forked from OSchip/llvm-project
Let replaceVTableHolder accept any type.
In Rust, a trait can be implemented for any type, and if a trait object pointer is used for the type, then a virtual table will be emitted for that trait/type combination. We would like debuggers to be able to inspect trait objects, which requires finding the concrete type associated with a given vtable. This patch changes LLVM so that any type can be passed to replaceVTableHolder. This allows the Rust compiler to emit the needed debug info -- associating a vtable with the concrete type for which it was emitted. This is a DWARF extension: DWARF only specifies the meaning of DW_AT_containing_type in one specific situation. This style of DWARF extension is routine, though, and LLVM already has one such case for DW_AT_containing_type. Patch by Tom Tromey! Differential Revision: https://reviews.llvm.org/D39503 llvm-svn: 317730
This commit is contained in:
Adrian Prantl
parent
2c74fe977d
commit
a8e56458e6
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@ -757,12 +757,12 @@ namespace llvm {
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const DILocation *DL,
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Instruction *InsertBefore);
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/// Replace the vtable holder in the given composite type.
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/// Replace the vtable holder in the given type.
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///
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/// If this creates a self reference, it may orphan some unresolved cycles
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/// in the operands of \c T, so \a DIBuilder needs to track that.
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void replaceVTableHolder(DICompositeType *&T,
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DICompositeType *VTableHolder);
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DIType *VTableHolder);
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/// Replace arrays on a composite type.
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///
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@ -960,8 +960,9 @@ void DwarfUnit::constructTypeDIE(DIE &Buffer, const DICompositeType *CTy) {
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// This is outside the DWARF spec, but GDB expects a DW_AT_containing_type
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// inside C++ composite types to point to the base class with the vtable.
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if (auto *ContainingType =
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dyn_cast_or_null<DICompositeType>(resolve(CTy->getVTableHolder())))
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// Rust uses DW_AT_containing_type to link a vtable to the type
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// for which it was created.
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if (auto *ContainingType = resolve(CTy->getVTableHolder()))
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addDIEEntry(Buffer, dwarf::DW_AT_containing_type,
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*getOrCreateTypeDIE(ContainingType));
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@ -874,7 +874,7 @@ Instruction *DIBuilder::insertDbgValueIntrinsic(
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}
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void DIBuilder::replaceVTableHolder(DICompositeType *&T,
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DICompositeType *VTableHolder) {
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DIType *VTableHolder) {
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{
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TypedTrackingMDRef<DICompositeType> N(T);
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N->replaceVTableHolder(VTableHolder);
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@ -0,0 +1,125 @@
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; REQUIRES: object-emission
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; RUN: %llc_dwarf -O0 -filetype=obj < %s > %t
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; RUN: llvm-dwarfdump -v -debug-info %t | FileCheck %s
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; Check that any type can have a vtable holder.
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; CHECK: [[SP:.*]]: DW_TAG_structure_type
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; CHECK-NOT: TAG
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; CHECK: DW_AT_containing_type [DW_FORM_ref4]
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; CHECK: DW_AT_name [DW_FORM_strp] {{.*}}= "vtable")
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; This was compiled using
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; rustc -g --emit=llvm-ir t2.rs
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; ... and then edited by hand, because rustc is using a somewhat older llvm.
