bjoernager/rust
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Rollup merge of #90081 - woppopo:const_write_bytes, r=oli-obk

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Make `intrinsics::write_bytes` const

This is required to constify `MaybeUninit::zeroed` and `(*mut T)::write_bytes`.

Tracking issue: #86302
This commit is contained in:
Matthias Krüger 2021-12-11 23:31:48 +01:00 • committed by GitHub
commit 9383a49cd4
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3 changed files with 72 additions and 2 deletions
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24
compiler/rustc_const_eval/src/interpret/intrinsics.rs
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@ -322,6 +322,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
sym::copy => {
self.copy_intrinsic(&args[0], &args[1], &args[2], /*nonoverlapping*/ false)?;
}
sym::write_bytes => {
self.write_bytes_intrinsic(&args[0], &args[1], &args[2])?;
}
sym::offset => {
let ptr = self.read_pointer(&args[0])?;
let offset_count = self.read_scalar(&args[1])?.to_machine_isize(self)?;
@ -567,6 +570,27 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
self.memory.copy(src, align, dst, align, size, nonoverlapping)
}
pub(crate) fn write_bytes_intrinsic(
&mut self,
dst: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::PointerTag>,
byte: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::PointerTag>,
count: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::PointerTag>,
) -> InterpResult<'tcx> {
let layout = self.layout_of(dst.layout.ty.builtin_deref(true).unwrap().ty)?;
let dst = self.read_pointer(&dst)?;
let byte = self.read_scalar(&byte)?.to_u8()?;
let count = self.read_scalar(&count)?.to_machine_usize(self)?;
let len = layout
.size
.checked_mul(count, self)
.ok_or_else(|| err_ub_format!("overflow computing total size of `write_bytes`"))?;
let bytes = std::iter::repeat(byte).take(len.bytes_usize());
self.memory.write_bytes(dst, bytes)
}
pub(crate) fn raw_eq_intrinsic(
&mut self,
lhs: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::PointerTag>,