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Diffstat (limited to '')
-rw-r--r-- | tests/mir-opt/copy-prop/mutate_through_pointer.rs | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/tests/mir-opt/copy-prop/mutate_through_pointer.rs b/tests/mir-opt/copy-prop/mutate_through_pointer.rs new file mode 100644 index 000000000..da142e339 --- /dev/null +++ b/tests/mir-opt/copy-prop/mutate_through_pointer.rs @@ -0,0 +1,32 @@ +// This attempts to mutate `a` via a pointer derived from `addr_of!(a)`. That is UB +// according to Miri. However, the decision to make this UB - and to allow +// rustc to rely on that fact for the purpose of optimizations - has not been +// finalized. +// +// As such, we include this test to ensure that copy prop does not rely on that +// fact. Specifically, if `addr_of!(a)` could not be used to modify a, it would +// be correct for CopyProp to replace all occurrences of `a` with `c` - but that +// would cause `f(true)` to output `false` instead of `true`. + +#![feature(custom_mir, core_intrinsics)] +#![allow(unused_assignments)] +extern crate core; +use core::intrinsics::mir::*; + +#[custom_mir(dialect = "analysis", phase = "post-cleanup")] +fn f(c: bool) -> bool { + mir!({ + let a = c; + let p = core::ptr::addr_of!(a); + let p2 = core::ptr::addr_of_mut!(*p); + *p2 = false; + RET = c; + Return() + }) +} + +fn main() { + assert_eq!(true, f(true)); +} + +// EMIT_MIR mutate_through_pointer.f.CopyProp.diff |