- Don't use morgan spiller as default until it is as stable as belady spiller
[libfirm] / ir / be / bechordal.c
index 500e5a7..dc37f88 100644 (file)
 #include "config.h"
 #endif
 
+#ifdef HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+
+#ifdef HAVE_ALLOCA_H
+#include <alloca.h>
+#endif
+
 #include <ctype.h>
 
 #include "obst.h"
@@ -18,6 +26,7 @@
 #include "list.h"
 #include "bitset.h"
 #include "iterator.h"
+#include "bipartite.h"
 
 #include "irmode_t.h"
 #include "irgraph_t.h"
 #include "benumb_t.h"
 #include "besched_t.h"
 #include "belive_t.h"
+#include "benode_t.h"
 #include "bearch.h"
+#include "beirgmod.h"
 #include "beifg.h"
+#include "beinsn_t.h"
 
 #include "bechordal_t.h"
 #include "bechordal_draw.h"
 
 #define NO_COLOR (-1)
 
-#undef DUMP_INTERVALS
+#define MAX(x, y) ((x) > (y) ? (x) : (y))
+#define MIN(x, y) ((x) < (y) ? (x) : (y))
+
+#define DUMP_INTERVALS
 
 typedef struct _be_chordal_alloc_env_t {
        be_chordal_env_t *chordal_env;
 
-       bitset_t *live;                         /**< A liveness bitset. */
-       bitset_t *colors;                       /**< The color mask. */
-       bitset_t *in_colors;        /**< Colors used by live in values. */
-       int colors_n;               /**< The number of colors. */
+       pset *pre_colored;              /**< Set of precolored nodes. */
+       bitset_t *live;                             /**< A liveness bitset. */
+       bitset_t *tmp_colors;           /**< An auxiliary bitset which is as long as the number of colors in the class. */
+       bitset_t *colors;                           /**< The color mask. */
+       bitset_t *in_colors;            /**< Colors used by live in values. */
+       int colors_n;                   /**< The number of colors. */
+       DEBUG_ONLY(firm_dbg_module_t *constr_dbg;)  /**< Debug output for the constraint handler. */
 } be_chordal_alloc_env_t;
 
