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Rollup merge of #92274 - woppopo:const_deallocate, r=oli-obk

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Add `intrinsics::const_deallocate`

Tracking issue: #79597
Related: #91884

This allows deallocation of a memory allocated by `intrinsics::const_allocate`. At the moment, this can be only used to reduce memory usage, but in the future this may be useful to detect memory leaks (If an allocated memory remains after evaluation, raise an error...?).
This commit is contained in:
Matthias Krüger 2022-01-29 14:46:30 +01:00 • committed by GitHub
commit 9e86a434a7
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18 changed files with 274 additions and 4 deletions
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27
compiler/rustc_const_eval/src/const_eval/machine.rs
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@ -347,6 +347,33 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
)?;
ecx.write_pointer(ptr, dest)?;
}
sym::const_deallocate => {
let ptr = ecx.read_pointer(&args[0])?;
let size = ecx.read_scalar(&args[1])?.to_machine_usize(ecx)?;
let align = ecx.read_scalar(&args[2])?.to_machine_usize(ecx)?;
let size = Size::from_bytes(size);
let align = match Align::from_bytes(align) {
Ok(a) => a,
Err(err) => throw_ub_format!("align has to be a power of 2, {}", err),
};
// If an allocation is created in an another const,
// we don't deallocate it.
let (alloc_id, _, _) = ecx.memory.ptr_get_alloc(ptr)?;
let is_allocated_in_another_const = matches!(
ecx.tcx.get_global_alloc(alloc_id),
Some(interpret::GlobalAlloc::Memory(_))
);
if !is_allocated_in_another_const {
ecx.memory.deallocate(
ptr,
Some((size, align)),
interpret::MemoryKind::Machine(MemoryKind::Heap),
)?;
}
}
_ => {
return Err(ConstEvalErrKind::NeedsRfc(format!(
"calling intrinsic `{}`",