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[SR-10518] Integer overflow checks prevent loop unrolling #52918

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TellowKrinkle opened this issue Apr 19, 2019 · 2 comments
Closed

[SR-10518] Integer overflow checks prevent loop unrolling #52918

TellowKrinkle opened this issue Apr 19, 2019 · 2 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself performance

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@TellowKrinkle
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Previous ID SR-10518
Radar rdar://problem/50054299
Original Reporter @TellowKrinkle
Type Bug
Status Resolved
Resolution Won't Do
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, Performance
Assignee None
Priority Medium

md5: 5ab0700095dc228277ef2731e36eac67

Issue Description:

When compiling loops like an array sum, the presence of overflow checks causes the compiler to not unroll loops as shown here

More info here
@belkadan
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cc @bob-wilson

@eeckstein
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The important optimization is mainly vectorization (and not loop unrolling) as discussed here: https://forums.swift.org/t/loop-unrolling-optimization/23344

We will not add vectorization for overflow checks in the SIL optimizer.
The way to solve this is to use non-overflow-checking operators, like discussed in the forum thread.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself performance
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@belkadan @TellowKrinkle @eeckstein