X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fopt%2Fopt_osr.c;h=101fb54c3f21210487d59b31ef6c2a9db82de842;hb=d16d39df6772995a29ecdc8de1904ccb2e523599;hp=d73974654f9e23afad7673bea3aadf436f509148;hpb=7e961375c8b2f276d3aa2ab908fdd0012008251a;p=libfirm

diff --git a/ir/opt/opt_osr.c b/ir/opt/opt_osr.c
index d73974654..101fb54c3 100644
--- a/ir/opt/opt_osr.c
+++ b/ir/opt/opt_osr.c
@@ -1,7 +1,7 @@
 /**
  * Project:     libFIRM
- * File name:   ir/opt/opt_osr.
- * Purpose:     Operator Strength Reduction,
+ * File name:   ir/opt/opt_osr.c
+ * Purpose:     Operator Strength Reduction, based on
  *              Keith D. Cooper, L. Taylor Simpson, Christopher A. Vick
  * Author:      Michael Beck
  * Modified by:
@@ -14,38 +14,33 @@
 #include "config.h"
 #endif
 
-#ifdef HAVE_MALLOC_H
-#include <malloc.h>
-#endif
-#ifdef HAVE_ALLOCA_H
-#include <alloca.h>
-#endif
-
 #include "opt_osr.h"
 #include "irgraph.h"
+#include "ircons.h"
 #include "irop_t.h"
 #include "irloop.h"
 #include "irdom.h"
+#include "irgmod.h"
 #include "irflag_t.h"
 #include "irgwalk.h"
+#include "irouts.h"
 #include "debug.h"
 #include "obst.h"
+#include "set.h"
+#include "tv.h"
+#include "hashptr.h"
 #include "irtools.h"
+#include "irloop_t.h"
 #include "array.h"
+#include "firmstat.h"
+#include "xmalloc.h"
 
 /** The debug handle. */
 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
 
-/* Use the link field to mark IV's */
-#define MARK_LOOP_IV(loop)   set_loop_link((loop), (loop))
-#define UNMARK_LOOP_IV(loop) set_loop_link((loop), NULL)
-#define IS_LOOP_IV(loop)     (get_loop_link(loop) != NULL)
-
 /** A scc. */
 typedef struct scc {
 	ir_node *head;		/**< the head of the list */
-	ir_node *header;	/**< the header block of this scc */
-	int     is_iv;      /**< true, if this scc is an IV */
 } scc;
 
 /** A node entry */
@@ -61,54 +56,370 @@ typedef struct node_entry {
 
 /** The environment. */
 typedef struct iv_env {
-	node_entry *entries;   /**< the node entry array */
-	struct obstack obst;   /**< an obstack for allocations */
-	ir_node  **stack;      /**< the node stack */
-	int      tos;          /**< tos index */
-	unsigned nextDFSnum;   /**< the current DFS number */
-	unsigned replaced;     /**< number of replaced ops */
-	unsigned POnum;        /**< current post order number */
+	struct obstack obst;    /**< an obstack for allocations */
+	ir_node  **stack;       /**< the node stack */
+	int      tos;           /**< tos index */
+	unsigned nextDFSnum;    /**< the current DFS number */
+	unsigned POnum;         /**< current post order number */
+	set      *quad_map;     /**< a map from (op, iv, rc) to node */
+	set      *lftr_edges;   /**< the set of lftr edges */
+	unsigned replaced;      /**< number of replaced ops */
+	unsigned lftr_replaced; /**< number of applied linear function test replacements */
+	unsigned flags;         /**< additional flags */
+	/** Function called to process a SCC. */
+	void (*process_scc)(scc *pscc, struct iv_env *env);
 } iv_env;
 
 /**
- * Check if irn is an IV.
+ * An entry in the (op, node, node) -> node map.
+ */
+typedef struct quadruple_t {
+	ir_opcode code;  /**< the opcode of the reduced operation */
+	ir_node   *op1;  /**< the first operand the reduced operation */
+	ir_node   *op2;  /**< the second operand of the reduced operation */
+
+	ir_node   *res; /**< the reduced operation */
+} quadruple_t;
+
+/**
+ * A LFTR edge.
+ */
+typedef struct LFTR_edge {
+	ir_node   *src;   /**< the source node */
+	ir_node   *dst;   /**< the destination node */
+	ir_opcode code;   /**< the opcode that must be applied */
+	ir_node   *rc;    /**< the region const that must be applied */
+} LFTR_edge;
+
+/* forward */
+static ir_node *reduce(ir_node *orig, ir_node *iv, ir_node *rc, iv_env *env);
+
+/**
+ * Compare two LFTR edges.
+ */
+static int LFTR_cmp(const void *e1, const void *e2, size_t size) {
+	const LFTR_edge *l1 = e1;
+	const LFTR_edge *l2 = e2;
+
+	return l1->src != l2->src;
+}
+
+#if 0
+/**
+ * Find a LFTR edge.
  */
-static scc *is_iv(ir_node *irn, iv_env *env) {
-	int idx = get_irn_idx(irn);
-	node_entry *e = &env->entries[idx];
+static LFTR_edge *LFTR_find(ir_node *src, iv_env *env) {
+	LFTR_edge key;
 
