--- /dev/null
+/*
+ * Project: libFIRM
+ * File name: ir/opt/reassoc.c
+ * Purpose: Reassociation
+ * Author: Michael Beck
+ * Created:
+ * CVS-ID: $Id$
+ * Copyright: (c) 1998-2004 Universität Karlsruhe
+ * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+# include "irnode_t.h"
+# include "irgraph_t.h"
+# include "irmode_t.h"
+# include "iropt_t.h"
+# include "ircons_t.h"
+# include "irgmod.h"
+# include "dbginfo.h"
+# include "iropt_dbg.h"
+# include "irflag_t.h"
+# include "irgwalk.h"
+# include "reassoc_t.h"
+# include "firmstat.h"
+
+typedef struct _walker_t {
+ int changes; /* set, if a reassociation take place */
+} walker_t;
+
+typedef enum {
+ NO_CONSTANT = 0, /**< node is not constant */
+ REAL_CONSTANT = 1, /**< node is a constnt that is suitable for constant folding */
+ CONST_EXPR = 4 /**< node is not constnt expression in the current context,
+ use 4 here to simplify implementation of get_comm_Binop_ops() */
+} const_class_t;
+
+/**
+ * returns wheater a node is constant, ie is a constant or
+ * is loop invariant
+ */
+static const_class_t get_const_class(ir_node *n)
+{
+ ir_op *op = get_irn_op(n);
+
+ if (op == op_Const)
+ return REAL_CONSTANT;
+ if (op == op_SymConst)
+ return CONST_EXPR;
+
+ return NO_CONSTANT;
+}
+
+/**
+ * returns the operands of a commutative bin-op, if one operand is
+ * a constant in the current context, it is returned as the second one.
+ *
+ * Beware: Real constrants must be returned with higher priority than
+ * constnt expression, because they might be folded.
+ */
+static void get_comm_Binop_ops(ir_node *binop, ir_node **a, ir_node **c)
+{
+ ir_node *op_a = get_binop_left(binop);
+ ir_node *op_b = get_binop_right(binop);
+ int class_a = get_const_class(op_a);
+ int class_b = get_const_class(op_b);
+
+ assert(is_op_commutative(get_irn_op(binop)));
+
+ switch (class_a + 2*class_b) {
+ case REAL_CONSTANT + 2*NO_CONSTANT:
+ case REAL_CONSTANT + 2*REAL_CONSTANT:
+ case REAL_CONSTANT + 2*CONST_EXPR:
+ case CONST_EXPR + 2*NO_CONSTANT:
+ *a = op_b;
+ *c = op_a;
+ break;
+ default:
+ *a = op_a;
+ *c = op_b;
+ break;
+ }
+}
+
+/**
+ * reassociate a Sub: x - c = (-c) + x
+ */
+static int reassoc_Sub(ir_node *n)
+{
+ ir_node *right = get_Sub_right(n);
+
+ /* handles rule R6:
+ * convert x - c => (-c) + x
+ *
+ * As there is NO real Minus in Firm it makes no sense to do this
+ * for non-real constants yet.
+ * */
+ if (get_const_class(right) == REAL_CONSTANT) {
+ ir_node *block = get_nodes_block(right);
+ ir_mode *mode = get_irn_mode(right);
+ dbg_info *dbg = get_irn_dbg_info(right);
+ ir_node *irn, *c;
+
+ c = new_r_Const(current_ir_graph, block, mode, get_mode_null(mode));
+ irn = new_rd_Sub(dbg, current_ir_graph, block, c, right, mode);
+
+ irn = new_rd_Add(dbg, current_ir_graph, block, irn, get_Sub_left(n), get_irn_mode(n));
+
+ printf("Applied: %s - %s => (-%s) + %s\n",
+ get_irn_opname(get_Sub_left(n)), get_irn_opname(c),
+ get_irn_opname(c), get_irn_opname(get_Sub_left(n)) );
+
+ exchange(n, irn);
+
+ return 1;
+ }
+ return 0;
+}
+
+/** Retrieve a mode form the operands. We need this, because
+ * Add and Sub are allowed to operate on (P, Is)
+ */
+static ir_mode *get_mode_from_ops(ir_node *op1, ir_node *op2)
+{
+ ir_mode *m1, *m2;
+
+ m1 = get_irn_mode(op1);
+ if (mode_is_reference(m1))
+ return m1;
+
+ m2 = get_irn_mode(op2);
+ if (mode_is_reference(m2))
+ return m2;
+
+ assert(m1 == m2);
+
+ return m1;
+}
+
+/**
+ * reassociate a commutative Binop
+ *
+ * BEWARE: this rule leads to a potential loop, if
+ * all two operands are are constant expressions and the third is a
+ * constant, so avoid this situation.
