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internal: Remove allocation on mir eval memory write #15571

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merged 1 commit into from
Sep 7, 2023
Merged

internal: Remove allocation on mir eval memory write #15571

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46 changes: 43 additions & 3 deletions crates/hir-ty/src/mir/eval.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -215,9 +215,7 @@ impl Interval {
}

fn write_from_interval(&self, memory: &mut Evaluator<'_>, interval: Interval) -> Result<()> {
// FIXME: this could be more efficient
let bytes = &interval.get(memory)?.to_vec();
memory.write_memory(self.addr, bytes)
memory.copy_from_interval(self.addr, interval)
}

fn slice(self, range: Range<usize>) -> Interval {
Expand Down Expand Up @@ -1760,6 +1758,48 @@ impl Evaluator<'_> {
Ok(())
}

fn copy_from_interval(&mut self, addr: Address, r: Interval) -> Result<()> {
if r.size == 0 {
return Ok(());
}

let oob = || MirEvalError::UndefinedBehavior("out of bounds memory write".to_string());

match (addr, r.addr) {
(Stack(dst), Stack(src)) => {
if self.stack.len() < src + r.size || self.stack.len() < dst + r.size {
return Err(oob());
}
self.stack.copy_within(src..src + r.size, dst)
}
(Heap(dst), Heap(src)) => {
if self.stack.len() < src + r.size || self.stack.len() < dst + r.size {
return Err(oob());
}
self.heap.copy_within(src..src + r.size, dst)
}
(Stack(dst), Heap(src)) => {
self.stack
.get_mut(dst..dst + r.size)
.ok_or_else(oob)?
.copy_from_slice(self.heap.get(src..src + r.size).ok_or_else(oob)?);
}
(Heap(dst), Stack(src)) => {
self.heap
.get_mut(dst..dst + r.size)
.ok_or_else(oob)?
.copy_from_slice(self.stack.get(src..src + r.size).ok_or_else(oob)?);
}
_ => {
return Err(MirEvalError::UndefinedBehavior(format!(
"invalid memory write at address {addr:?}"
)))
}
}

Ok(())
}

fn size_align_of(&self, ty: &Ty, locals: &Locals) -> Result<Option<(usize, usize)>> {
if let Some(layout) = self.layout_cache.borrow().get(ty) {
return Ok(layout
Expand Down