[LLVMdev] Need more information on llvm.dbg.value call

[Seb]

Hi all,


I'm using clang + LLVM 2.9. Let's consider following code sample:

extern void bar(int x) ;

void foo(int y)
{
    bar(y) ;
}

When compiled with clang at -O2 -g I've got following LLVM file:

; ModuleID = 'localvar.c'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-unknown-linux-gnu"

define void @foo(i32 %y) nounwind {
  tail call void @llvm.dbg.value(metadata !{i32 %y}, i64 0, metadata !5),
!dbg !7
  tail call void @bar(i32 %y) nounwind, !dbg !8
  ret void, !dbg !10
}

declare void @bar(i32)

declare void @llvm.dbg.value(metadata, i64, metadata) nounwind readnone

!llvm.dbg.sp = !{!0}
!llvm.dbg.lv.foo = !{!5}

!0 = metadata !{i32 589870, i32 0, metadata !1, metadata !"foo", metadata
!"foo", metadata !"", metadata !1, i32 5, metadata !3, i1 false, i1 true,
i32 0, i32 0, i32 0, i32 256, i1 true, void (i32)* @foo} ; [
DW_TAG_subprogram ]
!1 = metadata !{i32 589865, metadata !"localvar.c", metadata
!"/home/deldon/Work/OpenCL/DEBUG", metadata !2} ; [ DW_TAG_file_type ]
!2 = metadata !{i32 589841, i32 0, i32 12, metadata !"localvar.c", metadata
!"/home/deldon/Work/OpenCL/DEBUG", metadata !"clang version 2.9
(tags/RELEASE_29/final)", i1 true, i1 true, metadata !"", i32 0} ; [
DW_TAG_compile_unit ]
!3 = metadata !{i32 589845, metadata !1, metadata !"", metadata !1, i32 0,
i64 0, i64 0, i32 0, i32 0, i32 0, metadata !4, i32 0, i32 0} ; [
DW_TAG_subroutine_type ]
!4 = metadata !{null}
!5 = metadata !{i32 590081, metadata !0, metadata !"y", metadata !1, i32
16777220, metadata !6, i32 0} ; [ DW_TAG_arg_variable ]
!6 = metadata !{i32 589860, metadata !2, metadata !"int", null, i32 0, i64
32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
!7 = metadata !{i32 4, i32 14, metadata !0, null}
!8 = metadata !{i32 6, i32 5, metadata !9, null}
!9 = metadata !{i32 589835, metadata !0, i32 5, i32 1, metadata !1, i32 0}
; [ DW_TAG_lexical_block ]
!10 = metadata !{i32 7, i32 1, metadata !9, null}

Can someone give me more information on llvm.dbg.value call because
documentation is unclear to me ?
Why is there an 'llvm.dbg.lv.foo' created ? This is also not documented.

Thanks for your answers
Seb
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