Collect information on statements that set or use vars.

First, it turns out using daglabels wasn't such a workable plan (due to
labels being flushed every sblock). Instead, flowvars are used. Each actual
variable (whether normal or temp) has a pointer to the flowvar attached to
that variable.

For each variable, the statements that use or define the variable are
recorded in the appropriate set attached to each (flow)variable.

tools/qfcc/include/dags.h

@@ -45,7 +45,6 @@ typedef struct daglabel_s {
 	const char *opcode;			///< not if op
 	struct operand_s *op;		///< not if opcode;
 	struct dagnode_s *dagnode;	///< node with which this label is associated
-	int         number;			///< number of variable in func's ref list
 } daglabel_t;
 
 typedef struct dagnode_s {

tools/qfcc/include/flow.h

@@ -38,6 +38,14 @@
 struct function_s;
 struct sblock_s;
 struct statement_s;
+struct operand_s;
+
+typedef struct flowvar_s {
+	struct flowvar_s *next;		///< for ALLOC
+	struct set_s *use;			///< set of statements that use this var
+	struct set_s *define;		///< set of statements that define this var
+	int         number;			///< number of variable in func's ref list
+} flowvar_t;
 
 typedef struct flowloop_s {
 	struct flowloop_s *next;
@@ -74,6 +82,7 @@ typedef struct flowgraph_s {
 	flowloop_t *loops;			//< linked list of natural loops
 } flowgraph_t;
 
+flowvar_t *flow_get_var (struct operand_s *op);
 int flow_is_cond (struct statement_s *s);
 int flow_is_goto (struct statement_s *s);
 int flow_is_jumpb (struct statement_s *s);

tools/qfcc/include/function.h

@@ -86,7 +86,7 @@ typedef struct function_s {
 		This permits ready mapping of (function specific) variable number to
 		variable in the flow analyzer.
 	*/
-	struct daglabel_s **vars;
+	struct flowvar_s  **vars;
 	int                 num_vars;	///< total number of variables referenced
 	struct statement_s **statements;
 	int                 num_statements;

tools/qfcc/include/statements.h

@@ -43,6 +43,7 @@ typedef enum {
 
 typedef struct {
 	struct def_s   *def;
+	struct flowvar_s *flowvar;
 	struct daglabel_s *daglabel;
 } tempop_t;
 

tools/qfcc/include/symtab.h

@@ -64,6 +64,7 @@ typedef struct symbol_s {
 	sy_type_e   sy_type;		///< symbol type (st_type)
 	struct type_s *type;		///< type of object to which symbol refers
 	struct param_s *params;		///< the parameters if a function
+	struct flowvar_s *flowvar;
 	struct daglabel_s *daglabel;///< dag label for this symbol
 	union {
 		int         offset;			///< st_var (in a struct/union)

tools/qfcc/source/dags.c

@@ -43,7 +43,9 @@
 
 #include "dags.h"
 #include "diagnostic.h"
+#include "flow.h"
 #include "qfcc.h"
+#include "set.h"
 #include "statements.h"
 #include "strpool.h"
 #include "symtab.h"
@@ -134,6 +136,8 @@ operand_label (operand_t *op)
 		o = o->o.alias;
 
 	if (o->op_type == op_temp) {
+		if (o->o.tempop.daglabel)
+			return sym->daglabel;
 		label = new_label ();
 		label->op = op;
 		o->o.tempop.daglabel = label;
@@ -319,9 +323,18 @@ make_dag (const sblock_t *block)
 		operand_t  *x = 0, *y = 0, *z = 0, *w = 0;
 		dagnode_t  *n = 0, *ny, *nz, *nw;
 		daglabel_t *op, *lx;
+		flowvar_t  *var;
 		int         simp;
 
 		simp = find_operands (s, &x, &y, &z, &w);
+		if (x && (var = flow_get_var (x)))
+			set_add (var->define, s->number);
+		if (y && (var = flow_get_var (y)))
+			set_add (var->use, s->number);
+		if (z && (var = flow_get_var (z)))
+			set_add (var->use, s->number);
+		if (w && (var = flow_get_var (w)))
+			set_add (var->use, s->number);
 		if (!(ny = node (y))) {
 			ny = leaf_node (y);
 			if (simp) {

tools/qfcc/source/flow.c

@@ -52,10 +52,21 @@
 #include "symtab.h"
 #include "type.h"
 
