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cmd/compile: unnecessary bounds check #64902

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gnojus opened this issue Dec 30, 2023 · 2 comments
Closed

cmd/compile: unnecessary bounds check #64902

gnojus opened this issue Dec 30, 2023 · 2 comments
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Performance
Milestone
Unplanned

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@gnojus
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gnojus commented Dec 30, 2023

go1.21.5

package p

func f(i int) {
    var t [3]int
    if i >= 0 {
        _ = t[i%len(t)]
    }
}

https://godbolt.org/z/Tda3649sv

I would assume, since i is non negative, i % len(t) should always be in bounds? But the assembly contains a panicIndex.
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Dec 30, 2023
@Jorropo
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Jorropo commented Dec 31, 2023

I'm pretty sure this is a duplicate of #63110

@dmitshur dmitshur added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jan 9, 2024
@dmitshur dmitshur added this to the Backlog milestone Jan 9, 2024
@mknyszek mknyszek modified the milestones: Backlog, Unplanned Jan 10, 2024
@mknyszek
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Closing as a duplicate of #63110. In triage we think it's pretty close to a duplicate, anyway.

@mknyszek mknyszek closed this as not planned Won't fix, can't repro, duplicate, stale Jan 10, 2024
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Performance
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@mknyszek @dmitshur @bcmills @gopherbot @Jorropo @gnojus