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Loop
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Predication
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Loop
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Predication
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is
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an
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optimization
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in
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C2.
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The
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general
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idea
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is
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to
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insert
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a
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predicate
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on
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the
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entry
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path
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to
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a
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loop,
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and
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raise
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a
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uncommon
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trap
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if
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the
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check
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of
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the
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condition
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fails.
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The
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condition
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checks
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are
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promoted
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from
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inside
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the
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loop
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body,
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and
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thus
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the
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checks
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inside
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the
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loop
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could
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be
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eliminated.
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Currently,
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loop
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predication
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optimization
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has
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been
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applied
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to
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remove
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array
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range
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check,
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null
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checks
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and
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array
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checks
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in
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loops.
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Loop Predication for Array Range Check Elimination
Use loop predicate to remove array range checks in a loop.
original loop |
for (int i = init, i < limit; i += stride) |
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{ |
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// loop |
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with |
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array |
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range |
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check |
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+ |
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offset |
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< |
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a.length) |
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{ // array range check |
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] |
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... |
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|
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|
...
|
after loop predication |
|---|
if ( scale * imax + offset < a.length ) |
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{ // loop predicate |
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i < limit; i += stride) |
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{ |
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/ |
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/ loop |
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without |
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array range |
...
check |
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