diff --git a/tests/codegen/enum/enum-discriminant-eq.rs b/tests/codegen/enum/enum-discriminant-eq.rs
new file mode 100644
index 0000000..fd6f349
--- /dev/null
+++ b/tests/codegen/enum/enum-discriminant-eq.rs
@@ -0,0 +1,231 @@
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
+//@ min-llvm-version: 20
+//@ only-64bit
+
+// The `derive(PartialEq)` on enums with field-less variants compares discriminants,
+// so make sure we emit that in some reasonable way.
+
+#![crate_type = "lib"]
+#![feature(ascii_char)]
+#![feature(core_intrinsics)]
+#![feature(repr128)]
+
+use std::ascii::Char as AC;
+use std::cmp::Ordering;
+use std::intrinsics::discriminant_value;
+use std::num::NonZero;
+
+// A type that's bigger than `isize`, unlike the usual cases that have small tags.
+#[repr(u128)]
+pub enum Giant {
+    Two = 2,
+    Three = 3,
+    Four = 4,
+}
+
+#[unsafe(no_mangle)]
+pub fn opt_bool_eq_discr(a: Option<bool>, b: Option<bool>) -> bool {
+    // CHECK-LABEL: @opt_bool_eq_discr(
+    // CHECK: %[[A:.+]] = icmp ne i8 %a, 2
+    // CHECK: %[[B:.+]] = icmp eq i8 %b, 2
+    // CHECK: %[[R:.+]] = xor i1 %[[A]], %[[B]]
+    // CHECK: ret i1 %[[R]]
+
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn opt_ord_eq_discr(a: Option<Ordering>, b: Option<Ordering>) -> bool {
+    // CHECK-LABEL: @opt_ord_eq_discr(
+    // CHECK: %[[A:.+]] = icmp ne i8 %a, 2
+    // CHECK: %[[B:.+]] = icmp eq i8 %b, 2
+    // CHECK: %[[R:.+]] = xor i1 %[[A]], %[[B]]
+    // CHECK: ret i1 %[[R]]
+
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn opt_nz32_eq_discr(a: Option<NonZero<u32>>, b: Option<NonZero<u32>>) -> bool {
+    // CHECK-LABEL: @opt_nz32_eq_discr(
+    // CHECK: %[[A:.+]] = icmp ne i32 %a, 0
+    // CHECK: %[[B:.+]] = icmp eq i32 %b, 0
+    // CHECK: %[[R:.+]] = xor i1 %[[A]], %[[B]]
+    // CHECK: ret i1 %[[R]]
+
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn opt_ac_eq_discr(a: Option<AC>, b: Option<AC>) -> bool {
+    // CHECK-LABEL: @opt_ac_eq_discr(
+    // CHECK: %[[A:.+]] = icmp ne i8 %a, -128
+    // CHECK: %[[B:.+]] = icmp eq i8 %b, -128
+    // CHECK: %[[R:.+]] = xor i1 %[[A]], %[[B]]
+    // CHECK: ret i1 %[[R]]
+
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn opt_giant_eq_discr(a: Option<Giant>, b: Option<Giant>) -> bool {
+    // CHECK-LABEL: @opt_giant_eq_discr(
+    // CHECK: %[[A:.+]] = icmp ne i128 %a, 1
+    // CHECK: %[[B:.+]] = icmp eq i128 %b, 1
+    // CHECK: %[[R:.+]] = xor i1 %[[A]], %[[B]]
+    // CHECK: ret i1 %[[R]]
+
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+pub enum Mid<T> {
+    Before,
+    Thing(T),
+    After,
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_bool_eq_discr(a: Mid<bool>, b: Mid<bool>) -> bool {
+    // CHECK-LABEL: @mid_bool_eq_discr(
+
+    // CHECK: %[[A_REL_DISCR:.+]] = add nsw i8 %a, -2
+    // CHECK: %[[A_IS_NICHE:.+]] = icmp ult i8 %[[A_REL_DISCR]], 3
+    // CHECK: %[[A_NOT_HOLE:.+]] = icmp ne i8 %[[A_REL_DISCR]], 1
+    // CHECK: tail call void @llvm.assume(i1 %[[A_NOT_HOLE]])
+    // CHECK: %[[A_DISCR:.+]] = select i1 %[[A_IS_NICHE]], i8 %[[A_REL_DISCR]], i8 1
+
+    // CHECK: %[[B_REL_DISCR:.+]] = add nsw i8 %b, -2
+    // CHECK: %[[B_IS_NICHE:.+]] = icmp ult i8 %[[B_REL_DISCR]], 3
+    // CHECK: %[[B_NOT_HOLE:.+]] = icmp ne i8 %[[B_REL_DISCR]], 1
+    // CHECK: tail call void @llvm.assume(i1 %[[B_NOT_HOLE]])
+    // CHECK: %[[B_DISCR:.+]] = select i1 %[[B_IS_NICHE]], i8 %[[B_REL_DISCR]], i8 1
+
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_ord_eq_discr(a: Mid<Ordering>, b: Mid<Ordering>) -> bool {
+    // CHECK-LABEL: @mid_ord_eq_discr(
+
+    // CHECK: %[[A_REL_DISCR:.+]] = add nsw i8 %a, -2
+    // CHECK: %[[A_IS_NICHE:.+]] = icmp ult i8 %[[A_REL_DISCR]], 3
+    // CHECK: %[[A_NOT_HOLE:.+]] = icmp ne i8 %[[A_REL_DISCR]], 1
+    // CHECK: tail call void @llvm.assume(i1 %[[A_NOT_HOLE]])
+    // CHECK: %[[A_DISCR:.+]] = select i1 %[[A_IS_NICHE]], i8 %[[A_REL_DISCR]], i8 1
+
+    // CHECK: %[[B_REL_DISCR:.+]] = add nsw i8 %b, -2
+    // CHECK: %[[B_IS_NICHE:.+]] = icmp ult i8 %[[B_REL_DISCR]], 3
+    // CHECK: %[[B_NOT_HOLE:.+]] = icmp ne i8 %[[B_REL_DISCR]], 1
+    // CHECK: tail call void @llvm.assume(i1 %[[B_NOT_HOLE]])
+    // CHECK: %[[B_DISCR:.+]] = select i1 %[[B_IS_NICHE]], i8 %[[B_REL_DISCR]], i8 1
+
+    // CHECK: %[[R:.+]] = icmp eq i8 %[[A_DISCR]], %[[B_DISCR]]
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_nz32_eq_discr(a: Mid<NonZero<u32>>, b: Mid<NonZero<u32>>) -> bool {
+    // CHECK-LABEL: @mid_nz32_eq_discr(
+    // CHECK: %[[R:.+]] = icmp eq i32 %a.0, %b.0
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_ac_eq_discr(a: Mid<AC>, b: Mid<AC>) -> bool {
+    // CHECK-LABEL: @mid_ac_eq_discr(
+
+    // CHECK: %[[A_REL_DISCR:.+]] = xor i8 %a, -128
+    // CHECK: %[[A_IS_NICHE:.+]] = icmp ult i8 %[[A_REL_DISCR]], 3
+    // CHECK: %[[A_NOT_HOLE:.+]] = icmp ne i8 %a, -127
+    // CHECK: tail call void @llvm.assume(i1 %[[A_NOT_HOLE]])
+    // CHECK: %[[A_DISCR:.+]] = select i1 %[[A_IS_NICHE]], i8 %[[A_REL_DISCR]], i8 1
+
+    // CHECK: %[[B_REL_DISCR:.+]] = xor i8 %b, -128
+    // CHECK: %[[B_IS_NICHE:.+]] = icmp ult i8 %[[B_REL_DISCR]], 3
+    // CHECK: %[[B_NOT_HOLE:.+]] = icmp ne i8 %b, -127
+    // CHECK: tail call void @llvm.assume(i1 %[[B_NOT_HOLE]])
+    // CHECK: %[[B_DISCR:.+]] = select i1 %[[B_IS_NICHE]], i8 %[[B_REL_DISCR]], i8 1
+
