[llvm] efbbca6 - [llvm][DebugInfo] Allow DIDerivedType as a bound in DISubrangeType (#165880)
via llvm-commits
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Wed Dec 3 16:38:18 PST 2025
Author: Tom Tromey
Date: 2025-12-04T09:38:14+09:00
New Revision: efbbca62d15271b07c54b22a0014339f350c857f
URL: https://github.com/llvm/llvm-project/commit/efbbca62d15271b07c54b22a0014339f350c857f
DIFF: https://github.com/llvm/llvm-project/commit/efbbca62d15271b07c54b22a0014339f350c857f.diff
LOG: [llvm][DebugInfo] Allow DIDerivedType as a bound in DISubrangeType (#165880)
Consider this Ada type:
```
type Array_Type is array (Natural range <>) of Integer;
type Record_Type (L1, L2 : Natural) is record
I1 : Integer;
A1 : Array_Type (1 .. L1);
I2 : Integer;
A2 : Array_Type (1 .. L2);
I3 : Integer;
end record;
```
Here, the array fields have lengths that depend on the discriminants of
the record type. However, in this case the array lengths cannot be
expressed as DWARF location expressions, with the issue being that "A2"
has a non-constant offset, but an expression involving
DW_OP_push_object_address will push the address of the field -- with no
way to find the location of "L2".
In a case like this, I believe the correct DWARF is to emit the array
ranges using a direct reference to the discriminant, like:
```
<3><1156>: Abbrev Number: 1 (DW_TAG_member)
<1157> DW_AT_name : l1
...
<3><1177>: Abbrev Number: 6 (DW_TAG_array_type)
<1178> DW_AT_name : (indirect string, offset: 0x1a0b): vla__record_type__T4b
<117c> DW_AT_type : <0x1287>
<1180> DW_AT_sibling : <0x118e>
<4><1184>: Abbrev Number: 7 (DW_TAG_subrange_type)
<1185> DW_AT_type : <0x1280>
<1189> DW_AT_upper_bound : <0x1156>
```
(FWIW this is what GCC has done for years.)
This patch makes this possible in LLVM, by letting a DISubrangeType
refer to a DIDerivedType. gnat-llvm can then arrange for the DIE
reference to be correct by setting the array type's scope to be the
record.
Added:
llvm/test/DebugInfo/X86/derived-in-subrange.ll
Modified:
llvm/include/llvm/IR/DebugInfoMetadata.h
llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
llvm/lib/IR/DebugInfoMetadata.cpp
llvm/lib/IR/Verifier.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index 6918b21d5b363..fbeb93f45985d 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -1520,7 +1520,9 @@ inline bool operator!=(DIDerivedType::PtrAuthData Lhs,
/// is also a DIType.
class DISubrangeType : public DIType {
public:
- typedef PointerUnion<ConstantInt *, DIVariable *, DIExpression *> BoundType;
+ typedef PointerUnion<ConstantInt *, DIVariable *, DIExpression *,
+ DIDerivedType *>
+ BoundType;
private:
friend class LLVMContextImpl;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index e1a231e02aeb2..330fe333a58cc 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1598,6 +1598,9 @@ void DwarfUnit::constructSubrangeDIE(DIE &DW_Subrange, const DISubrangeType *SR,
if (auto *BV = dyn_cast_if_present<DIVariable *>(Bound)) {
if (auto *VarDIE = getDIE(BV))
addDIEEntry(DW_Subrange, Attr, *VarDIE);
+ } else if (auto *DT = dyn_cast_if_present<DIDerivedType *>(Bound)) {
+ if (auto *DTDIE = getDIE(DT))
+ addDIEEntry(DW_Subrange, Attr, *DTDIE);
} else if (auto *BE = dyn_cast_if_present<DIExpression *>(Bound)) {
addBlock(DW_Subrange, Attr, BE);
} else if (auto *BI = dyn_cast_if_present<ConstantInt *>(Bound)) {
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 1a6a25e161803..79b512d09822b 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -839,7 +839,7 @@ DISubrangeType::convertRawToBound(Metadata *IN) const {
return BoundType();
assert(isa<ConstantAsMetadata>(IN) || isa<DIVariable>(IN) ||
- isa<DIExpression>(IN));
+ isa<DIExpression>(IN) || isa<DIDerivedType>(IN));
if (auto *MD = dyn_cast<ConstantAsMetadata>(IN))
return BoundType(cast<ConstantInt>(MD->getValue()));
@@ -850,6 +850,9 @@ DISubrangeType::convertRawToBound(Metadata *IN) const {
if (auto *MD = dyn_cast<DIExpression>(IN))
return BoundType(MD);
+ if (auto *DT = dyn_cast<DIDerivedType>(IN))
+ return BoundType(DT);
+
return BoundType();
}
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index a1e14d8f25bf7..147f8a64daaa5 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -1187,13 +1187,17 @@ void Verifier::visitDISubrangeType(const DISubrangeType &N) {
CheckDI(!BaseType || isType(BaseType), "BaseType must be a type");
auto *LBound = N.getRawLowerBound();
CheckDI(!LBound || isa<ConstantAsMetadata>(LBound) ||
- isa<DIVariable>(LBound) || isa<DIExpression>(LBound),
- "LowerBound must be signed constant or DIVariable or DIExpression",
+ isa<DIVariable>(LBound) || isa<DIExpression>(LBound) ||
+ isa<DIDerivedType>(LBound),
+ "LowerBound must be signed constant or DIVariable or DIExpression or "
+ "DIDerivedType",
&N);
auto *UBound = N.getRawUpperBound();
CheckDI(!UBound || isa<ConstantAsMetadata>(UBound) ||
- isa<DIVariable>(UBound) || isa<DIExpression>(UBound),
- "UpperBound must be signed constant or DIVariable or DIExpression",
+ isa<DIVariable>(UBound) || isa<DIExpression>(UBound) ||
+ isa<DIDerivedType>(UBound),
+ "UpperBound must be signed constant or DIVariable or DIExpression or "
+ "DIDerivedType",
&N);
auto *Stride = N.getRawStride();
CheckDI(!Stride || isa<ConstantAsMetadata>(Stride) ||
diff --git a/llvm/test/DebugInfo/X86/derived-in-subrange.ll b/llvm/test/DebugInfo/X86/derived-in-subrange.ll
new file mode 100644
index 0000000000000..fb4c1d4745feb
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/derived-in-subrange.ll
@@ -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)
+!34 = !DILocation(line: 18, column: 22, scope: !16)
+!35 = !{!36, !36, i64 0, i64 4}
+!36 = !{!37, i64 4, !"natural#T5"}
+!37 = !{!38, i64 4, !"natural#TN"}
+!38 = !{!39, i64 4, !"integerB#TN"}
+!39 = !{!"Ada Root"}
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