 #include "fourcc.h"
@@ -149,7 +167,416 @@ static INLINE border_t *border_add(be_chordal_env_t *env, struct list_head *head
  */
 static INLINE int has_reg_class(const be_chordal_env_t *env, const ir_node *irn)
 {
-  return arch_irn_has_reg_class(env->main_env->arch_env, irn, -1, env->cls);
+       return arch_irn_has_reg_class(env->birg->main_env->arch_env, irn, -1, env->cls);
+       // return arch_irn_consider_in_reg_alloc(env->birg->main_env->arch_env, env->cls, irn);
+}
+
+#define has_limited_constr(req, irn) \
+       (arch_get_register_req(arch_env, (req), irn, -1) && (req)->type == arch_register_req_type_limited)
+
+static int get_next_free_reg(const be_chordal_alloc_env_t *alloc_env, bitset_t *colors)
+{
+       bitset_t *tmp = alloc_env->tmp_colors;
+       bitset_copy(tmp, colors);
+       bitset_or(tmp, alloc_env->chordal_env->ignore_colors);
+       return bitset_next_clear(tmp, 0);
+}
+
+static bitset_t *get_decisive_partner_regs(bitset_t *bs, const be_operand_t *o1, const be_operand_t *o2)
+{
+       bitset_t *res = bs;
+
+       if(!o1) {
+               bitset_copy(bs, o2->regs);
+               return bs;
+       }
+
+       if(!o2) {
+               bitset_copy(bs, o1->regs);
+               return bs;
+       }
+
+       assert(o1->req.cls == o2->req.cls);
+
+       if(bitset_contains(o1->regs, o2->regs))
+               bitset_copy(bs, o1->regs);
+       else if(bitset_contains(o2->regs, o1->regs))
+               bitset_copy(bs, o2->regs);
+       else
+               res = NULL;
+
+       return res;
+}
+
+static be_insn_t *chordal_scan_insn(be_chordal_alloc_env_t *env, ir_node *irn)
+{
+       be_insn_env_t ie;
+
+       ie.ignore_colors = env->chordal_env->ignore_colors;
+       ie.aenv          = env->chordal_env->birg->main_env->arch_env;
+       ie.obst          = &env->chordal_env->obst;
+       ie.cls           = env->chordal_env->cls;
+       return be_scan_insn(&ie, irn);
+}
+
+static void pair_up_operands(const be_chordal_alloc_env_t *alloc_env, be_insn_t *insn)
+{
+       const be_chordal_env_t *env = alloc_env->chordal_env;
+
+       int n_uses         = be_insn_n_uses(insn);
+       int n_defs         = be_insn_n_defs(insn);
+       bitset_t *bs       = bitset_alloca(env->cls->n_regs);
+       bipartite_t *bp    = bipartite_new(n_defs, n_uses);
+       int *pairing       = alloca(MAX(n_defs, n_uses) * sizeof(pairing[0]));
+
+       int i, j;
+
+       /*
+               For each out operand, try to find an in operand which can be assigned the
+               same register as the out operand.
+       */
+       for(j = 0; j < insn->use_start; ++j) {
+               be_operand_t *out_op = &insn->ops[j];
+
+               /* Try to find an in operand which has ... */
+               for(i = insn->use_start; i < insn->n_ops; ++i) {
+                       const be_operand_t *op = &insn->ops[i];
+
+                       /*
+                       The in operand can only be paired with a def, if the node defining the
+                       operand's value does not interfere with the instruction itself. That
+                       would mean, that it is live at the instruction, so no result of the instruction
+                       can have the same register as the operand.
+
+                       Furthermore, tow operands can be paired, if the admissible registers
+                       of one are a subset of the other's. We record the operand whose constraints
+                       count in the decisive array.
+                       */
+                       if(!values_interfere(op->irn, op->carrier)) {
+                               if(get_decisive_partner_regs(bs, out_op, op))
+                                       bipartite_add(bp, j, i - insn->use_start);
+                       }
+               }
+       }
+
+       /* Compute the pairing. */
+       bipartite_matching(bp, pairing);
+       for(i = 0; i < insn->use_start; ++i) {
+               int p = pairing[i] + insn->use_start;
+
+               if(p >= insn->use_start) {
+                       insn->ops[i].partner = &insn->ops[p];
+                       insn->ops[p].partner = &insn->ops[i];
+               }
+       }
+
+       bipartite_free(bp);
+}
+
+
+static ir_node *pre_process_constraints(be_chordal_alloc_env_t *alloc_env, be_insn_t **the_insn)
+{
+       be_chordal_env_t *env       = alloc_env->chordal_env;
+       const arch_env_t *aenv      = env->birg->main_env->arch_env;
+       be_insn_t *insn             = *the_insn;
+       ir_node *bl                 = get_nodes_block(insn->irn);
+       ir_node *copy               = NULL;
+       ir_node *perm               = NULL;
+       bitset_t *out_constr        = bitset_alloca(env->cls->n_regs);
+       bitset_t *bs                = bitset_alloca(env->cls->n_regs);
+       DEBUG_ONLY(firm_dbg_module_t *dbg      = alloc_env->constr_dbg;)
+
+       int i;
+
+       assert(insn->has_constraints && "only do this for constrained nodes");
+
+       /*
+               Collect all registers that occur in output constraints.
+               This is necessary, since if the insn has one of these as an input constraint
+               and the corresponding operand interferes with the insn, the operand must
+               be copied.
+       */
+       for(i = 0; i < insn->use_start; ++i) {
+               be_operand_t *op = &insn->ops[i];
+               if(op->has_constraints)
+                       bitset_or(out_constr, op->regs);
+       }
+
+       /*
+               Now, figure out which input operand must be copied since it has input
+               constraints which are also output constraints.
+       */
+       for(i = insn->use_start; i < insn->n_ops; ++i) {
+               be_operand_t *op = &insn->ops[i];
+               if(op->has_constraints && (values_interfere(op->carrier, insn->irn) || arch_irn_is(aenv, op->carrier, ignore))) {
+                       bitset_copy(bs, op->regs);
+                       bitset_and(bs, out_constr);
