[Soot-list] baf locals packer question

[mbatch at cs.mcgill.ca]

For potential future questions, I thought I would follow up on the bug I
discovered (in my code) that was resulting in incorrect local packing in
the baf phase (bb.lp).

The original email is below, but the general problem was that I was
sometimes inserting new baf instructions at the beginning of the method
(such as local initializers - "push, store"). While these did NOT
interfere with the ParameterRef locals, it would appear that problems can
occur in the local packer if ParameterRef baf units are NOT the VERY FIRST
units in the method.

Cheers,

Michael

On Thu, July 6, 2006 6:51 pm, mbatch at cs.mcgill.ca wrote:
> Hello all,
>
> I have a Baf transform with moves bytecode around in a method. Sometimes
> this results in the java verifier not being able to properly tell if a
> register is initialized before use. To solve this in the most
> conservative way, I run a guaranteed defs analysis and anywhere a local is
> used but not defined I add an initializer at the top of the method for
> that local (i.e. r1 = null). This is done BEFORE localpacking. This worked
> in the past, but most recently I am getting unusual results. Since
> something was odd, I went ahead and added initializers for EVERY local at
> the top of methods.
>
> The local packer is "unsplitting" most of these locals such that they
> share the same name (register) even though they clearly have overlapping
> live ranges.
>
> The following is an example. As you can see, z6, $z5, and $r30 are all
> assigned $r20, even though they are boolean, boolean, and objectref
> respectively, and clearly overlap. Anyone have any ideas on this one?
>
>
> Before Local packing:
>
>
> 0 push null 1 store.r r2
> 2 push null
> 3 store.r r37
> 4 push null
> 5 store.r r39
> 6 push -1750717778
> 7 store.b $z7
> 8 push null
> 9 store.r $r41
> 10 push 1165249391
> 11 store.b z6
> 12 push 164612758
> 13 store.b $z5
> 14 push null
> 15 store.r r31
> 16 push null
> 17 store.r $r30
> 18 push null
> 19 store.r r27
> 20 push null
> 21 store.r $r26
> 22 push null
> 23 store.r r4
> 24 push null
> 25 store.r r5
> 26 push 1663228139
> 27 store.b $z3
> 28 push null
> 29 store.r $r20
> 30 push -472838325
> 31 store.b z2
> 32 push -2058237879
> 33 store.b $z1
> 34 push null
> 35 store.r r12
> 36 push null
> 37 store.r $r11
> 38 push null
> 39 store.r r3
> 40 push null
> 41 store.r $r8
>
>
>
> After Local Packing:
>
>
> 0 push null 1 store.r r2
> 2 push null
> 3 store.r z2
> 4 push null
> 5 store.r r5
> 6 push -1750717778
> 7 store.b $r20
> 8 push null
> 9 store.r r3
> 10 push 1165249391
> 11 store.b $r20
> 12 push 164612758
> 13 store.b $r20
> 14 push null
> 15 store.r z2
> 16 push null
> 17 store.r $r20
> 18 push null
> 19 store.r z2
> 20 push null
> 21 store.r $r20
> 22 push null
> 23 store.r r3
> 24 push null
> 25 store.r r5
> 26 push 1663228139
> 27 store.b z2
> 28 push null
> 29 store.r $r20
> 30 push -472838325
> 31 store.b z2
> 32 push -2058237879
> 33 store.b r5
> 34 push null
> 35 store.r r3
> 36 push null
> 37 store.r r5
> 38 push null
> 39 store.r r3
> 40 push null
> 41 store.r r5	0 push null:q
> 1 store.r r2
> 2 push null
> 3 store.r r37
> 4 push null
> 5 store.r r39
> 6 push -1750717778
> 7 store.b $z7
> 8 push null
> 9 store.r $r41
> 10 push 1165249391
> 11 store.b z6
> 12 push 164612758
> 13 store.b $z5
> 14 push null
> 15 store.r r31
> 16 push null
> 17 store.r $r30
> 18 push null
> 19 store.r r27
> 20 push null
> 21 store.r $r26
> 22 push null
> 23 store.r r4
> 24 push null
> 25 store.r r5
> 26 push 1663228139
> 27 store.b $z3
> 28 push null
> 29 store.r $r20
> 30 push -472838325
> 31 store.b z2
> 32 push -2058237879
> 33 store.b $z1
> 34 push null
> 35 store.r r12
> 36 push null
> 37 store.r $r11
> 38 push null
> 39 store.r r3
> 40 push null
> 41 store.r $r8