+    // CHECK: %[[R:.+]] = icmp eq i8 %[[A_DISCR]], %[[B_DISCR]]
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+// FIXME: This should be improved once our LLVM fork picks up the fix for
+// <https://github.com/llvm/llvm-project/issues/134024>
+#[unsafe(no_mangle)]
+pub fn mid_giant_eq_discr(a: Mid<Giant>, b: Mid<Giant>) -> bool {
+    // CHECK-LABEL: @mid_giant_eq_discr(
+
+    // CHECK: %[[A_REL_DISCR_WIDE:.+]] = add nsw i128 %a, -5
+    // CHECK: %[[A_REL_DISCR:.+]] = trunc nsw i128 %[[A_REL_DISCR_WIDE]] to i64
+    // CHECK: %[[A_IS_NICHE:.+]] = icmp ult i128 %[[A_REL_DISCR_WIDE]], 3
+    // CHECK: %[[A_NOT_HOLE:.+]] = icmp ne i128 %[[A_REL_DISCR_WIDE]], 1
+    // CHECK: tail call void @llvm.assume(i1 %[[A_NOT_HOLE]])
+    // CHECK: %[[A_DISCR:.+]] = select i1 %[[A_IS_NICHE]], i64 %[[A_REL_DISCR]], i64 1
+
+    // CHECK: %[[B_REL_DISCR_WIDE:.+]] = add nsw i128 %b, -5
+    // CHECK: %[[B_REL_DISCR:.+]] = trunc nsw i128 %[[B_REL_DISCR_WIDE]] to i64
+    // CHECK: %[[B_IS_NICHE:.+]] = icmp ult i128 %[[B_REL_DISCR_WIDE]], 3
+    // CHECK: %[[B_NOT_HOLE:.+]] = icmp ne i128 %[[B_REL_DISCR_WIDE]], 1
+    // CHECK: tail call void @llvm.assume(i1 %[[B_NOT_HOLE]])
+    // CHECK: %[[B_DISCR:.+]] = select i1 %[[B_IS_NICHE]], i64 %[[B_REL_DISCR]], i64 1
+
+    // CHECK: %[[R:.+]] = icmp eq i64 %[[A_DISCR]], %[[B_DISCR]]
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == discriminant_value(&b)
+}
+
+// In niche-encoded enums, testing for the untagged variant should optimize to a
+// straight-forward comparison looking for the natural range of the payload value.
+// FIXME: A bunch don't, though.
+
+#[unsafe(no_mangle)]
+pub fn mid_bool_is_thing(a: Mid<bool>) -> bool {
+    // CHECK-LABEL: @mid_bool_is_thing(
+
+    // CHECK: %[[REL_DISCR:.+]] = add nsw i8 %a, -2
+    // CHECK: %[[R:.+]] = icmp ugt i8 %[[REL_DISCR]], 2
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == 1
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_ord_is_thing(a: Mid<Ordering>) -> bool {
+    // CHECK-LABEL: @mid_ord_is_thing(
+    // CHECK: %[[REL_DISCR:.+]] = add nsw i8 %a, -2
+    // CHECK: %[[R:.+]] = icmp ugt i8 %[[REL_DISCR]], 2
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == 1
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_nz32_is_thing(a: Mid<NonZero<u32>>) -> bool {
+    // CHECK-LABEL: @mid_nz32_is_thing(
+    // CHECK: %[[R:.+]] = icmp eq i32 %a.0, 1
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == 1
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_ac_is_thing(a: Mid<AC>) -> bool {
+    // CHECK-LABEL: @mid_ac_is_thing(
+    // CHECK: %[[R:.+]] = icmp sgt i8 %a, -1
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == 1
+}
+
+#[unsafe(no_mangle)]
