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[CLJ-47] GC Issue 43: Dead code in generated bytecode Created: 17/Jun/09  Updated: 26/Aug/13

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: None
Fix Version/s: Backlog

Type: Defect Priority: Major
Reporter: Anonymous Assignee: Unassigned
Resolution: Unresolved Votes: 0
Labels: None

Approval: Vetted

 Description   
Reported by Levente.Santha, Jan 11, 2009
The bug was described in detail in this thread: http://groups.google.com/
group/clojure/browse_thread/thread/81ba15d7e9130441

For clojure.core$last__2954.invoke the correct bytecode would be (notice 
the removed "goto    65" after "41:  goto    0"):

public java.lang.Object invoke(java.lang.Object)   throws 
java.lang.Exception;
  Code:
   0:   getstatic       #22; //Field const__0:Lclojure/lang/Var;
   3:   invokevirtual   #37; //Method clojure/lang/Var.get:()Ljava/lang/
Object;
   6:   checkcast       #39; //class clojure/lang/IFn
   9:   aload_1
   10:  invokeinterface #41,  2; //InterfaceMethod clojure/lang/IFn.invoke:
(Ljava/lang/Object;)Ljava/lang/Object;
   15:  dup
   16:  ifnull  44
   19:  getstatic       #47; //Field java/lang/Boolean.FALSE:Ljava/lang/
Boolean;
   22:  if_acmpeq       45
   25:  getstatic       #22; //Field const__0:Lclojure/lang/Var;
   28:  invokevirtual   #37; //Method clojure/lang/Var.get:()Ljava/lang/
Object;
   31:  checkcast       #39; //class clojure/lang/IFn
   34:  aload_1
   35:  invokeinterface #41,  2; //InterfaceMethod clojure/lang/IFn.invoke:
(Ljava/lang/Object;)Ljava/lang/Object;
   40:  astore_1
   41:  goto    0
   44:  pop
   45:  getstatic       #26; //Field const__1:Lclojure/lang/Var;
   48:  invokevirtual   #37; //Method clojure/lang/Var.get:()Ljava/lang/
Object;
   51:  checkcast       #39; //class clojure/lang/IFn
   54:  aload_1
   55:  aconst_null
   56:  astore_1
   57:  invokeinterface #41,  2; //InterfaceMethod clojure/lang/IFn.invoke:
(Ljava/lang/Object;)Ljava/lang/Object;
   62:  areturn

Our JIT reported incorrect stack size along the basic block introduced by 
the unneeded goto.
The bug was present in SVN rev 1205.


 Comments   
Comment by Assembla Importer [ 08/Oct/10 10:21 AM ]

Converted from http://www.assembla.com/spaces/clojure/tickets/47

Comment by Assembla Importer [ 08/Oct/10 10:21 AM ]

richhickey said: Updating tickets (#8, #19, #30, #31, #126, #17, #42, #47, #50, #61, #64, #69, #71, #77, #79, #84, #87, #89, #96, #99, #103, #107, #112, #113, #114, #115, #118, #119, #121, #122, #124)

Comment by Assembla Importer [ 08/Oct/10 10:21 AM ]

aredington said: This appears to still be a problem with the generated bytecode in 1.3.0. Examining the bytecode for last, the problem has moved to invokeStatic:

<pre>
public static java.lang.Object invokeStatic(java.lang.Object) throws java.lang.Exception;
Code:
0: aload_0
1: invokestatic #50; //Method clojure/core$next.invokeStatic:(Ljava/lang/Object;)Ljava/lang/Object;
4: dup
5: ifnull 25
8: getstatic #56; //Field java/lang/Boolean.FALSE:Ljava/lang/Boolean;
11: if_acmpeq 26
14: aload_0
15: invokestatic #50; //Method clojure/core$next.invokeStatic:(Ljava/lang/Object;)Ljava/lang/Object;
18: astore_0
19: goto 0
22: goto 30
25: pop
26: aload_0
27: invokestatic #59; //Method clojure/core$first.invokeStatic:(Ljava/lang/Object;)Ljava/lang/Object;
30: areturn
</pre>

Line number 22 is an unreachable goto given the prior goto on line 19.

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