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EscapeAnalysis: fix a bug which results in not detecting an escape through an unowned reference. #40325

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merged 1 commit into from
Nov 30, 2021
Merged

EscapeAnalysis: fix a bug which results in not detecting an escape through an unowned reference. #40325

merged 1 commit into from
Nov 30, 2021

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eeckstein
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ref_to_unowned and similar instructions must be checked if the operand/result types are treated as "pointers" in escape analysis.
Fixes a miscompile.

https://bugs.swift.org/browse/SR-15527
rdar://85772200

@eeckstein
EscapeAnalysis: fix a bug with results in not detecting an escape thr…
4aae415 
…ough an unowned reference.

`ref_to_unowned`  and similar instructions must be checked if the operand/result types are treated as "pointers" in escape analysis.
Fixes a miscompile.

https://bugs.swift.org/browse/SR-15527
rdar://85772200
@eeckstein
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@swift-ci test

@eeckstein eeckstein changed the title EscapeAnalysis: fix a bug with results in not detecting an escape through an unowned reference. EscapeAnalysis: fix a bug which results in not detecting an escape through an unowned reference. Nov 30, 2021
atrick
atrick approved these changes Nov 30, 2021
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Too bad this wasn't caught with a simple assert. This fix is good. I had to debug it myself to understand the problem though.

Why do you bailout on unchecked_conditional_cast? SIL.rst says "representation or ownership changes are unsupported". So if the cast changes reference-ness, then there's a bigger problem.

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Why do you bailout on unchecked_conditional_cast?

Just to be on the safe side. It doesn't harm.

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atrick commented Nov 30, 2021 •
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Why do you bailout on unchecked_conditional_cast?

Just to be on the safe side. It doesn't harm.

At the very least, it means that we can't tell that a cast reference points to a local/unique object. I assume that's quite common and something we don't want to affect optimization. It could just be an assert instead of bailout.

Never mind, this only bails out in the rare case, so the PR is good as-is!

@eeckstein eeckstein merged commit 19f95eb into swiftlang:main Nov 30, 2021
@eeckstein eeckstein deleted the fix-escape-analysis branch November 30, 2021 20:58
@eeckstein eeckstein mentioned this pull request Dec 1, 2021
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