+
+                       /*
+                               The operand (interfering with the node) has input constraints
+                               which also occur as output constraints, so insert a copy.
+                       */
+                       if(bitset_popcnt(bs) > 0) {
+                               copy        = be_new_Copy(op->req.cls, env->irg, bl, op->carrier);
+                               op->carrier = copy;
+                               sched_add_before(insn->irn, copy);
+                               set_irn_n(insn->irn, op->pos, op->carrier);
+
+                               DBG((dbg, LEVEL_2, "adding copy for interfering and constrained op %+F\n", op->carrier));
+                       }
+               }
+       }
+
+       /*
+               Make the Perm, recompute liveness and re-scan the insn since the
+               in operands are now the Projs of the Perm.
+       */
+       perm = insert_Perm_after(aenv, env->cls, env->dom_front, sched_prev(insn->irn));
+
+       /* Registers are propagated by insert_Perm_after(). Clean them here! */
+       if(perm) {
+               const ir_edge_t *edge;
+
+               foreach_out_edge(perm, edge) {
+                       ir_node *proj = get_edge_src_irn(edge);
+                       arch_set_irn_register(aenv, proj, NULL);
+               }
+
+               /*
+                       We also have to re-build the insn since the input operands are now the Projs of
+                       the Perm. Recomputing liveness is also a good idea if a Perm is inserted, since
+                       the live sets may change.
+               */
+               be_liveness(env->irg);
+               obstack_free(&env->obst, insn);
+               *the_insn = insn = chordal_scan_insn(alloc_env, insn->irn);
+
+               /*
+                       Copy the input constraints of the insn to the Perm as output
+                       constraints. Succeeding phases (coalescing will need that).
+               */
+               for(i = insn->use_start; i < insn->n_ops; ++i) {
+                       be_operand_t *op = &insn->ops[i];
+                       ir_node *proj = op->carrier;
+                       /*
+                               Note that the predecessor must not be a Proj of the Perm,
+                               since ignore-nodes are not Perm'ed.
+                       */
+                       if(op->has_constraints &&  is_Proj(proj) && get_Proj_pred(proj) == perm) {
+                               be_set_constr_limited(perm, BE_OUT_POS(get_Proj_proj(proj)), &op->req);
+                       }
+               }
+       }
+
+       return perm;
+}
+
+static ir_node *handle_constraints(be_chordal_alloc_env_t *alloc_env, ir_node *irn, int *silent)
+{
+       be_chordal_env_t *env  = alloc_env->chordal_env;
+       void *base             = obstack_base(&env->obst);
+       be_insn_t *insn        = chordal_scan_insn(alloc_env, irn);
+       ir_node *res           = insn->next_insn;
+       int be_silent          = *silent;
+
+       if(insn->pre_colored) {
+               int i;
+               for(i = 0; i < insn->use_start; ++i)
+                       pset_insert_ptr(alloc_env->pre_colored, insn->ops[i].carrier);
+       }
+
+       /*
+               If the current node is a barrier toggle the silent flag.
+               If we are in the start block, we are ought to be silent at the beginning,
+               so the toggling activates the constraint handling but skips the barrier.
+               If we are in the end block we handle the in requirements of the barrier
+               and set the rest to silent.
+       */
+       if(be_is_Barrier(irn))
+               *silent = !*silent;
+
+       if(be_silent)
+               goto end;
+
+       /*
+               Perms inserted before the constraint handling phase are considered to be
+               correctly precolored. These Perms arise during the ABI handling phase.
+       */
+       if(insn->has_constraints) {
+               const arch_env_t *aenv = env->birg->main_env->arch_env;
+               int n_regs             = env->cls->n_regs;
+               bitset_t *bs           = bitset_alloca(n_regs);
+               ir_node **alloc_nodes  = alloca(n_regs * sizeof(alloc_nodes[0]));
+               bipartite_t *bp        = bipartite_new(n_regs, n_regs);
+               int *assignment        = alloca(n_regs * sizeof(assignment[0]));
+               pmap *partners         = pmap_create();
+               DEBUG_ONLY(firm_dbg_module_t *dbg = alloc_env->constr_dbg;)
+
+               int i, n_alloc;
+               long col;
+               const ir_edge_t *edge;
+               ir_node *perm = NULL;
+
+               /*
+                       prepare the constraint handling of this node.
+                       Perms are constructed and Copies are created for constrained values
+                       interfering with the instruction.
+               */
+               perm = pre_process_constraints(alloc_env, &insn);
+
+               /* find suitable in operands to the out operands of the node. */
+               pair_up_operands(alloc_env, insn);
+
+               /*
+                       look at the in/out operands and add each operand (and its possible partner)
+                       to a bipartite graph (left: nodes with partners, right: admissible colors).
+               */
+               for(i = 0, n_alloc = 0; i < insn->n_ops; ++i) {
+                       be_operand_t *op = &insn->ops[i];
+
+                       /*
+                               If the operand has no partner or the partner has not been marked
+                               for allocation, determine the admissible registers and mark it
+                               for allocation by associating the node and its partner with the
+                               set of admissible registers via a bipartite graph.
