[llvm] Allow DIDerivedType as a bound in DISubrangeType (PR #165880)

[Tom Tromey via llvm-commits]

================
@@ -0,0 +1,88 @@
+; RUN: llvm-as < %s | llvm-dis | llc -mtriple=x86_64 -O0 -filetype=obj -o - | llvm-dwarfdump -v -debug-info - | FileCheck %s
+
+; A test to verify the use of a DIDerivedType as a bound of a
+; DISubrangeType.
+
+; CHECK: DW_TAG_array_type
+; CHECK-NEXT: DW_AT_type [DW_FORM_ref4] {{.*}}
+; CHECK: DW_TAG_subrange_type {{.*}}
+; CHECK-NEXT: DW_AT_type [DW_FORM_ref4] {{.*}}
+; CHECK-NEXT: DW_AT_upper_bound [DW_FORM_ref4] {{.*}}
+
+; ModuleID = 'vla.ads'
+source_filename = "vla.ads"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%vla__array_type_FP = type { ptr, ptr }
+%vla__record_type_I = type <{ i32 }>
+
+ at vla_E = dso_local global i16 0, align 2, !dbg !0
+
+; Function Attrs: inlinehint
+define dso_local void @vla__array_typeIP(%vla__array_type_FP %_init) #0 !dbg !10 {
+entry:
+  %0 = extractvalue %vla__array_type_FP %_init, 1, !dbg !15
+  %1 = call ptr @llvm.invariant.start.p0(i64 8, ptr %0), !dbg !15
+  ret void, !dbg !15
+}
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare ptr @llvm.invariant.start.p0(i64 immarg, ptr nocapture) #1
+
+; Function Attrs: inlinehint
+define dso_local void @vla__record_typeIP(ptr noalias nocapture nonnull %_init, i32 %l1) #0 !dbg !16 {
+entry:
+    #dbg_declare(ptr %_init, !31, !DIExpression(), !32)
+    #dbg_value(i32 %l1, !33, !DIExpression(), !34)
+  %0 = getelementptr inbounds %vla__record_type_I, ptr %_init, i32 0, i32 0, !dbg !32
+  store i32 %l1, ptr %0, align 4, !dbg !32, !tbaa !35
+  ret void, !dbg !32
+}
+
+attributes #0 = { inlinehint }
+attributes #1 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
+
+!llvm.module.flags = !{!6, !7, !8, !9}
+!llvm.dbg.cu = !{!2}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "vla_E", scope: !2, file: !3, line: 16, type: !5, isLocal: false, isDefinition: true, align: 16)
+!2 = distinct !DICompileUnit(language: DW_LANG_Ada95, file: !3, producer: "GNAT/LLVM", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false)
+!3 = !DIFile(filename: "vla.ads", directory: "")
+!4 = !{!0}
+!5 = !DIBasicType(name: "short_integer", size: 16, encoding: DW_ATE_signed)
+!6 = !{i32 8, !"PIC Level", i32 2}
+!7 = !{i32 7, !"PIE Level", i32 2}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 2, !"Dwarf Version", i32 4}
+!10 = distinct !DISubprogram(name: "vla__array_typeIP", scope: !3, file: !3, line: 17, type: !11, scopeLine: 17, spFlags: DISPFlagDefinition, unit: !2)
+!11 = !DISubroutineType(types: !12)
+!12 = !{null, !13}
+!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !14, size: 64, align: 64, dwarfAddressSpace: 0)
+!14 = !DIBasicType(tag: DW_TAG_unspecified_type, name: "vla__array_type")
+!15 = !DILocation(line: 17, column: 9, scope: !10)
+!16 = distinct !DISubprogram(name: "vla__record_typeIP", scope: !3, file: !3, line: 18, type: !17, scopeLine: 18, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !30)
+!17 = !DISubroutineType(types: !18)
+!18 = !{null, !19, !23}
+!19 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !20, size: 64, align: 64, dwarfAddressSpace: 0)
+!20 = !DICompositeType(tag: DW_TAG_structure_type, name: "vla__record_type", file: !3, line: 18, size: !DIExpression(DW_OP_push_object_address, DW_OP_deref_size, 4, DW_OP_constu, 32, DW_OP_mul, DW_OP_constu, 32, DW_OP_plus), align: 32, elements: !21, identifier: "vla__record_type")
+!21 = !{!22, !26}
+!22 = !DIDerivedType(tag: DW_TAG_member, name: "l1", file: !3, line: 18, baseType: !23)
+!23 = !DISubrangeType(name: "natural", file: !24, line: 1, size: 32, align: 32, baseType: !25, lowerBound: i64 0, upperBound: i64 2147483647)
+!24 = !DIFile(filename: "system.ads", directory: "/home/tromey/AdaCore/gnat-llvm/llvm-interface//lib/gnat-llvm/x86_64-unknown-linux-gnu/rts-native/adainclude/")
+!25 = !DIBasicType(name: "integer", size: 32, encoding: DW_ATE_signed)
+!26 = !DIDerivedType(tag: DW_TAG_member, name: "a1", file: !3, line: 19, baseType: !27, offset: 32)
+!27 = !DICompositeType(tag: DW_TAG_array_type, scope: !20, file: !3, line: 19, baseType: !25, align: 32, elements: !28)
+!28 = !{!29}
+!29 = !DISubrangeType(baseType: !25, lowerBound: i64 1, upperBound: !22)
+!30 = !{}
+!31 = !DILocalVariable(name: "_init", arg: 1, scope: !16, file: !3, line: 18, type: !20, flags: DIFlagArtificial)
+!32 = !DILocation(line: 18, column: 9, scope: !16)
+!33 = !DILocalVariable(name: "l1", arg: 2, scope: !16, file: !3, line: 18, type: !23, flags: DIFlagArtificial)
----------------
tromey wrote:

Offhand I am not sure why that is there.  This is more or less just the compiler output.  It's possible that maybe in this particular little test program that the bound is also in some variable, but in general this isn't the case and referring to a member of the enclosing record is the correct way.

https://github.com/llvm/llvm-project/pull/165880