-	return e->pscc && e->pscc->is_iv ? e->pscc : NULL;
+	key.src  = src;
+
+	return set_find(env->lftr_edges, &key, sizeof(key), HASH_PTR(src));
+}
+#endif
+
+/**
+ * Add a LFTR edge.
+ */
+static void LFTR_add(ir_node *src, ir_node *dst, ir_opcode code, ir_node *rc, iv_env *env) {
+	LFTR_edge key;
+
+	key.src  = src;
+	key.dst  = dst;
+	key.code = code;
+	key.rc   = rc;
+
+	/*
+	 * There might be more than one edge here. This is rather bad
+	 * because we currently store only one.
+	 */
+//	assert(LFTR_find(src, env) == NULL);
+	set_insert(env->lftr_edges, &key, sizeof(key), HASH_PTR(src));
+}
+
+/**
+ * Gets the node_entry of a node
+ */
+static node_entry *get_irn_ne(ir_node *irn, iv_env *env) {
+	node_entry *e = get_irn_link(irn);
+
+	if (! e) {
+		e = obstack_alloc(&env->obst, sizeof(*e));
+		memset(e, 0, sizeof(*e));
+		set_irn_link(irn, e);
+	}
+	return e;
+}
+
+/**
+ * Check if irn is an IV.
+ *
+ * @param irn  the node to check
+ * @param env  the environment
+ *
+ * @returns the header if it is one, NULL else
+ */
+static ir_node *is_iv(ir_node *irn, iv_env *env) {
+	return get_irn_ne(irn, env)->header;
 }
 
 /**
  * Check if irn is a region constant.
+ * The block or irn must strictly dominate the header block.
+ *
+ * @param irn           the node to check
+ * @param header_block  the header block of the induction variable
  */
 static int is_rc(ir_node *irn, ir_node *header_block) {
 	ir_node *block = get_nodes_block(irn);
 
-	return block_dominates(block, header_block);
+	return (block != header_block) && block_dominates(block, header_block);
+}
+
+/**
+ * Set compare function for the quad set.
+ */
+static int quad_cmp(const void *e1, const void *e2, size_t size) {
+	const quadruple_t *c1 = e1;
+	const quadruple_t *c2 = e2;
+
+	return c1->code != c2->code || c1->op1 != c2->op1 || c1->op2 != c2->op2;
+}
+
+/**
+ * Check if an reduced operation was already calculated.
+ *
+ * @param code  the opcode of the operation
+ * @param op1   the first operand of the operation
+ * @param op2   the second operand of the operation
+ * @param env   the environment
+ *
+ * @return the already reduced node or NULL if this operation is not yet reduced
+ */
+static ir_node *search(ir_opcode code, ir_node *op1, ir_node *op2, iv_env *env) {
+	quadruple_t key, *entry;
+
+	key.code = code;
+	key.op1 = op1;
+	key.op2 = op2;
+
+	entry = set_find(env->quad_map, &key, sizeof(key),
+	                 (code * 9) ^ HASH_PTR(op1) ^HASH_PTR(op2));
+	if (entry)
+		return entry->res;
+	return NULL;
+}
+
+/**
+ * Add an reduced operation.
+ *
+ * @param code    the opcode of the operation
+ * @param op1     the first operand of the operation
+ * @param op2     the second operand of the operation
+ * @param result  the result of the reduced operation
+ * @param env     the environment
+ */
+static void add(ir_opcode code, ir_node *op1, ir_node *op2, ir_node *result, iv_env *env) {
+	quadruple_t key;
+
+	key.code = code;
+	key.op1  = op1;
+	key.op2  = op2;
+	key.res  = result;
+
+	set_insert(env->quad_map, &key, sizeof(key),
+	           (code * 9) ^ HASH_PTR(op1) ^HASH_PTR(op2));
+}
+
+/**
+ * Find a location where to place a bin-op whose operands are in
+ * block1 and block2.
+ *
+ * @param block1  the block of the first operand
+ * @param block2  the block of the second operand
+ *
+ * Note that we know here that such a place must exists. Moreover, this means
+ * that either block1 dominates block2 or vice versa. So, just return
+ * the "smaller" one.
+ */
+static ir_node *find_location(ir_node *block1, ir_node *block2) {
+	if (block_dominates(block1, block2))
+		return block2;
+	assert(block_dominates(block2, block1));
+	return block1;
 }
 
