[PATCH] Debug info: Support fragmented variables.

[Manman Ren]

Noticed one copy-pasto:
/// getPieceOffset - Return the offset of this piece in bytes.
  uint64_t getPieceOffset() const;
  /// getPieceOffset - Return the offset of this piece in bytes.
  uint64_t getPieceSize() const;

Manman


On Mon, Feb 3, 2014 at 3:41 PM, Adrian Prantl <aprantl at apple.com> wrote:

>
>   Hi David,
>
>   Here's the MDNodes for the two variable pieces:
>     !20 = metadata !{i32 786689, metadata !4, metadata !"s", metadata !5,
> i32 16777219, metadata !9, i32 0, i32 0, i32 3, i32 0, i32 8} ; [
> DW_TAG_arg_variable ] [s] [line 3]
>     !21 = metadata !{i32 786689, metadata !4, metadata !"s", metadata !5,
> i32 16777219, metadata !9, i32 0, i32 0, i32 3, i32 8, i32 4} ; [
> DW_TAG_arg_variable ] [s] [line 3]
>
>   All the way through ISel and the MC layer those two MDNodes behave like
> regular DIVariables with complex addresses. In DwarfDebug, we need to treat
> the pieces as one entity when calculating the Ranges/History.
> getEntireVariable() simply chops off the last two elements so it can be
> used as a shared  index into DbgVariables while still indicating that this
> is a fragmented location. The extra code in the range calculation makes
> sure that a piece of a variable is not clobbered by a non-overlapping piece.
>
>   FYI: In a previous design I experimented with introducing a new type
> MDnode
>     !Piece = metadata !{i32 PIECE, metadata !<ref to DIVariable>, metadata
> !<Offset>, metadata !<Size>}
>   but this meant adding an extra case to all the ISel/MC code handling
> DBG_VALUEs, which is why I ended up with the current design.
>
>   --  adrian
>
> http://llvm-reviews.chandlerc.com/D2680
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