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Christopher Di Bella f7cd39428e Add Destroy.SubobjectDestroy as a temporary replacement for Destroy.Op (#7773)
This change partially implements [PR #7362], which revises how objects
are destroyed. It is a partial implementation for two reasons:

1. This change moves `Destroy.Op`'s current behaviour into
`Destroy.SubobjectDestroy`, but it doesn't add support for objects with
non-trivial destruction.
2. `Destroy.SubobjectDestroy` is a workaround for `require impls
SubobjectDestroy`. We aren't able to use the latter until the dependents
add their requirements' implementations to their own witness tables.

[PR #7362]: https://github.com/carbon-language/carbon-lang/pulls/7362
2026-09-24 00:06:28 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/int.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/struct/empty.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/struct/empty.carbon
fn Run() -> i32 {
var x: {} = {};
var _: {} = x;
return 0;
}
// CHECK:STDOUT: ; ---
// CHECK:STDOUT: ; ModuleID = 'empty.carbon'
// CHECK:STDOUT: source_filename = "empty.carbon"
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define i32 @main() #0 !dbg !26 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %x.var = alloca {}, align 1, !dbg !29
// CHECK:STDOUT: %_.var = alloca {}, align 1, !dbg !31
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !29
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !31
// CHECK:STDOUT: call void @"_CSelfDestruct.cb8adced19392b99:core.Destroy.Core"(ptr %_.var), !dbg !31
// CHECK:STDOUT: call void @"_CSelfDestruct.cb8adced19392b99:core.Destroy.Core"(ptr %x.var), !dbg !29
// CHECK:STDOUT: ret i32 0, !dbg !34
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define weak_odr void @"_CSelfDestruct.cb8adced19392b99:core.Destroy.Core"(ptr %self) #0 !dbg !35 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !37
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #1
// CHECK:STDOUT:
// CHECK:STDOUT: ; uselistorder directives
// CHECK:STDOUT: uselistorder ptr @"_CSelfDestruct.cb8adced19392b99:core.Destroy.Core", { 1, 0 }
// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 1, 0 }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT: attributes #1 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.dbg.cu = !{!19}
// CHECK:STDOUT: !llvm.module.flags = !{!2, !3}
// CHECK:STDOUT:
// CHECK:STDOUT: !2 = !{i32 7, !"Dwarf Version", i32 5}
// CHECK:STDOUT: !3 = !{i32 2, !"Debug Info Version", i32 3}
// CHECK:STDOUT: !18 = !DIFile(filename: "empty.carbon", directory: "")
// CHECK:STDOUT: !19 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !18, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
// CHECK:STDOUT: !20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
// CHECK:STDOUT: !21 = !{!20}
// CHECK:STDOUT: !22 = !DISubroutineType(types: !21)
// CHECK:STDOUT: !23 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
// CHECK:STDOUT: !24 = !{null, !23}
// CHECK:STDOUT: !25 = !DISubroutineType(types: !24)
// CHECK:STDOUT: !26 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !18, line: 13, type: !22, spFlags: DISPFlagDefinition, unit: !19)
// CHECK:STDOUT: !29 = !DILocation(line: 14, column: 3, scope: !26)
// CHECK:STDOUT: !31 = !DILocation(line: 15, column: 3, scope: !26)
// CHECK:STDOUT: !34 = !DILocation(line: 16, column: 3, scope: !26)
// CHECK:STDOUT: !35 = distinct !DISubprogram(name: "SelfDestruct", linkageName: "_CSelfDestruct.cb8adced19392b99:core.Destroy.Core", scope: null, file: !18, line: 15, type: !25, spFlags: DISPFlagDefinition, unit: !19, retainedNodes: !38)
// CHECK:STDOUT: !36 = !DILocalVariable(arg: 1, scope: !35, type: !23)
// CHECK:STDOUT: !37 = !DILocation(line: 15, column: 3, scope: !35)
// CHECK:STDOUT: !38 = !{!36}
// CHECK:STDOUT: