improvements,

interessing insight about scc algorithm documented

[r5295]

ir/ana/callgraph.c

@@ -1118,7 +1118,7 @@ static void compute_rec_depth (ir_graph *irg, void *env) {
 
 
 /* ----------------------------------------------------------------------------------- */
-/* Another algorithm to compute recursion nesting depth                                */
+/* Another algorithm to compute the execution freqency of methods ignoring recursions. */
 /* Walk the callgraph.  Ignore backedges.  Use sum of execution freqencies of Call     */
 /* nodes to evaluate a callgraph edge.                                                 */
 /* ----------------------------------------------------------------------------------- */

ir/ana/execution_frequency.c

@@ -20,7 +20,9 @@
 #include "pdeq.h"
 
 #include "irprog.h"
+#include "irnode_t.h"
 #include "irloop.h"
+#include "irgwalk.h"
 
 #include "interval_analysis.h"
 
@@ -32,6 +34,7 @@
 typedef struct {
   void   *reg;
   double  freq;
+  int     prob;
 } reg_exec_freq;
 
 /* We use this set for all nodes in all irgraphs. */
@@ -58,6 +61,7 @@ static INLINE void set_region_exec_freq(void *reg, double freq) {
 INLINE double get_region_exec_freq(void *reg) {
   reg_exec_freq ef, *found;
   ef.reg  = reg;
+  assert(exec_freq_set);
 
   found = set_find(exec_freq_set, &ef, sizeof(ef), exec_freq_hash(&ef));
 
