small optimisation (avoid some arch_irn_consider_in_regalloc
[libfirm] / ir / be / benewalloc.c
index 89c844b..003032c 100644 (file)
  *    add copies and split live-ranges.
  *
  * TODO:
- *  - make use of free registers in the permutate_values code
- *  - We have to pessimistically construct Phi_0s when not all predecessors
- *    of a block are known.
- *  - Phi color assignment should give bonus points towards registers already
- *    assigned at predecessors.
+ *  - make use of free registers in the permute_values code
  *  - think about a smarter sequence of visiting the blocks. Sorted by
  *    execfreq might be good, or looptree from inner to outermost loops going
  *    over blocks in a reverse postorder
@@ -53,6 +49,7 @@
 
 #include <float.h>
 #include <stdbool.h>
+#include <math.h>
 
 #include "error.h"
 #include "execfreq.h"
 #include "irgraph_t.h"
 #include "irgwalk.h"
 #include "irnode_t.h"
+#include "irprintf.h"
 #include "obst.h"
+#include "raw_bitset.h"
+#include "unionfind.h"
+#include "pdeq.h"
+#include "hungarian.h"
 
 #include "beabi.h"
 #include "bechordal_t.h"
 #include "bespill.h"
 #include "bespillutil.h"
 #include "beverify.h"
+#include "beutil.h"
 
-#include "bipartite.h"
-#include "hungarian.h"
-
-#define USE_FACTOR         1.0f
-#define DEF_FACTOR         1.0f
-#define NEIGHBOR_FACTOR    0.2f
-#define AFF_SHOULD_BE_SAME 1.0f
-#define AFF_PHI            1.0f
+#define USE_FACTOR                     1.0f
+#define DEF_FACTOR                     1.0f
+#define NEIGHBOR_FACTOR                0.2f
+#define AFF_SHOULD_BE_SAME             0.5f
+#define AFF_PHI                        1.0f
+#define SPLIT_DELTA                    1.0f
+#define MAX_OPTIMISTIC_SPLIT_RECURSION 0
 
 DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)
 
@@ -96,16 +98,24 @@ static const arch_register_req_t   *default_cls_req;
 static be_lv_t                     *lv;
 static const ir_exec_freq          *execfreqs;
 static unsigned                     n_regs;
-static bitset_t                    *ignore_regs;
-
-/** info about the current assignment for a register */
-struct assignment_t {
-       ir_node *value;            /**< currently assigned value */
+static unsigned                    *normal_regs;
+static int                         *congruence_classes;
+static ir_node                    **block_order;
+static int                          n_block_order;
+static int                          create_preferences        = true;
+static int                          create_congruence_classes = true;
+static int                          propagate_phi_registers   = true;
+
+static const lc_opt_table_entry_t options[] = {
+       LC_OPT_ENT_BOOL("prefs", "use preference based coloring", &create_preferences),
+       LC_OPT_ENT_BOOL("congruences", "create congruence classes", &create_congruence_classes),
+       LC_OPT_ENT_BOOL("prop_phi", "propagate phi registers", &propagate_phi_registers),
+       LC_OPT_LAST
 };
-typedef struct assignment_t assignment_t;
 
-/** currently active assignments (while processing a basic block) */
-static assignment_t *assignments;
+/** currently active assignments (while processing a basic block)
+ * maps registers to values(their current copies) */
+static ir_node **assignments;
 
 /**
  * allocation information: last_uses, register preferences
@@ -128,8 +138,8 @@ typedef struct reg_pref_t reg_pref_t;
 
 /** per basic-block information */
 struct block_info_t {
-       bool         processed;       /**< indicate wether block is processed */
-       assignment_t assignments[0];  /**< register assignments at end of block */
+       bool     processed;       /**< indicate wether block is processed */
+       ir_node *assignments[0];  /**< register assignments at end of block */
 };
 typedef struct block_info_t block_info_t;
 
@@ -139,36 +149,33 @@ typedef struct block_info_t block_info_t;
  */
 static allocation_info_t *get_allocation_info(ir_node *node)
 {
-       allocation_info_t *info;
-       if (!irn_visited_else_mark(node)) {
-               size_t size = sizeof(info[0]) + n_regs * sizeof(info->prefs[0]);
-               info = obstack_alloc(&obst, size);
-               memset(info, 0, size);
+       allocation_info_t *info = get_irn_link(node);
+       if (info == NULL) {
+               info = OALLOCFZ(&obst, allocation_info_t, prefs, n_regs);
                info->current_value  = node;
                info->original_value = node;
                set_irn_link(node, info);
-       } else {
-               info = get_irn_link(node);
        }
 
        return info;
 }
 
+static allocation_info_t *try_get_allocation_info(const ir_node *node)
+{
+       return (allocation_info_t*) get_irn_link(node);
+}
+
 /**
  * Get allocation information for a basic block
  */
 static block_info_t *get_block_info(ir_node *block)
 {
-       block_info_t *info;
+       block_info_t *info = get_irn_link(block);
 
        assert(is_Block(block));
-       if (!irn_visited_else_mark(block)) {
-               size_t size = sizeof(info[0]) + n_regs * sizeof(info->assignments[0]);
-               info = obstack_alloc(&obst, size);
-               memset(info, 0, size);
+       if (info == NULL) {
+               info = OALLOCFZ(&obst, block_info_t, assignments, n_regs);
                set_irn_link(block, info);
-       } else {
-               info = get_irn_link(block);
        }
 
        return info;
@@ -181,8 +188,7 @@ static const arch_register_req_t *get_default_req_current_cls(void)
 {
        if (default_cls_req == NULL) {
                struct obstack      *obst = get_irg_obstack(irg);
-               arch_register_req_t *req  = obstack_alloc(obst, sizeof(*req));
-               memset(req, 0, sizeof(*req));
+               arch_register_req_t *req  = OALLOCZ(obst, arch_register_req_t);
 
                req->type = arch_register_req_type_normal;
                req->cls  = cls;
@@ -217,9 +223,10 @@ static void mark_as_copy_of(ir_node *copy, ir_node *value)
 
        /* the copy should not be linked to something else yet */
        assert(copy_info->original_value == copy);
+       copy_info->original_value = original;
+
        /* copy over allocation preferences */
        memcpy(copy_info->prefs, info->prefs, n_regs * sizeof(copy_info->prefs[0]));
-       copy_info->original_value = original;
 }
 
 /**
@@ -236,6 +243,7 @@ static void give_penalties_for_limits(const ir_nodeset_t *live_nodes,
 {
        ir_nodeset_iterator_t iter;
        unsigned              r;
+       unsigned              n_allowed;
        allocation_info_t     *info = get_allocation_info(node);
        ir_node               *neighbor;
 
@@ -251,8 +259,12 @@ static void give_penalties_for_limits(const ir_nodeset_t *live_nodes,
        if (live_nodes == NULL)
                return;
 
-       /* TODO: reduce penalty if there are multiple allowed registers... */
-       penalty *= NEIGHBOR_FACTOR;
+       penalty   *= NEIGHBOR_FACTOR;
+       n_allowed  = rbitset_popcnt(limited, n_regs);
+       if (n_allowed > 1) {
+               /* only create a very weak penalty if multiple regs are allowed */
+               penalty = (penalty * 0.8f) / n_allowed;
+       }
        foreach_ir_nodeset(live_nodes, neighbor, iter) {
                allocation_info_t *neighbor_info;
 
