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n Rust, an enum that carries data in the variants is, essentially, a discriminated union. Furthermore, the Rust compiler will perform space optimizations on such enums in some situations. Previously, DWARF for these constructs was emitted using a hack (a magic field name); but this approach stopped working when more space optimizations were added in https://github.com/rust-lang/rust/pull/45225. This patch changes LLVM to allow discriminated unions to be represented in DWARF. It adds createDiscriminatedUnionType and createDiscriminatedMemberType to DIBuilder and then arranges for this to be emitted using DWARF's DW_TAG_variant_part and DW_TAG_variant. Note that DWARF requires that a discriminated union be represented as a structure with a variant part. However, as Rust only needs to emit pure discriminated unions, this is what I chose to expose on DIBuilder. Patch by Tom Tromey! Differential Revision: https://reviews.llvm.org/D42082 llvm-svn: 324426
9 lines
400 B
LLVM
9 lines
400 B
LLVM
; RUN: not llvm-as -disable-output <%s 2>&1 | FileCheck %s
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!named = !{!0}
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!0 = !DICompositeType(tag: DW_TAG_structure_type, name: "A", size: 64, discriminator: !1)
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!1 = !DIDerivedType(tag: DW_TAG_member, scope: !0, baseType: !3, size: 64, align: 64, flags: DIFlagArtificial)
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!3 = !DIBasicType(name: "u64", size: 64, encoding: DW_ATE_unsigned)
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; CHECK: discriminator can only appear on variant part
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