 /**
- * Do the replacement operation.
+ * Create a node that executes an op1 code op1 operation.
+ *
+ * @param code   the opcode to execute
+ * @param db     debug info to add to the new node
+ * @param op1    the first operand
+ * @param op2    the second operand
+ * @param mode   the mode of the new operation
+ *
+ * @return the newly created node
+ */
+static ir_node *do_apply(ir_opcode code, dbg_info *db, ir_node *op1, ir_node *op2, ir_mode *mode) {
+	ir_graph *irg = current_ir_graph;
+	ir_node *result;
+	ir_node *block = find_location(get_nodes_block(op1), get_nodes_block(op2));
+
+	switch (code) {
+	case iro_Mul:
+		result = new_rd_Mul(db, irg, block, op1, op2, mode);
+		break;
+	case iro_Add:
+		result = new_rd_Add(db, irg, block, op1, op2, mode);
+		break;
+	case iro_Sub:
+		result = new_rd_Sub(db, irg, block, op1, op2, mode);
+		break;
+	default:
+		assert(0);
+		result = NULL;
+	}
+	return result;
+}
+
+/**
+ * The Apply operation.
+ *
+ * @param orig   the node that represent the original operation and determines
+ *               the opcode, debug-info and mode of a newly created one
+ * @param op1    the first operand
+ * @param op2    the second operand
+ * @param env    the environment
+ *
+ * @return the newly created node
+ */
+static ir_node *apply(ir_node *orig, ir_node *op1, ir_node *op2, iv_env *env) {
+	ir_opcode code = get_irn_opcode(orig);
+	ir_node *result = search(code, op1, op2, env);
+
+	if (! result) {
+		dbg_info *db = get_irn_dbg_info(orig);
+		ir_node *op1_header = get_irn_ne(op1, env)->header;
+		ir_node *op2_header = get_irn_ne(op2, env)->header;
+
+		if (op1_header != NULL && is_rc(op2, op1_header)) {
+			result = reduce(orig, op1, op2, env);
+		}
+		else if (op2_header != NULL && is_rc(op1, op2_header)) {
+			result = reduce(orig, op2, op1, env);
+		}
+		else {
+			result = do_apply(code, db, op1, op2, get_irn_mode(orig));
+			get_irn_ne(result, env)->header = NULL;		}
+	}
+	return result;
+}
+
+/**
+ * The Reduce operation.
+ *
+ * @param orig   the node that represent the original operation and determines
+ *               the opcode, debug-info and mode of a newly created one
+ * @param iv     the induction variable
+ * @param rc     the region constant
+ * @param env    the environment
+ *
+ * @return the reduced node
+ */
+static ir_node *reduce(ir_node *orig, ir_node *iv, ir_node *rc, iv_env *env) {
+	ir_opcode code = get_irn_opcode(orig);
+	ir_node *result = search(code, iv, rc, env);
+
+	if (! result) {
+		node_entry *e, *iv_e;
+		int i, n;
+		ir_mode *mode = get_irn_mode(orig);
+
+		result = exact_copy(iv);
+
+		/* Beware: we must always create a new nduction variable with the same mode
+		   as the node we are replacing. Espicially this means the mode might be changed
+		   from P to I and back. This is always possible, because we have only Phi, Add
+		   and Sub nodes. */
+		set_irn_mode(result, mode);
+		add(code, iv, rc, result, env);
+		DB((dbg, LEVEL_3, "   Created new %+F for %+F (%s %+F)\n", result, iv,
+			get_irn_opname(orig), rc));
+
+		iv_e = get_irn_ne(iv, env);
+		e    = get_irn_ne(result, env);
+		e->header = iv_e->header;
+
+		/* create the LFTR edge */
+		LFTR_add(iv, result, code, rc, env);
+
+		n = get_irn_arity(result);
+		for (i = 0; i < n; ++i) {
+			ir_node *o = get_irn_n(result, i);
+
+			e = get_irn_ne(o, env);
+			if (e->header == iv_e->header)
+				o = reduce(orig, o, rc, env);
+			else if (is_Phi(result))
+				o = apply(orig, o, rc, env);
+			else {
+				if (code == iro_Mul)
+					o = apply(orig, o, rc, env);
+			}
+			set_irn_n(result, i, o);
+		}
+	}
+	else {
+		DB((dbg, LEVEL_3, "   Already Created %+F for %+F (%s %+F)\n", result, iv,
+			get_irn_opname(orig), rc));
+	}
+	return result;
+}
+
+/**
+ * The Replace operation.
  *
  * @param irn   the node that will be replaced
  * @param iv    the induction variable
  * @param rc    the region constant
  * @param env   the environment
  */
-static void replace(ir_node *irn, ir_node *iv, ir_node *rc, iv_env *env) {
-	DB((dbg, LEVEL_2, "  Replacing %+F\n", irn));
+static int replace(ir_node *irn, ir_node *iv, ir_node *rc, iv_env *env) {
+	ir_node *result;
+	ir_loop *iv_loop  = get_irn_loop(get_nodes_block(iv));
+	ir_loop *irn_loop = get_irn_loop(get_nodes_block(irn));
+
+	/* only replace nodes that are in the same (or deeper loops) */
+	if (get_loop_depth(irn_loop) >= get_loop_depth(iv_loop)) {
+		DB((dbg, LEVEL_2, "  Replacing %+F\n", irn));
+
+		result = reduce(irn, iv, rc, env);
+		if (result != irn) {
+			node_entry *e, *iv_e;
+
+			hook_strength_red(current_ir_graph, irn);
+			exchange(irn, result);
+			e = get_irn_ne(result, env);
+			iv_e = get_irn_ne(iv, env);
+			e->header = iv_e->header;
+		}
+		return 1;
+	}
+	return 0;
 }
 