+                       */
+                       if(!op->partner || !pmap_contains(partners, op->partner->carrier)) {
+
+                               pmap_insert(partners, op->carrier, op->partner ? op->partner->carrier : NULL);
+                               alloc_nodes[n_alloc] = op->carrier;
+
+                               DBG((dbg, LEVEL_2, "\tassociating %+F and %+F\n", op->carrier, op->partner ? op->partner->carrier : NULL));
+
+                               bitset_clear_all(bs);
+                               get_decisive_partner_regs(bs, op, op->partner);
+
+                               DBG((dbg, LEVEL_2, "\tallowed registers for %+F: %B\n", op->carrier, bs));
+
+                               bitset_foreach(bs, col)
+                                       bipartite_add(bp, n_alloc, col);
+
+                               n_alloc++;
+                       }
+               }
+
+               /*
+                       Put all nodes which live by the constrained instruction also to the
+                       allocation bipartite graph. They are considered unconstrained.
+               */
+               if(perm) {
+                       foreach_out_edge(perm, edge) {
+                               ir_node *proj = get_edge_src_irn(edge);
+
+                               assert(is_Proj(proj));
+
+                               if(values_interfere(proj, irn) && !pmap_contains(partners, proj)) {
+                                       assert(n_alloc < n_regs);
+                                       alloc_nodes[n_alloc] = proj;
+                                       pmap_insert(partners, proj, NULL);
+
+                                       bitset_clear_all(bs);
+                                       arch_put_non_ignore_regs(aenv, env->cls, bs);
+                                       bitset_foreach(bs, col)
+                                               bipartite_add(bp, n_alloc, col);
+
+                                       n_alloc++;
+                               }
+                       }
+               }
+
+               /* Compute a valid register allocation. */
+               bipartite_matching(bp, assignment);
+
+               /* Assign colors obtained from the matching. */
+               for(i = 0; i < n_alloc; ++i) {
+                       const arch_register_t *reg;
+                       ir_node *nodes[2];
+                       int j;
+
+                       assert(assignment[i] >= 0 && "there must have been a register assigned");
+                       reg = arch_register_for_index(env->cls, assignment[i]);
+
+                       nodes[0] = alloc_nodes[i];
+                       nodes[1] = pmap_get(partners, alloc_nodes[i]);
+
+                       for(j = 0; j < 2; ++j) {
+                               if(!nodes[j])
+                                       continue;
+
+                               arch_set_irn_register(aenv, nodes[j], reg);
+                               pset_hinsert_ptr(alloc_env->pre_colored, nodes[j]);
+                               DBG((dbg, LEVEL_2, "\tsetting %+F to register %s\n", nodes[j], reg->name));
+                       }
+               }
+
+
+               /* Allocate the non-constrained Projs of the Perm. */
+               if(perm) {
+
+                       bitset_clear_all(bs);
+
+                       /* Put the colors of all Projs in a bitset. */
+                       foreach_out_edge(perm, edge) {
+                               ir_node *proj              = get_edge_src_irn(edge);
+                               const arch_register_t *reg = arch_get_irn_register(aenv, proj);
+
+                               if(reg != NULL)
+                                       bitset_set(bs, reg->index);
+                       }
+
+                       /* Assign the not yet assigned Projs of the Perm a suitable color. */
+                       foreach_out_edge(perm, edge) {
+                               ir_node *proj              = get_edge_src_irn(edge);
+                               const arch_register_t *reg = arch_get_irn_register(aenv, proj);
+
+                               DBG((dbg, LEVEL_2, "\tchecking reg of %+F: %s\n", proj, reg ? reg->name : "<none>"));
+
+                               if(reg == NULL) {
+                                       col = get_next_free_reg(alloc_env, bs);
+                                       reg = arch_register_for_index(env->cls, col);
+                                       bitset_set(bs, reg->index);
+                                       arch_set_irn_register(aenv, proj, reg);
+                                       pset_insert_ptr(alloc_env->pre_colored, proj);
+                                       DBG((dbg, LEVEL_2, "\tsetting %+F to register %s\n", proj, reg->name));
+                               }
+                       }
+               }
+
+               pmap_destroy(partners);
+       }
+
+end:
+       obstack_free(&env->obst, base);
+       return res;
+}
+
+/**
+ * Handle constraint nodes in each basic block.
+ * handle_constraints() inserts Perm nodes which perm
+ * over all values live at the constrained node right in front
+ * of the constrained node. These Perms signal a constrained node.
+ * For further comments, refer to handle_constraints().
+ */
+static void constraints(ir_node *bl, void *data)
+{
+       be_chordal_alloc_env_t *env = data;
+
+       /*
+               Start silent in the start block.
+               The silence remains until the first barrier is seen.
+               Each other block is begun loud.
+       */
+       int silent                  = bl == get_irg_start_block(get_irn_irg(bl));
+       ir_node *irn;
+
+       /*
+               If the block is the start block search the barrier and
+               start handling constraints from there.
+       */
+
+       for(irn = sched_first(bl); !sched_is_end(irn);) {
+               irn = handle_constraints(env, irn, &silent);
+       }
 }
 
