Add optimization: occult_consts

Now we have a simple optimization actually using DCA.

include/libfirm/iroptimize.h

@@ -851,6 +851,12 @@ FIRM_API ir_graph_pass_t *place_code_pass(const char *name);
  */
 FIRM_API void fixpoint_vrp(ir_graph*);
 
+/**
+ * This optimization finds values where the bits are either constant or irrelevant
+ * and exchanges them for a corresponding constant.
+ */
+FIRM_API void occult_consts(ir_graph*);
+
 /**
  * Creates an ir_graph pass for fixpoint_vrp().
  * This pass dDetermines information about the values of nodes

ir/opt/occult_const.c

+/*
+ * This file is part of libFirm.
+ * Copyright (C) 2013 University of Karlsruhe.
+ */
+
+/**
+ * @brief   optimize nodes to const, where non-const bits are irrelevant
+ * @author  Andreas Seltenreich, Andreas Zwinkau
+ */
+
+// TODO might make sense to merge this optimization with fp-vrp
+
+#include "config.h"
+
+#include "iroptimize.h"
+
+#include <stdbool.h>
+#include "debug.h"
+#include "ircons.h"
+#include "irgmod.h"
+#include "irgopt.h"
+#include "irnode_t.h"
+#include "iropt_t.h"
+#include "irdump_t.h"
+#include "iredges_t.h"
+#include "irgwalk.h"
+#include "irpass_t.h"
+#include "tv.h"
+#include "irnodemap.h"
+#include "dca.h"
+#include "fp-vrp.h"
+
+DEBUG_ONLY(static firm_dbg_module_t *dbg;)
+
+typedef struct env_t {
+	bool changed;
+	ir_nodemap dca;
+	ir_nodemap vrp;
+	struct obstack obst;
+} env_t;
+
+static void occult_const_opt_walker(ir_node *node, void *data)
+{
+	/* Ignore already const nodes */
+	if (is_Const(node) || is_SymConst(node)) return;
+
+	/* Ignore mode_BB, mode_X, etc */
+	if (!mode_is_data(get_irn_mode(node))) return;
+
+	env_t       *env = (env_t *)data;
+	vrp_bitinfo *vrp = ir_nodemap_get(vrp_bitinfo, &env->vrp, node);
+
+	if (vrp == NULL) {
+		DB((dbg, LEVEL_4, "No VRP info: %+F\n", node));
+		return;
+	}
+
+	ir_tarval *dc                       = ir_nodemap_get(ir_tarval, &env->dca, node);
+	ir_tarval *not_const_bits           = tarval_eor(vrp->o, vrp->z);
+	ir_tarval *relevant_not_const_bits  = tarval_and(dc, not_const_bits);
+	if (!tarval_is_null(relevant_not_const_bits)) {
+		DB((dbg, LEVEL_4, "Not occult: %+F dc=%T, z=%T, o=%T\n", node, dc, vrp->z, vrp->o));
+		return;
+	}
+
+	ir_graph  *irg  = get_irn_irg(node);
+	ir_node   *cnst = new_r_Const(irg, vrp->z);
+	DB((dbg, LEVEL_2, "Occult Const found: %+F -> %+F dc=%T, z=%T, o=%T\n", node, cnst, dc, vrp->z, vrp->o));
+	exchange(node, cnst);
+	env->changed = true;
+}
+
+static void fill_nodemap(ir_node *node, void *data) {
+	ir_nodemap *map = data;
+	ir_nodemap_insert_fast(map, node, get_irn_link(node));
+}
+
+void occult_consts(ir_graph *irg)
+{
+	FIRM_DBG_REGISTER(dbg, "firm.opt.occults");
+
+	assure_irg_properties(irg,
+		IR_GRAPH_PROPERTY_NO_BADS
+		| IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE
+		| IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
+		| IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES);
+
+	env_t env;
+	obstack_init(&env.obst);
+
+	env.changed = false;
+
+	fp_vrp_analyze(irg, &env.obst);
+	ir_nodemap_init(&env.vrp, irg);
+	irg_walk_graph(irg, fill_nodemap, 0, &env.vrp);
+
+	dca_analyze(irg);
+	ir_nodemap_init(&env.dca, irg);
+	irg_walk_graph(irg, fill_nodemap, 0, &env.dca);
+
+	irg_walk_graph(irg, occult_const_opt_walker, 0, &env);
+
+	ir_nodemap_destroy(&env.dca);
+	ir_nodemap_destroy(&env.vrp);
+
+	obstack_free(&env.obst, NULL);
+	confirm_irg_properties(irg,
+			env.changed ? IR_GRAPH_PROPERTIES_NONE : IR_GRAPH_PROPERTIES_ALL);
+}