@@ -319,11 +331,16 @@ static void check_defs(const ir_nodeset_t *live_nodes, float weight,
                        if (!rbitset_is_set(&req->other_same, i))
                                continue;
 
-                       op      = get_irn_n(insn, i);
+                       op = get_irn_n(insn, i);
+
+                       /* if we the value at the should_be_same input doesn't die at the
+                        * node, then it is no use to propagate the constraints (since a
+                        * copy will emerge anyway) */
+                       if (ir_nodeset_contains(live_nodes, op))
+                               continue;
+
                        op_info = get_allocation_info(op);
                        for (r = 0; r < n_regs; ++r) {
-                               if (bitset_is_set(ignore_regs, r))
-                                       continue;
                                op_info->prefs[r] += info->prefs[r] * factor;
                        }
                }
@@ -352,8 +369,8 @@ static void analyze_block(ir_node *block, void *data)
                if (is_Phi(node))
                        break;
 
-               /* TODO give/take penalties for should_be_same/different) */
-               check_defs(&live_nodes, weight, node);
+               if (create_preferences)
+                       check_defs(&live_nodes, weight, node);
 
                /* mark last uses */
                arity = get_irn_arity(node);
@@ -380,30 +397,237 @@ static void analyze_block(ir_node *block, void *data)
 
                be_liveness_transfer(cls, node, &live_nodes);
 
-               /* update weights based on usage constraints */
+               if (create_preferences) {
+                       /* update weights based on usage constraints */
+                       for (i = 0; i < arity; ++i) {
+                               const arch_register_req_t *req;
+                               const unsigned            *limited;
+                               ir_node                   *op = get_irn_n(node, i);
+
+                               if (!arch_irn_consider_in_reg_alloc(cls, op))
+                                       continue;
+
+                               req = arch_get_register_req(node, i);
+                               if (!(req->type & arch_register_req_type_limited))
+                                       continue;
+
+                               limited = req->limited;
+                               give_penalties_for_limits(&live_nodes, weight * USE_FACTOR, limited,
+                                                                                 op);
+                       }
+               }
+       }
+
+       ir_nodeset_destroy(&live_nodes);
+}
+
+static void congruence_def(ir_nodeset_t *live_nodes, ir_node *node)
+{
+       const arch_register_req_t *req;
+
+       if (get_irn_mode(node) == mode_T) {
+               const ir_edge_t *edge;
+               foreach_out_edge(node, edge) {
+                       ir_node *def = get_edge_src_irn(edge);
+                       congruence_def(live_nodes, def);
+               }
+               return;
+       }
+
+       if (!arch_irn_consider_in_reg_alloc(cls, node))
+               return;
+
+       /* should be same constraint? */
+       req = arch_get_register_req_out(node);
+       if (req->type & arch_register_req_type_should_be_same) {
+               ir_node *insn  = skip_Proj(node);
+               int      arity = get_irn_arity(insn);
+               int      i;
+               unsigned node_idx = get_irn_idx(node);
+               node_idx          = uf_find(congruence_classes, node_idx);
+
                for (i = 0; i < arity; ++i) {
-                       const arch_register_req_t *req;
-                       const unsigned            *limited;
-                       ir_node                   *op = get_irn_n(node, i);
+                       ir_node               *live;
+                       ir_node               *op;
+                       int                    op_idx;
+                       ir_nodeset_iterator_t  iter;
+                       bool                   interferes = false;
 
-                       if (!arch_irn_consider_in_reg_alloc(cls, op))
+                       if (!rbitset_is_set(&req->other_same, i))
                                continue;
 
-                       req = arch_get_register_req(node, i);
-                       if (!(req->type & arch_register_req_type_limited))
+                       op     = get_irn_n(insn, i);
+                       op_idx = get_irn_idx(op);
+                       op_idx = uf_find(congruence_classes, op_idx);
+
+                       /* do we interfere with the value */
+                       foreach_ir_nodeset(live_nodes, live, iter) {
+                               int lv_idx = get_irn_idx(live);
+                               lv_idx     = uf_find(congruence_classes, lv_idx);
+                               if (lv_idx == op_idx) {
+                                       interferes = true;
+                                       break;
+                               }
+                       }
+                       /* don't put in same affinity class if we interfere */
+                       if (interferes)
                                continue;
 
-                       /* TODO: give penalties to neighbors for precolored nodes! */
+                       node_idx = uf_union(congruence_classes, node_idx, op_idx);
+                       DB((dbg, LEVEL_3, "Merge %+F and %+F congruence classes\n",
+                           node, op));
+                       /* one should_be_same is enough... */
+                       break;
+               }
+       }
+}
 
-                       limited = req->limited;
-                       give_penalties_for_limits(&live_nodes, weight * USE_FACTOR, limited,
-                                                 op);
+static void create_congurence_class(ir_node *block, void *data)
+{
+       ir_nodeset_t  live_nodes;
+       ir_node      *node;
+
+       (void) data;
+       ir_nodeset_init(&live_nodes);
+       be_liveness_end_of_block(lv, cls, block, &live_nodes);
+
+       /* check should be same constraints */
+       sched_foreach_reverse(block, node) {
+               if (is_Phi(node))
+                       break;
+
+               congruence_def(&live_nodes, node);
+               be_liveness_transfer(cls, node, &live_nodes);
+       }
+
+       /* check phi congruence classes */
+       sched_foreach_reverse_from(node, node) {
+               int i;
+               int arity;
+               int node_idx;
+               assert(is_Phi(node));
+
+               if (!arch_irn_consider_in_reg_alloc(cls, node))
+                       continue;
+
+               node_idx = get_irn_idx(node);
+               node_idx = uf_find(congruence_classes, node_idx);
+
+               arity = get_irn_arity(node);
+               for (i = 0; i < arity; ++i) {
+                       bool                  interferes = false;
+                       ir_nodeset_iterator_t iter;
+                       ir_node *live;
+                       ir_node *phi;
+                       ir_node *op     = get_Phi_pred(node, i);
+                       int      op_idx = get_irn_idx(op);
+                       op_idx = uf_find(congruence_classes, op_idx);
+
+                       /* do we interfere with the value */
+                       foreach_ir_nodeset(&live_nodes, live, iter) {
+                               int lv_idx = get_irn_idx(live);
+                               lv_idx     = uf_find(congruence_classes, lv_idx);
+                               if (lv_idx == op_idx) {
+                                       interferes = true;
+                                       break;
+                               }
+                       }
+                       /* don't put in same affinity class if we interfere */
+                       if (interferes)
+                               continue;
+                       /* any other phi has the same input? */
+                       sched_foreach(block, phi) {
+                               ir_node *oop;
+                               int      oop_idx;
+                               if (!is_Phi(phi))
+                                       break;
+                               if (!arch_irn_consider_in_reg_alloc(cls, phi))
+                                       continue;
+                               oop = get_Phi_pred(phi, i);
+                               if (oop == op)
+                                       continue;
+                               oop_idx = get_irn_idx(oop);
+                               oop_idx = uf_find(congruence_classes, oop_idx);
+                               if (oop_idx == op_idx) {
+                                       interferes = true;
+                                       break;
+                               }
+                       }
+                       if (interferes)
+                               continue;
+
+                       node_idx = uf_union(congruence_classes, node_idx, op_idx);
+                       DB((dbg, LEVEL_3, "Merge %+F and %+F congruence classes\n",
+                           node, op));
                }
        }
+}
 