+pub fn mid_giant_is_thing(a: Mid<Giant>) -> bool {
+    // CHECK-LABEL: @mid_giant_is_thing(
+    // CHECK: %[[REL_DISCR_WIDE:.+]] = add nsw i128 %a, -5
+    // CHECK: %[[REL_DISCR:.+]] = trunc nsw i128 %[[REL_DISCR_WIDE]] to i64
+    // CHECK: %[[NOT_NICHE:.+]] = icmp ugt i128 %[[REL_DISCR_WIDE]], 2
+    // CHECK: %[[IS_MID_VARIANT:.+]] = icmp eq i64 %[[REL_DISCR]], 1
+    // CHECK: %[[R:.+]] = select i1 %[[NOT_NICHE]], i1 true, i1 %[[IS_MID_VARIANT]]
+    // CHECK: ret i1 %[[R]]
+    discriminant_value(&a) == 1
+}
diff --git a/tests/codegen/enum/enum-match.rs b/tests/codegen/enum/enum-match.rs
index 9863500..9725e64 100644
--- a/tests/codegen/enum/enum-match.rs
+++ b/tests/codegen/enum/enum-match.rs
@@ -471,3 +471,310 @@ pub fn match5(e: HugeVariantIndex) -> u8 {
         Possible259 => 100,
     }
 }
+
+// Make an enum where the niche tags wrap both as signed and as unsigned, to hit
+// the most-fallback case where there's just nothing smart to do.
+
+pub enum E10Through65 {
+    D10 = 10,
+    D11 = 11,
+    D12 = 12,
+    D13 = 13,
+    D14 = 14,
+    D15 = 15,
+    D16 = 16,
+    D17 = 17,
+    D18 = 18,
+    D19 = 19,
+    D20 = 20,
+    D21 = 21,
+    D22 = 22,
+    D23 = 23,
+    D24 = 24,
+    D25 = 25,
+    D26 = 26,
+    D27 = 27,
+    D28 = 28,
+    D29 = 29,
+    D30 = 30,
+    D31 = 31,
+    D32 = 32,
+    D33 = 33,
+    D34 = 34,
+    D35 = 35,
+    D36 = 36,
+    D37 = 37,
+    D38 = 38,
+    D39 = 39,
+    D40 = 40,
+    D41 = 41,
+    D42 = 42,
+    D43 = 43,
+    D44 = 44,
+    D45 = 45,
+    D46 = 46,
+    D47 = 47,
+    D48 = 48,
+    D49 = 49,
+    D50 = 50,
+    D51 = 51,
+    D52 = 52,
+    D53 = 53,
+    D54 = 54,
+    D55 = 55,
+    D56 = 56,
+    D57 = 57,
+    D58 = 58,
+    D59 = 59,
+    D60 = 60,
+    D61 = 61,
+    D62 = 62,
+    D63 = 63,
+    D64 = 64,
+    D65 = 65,
+}
+
+pub enum Tricky {
+    Untagged(E10Through65),
+    V001,
+    V002,
+    V003,
+    V004,
+    V005,
+    V006,
+    V007,
+    V008,
+    V009,
+    V010,
+    V011,
+    V012,
+    V013,
+    V014,
+    V015,
+    V016,
+    V017,
+    V018,
+    V019,
+    V020,
+    V021,
+    V022,
+    V023,
+    V024,
+    V025,
+    V026,
+    V027,
+    V028,
+    V029,
+    V030,
+    V031,
+    V032,
+    V033,
+    V034,
+    V035,
+    V036,
+    V037,
+    V038,
+    V039,
+    V040,
+    V041,
+    V042,
+    V043,
+    V044,
+    V045,
+    V046,
+    V047,
+    V048,
+    V049,
+    V050,
+    V051,
+    V052,
+    V053,
+    V054,
+    V055,
+    V056,
+    V057,
+    V058,
+    V059,
+    V060,
+    V061,
+    V062,
+    V063,
+    V064,
+    V065,
+    V066,
+    V067,
+    V068,
+    V069,
+    V070,
+    V071,
+    V072,
+    V073,
+    V074,
