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[SR-12179] Windows, compiling w/o speculative devirtualization produces unstable binaries #3270

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lxbndr opened this issue Feb 11, 2020 · 4 comments
Closed

[SR-12179] Windows, compiling w/o speculative devirtualization produces unstable binaries #3270

lxbndr opened this issue Feb 11, 2020 · 4 comments
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@compnerd
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bug Compiler Foundation Windows

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@lxbndr
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lxbndr commented Feb 11, 2020

Previous ID SR-12179
Radar rdar://problem/59496026
Original Reporter @lxbndr
Type Bug
Status Closed
Resolution Done

Attachment: Download

Environment

Apple Swift version 5.2-dev (LLVM 88d1013b2e, Swift 7177f4a730)
Target: x86_64-unknown-windows-msvc

Additional Detail from JIRA
Votes 0
Component/s Compiler, Foundation
Labels Bug, Foundation, Windows
Assignee @compnerd
Priority Medium

md5: bc89c69d3a5f5a94258b547fe2202d02

Issue Description:

After commit 5285bf7200d2999812a79df35ff2eebd41cc7ee7 noticeable part of Foundation tests on Windows became unstable.

Compiling with -enable-spec-devirt makes tests stable again.

Stack traces are different for different call sites. Mostly "Illegal Instruction" somewhere in Foundation.dll. Common in all cases: always related to bridged classes. In case below it is _NSCFConstantString.

The easiest steps I found (and most informative at the same time):

  1. Replace content of TestFoundation\main.swift with sample code:
import Foundation
_ = Bundle.main.infoDictionary // <- crash

2. Build and run TestFoundation target

Reconstructed stack:

swiftCore.dll         swift::TargetOpaqueExistentialContainer<swift::InProcess>::projectValue Line 31     swift\stdlib\public\runtime\ExistentialContainer.cpp(31)
swiftCore.dll         swift::TargetExistentialTypeMetadata<swift::InProcess>::projectValue Line 1858      swift\include\swift\ABI\Metadata.h(1858)
swiftCore.dll         tryDynamicCastBoxedSwiftValue Line 1904                                             swift\stdlib\public\runtime\Casting.cpp(1904)
swiftCore.dll         swift_dynamicCastImpl Line 2265                                                     swift\stdlib\public\runtime\Casting.cpp(2265)
...
Foundation.dll        Dictionary._conditionallyBridgeFromObjectiveC(_:result:) Line 70                    Foundation\Dictionary.swift(70)  // "guard let k = key as? Key", key is _NSCFConstantString
Foundation.dll        Dictionary._unconditionallyBridgeFromObjectiveC(_:) Line 91                         Foundation\Dictionary.swift(91)
Foundation.dll        NSDictionary._bridgeToSwift() Line 731                                              Foundation\NSDictionary.swift(731)
Foundation.dll        _StructTypeBridgeable._bridgeToAny() Line 50                                        Foundation\Bridging.swift(50)
Foundation.dll        __SwiftValue.fetch(nonOptional:) Line 164                                           Foundation\Bridging.swift(164)
Foundation.dll        __SwiftValue.fetch(_:) Line 82                                                      Foundation\Bridging.swift(82)
Foundation.dll        Bundle.infoDictionary Line 366                                                      Foundation\Bundle.swift(366)
...

@lxbndr
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lxbndr commented Feb 11, 2020

cc @compnerd

@lxbndr
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lxbndr commented Feb 14, 2020

Had opportunity to check this on slightly newer build, still reproducible.
LLVM 9505d8980c, Swift 1d2d8d4aee

@beccadax
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@swift-ci create

@compnerd
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compnerd commented Apr 1, 2020

This was the compiler optimizing away the initializer (reasonably). This has been resolved for now (added a {{@inline(never)}} function call with the result).

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
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@compnerd @beccadax @lxbndr