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Auto merge of #108872 - cjgillot:simp-const-prop, r=oli-obk

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Strengthen state tracking in const-prop

Some/many of the changes are replicated between both the const-prop lint and the const-prop optimization.

Behaviour changes:
- const-prop opt does not give a span to propagated values. This was useless as that span's primary purpose is to diagnose evaluation failure in codegen.
- we remove the `OnlyPropagateInto` mode. It was only used for function arguments, which are better modeled by a write before entry.
- the tracking of assignments and discriminants make clearer that we do nothing in `NoPropagation` mode or on indirect places.
This commit is contained in:
bors 2023-03-12 23:27:52 +00:00
commit b05bb29008
14 changed files with 254 additions and 335 deletions
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30
compiler/rustc_const_eval/src/interpret/eval_context.rs
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@ -536,24 +536,20 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
local: mir::Local,
layout: Option<TyAndLayout<'tcx>>,
) -> InterpResult<'tcx, TyAndLayout<'tcx>> {
// `const_prop` runs into this with an invalid (empty) frame, so we
// have to support that case (mostly by skipping all caching).
match frame.locals.get(local).and_then(|state| state.layout.get()) {
None => {
let layout = from_known_layout(self.tcx, self.param_env, layout, || {
let local_ty = frame.body.local_decls[local].ty;
let local_ty =
self.subst_from_frame_and_normalize_erasing_regions(frame, local_ty)?;
self.layout_of(local_ty)
})?;
if let Some(state) = frame.locals.get(local) {
// Layouts of locals are requested a lot, so we cache them.
state.layout.set(Some(layout));
}
Ok(layout)
}
Some(layout) => Ok(layout),
let state = &frame.locals[local];
if let Some(layout) = state.layout.get() {
return Ok(layout);
}
let layout = from_known_layout(self.tcx, self.param_env, layout, || {
let local_ty = frame.body.local_decls[local].ty;
let local_ty = self.subst_from_frame_and_normalize_erasing_regions(frame, local_ty)?;
self.layout_of(local_ty)
})?;
// Layouts of locals are requested a lot, so we cache them.
state.layout.set(Some(layout));
Ok(layout)
}
/// Returns the actual dynamic size and alignment of the place at the given type.