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e9f29a8519
Introduce `Rvalue::ShallowInitBox` Polished version of #88700. Implements MCP rust-lang/compiler-team#460, and should allow #43596 to go forward. In short, creating an empty box is split from a nullary-op `NullOp::Box` into two steps, first a call to `exchange_malloc`, then a `Rvalue::ShallowInitBox` which transmutes `*mut u8` to a shallow-initialized `Box<T>`. This allows the `exchange_malloc` call to unwind. Details can be found in the MCP. `NullOp::Box` is not yet removed, purely to make reverting easier in case anything goes wrong as the result of this PR. If revert is needed a reversion of "Use Rvalue::ShallowInitBox for box expression" commit followed by a test bless should be sufficient. Experiments in #88700 showed a very slight compile-time perf regression due to (supposedly) slightly more time spent in LLVM. We could omit unwind edge generation (in non-`oom=panic` case) in box expression MIR construction to restore perf; but I don't think it's necessary since runtime perf isn't affected and perf difference is rather small. |
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| .. | ||
| alloc | ||
| collections | ||
| prelude | ||
| raw_vec | ||
| rc | ||
| sync | ||
| vec | ||
| alloc.rs | ||
| borrow.rs | ||
| boxed.rs | ||
| fmt.rs | ||
| lib.rs | ||
| macros.rs | ||
| raw_vec.rs | ||
| rc.rs | ||
| slice.rs | ||
| str.rs | ||
| string.rs | ||
| sync.rs | ||
| task.rs | ||
| tests.rs | ||