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;
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; t2.rs is:
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;
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; // trait object test case
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;
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; pub trait T {
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; }
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;
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; impl T for f64 {
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; }
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;
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; pub fn main() {
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; let tu = &23.0f64 as &T;
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; }
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; t2.rs ends here ^^^
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; ModuleID = 't2.cgu-0.rs'
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source_filename = "t2.cgu-0.rs"
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@ref.0 = internal unnamed_addr constant double 2.300000e+01, align 8
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@vtable.1 = internal unnamed_addr constant { void (double*)*, i64, i64 } { void (double*)* @_ZN4core3ptr13drop_in_place17h2818a933abde117eE, i64 8, i64 8 }, align 8, !dbg !0
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@__rustc_debug_gdb_scripts_section__ = linkonce_odr unnamed_addr constant [34 x i8] c"\01gdb_load_rust_pretty_printers.py\00", section ".debug_gdb_scripts", align 1
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; core::ptr::drop_in_place
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; Function Attrs: uwtable
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define internal void @_ZN4core3ptr13drop_in_place17h2818a933abde117eE(double*) unnamed_addr #0 !dbg !11 {
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start:
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%arg0 = alloca double*
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store double* %0, double** %arg0
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call void @llvm.dbg.declare(metadata double** %arg0, metadata !20, metadata !22), !dbg !23
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ret void, !dbg !24
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}
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; t2::main
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; Function Attrs: uwtable
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define internal void @_ZN2t24main17h6319e6ac7de3a097E() unnamed_addr #0 !dbg !25 {
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start:
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%tu = alloca { i8*, void (i8*)** }
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call void @llvm.dbg.declare(metadata { i8*, void (i8*)** }* %tu, metadata !29, metadata !22), !dbg !37
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%0 = getelementptr inbounds { i8*, void (i8*)** }, { i8*, void (i8*)** }* %tu, i32 0, i32 0, !dbg !37
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store i8* bitcast (double* @ref.0 to i8*), i8** %0, !dbg !37
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%1 = getelementptr inbounds { i8*, void (i8*)** }, { i8*, void (i8*)** }* %tu, i32 0, i32 1, !dbg !37
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store void (i8*)** bitcast ({ void (double*)*, i64, i64 }* @vtable.1 to void (i8*)**), void (i8*)*** %1, !dbg !37
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ret void, !dbg !38
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}
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; Function Attrs: nounwind readnone
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declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
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define i32 @main(i32, i8**) unnamed_addr #2 {
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top:
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%2 = load volatile i8, i8* getelementptr inbounds ([34 x i8], [34 x i8]* @__rustc_debug_gdb_scripts_section__, i32 0, i32 0), align 1
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%3 = sext i32 %0 to i64
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; call std::rt::lang_start
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%4 = call i64 @_ZN3std2rt10lang_start17h2626caf1112a00beE(void ()* @_ZN2t24main17h6319e6ac7de3a097E, i64 %3, i8** %1)
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%5 = trunc i64 %4 to i32
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ret i32 %5
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}
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; std::rt::lang_start
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declare i64 @_ZN3std2rt10lang_start17h2626caf1112a00beE(void ()*, i64, i8**) unnamed_addr #3
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attributes #0 = { uwtable "no-frame-pointer-elim"="true" "probe-stack"="__rust_probestack" }
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attributes #1 = { nounwind readnone }
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attributes #2 = { "no-frame-pointer-elim"="true" }
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attributes #3 = { "no-frame-pointer-elim"="true" "probe-stack"="__rust_probestack" }
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!llvm.module.flags = !{!6, !7}
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!llvm.dbg.cu = !{!8}
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!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
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!1 = distinct !DIGlobalVariable(name: "vtable", scope: null, file: !2, type: !3, isLocal: true, isDefinition: true)
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!2 = !DIFile(filename: "<unknown>", directory: "")
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!3 = !DICompositeType(tag: DW_TAG_structure_type, name: "vtable", file: !2, size: 64, align: 64, flags: DIFlagArtificial, elements: !4, vtableHolder: !5, identifier: "vtable")
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!4 = !{}
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!5 = !DIBasicType(name: "f64", size: 64, encoding: DW_ATE_float)
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!6 = !{i32 1, !"PIE Level", i32 2}
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!7 = !{i32 2, !"Debug Info Version", i32 3}
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!8 = distinct !DICompileUnit(language: DW_LANG_Rust, file: !9, producer: "clang LLVM (rustc version 1.22.0-dev)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !10)
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!9 = !DIFile(filename: "t2.rs", directory: "/home/tromey/Rust")
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!10 = !{!0}
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!11 = distinct !DISubprogram(name: "drop_in_place<f64>", linkageName: "_ZN4core3ptr18drop_in_place<f64>E", scope: !13, file: !12, line: 59, type: !15, isLocal: false, isDefinition: true, scopeLine: 59, flags: DIFlagPrototyped, isOptimized: false, unit: !8, templateParams: !18, variables: !4)
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!12 = !DIFile(filename: "/home/tromey/Rust/rust/src/libcore/ptr.rs", directory: "")
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!13 = !DINamespace(name: "ptr", scope: !14)
