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Lower to a memset(undef) when Rvalue::Repeat repeats uninit

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This commit is contained in:
Ben Kimock 2025-03-17 21:29:07 -04:00
parent 43a2e9d2c7
commit 8e7d8ddffe
3 changed files with 66 additions and 4 deletions
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28
compiler/rustc_middle/src/mir/consts.rs
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@ -9,7 +9,9 @@ use rustc_span::{DUMMY_SP, Span, Symbol};
use rustc_type_ir::TypeVisitableExt;
use super::interpret::ReportedErrorInfo;
use crate::mir::interpret::{AllocId, ConstAllocation, ErrorHandled, Scalar, alloc_range};
use crate::mir::interpret::{
AllocId, AllocRange, ConstAllocation, ErrorHandled, GlobalAlloc, Scalar, alloc_range,
};
use crate::mir::{Promoted, pretty_print_const_value};
use crate::ty::print::{pretty_print_const, with_no_trimmed_paths};
use crate::ty::{self, ConstKind, GenericArgsRef, ScalarInt, Ty, TyCtxt};
@ -192,9 +194,31 @@ impl<'tcx> ConstValue<'tcx> {
.unwrap_memory()
.inner()
.provenance()
.range_empty(super::AllocRange::from(offset..offset + size), &tcx),
.range_empty(AllocRange::from(offset..offset + size), &tcx),
}
}
/// Check if a constant only contains uninitialized bytes.
pub fn all_bytes_uninit(&self, tcx: TyCtxt<'tcx>) -> bool {
let ConstValue::Indirect { alloc_id, .. } = self else {
return false;
};
let alloc = tcx.global_alloc(*alloc_id);
let GlobalAlloc::Memory(alloc) = alloc else {
return false;
};
let init_mask = alloc.0.init_mask();
let init_range = init_mask.is_range_initialized(AllocRange {
start: Size::ZERO,
size: Size::from_bytes(alloc.0.len()),
});
if let Err(range) = init_range {
if range.size == alloc.0.size() {
return true;
}
}
false
}
}
///////////////////////////////////////////////////////////////////////////