+    V075,
+    V076,
+    V077,
+    V078,
+    V079,
+    V080,
+    V081,
+    V082,
+    V083,
+    V084,
+    V085,
+    V086,
+    V087,
+    V088,
+    V089,
+    V090,
+    V091,
+    V092,
+    V093,
+    V094,
+    V095,
+    V096,
+    V097,
+    V098,
+    V099,
+    V100,
+    V101,
+    V102,
+    V103,
+    V104,
+    V105,
+    V106,
+    V107,
+    V108,
+    V109,
+    V110,
+    V111,
+    V112,
+    V113,
+    V114,
+    V115,
+    V116,
+    V117,
+    V118,
+    V119,
+    V120,
+    V121,
+    V122,
+    V123,
+    V124,
+    V125,
+    V126,
+    V127,
+    V128,
+    V129,
+    V130,
+    V131,
+    V132,
+    V133,
+    V134,
+    V135,
+    V136,
+    V137,
+    V138,
+    V139,
+    V140,
+    V141,
+    V142,
+    V143,
+    V144,
+    V145,
+    V146,
+    V147,
+    V148,
+    V149,
+    V150,
+    V151,
+    V152,
+    V153,
+    V154,
+    V155,
+    V156,
+    V157,
+    V158,
+    V159,
+    V160,
+    V161,
+    V162,
+    V163,
+    V164,
+    V165,
+    V166,
+    V167,
+    V168,
+    V169,
+    V170,
+    V171,
+    V172,
+    V173,
+    V174,
+    V175,
+    V176,
+    V177,
+    V178,
+    V179,
+    V180,
+    V181,
+    V182,
+    V183,
+    V184,
+    V185,
+    V186,
+    V187,
+    V188,
+    V189,
+    V190,
+    V191,
+    V192,
+    V193,
+    V194,
+    V195,
+    V196,
+    V197,
+    V198,
+    V199,
+    V200,
+}
+
+const _: () = assert!(std::intrinsics::discriminant_value(&Tricky::V100) == 100);
+
+// CHECK-LABEL: define noundef{{( range\(i8 [0-9]+, [0-9]+\))?}} i8 @discriminant6(i8 noundef %e)
+// CHECK-NEXT: start:
+// CHECK-NEXT: %[[REL_VAR:.+]] = add i8 %e, -66
+// CHECK-NEXT: %[[IS_NICHE:.+]] = icmp ult i8 %[[REL_VAR]], -56
+// CHECK-NEXT: %[[TAGGED_DISCR:.+]] = add i8 %e, -65
+// CHECK-NEXT: %[[DISCR:.+]] = select i1 %[[IS_NICHE]], i8 %[[TAGGED_DISCR]], i8 0
+// CHECK-NEXT: ret i8 %[[DISCR]]
+#[no_mangle]
+pub fn discriminant6(e: Tricky) -> u8 {
+    std::intrinsics::discriminant_value(&e) as _
+}
+
+// Case from <https://github.com/rust-lang/rust/issues/104519>,
+// where sign-extension is important.
+
+pub enum OpenResult {
+    Ok(()),
+    Err(()),
+    TransportErr(TransportErr),
+}
+
+#[repr(i32)]
+pub enum TransportErr {
+    UnknownMethod = -2,
+}
+
+#[no_mangle]
+pub fn match7(result: OpenResult) -> u8 {
+    // CHECK-LABEL: define noundef{{( range\(i8 [0-9]+, [0-9]+\))?}} i8 @match7(i32{{.+}}%result)
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: %[[NOT_OK:.+]] = icmp ne i32 %result, -1
+    // CHECK-NEXT: %[[RET:.+]] = zext i1 %[[NOT_OK]] to i8
+    // CHECK-NEXT: ret i8 %[[RET]]
+    match result {
+        OpenResult::Ok(()) => 0,
+        _ => 1,
+    }
+}