From 4f70b48370a50ed58eee1f20af1aacb8666bf03b Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Mon, 10 Dec 2012 13:23:45 +0900
Subject: [PATCH] Add a function to check if two defs overlap.

Very useful for alias handling :)
---
 tools/qfcc/include/def.h |  7 +++++++
 tools/qfcc/source/def.c  | 24 ++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/tools/qfcc/include/def.h b/tools/qfcc/include/def.h
index 77a839887..774a16242 100644
--- a/tools/qfcc/include/def.h
+++ b/tools/qfcc/include/def.h
@@ -247,6 +247,13 @@ void initialize_def (struct symbol_s *sym, struct type_s *type,
 					 struct expr_s *init, struct defspace_s *space,
 					 storage_class_t storage);
 
+/** Determine if two defs overlap.
+
+	\param d1		The first def to check. May be an alias def.
+	\param d2		The second def to check. May be an alias def.
+	\return			1 if the defs overlap, 0 otherwise.
+*/
+int def_overlap (def_t *d1, def_t *d2);
 //@}
 
 #endif//__def_h
diff --git a/tools/qfcc/source/def.c b/tools/qfcc/source/def.c
index e1f164e80..82b79b9e1 100644
--- a/tools/qfcc/source/def.c
+++ b/tools/qfcc/source/def.c
@@ -587,3 +587,27 @@ initialize_def (symbol_t *sym, type_t *type, expr_t *init, defspace_t *space,
 	}
 	sym->s.def->initializer = init;
 }
+
+int
+def_overlap (def_t *d1, def_t *d2)
+{
+	int         offs1, size1;
+	int         offs2, size2;
+	/// Defs in different spaces never overlap.
+	if (d1->space != d2->space)
+		return 0;
+
+	offs1 = d1->offset;
+	if (d1->alias)
+		offs1 += d1->alias->offset;
+	size1 = type_size (d1->type);
+
+	offs2 = d2->offset;
+	if (d2->alias)
+		offs2 += d2->alias->offset;
+	size2 = type_size (d2->type);
+
+	if (offs1 < offs2 + size2 && offs2 < offs1 + size1)
+		return 1;
+	return 0;
+}