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Fix DWARF generation for enums

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The DWARF generated for Rust enums was always somewhat unusual.
Rather than using DWARF constructs directly, it would emit magic field
names like "RUST$ENCODED$ENUM$0$Name" and "RUST$ENUM$DISR".  Since
PR #45225, though, even this has not worked -- the ad hoc scheme was
not updated to handle the wider variety of niche-filling layout
optimizations now available.

This patch changes the generated DWARF to use the standard tags meant
for this purpose; namely, DW_TAG_variant and DW_TAG_variant_part.

The patch to implement this went in to LLVM 7.  In order to work with
older versions of LLVM, and because LLVM doesn't do anything here for
PDB, the existing code is kept as a fallback mode.

Support for this DWARF is in the Rust lldb and in gdb 8.2.

Closes #32920
Closes #32924
Closes #52762
Closes #53153
This commit is contained in:
Tom Tromey 2017-11-29 14:42:25 -07:00
parent e8aef7cae1
commit 71ce4c3007
5 changed files with 494 additions and 147 deletions
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40
src/test/codegen/enum-debug.rs Normal file
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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// This test depends on a patch that was committed to upstream LLVM
// before 7.0, then backported to the Rust LLVM fork. It tests that
// optimized enum debug info accurately reflects the enum layout.
// ignore-tidy-linelength
// ignore-windows
// min-system-llvm-version 7.0
// compile-flags: -g -C no-prepopulate-passes
// CHECK-LABEL: @main
// CHECK: {{.*}}DICompositeType{{.*}}tag: DW_TAG_variant_part,{{.*}}discriminator:{{.*}}
// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "A",{{.*}}extraData:{{.*}}
// CHECK: {{.*}}DICompositeType{{.*}}tag: DW_TAG_structure_type,{{.*}}name: "A",{{.*}}
// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "B",{{.*}}extraData:{{.*}}
// CHECK: {{.*}}DICompositeType{{.*}}tag: DW_TAG_structure_type,{{.*}}name: "B",{{.*}}
// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "C",{{.*}}extraData:{{.*}}
// CHECK: {{.*}}DICompositeType{{.*}}tag: DW_TAG_structure_type,{{.*}}name: "C",{{.*}}
// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "D",{{.*}}
// CHECK: {{.*}}DICompositeType{{.*}}tag: DW_TAG_structure_type,{{.*}}name: "D",{{.*}}
#![allow(dead_code)]
#![allow(unused_variables)]
#![allow(unused_assignments)]
enum E { A, B, C, D(bool) }
pub fn main() {
let e = E::D(true);
}