 /**
- * check if a node can be replaced
+ * Check if a node can be replaced (+, -, *).
+ *
+ * @param irn   the node to check
+ * @param env   the environment
+ *
+ * @return non-zero if irn should be Replace'd
  */
-static void check_replace(ir_node *irn, iv_env *env) {
-	ir_node *left, *right, *iv, *rc;
-	ir_op   *op  = get_irn_op(irn);
-	opcode  code = get_op_code(op);
-	scc     *liv, *riv;
+static int check_replace(ir_node *irn, iv_env *env) {
+	ir_node   *left, *right, *iv, *rc;
+	ir_op     *op  = get_irn_op(irn);
+	ir_opcode code = get_op_code(op);
+	ir_node   *liv, *riv;
 
 	switch (code) {
 	case iro_Mul:
@@ -121,29 +432,50 @@ static void check_replace(ir_node *irn, iv_env *env) {
 
 		liv = is_iv(left, env);
 		riv = is_iv(right, env);
-		if (liv && is_rc(right, liv->header)) {
+		if (liv && is_rc(right, liv)) {
 			iv = left; rc = right;
 		}
-		else if (is_op_commutative(op) &&
-			riv && is_rc(left, riv->header)) {
+		else if (riv && is_op_commutative(op) &&
+			            is_rc(left, riv)) {
 			iv = right; rc = left;
 		}
 
 		if (iv) {
-			replace(irn, iv, rc, env);
-			++env->replaced;
+			if (code == iro_Mul && env->flags & osr_flag_ignore_x86_shift) {
+				if (is_Const(rc)) {
+					tarval *tv = get_Const_tarval(rc);
+
+					if (tarval_is_long(tv)) {
+						long value = get_tarval_long(tv);
+
+						if (value == 2 || value == 4 || value == 8) {
+							/* do not reduce multiplications by 2, 4, 8 */
+							break;
+						}
+					}
+				}
+			}
+
+			return replace(irn, iv, rc, env);
 		}
 		break;
+	default:
+		break;
 	}
+	return 0;
 }
 
 /**
- * check which SCC's are induction variables
+ * Check which SCC's are induction variables.
+ *
+ * @param pscc  a SCC
+ * @param env   the environment
  */
 static void classify_iv(scc *pscc, iv_env *env) {
 	ir_node *irn, *next, *header = NULL;
-	node_entry *h, *b;
-	int j;
+	node_entry *b, *h = NULL;
+	int j, only_phi, num_outside;
+	ir_node *out_rc;
 
 	/* find the header block for this scc */
 	for (irn = pscc->head; irn; irn = next) {
@@ -151,7 +483,7 @@ static void classify_iv(scc *pscc, iv_env *env) {
 		ir_node *block = get_nodes_block(irn);
 
 		next = e->next;
-		b = &env->entries[get_irn_idx(block)];
+		b = get_irn_ne(block, env);
 
 		if (header) {
 			if (h->POnum < b->POnum) {
@@ -164,19 +496,24 @@ static void classify_iv(scc *pscc, iv_env *env) {
 			h      = b;
 		}
 	}
-	pscc->header = header;
 
+	/* check if this scc contains only Phi, Add or Sub nodes */
+	only_phi    = 1;
+	num_outside = 0;
+	out_rc      = NULL;
 	for (irn = pscc->head; irn; irn = next) {
-		node_entry *e = get_irn_link(irn);
+		node_entry *e = get_irn_ne(irn, env);
 
 		next = e->next;
 		switch (get_irn_opcode(irn)) {
 		case iro_Add:
 		case iro_Sub:
+			only_phi = 0;
+			/* fall through */
 		case iro_Phi:
 			for (j = get_irn_arity(irn) - 1; j >= 0; --j) {
-				ir_node *pred = get_irn_n(irn, j);
-				node_entry *pe = &env->entries[get_irn_idx(pred)];
+				ir_node *pred  = get_irn_n(irn, j);
+				node_entry *pe = get_irn_ne(pred, env);
 
 				if (pe->pscc != e->pscc) {
 					/* not in the same SCC, must be a region const */
@@ -184,6 +521,12 @@ static void classify_iv(scc *pscc, iv_env *env) {
 						/* not an induction variable */
 						goto fail;
 					}
+					if (! out_rc) {
+						out_rc = pred;
+						++num_outside;
+					} else if (out_rc != pred) {
+						++num_outside;
+					}
 				}
 			}
 			break;
@@ -193,128 +536,193 @@ static void classify_iv(scc *pscc, iv_env *env) {
 		}
 	}
 	/* found an induction variable */
-	DB((dbg, LEVEL_2, "  Found an induction variable in %+F\n", pscc->head));
-	pscc->is_iv = 1;
+	DB((dbg, LEVEL_2, "  Found an induction variable:\n  "));
+	if (only_phi && num_outside == 1) {
+		/* a phi cycle with only one real predecessor can be collapsed */
+		DB((dbg, LEVEL_2, "  Found an USELESS Phi cycle:\n  "));
+
+		for (irn = pscc->head; irn; irn = next) {
+			node_entry *e = get_irn_ne(irn, env);
+			next = e->next;
+			e->header = NULL;
+			exchange(irn, out_rc);
+		}
+		++env->replaced;
+		return;
+	}
+
+	/* set the header for every node in this scc */
+	for (irn = pscc->head; irn; irn = next) {
+		node_entry *e = get_irn_ne(irn, env);
+		e->header = header;
+		next = e->next;
+		DB((dbg, LEVEL_2, " %+F,", irn));
+	}
+	DB((dbg, LEVEL_2, "\n"));
 	return;
 
 fail:
 	for (irn = pscc->head; irn; irn = next) {
-		node_entry *e = get_irn_link(irn);
+		node_entry *e = get_irn_ne(irn, env);
 
 		next = e->next;
-		check_replace(irn, env);
+		if (! check_replace(irn, env))
+			e->header = NULL;
 	}
 }
 
 /**
- * Do the replacement: We must do this as an additional step because
- * of our loop-tree structure.
+ * Process a SCC for the operator strength reduction.
+ *
+ * @param pscc  the SCC
+ * @param env   the environment
  */
-static void find_replacement(ir_loop *loop, iv_env *env) {
-	int i, n;
+static void process_scc(scc *pscc, iv_env *env) {
+	ir_node *head = pscc->head;
+	node_entry *e = get_irn_link(head);
 
-	if (! IS_LOOP_IV(loop)) {
-		/* do replacements */
-		n = get_loop_n_nodes(loop);
-		for (i = 0; i < n; ++i) {
-			ir_node *irn = get_loop_node(loop, i);
-			ir_node *left, *right, *iv, *rc;
-			opcode code = get_irn_opcode(irn);
+#ifdef DEBUG_libfirm
+	{
+		ir_node *irn, *next;
+
+		DB((dbg, LEVEL_4, " SCC at %p:\n ", pscc));
+		for (irn = pscc->head; irn; irn = next) {
+			node_entry *e = get_irn_link(irn);
 
-			switch (code) {
-			case iro_Mul:
-			case iro_Add:
-			case iro_Sub:
-				iv = rc = NULL;
+			next = e->next;
 
-				left  = get_binop_left(irn);
-				right = get_binop_right(irn);
+			DB((dbg, LEVEL_4, " %+F,", irn));
+		}
+		DB((dbg, LEVEL_4, "\n"));
+	}
+#endif
 
-				if (is_iv(left, env) && is_rc(right, left)) {
-					iv = left; rc = right;
-				}
-				else if (code != iro_Sub &&
-					is_iv(right, env) && is_rc(left, right)) {
-					iv = right; rc = left;
-				}
+	if (e->next == NULL) {
+		/* this SCC has only a single member */
+		check_replace(head, env);
+	} else {
+		classify_iv(pscc, env);
+	}
+}
+
+/**
+ * If an SCC is a Phi only cycle, remove it.
+ */
+static void remove_phi_cycle(scc *pscc, iv_env *env) {
+	ir_node *irn, *next;
+	int j;
+	ir_node *out_rc;
+
+	/* check if this scc contains only Phi, Add or Sub nodes */
+	out_rc      = NULL;
+	for (irn = pscc->head; irn; irn = next) {
+		node_entry *e = get_irn_ne(irn, env);
 
-				if (iv) {
-					replace(irn, iv, rc, env);
-					++env->replaced;
+		next = e->next;
+		if (! is_Phi(irn))
+			return;
+
+		for (j = get_irn_arity(irn) - 1; j >= 0; --j) {
+			ir_node *pred  = get_irn_n(irn, j);
+			node_entry *pe = get_irn_ne(pred, env);
+
+			if (pe->pscc != e->pscc) {
+				/* not in the same SCC, must be the only input */
+				if (! out_rc) {
+					out_rc = pred;
+				} else if (out_rc != pred) {
+					return;
 				}
-				break;
 			}
 		}
 	}
-	n = get_loop_n_sons(loop);
-	for (i = 0; i < n; ++i) {
-		ir_loop *child = get_loop_son(loop, i);
-		find_replacement(child, env);
+	/* found a Phi cycle */
+	DB((dbg, LEVEL_2, "  Found an USELESS Phi cycle:\n  "));
+
+	for (irn = pscc->head; irn; irn = next) {
+		node_entry *e = get_irn_ne(irn, env);
+		next = e->next;
+		e->header = NULL;
+		exchange(irn, out_rc);
 	}
+	++env->replaced;
 }
 
 /**
- * Process a SCC given as a list.
+ * Process a SCC for the Phi cycle removement.
+ *
+ * @param pscc  the SCC
+ * @param env   the environment
  */
-static void process_scc(scc *pscc, iv_env *env) {
+static void process_phi_only_scc(scc *pscc, iv_env *env) {
 	ir_node *head = pscc->head;
 	node_entry *e = get_irn_link(head);
 
-	pscc->is_iv = 0;
-
 #ifdef DEBUG_libfirm
 	{
 		ir_node *irn, *next;
 
-		DB((dbg, LEVEL_3, " SCC at %p:\n ", pscc));
+		DB((dbg, LEVEL_4, " SCC at %p:\n ", pscc));
 		for (irn = pscc->head; irn; irn = next) {
 			node_entry *e = get_irn_link(irn);
 
 			next = e->next;
 
-			DB((dbg, LEVEL_3, " %+F,", irn));
+			DB((dbg, LEVEL_4, " %+F,", irn));
 		}
-		DB((dbg, LEVEL_3, "\n"));
+		DB((dbg, LEVEL_4, "\n"));
 	}
 #endif
 
-	if (e->next == NULL) {
-		/* this SCC has only a single member */
-		check_replace(head, env);
-	}
-	else {
-		classify_iv(pscc, env);
-	}
+	if (e->next != NULL)
+		remove_phi_cycle(pscc, env);
 }
 
+
 /**
  * Push a node onto the stack.
+ *
+ * @param env   the environment
+ * @param n     the node to push
  */
 static void push(iv_env *env, ir_node *n) {
+	node_entry *e;
+
 	if (env->tos == ARR_LEN(env->stack)) {
 		int nlen = ARR_LEN(env->stack) * 2;
 		ARR_RESIZE(ir_node *, env->stack, nlen);
 	}
 	env->stack[env->tos++] = n;
-	env->entries[get_irn_idx(n)].in_stack = 1;
+	e = get_irn_ne(n, env);
+	e->in_stack = 1;
 }
 
 /**
  * pop a node from the stack
  *
+ * @param env   the environment
+ *
  * @return  The topmost node
  */
 static ir_node *pop(iv_env *env)
 {
-  ir_node *n = env->stack[--env->tos];
-  env->entries[get_irn_idx(n)].in_stack = 0;
-  return n;
+	ir_node *n = env->stack[--env->tos];
+	node_entry *e = get_irn_ne(n, env);
+
+	e->in_stack = 0;
+	return n;
 }
 
+/**
+ * Do Tarjan's SCC algorithm and drive OSR.
+ *
+ * @param irn  start at this node
+ * @param env  the environment
+ */
 static void dfs(ir_node *irn, iv_env *env)
 {
 	int i, n;
-	node_entry *node = &env->entries[get_irn_idx(irn)];
+	node_entry *node = get_irn_ne(irn, env);
 
 	mark_irn_visited(irn);
 
@@ -342,7 +750,7 @@ static void dfs(ir_node *irn, iv_env *env)
 		n = get_irn_arity(irn);
 		for (i = 0; i < n; ++i) {
 			ir_node *pred = get_irn_n(irn, i);
-			node_entry *o = &env->entries[get_irn_idx(pred)];
+			node_entry *o = get_irn_ne(pred, env);
 
 			if (irn_not_visited(pred)) {
 				dfs(pred, env);
@@ -360,22 +768,22 @@ static void dfs(ir_node *irn, iv_env *env)
 				node_entry *e;
 
 				x = pop(env);
-				e = &env->entries[get_irn_idx(x)];
+				e = get_irn_ne(x, env);
 				e->pscc    = pscc;
 				e->next    = pscc->head;
 				pscc->head = x;
-
-				/* link the node entry for easier access */
-				set_irn_link(x, e);
 			} while (x != irn);
 
-			process_scc(pscc, env);
+			env->process_scc(pscc, env);
 		}
 	}
 }
 
 /**
- * Do the DFS by starting end the End node
+ * Do the DFS by starting at the End node of a graph.
+ *
+ * @param irg  the graph to process
+ * @param env  the environment
  */
 static void do_dfs(ir_graph *irg, iv_env *env) {
 	ir_graph *rem = current_ir_graph;
@@ -396,6 +804,7 @@ static void do_dfs(ir_graph *irg, iv_env *env) {
 		if (irn_not_visited(ka))
 			dfs(ka, env);
 	}
+
 	current_ir_graph = rem;
 }
 
@@ -404,48 +813,307 @@ static void do_dfs(ir_graph *irg, iv_env *env) {
  */
 static void assign_po(ir_node *block, void *ctx) {
 	iv_env *env = ctx;
-	int idx = get_irn_idx(block);
+	node_entry *e = get_irn_ne(block, env);
 
-	env->entries[idx].POnum = env->POnum++;
+	e->POnum = env->POnum++;
+}
+
+#if 0
+/**
+ * Follows the LFTR edges and return the last node in the chain.
+ *
+ * @param irn  the node that should be followed
+ * @param env  the IV environment
+ *
+ * @note
+ * In the current implementation only the last edge is stored, so
+ * only one chain exists. That's why we might miss some opportunities.
+ */
+static ir_node *followEdges(ir_node *irn, iv_env *env) {
+	for (;;) {
+		LFTR_edge *e = LFTR_find(irn, env);
+		if (e)
+			irn = e->dst;
+		else
+			return irn;
+	}
+}
+
+/**
+ * Apply one LFTR edge operation.
+ * Return NULL if the transformation cannot be done safely without
+ * an Overflow.
+ *
+ * @param rc   the IV node that should be translated
+ * @param e    the LFTR edge
+ * @param env  the IV environment
+ *
+ * @return the translated region constant or NULL
+ *         if the translation was not possible
+ *
+ * @note
+ * In the current implementation only the last edge is stored, so
+ * only one chain exists. That's why we might miss some opportunities.
+ */
+static ir_node *applyOneEdge(ir_node *rc, LFTR_edge *e, iv_env *env) {
+	if (env->flags & osr_flag_lftr_with_ov_check) {
+		tarval *tv_l, *tv_r, *tv;
+		tarval_int_overflow_mode_t ovmode;
+
+		/* overflow can only be decided for Consts */
+		if (! is_Const(e->rc)) {
+			DB((dbg, LEVEL_4, " = UNKNOWN (%+F)", e->rc));
+			return NULL;
+		}
+
+		tv_l = get_Const_tarval(rc);
+		tv_r = get_Const_tarval(e->rc);
+
+		ovmode = tarval_get_integer_overflow_mode();
+		tarval_set_integer_overflow_mode(TV_OVERFLOW_BAD);
+
+		switch (e->code) {
+		case iro_Mul:
+			tv = tarval_mul(tv_l, tv_r);
+			DB((dbg, LEVEL_4, " * %+F", tv_r));
+			break;
+		case iro_Add:
+			tv = tarval_add(tv_l, tv_r);
+			DB((dbg, LEVEL_4, " + %+F", tv_r));
+			break;
+		case iro_Sub:
+			tv = tarval_sub(tv_l, tv_r);
+			DB((dbg, LEVEL_4, " - %+F", tv_r));
+			break;
+		default:
+			assert(0);
+			tv = tarval_bad;
+		}
+		tarval_set_integer_overflow_mode(ovmode);
+
+		if (tv == tarval_bad) {
+			DB((dbg, LEVEL_4, " = OVERFLOW"));
+			return NULL;
+		}
+		return new_r_Const(current_ir_graph, get_irn_n(rc, -1), get_tarval_mode(tv), tv);
+	}
+	return do_apply(e->code, NULL, rc, e->rc, get_irn_mode(rc));
+}
+
+/**
+ * Applies the operations represented by the LFTR edges to a
+ * region constant and returns the value.
+ * Return NULL if the transformation cannot be done safely without
+ * an Overflow.
+ *
+ * @param iv   the IV node that starts the LFTR edge chain
+ * @param rc   the region constant that should be translated
+ * @param env  the IV environment
+ *
+ * @return the translated region constant or NULL
+ *         if the translation was not possible
+ */
+static ir_node *applyEdges(ir_node *iv, ir_node *rc, iv_env *env) {
+	ir_node *irn = iv;
+
+	if (env->flags & osr_flag_lftr_with_ov_check) {
+		/* overflow can only be decided for Consts */
+		if (! is_Const(rc)) {
+			DB((dbg, LEVEL_4, " = UNKNOWN (%+F)\n", rc));
+			return NULL;
+		}
+		DB((dbg, LEVEL_4, "%+F", get_Const_tarval(rc)));
+	}
+
+	for (irn = iv; rc;) {
+		LFTR_edge *e = LFTR_find(irn, env);
+		if (e) {
+			rc = applyOneEdge(rc, e, env);
+			irn = e->dst;
+		}
+		else
+			break;
+	}
+	DB((dbg, LEVEL_3, "\n"));
+	return rc;
+}
+
+/**
+ * Walker, finds Cmp(iv, rc) or Cmp(rc, iv)
+ * and tries to optimize them.
+ */
+static void do_lftr(ir_node *cmp, void *ctx) {
+	iv_env *env = ctx;
+	ir_node *left, *right, *liv, *riv;
+	ir_node *iv, *rc;
+	ir_node *nleft = NULL, *nright = NULL;
+
+	if (get_irn_op(cmp) != op_Cmp)
+		return;
+
+	left  = get_Cmp_left(cmp);
+	right = get_Cmp_right(cmp);
+
+	liv = is_iv(left, env);
+	riv = is_iv(right, env);
+	if (liv && is_rc(right, liv)) {
+		iv = left; rc = right;
+
+		nright = applyEdges(iv, rc, env);
+		if (nright && nright != rc) {
+			nleft = followEdges(iv, env);
+		}
+	}
+	else if (riv && is_rc(left, riv)) {
+		iv = right; rc = left;
+
+		nleft = applyEdges(iv, rc, env);
+		if (nleft && nleft != rc) {
+			nright = followEdges(iv, env);
+		}
+	}
+
+	if (nleft && nright) {
+		DB((dbg, LEVEL_2, "  LFTR for %+F\n", cmp));
+		set_Cmp_left(cmp, nleft);
+		set_Cmp_right(cmp, nright);
+		++env->lftr_replaced;
+	}
+}
+
+/**
+ * do linear function test replacement.
+ *
+ * @param irg   the graph that should be optimized
+ * @param env   the IV environment
+ */
+static void lftr(ir_graph *irg, iv_env *env) {
+	irg_walk_graph(irg, NULL, do_lftr, env);
+}
+#endif
+
+/**
+ * Pre-walker: set all node links to NULL and fix the
+ * block of Proj nodes.
+ */
+static void clear_and_fix(ir_node *irn, void *env)
+{
+	set_irn_link(irn, NULL);
+
+	if (is_Proj(irn)) {
+		ir_node *pred = get_Proj_pred(irn);
+		set_irn_n(irn, -1, get_irn_n(pred, -1));
+	}
 }
 
