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Detect fixed loops with autotuner even if there is no assignment of const value to the loop variable before loop #1516

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merged 2 commits into from
Oct 9, 2024
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Detect fixed loops with autotuner even if there is no assignment of const value to the loop variable before loop #1516

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25a1aca
Assume var is 0 if there was no assign before loop
karoliineh Jun 20, 2024
64b3baa
Bugfix: do not assume loop start to be 0 in case of decreasing values
karoliineh Sep 27, 2024
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6 changes: 4 additions & 2 deletions src/util/loopUnrolling.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -277,8 +277,10 @@ let fixedLoopSize loopStatement func =
if getsPointedAt var func then
None
else
let* start = constBefore var loopStatement func in
let* diff = assignmentDifference (loopBody loopStatement) var in
let diff = Option.value (assignmentDifference (loopBody loopStatement) var) ~default:Z.one in
(* Assume var start value if there was no constant assignment to the var before loop;
Assume it to be 0, if loop is increasing and 11 (TODO: can we do better than just 11?) if loop is decreasing *)
let start = Option.value (constBefore var loopStatement func) ~default:(if diff < Z.zero then Z.of_int 11 else Z.zero) in
let* goal = adjustGoal diff goal op in
let iterations = loopIterations start diff goal (op=Ne) in
Logs.debug "comparison: %a" CilType.Exp.pretty comparison;
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