33 lines
1.0 KiB
Rust
33 lines
1.0 KiB
Rust
// This attempts to mutate `a` via a pointer derived from `addr_of!(a)`. That is UB
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// according to Miri. However, the decision to make this UB - and to allow
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// rustc to rely on that fact for the purpose of optimizations - has not been
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// finalized.
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//
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// As such, we include this test to ensure that copy prop does not rely on that
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// fact. Specifically, if `addr_of!(a)` could not be used to modify a, it would
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// be correct for CopyProp to replace all occurrences of `a` with `c` - but that
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// would cause `f(true)` to output `false` instead of `true`.
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#![feature(custom_mir, core_intrinsics)]
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#![allow(unused_assignments)]
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extern crate core;
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use core::intrinsics::mir::*;
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#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
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fn f(c: bool) -> bool {
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mir!({
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let a = c;
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let p = core::ptr::addr_of!(a);
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let p2 = core::ptr::addr_of_mut!(*p);
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*p2 = false;
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RET = c;
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Return()
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})
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}
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fn main() {
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assert_eq!(true, f(true));
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}
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// EMIT_MIR mutate_through_pointer.f.CopyProp.diff
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