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Auto merge of #96862 - oli-obk:enum_cast_mir, r=RalfJung

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Change enum->int casts to not go through MIR casts.

follow-up to https://github.com/rust-lang/rust/pull/96814

this simplifies all backends and even gives LLVM more information about the return value of `Rvalue::Discriminant`, enabling optimizations in more cases.
This commit is contained in:
bors 2022-07-05 09:36:29 +00:00
commit 96bdb398f9
1 changed files with 0 additions and 23 deletions
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23
src/base.rs
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@ -635,29 +635,6 @@ fn codegen_stmt<'tcx>(
let (ptr, _extra) = operand.load_scalar_pair(fx);
lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
}
} else if let ty::Adt(adt_def, _substs) = from_ty.kind() {
// enum -> discriminant value
assert!(adt_def.is_enum());
match to_ty.kind() {
ty::Uint(_) | ty::Int(_) => {}
_ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
}
let to_clif_ty = fx.clif_type(to_ty).unwrap();
let discriminant = crate::discriminant::codegen_get_discriminant(
fx,
operand,
fx.layout_of(operand.layout().ty.discriminant_ty(fx.tcx)),
)
.load_scalar(fx);
let res = crate::cast::clif_intcast(
fx,
discriminant,
to_clif_ty,
to_ty.is_signed(),
);
lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
} else {
let to_clif_ty = fx.clif_type(to_ty).unwrap();
let from = operand.load_scalar(fx);