[SR-5968] Build never ends if SWIFT_OPTIMIZATION_LEVEL is `-O` or `-Owholemodule` in Xcode 9

[swift-ci]

Previous ID	SR-5968
Radar	rdar://problem/34602036
Original Reporter	kishikawakatsumi (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

Xcode Version 9.0 (9A235)
macOS Sierra 10.12.6

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, OptimizedOnly
Assignee	@swiftix
Priority	Medium

md5: cdbcbf00f74d364d30452e27a6b6a353

Issue Description:

Summary

Build never ends if SWIFT_OPTIMIZATION_LEVEL is `-O` or `-Owholemodule` in Xcode 9.
CPU usage of swift process reaches 100%.

Steps to Reproduce:

1. Create a new Swift project.

2. Set `SWIFT_OPTIMIZATION_LEVEL = -O` in build setting or select Release build configuration in schema

3. Add a new file and paste the following code

4. Build

public class A {
    public class func f() {
        B.f()
    }
}

class B {
    private class C {
        var this: C? = nil

        lazy var number: Int = {
            var local: C? = self
            let count = 0
            while let temp = local?.this {
                local = temp
            }
            return count
        }()

        func f() -> C {
            if number == 0 {
                return self
            }
            print(number)
            return self
        }
    }

    class func f() {
        let _ = C().f()
    }
}

Expected Results:

Build finishes

Actual Results:

Build never ends, swift process CPU usage reaches 100%

[belkadan]

Whatever it is, it seems to be fixed on master. shajrawi (JIRA User), does this look familiar?

[swift-ci]

Comment by Joe Shajrawi (JIRA)

I am not familiar with it but it is not fixed on master. at least on my machine. Clean top of tree build spends forever in SimplifyCFG.

[swift-ci]

Comment by Joe Shajrawi (JIRA)

@swift-ci create

[swift-ci]

Comment by Joe Shajrawi (JIRA)

Instruments:

2.83 min 100.0% 0 s swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*)
2.83 min 100.0% 0 s performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*)
2.83 min 100.0% 0 s swift::runSILOptimizationPasses(swift::SILModule&)
2.83 min 100.0% 0 s swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&)
2.83 min 100.0% 0 s swift::SILPassManager::runOneIteration()
2.83 min 100.0% 0 s swift::SILPassManager::runFunctionPasses(llvm::ArrayRef<swift::SILFunctionTransform*>)
2.83 min 100.0% 0 s swift::SILPassManager::runPassOnFunction(swift::SILFunctionTransform*, swift::SILFunction*)
2.83 min 100.0% 0 s (anonymous namespace)::SimplifyCFGPass::run()
2.83 min 100.0% 0 s (anonymous namespace)::SimplifyCFG::run()
2.83 min 100.0% 0 s (anonymous namespace)::SimplifyCFG::simplifyBlocks()
2.83 min 100.0% 0 s (anonymous namespace)::SimplifyCFG::simplifyArgs(swift::SILBasicBlock*)
2.83 min 100.0% 0 s removeArgument(swift::SILBasicBlock*, unsigned int)
2.75 min 97.1% 34.86 s swift::SILBuilder::addOpenedArchetypeOperands(swift::SILInstruction*)

[swiftix]

I fixed it on swift/master in commit 7f4c4f7

[swiftix]

Fix committed on swift/master and swift-4.0-branch.

[sjavora]

@swiftix Sorry if this is not the way/place to ask this, but when is this fix going to propagate into Xcode? Our project is currently experiencing this and Xcode 9.1 beta 2 seems to behave in the same way as Xcode 9.0.