[LLVMdev] DW_AT_location not getting generated for local variables
Devang Patel
dpatel at apple.com
Tue Jan 3 09:47:57 PST 2012
Hi Joe,
On Jan 2, 2012, at 11:55 AM, Joe Groff wrote:
> I found the problem. The llvm.dbg.declare call must have a !dbg tag,
> otherwise the location info is not generated. Changing the invocation
> in my original example to "call void @llvm.dbg.declare(metadata !{i32*
> %"bar:Int32"}, metadata !13), !dbg !16" causes MC to generate the
> local location as expected.
We want to go in direction where metadata !13 (node for DW_TAG_auto_variable) will have enough location information for location so that !dbg is not required for llvm.dbg.declare intrinsic.
-
Devang
> -Joe
>
> On Thu, Dec 29, 2011 at 12:41 PM, Joe Groff <arcata at gmail.com> wrote:
>> I figured out my previous problem with DIBuilder. However, now I can't seem
>> to get the compiler to emit location information for local variables. Here's
>> how my IR looks:
>>
>> ---
>> define i32 @"\01_main"() {
>> init:
>> %exception1 = alloca i8*
>> %0 = alloca i32
>> %"bar:Int32" = alloca i32
>> %1 = alloca i32
>> %2 = alloca i32*
>> br label %code
>>
>> code: ; preds = %init
>> call void @llvm.dbg.declare(metadata !{i32* %"bar:Int32"}, metadata !13)
>> store i32 1, i32* %"bar:Int32", !dbg !16
>> store i32 1, i32* %1, !dbg !17
>> %3 = load i32* %"bar:Int32", !dbg !17
>> %4 = load i32* %1, !dbg !17
>> %5 = add i32 %3, %4, !dbg !17
>> store i32 %5, i32* %"bar:Int32", !dbg !17
>> store i32* %"bar:Int32", i32** %2, !dbg !18
>> %6 = load i32** %2, !dbg !18
>> %7 = load i32* %6, !dbg !18
>> store i32 %7, i32* %0, !dbg !18
>> br label %return, !dbg !18
>>
>> return: ; preds = %code
>> %8 = load i32* %0
>> ret i32 %8
>>
>> exception: ; No predecessors!
>> unreachable
>> }
>>
>> declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
>>
>> !llvm.dbg.cu = !{!0}
>>
>> !0 = metadata !{i32 720913, i32 0, i32 49572, metadata !"foo.clay", metadata
>> !"", metadata !"clay compiler 0.1git", i1 true, i1 false, metadata !"", i32
>> 0, metadata !1, metadata !1, metadata !3, metadata !1} ; [
>> DW_TAG_compile_unit ]
>> !1 = metadata !{metadata !2}
>> !2 = metadata !{i32 0}
>> !3 = metadata !{metadata !4}
>> !4 = metadata !{metadata !5}
>> !5 = metadata !{i32 720942, i32 0, metadata !6, metadata !"foo", metadata
>> !"foo", metadata !"\01_main", metadata !7, i32 1, metadata !8, i1 false, i1
>> true, i32 0, i32 0, i32 0, i32 0, i1 false, i32 ()* @"\01_main", null, null,
>> metadata !11} ; [ DW_TAG_subprogram ]
>> !6 = metadata !{i32 720953, null, metadata !"__main__", metadata !7, i32 1}
>> ; [ DW_TAG_namespace ]
>> !7 = metadata !{i32 720937, metadata !"foo.clay", metadata !"", null} ; [
>> DW_TAG_file_type ]
>> !8 = metadata !{i32 720917, i32 0, metadata !"", i32 0, i32 0, i64 0, i64 0,
>> i32 0, i32 0, i32 0, metadata !9, i32 0, i32 0} ; [ DW_TAG_subroutine_type ]
>> !9 = metadata !{metadata !10}
>> !10 = metadata !{i32 720932, null, metadata !"Int32", null, i32 0, i64 32,
>> i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
>> !11 = metadata !{metadata !12}
>> !12 = metadata !{metadata !13}
>> !13 = metadata !{i32 721152, metadata !14, metadata !"bar", metadata !7, i32
>> 2, metadata !10, i32 0, i32 0} ; [ DW_TAG_auto_variable ]
>> !14 = metadata !{i32 720907, metadata !15, i32 1, i32 1, metadata !7, i32 1}
>> ; [ DW_TAG_lexical_block ]
>> !15 = metadata !{i32 720907, metadata !5, i32 1, i32 1, metadata !7, i32 0}
>> ; [ DW_TAG_lexical_block ]
>> !16 = metadata !{i32 2, i32 2, metadata !14, null}
>> !17 = metadata !{i32 3, i32 3, metadata !14, null}
>> !18 = metadata !{i32 4, i32 4, metadata !14, null}
>> ---
>>
>> And this is what dwarfdump on the compiled object file shows. The
>> TAG_variable entry for 'bar' is missing its AT_location.