 /**
@@ -171,14 +598,14 @@ static void pressure(ir_node *block, void *env_ptr)
        be_chordal_alloc_env_t *alloc_env = env_ptr;
        be_chordal_env_t *env             = alloc_env->chordal_env;
        bitset_t *live                    = alloc_env->live;
-       firm_dbg_module_t *dbg            = env->dbg;
        ir_node *irn;
+       DEBUG_ONLY(firm_dbg_module_t *dbg            = env->dbg;)
 
        int i, n;
        unsigned step = 0;
        unsigned pressure = 0;
        struct list_head *head;
-       pset *live_in = put_live_in(block, pset_new_ptr_default());
+       pset *live_in  = put_live_in(block, pset_new_ptr_default());
        pset *live_end = put_live_end(block, pset_new_ptr_default());
 
        DBG((dbg, LEVEL_1, "Computing pressure in block %+F\n", block));
@@ -194,10 +621,10 @@ static void pressure(ir_node *block, void *env_ptr)
         * Make final uses of all values live out of the block.
         * They are necessary to build up real intervals.
         */
-       for(irn = pset_first(live_end); irn; irn = pset_next(live_end)) {
+       foreach_pset(live_end, irn) {
                if(has_reg_class(env, irn)) {
-                       DBG((dbg, LEVEL_3, "\tMaking live: %+F/%d\n", irn, get_irn_graph_nr(irn)));
-                       bitset_set(live, get_irn_graph_nr(irn));
+                       DBG((dbg, LEVEL_3, "\tMaking live: %+F/%d\n", irn, get_irn_idx(irn)));
+                       bitset_set(live, get_irn_idx(irn));
                        border_use(irn, step, 0);
                }
        }
@@ -209,14 +636,14 @@ static void pressure(ir_node *block, void *env_ptr)
         */
        sched_foreach_reverse(block, irn) {
                DBG((dbg, LEVEL_1, "\tinsn: %+F, pressure: %d\n", irn, pressure));
-               DBG((dbg, LEVEL_2, "\tlive: %b\n", live));
+               DBG((dbg, LEVEL_2, "\tlive: %B\n", live));
 
