[cfe-dev] Storing auto as well as actual data type for sub program

[David Blaikie via cfe-dev]

Yep - given this source code:

struct foo {
  static auto f1();
};
auto foo::f1() {
  return 3;
}

The current LLVM IR generated is:
!7 = distinct !DISubprogram(name: "f1", linkageName: "_ZN3foo2f1Ev", scope:
!8, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped,
spFlags: DISPFlagDefinition, unit: !0, declaration: !12, retainedNodes: !2)
!8 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "foo",
file: !1, line: 1, size: 8, flags: DIFlagTypePassByValue, elements: !2,
identifier: "_ZTS3foo")
!9 = !DISubroutineType(types: !10)
!10 = !{!11}
!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!12 = !DISubprogram(name: "f1", linkageName: "_ZN3foo2f1Ev", scope: !8,
file: !1, line: 2, type: !9, scopeLine: 2, flags: DIFlagPrototyped |
DIFlagStaticMember, spFlags: 0)

But instead of that, if we're going to support using DW_AT_unspecified_type
for auto and emitting declarations of auto functions even if there's no
definition available (which, again, I don't think is super
important/necessary by any means), the DWARF should look like this:

!7 = distinct !DISubprogram(name: "f1", linkageName: "_ZN3foo2f1Ev", scope:
!8, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped,
spFlags: DISPFlagDefinition, unit: !0, declaration: !12, retainedNodes: !2)
!8 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "foo",
file: !1, line: 1, size: 8, flags: DIFlagTypePassByValue, *elements: !13*,
identifier: "_ZTS3foo")
!9 = !DISubroutineType(types: !10)
!10 = !{!11}
!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!12 = !DISubprogram(name: "f1", linkageName: "_ZN3foo2f1Ev", scope: !8,
file: !1, line: 2, *type: !14*, scopeLine: 2, flags: DIFlagPrototyped |
DIFlagStaticMember, spFlags: 0)




*!13 = !{!12}!14 = !DISubroutineType(types: !15)!15 = {!16}!16 =
DIBasicType(tag: DW_TAG_unspecified_type, name: "auto")*

On Thu, Dec 26, 2019 at 10:11 PM Awanish Pandey via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Dear all,
>
> I want to handle auto return type feature in the clang. The objective of
> this task is to store *auto *as the program return type in the
> declaration DIE and the actual return type in the definition DIE.
> Currently, clang only dumps actual return type in the declaration DIE.
> Based on my understanding I need two store two return types (auto for
> declaration and actual for definition). Is there any other way to tackle
> this scenario?
>
> --
> Thanking You
> Awanish Pandey
> PhD, CSE
> IIT Kanpur
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
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