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b2c717fa33
I was looking into `array::IntoIter` optimization, and noticed that it wasn't annotating the loads with `noundef` for simple things like `array::IntoIter<i32, N>`. Turned out to be a more general problem as `MaybeUninit::assume_init_read` isn't marking the load as initialized (<https://rust.godbolt.org/z/Mxd8TPTnv>), which is unfortunate since that's basically its reason to exist. This PR lowers `ptr::read(p)` to `copy *p` in MIR, which fortuitiously also improves the IR we give to LLVM for things like `mem::replace`.
21 lines
866 B
Plaintext
21 lines
866 B
Plaintext
error[E0080]: evaluation of constant value failed
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--> $SRC_DIR/core/src/ptr/mod.rs:LL:COL
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= note: unable to turn pointer into raw bytes
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= help: this code performed an operation that depends on the underlying bytes representing a pointer
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= help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
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note: inside `std::ptr::read::<u8>`
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--> $SRC_DIR/core/src/ptr/mod.rs:LL:COL
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note: inside `ptr::const_ptr::<impl *const u8>::read`
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--> $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
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note: inside `C`
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--> $DIR/issue-miri-1910.rs:8:5
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LL | (&foo as *const _ as *const u8).add(one_and_a_half_pointers).read();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0080`.
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