[LLVMdev] Missing metadata for volatile variables

[Cindy Rubio González]

Hi everyone,

I am using the dragonegg plugin to produce bitcode for the following
small C program:

int main() {
1:  int x = -5;
2:  x = 6;
3:  return 0;
}

The assignments on lines 1 and 2 are removed even when no optimization
flags are specified. I tried making variable "x" volatile, which
prevents the assignments from being removed, however I am no longer
able to recover the original name of the variable "x". Below is the
bitcode generated. It seems like the metadata does not mention "x"
anywhere. Am I missing something?

Thank you,
Cindy


=========

; ModuleID = 'post/tests/test1/source.c'
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-f128:128:128-n8:16:32"
target triple = "i386-pc-linux-gnu"

module asm "\09.ident\09\22GCC: (GNU) 4.5.2 LLVM: exported\22"

%int = type i32

define i32 @main() nounwind {
entry:
  %memtmp = alloca i32
  %memtmp1 = alloca i32
  %"alloca point" = bitcast i32 0 to i32
  %"ssa point" = bitcast i32 0 to i32
  br label %"2", !dbg !6

"2":                                              ; preds = %entry
  call void @llvm.dbg.declare(metadata !{i32* %memtmp}, metadata !7), !dbg !9
  volatile store i32 -5, i32* %memtmp, align 4, !dbg !9
  volatile store i32 6, i32* %memtmp, align 4, !dbg !10
  store i32 0, i32* %memtmp1, align 1, !dbg !11
  br label %return, !dbg !11

return:                                           ; preds = %"2"
  %retval = load i32* %memtmp1, !dbg !11
  ret i32 %retval, !dbg !11
}

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

!llvm.dbg.sp = !{!0}

!0 = metadata !{i32 589870, i32 0, metadata !1, metadata !"main",
metadata !"main", metadata !"main", metadata !1, i32 1, metadata !3,
i1 false, i1 true, i32 0, i32 0, null, i32 0, i1 false, null} ; [
DW_TAG_subprogram ]
!1 = metadata !{i32 589865, metadata !"source.c", metadata
!"/afs/cs.wisc.edu/u/c/r/crubio/trunk/post/tests/test1", metadata !2}
; [ DW_TAG_file_type ]
!2 = metadata !{i32 589841, i32 0, i32 1, metadata !"source.c",
metadata !"post/tests/test1", metadata !"4.5.2", i1 true, i1 false,
metadata !"", i32 0} ; [ DW_TAG_compile_unit ]
!3 = metadata !{i32 589845, metadata !1, metadata !"", metadata !1,
i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !4, i32 0, null} ; [
DW_TAG_subroutine_type ]
!4 = metadata !{metadata !5}
!5 = metadata !{i32 589860, metadata !1, metadata !"int", metadata !1,
i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
!6 = metadata !{i32 1, i32 0, metadata !0, null}
!7 = metadata !{i32 590080, metadata !0, metadata !"memtmp", metadata
!1, i32 2, metadata !8, i32 0} ; [ DW_TAG_auto_variable ]
!8 = metadata !{i32 589877, metadata !1, metadata !"", metadata !1,
i32 0, i64 32, i64 32, i64 0, i32 0, metadata !5} ; [
DW_TAG_volatile_type ]
!9 = metadata !{i32 2, i32 0, metadata !0, null}
!10 = metadata !{i32 3, i32 0, metadata !0, null}
!11 = metadata !{i32 4, i32 0, metadata !0, null}

========