Fix major compile time regression#25423
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The assume intrinsic has a strong, negative impact on compile times, so we're currently only using it in places where LLVM can simplify it to nonnull metadata on a load intruction. Unfortunately a recent change that fixed invalid assume calls introduce new assume calls for which this simplification can not happen, leading to a massive regression in compile times in certain cases. Moving the assumptions from the middle of the function to the beginning allows the simplification to happen again, bringing compile times back to their old levels. Fixes rust-lang#25393
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(rust_highfive has picked a reviewer for you, use r? to override) |
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@bors r+ Nice investigation! |
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📌 Commit 0260333 has been approved by |
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⌛ Testing commit 0260333 with merge daa46b4... |
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💔 Test failed - auto-linux-32-nopt-t |
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I'm going to assume that this is a transient build test failure: |
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@bors retry |
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May 15, 2015
The assume intrinsic has a strong, negative impact on compile times, so we're currently only using it in places where LLVM can simplify it to nonnull metadata on a load intruction. Unfortunately a recent change that fixed invalid assume calls introduce new assume calls for which this simplification can not happen, leading to a massive regression in compile times in certain cases. Moving the assumptions from the middle of the function to the beginning allows the simplification to happen again, bringing compile times back to their old levels. Fixes #25393
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The assume intrinsic has a strong, negative impact on compile times, so
we're currently only using it in places where LLVM can simplify it to
nonnull metadata on a load intruction. Unfortunately a recent change
that fixed invalid assume calls introduce new assume calls for which
this simplification can not happen, leading to a massive regression in
compile times in certain cases.
Moving the assumptions from the middle of the function to the beginning
allows the simplification to happen again, bringing compile times back
to their old levels.
Fixes #25393