-       ir_nodeset_destroy(&live_nodes);
+static void merge_congruence_prefs(ir_node *node, void *data)
+{
+       allocation_info_t *info;
+       allocation_info_t *head_info;
+       unsigned node_idx = get_irn_idx(node);
+       unsigned node_set = uf_find(congruence_classes, node_idx);
+       unsigned r;
+
+       (void) data;
+
+       /* head of congruence class or not in any class */
+       if (node_set == node_idx)
+               return;
+
+       if (!arch_irn_consider_in_reg_alloc(cls, node))
+               return;
+
+       head_info = get_allocation_info(get_idx_irn(irg, node_set));
+       info      = get_allocation_info(node);
+
+       for (r = 0; r < n_regs; ++r) {
+               head_info->prefs[r] += info->prefs[r];
+       }
 }
 
+static void set_congruence_prefs(ir_node *node, void *data)
+{
+       allocation_info_t *info;
+       allocation_info_t *head_info;
+       unsigned node_idx = get_irn_idx(node);
+       unsigned node_set = uf_find(congruence_classes, node_idx);
+
+       (void) data;
+
+       /* head of congruence class or not in any class */
+       if (node_set == node_idx)
+               return;
+
+       if (!arch_irn_consider_in_reg_alloc(cls, node))
+               return;
+
+       head_info = get_allocation_info(get_idx_irn(irg, node_set));
+       info      = get_allocation_info(node);
+
+       memcpy(info->prefs, head_info->prefs, n_regs * sizeof(info->prefs[0]));
+}
+
+static void combine_congruence_classes(void)
+{
+       size_t n = get_irg_last_idx(irg);
+       congruence_classes = XMALLOCN(int, n);
+       uf_init(congruence_classes, n);
+
+       /* create congruence classes */
+       irg_block_walk_graph(irg, create_congurence_class, NULL, NULL);
+       /* merge preferences */
+       irg_walk_graph(irg, merge_congruence_prefs, NULL, NULL);
+       irg_walk_graph(irg, set_congruence_prefs, NULL, NULL);
+       free(congruence_classes);
+}
+
+
+
+
+
 /**
  * Assign register reg to the given node.
  *
@@ -412,13 +636,25 @@ static void analyze_block(ir_node *block, void *data)
  */
 static void use_reg(ir_node *node, const arch_register_t *reg)
 {
-       unsigned      r          = arch_register_get_index(reg);
-       assignment_t *assignment = &assignments[r];
+       unsigned r = arch_register_get_index(reg);
+       assignments[r] = node;
+       arch_set_irn_register(node, reg);
+}
+
+static void free_reg_of_value(ir_node *node)
+{
+       const arch_register_t *reg;
+       unsigned               r;
 
-       //assert(assignment->value == NULL);
-       assignment->value = node;
+       if (!arch_irn_consider_in_reg_alloc(cls, node))
+               return;
 
-       arch_set_irn_register(node, reg);
+       reg        = arch_get_irn_register(node);
+       r          = arch_register_get_index(reg);
+       /* assignment->value may be NULL if a value is used at 2 inputs
+          so it gets freed twice. */
+       assert(assignments[r] == node || assignments[r] == NULL);
+       assignments[r] = NULL;
 }
 
 /**
@@ -442,9 +678,6 @@ static void fill_sort_candidates(reg_pref_t *regprefs,
 
        for (r = 0; r < n_regs; ++r) {
                float pref = info->prefs[r];
-               if (bitset_is_set(ignore_regs, r)) {
-                       pref = -10000;
-               }
                regprefs[r].num  = r;
                regprefs[r].pref = pref;
        }
@@ -452,18 +685,130 @@ static void fill_sort_candidates(reg_pref_t *regprefs,
        qsort(regprefs, n_regs, sizeof(regprefs[0]), compare_reg_pref);
 }
 
+static bool try_optimistic_split(ir_node *to_split, ir_node *before,
+                                 float pref, float pref_delta,
+                                 unsigned *forbidden_regs, int recursion)
+{
+       const arch_register_t *from_reg;
+       const arch_register_t *reg;
+       ir_node               *original_insn;
+       ir_node               *block;
+       ir_node               *copy;
+       unsigned               r;
+       unsigned               from_r;
+       unsigned               i;
+       allocation_info_t     *info = get_allocation_info(to_split);
+       reg_pref_t            *prefs;
+       float                  delta;
+       float                  split_threshold;
+
+       (void) pref;
+
+       /* stupid hack: don't optimisticallt split don't spill nodes...
+        * (so we don't split away the values produced because of
+        *  must_be_different constraints) */
+       original_insn = skip_Proj(info->original_value);
+       if (arch_irn_get_flags(original_insn) & arch_irn_flags_dont_spill)
+               return false;
+
+       from_reg        = arch_get_irn_register(to_split);
+       from_r          = arch_register_get_index(from_reg);
+       block           = get_nodes_block(before);
+       split_threshold = get_block_execfreq(execfreqs, block) * SPLIT_DELTA;
+
+       if (pref_delta < split_threshold*0.5)
+               return false;
+
+       /* find the best free position where we could move to */
+       prefs = ALLOCAN(reg_pref_t, n_regs);
+       fill_sort_candidates(prefs, info);
+       for (i = 0; i < n_regs; ++i) {
+               float apref;
+               float apref_delta;
+               bool  res;
+               bool  old_source_state;
+
+               /* we need a normal register which is not an output register
+                  an different from the current register of to_split */
+               r = prefs[i].num;
+               if (!rbitset_is_set(normal_regs, r))
+                       continue;
+               if (rbitset_is_set(forbidden_regs, r))
+                       continue;
+               if (r == from_r)
+                       continue;
+
+               /* is the split worth it? */
+               delta = pref_delta + prefs[i].pref;
+               if (delta < split_threshold) {
+                       DB((dbg, LEVEL_3, "Not doing optimistical split of %+F (depth %d), win %f too low\n",
+                               to_split, recursion, delta));
+                       return false;
+               }
+
+               /* if the register is free then we can do the split */
+               if (assignments[r] == NULL)
+                       break;
+
+               /* otherwise we might try recursively calling optimistic_split */
+               if (recursion+1 > MAX_OPTIMISTIC_SPLIT_RECURSION)
+                       continue;
+
+               apref        = prefs[i].pref;
+               apref_delta  = i+1 < n_regs ? apref - prefs[i+1].pref : 0;
+               apref_delta += pref_delta - split_threshold;
+
+               /* our source register isn't a usefull destination for recursive
+                  splits */
+               old_source_state = rbitset_is_set(forbidden_regs, from_r);
+               rbitset_set(forbidden_regs, from_r);
+               /* try recursive split */
+               res = try_optimistic_split(assignments[r], before, apref,
+                                          apref_delta, forbidden_regs, recursion+1);
+               /* restore our destination */
+               if (old_source_state) {
+                       rbitset_set(forbidden_regs, from_r);
+               } else {
+                       rbitset_clear(forbidden_regs, from_r);
+               }
+
+               if (res)
+                       break;
+       }
+       if (i >= n_regs)
+               return false;
+
+       reg  = arch_register_for_index(cls, r);
+       copy = be_new_Copy(cls, block, to_split);
+       mark_as_copy_of(copy, to_split);
+       /* hacky, but correct here */
+       if (assignments[arch_register_get_index(from_reg)] == to_split)
+               free_reg_of_value(to_split);
+       use_reg(copy, reg);
+       sched_add_before(before, copy);
+
+       DB((dbg, LEVEL_3,
+           "Optimistic live-range split %+F move %+F(%s) -> %s before %+F (win %f, depth %d)\n",
+           copy, to_split, from_reg->name, reg->name, before, delta, recursion));
+       return true;
+}
+
 /**
  * Determine and assign a register for node @p node
  */
-static void assign_reg(const ir_node *block, ir_node *node)
+static void assign_reg(const ir_node *block, ir_node *node,
+                       unsigned *forbidden_regs)
 {
        const arch_register_t     *reg;
        allocation_info_t         *info;
        const arch_register_req_t *req;
        reg_pref_t                *reg_prefs;
        ir_node                   *in_node;
-       unsigned                  i;
+       unsigned                   i;
+       const unsigned            *allowed_regs;
+       unsigned                   r;
 