@@ -79,6 +83,183 @@ double get_irn_exec_freq(ir_node *n) {
 }
 
 
+/*------------------------------------------------------------------*/
+/* A algorithm that precomputes whether Conds lead to an exception.
+ * Computes a field for all Projs from Conds that says the following:
+ *   - The Proj projs from a normal dual Cond with probability 50:50
+ *   - This Proj of the Cond leads to an exception, i.e., a raise node.
+ *     It is taken with exception probability.
+ *   - The Proj of the Cond avoids an exception.  It is taken with
+ *     1 - exception probability.                                   */
+/*------------------------------------------------------------------*/
+
+#include "irouts.h"
+
+typedef enum {
+  Cond_prob_none,
+  Cond_prob_normal,
+  Cond_prob_avoid_exception,
+  Cond_prob_exception_taken,
+  Cond_prob_was_exception_taken,
+} Cond_prob;
+
+static int just_passed_a_Raise = 0;
+static ir_node *Cond_list = NULL;
+
+/* We do not use an extra set, as Projs are not yet in the existing one. */
+void set_ProjX_probability(ir_node *n, Cond_prob prob) {
+  reg_exec_freq ef;
+  ef.reg  = n;
+  ef.prob = prob;
+  set_insert(exec_freq_set, &ef, sizeof(ef), exec_freq_hash(&ef));
+}
+
+Cond_prob get_ProjX_probability(ir_node *n) {
+  reg_exec_freq ef, *found;
+  ef.reg  = n;
+
+  found = set_find(exec_freq_set, &ef, sizeof(ef), exec_freq_hash(&ef));
+
+  if (found)
+    return (Cond_prob)found->prob;
+  else
+    return Cond_prob_none;
+}
+
+/* A walker that only visits the nodes we want to see. */
+
+static void
+my_irg_walk_2_both(ir_node *node, irg_walk_func *pre, irg_walk_func *post, void * env) {
+  int i;
+  set_irn_visited(node, current_ir_graph->visited);
+
+  pre(node, env);
+
+  if (node->op != op_Block) {
+    ir_node *pred;
+    if (node->op == op_Proj)
+      pred = get_irn_n(node, 0);
+    else
+      pred = get_irn_n(node, -1);
+    if (pred->visited < current_ir_graph->visited)
+      my_irg_walk_2_both(pred, pre, post, env);
+  }
+
+  else {  /* a Block */
+    for (i = get_irn_arity(node) - 1; i >= 0; --i) {
+      ir_node *pred = get_irn_n(node, i);
+      if (pred->visited < current_ir_graph->visited)
+	my_irg_walk_2_both(pred, pre, post, env);
+    }
+  }
+
+  if (node->op == op_End) {
+    for (i = get_irn_arity(node) - 1; i >= 0; --i) {
+      ir_node *pred = get_irn_n(node, i);
+      if ((pred->op == op_Block) && (pred->visited < current_ir_graph->visited))
+	my_irg_walk_2_both(pred, pre, post, env);
+    }
+  }
+
+  post(node, env);
+}
+static void my_irg_walk_current_graph(irg_walk_func *pre, irg_walk_func *post, void *env) {
+  inc_irg_visited(current_ir_graph);
+  my_irg_walk_2_both(get_irg_end(current_ir_graph), pre, post, env);
+}
+
+
+static void walk_pre(ir_node *n, void *env) {
+
+  if (get_irn_op(n) == op_Raise)
+    just_passed_a_Raise = 1;
+
+  if (   (get_irn_op(n) == op_Proj)
+      && (get_irn_op(get_Proj_pred(n)) == op_Cond)
+      && (just_passed_a_Raise)) {
+    ir_node *c = get_Proj_pred(n);
+
+    /* If we already visited the other Proj, and it also leads to a Raise,
+       we are in the middle of something. Continue searching. */
+    assert(get_irn_n_outs(c) == 2 && "encountered a switch cond");
+    ir_node *other_proj = get_irn_out(c, 0);
+    if (other_proj == n) other_proj = get_irn_out(c, 1);
+    if (get_ProjX_probability(other_proj) == Cond_prob_exception_taken) {
+      set_ProjX_probability(other_proj, Cond_prob_was_exception_taken);
+      /* Keep searching for the Proj, so keep just_passed_a_Raise. */
+    } else {
+      set_ProjX_probability(n, Cond_prob_exception_taken);
+      just_passed_a_Raise = 0;
+    }
+  }
+
+  if (get_irn_op(n) == op_Cond) {
+    set_irn_link(n, Cond_list);
+    Cond_list = n;
+  }
+}
+
+static void walk_post(ir_node *n, void *env) {
+
+  if (get_irn_op(n) == op_Raise)
+    just_passed_a_Raise = 0;
+
+  if (   (get_irn_op(n) == op_Proj)
+      && (get_irn_op(get_Proj_pred(n)) == op_Cond)
+      && ((get_ProjX_probability(n) == Cond_prob_exception_taken)    ||
+	  (get_ProjX_probability(n) == Cond_prob_was_exception_taken)   )) {
+    just_passed_a_Raise = 1;
+  }
+}
+
+/** Precompute which Conds test for an exception.
+ *
+ *  Operates on current_ir_graph. */
+void precompute_cond_evaluation(void) {
+  ir_node *c;
+
+  compute_outs(current_ir_graph);
+
+  just_passed_a_Raise = 0;
+  Cond_list = NULL;
+  my_irg_walk_current_graph(walk_pre, walk_post, NULL);
+
+  for (c = Cond_list; c; c = get_irn_link(c)) {
+    assert(get_irn_n_outs(c) == 2 && "encountered a switch cond");
+    ir_node *p0 = get_irn_out(c, 0);
+    ir_node *p1 = get_irn_out(c, 1);
+
+    /* both are exceptions */
+    if ((get_ProjX_probability(p0) == Cond_prob_exception_taken) &&
+	(get_ProjX_probability(p1) == Cond_prob_exception_taken)   ) {
+      assert(0 && "I tried to avoid these!");
+      /* It's a */
+      set_ProjX_probability(p0, Cond_prob_normal);
+      set_ProjX_probability(p1, Cond_prob_normal);
+    }
+
+    /* p0 is exception */
+    else if (get_ProjX_probability(p0) == Cond_prob_exception_taken) {
+      set_ProjX_probability(p1, Cond_prob_avoid_exception);
+    }
+
+    /* p1 is exception */
+    else if (get_ProjX_probability(p1) == Cond_prob_exception_taken) {
+      set_ProjX_probability(p0, Cond_prob_avoid_exception);
+    }
+
+    /* none is exception */
+    else {
+      set_ProjX_probability(p0, Cond_prob_normal);
+      set_ProjX_probability(p1, Cond_prob_normal);
+    }
+  }
+}
+
+int is_fragile_Proj(ir_node *n) {
+  return is_Proj(n) && (get_ProjX_probability(n) == Cond_prob_exception_taken);
+}
+
 /*------------------------------------------------------------------*/
 /* The algorithm to compute the execution freqencies.
  *
@@ -94,21 +275,27 @@ static INLINE int is_loop_head(ir_node *cond) {
   return false;
 }
 
