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use llvm.lifetime.end to mark the end of unique pointer lifetimes #6755

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thestinger opened this issue May 26, 2013 · 5 comments
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use llvm.lifetime.end to mark the end of unique pointer lifetimes #6755

thestinger opened this issue May 26, 2013 · 5 comments
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I-slow Issue: Problems and improvements with respect to performance of generated code.

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@thestinger
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This applies to unique pointers going out of scope when the compiler knows they weren't moved from.
@thestinger
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Somewhat related to #5016.

@emberian
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triage bump; still relevant.

@alexcrichton
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I don't think that this would help alleviate the problem in #5016. I took the IR from #8484 (where extra glue was generated), and then manually added the calls to llvm.lifetime.{start,end} to the IR. The resulting optimized IR didn't have the glue removed, even though loads/stores were undefined to the location.

This may still help other optimization passes, but I'm not sure.

@huonw
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huonw commented Dec 19, 2013

Triage, lots of lifetimes in Rust, but still no lifetimes in LLVM. :(

@thestinger
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This can be left to LLVM, since free implies that the pointer is dead.

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@alexcrichton @emberian @huonw @thestinger