Auto merge of #59520 - JohnTitor:add-assert, r=eddyb

rustc_codegen_llvm: support 128-bit discriminants in debuginfo.

CC: #59509

> Alternatively, if LLVM and DWARF support it, we should encode the 128-bit discriminant

If we should fix like this issue comment, I'll do.

r? @eddyb

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -993,7 +993,7 @@ struct MemberDescription<'ll> {
     size: Size,
     align: Align,
     flags: DIFlags,
-    discriminant: Option<u64>,
+    discriminant: Option<u128>,
 }
 
 // A factory for MemberDescriptions. It produces a list of member descriptions
@@ -1351,7 +1351,7 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
                         flags: DIFlags::FlagZero,
                         discriminant: Some(self.layout.ty.ty_adt_def().unwrap()
                                            .discriminant_for_variant(cx.tcx, i)
-                                           .val as u64),
+                                           .val),
                     }
                 }).collect()
             }
@@ -1450,12 +1450,7 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
                             let value = (i.as_u32() as u128)
                                 .wrapping_sub(niche_variants.start().as_u32() as u128)
                                 .wrapping_add(niche_start);
-                            let value = truncate(value, discr.value.size(cx));
-                            // NOTE(eddyb) do *NOT* remove this assert, until
-                            // we pass the full 128-bit value to LLVM, otherwise
-                            // truncation will be silent and remain undetected.
-                            assert_eq!(value as u64 as u128, value);
-                            Some(value as u64)
+                            Some(truncate(value, discr.value.size(cx)))
                         };
 
                         MemberDescription {
@@ -1928,7 +1923,8 @@ fn set_members_of_composite_type(cx: &CodegenCx<'ll, 'tcx>,
                     member_description.offset.bits(),
                     match member_description.discriminant {
                         None => None,
-                        Some(value) => Some(cx.const_u64(value)),
+                        Some(value) =>
+                            Some(cx.const_uint_big(cx.type_i128(), value)),
                     },
                     member_description.flags,
                     member_description.type_metadata))

src/test/codegen/repr-u128.rs

@@ -0,0 +1,20 @@
+// ignore-windows
+// ignore-tidy-linelength
+//min-system-llvm-version 8.0
+
+//compile-flags: -g -C no-prepopulate-passes
+#![feature(repr128)]
+
+#[repr(u128)]
+pub enum Foo {
+    Lo,
+    Hi = 1 << 64,
+    Bar = 18_446_745_000_000_000_123,
+}
+
+// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "None",{{.*}}extraData:18446745000000000124
+pub fn foo() -> Option<Foo> {
+    None
+}
+
+fn main() {}

src/test/debuginfo/repr-u128.rs

@@ -0,0 +1,34 @@
+// ignore-windows
+// ignore-tidy-linelength
+//min-system-llvm-version 8.0
+
+//compile-flags: -g -C no-prepopulate-passes
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command: run
+
+// gdb-command:print vals
+// gdbg-check:$1 = (Some(Foo::Lo), None::<Foo>)
+// gdbr-check:$1 = repr_u128::Foo::(std::option::Option<Foo>, std::option::Option<Foo>)
+
+// === LLDB TESTS ==================================================================================
+
+// lldb-command:run
+
+// lldb-command:print vals
+// lldbg-check:[...]$0 = (Some(Foo::Lo), None::<Foo>)
+// lldbr-check:(repr_u128::Foo) vals = repr_u128::Foo::(std::option::Option<Foo>, std::option::Option<Foo>)
+
+#![feature(repr128)]
+
+#[repr(u128)]
+pub enum Foo {
+    Lo,
+    Hi = 1 << 64,
+    Bar = 18_446_745_000_000_000_123,
+}
+
+fn main() {
+    let vals = (Some(Foo::Lo), None::<Foo>);
+}