+       assert(!is_Phi(node));
        assert(arch_irn_consider_in_reg_alloc(cls, node));
 
        /* preassigned register? */
@@ -496,52 +841,62 @@ static void assign_reg(const ir_node *block, ir_node *node)
                        reg = arch_get_irn_register(in);
                        assert(reg != NULL);
                        r = arch_register_get_index(reg);
-                       if (bitset_is_set(ignore_regs, r))
+
+                       /* if the value didn't die here then we should not propagate the
+                        * should_be_same info */
+                       if (assignments[r] == in)
                                continue;
+
                        info->prefs[r] += weight * AFF_SHOULD_BE_SAME;
                }
        }
 
+       /* create list of register candidates and sort by their preference */
        DB((dbg, LEVEL_2, "Candidates for %+F:", node));
        reg_prefs = alloca(n_regs * sizeof(reg_prefs[0]));
        fill_sort_candidates(reg_prefs, info);
        for (i = 0; i < n_regs; ++i) {
-               unsigned               num = reg_prefs[i].num;
-               const arch_register_t *reg = arch_register_for_index(cls, num);
+               unsigned num = reg_prefs[i].num;
+               const arch_register_t *reg;
+
+               if (!rbitset_is_set(normal_regs, num))
+                       continue;
+
+               reg = arch_register_for_index(cls, num);
                DB((dbg, LEVEL_2, " %s(%f)", reg->name, reg_prefs[i].pref));
        }
        DB((dbg, LEVEL_2, "\n"));
 
-       for (i = 0; i < n_regs; ++i) {
-               unsigned r = reg_prefs[i].num;
-               /* ignores are last and we should have at least 1 non-ignore left */
-               assert(!bitset_is_set(ignore_regs, r));
-               /* already used?
-                  TODO: It might be better to copy the value occupying the register
-                  around here instead of trying the next one, find out when... */
-               if (assignments[r].value != NULL)
-                       continue;
-               reg = arch_register_for_index(cls, r);
-               DB((dbg, LEVEL_2, "Assign %+F -> %s\n", node, reg->name));
-               use_reg(node, reg);
-               break;
+       allowed_regs = normal_regs;
+       if (req->type & arch_register_req_type_limited) {
+               allowed_regs = req->limited;
        }
-}
 
-static void free_reg_of_value(ir_node *node)
-{
-       assignment_t          *assignment;
-       const arch_register_t *reg;
-       unsigned               r;
+       for (i = 0; i < n_regs; ++i) {
+               float   pref, delta;
+               ir_node *before;
+               bool    res;
 
-       if (!arch_irn_consider_in_reg_alloc(cls, node))
-               return;
+               r = reg_prefs[i].num;
+               if (!rbitset_is_set(allowed_regs, r))
+                       continue;
+               if (assignments[r] == NULL)
+                       break;
+               pref   = reg_prefs[i].pref;
+               delta  = i+1 < n_regs ? pref - reg_prefs[i+1].pref : 0;
+               before = skip_Proj(node);
+               res    = try_optimistic_split(assignments[r], before,
+                                             pref, delta, forbidden_regs, 0);
+               if (res)
+                       break;
+       }
+       if (i >= n_regs) {
+               panic("No register left for %+F\n", node);
+       }
 
-       reg               = arch_get_irn_register(node);
-       r                 = arch_register_get_index(reg);
-       assignment        = &assignments[r];
-       assert(assignment->value == node);
-       assignment->value = NULL;
+       reg = arch_register_for_index(cls, r);
+       DB((dbg, LEVEL_2, "Assign %+F -> %s\n", node, reg->name));
+       use_reg(node, reg);
 }
 
 /**
@@ -578,26 +933,19 @@ static void free_reg_of_value(ir_node *node)
  *                     registers, the values in the array are the source
  *                     registers.
  */
-static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
+static void permute_values(ir_nodeset_t *live_nodes, ir_node *before,
                              unsigned *permutation)
 {
-       ir_node  **ins    = ALLOCANZ(ir_node*, n_regs);
        unsigned  *n_used = ALLOCANZ(unsigned, n_regs);
        ir_node   *block;
        unsigned   r;
 
-       /* create a list of permutations. Leave out fix points. */
+       /* determine how often each source register needs to be read */
        for (r = 0; r < n_regs; ++r) {
-               unsigned      old_reg = permutation[r];
-               assignment_t *assignment;
-               ir_node      *value;
+               unsigned  old_reg = permutation[r];
+               ir_node  *value;
 
-               /* no need to do anything for a fixpoint */
-               if (old_reg == r)
-                       continue;
-
-               assignment = &assignments[old_reg];
-               value      = assignment->value;
+               value = assignments[old_reg];
                if (value == NULL) {
                        /* nothing to do here, reg is not live. Mark it as fixpoint
                         * so we ignore it in the next steps */
@@ -605,13 +953,7 @@ static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
                        continue;
                }
 
-               ins[old_reg] = value;
                ++n_used[old_reg];
-
-               /* free occupation infos, we'll add the values back later */
-               if (live_nodes != NULL) {
-                       ir_nodeset_remove(live_nodes, value);
-               }
        }
 
        block = get_nodes_block(before);
@@ -631,7 +973,7 @@ static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
                }
 
                /* create a copy */
-               src = ins[old_r];
+               src  = assignments[old_r];
                copy = be_new_Copy(cls, block, src);
                sched_add_before(before, copy);
                reg = arch_register_for_index(cls, r);
@@ -651,6 +993,9 @@ static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
                assert(n_used[old_r] > 0);
                --n_used[old_r];
                if (n_used[old_r] == 0) {
+                       if (live_nodes != NULL) {
+                               ir_nodeset_remove(live_nodes, src);
+                       }
                        free_reg_of_value(src);
                }
 
@@ -690,8 +1035,8 @@ static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
                /* exchange old_r and r2; after that old_r is a fixed point */
                r2 = permutation[old_r];
 
-               in[0] = ins[r2];
-               in[1] = ins[old_r];
+               in[0] = assignments[r2];
+               in[1] = assignments[old_r];
                perm = be_new_Perm(cls, block, 2, in);
                sched_add_before(before, perm);
                DB((dbg, LEVEL_2, "Perm %+F (perm %+F,%+F, before %+F)\n",
@@ -701,27 +1046,23 @@ static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
                mark_as_copy_of(proj0, in[0]);
                reg = arch_register_for_index(cls, old_r);
                use_reg(proj0, reg);
-               if (live_nodes != NULL) {
-                       ir_nodeset_insert(live_nodes, proj0);
-               }
 
                proj1 = new_r_Proj(block, perm, get_irn_mode(in[1]), 1);
+               mark_as_copy_of(proj1, in[1]);
+               reg = arch_register_for_index(cls, r2);
+               use_reg(proj1, reg);
 
