From e0b8877cd916dca3b37fd39e1376bf0ca0f11082 Mon Sep 17 00:00:00 2001 From: Adriaan Moors Date: Sun, 27 Nov 2011 22:57:40 +0100 Subject: [vpm] common sub-expression elimination for conditions TreeMakers (esp. CondTreeMakers) are approximated by hash-cons'ed Conds sharing is detected for prefixes of Conds, and shared conditions are only tested once their results are stored, and repeated tests branch on the last shared condition, reusing the results from the first time they were checked a Test is 1-to-1 with a TreeMaker, but may share its Cond TODO: clean separation of the two translation strategies: - naive flatMap/orElse (for virtualization) - less-naive if-then-else (with CSE etc coming) sharing trees caused wrong bytecode to be emitted (verifyerror) tentative explanation: "because lambdalift uses mutable state to track which variables have been captured if you refer to the same variable with the same tree twice it'll get confused" Sent at 8:27 PM on Thursday >> grzegorz.kossakowski: so we found a bug in jvm according to http://java.sun.com/docs/books/jvms/second_edition/html/Instructions2.doc2.html checkcast should throw a classcastexception becuase it's a shorthand for if !(x instanceof T) throw ClassCastExcpt but jvm decided to throw verifyerror and yeah, the check is wrong if jvm was not throwing verifyerror it would throw classcast exception saying that ObjectRef cannot be casted to $colon$colon ... >> me: so now where does it come from? since a ref is involved, i thought LambdaLift >> grzegorz.kossakowski: yup or now I don't think lambalift introduces that kind of low-level casts but I might be wrong btw. it's interesting that it unpacks stuff from objectref twice in your code and in one place checkcast is correct and in another is wrong Sent at 9:33 PM on Thursday >> grzegorz.kossakowski: also, since it's a verifyerror I think genjvm should have an assertion >> grzegorz.kossakowski: 193: getfield #54; //Field scala/runtime/ObjectRef.elem:Ljava/lang/Object; 196: checkcast #8; //class scala/runtime/ObjectRef 199: invokevirtual #95; //Method scala/collection/immutable/$colon$colon.tl$1:()Lscala/collection/immutable/List; it's this see you have checkcast for ObjectRef and then on that value, you try to call tl() method from List Sent at 9:56 PM on Thursday >> me: fixed sharing trees is bad very bad because lambdalift uses mutable state to track which variables have been captured if you refer to the same variable with the same tree twice it'll get confused --- test/files/run/virtpatmat_opt_sharing.check | 1 + 1 file changed, 1 insertion(+) create mode 100644 test/files/run/virtpatmat_opt_sharing.check (limited to 'test/files/run/virtpatmat_opt_sharing.check') diff --git a/test/files/run/virtpatmat_opt_sharing.check b/test/files/run/virtpatmat_opt_sharing.check new file mode 100644 index 0000000000..d00491fd7e --- /dev/null +++ b/test/files/run/virtpatmat_opt_sharing.check @@ -0,0 +1 @@ +1 -- cgit v1.2.3