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Previously, we unconditionally set the bitwidth to 128-bits, the largest an discrimnator would possibly be. Then, LLVM would cut down the constant by chopping off leading zeroes before emitting the DWARF. LLVM only supported 64-bit descriminators, so this would also have occasionally resulted in truncated data (or an assert) if more than 64-bits were used. LLVM added support for 128-bit enumerators in llvm/llvm-project#125578 That patchset also trusts the constant to describe how wide the variant tag is. As a result, we went from emitting tags that looked like: DW_AT_discr_value (0xfe) (`form1`) to emitting tags that looked like: DW_AT_discr_value (<0x10> fe ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 ) This makes the `DW_AT_discr_value` encode at the bitwidth of the tag, which: 1. Is probably closer to our intentions in terms of describing the data. 2. Doesn't invoke the 128-bit support which may not be supported by all debuggers / downstream tools. 3. Will result in smaller debug information.
48 lines
1.2 KiB
Rust
48 lines
1.2 KiB
Rust
//! This tests that optimized enum debug info accurately reflects the enum layout.
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//! This is ignored for the fallback mode on MSVC due to problems with PDB.
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//!
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//@ compile-flags: -g -C no-prepopulate-passes
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//@ ignore-msvc
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//
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// CHECK: {{.*}}DICompositeType{{.*}}tag: DW_TAG_variant_part,{{.*}}size: 32,{{.*}}
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// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "Placeholder",{{.*}}extraData: i32 -1{{[,)].*}}
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// CHECK: {{.*}}DIDerivedType{{.*}}tag: DW_TAG_member,{{.*}}name: "Error",{{.*}}extraData: i32 0{{[,)].*}}
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#![feature(never_type)]
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#[derive(Copy, Clone)]
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pub struct Entity {
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private: std::num::NonZero<u32>,
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}
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#[derive(Copy, Clone, PartialEq, Eq)]
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pub struct Declaration;
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impl TypeFamily for Declaration {
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type Base = Base;
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type Placeholder = !;
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fn intern_base_data(_: BaseKind<Self>) {}
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}
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#[derive(Copy, Clone)]
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pub struct Base;
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pub trait TypeFamily: Copy + 'static {
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type Base: Copy;
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type Placeholder: Copy;
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fn intern_base_data(_: BaseKind<Self>);
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}
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#[derive(Copy, Clone)]
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pub enum BaseKind<F: TypeFamily> {
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Named(Entity),
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Placeholder(F::Placeholder),
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Error,
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}
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pub fn main() {
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let x = BaseKind::Error::<Declaration>;
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let y = 7;
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}
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