+/** Weight a single region in edge.
+ *
+ *  Given all outs of the predecessor region, we can compute the weight of
+ *  this single edge. */
 static INLINE double get_weighted_region_exec_freq(void *reg, int pos) {
-  void *pred_reg = get_region_in(reg, pos);
-  double res, full_freq = get_region_exec_freq(pred_reg);
-  int n_outs     = get_region_n_outs    (pred_reg);
-  int n_exc_outs = get_region_n_exc_outs(pred_reg);
+  void *pred_reg        = get_region_in(reg, pos);
+  double res, full_freq = get_region_exec_freq (pred_reg);
+  int n_outs            = get_region_n_outs    (pred_reg);
+  int n_exc_outs        = get_region_n_exc_outs(pred_reg);
 
   ir_node *cfop;
   if (is_ir_node(reg)) {
-    cfop = skip_Proj(get_Block_cfgpred((ir_node *)reg, pos));
+    cfop = get_Block_cfgpred((ir_node *)reg, pos);
+    if (is_Proj(cfop) && (get_irn_op(get_Proj_pred(cfop)) != op_Cond))
+      cfop = skip_Proj(cfop);
   } else {
     assert(is_ir_loop(reg));
     cfop = get_loop_cfop(reg, pos);
   }
 
-  if (is_fragile_op(cfop)) {
+  if (is_fragile_op(cfop) || is_fragile_Proj(cfop)) {
     res = full_freq * exception_prob;
   } else {
 
@@ -183,6 +370,7 @@ void compute_execution_frequency(ir_graph *irg, int default_loop_weight, double
   exception_prob = exception_probability;
   if (!exec_freq_set) exec_freq_set = new_set(exec_freq_cmp, 256);
 
+  precompute_cond_evaluation();
   construct_intervals(current_ir_graph);
   compute_frequency(default_loop_weight);
 

ir/ana/execution_frequency.h

@@ -22,26 +22,41 @@
  * We assume the start block of a procedure is executed once.  Based on this we
  * compute the execution freqency of all blocks.
  *
- *
+ * The computation of the freqencies depends on the count of exception control
+ * flow computed during the interval analysis.  The interval analysis again
+ * depends on stuff computed here.
  */
 
 #include "irnode.h"
 #include "irgraph.h"
 
+/* A proj from a Cond that goes to an exception handler. */
+int is_fragile_Proj(ir_node *n);
 
 /** Returns the number of times the block/region is executed according to
- *  our estimate. */
-double get_irn_exec_freq(ir_node *n);
+ *  our estimate. Gives a number relative to the Start node of the procedure
+ *  the block is in, which is weighted with 1. */
+double get_irn_exec_freq   (ir_node *n);
 double get_Block_exec_freq (ir_node *b);
 double get_region_exec_freq(void *reg);
 
 /** Compute the execution frequency for all blocks in the given
  *  graph.
  *
- * @param irg                  The graph to be analyzed.
- * @param default_loop_weight  The default number of executions of a loop.
+ * @param irg                   The graph to be analyzed.
+ * @param default_loop_weight   The default number of executions of a loop.
+ * @param exception_probability The probability that a fragile operation causes an exception.
+ *
+ * Uses link field.
  */
 void compute_execution_frequency(ir_graph *irg, int default_loop_weight, double exception_probability);
+
+/** Compute the execution frequency for all graphs.
+ *
+ * @param default_loop_weight   The default number of executions of a loop.
+ * @param exception_probability The probability that a fragile operation causes an exception.
+ *
+ */
 void compute_execution_frequencies(int default_loop_weight, double exception_probability);
 
 /** Free occupied memory, reset. */

ir/ana/field_temperature.c

@@ -68,6 +68,7 @@ int get_irn_recursion_depth(ir_node *n) {
 }
 
 
+/**   @@@ the second version of the heuristic. */
 int get_weighted_loop_depth(ir_node *n) {
   int loop_call_depth = get_irn_loop_call_depth(n);
   int loop_depth      = get_irn_loop_depth(n);
@@ -86,12 +87,14 @@ static int default_recursion_weight = 5;
 
 /* The final evaluation of a node.  In this function we can
    adapt the heuristic.  Combine execution freqency with
-   recursion depth. */
+   recursion depth.
+   @@@ the second version of the heuristic. */
 double get_irn_final_cost(ir_node *n) {
-  double cost_loop = get_irn_exec_freq(n);
-  int    rec_depth = get_irn_recursion_depth(n);
-  double cost_rec  = pow(default_recursion_weight, rec_depth);
-  return cost_loop + cost_rec;
+  double cost_loop   = get_irn_exec_freq(n);
+  double cost_method = get_irg_method_execution_frequency(get_irn_irg(n));
+  int    rec_depth   = get_irn_recursion_depth(n);
+  double cost_rec    = pow(default_recursion_weight, rec_depth);
+  return cost_loop*(cost_method + cost_rec);
 }
 