 /* Performs Operator Strength Reduction for the passed graph. */
-void opt_osr(ir_graph *irg) {
-	iv_env env;
+void opt_osr(ir_graph *irg, unsigned flags) {
+	iv_env   env;
+	ir_graph *rem;
 
-	if (! get_opt_strength_red())
+	if (! get_opt_strength_red()) {
+		/* only kill Phi cycles  */
+		remove_phi_cycles(irg);
 		return;
+	}
+
+	rem = current_ir_graph;
+	current_ir_graph = irg;
 
 	FIRM_DBG_REGISTER(dbg, "firm.opt.osr");
-	firm_dbg_set_mask(dbg, SET_LEVEL_2);
 
-	/* and dominance as well */
+	DB((dbg, LEVEL_1, "Doing Operator Strength Reduction for %+F\n", irg));
+
+	obstack_init(&env.obst);
+	env.stack         = NEW_ARR_F(ir_node *, 128);
+	env.tos           = 0;
+	env.nextDFSnum    = 0;
+	env.POnum         = 0;
+	env.quad_map      = new_set(quad_cmp, 64);
+	env.lftr_edges    = new_set(LFTR_cmp, 64);
+	env.replaced      = 0;
+	env.lftr_replaced = 0;
+	env.flags         = flags;
+	env.process_scc   = process_scc;
+
+	/* Clear all links and move Proj nodes into the
+	   the same block as it's predecessors.
+	   This can improve the placement of new nodes.
+	 */
+	irg_walk_graph(irg, NULL, clear_and_fix, NULL);
+
+	/* we need dominance */
 	assure_doms(irg);
+	assure_irg_outs(irg);
 
-	DB((dbg, LEVEL_1, "Doing Operator Strength Reduction for %+F\n", irg));
+	/* calculate the post order number for blocks. */
+	irg_out_block_walk(get_irg_start_block(irg), NULL, assign_po, &env);
 
-	env.entries    = NEW_ARR_F(node_entry, get_irg_last_idx(irg));
-	memset(env.entries, 0, get_irg_last_idx(irg));
+	/* calculate the SCC's and drive OSR. */
+	do_dfs(irg, &env);
 
-	obstack_init(&env.obst);
-	env.stack      = NEW_ARR_F(ir_node *, 128);
-	env.tos        = 0;
-	env.nextDFSnum = 0;
-	env.replaced   = 0;
-	env.POnum      = 0;
+	if (env.replaced) {
+		/* try linear function test replacements */
+		//lftr(irg, &env);
 
-	/* calculate the post order number */
-	irg_block_walk_graph(irg, NULL, assign_po, &env);
+		set_irg_outs_inconsistent(irg);
+		DB((dbg, LEVEL_1, "Replacements: %u + %u (lftr)\n\n", env.replaced, env.lftr_replaced));
+	}
+
+	del_set(env.lftr_edges);
+	del_set(env.quad_map);
+	DEL_ARR_F(env.stack);
+	obstack_free(&env.obst, NULL);
+
+	current_ir_graph = rem;
+}
 
+/* Remove any Phi cycles with only one real input. */
+void remove_phi_cycles(ir_graph *irg) {
+	iv_env   env;
+	ir_graph *rem;
+
+	rem = current_ir_graph;
+	current_ir_graph = irg;
+
+	FIRM_DBG_REGISTER(dbg, "firm.opt.remove_phi");
+
+	DB((dbg, LEVEL_1, "Doing Phi cycle removement for %+F\n", irg));
+
+	obstack_init(&env.obst);
+	env.stack         = NEW_ARR_F(ir_node *, 128);
+	env.tos           = 0;
+	env.nextDFSnum    = 0;
+	env.POnum         = 0;
+	env.quad_map      = NULL;
+	env.lftr_edges    = NULL;
+	env.replaced      = 0;
+	env.lftr_replaced = 0;
+	env.flags         = 0;
+	env.process_scc   = process_phi_only_scc;
+
+	/* Clear all links and move Proj nodes into the
+	   the same block as it's predecessors.
+	   This can improve the placement of new nodes.
+	 */
+	irg_walk_graph(irg, NULL, clear_and_fix, NULL);
+
+	/* we need dominance */
+	assure_irg_outs(irg);
+
+	/* calculate the post order number for blocks. */
+	irg_out_block_walk(get_irg_start_block(irg), NULL, assign_po, &env);
+
+	/* calculate the SCC's and drive OSR. */
 	do_dfs(irg, &env);
 
 	if (env.replaced) {
 		set_irg_outs_inconsistent(irg);
-		set_irg_loopinfo_inconsistent(irg);
+                DB((dbg, LEVEL_1, "remove_phi_cycles: %u Cycles removed\n\n", env.replaced));
 	}
-	DB((dbg, LEVEL_1, "Replacements: %u\n\n", env.replaced));
 
 	DEL_ARR_F(env.stack);
 	obstack_free(&env.obst, NULL);
-	DEL_ARR_F(env.entries);
+
+	current_ir_graph = rem;
 }