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valtree_to_const_value: add fast-path for Scalar tuples/structs

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Ralf Jung 2023-09-14 07:40:05 +02:00
parent 3aedb85a27
commit 06947be196
1 changed files with 16 additions and 1 deletions
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17
compiler/rustc_const_eval/src/const_eval/valtrees.rs
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@ -7,7 +7,7 @@ use crate::interpret::{
intern_const_alloc_recursive, ConstValue, ImmTy, Immediate, InternKind, MemPlaceMeta,
MemoryKind, PlaceTy, Projectable, Scalar,
};
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt};
use rustc_span::source_map::DUMMY_SP;
use rustc_target::abi::VariantIdx;
@ -239,6 +239,21 @@ pub fn valtree_to_const_value<'tcx>(
// Fast path to avoid some allocations.
return ConstValue::ZeroSized;
}
if layout.abi.is_scalar()
&& (matches!(ty.kind(), ty::Tuple(_))
|| matches!(ty.kind(), ty::Adt(def, _) if def.is_struct()))
{
// A Scalar tuple/struct; we can avoid creating an allocation.
let branches = valtree.unwrap_branch();
// Find the non-ZST field. (There can be aligned ZST!)
for (i, &inner_valtree) in branches.iter().enumerate() {
let field = layout.field(&LayoutCx { tcx, param_env }, i);
if !field.is_zst() {
return valtree_to_const_value(tcx, param_env.and(field.ty), inner_valtree);
}
}
bug!("could not find non-ZST field during in {layout:#?}");
}
let mut ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, CanAccessStatics::No);