

/**
 * Block-Walker: fix all stack offsets for all blocks
 * except the start block
 */
static void stack_bias_walker(ir_node *bl, void *data)
{
        bias_walk *bw = (bias_walk*)data;
        if (bl != bw->start_block) {
                process_stack_bias(bl, bw->start_block_bias);
        }
}

void be_abi_fix_stack_bias(ir_graph *irg)
{
        be_stack_layout_t *stack_layout = be_get_irg_stack_layout(irg);
        ir_type           *frame_tp;
        int                i;
        bias_walk          bw;

        stack_frame_compute_initial_offset(stack_layout);

        /* Determine the stack bias at the end of the start block. */
        bw.start_block_bias = process_stack_bias(get_irg_start_block(irg),
                                                 stack_layout->initial_bias);
        bw.between_size     = get_type_size_bytes(stack_layout->between_type);

        /* fix the bias is all other blocks */
        bw.start_block = get_irg_start_block(irg);
        irg_block_walk_graph(irg, stack_bias_walker, NULL, &bw);

        /* fix now inner functions: these still have Sel node to outer
           frame and parameter entities */
        frame_tp = get_irg_frame_type(irg);
        for (i = get_class_n_members(frame_tp) - 1; i >= 0; --i) {
                ir_entity *ent = get_class_member(frame_tp, i);
                ir_graph  *irg = get_entity_irg(ent);

                if (irg != NULL) {
                        irg_walk_graph(irg, NULL, lower_outer_frame_sels, NULL);
                }
        }
}

typedef struct fix_stack_walker_env_t {
        ir_node **sp_nodes;
} fix_stack_walker_env_t;

/**
 * Walker. Collect all stack modifying nodes.
 */
static void collect_stack_nodes_walker(ir_node *node, void *data)
{
        ir_node                   *insn = node;
        fix_stack_walker_env_t    *env  = (fix_stack_walker_env_t*)data;
        const arch_register_req_t *req;

        if (is_Proj(node)) {
                insn = get_Proj_pred(node);
        }

        if (arch_get_irn_n_outs(insn) == 0)
                return;
        if (get_irn_mode(node) == mode_T)
                return;

        req = arch_get_irn_register_req(node);
        if (! (req->type & arch_register_req_type_produces_sp))
                return;

        ARR_APP1(ir_node*, env->sp_nodes, node);
}

void be_abi_fix_stack_nodes(ir_graph *irg)
{
        be_lv_t                   *lv       = be_get_irg_liveness(irg);
        const arch_env_t          *arch_env = be_get_irg_arch_env(irg);
        be_irg_t                  *birg     = be_birg_from_irg(irg);
        const arch_register_req_t *sp_req   = birg->sp_req;
        const arch_register_t     *sp       = arch_env->sp;
        be_ssa_construction_env_t  senv;
        int i, len;
        ir_node **phis;
        fix_stack_walker_env_t walker_env;

        if (sp_req == NULL) {
                struct obstack      *obst = be_get_be_obst(irg);
                arch_register_req_t *new_sp_req;
                unsigned            *limited_bitset;

                new_sp_req        = OALLOCZ(obst, arch_register_req_t);
                new_sp_req->type  = arch_register_req_type_limited
                                  | arch_register_req_type_produces_sp;
                new_sp_req->cls   = arch_register_get_class(arch_env->sp);
                new_sp_req->width = 1;

                limited_bitset = rbitset_obstack_alloc(obst, new_sp_req->cls->n_regs);
                rbitset_set(limited_bitset, arch_register_get_index(sp));
                new_sp_req->limited = limited_bitset;

                if (!rbitset_is_set(birg->allocatable_regs, sp->global_index)) {
                        new_sp_req->type |= arch_register_req_type_ignore;
                }

                sp_req = new_sp_req;
                birg->sp_req = new_sp_req;
        }

        walker_env.sp_nodes = NEW_ARR_F(ir_node*, 0);

        irg_walk_graph(irg, collect_stack_nodes_walker, NULL, &walker_env);

        /* nothing to be done if we didn't find any node, in fact we mustn't
         * continue, as for endless loops incsp might have had no users and is bad
         * now.
         */
        len = ARR_LEN(walker_env.sp_nodes);
        if (len == 0) {
                DEL_ARR_F(walker_env.sp_nodes);
                return;
        }

        be_ssa_construction_init(&senv, irg);
        be_ssa_construction_add_copies(&senv, walker_env.sp_nodes,
                                   ARR_LEN(walker_env.sp_nodes));
        be_ssa_construction_fix_users_array(&senv, walker_env.sp_nodes,
                                            ARR_LEN(walker_env.sp_nodes));

        if (lv != NULL) {
                len = ARR_LEN(walker_env.sp_nodes);
                for (i = 0; i < len; ++i) {
                        be_liveness_update(lv, walker_env.sp_nodes[i]);
                }
                be_ssa_construction_update_liveness_phis(&senv, lv);
        }

        phis = be_ssa_construction_get_new_phis(&senv);

        /* set register requirements for stack phis */
        len = ARR_LEN(phis);
        for (i = 0; i < len; ++i) {
                ir_node *phi = phis[i];
                be_set_phi_reg_req(phi, sp_req);
                arch_set_irn_register(phi, arch_env->sp);
        }
        be_ssa_construction_destroy(&senv);
        DEL_ARR_F(walker_env.sp_nodes);

        /* when doing code with frame-pointers then often the last incsp-nodes are
         * not used anymore because we copy the framepointer to the stack pointer
         * when leaving the function. Though the last incsp is often kept (because
         * you often don't know which incsp is the last one and fixstack should find
         * them all). Remove unnecessary keeps and IncSP nodes */
        {
                ir_node  *end    = get_irg_end(irg);
                int       arity  = get_irn_arity(end);
                int       i;
                for (i = arity-1; i >= 0; --i) {
                        ir_node *in = get_irn_n(end, i);
                        if (!be_is_IncSP(in)) {
                                continue;
                        }

                        remove_End_keepalive(end, in);
                        if (get_irn_n_edges(in) == 0) {
                                sched_remove(in);
                                kill_node(in);
                        }
                }
        }
}