From d2f2fdc28e6e5fa06aa608decf52389ac7bdd9e6 Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Mon, 10 Dec 2012 14:41:35 +0900
Subject: [PATCH] Create dummy definitions for local variables.

The entry dummy block is setup to provide dummy definitions of local
variables so the reaching definitions analysis can be used to detect
uninitialized variables (not implemented yet). Fake statement numbers
(func->num_statements + X) are used to represent the definitions. Local
variables (ie, not temp ops) use their offsets (ie, the offset range they
cover) for X. Temp ops use their flowvar number + the size of the
function's defspace for X. flow_kill_aliases() should take care of temp op
aliasing, while the use of the actual offsets spanned by the variable's def
should take care of any wild aliasing so structures and unions should
become a non-issue.
---
 tools/qfcc/source/flow.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/tools/qfcc/source/flow.c b/tools/qfcc/source/flow.c
index 7adc82d06..0ea448beb 100644
--- a/tools/qfcc/source/flow.c
+++ b/tools/qfcc/source/flow.c
@@ -46,6 +46,7 @@
 
 #include "dags.h"
 #include "def.h"
+#include "defspace.h"
 #include "diagnostic.h"
 #include "dot.h"
 #include "flow.h"
@@ -178,6 +179,8 @@ flowvar_is_global (flowvar_t *var)
 	if (var->op->op_type != op_def)
 		return 0;
 	def = var->op->o.def;
+	if (def->alias)
+		def = def->alias;
 	if (def->local)
 		return 0;
 	return 1;
@@ -191,6 +194,8 @@ flowvar_is_param (flowvar_t *var)
 	if (var->op->op_type != op_def)
 		return 0;
 	def = var->op->o.def;
+	if (def->alias)
+		def = def->alias;
 	if (!def->local)
 		return 0;
 	if (!def->param)
@@ -368,6 +373,23 @@ flow_build_vars (function_t *func)
 		if (flowvar_is_global (func->vars[i]))
 			set_add (func->global_vars, i);
 	}
+	// create dummy defs for local vars
+	for (i = 0; i < func->num_vars; i++) {
+		int         offset, size;
+		int         j;
+
+		var = func->vars[i];
+		if (flowvar_is_global (var) || flowvar_is_param (var))
+			continue;
+		if (var->op->op_type == op_temp) {
+			set_add (var->define, func->symtab->space->size + var->number);
+		} else {
+			offset = def_offset (var->op->o.def);
+			size = def_size (var->op->o.def);
+			for (j = offset; j < offset + size; j++)
+				set_add (var->define, func->num_statements + j);
+		}
+	}
 
 	set_delete (stuse);
 	set_delete (stdef);
@@ -455,6 +477,20 @@ flow_reaching_defs (flowgraph_t *graph)
 		node->reaching_defs.in = set_new ();
 		node->reaching_defs.out = set_new ();
 	}
+	// Create out for the entry dummy node using fake statement numbers.
+	kill = set_new ();
+	for (i = 0; i < graph->func->num_statements; i++)
+		set_add (kill, i);
+	out = set_new ();
+	for (i = 0; i < graph->func->num_vars; i++) {
+		var = graph->func->vars[i];
+		set_union (out, var->define);	// do not want alias handling here
+		set_difference (out, kill);		// remove any gens from the function
+	}
+	graph->nodes[graph->num_nodes]->reaching_defs.out = out;
+	graph->nodes[graph->num_nodes]->reaching_defs.in = set_new ();
+	graph->nodes[graph->num_nodes]->reaching_defs.gen = set_new ();
+	graph->nodes[graph->num_nodes]->reaching_defs.kill = set_new ();
 
 	while (changed) {
 		changed = 0;