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llvm-mirror/test/Bitcode/DISubprogram-distinct-definitions.ll
Adrian Prantl fb3abba237 [PR27284] Reverse the ownership between DICompileUnit and DISubprogram.
Currently each Function points to a DISubprogram and DISubprogram has a
scope field. For member functions the scope is a DICompositeType. DIScopes
point to the DICompileUnit to facilitate type uniquing.

Distinct DISubprograms (with isDefinition: true) are not part of the type
hierarchy and cannot be uniqued. This change removes the subprograms
list from DICompileUnit and instead adds a pointer to the owning compile
unit to distinct DISubprograms. This would make it easy for ThinLTO to
strip unneeded DISubprograms and their transitively referenced debug info.

Motivation
----------

Materializing DISubprograms is currently the most expensive operation when
doing a ThinLTO build of clang.

We want the DISubprogram to be stored in a separate Bitcode block (or the
same block as the function body) so we can avoid having to expensively
deserialize all DISubprograms together with the global metadata. If a
function has been inlined into another subprogram we need to store a
reference the block containing the inlined subprogram.

Attached to https://llvm.org/bugs/show_bug.cgi?id=27284 is a python script
that updates LLVM IR testcases to the new format.

http://reviews.llvm.org/D19034
<rdar://problem/25256815>

llvm-svn: 266446
2016-04-15 15:57:41 +00:00

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LLVM

; RUN: llvm-dis < %s.bc | FileCheck %s
; Check that subprogram definitions are correctly upgraded to 'distinct'.
; Bitcode compiled with llvm-as version 3.7.
define void @f() !dbg !3 { ret void }
!llvm.module.flags = !{!4}
!llvm.dbg.cu = !{!0}
!0 = distinct !DICompileUnit(language: 12, file: !1, subprograms: !{!3})
!1 = !DIFile(filename: "path/to/file", directory: "/path/to/dir")
; CHECK: = distinct !DISubprogram({{.*}}, isDefinition: true
!3 = !DISubprogram(name: "foo", isDefinition: true)
!4 = !{i32 2, !"Debug Info Version", i32 3}