diff --git a/clippy_lints/src/invalid_upcast_comparisons.rs b/clippy_lints/src/invalid_upcast_comparisons.rs
index b1f70b30c12cf..82438d85c7a3a 100644
--- a/clippy_lints/src/invalid_upcast_comparisons.rs
+++ b/clippy_lints/src/invalid_upcast_comparisons.rs
@@ -1,5 +1,3 @@
-use std::cmp::Ordering;
-
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::layout::LayoutOf;
@@ -7,11 +5,11 @@ use rustc_middle::ty::{self, IntTy, UintTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::Span;
 
+use clippy_utils::comparisons;
 use clippy_utils::comparisons::Rel;
-use clippy_utils::consts::{constant, Constant};
+use clippy_utils::consts::{constant_full_int, FullInt};
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::source::snippet;
-use clippy_utils::{comparisons, sext};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -39,53 +37,6 @@ declare_clippy_lint! {
 
 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
 
-#[derive(Copy, Clone, Debug, Eq)]
-enum FullInt {
-    S(i128),
-    U(u128),
-}
-
-impl FullInt {
-    #[allow(clippy::cast_sign_loss)]
-    #[must_use]
-    fn cmp_s_u(s: i128, u: u128) -> Ordering {
-        if s < 0 {
-            Ordering::Less
-        } else if u > (i128::MAX as u128) {
-            Ordering::Greater
-        } else {
-            (s as u128).cmp(&u)
-        }
-    }
-}
-
-impl PartialEq for FullInt {
-    #[must_use]
-    fn eq(&self, other: &Self) -> bool {
-        self.partial_cmp(other).expect("`partial_cmp` only returns `Some(_)`") == Ordering::Equal
-    }
-}
-
-impl PartialOrd for FullInt {
-    #[must_use]
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(match (self, other) {
-            (&Self::S(s), &Self::S(o)) => s.cmp(&o),
-            (&Self::U(s), &Self::U(o)) => s.cmp(&o),
-            (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
-            (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
-        })
-    }
-}
-
-impl Ord for FullInt {
-    #[must_use]
-    fn cmp(&self, other: &Self) -> Ordering {
-        self.partial_cmp(other)
-            .expect("`partial_cmp` for FullInt can never return `None`")
-    }
-}
-
 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_>, expr: &'a Expr<'_>) -> Option<(FullInt, FullInt)> {
     if let ExprKind::Cast(cast_exp, _) = expr.kind {
         let pre_cast_ty = cx.typeck_results().expr_ty(cast_exp);
@@ -118,19 +69,6 @@ fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_>, expr: &'a Expr<'_>) ->
     }
 }
 
-fn node_as_const_fullint<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<FullInt> {
-    let val = constant(cx, cx.typeck_results(), expr)?.0;
-    if let Constant::Int(const_int) = val {
-        match *cx.typeck_results().expr_ty(expr).kind() {
-            ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
-            ty::Uint(_) => Some(FullInt::U(const_int)),
-            _ => None,
-        }
-    } else {
-        None
-    }
-}
-
 fn err_upcast_comparison(cx: &LateContext<'_>, span: Span, expr: &Expr<'_>, always: bool) {
     if let ExprKind::Cast(cast_val, _) = expr.kind {
         span_lint(
@@ -156,7 +94,7 @@ fn upcast_comparison_bounds_err<'tcx>(
     invert: bool,
 ) {
     if let Some((lb, ub)) = lhs_bounds {
-        if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
+        if let Some(norm_rhs_val) = constant_full_int(cx, cx.typeck_results(), rhs) {
             if rel == Rel::Eq || rel == Rel::Ne {
                 if norm_rhs_val < lb || norm_rhs_val > ub {
                     err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
diff --git a/clippy_utils/src/consts.rs b/clippy_utils/src/consts.rs
index 8bf31807d55d1..3e5d74a66f4e8 100644
--- a/clippy_utils/src/consts.rs
+++ b/clippy_utils/src/consts.rs
@@ -155,6 +155,19 @@ impl Constant {
             _ => None,
         }
     }
+
+    /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
+    pub fn int_value(&self, cx: &LateContext<'_>, val_type: Ty<'_>) -> Option<FullInt> {
+        if let Constant::Int(const_int) = *self {
+            match *val_type.kind() {
+                ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
+                ty::Uint(_) => Some(FullInt::U(const_int)),
+                _ => None,
+            }
+        } else {
+            None
+        }
+    }
 }
 
 /// Parses a `LitKind` to a `Constant`.
@@ -202,6 +215,61 @@ pub fn constant_simple<'tcx>(
     constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
 }
 
+pub fn constant_full_int(
+    lcx: &LateContext<'tcx>,
+    typeck_results: &ty::TypeckResults<'tcx>,
+    e: &Expr<'_>,
+) -> Option<FullInt> {
+    constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
+}
+
+#[derive(Copy, Clone, Debug, Eq)]
+pub enum FullInt {
+    S(i128),
+    U(u128),
+}
+
+impl FullInt {
+    #[allow(clippy::cast_sign_loss)]
+    #[must_use]
+    fn cmp_s_u(s: i128, u: u128) -> Ordering {
+        if s < 0 {
+            Ordering::Less
+        } else if u > (i128::MAX as u128) {
+            Ordering::Greater
+        } else {
+            (s as u128).cmp(&u)
+        }
+    }
+}
+
+impl PartialEq for FullInt {
+    #[must_use]
+    fn eq(&self, other: &Self) -> bool {
+        self.partial_cmp(other).expect("`partial_cmp` only returns `Some(_)`") == Ordering::Equal
+    }
+}
+
+impl PartialOrd for FullInt {
+    #[must_use]
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(match (self, other) {
+            (&Self::S(s), &Self::S(o)) => s.cmp(&o),
+            (&Self::U(s), &Self::U(o)) => s.cmp(&o),
+            (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
+            (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
+        })
+    }
+}
+
+impl Ord for FullInt {
+    #[must_use]
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.partial_cmp(other)
+            .expect("`partial_cmp` for FullInt can never return `None`")
+    }
+}
+
 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
 pub fn constant_context<'a, 'tcx>(
     lcx: &'a LateContext<'tcx>,