>>
>> ---
>> ----------------------------------------------------------------------
>> File: foo.o (x86_64)
>> ----------------------------------------------------------------------
>> .debug_info contents:
>>
>> 0x00000000: Compile Unit: length = 0x000000a9 version = 0x0002 abbr_offset
>> = 0x00000000 addr_size = 0x08 (next CU at 0x000000ad)
>>
>> 0x0000000b: TAG_compile_unit [1] *
>> AT_producer( "clay compiler 0.1git" )
>> AT_language( Unknown DW_LANG constant: 0xc1a4 )
>> AT_name( "foo.clay" )
>> AT_entry_pc( 0x0000000000000000 )
>> AT_stmt_list( 0x00000000 )
>>
>> 0x00000038: TAG_namespace [2] *
>> AT_sibling( {0x0000005c} )
>> AT_name( "__main__" )
>> AT_decl_file(
>> "/Users/joe/Documents/Code/others/clay/foo.clay" )
>> AT_decl_line( 1 )
>>
>> 0x00000048: TAG_subprogram [3]
>> AT_MIPS_linkage_name( "_main" )
>> AT_name( "foo" )
>> AT_decl_file(
>> "/Users/joe/Documents/Code/others/clay/foo.clay" )
>> AT_decl_line( 1 )
>> AT_type( {0x0000005c} ( Int32 ) )
>> AT_external( 0x01 )
>> AT_declaration( 0x01 )
>>
>> 0x0000005b: NULL
>>
>> 0x0000005c: TAG_base_type [4]
>> AT_name( "Int32" )
>> AT_encoding( DW_ATE_signed )
>> AT_byte_size( 0x04 )
>>
>> 0x00000065: TAG_subprogram [5] *
>> AT_specification( {0x00000048} ( "_main" ) )
>> AT_low_pc( 0x0000000000000020 )
>> AT_high_pc( 0x0000000000000051 )
>> AT_frame_base( rbp )
>>
>> 0x0000007c: TAG_lexical_block [6] *
>> AT_low_pc( 0x0000000000000028 )
>> AT_high_pc( 0x000000000000004c )
>>
>> 0x0000008d: TAG_lexical_block [6] *
>> AT_low_pc( 0x0000000000000028 )
>> AT_high_pc( 0x000000000000004c )
>>
>> 0x0000009e: TAG_variable [7]
>> AT_name( "bar" )
>> AT_decl_file(
>> "/Users/joe/Documents/Code/others/clay/foo.clay" )
>> AT_decl_line( 2 )
>> AT_type( {0x0000005c} ( Int32 ) )
>>
>> 0x000000a9: NULL
>>
>> 0x000000aa: NULL
>>
>> 0x000000ab: NULL
>>
>> 0x000000ac: NULL
>> ---
>>
>> Am I using llvm.dbg.declare correctly? Is there something missing in my
>> metadata?
>>
>> -Joe
>
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