+ */
+static int reassoc_commutative(ir_node *n)
+{
+ ir_op *op = get_irn_op(n);
+ ir_node *block = get_nodes_block(n);
+ ir_node *t1, *c1;
+
+ get_comm_Binop_ops(n, &t1, &c1);
+
+ if (get_irn_op(t1) == op) {
+ ir_node *t2, *c2;
+ const_class_t c_c1, c_c2, c_t2;
+
+ get_comm_Binop_ops(t1, &t2, &c2);
+
+ c_c1 = get_const_class(c1);
+ c_c2 = get_const_class(c2);
+ c_t2 = get_const_class(t2);
+
+ if ( ((c_c1 > NO_CONSTANT) & (c_t2 > NO_CONSTANT)) &&
+ ((((c_c1 ^ c_c2 ^ c_t2) & CONST_EXPR) == 0) || ((c_c1 & c_c2 & c_t2) == CONST_EXPR)) ) {
+ /* all three are constant and either all are constant expressions or two of them are:
+ * then, applying this rule would lead into a cycle
+ *
+ * Note that if t2 is a onstant so is c2, so we save one test.
+ */
+ return 0;
+ }
+
+ if ((c_c1 != NO_CONSTANT) & (c_c2 != NO_CONSTANT)) {
+ /* handles rules R7, R8, R9, R10:
+ * convert c1 .OP. (c2 .OP. x) => (c1 .OP. c2) .OP. x
+ */
+ ir_node *irn, *in[2];
+ ir_mode *mode;
+
+ in[0] = c1;
+ in[1] = c2;
+
+ mode = get_mode_from_ops(in[0], in[1]);
+ in[0] = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
+ in[1] = t2;
+
+ mode = get_mode_from_ops(in[0], in[1]);
+ irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
+
+ printf("Applied: %s .%s. (%s .%s. %s) => (%s .%s. %s) .%s. %s\n",
+ get_irn_opname(c1), get_irn_opname(n), get_irn_opname(c2), get_irn_opname(n), get_irn_opname(t2),
+ get_irn_opname(c1), get_irn_opname(n), get_irn_opname(c2), get_irn_opname(n), get_irn_opname(t2));
+
+ exchange(n, irn);
+
+ return 1;
+ }
+ }
+ return 0;
+}
+
+#define reassoc_Add reassoc_commutative
+
+/**
+ * reassociate using distibutive law for Mul and Add/Sub
+ */
+static int reassoc_Mul(ir_node *n)
+{
+ ir_node *add_sub, *c;
+ ir_op *op;
+
+ if (reassoc_commutative(n))
+ return 1;
+
+ get_comm_Binop_ops(n, &add_sub, &c);
+ op = get_irn_op(add_sub);
+
+ /* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
+ if (op == op_Add || op == op_Sub) {
+ ir_mode *mode = get_irn_mode(n);
+ ir_node *irn, *block, *t1, *t2, *in[2];
+
+ block = get_nodes_block(n);
+ t1 = get_binop_left(add_sub);
+ t2 = get_binop_right(add_sub);
+
+ in[0] = new_rd_Mul(NULL, current_ir_graph, block, c, t1, mode);
+ in[1] = new_rd_Mul(NULL, current_ir_graph, block, c, t2, mode);
+
+ mode = get_mode_from_ops(in[0], in[1]);
+ irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
+
+ printf("Applied: (%s .%s. %s) %s %s => (%s %s %s) .%s. (%s %s %s)\n",
+ get_irn_opname(t1), get_op_name(op), get_irn_opname(t2), get_irn_opname(n), get_irn_opname(c),
+ get_irn_opname(t1), get_irn_opname(n), get_irn_opname(c),
+ get_op_name(op),
+ get_irn_opname(t2), get_irn_opname(n), get_irn_opname(c));
+
+ exchange(n, irn);
+
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * The walker for the reassociation
+ */
+static void do_reassociation(ir_node *n, void *env)
+{
+ walker_t *wenv = env;
+ int res;
+
+ /* reassociation must run until fixpoint */
+ do {
+ ir_op *op = get_irn_op(n);
+ ir_mode *mode = get_irn_mode(n);
+
+ res = 0;
+
+ /* reassociation works only for integer or reference modes */
+ if (op->reassociate && (mode_is_int(mode) || mode_is_reference(mode))) {
+ res = op->reassociate(n);
+ if (res) {
+ wenv->changes = 1;
+
+ /* we need a skip here, or we will see an Id in the next iteration */
+ n = skip_Id(n);
+ }
+ }
+ } while (res == 1);
+}
+
+/*
+ * do the reassociation
+ */
+void optimize_reassociation(ir_graph *irg)
+{
+ walker_t env;
+
+ assert(get_irg_phase_state(irg) != phase_building);
+
+ /* reassociation needs constant folding */
+ if (!get_opt_reassociation() || !get_opt_constant_folding())
+ return;
+
+ env.changes = 0;
+
+ irg_walk_graph(irg, NULL, do_reassociation, &env);
+
+ /* now we have collected enough information, optimize */
+ irg_walk_graph(irg, NULL, do_reassociation, &env);
+
+ /* Handle graph state */
+ if (env.changes) {
+ if (get_irg_outs_state(current_ir_graph) == outs_consistent)
+ set_irg_outs_inconsistent(current_ir_graph);
+ }
+}
+
+/* initialise the reassociation by adding operations to some opcodes */
+void firm_init_reassociation(void)
+{
+#define INIT(a) op_##a->reassociate = reassoc_##a;
+ INIT(Mul);
+ INIT(Add);
+ INIT(Sub);
+#undef CASE
+}
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