                /* 1 value is now in the correct register */
                permutation[old_r] = old_r;
                /* the source of r changed to r2 */
                permutation[r] = r2;
-               ins[r2] = in[1];
-               reg = arch_register_for_index(cls, r2);
-               if (r == r2) {
-                       /* if we have reached a fixpoint update data structures */
-                       mark_as_copy_of(proj1, in[1]);
-                       use_reg(proj1, reg);
-                       if (live_nodes != NULL) {
-                               ir_nodeset_insert(live_nodes, proj1);
-                       }
-               } else {
-                       arch_set_irn_register(proj1, reg);
+
+               /* if we have reached a fixpoint update data structures */
+               if (live_nodes != NULL) {
+                       ir_nodeset_remove(live_nodes, in[0]);
+                       ir_nodeset_remove(live_nodes, in[1]);
+                       ir_nodeset_remove(live_nodes, proj0);
+                       ir_nodeset_insert(live_nodes, proj1);
                }
        }
 
@@ -741,10 +1082,11 @@ static void permutate_values(ir_nodeset_t *live_nodes, ir_node *before,
  */
 static void free_last_uses(ir_nodeset_t *live_nodes, ir_node *node)
 {
-       allocation_info_t *info      = get_allocation_info(node);
-       const unsigned    *last_uses = &info->last_uses;
-       int                arity     = get_irn_arity(node);
-       int                i;
+       allocation_info_t     *info      = get_allocation_info(node);
+       const unsigned        *last_uses = &info->last_uses;
+       int                    arity     = get_irn_arity(node);
+       int                    i;
+
        for (i = 0; i < arity; ++i) {
                ir_node *op;
 
@@ -758,6 +1100,28 @@ static void free_last_uses(ir_nodeset_t *live_nodes, ir_node *node)
        }
 }
 
+/**
+ * change inputs of a node to the current value (copies/perms)
+ */
+static void rewire_inputs(ir_node *node)
+{
+       int i;
+       int arity = get_irn_arity(node);
+
+       for (i = 0; i < arity; ++i) {
+               ir_node           *op = get_irn_n(node, i);
+               allocation_info_t *info = try_get_allocation_info(op);
+
+               if (info == NULL)
+                       continue;
+
+               info = get_allocation_info(info->original_value);
+               if (info->current_value != op) {
+                       set_irn_n(node, i, info->current_value);
+               }
+       }
+}
+
 /**
  * Create a bitset of registers occupied with value living through an
  * instruction
@@ -771,8 +1135,9 @@ static void determine_live_through_regs(unsigned *bitset, ir_node *node)
 
        /* mark all used registers as potentially live-through */
        for (r = 0; r < n_regs; ++r) {
-               const assignment_t *assignment = &assignments[r];
-               if (assignment->value == NULL)
+               if (assignments[r] == NULL)
+                       continue;
+               if (!rbitset_is_set(normal_regs, r))
                        continue;
 
                rbitset_set(bitset, r);
@@ -799,17 +1164,17 @@ static void determine_live_through_regs(unsigned *bitset, ir_node *node)
  * @param  live_nodes  the set of live nodes, might be changed
  * @param  node        the current node
  */
-static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node)
+static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node,
+                                unsigned *forbidden_regs)
 {
        int arity = get_irn_arity(node);
-       int i, dummy, res;
+       int i, res;
        hungarian_problem_t *bp;
        unsigned l, r;
        unsigned *assignment;
 
        /* construct a list of register occupied by live-through values */
        unsigned *live_through_regs = NULL;
-       unsigned *output_regs       = NULL;
 
        /* see if any use constraints are not met */
        bool good = true;
@@ -856,11 +1221,9 @@ static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node)
                        if (live_through_regs == NULL) {
                                rbitset_alloca(live_through_regs, n_regs);
                                determine_live_through_regs(live_through_regs, node);
-
-                               rbitset_alloca(output_regs, n_regs);
                        }
 
-                       rbitset_or(output_regs, req->limited, n_regs);
+                       rbitset_or(forbidden_regs, req->limited, n_regs);
                        if (rbitsets_have_common(req->limited, live_through_regs, n_regs)) {
                                good = false;
                        }
@@ -873,9 +1236,7 @@ static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node)
                                determine_live_through_regs(live_through_regs, node);
                                if (rbitsets_have_common(req->limited, live_through_regs, n_regs)) {
                                        good = false;
-
-                                       rbitset_alloca(output_regs, n_regs);
-                                       rbitset_or(output_regs, req->limited, n_regs);
+                                       rbitset_or(forbidden_regs, req->limited, n_regs);
                                }
                        }
                }
@@ -885,30 +1246,31 @@ static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node)
                return;
 
        /* create these arrays if we haven't yet */
-       if (output_regs == NULL) {
-               if (live_through_regs == NULL) {
-                       rbitset_alloca(live_through_regs, n_regs);
-               }
-               rbitset_alloca(output_regs, n_regs);
+       if (live_through_regs == NULL) {
+               rbitset_alloca(live_through_regs, n_regs);
        }
 
        /* at this point we have to construct a bipartite matching problem to see
-          which values should go to which registers */
+        * which values should go to which registers
+        * Note: We're building the matrix in "reverse" - source registers are
+        *       right, destinations left because this will produce the solution
+        *       in the format required for permute_values.
+        */
        bp = hungarian_new(n_regs, n_regs, HUNGARIAN_MATCH_PERFECT);
 
        /* add all combinations, then remove not allowed ones */
        for (l = 0; l < n_regs; ++l) {
-               if (bitset_is_set(ignore_regs, l)) {
+               if (!rbitset_is_set(normal_regs, l)) {
                        hungarian_add(bp, l, l, 1);
                        continue;
                }
 
                for (r = 0; r < n_regs; ++r) {
-                       if (bitset_is_set(ignore_regs, r))
+                       if (!rbitset_is_set(normal_regs, r))
                                continue;
                        /* livethrough values may not use constrainted output registers */
                        if (rbitset_is_set(live_through_regs, l)
-                                       && rbitset_is_set(output_regs, r))
+                                       && rbitset_is_set(forbidden_regs, r))
                                continue;
 
                        hungarian_add(bp, r, l, l == r ? 9 : 8);
@@ -939,24 +1301,24 @@ static void enforce_constraints(ir_nodeset_t *live_nodes, ir_node *node)
                }
        }
 
-       hungarian_print_costmatrix(bp, 1);
+       //hungarian_print_cost_matrix(bp, 1);
        hungarian_prepare_cost_matrix(bp, HUNGARIAN_MODE_MAXIMIZE_UTIL);
 
        assignment = ALLOCAN(unsigned, n_regs);
-       res = hungarian_solve(bp, (int*) assignment, &dummy, 0);
+       res = hungarian_solve(bp, (int*) assignment, NULL, 0);
        assert(res == 0);
 
-#if 1
-       printf("Swap result:");
+#if 0
+       fprintf(stderr, "Swap result:");
        for (i = 0; i < (int) n_regs; ++i) {
-               printf(" %d", assignment[i]);
+               fprintf(stderr, " %d", assignment[i]);
        }
-       printf("\n");
+       fprintf(stderr, "\n");
 #endif
 
        hungarian_free(bp);
 
-       permutate_values(live_nodes, node, assignment);
+       permute_values(live_nodes, node, assignment);
 }
 
