| Issue |
136506
|
| Summary |
[WebAssembly] `DEBUG_VALUE`s not collected for non-first defs
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
SingleAccretion
|
In writing a test for an unrelated issue, I came across this code:
https://github.com/llvm/llvm-project/blob/842e5915778a820c63cf38b75bec932a6ea8c18b/llvm/lib/Target/WebAssembly/WebAssemblyDebugValueManager.cpp#L29-L44
This means that any non-first defs of multivalue instructions will get their `DEBUG_VALUE`s dropped. The reproduction is something like below:
```llvm
target triple = "wasm32-unknown-unknown"
declare {i32, i32} @extern_func_multivalue(i32, i32)
define i32 @single_non_dbg_use_multivalue(i32 %0, i32 %1) !dbg !15 {
%full_value = call {i32, i32} @extern_func_multivalue(i32 1, i32 2), !dbg !27
%full_value_one = extractvalue {i32, i32} %full_value, 0, !dbg !27
%full_value_two = extractvalue {i32, i32} %full_value, 1, !dbg !27
call void @llvm.dbg.value(metadata i32 %full_value_two, metadata !16, metadata !DIExpression()), !dbg !28
%partial_value = call {i32, i32} @extern_func_multivalue(i32 %full_value_one, i32 %full_value_two), !dbg !28
%partial_value_one = extractvalue {i32, i32} %partial_value, 0, !dbg !28
%partial_value_two = extractvalue {i32, i32} %partial_value, 1, !dbg !28
call void @llvm.dbg.value(metadata i32 %partial_value_two, metadata !17, metadata !DIExpression()), !dbg !28
ret i32 %partial_value_one, !dbg !29
}
!15 = distinct !DISubprogram(name: "single_non_dbg_use_multivalue", scope: !1, file: !1, type: !7, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
!16 = !DILocalVariable(name: "value_used", scope: !15, type: !9)
!17 = !DILocalVariable(name: "value_unused", scope: !15, type: !9)
!27 = !DILocation(line: 27, scope: !15)
!28 = !DILocation(line: 28, scope: !15)
!29 = !DILocation(line: 29, scope: !15)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!2, !3}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "LLC", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.ll", directory: "")
!2 = !{i32 7, !"Dwarf Version", i32 4}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!7 = !DISubroutineType(types: !8)
!8 = !{!9, !9, !9}
!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
```
```bash
> llc test.ll -mattr=+multivalue -target-abi=experimental-mv -O0 -o - --filetype=obj | llvm-dwarfdump -
```
```dwarf
0x0000000b: DW_TAG_compile_unit
DW_AT_producer ("LLC")
DW_AT_language (DW_LANG_C_plus_plus_14)
DW_AT_name ("test.ll")
DW_AT_stmt_list (0x00000000)
DW_AT_low_pc (0x00000002)
DW_AT_high_pc (0x0000002c)
0x00000022: DW_TAG_subprogram
DW_AT_low_pc (0x00000002)
DW_AT_high_pc (0x0000002c)
DW_AT_frame_base (DW_OP_WASM_location 0x3 0x0, DW_OP_stack_value)
DW_AT_name ("single_non_dbg_use_multivalue")
DW_AT_type (0x0000003b "int")
DW_AT_external (true)
0x0000003b: DW_TAG_base_type
DW_AT_name ("int")
DW_AT_encoding (DW_ATE_signed)
DW_AT_byte_size (0x04)
```
We should expect to see the variable record for at least `value_used` (`value_unused` looks to be getting dropped earlier).
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