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DebugInfo: support for DWARFv5 DW_AT_alignment attribute

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* Assume that clang passes non-zero alignment value to DIBuilder
only in case when it was forced by C++11 'alignas', C11 '_Alignas'
or compiler attribute '__attribute__((aligned (N)))'.

* Emit DW_AT_alignment if alignment is specified for type/object.

Differential Revision: https://reviews.llvm.org/D24425


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285181 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Victor Leschuk
2016-10-26 08:55:27 +00:00
parent 6bee13e122
commit de2f92b5ef
10 changed files with 412 additions and 28 deletions
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docs/SourceLevelDebugging.rst
+26 -21
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@@ -386,7 +386,7 @@ Given an integer global variable declared as follows:
.. code-block:: c
int MyGlobal = 100;
_Alignas(8) int MyGlobal = 100;
a C/C++ front-end would generate the following descriptors:
@@ -395,54 +395,59 @@ a C/C++ front-end would generate the following descriptors:
;;
;; Define the global itself.
;;
@MyGlobal = global i32 100, align 4
@MyGlobal = global i32 100, align 8, !dbg !0
;;
;; List of debug info of globals
;;
!llvm.dbg.cu = !{!0}
!llvm.dbg.cu = !{!1}
;; Some unrelated metadata.
!llvm.module.flags = !{!6, !7}
!llvm.ident = !{!8}
;; Define the global variable itself
!0 = distinct !DIGlobalVariable(name: "MyGlobal", scope: !1, file: !2, line: 1, type: !5, isLocal: false, isDefinition: true, align: 64)
;; Define the compile unit.
!0 = !DICompileUnit(language: DW_LANG_C99, file: !1,
producer:
"clang version 3.7.0 (trunk 231150) (llvm/trunk 231154)",
isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug,
enums: !2, retainedTypes: !2, subprograms: !2, globals:
!3, imports: !2)
!1 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2,
producer: "clang version 4.0.0 (http://llvm.org/git/clang.git ae4deadbea242e8ea517eef662c30443f75bd086) (http://llvm.org/git/llvm.git 818b4c1539df3e51dc7e62c89ead4abfd348827d)",
isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug,
enums: !3, globals: !4)
;;
;; Define the file
;;
!1 = !DIFile(filename: "/dev/stdin",
!2 = !DIFile(filename: "/dev/stdin",
directory: "/Users/dexonsmith/data/llvm/debug-info")
;; An empty array.
!2 = !{}
!3 = !{}
;; The Array of Global Variables
!3 = !{!4}
;;
;; Define the global variable itself.
;;
!4 = !DIGlobalVariable(name: "MyGlobal", scope: !0, file: !1, line: 1,
type: !5, isLocal: false, isDefinition: true,
variable: i32* @MyGlobal)
!4 = !{!0}
;;
;; Define the type
;;
!5 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
;; Dwarf version to output.
!6 = !{i32 2, !"Dwarf Version", i32 2}
!6 = !{i32 2, !"Dwarf Version", i32 4}
;; Debug info schema version.
!7 = !{i32 2, !"Debug Info Version", i32 3}
;; Compiler identification
!8 = !{!"clang version 4.0.0 (http://llvm.org/git/clang.git ae4deadbea242e8ea517eef662c30443f75bd086) (http://llvm.org/git/llvm.git 818b4c1539df3e51dc7e62c89ead4abfd348827d)"}
The align value in DIGlobalVariable description specifies variable alignment in
case it was forced by C11 _Alignas(), C++11 alignas() keywords or compiler
attribute __attribute__((aligned ())). In other case (when this field is missing)
alignment is considered default. This is used when producing DWARF output
for DW_AT_alignment value.
C/C++ function information
--------------------------