 double get_type_estimated_n_instances(type *tp) {

ir/ana/interval_analysis.c

+
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
@@ -7,7 +8,7 @@
 #endif
 
 #include "interval_analysis.h"
-
+#include "execution_frequency.h"
 #include "firm_common_t.h"
 #include "set.h"
 #include "array.h"
@@ -71,7 +72,7 @@ int get_region_n_ins(void *region) {
 
 void *get_region_in(void *region, int pos) {
   assert(0 <= pos && pos < get_region_n_ins(region));
-  return (get_region_attr(region)->in_array)[pos];
+  return ((get_region_attr(region)->in_array)[pos]);
 }
 
 void add_region_in (void *region, void *in) {
@@ -93,7 +94,7 @@ void inc_region_n_exc_outs(void *region) {
 
 void *get_loop_cfop(void *region, int pos) {
   assert(0 <= pos && pos < get_region_n_ins(region));
-  return (get_region_attr(region)->op_array)[pos];
+  return ((get_region_attr(region)->op_array)[pos]);
 }
 
 void add_loop_cfop (void *region, void *cfop) {
@@ -102,7 +103,8 @@ void add_loop_cfop (void *region, void *cfop) {
 }
 
 static INLINE void exc_outs(void *reg, ir_node *cfop) {
-  if (is_fragile_op(cfop)) inc_region_n_exc_outs(reg);
+  if (is_fragile_op(cfop) || (is_fragile_Proj(cfop)))
+    inc_region_n_exc_outs(reg);
 }
 
 /*------------------------------------------------------------------*/
@@ -235,8 +237,16 @@ static void construct_interval_block(ir_node *b, ir_loop *l) {
       continue;
     }
 
-    cfop = skip_Proj(get_Block_cfgpred(b, i));
-    pred = get_nodes_block(cfop);
+    cfop = get_Block_cfgpred(b, i);
+    if (is_Proj(cfop)) {
+      if (get_irn_op(get_Proj_pred(cfop)) != op_Cond) {
+	cfop = skip_Proj(cfop);
+      } else {
+	assert(get_nodes_block(cfop) == get_nodes_block(skip_Proj(cfop)));
+      }
+    }
+
+    pred = skip_Proj(get_nodes_block(cfop));
     /* We want nice blocks. */
     assert(   get_irn_op(pred) != op_Bad
            && get_irn_op(skip_Proj(get_Block_cfgpred(b, i))) != op_Bad);

ir/ana/interval_analysis.h

@@ -17,13 +17,14 @@
  *
  *  @author Goetz Lindenmaier
  *
- *  The analysis is based on the control flow looptree.  An intervall are basically
- *  all nodes in a single ir_loop entry, i.e., basic blocks and inner loop nodes.
- *  The analysis computes a new set of edges that link all nodes of a loop to an
- *  acyclic graph.
- *
- *
+ *  The analysis is based on the control flow looptree.  An intervall
+ *  are basically all nodes in a single ir_loop entry, i.e., basic
+ *  blocks and inner loop nodes.  The analysis computes a new set of
+ *  edges that link all nodes of a loop to an acyclic graph.
  *
+ *  The interval analysis counts the number of exception control flow
+ *  operations leaving a block.  This depends on stuff computed in
+ *  execution_freqencies.
  */
 
 #ifndef _INTERVAL_ANALYSIS_H_
@@ -47,6 +48,11 @@ void  add_region_in   (void *region, void *in);
  *  This number is useful for evaluation of execution frequencies.
  */
 int get_region_n_outs(void *region);
+
+/** The number of exception out edges of a region.
+ *
+ *  This number is useful for evaluation of execution frequencies.
+ */
 int get_region_n_exc_outs(void *region);
 
 /** The control flow operation corresponding to the loop-region in at

ir/ana/irloop.h

@@ -126,7 +126,17 @@ void *get_loop_link (const ir_loop *loop);
 /* ------------------------------------------------------------------- */
 
 /** Constructs backedge information for irg in intraprocedural view.
- *  @returns Maximal depth of loop tree. */
+ *  @returns Maximal depth of loop tree.
+ *
+ *  ATTENTION:
+ *  One assumes, the Phi nodes in a block with a backedge have backedges
+ *  at the same positions as the block.  This is not the case, as
+ *  the scc algorithms does not respect the program semantics in this case.
+ *  Take a swap in a loop (t = i; i = j; j = t;)  This results in two Phi
+ *  nodes.  They form a cycle.  Once the scc algorithm deleted one of the
+ *  edges, the cycle is removed.  The second Phi node does not get a
+ *  backedge!
+ */
 /* @@@ Well, maybe construct_loop_information or analyze_loops ? */
 int construct_backedges(ir_graph *irg);