 /** test wether a node @p n is a copy of the value of node @p of */
@@ -980,11 +1342,10 @@ static bool is_copy_of(ir_node *value, ir_node *test_value)
  */
 static int find_value_in_block_info(block_info_t *info, ir_node *value)
 {
-       unsigned      r;
-       assignment_t *assignments = info->assignments;
+       unsigned   r;
+       ir_node  **assignments = info->assignments;
        for (r = 0; r < n_regs; ++r) {
-               const assignment_t *assignment = &assignments[r];
-               ir_node            *a_value    = assignment->value;
+               ir_node *a_value = assignments[r];
 
                if (a_value == NULL)
                        continue;
@@ -1001,12 +1362,12 @@ static int find_value_in_block_info(block_info_t *info, ir_node *value)
  */
 static void add_phi_permutations(ir_node *block, int p)
 {
-       unsigned  r;
-       unsigned *permutation;
-       assignment_t *old_assignments;
-       bool      need_permutation;
-       ir_node  *node;
-       ir_node  *pred = get_Block_cfgpred_block(block, p);
+       unsigned   r;
+       unsigned  *permutation;
+       ir_node  **old_assignments;
+       bool       need_permutation;
+       ir_node   *node;
+       ir_node   *pred = get_Block_cfgpred_block(block, p);
 
        block_info_t *pred_info = get_block_info(pred);
 
@@ -1032,7 +1393,10 @@ static void add_phi_permutations(ir_node *block, int p)
                        continue;
 
                op = get_Phi_pred(node, p);
-               a  = find_value_in_block_info(pred_info, op);
+               if (!arch_irn_consider_in_reg_alloc(cls, op))
+                       continue;
+
+               a = find_value_in_block_info(pred_info, op);
                assert(a >= 0);
 
                reg  = arch_get_irn_register(node);
@@ -1044,10 +1408,10 @@ static void add_phi_permutations(ir_node *block, int p)
        }
 
        if (need_permutation) {
-               /* permutate values at end of predecessor */
+               /* permute values at end of predecessor */
                old_assignments = assignments;
                assignments     = pred_info->assignments;
-               permutate_values(NULL, be_get_end_of_block_insertion_point(pred),
+               permute_values(NULL, be_get_end_of_block_insertion_point(pred),
                                                 permutation);
                assignments = old_assignments;
        }
@@ -1061,16 +1425,25 @@ static void add_phi_permutations(ir_node *block, int p)
                if (!arch_irn_consider_in_reg_alloc(cls, node))
                        continue;
 
-               /* we have permutated all values into the correct registers so we can
+               op = get_Phi_pred(node, p);
+               /* no need to do anything for Unknown inputs */
+               if (!arch_irn_consider_in_reg_alloc(cls, op))
+                       continue;
+
+               /* we have permuted all values into the correct registers so we can
                   simply query which value occupies the phis register in the
                   predecessor */
                a  = arch_register_get_index(arch_get_irn_register(node));
-               op = pred_info->assignments[a].value;
+               op = pred_info->assignments[a];
                set_Phi_pred(node, p, op);
        }
 }
 
-static void handle_phi_prefs(ir_node *phi)
+/**
+ * Set preferences for a phis register based on the registers used on the
+ * phi inputs.
+ */
+static void adapt_phi_prefs(ir_node *phi)
 {
        int i;
        int arity = get_irn_arity(phi);
@@ -1080,40 +1453,145 @@ static void handle_phi_prefs(ir_node *phi)
        for (i = 0; i < arity; ++i) {
                ir_node               *op  = get_irn_n(phi, i);
                const arch_register_t *reg = arch_get_irn_register(op);
-               ir_node               *pred;
+               ir_node               *pred_block;
+               block_info_t          *pred_block_info;
                float                  weight;
                unsigned               r;
 
                if (reg == NULL)
                        continue;
+               /* we only give the bonus if the predecessor already has registers
+                * assigned, otherwise we only see a dummy value
+                * and any conclusions about its register are useless */
+               pred_block = get_Block_cfgpred_block(block, i);
+               pred_block_info = get_block_info(pred_block);
+               if (!pred_block_info->processed)
+                       continue;
 
                /* give bonus for already assigned register */
-               pred   = get_Block_cfgpred_block(block, i);
-               weight = get_block_execfreq(execfreqs, pred);
+               weight = get_block_execfreq(execfreqs, pred_block);
                r      = arch_register_get_index(reg);
                info->prefs[r] += weight * AFF_PHI;
        }
 }
 
 /**
- * change inputs of a node to the current value (copies/perms)
+ * After a phi has been assigned a register propagate preference inputs
+ * to the phi inputs.
  */
-static void rewire_inputs(ir_node *node)
+static void propagate_phi_register(ir_node *phi, unsigned assigned_r)
 {
-       int i;
-       int arity = get_irn_arity(node);
+       int      i;
+       ir_node *block = get_nodes_block(phi);
+       int      arity = get_irn_arity(phi);
 
        for (i = 0; i < arity; ++i) {
-               ir_node           *op = get_irn_n(node, i);
-               allocation_info_t *info;
+               ir_node           *op         = get_Phi_pred(phi, i);
+               allocation_info_t *info       = get_allocation_info(op);
+               ir_node           *pred_block = get_Block_cfgpred_block(block, i);
+               unsigned           r;
+               float              weight
+                       = get_block_execfreq(execfreqs, pred_block) * AFF_PHI;
+
+               if (info->prefs[assigned_r] >= weight)
+                       continue;
 
-               if (!arch_irn_consider_in_reg_alloc(cls, op))
+               /* promote the prefered register */
+               for (r = 0; r < n_regs; ++r) {
+                       if (info->prefs[r] > -weight) {
+                               info->prefs[r] = -weight;
+                       }
+               }
+               info->prefs[assigned_r] = weight;
+
+               if (is_Phi(op))
+                       propagate_phi_register(op, assigned_r);
+       }
+}
+
+static void assign_phi_registers(ir_node *block)
+{
+       int                  n_phis = 0;
+       int                  n;
+       int                  res;
+       int                 *assignment;
+       ir_node             *node;
+       hungarian_problem_t *bp;
+
+       /* count phi nodes */
+       sched_foreach(block, node) {
+               if (!is_Phi(node))
+                       break;
+               if (!arch_irn_consider_in_reg_alloc(cls, node))
                        continue;
+               ++n_phis;
+       }
 
