[LLVMdev] Trying to access the user defined variable name

[Arvind Sudarsanam]

Dear all,

I have the following source code:

long f(long x, long y)
{
	long u;
	
   u = x+y;	
   return u;
};

After clang (with debug option set) and llvm opt using mem2reg, I get
the following .ll file
***************************************************************************
; ModuleID = '<stdin>'
target datalayout =
"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
target triple = "i686-pc-linux-gnu"

define i32 @f(i32 %x, i32 %y) nounwind {
entry:
  call void @llvm.dbg.value(metadata !{i32 %x}, i64 0, metadata !0)
  call void @llvm.dbg.value(metadata !{i32 %y}, i64 0, metadata !7)
  %add = add nsw i32 %x, %y, !dbg !8              ; <i32> [#uses=1]
  call void @llvm.dbg.value(metadata !{i32 %add}, i64 0, metadata !10), !dbg !8
  ret i32 %add, !dbg !11
}

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

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

!0 = metadata !{i32 524545, metadata !1, metadata !"x", metadata !2,
i32 1, metadata !6} ; [ DW_TAG_arg_variable ]
!1 = metadata !{i32 524334, i32 0, metadata !2, metadata !"f",
metadata !"f", metadata !"f", metadata !2, i32 2, metadata !4, i1
false, i1 true, i32 0, i32 0, null, i1 false, i1 false} ; [
DW_TAG_subprogram ]
!2 = metadata !{i32 524329, metadata !"testadd.c", metadata
!"/home/asudarsanam/perforce/llvmtop/setup", metadata !3} ; [
DW_TAG_file_type ]
!3 = metadata !{i32 524305, i32 0, i32 12, metadata !"testadd.c",
metadata !".", metadata !"clang 2.0", i1 true, i1 false, metadata !"",
i32 0} ; [ DW_TAG_compile_unit ]
!4 = metadata !{i32 524309, metadata !2, metadata !"", metadata !2,
i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !5, i32 0, null} ; [
DW_TAG_subroutine_type ]
!5 = metadata !{metadata !6}
!6 = metadata !{i32 524324, metadata !2, metadata !"long", metadata
!2, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
!7 = metadata !{i32 524545, metadata !1, metadata !"y", metadata !2,
i32 1, metadata !6} ; [ DW_TAG_arg_variable ]
!8 = metadata !{i32 5, i32 4, metadata !9, null}
!9 = metadata !{i32 524299, metadata !1, i32 2, i32 1} ; [
DW_TAG_lexical_block ] !10 = metadata !{i32 524544, metadata !9,
metadata !"u", metadata !2, i32 3, metadata !6} ; [
DW_TAG_auto_variable ]
!11 = metadata !{i32 7, i32 1, metadata !9, null}
******************************************************************

Llvm has replaced the name of the local variable (u) by a temporary
name (%add). However, the debug information contains the information
about the original variable name.  **** !10 = metadata !{i32 524544,
metadata !9, metadata !"u", metadata !2, i32 3, metadata !6} ; [
DW_TAG_auto_variable ] ******

I have been trying for a while and have been unsuccessful in accessing
this information (mapping between the temporary name (%add) and the
actual name (u)). What I need is this: When I access the llvm value
that points to the temporary name (%add), I need to identify that it
replaces the actual name (u).

Can anyone help me out please?

Thanks
Regards
Arvind