DebugInfo: Permit DW_TAG_structure_type, DW_TAG_member, DW_TAG_typedef tags with empty file names.

[pcc]

Summary

Some languages, such as Go, have pre-defined structure types (e.g. "string"
is essentially a pointer/length pair) or pre-defined "typedef" types
(e.g. "error" is essentially a typedef for a specific interface type).
Such types do not have associated source location, so a Go frontend would
be correct not to associate a file name with such types.

This change relaxes the DIType verifier to permit unlocated types with
these tags.

[dblaikie]

Some IR test cases might be nice to have here, to avoid regressing this
functionality.

[pcc]

• Add test case

[dblaikie]

test/DebugInfo/verifier.ll

4 ↗

(On Diff #22599)

"this test doesn't crash" is generally not ideal, prefer to test the desired output.

Use llc rather than opt, and ensure that the tags are emitted without file info as desired?

[pcc]

• Replace with an llc test

[probinson]

test/DebugInfo/missing-file-line.ll

1

Generating an object file and going through llvm-dwarfdump means you need
REQUIRES: object-emission
Also, as the test is now architecture-dependent, it needs to go in the DebugInfo/X86 directory.

16

These checks verify that you accept metadata with no source location; however I think it doesn't verify that what comes back out has no source location?

[pcc]

• Move test to DebugInfo/X86. Test that the entities have no file/line attrs. Add REQUIRES: object-emission

[probinson]

LGTM with the DW_TAG|NULL chang, and thanks for tolerating the pickiness about debug-info tests!

test/DebugInfo/X86/missing-file-line.ll

22 ↗

(On Diff #22625)

I see why this works, but we usually check DW_TAG|NULL to constrain the range to a single DIE. Ditto for the other two places.

[dblaikie]

test/DebugInfo/X86/missing-file-line.ll

3 ↗

(On Diff #22625)

Ideally just pipe dwarfdump's output straight to FileCheck without the intermediate %t - then just use a single set of CHECK (rather than 3 separate CHECK prefixes) lines for the tests.

[pcc]

test/DebugInfo/X86/missing-file-line.ll

3 ↗

(On Diff #22625)

Previously I used CHECK-DAG, but I couldn't see a way to do the CHECK-NOT checks within a single run of FileCheck while keeping them order independent.

22 ↗

(On Diff #22625)

Done

[probinson]

test/DebugInfo/X86/missing-file-line.ll

3 ↗

(On Diff #22625)

That would hard-code an order for the three DIEs, which is probably okay for the structure/member but I'm not so sure about the typedef.

lib/IR/DebugInfo.cpp

if (getFilename().empty()) {
     if (Tag != dwarf::DW_TAG_const_type && Tag != dwarf::DW_TAG_volatile_type &&
         Tag != dwarf::DW_TAG_pointer_type &&
         Tag != dwarf::DW_TAG_ptr_to_member_type &&
         Tag != dwarf::DW_TAG_reference_type &&
         Tag != dwarf::DW_TAG_rvalue_reference_type &&
         Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_array_type &&
         Tag != dwarf::DW_TAG_enumeration_type &&
         Tag != dwarf::DW_TAG_subroutine_type &&
-        Tag != dwarf::DW_TAG_inheritance && Tag != dwarf::DW_TAG_friend)
+        Tag != dwarf::DW_TAG_inheritance && Tag != dwarf::DW_TAG_friend &&
+        Tag != dwarf::DW_TAG_structure_type && Tag != dwarf::DW_TAG_member &&
+        Tag != dwarf::DW_TAG_typedef)
       return false;
   }
 
   if (isCompositeType())
     return DICompositeType(DbgNode).Verify();
   if (isDerivedType())
     return DIDerivedType(DbgNode).Verify();
   return false;

test/DebugInfo/missing-file-line.ll

+; RUN: llc -mtriple=x86_64-linux-gnu -filetype=obj %s -o - | llvm-dwarfdump -debug-dump=all - | FileCheck %s
+
+; Test that we accept and generate DWARF entities for DW_TAG_structure_type,
+; DW_TAG_member and DW_TAG_typedef with no source location. These can come up
+; in some languages with predefined types.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.S = type { %struct.S* }
+
+define void @f() {
+  %x = alloca %struct.S, align 8
+  ; CHECK-DAG: DW_TAG_typedef
+  ; CHECK-DAG: DW_TAG_structure_type
+  ; CHECK-DAG: DW_TAG_member
+  call void @llvm.dbg.declare(metadata %struct.S* %x, metadata !10, metadata !16), !dbg !17
+  ret void, !dbg !18
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = !MDCompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !MDFile(filename: "file.c", directory: "/dir")
+!2 = !{}
+!3 = !{!4}
+!4 = !MDSubprogram(name: "f", scope: !1, file: !1, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: false, function: void ()* @f, variables: !2)
+!5 = !MDSubroutineType(types: !6)
+!6 = !{null}
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang"}
+!10 = !MDLocalVariable(tag: DW_TAG_auto_variable, name: "x", scope: !4, file: !1, line: 8, type: !11)
+!11 = !MDDerivedType(tag: DW_TAG_typedef, name: "SS", baseType: !12)
+!12 = !MDCompositeType(tag: DW_TAG_structure_type, name: "S", size: 64, align: 64, elements: !13)
+!13 = !{!14}
+!14 = !MDDerivedType(tag: DW_TAG_member, name: "s", scope: !12, baseType: !15, size: 64, align: 64)
+!15 = !MDDerivedType(tag: DW_TAG_pointer_type, baseType: !12, size: 64, align: 64)
+!16 = !MDExpression()
+!17 = !MDLocation(line: 8, column: 6, scope: !4)
+!18 = !MDLocation(line: 9, column: 1, scope: !4)