-           /*
-            * If the node defines some value, which can put into a
-            * register of the current class, make a border for it.
-            */
+               /*
+                * If the node defines some value, which can put into a
+                * register of the current class, make a border for it.
+                */
                if(has_reg_class(env, irn)) {
-                       int nr = get_irn_graph_nr(irn);
+                       int nr = get_irn_idx(irn);
 
                        bitset_clear(live, nr);
                        border_def(irn, step, 1);
@@ -230,14 +657,16 @@ static void pressure(ir_node *block, void *env_ptr)
                                ir_node *op = get_irn_n(irn, i);
 
                                if(has_reg_class(env, op)) {
-                                       int nr = get_irn_graph_nr(op);
-
-                                       DBG((dbg, LEVEL_4, "\t\tpos: %d, use: %+F\n", i, op));
+                                       int nr = get_irn_idx(op);
+                                       const char *msg = "-";
 
                                        if(!bitset_is_set(live, nr)) {
                                                border_use(op, step, 1);
                                                bitset_set(live, nr);
+                                               msg = "X";
                                        }
+
+                                       DBG((dbg, LEVEL_4, "\t\t%s pos: %d, use: %+F\n", msg, i, op));
                                }
                        }
                }
@@ -247,46 +676,45 @@ static void pressure(ir_node *block, void *env_ptr)
        /*
         * Add initial defs for all values live in.
         */
-       for(irn = pset_first(live_in); irn; irn = pset_next(live_in)) {
+       foreach_pset(live_in, irn) {
                if(has_reg_class(env, irn)) {
 
                        /* Mark the value live in. */
-                       bitset_set(live, get_irn_graph_nr(irn));
+                       bitset_set(live, get_irn_idx(irn));
 
                        /* Add the def */
                        border_def(irn, step, 0);
                }
        }
 
-
-  del_pset(live_in);
-  del_pset(live_end);
+       del_pset(live_in);
+       del_pset(live_end);
 }
 
 static void assign(ir_node *block, void *env_ptr)
 {
        be_chordal_alloc_env_t *alloc_env = env_ptr;
        be_chordal_env_t *env       = alloc_env->chordal_env;
-       firm_dbg_module_t *dbg      = env->dbg;
        bitset_t *live              = alloc_env->live;
        bitset_t *colors            = alloc_env->colors;
        bitset_t *in_colors         = alloc_env->in_colors;
-       const arch_env_t *arch_env  = env->main_env->arch_env;
+       const arch_env_t *arch_env  = env->birg->main_env->arch_env;
+       struct list_head *head      = get_block_border_head(env, block);
+       pset *live_in               = put_live_in(block, pset_new_ptr_default());
 
        const ir_node *irn;
        border_t *b;
-       struct list_head *head = get_block_border_head(env, block);
-       pset *live_in = put_live_in(block, pset_new_ptr_default());
+       DEBUG_ONLY(firm_dbg_module_t *dbg = env->dbg;)
 