+static flowvar_t *free_vars;
 static flowloop_t *free_loops;
 static flownode_t *free_nodes;
 static flowgraph_t *free_graphs;
 
+static flowvar_t *
+new_flowvar (void)
+{
+	flowvar_t *var;
+	ALLOC (256, flowvar_t, vars, var);
+	var->use = set_new ();
+	var->define = set_new ();
+	return var;
+}
+
 static flowloop_t *
 new_loop (void)
 {
@@ -124,24 +135,28 @@ delete_graph (flowgraph_t *graph)
 	free_graphs = graph;
 }
 
-static int
-is_variable (daglabel_t *var)
+flowvar_t *
+flow_get_var (operand_t *op)
 {
 	operand_t  *o;
 
-	if (!var)
+	if (!op)
 		return 0;
 
-	o = var->op;
+	o = op;
 	while (o->op_type == op_alias)
 		o = o->o.alias;
 
-	if (o->op_type == op_temp)
-		return 1;
-	if (o->op_type != op_symbol)
-		return 0;
-	if (o->o.symbol->sy_type == sy_var)
-		return 1;
+	if (o->op_type == op_temp) {
+		if (!o->o.tempop.flowvar)
+			o->o.tempop.flowvar = new_flowvar ();
+		return o->o.tempop.flowvar;
+	}
+	if (o->op_type == op_symbol && o->o.symbol->sy_type == sy_var) {
+		if (!o->o.symbol->flowvar)
+			o->o.symbol->flowvar = new_flowvar ();
+		return o->o.symbol->flowvar;
+	}
 	//FIXME functions? (some are variable)
 	return 0;
 }
@@ -149,19 +164,25 @@ is_variable (daglabel_t *var)
 static int
 count_operand (operand_t *op)
 {
-	daglabel_t *var;
+	flowvar_t  *var;
 
 	if (!op)
 		return 0;
 	if (op->op_type == op_label)
 		return 0;
 
-	var = operand_label (op);
+	var = flow_get_var (op);
 	// daglabels are initialized with number == 0, and any global daglabel
 	// used by a function will always have a number >= 0 after flow analysis,
 	// and local daglabels will always be 0 before flow analysis, so use -1
 	// to indicate the variable has been counted.
-	if (is_variable (var) && var->number != -1) {
+	//
+	// Also, since this is the beginning of flow analysis for this function,
+	// ensure the define/use sets for global vars are empty. However, as
+	// checking if a var is global is too much trouble, just clear them all.
+	if (var && var->number != -1) {
+		set_empty (var->use);
+		set_empty (var->define);
 		var->number = -1;
 		return 1;
 	}
@@ -171,17 +192,17 @@ count_operand (operand_t *op)
 static void
 add_operand (function_t *func, operand_t *op)
 {
-	daglabel_t *var;
+	flowvar_t  *var;
 
 	if (!op)
 		return;
 	if (op->op_type == op_label)
 		return;
 
-	var = operand_label (op);
+	var = flow_get_var (op);
 	// If the daglabel number is still -1, then the daglabel has not yet been
 	// added to the list of variables referenced by the function.
-	if (is_variable (var) && var->number == -1) {
+	if (var && var->number == -1) {
 		var->number = func->num_vars++;
 		func->vars[var->number] = var;
 	}

tools/qfcc/source/function.c

@@ -645,16 +645,6 @@ emit_function (function_t *f, expr_t *e)
 	f->sblock = make_statements (e);
 	flow_build_vars (f);
 	f->graph = flow_build_graph (f->sblock);
-	if (options.block_dot.flow)
-		print_flowgraph (f->graph, nva ("%s.%s.%s.dot", GETSTR (pr.source_file),
-										f->name, "flow"));
-	{
-		flowloop_t *l;
-		int         n = 0;
-		for (l = f->graph->loops; l; l = l->next)
-			n++;
-		printf ("%s %d %d %d\n", f->name, f->graph->num_nodes, f->num_vars, n);
-	}
 	emit_statements (f->sblock);
 }