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[SR-7026] Compiler runs extremely slow on this bit shifting and or-ing code #49574

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swift-ci opened this issue Feb 18, 2018 · 3 comments
Open

[SR-7026] Compiler runs extremely slow on this bit shifting and or-ing code #49574

swift-ci opened this issue Feb 18, 2018 · 3 comments
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@xedin
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself performance type checker Area → compiler: Semantic analysis

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@swift-ci
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Previous ID SR-7026
Radar rdar://problem/37680424
Original Reporter acr (JIRA User)
Type Bug
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, Performance, TypeChecker
Assignee @xedin
Priority Medium

md5: ca2cef5b3c16ece282f62eec59b2367b

Issue Description:

This code takes several minutes to compile. On my MBP i5 2.4Ghz it takes just under 3 minutes.

I've tried on both the Standard and New build system, both behave the same.

Unfortunately I don't know why. If I break it out to several lines doing each shift on a separate line or-equaling them together the compiler has no problem.

Slow code:

struct Test {
 let computed: Int
 init(a: Int, b: Int, c: Int, d: Int, e: Int = 0, f: Int = 0, g: Int = 0, h: Int = 0) {
        computed = (a << 56) | (b << 48) | (c << 40) | (d << 32) | (e << 24) | (f << 16) | (g << 8) | h
  }
}

Fast code:

struct Test {
 let computed: Int
 init(a: Int, b: Int, c: Int, d: Int, e: Int = 0, f: Int = 0, g: Int = 0, h: Int = 0){
        var value: Int = (a << 56)
        value |= (b << 48)
        value |= (c << 40)
        value |= (d << 32)
        value |= (e << 24)
        value |= (f << 16)
        value |= (g << 8)
        value |= h
        computed = value
  }
}
@belkadan
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@xedin, @rudkx, seems in line with the others.

@xedin
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xedin commented Feb 19, 2018

Yes, this is definitely a common problem we are trying to address...

@xedin
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xedin commented Feb 19, 2018

@swift-ci create

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@xedin xedin

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself performance type checker Area → compiler: Semantic analysis
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@xedin @belkadan @swift-ci