-       bitset_clear_all(live);
        bitset_clear_all(colors);
+       bitset_clear_all(live);
        bitset_clear_all(in_colors);
 
        DBG((dbg, LEVEL_4, "Assigning colors for block %+F\n", block));
        DBG((dbg, LEVEL_4, "\tusedef chain for block\n"));
        list_for_each_entry(border_t, b, head, list) {
                DBG((dbg, LEVEL_4, "\t%s %+F/%d\n", b->is_def ? "def" : "use",
-                                       b->irn, get_irn_graph_nr(b->irn)));
+                                       b->irn, get_irn_idx(b->irn)));
        }
 
        /*
@@ -294,7 +722,7 @@ static void assign(ir_node *block, void *env_ptr)
         * Since their colors have already been assigned (The dominators were
         * allocated before), we have to mark their colors as used also.
         */
-       for(irn = pset_first(live_in); irn; irn = pset_next(live_in)) {
+       foreach_pset(live_in, irn) {
                if(has_reg_class(env, irn)) {
                        const arch_register_t *reg = arch_get_irn_register(arch_env, irn);
                        int col;
@@ -302,23 +730,27 @@ static void assign(ir_node *block, void *env_ptr)
                        assert(reg && "Node must have been assigned a register");
                        col = arch_register_get_index(reg);
 
+                       DBG((dbg, LEVEL_4, "%+F has reg %s\n", irn, reg->name));
+
                        /* Mark the color of the live in value as used. */
                        bitset_set(colors, col);
                        bitset_set(in_colors, col);
 
                        /* Mark the value live in. */
-                       bitset_set(live, get_irn_graph_nr(irn));
+                       bitset_set(live, get_irn_idx(irn));
                }
        }
 
        /*
-        * Mind that the sequence of defs from back to front defines a perfect
+        * Mind that the sequence
+        * of defs from back to front defines a perfect
         * elimination order. So, coloring the definitions from first to last
         * will work.
         */
        list_for_each_entry_reverse(border_t, b, head, list) {
                ir_node *irn = b->irn;
-               int nr = get_irn_graph_nr(irn);
+               int nr       = get_irn_idx(irn);
+               int ignore   = arch_irn_is(arch_env, irn, ignore);
 
                /*
                 * Assign a color, if it is a local def. Global defs already have a
@@ -328,20 +760,26 @@ static void assign(ir_node *block, void *env_ptr)
                        const arch_register_t *reg;
                        int col = NO_COLOR;
 
-                       DBG((dbg, LEVEL_4, "\tcolors in use: %b\n", colors));
-
-                       col = bitset_next_clear(colors, 0);
-                       reg = arch_register_for_index(env->cls, col);
+                       if(pset_find_ptr(alloc_env->pre_colored, irn) || ignore) {
+                               reg = arch_get_irn_register(arch_env, irn);
+                               col = reg->index;
+                               assert(!bitset_is_set(colors, col) && "pre-colored register must be free");
+                       }
 
-                       assert(arch_get_irn_register(arch_env, irn) == NULL && "This node must not have been assigned a register yet");
-                       assert(!bitset_is_set(live, nr) && "Value's definition must not have been encountered");
+                       else {
+                               col = get_next_free_reg(alloc_env, colors);
+                               reg = arch_register_for_index(env->cls, col);
+                               assert(arch_get_irn_register(arch_env, irn) == NULL && "This node must not have been assigned a register yet");
+                               assert(!arch_register_type_is(reg, ignore) && "Must not assign ignore register");
+                       }
 