-               info = get_allocation_info(op);
-               if (info->current_value != op) {
-                       set_irn_n(node, i, info->current_value);
+       if (n_phis == 0)
+               return;
+
+       /* build a bipartite matching problem for all phi nodes */
+       bp = hungarian_new(n_phis, n_regs, HUNGARIAN_MATCH_PERFECT);
+       n  = 0;
+       sched_foreach(block, node) {
+               unsigned r;
+
+               allocation_info_t *info;
+               if (!is_Phi(node))
+                       break;
+               if (!arch_irn_consider_in_reg_alloc(cls, node))
+                       continue;
+
+               /* give boni for predecessor colorings */
+               adapt_phi_prefs(node);
+               /* add stuff to bipartite problem */
+               info = get_allocation_info(node);
+               DB((dbg, LEVEL_3, "Prefs for %+F: ", node));
+               for (r = 0; r < n_regs; ++r) {
+                       float costs;
+
+                       if (!rbitset_is_set(normal_regs, r))
+                               continue;
+
+                       costs = info->prefs[r];
+                       costs = costs < 0 ? -logf(-costs+1) : logf(costs+1);
+                       costs *= 100;
+                       costs += 10000;
+                       hungarian_add(bp, n, r, costs);
+                       DB((dbg, LEVEL_3, " %s(%f)", arch_register_for_index(cls, r)->name,
+                                               info->prefs[r]));
                }
+               DB((dbg, LEVEL_3, "\n"));
+               ++n;
+       }
+
+       //hungarian_print_cost_matrix(bp, 7);
+       hungarian_prepare_cost_matrix(bp, HUNGARIAN_MODE_MAXIMIZE_UTIL);
+
+       assignment = ALLOCAN(int, n_regs);
+       res        = hungarian_solve(bp, assignment, NULL, 0);
+       assert(res == 0);
+
+       /* apply results */
+       n = 0;
+       sched_foreach(block, node) {
+               unsigned               r;
+               const arch_register_t *reg;
+
+               if (!is_Phi(node))
+                       break;
+               if (!arch_irn_consider_in_reg_alloc(cls, node))
+                       continue;
+
+               r   = assignment[n++];
+               assert(rbitset_is_set(normal_regs, r));
+               reg = arch_register_for_index(cls, r);
+               DB((dbg, LEVEL_2, "Assign %+F -> %s\n", node, reg->name));
+               use_reg(node, reg);
+
+               /* adapt preferences for phi inputs */
+               if (propagate_phi_registers)
+                       propagate_phi_register(node, r);
        }
 }
 
@@ -1125,12 +1603,13 @@ static void allocate_coalesce_block(ir_node *block, void *data)
 {
        int                    i;
        ir_nodeset_t           live_nodes;
-       ir_nodeset_iterator_t  iter;
-       ir_node               *node, *start;
+       ir_node               *node;
        int                    n_preds;
        block_info_t          *block_info;
        block_info_t         **pred_block_infos;
        ir_node              **phi_ins;
+       unsigned              *forbidden_regs; /**< collects registers which must
+                                               not be used for optimistic splits */
 
        (void) data;
        DB((dbg, LEVEL_2, "* Block %+F\n", block));
@@ -1177,7 +1656,7 @@ static void allocate_coalesce_block(ir_node *block, void *data)
 
                                /* must live out of predecessor */
                                assert(a >= 0);
-                               phi_ins[p] = pred_info->assignments[a].value;
+                               phi_ins[p] = pred_info->assignments[a];
                                /* different value from last time? then we need a phi */
                                if (p > 0 && phi_ins[p-1] != phi_ins[p]) {
                                        need_phi = true;
@@ -1193,8 +1672,16 @@ static void allocate_coalesce_block(ir_node *block, void *data)
                        phi = new_r_Phi(block, n_preds, phi_ins, mode);
                        be_set_phi_reg_req(phi, req);
 
-                       DB((dbg, LEVEL_3, "Create Phi %+F (for %+F)\n", phi, node));
-
+                       DB((dbg, LEVEL_3, "Create Phi %+F (for %+F) -", phi, node));
+#ifdef DEBUG_libfirm
+                       {
+                               int i;
+                               for (i = 0; i < n_preds; ++i) {
+                                       DB((dbg, LEVEL_3, " %+F", phi_ins[i]));
+                               }
+                               DB((dbg, LEVEL_3, "\n"));
+                       }
+#endif
                        mark_as_copy_of(phi, node);
                        sched_add_after(block, phi);
 
@@ -1212,11 +1699,6 @@ static void allocate_coalesce_block(ir_node *block, void *data)
                /* if the node already has a register assigned use it */
                reg = arch_get_irn_register(node);
                if (reg != NULL) {
-                       /* TODO: consult pred-block infos here. The value could be copied
-                          away in some/all predecessor blocks. We need to construct
-                          phi-nodes in this case.
-                          We even need to construct some Phi_0 like constructs in cases
-                          where the predecessor allocation is not determined yet. */
                        use_reg(node, reg);
                }
 
@@ -1224,43 +1706,51 @@ static void allocate_coalesce_block(ir_node *block, void *data)
                ir_nodeset_insert(&live_nodes, node);
        }
 
-       /* handle phis... */
-       node = sched_first(block);
-       for ( ; is_Phi(node); node = sched_next(node)) {
-               const arch_register_t *reg;
+       rbitset_alloca(forbidden_regs, n_regs);
 
-               if (!arch_irn_consider_in_reg_alloc(cls, node))
-                       continue;
+       /* handle phis... */
+       assign_phi_registers(block);
 
-               /* fill in regs already assigned */
-               reg = arch_get_irn_register(node);
-               if (reg != NULL) {
-                       use_reg(node, reg);
-               } else {
-                       /* TODO: give boni for registers already assigned at the
-                          predecessors */
-                       handle_phi_prefs(node);
-                       assign_reg(block, node);
+       /* all live-ins must have a register */
+#ifdef DEBUG_libfirm
+       {
+               ir_nodeset_iterator_t  iter;
+               foreach_ir_nodeset(&live_nodes, node, iter) {
+                       const arch_register_t *reg = arch_get_irn_register(node);
+                       assert(reg != NULL);
                }
        }
-       start = node;
+#endif
 
-       /* assign regs for live-in values */
-       foreach_ir_nodeset(&live_nodes, node, iter) {
-               const arch_register_t *reg = arch_get_irn_register(node);
-               if (reg != NULL)
+       /* assign instructions in the block */
+       sched_foreach(block, node) {
+               int i;
+               int arity;
+
+               /* phis are already assigned */
+               if (is_Phi(node))
                        continue;
 
-               assign_reg(block, node);
-       }
+               rewire_inputs(node);
 
-       /* assign instructions in the block */
-       for (node = start; !sched_is_end(node); node = sched_next(node)) {
                /* enforce use constraints */
-               enforce_constraints(&live_nodes, node);
+               rbitset_clear_all(forbidden_regs, n_regs);
+               enforce_constraints(&live_nodes, node, forbidden_regs);
 
                rewire_inputs(node);
 
+               /* we may not use registers used for inputs for optimistic splits */
+               arity = get_irn_arity(node);
+               for (i = 0; i < arity; ++i) {
+                       ir_node *op = get_irn_n(node, i);
+                       const arch_register_t *reg;
+                       if (!arch_irn_consider_in_reg_alloc(cls, op))
+                               continue;
+
+                       reg = arch_get_irn_register(op);
+                       rbitset_set(forbidden_regs, arch_register_get_index(reg));
+               }
+
                /* free registers of values last used at this instruction */
                free_last_uses(&live_nodes, node);
 
@@ -1272,10 +1762,10 @@ static void allocate_coalesce_block(ir_node *block, void *data)
                                ir_node *proj = get_edge_src_irn(edge);
                                if (!arch_irn_consider_in_reg_alloc(cls, proj))
                                        continue;
-                               assign_reg(block, proj);
+                               assign_reg(block, proj, forbidden_regs);
                        }
                } else if (arch_irn_consider_in_reg_alloc(cls, node)) {
-                       assign_reg(block, node);
+                       assign_reg(block, node, forbidden_regs);
                }
        }
 
@@ -1284,7 +1774,7 @@ static void allocate_coalesce_block(ir_node *block, void *data)
 
        block_info->processed = true;
 
-       /* permutate values at end of predecessor blocks in case of phi-nodes */
+       /* permute values at end of predecessor blocks in case of phi-nodes */
        if (n_preds > 1) {
                int p;
                for (p = 0; p < n_preds; ++p) {
@@ -1307,26 +1797,148 @@ static void allocate_coalesce_block(ir_node *block, void *data)
        }
 }
 
