Rollup merge of rust-lang#137643 - beetrees:repr128-dwarf-variant-test, r=jieyouxu

Add DWARF test case for non-C-like `repr128` enums

LLVM 20 fixes DWARF debuginfo for non-C-like 128-bit enums: this PR adds a test case to the `repr128-dwarf` test to ensure that LLVM doesn't regress in the future.

Tracking issue: rust-lang#56071

Author: compiler-errors

tests/run-make/repr128-dwarf/main.rs

@@ -19,8 +19,33 @@ pub enum I128Enum {
     I128D = i128::MAX.to_le(),
 }
 
+#[cfg(not(old_llvm))]
+#[repr(u128)]
+pub enum U128VariantEnum {
+    VariantU128A(u8) = 0_u128.to_le(),
+    VariantU128B = 1_u128.to_le(),
+    VariantU128C = (u64::MAX as u128 + 1).to_le(),
+    VariantU128D = u128::MAX.to_le(),
+}
+
+#[cfg(not(old_llvm))]
+#[repr(i128)]
+pub enum I128VariantEnum {
+    VariantI128A(u8) = 0_i128.to_le(),
+    VariantI128B = (-1_i128).to_le(),
+    VariantI128C = i128::MIN.to_le(),
+    VariantI128D = i128::MAX.to_le(),
+}
+
 pub fn f(_: U128Enum, _: I128Enum) {}
 
+#[cfg(not(old_llvm))]
+pub fn g(_: U128VariantEnum, _: I128VariantEnum) {}
+
 fn main() {
     f(U128Enum::U128A, I128Enum::I128A);
+    #[cfg(not(old_llvm))]
+    {
+        g(U128VariantEnum::VariantU128A(1), I128VariantEnum::VariantI128A(2));
+    }
 }

tests/run-make/repr128-dwarf/rmake.rs

@@ -5,13 +5,32 @@ use std::collections::HashMap;
 use std::path::PathBuf;
 use std::rc::Rc;
 
+use gimli::read::DebuggingInformationEntry;
 use gimli::{AttributeValue, EndianRcSlice, Reader, RunTimeEndian};
 use object::{Object, ObjectSection};
 use run_make_support::{gimli, object, rfs, rustc};
 