                        bitset_set(colors, col);
-                       bitset_set(live, nr);
-
                        arch_set_irn_register(arch_env, irn, reg);
-                       DBG((dbg, LEVEL_1, "\tassigning register %s(%d) to %+F\n",
-            arch_register_get_name(reg), col, irn));
+
+                       DBG((dbg, LEVEL_1, "\tassigning register %s(%d) to %+F\n", arch_register_get_name(reg), col, irn));
+
+                       assert(!bitset_is_set(live, nr) && "Value's definition must not have been encountered");
+                       bitset_set(live, nr);
                }
 
                /* Clear the color upon a use. */
@@ -364,21 +802,34 @@ static void assign(ir_node *block, void *env_ptr)
 
 void be_ra_chordal_color(be_chordal_env_t *chordal_env)
 {
-       int node_count        = get_graph_node_count(chordal_env->irg);
+       be_chordal_alloc_env_t env;
+       char buf[256];
+
        int colors_n          = arch_register_class_n_regs(chordal_env->cls);
        ir_graph *irg         = chordal_env->irg;
-       void *base            = obstack_base(&chordal_env->obst);
 
-       be_chordal_alloc_env_t env;
 
-       if(get_irg_dom_state(irg) != dom_consistent)
-               compute_doms(irg);
+       assure_doms(irg);
+
+       env.chordal_env   = chordal_env;
+       env.colors_n      = colors_n;
+       env.colors        = bitset_alloca(colors_n);
+       env.tmp_colors    = bitset_alloca(colors_n);
+       env.in_colors     = bitset_alloca(colors_n);
+       env.pre_colored   = pset_new_ptr_default();
+       FIRM_DBG_REGISTER(env.constr_dbg, "firm.be.chordal.constr");
 
-       env.chordal_env  = chordal_env;
-       env.live         = bitset_obstack_alloc(&chordal_env->obst, node_count);
-       env.colors       = bitset_obstack_alloc(&chordal_env->obst, colors_n);
-       env.in_colors    = bitset_obstack_alloc(&chordal_env->obst, colors_n);
-       env.colors_n     = colors_n;
+
+       /* Handle register targeting constraints */
+       dom_tree_walk_irg(irg, constraints, NULL, &env);
+
+       if(chordal_env->opts->dump_flags & BE_CH_DUMP_CONSTR) {
+               snprintf(buf, sizeof(buf), "-%s-constr", chordal_env->cls->name);
+               be_dump(chordal_env->irg, buf, dump_ir_block_graph_sched);
+       }
+
+       be_numbering(irg);
+       env.live = bitset_malloc(get_irg_last_idx(chordal_env->irg));
 
        /* First, determine the pressure */
        dom_tree_walk_irg(irg, pressure, NULL, &env);
@@ -386,18 +837,15 @@ void be_ra_chordal_color(be_chordal_env_t *chordal_env)
        /* Assign the colors */
        dom_tree_walk_irg(irg, assign, NULL, &env);
 
-#ifdef DUMP_INTERVALS
-       {
-               char buf[128];
-       plotter_t *plotter;
+       be_numbering_done(irg);
 
-               ir_snprintf(buf, sizeof(buf), "ifg_%s_%F.eps", cls->name, irg);
-       plotter = new_plotter_ps(buf);
-
-       draw_interval_tree(&draw_chordal_def_opts, chordal_env, plotter, env->arch_env, cls);
-       plotter_free(plotter);
+       if(chordal_env->opts->dump_flags & BE_CH_DUMP_TREE_INTV) {
+               plotter_t *plotter;
+               ir_snprintf(buf, sizeof(buf), "ifg_%s_%F.eps", chordal_env->cls->name, irg);
+               plotter = new_plotter_ps(buf);
+               draw_interval_tree(&draw_chordal_def_opts, chordal_env, plotter);
+               plotter_free(plotter);
        }
-#endif
 
-       obstack_free(&chordal_env->obst, base);
+       del_pset(env.pre_colored);
 }