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fix fast-path for try_eval_scalar_int #116457

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merged 1 commit into from
Oct 7, 2023
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fix fast-path for try_eval_scalar_int #116457

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30 changes: 15 additions & 15 deletions compiler/rustc_middle/src/mir/consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -213,10 +213,10 @@ impl<'tcx> Const<'tcx> {
pub fn try_to_scalar(self) -> Option<Scalar> {
match self {
Const::Ty(c) => match c.kind() {
ty::ConstKind::Value(valtree) => match valtree {
ty::ValTree::Leaf(scalar_int) => Some(Scalar::Int(scalar_int)),
ty::ValTree::Branch(_) => None,
},
ty::ConstKind::Value(valtree) if c.ty().is_primitive() => {
// A valtree of a type where leaves directly represent the scalar const value.
Some(valtree.unwrap_leaf().into())
}
_ => None,
},
Const::Val(val, _) => val.try_to_scalar(),
Expand Down Expand Up @@ -279,7 +279,16 @@ impl<'tcx> Const<'tcx> {
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<Scalar> {
self.eval(tcx, param_env, None).ok()?.try_to_scalar()
match self {
Const::Ty(c) if c.ty().is_primitive() => {
// Avoid the `valtree_to_const_val` query. Can only be done on primitive types that
// are valtree leaves, and *not* on references. (References should return the
// pointer here, which valtrees don't represent.)
let val = c.eval(tcx, param_env, None).ok()?;
Some(val.unwrap_leaf().into())
}
_ => self.eval(tcx, param_env, None).ok()?.try_to_scalar(),
}
}

#[inline]
Expand All @@ -288,16 +297,7 @@ impl<'tcx> Const<'tcx> {
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<ScalarInt> {
match self {
// If the constant is already evaluated, we shortcut here.
Const::Ty(c) if let ty::ConstKind::Value(valtree) = c.kind() => {
valtree.try_to_scalar_int()
},
// This is a more general form of the previous case.
_ => {
self.try_eval_scalar(tcx, param_env)?.try_to_int().ok()
},
}
self.try_eval_scalar(tcx, param_env)?.try_to_int().ok()
}

#[inline]
Expand Down