 fn main() {
+    // Before LLVM 20, 128-bit enums with variants didn't emit debuginfo correctly.
+    // This check can be removed once Rust no longer supports LLVM 18 and 19.
+    let llvm_version = rustc()
+        .verbose()
+        .arg("--version")
+        .run()
+        .stdout_utf8()
+        .lines()
+        .filter_map(|line| line.strip_prefix("LLVM version: "))
+        .map(|version| version.split(".").next().unwrap().parse::<u32>().unwrap())
+        .next()
+        .unwrap();
+    let is_old_llvm = llvm_version < 20;
+
     let output = PathBuf::from("repr128");
-    rustc().input("main.rs").output(&output).arg("-Cdebuginfo=2").run();
+    let mut rustc = rustc();
+    if is_old_llvm {
+        rustc.cfg("old_llvm");
+    }
+    rustc.input("main.rs").output(&output).arg("-Cdebuginfo=2").run();
     // Mach-O uses packed debug info
     let dsym_location = output
         .with_extension("dSYM")
@@ -29,7 +48,8 @@ fn main() {
     })
     .unwrap();
     let mut iter = dwarf.units();
-    let mut still_to_find = HashMap::from([
+
+    let mut enumerators_to_find = HashMap::from([
         ("U128A", 0_u128),
         ("U128B", 1_u128),
         ("U128C", u64::MAX as u128 + 1),
@@ -39,35 +59,88 @@ fn main() {
         ("I128C", i128::MIN as u128),
         ("I128D", i128::MAX as u128),
     ]);
+    let mut variants_to_find = HashMap::from([
+        ("VariantU128A", 0_u128),
+        ("VariantU128B", 1_u128),
+        ("VariantU128C", u64::MAX as u128 + 1),
+        ("VariantU128D", u128::MAX),
+        ("VariantI128A", 0_i128 as u128),
+        ("VariantI128B", (-1_i128) as u128),
+        ("VariantI128C", i128::MIN as u128),
+        ("VariantI128D", i128::MAX as u128),
+    ]);
+
     while let Some(header) = iter.next().unwrap() {
         let unit = dwarf.unit(header).unwrap();
         let mut cursor = unit.entries();
+
+        let get_name = |entry: &DebuggingInformationEntry<'_, '_, _>| {
+            let name = dwarf
+                .attr_string(
+                    &unit,
+                    entry.attr(gimli::constants::DW_AT_name).unwrap().unwrap().value(),
+                )
+                .unwrap();
+            name.to_string().unwrap().to_string()
+        };
+
         while let Some((_, entry)) = cursor.next_dfs().unwrap() {
-            if entry.tag() == gimli::constants::DW_TAG_enumerator {
-                let name = dwarf
-                    .attr_string(
-                        &unit,
-                        entry.attr(gimli::constants::DW_AT_name).unwrap().unwrap().value(),
-                    )
-                    .unwrap();
-                let name = name.to_string().unwrap();
-                if let Some(expected) = still_to_find.remove(name.as_ref()) {
-                    match entry.attr(gimli::constants::DW_AT_const_value).unwrap().unwrap().value()
+            match entry.tag() {
+                gimli::constants::DW_TAG_variant if !is_old_llvm => {
+                    let value = match entry
+                        .attr(gimli::constants::DW_AT_discr_value)
+                        .unwrap()
+                        .unwrap()
+                        .value()
                     {
-                        AttributeValue::Block(value) => {
-                            assert_eq!(
-                                value.to_slice().unwrap(),
-                                expected.to_le_bytes().as_slice(),
-                                "{name}"
-                            );
+                        AttributeValue::Block(value) => value.to_slice().unwrap().to_vec(),
+                        value => panic!("unexpected DW_AT_discr_value of {value:?}"),
+                    };
+                    // The `DW_TAG_member` that is a child of `DW_TAG_variant` will contain the
+                    // variant's name.
+                    let Some((1, child_entry)) = cursor.next_dfs().unwrap() else {
+                        panic!("Missing child of DW_TAG_variant");
+                    };
+                    assert_eq!(child_entry.tag(), gimli::constants::DW_TAG_member);
+                    let name = get_name(child_entry);
+                    if let Some(expected) = variants_to_find.remove(name.as_str()) {
+                        // This test uses LE byte order is used for consistent values across
+                        // architectures.
+                        assert_eq!(value.as_slice(), expected.to_le_bytes().as_slice(), "{name}");
+                    }
+                }
+
+                gimli::constants::DW_TAG_enumerator => {
+                    let name = get_name(entry);
+                    if let Some(expected) = enumerators_to_find.remove(name.as_str()) {
+                        match entry
+                            .attr(gimli::constants::DW_AT_const_value)
+                            .unwrap()
+                            .unwrap()
+                            .value()
+                        {
+                            AttributeValue::Block(value) => {
+                                // This test uses LE byte order is used for consistent values across
+                                // architectures.
+                                assert_eq!(
+                                    value.to_slice().unwrap(),
+                                    expected.to_le_bytes().as_slice(),
+                                    "{name}"
+                                );
+                            }
+                            value => panic!("{name}: unexpected DW_AT_const_value of {value:?}"),
                         }
-                        value => panic!("{name}: unexpected DW_AT_const_value of {value:?}"),
                     }
                 }
+
+                _ => {}
             }
         }
     }
-    if !still_to_find.is_empty() {
-        panic!("Didn't find debug entries for {still_to_find:?}");
+    if !enumerators_to_find.is_empty() {
+        panic!("Didn't find debug enumerator entries for {enumerators_to_find:?}");
+    }
+    if !is_old_llvm && !variants_to_find.is_empty() {
+        panic!("Didn't find debug variant entries for {variants_to_find:?}");
     }
 }