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LLVM can make use of the `noalias` parameter attribute on the parameter to `drop_in_place` in areas like argument promotion. Because the Rust compiler fully controls the code for `drop_in_place`, it can soundly deduce parameter attributes on it. In the case of a value that has a programmer-defined Drop implementation, we know that the first thing `drop_in_place` will do is pass a pointer to the object to `Drop::drop`. `Drop::drop` takes `&mut`, so it must be guaranteed that there are no pointers to the object upon entering that function. Therefore, it should be safe to mark `noalias` there. With this patch, we mark `noalias` only when the type is a value with a programmer-defined Drop implementation. This is possibly overly conservative, but I thought that proceeding cautiously was best in this instance. |
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| .. | ||
| assembly | ||
| auxiliary | ||
| codegen | ||
| codegen-units | ||
| debuginfo | ||
| incremental | ||
| mir-opt | ||
| pretty | ||
| run-make | ||
| run-make-fulldeps | ||
| run-pass-valgrind | ||
| rustdoc | ||
| rustdoc-gui | ||
| rustdoc-js | ||
| rustdoc-js-std | ||
| rustdoc-json | ||
| rustdoc-ui | ||
| ui | ||
| ui-fulldeps | ||
| COMPILER_TESTS.md | ||