[Mono-bugs] [Bug 82756][Nor] New - useless instructions generated for struct field init

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Changed by lupus at ximian.com.

http://bugzilla.ximian.com/show_bug.cgi?id=82756

--- shadow/82756	2007-09-08 13:55:16.000000000 -0400
+++ shadow/82756.tmp.18142	2007-09-08 13:55:16.000000000 -0400
@@ -0,0 +1,54 @@
+Bug#: 82756
+Product: Mono: Compilers
+Version: 1.2
+OS: 
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Normal
+Component: C#
+AssignedTo: rharinath at novell.com                            
+ReportedBy: lupus at ximian.com               
+QAContact: mono-bugs at ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: useless instructions generated for struct field init
+
+mcs generate useless code when initing a struct in a field, either instance
+or static. Basically, given the struct D, for a D field initialized with:
+
+  d_field = new D ();
+
+It will emit the code:
+
+  d_field = new D ()
+  d_field =  d_field;
+
+This just inflates the IL code for no reason and pessimizes the code a lot,
+especially for instance fields (because it loads the this object reference
+across method calls...).
+
+A simple test program follows, check with monodis the presence of the
+useless instructions.
+
+struct D {
+
+	readonly static D d1 = new D (1);
+	static D d2 = new D (2);
+
+	int val;
+
+	public D (int v) {
+		val = v;
+	}
+	static void Main () {
+		D d = new D (5);
+		T t = new T ();
+	}
+}
+
+class T {
+	D d = new D (3);
+}