[LLVMdev] Little bug in LoopInfo after Rotate?

[Julio]

Well, I was too fast to frame LoopInfo. The problem could be in LoopRotation
as well. What do you think?

2008/7/13 Julio <julio.martin.hidalgo at gmail.com>:

> Hello, I have two for loops (one inside the other), that after indvars,
> looprotate, etc. (the important here is the loop rotate), is similar to this
> (I've stripped the real operations):
>
> define i32 @f() nounwind  {
> entry:
>     br label %bb1
>
> bb1:        ; preds = %bb3, %bb1, %entry
>     %i.0.reg2mem.0.ph = phi i32 [ 0, %entry ], [ %i.0.reg2mem.0.ph, %bb1
> ], [ %indvar.next9, %bb3 ]        ; <i32> [#uses=4]
>     %j.0.reg2mem.0 = phi i32 [ 0, %entry ], [ %indvar.next, %bb1 ], [ 0,
> %bb3 ]        ; <i32> [#uses=3]
>     %indvar.next = add i32 %j.0.reg2mem.0, 1        ; <i32> [#uses=2]
>     %exitcond = icmp eq i32 %indvar.next, 16        ; <i1> [#uses=1]
>     br i1 %exitcond, label %bb3, label %bb1
>
> bb3:        ; preds = %bb1
>     %indvar.next9 = add i32 %i.0.reg2mem.0.ph, 1        ; <i32> [#uses=2]
>     %exitcond10 = icmp eq i32 %indvar.next9, 32        ; <i1> [#uses=1]
>     br i1 %exitcond10, label %bb6, label %bb1
>
> bb6:        ; preds = %bb3
>     ret i32 0
> }
>
> LoopInfo says: Loop Containing:  %bb1, %bb3. Only detects the outer loop
>
> By the way, if I separate the header of the outer loop, like:
>
> define i32 @f() nounwind  {
> entry:
>     br label %bb0
>
> bb0:        ; preds = %entry, %bb3
>     %i.0.reg2mem.0.ph = phi i32 [ 0, %entry ], [ %indvar.next9, %bb3 ]
>     ; <i32> [#uses=4]
>     br label %bb1
>
> bb1:        ; preds = %bb1, %bb0
>     %j.0.reg2mem.0 = phi i32 [ 0, %bb0 ], [ %indvar.next, %bb1 ]        ;
> <i32> [#uses=3]
>     %indvar.next = add i32 %j.0.reg2mem.0, 1        ; <i32> [#uses=2]
>     %exitcond = icmp eq i32 %indvar.next, 16        ; <i1> [#uses=1]
>     br i1 %exitcond, label %bb3, label %bb1
>
> bb3:        ; preds = %bb1
>     %indvar.next9 = add i32 %i.0.reg2mem.0.ph, 1        ; <i32> [#uses=2]
>     %exitcond10 = icmp eq i32 %indvar.next9, 32        ; <i1> [#uses=1]
>     br i1 %exitcond10, label %bb6, label %bb0
>
> bb6:        ; preds = %bb3
>     ret i32 0
> }
>
> LoopInfo:
> Loop Containing:  %bb0, %bb3, %bb1
>     Loop Containing:  %bb1
>
> I would need to operate in the two loops in rotated form. It can be
> considered a bug or I have to introduce manually the header (or modify
> myself the ConsiderForLoop to my particular problem)?
>
> Thanks.
> Julio
>
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