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!14 = !DINamespace(name: "core", scope: null)
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!15 = !DISubroutineType(types: !16)
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!16 = !{null, !17}
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!17 = !DIDerivedType(tag: DW_TAG_pointer_type, name: "*mut f64", baseType: !5, size: 64, align: 64)
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!18 = !{!19}
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!19 = !DITemplateTypeParameter(name: "T", type: !5)
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!20 = !DILocalVariable(arg: 1, scope: !11, file: !21, line: 1, type: !17)
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!21 = !DIFile(filename: "t2.rs", directory: "")
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!22 = !DIExpression()
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!23 = !DILocation(line: 1, scope: !11)
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!24 = !DILocation(line: 59, scope: !11)
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!25 = distinct !DISubprogram(name: "main", linkageName: "_ZN2t24mainE", scope: !26, file: !9, line: 9, type: !27, isLocal: true, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped | DIFlagMainSubprogram, isOptimized: false, unit: !8, templateParams: !4, variables: !4)
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!26 = !DINamespace(name: "t2", scope: null)
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!27 = !DISubroutineType(types: !28)
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!28 = !{null}
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!29 = !DILocalVariable(name: "tu", scope: !30, file: !9, line: 10, type: !31, align: 8)
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!30 = distinct !DILexicalBlock(scope: !25, file: !9, line: 10, column: 4)
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!31 = !DICompositeType(tag: DW_TAG_structure_type, name: "&T", scope: !26, file: !2, size: 128, align: 64, elements: !32, identifier: "b9f642b757d8ad3984c1e721e3ce6016d14d9322")
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!32 = !{!33, !36}
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!33 = !DIDerivedType(tag: DW_TAG_member, name: "pointer", scope: !31, file: !2, baseType: !34, size: 64, align: 64, flags: DIFlagArtificial)
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!34 = !DIDerivedType(tag: DW_TAG_pointer_type, name: "*const u8", baseType: !35, size: 64, align: 64)
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!35 = !DIBasicType(name: "u8", size: 8, encoding: DW_ATE_unsigned)
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!36 = !DIDerivedType(tag: DW_TAG_member, name: "vtable", scope: !31, file: !2, baseType: !34, size: 64, align: 64, offset: 64, flags: DIFlagArtificial)
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!37 = !DILocation(line: 10, scope: !30)
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!38 = !DILocation(line: 11, scope: !25)
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@ -0,0 +1,39 @@
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; REQUIRES: object-emission
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; RUN: %llc_dwarf -O0 -filetype=obj < %s > %t
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; RUN: llvm-dwarfdump -v -debug-info %t | FileCheck %s
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; Check that any type can have a vtable holder.
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; CHECK: [[SP:.*]]: DW_TAG_structure_type
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; CHECK-NOT: TAG
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; CHECK: DW_AT_containing_type [DW_FORM_ref4]
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; CHECK: DW_AT_name [DW_FORM_strp] {{.*}}= "vtable")
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; The code doesn't actually matter.
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define i32 @main() #0 !dbg !4 {
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entry:
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%retval = alloca i32, align 4
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store i32 0, i32* %retval
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ret i32 0, !dbg !10
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}
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attributes #0 = { nounwind uwtable }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!9, !11}
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!0 = distinct !DICompileUnit(language: DW_LANG_Rust, producer: "clang version 3.4 (trunk 185475)", isOptimized: false, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !15, imports: !2)
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!1 = !DIFile(filename: "CodeGen/dwarf-version.c", directory: "test")
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!2 = !{}
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!4 = distinct !DISubprogram(name: "main", line: 6, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped | DIFlagMainSubprogram, isOptimized: false, unit: !0, scopeLine: 6, file: !1, scope: !5, type: !6, variables: !2)
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!5 = !DIFile(filename: "CodeGen/dwarf-version.c", directory: "test")
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!6 = !DISubroutineType(types: !7)
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!7 = !{!8}
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!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
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!9 = !{i32 2, !"Dwarf Version", i32 4}
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!10 = !DILocation(line: 7, scope: !4)
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!11 = !{i32 1, !"Debug Info Version", i32 3}
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!12 = !DICompositeType(tag: DW_TAG_structure_type, name: "vtable", size: 8, align: 8, elements: !2, identifier: "vtable", vtableHolder: !8)
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!13 = !DIGlobalVariableExpression(var: !14, expr: !DIExpression())
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!14 = !DIGlobalVariable(name: "vtable", linkageName: "vtable", scope: null, file: !1, line: 1, type: !12, isLocal: true, isDefinition: true)
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!15 = !{!13}
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@ -1314,6 +1314,11 @@ TEST_F(DICompositeTypeTest, replaceOperands) {
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EXPECT_EQ(nullptr, N->getVTableHolder());
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N->replaceVTableHolder(VTableHolder);
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EXPECT_EQ(VTableHolder, N->getVTableHolder());
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// As an extension, the containing type can be anything. This is
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// used by Rust to associate vtables with their concrete type.
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DIType *BasicType = getBasicType("basic");
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N->replaceVTableHolder(BasicType);
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EXPECT_EQ(BasicType, N->getVTableHolder());
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N->replaceVTableHolder(nullptr);
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EXPECT_EQ(nullptr, N->getVTableHolder());
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