+typedef struct block_costs_t block_costs_t;
+struct block_costs_t {
+       float costs;   /**< costs of the block */
+       int   dfs_num; /**< depth first search number (to detect backedges) */
+};
+
+static int cmp_block_costs(const void *d1, const void *d2)
+{
+       const ir_node       * const *block1 = d1;
+       const ir_node       * const *block2 = d2;
+       const block_costs_t *info1  = get_irn_link(*block1);
+       const block_costs_t *info2  = get_irn_link(*block2);
+       return QSORT_CMP(info2->costs, info1->costs);
+}
+
+static void determine_block_order(void)
+{
+       int i;
+       ir_node **blocklist = be_get_cfgpostorder(irg);
+       int       n_blocks  = ARR_LEN(blocklist);
+       int       dfs_num   = 0;
+       pdeq     *worklist  = new_pdeq();
+       ir_node **order     = XMALLOCN(ir_node*, n_blocks);
+       int       order_p   = 0;
+
+       /* clear block links... */
+       for (i = 0; i < n_blocks; ++i) {
+               ir_node *block = blocklist[i];
+               set_irn_link(block, NULL);
+       }
+
+       /* walk blocks in reverse postorder, the costs for each block are the
+        * sum of the costs of its predecessors (excluding the costs on backedges
+        * which we can't determine) */
+       for (i = n_blocks-1; i >= 0; --i) {
+               block_costs_t *cost_info;
+               ir_node *block = blocklist[i];
+
+               float execfreq   = get_block_execfreq(execfreqs, block);
+               float costs      = execfreq;
+               int   n_cfgpreds = get_Block_n_cfgpreds(block);
+               int   p;
+               for (p = 0; p < n_cfgpreds; ++p) {
+                       ir_node       *pred_block = get_Block_cfgpred_block(block, p);
+                       block_costs_t *pred_costs = get_irn_link(pred_block);
+                       /* we don't have any info for backedges */
+                       if (pred_costs == NULL)
+                               continue;
+                       costs += pred_costs->costs;
+               }
+
+               cost_info          = OALLOCZ(&obst, block_costs_t);
+               cost_info->costs   = costs;
+               cost_info->dfs_num = dfs_num++;
+               set_irn_link(block, cost_info);
+       }
+
+       /* sort array by block costs */
+       qsort(blocklist, n_blocks, sizeof(blocklist[0]), cmp_block_costs);
+
+       ir_reserve_resources(irg, IR_RESOURCE_BLOCK_VISITED);
+       inc_irg_block_visited(irg);
+
+       for (i = 0; i < n_blocks; ++i) {
+               ir_node       *block = blocklist[i];
+               if (Block_block_visited(block))
+                       continue;
+
+               /* continually add predecessors with highest costs to worklist
+                * (without using backedges) */
+               do {
+                       block_costs_t *info       = get_irn_link(block);
+                       ir_node       *best_pred  = NULL;
+                       float          best_costs = -1;
+                       int            n_cfgpred  = get_Block_n_cfgpreds(block);
+                       int            i;
+
+                       pdeq_putr(worklist, block);
+                       mark_Block_block_visited(block);
+                       for (i = 0; i < n_cfgpred; ++i) {
+                               ir_node       *pred_block = get_Block_cfgpred_block(block, i);
+                               block_costs_t *pred_info  = get_irn_link(pred_block);
+
+                               /* ignore backedges */
+                               if (pred_info->dfs_num > info->dfs_num)
+                                       continue;
+
+                               if (info->costs > best_costs) {
+                                       best_costs = info->costs;
+                                       best_pred  = pred_block;
+                               }
+                       }
+                       block = best_pred;
+               } while(block != NULL && !Block_block_visited(block));
+
+               /* now put all nodes in the worklist in our final order */
+               while (!pdeq_empty(worklist)) {
+                       ir_node *pblock = pdeq_getr(worklist);
+                       assert(order_p < n_blocks);
+                       order[order_p++] = pblock;
+               }
+       }
+       assert(order_p == n_blocks);
+       del_pdeq(worklist);
+
+       ir_free_resources(irg, IR_RESOURCE_BLOCK_VISITED);
+
+       DEL_ARR_F(blocklist);
+
+       obstack_free(&obst, NULL);
+       obstack_init(&obst);
+
+       block_order   = order;
+       n_block_order = n_blocks;
+}
+
 /**
  * Run the register allocator for the current register class.
  */
 static void be_straight_alloc_cls(void)
 {
+       int i;
+
        lv = be_assure_liveness(birg);
        be_liveness_assure_sets(lv);
-       be_liveness_assure_chk(lv);
 
-       ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
-       inc_irg_visited(irg);
+       ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
 
        DB((dbg, LEVEL_2, "=== Allocating registers of %s ===\n", cls->name));
 
+       be_clear_links(irg);
+
        irg_block_walk_graph(irg, NULL, analyze_block, NULL);
-       /* we need some dominance pre-order walk to ensure we see all
-        *  definitions/create copies before we encounter their users */
-       dom_tree_walk_irg(irg, allocate_coalesce_block, NULL, NULL);
+       if (create_congruence_classes)
+               combine_congruence_classes();
 
-       ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
+       for (i = 0; i < n_block_order; ++i) {
+               ir_node *block = block_order[i];
+               allocate_coalesce_block(block, NULL);
+       }
+
+       ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
 }
 
 static void dump(int mask, ir_graph *irg, const char *suffix,
@@ -1375,8 +1987,8 @@ static void be_straight_alloc(be_irg_t *new_birg)
        irg       = be_get_birg_irg(birg);
        execfreqs = birg->exec_freq;
 
-       /* TODO: extract some of the stuff from bechordal allocator, like
-        * statistics, time measurements, etc. and use them here too */
+       /* determine a good coloring order */
+       determine_block_order();
 
        for (c = 0; c < n_cls; ++c) {
                cls             = arch_env_get_reg_class(arch_env, c);
@@ -1387,8 +1999,8 @@ static void be_straight_alloc(be_irg_t *new_birg)
                stat_ev_ctx_push_str("regcls", cls->name);
 
                n_regs      = arch_register_class_n_regs(cls);
-               ignore_regs = bitset_malloc(n_regs);
-               be_put_ignore_regs(birg, cls, ignore_regs);
+               normal_regs = rbitset_malloc(n_regs);
+               be_abi_set_non_ignore_regs(birg->abi, cls, normal_regs);
 
                spill();
 
@@ -1412,8 +2024,7 @@ static void be_straight_alloc(be_irg_t *new_birg)
                 * now */
                /* TODO: test liveness_introduce */
                be_liveness_invalidate(lv);
-
-               bitset_free(ignore_regs);
+               free(normal_regs);
 
                stat_ev_ctx_pop("regcls");
        }
@@ -1442,10 +2053,12 @@ void be_init_straight_alloc(void)
        static be_ra_t be_ra_straight = {
                be_straight_alloc,
        };
-
-       FIRM_DBG_REGISTER(dbg, "firm.be.straightalloc");
+       lc_opt_entry_t *be_grp              = lc_opt_get_grp(firm_opt_get_root(), "be");
+       lc_opt_entry_t *straightalloc_group = lc_opt_get_grp(be_grp, "straightalloc");
+       lc_opt_add_table(straightalloc_group, options);
 
        be_register_allocator("straight", &be_ra_straight);
+       FIRM_DBG_REGISTER(dbg, "firm.be.straightalloc");
 }
 
 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_straight_alloc);