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Remove restriction that no loop unrolling is done when breaks are in the loop #1518

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Remove restriction that no loop unrolling is done when breaks are in the loop #1518

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6f833d3
Remove restriction that no loop unrolling is done when breaks are in …
karoliineh Jun 19, 2024
e656cc1
Remove unused checkNoBreak visitors
karoliineh Jun 19, 2024
fa0f086
Merge branch 'master' into loop-unroll-ignore-breaks
karoliineh Oct 10, 2024
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17 changes: 4 additions & 13 deletions src/util/loopUnrolling.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -31,34 +31,25 @@ class checkNoBreakVisitor = object

end

let checkNoBreakStmt stmt =
let visitor = new checkNoBreakVisitor in
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checkNoBreakVisitor itself is also unused now.

ignore @@ visitCilStmt visitor stmt

let checkNoBreakBlock block =
let visitor = new checkNoBreakVisitor in
ignore @@ visitCilBlock visitor block

class findBreakVisitor(compOption: exp option ref) = object
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Looking at this visitor now, I understand why it didn't want multiple breaks. It's main goal is to actually find the comparison for the loop, which will be an if with a break inside.
By only allowing one such break it guaranteed that the result is unambiguous: there couldn't be multiple such comparisons found.

Now, if there are multiple matching ifs with breaks inside, this will still find the first one because compOption is only assigned when it's None, so that can happen at most once.
Is the loop condition always in the first matching one though? If so, then why did the old version have a problem at all? Or maybe there are loops where the condition isn't actually the first one?

inherit nopCilVisitor

method! vstmt stmt =
match stmt.skind with
| Block _ -> DoChildren
| Break _ -> raise WrongOrMultiple
| Break _ -> SkipChildren
| If (cond, t, e, _, _) -> (
checkNoBreakBlock t;
match e.bstmts with
| [s] -> (
match s.skind with
| Break _ -> (
match !compOption with
| Some _ -> raise WrongOrMultiple (*more than one loop break*)
| Some _ -> SkipChildren (*more than one loop break*)
| _ -> compOption := Some cond; SkipChildren
)
| _ -> checkNoBreakStmt stmt; SkipChildren
| _ -> SkipChildren
)
| _ -> checkNoBreakStmt stmt; SkipChildren
| _ -> SkipChildren
)
| _ -> SkipChildren

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