llvm/test/DebugInfo/MIR/InstrRef/livedebugvalues_recover_clobbers.mir

--- |
  ; RUN: llc %s -march=x86-64 -run-pass=livedebugvalues -o - -force-instr-ref-livedebugvalues=1 -emulate-old-livedebugvalues=0 | FileCheck %s -implicit-check-not=DBG_VALUE

  ;; When using instruction referencing LiveDebugValues, when a register gets
  ;; clobbered, we should transfer variable locations to backup locations, if
  ;; one is available.
  ;; I've written this test in terms of DBG_VALUEs rather than DBG_INSTR_REFs
  ;; as this is purely a LiveDebugValues feature, and should work without the
  ;; need to use any other instructoin referencing work.

  declare i32 @use() local_unnamed_addr;

  define i32 @_Z8bb_to_bb() local_unnamed_addr !dbg !12 {
  entry:
    br label %bb1, !dbg !17
  bb1:
    br label %bb2, !dbg !17
  bb2:
    br label %bb3, !dbg !17
  bb3:
    br label %bb3, !dbg !17
  bb4:
    br label %bb3, !dbg !17
  bb5:
    ret i32 0, !dbg !17
  }

  !llvm.dbg.cu = !{!0}
  !llvm.module.flags = !{!7, !8, !9, !10}
  !llvm.ident = !{!11}
  !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3, debugInfoForProfiling: true, nameTableKind: None)
  !1 = !DIFile(filename: "main.cpp", directory: "F:\")
  !2 = !{}
  !3 = !{!4}
  !4 = !DIGlobalVariableExpression(var: !5, expr: !DIExpression())
  !5 = distinct !DIGlobalVariable(name: "start", scope: !0, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true)
  !6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
  !7 = !{i32 2, !"Dwarf Version", i32 4}
  !8 = !{i32 2, !"Debug Info Version", i32 3}
  !9 = !{i32 1, !"wchar_size", i32 2}
  !10 = !{i32 7, !"PIC Level", i32 2}
  !11 = !{!"clang version 10.0.0"}
  !12 = distinct !DISubprogram(name: "bb_to_bb", linkageName: "bb_to_bb", scope: !1, file: !1, line: 6, type: !13, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !15)
  !13 = !DISubroutineType(types: !14)
  !14 = !{!6, !6}
  !15 = !{!16}
  !16 = !DILocalVariable(name: "myVar", scope: !12, file: !1, line: 7, type: !6)
  !17 = !DILocation(line: 10, scope: !12)

...
---
name: _Z8bb_to_bb
stack:
  - { id: 0, type: spill-slot, offset: -12, size: 4, alignment: 4 }
body:  |
  bb.0.entry:
    $eax = MOV32ri 0, debug-location !17
    $eax = COPY $ebx
    DBG_VALUE $eax, $noreg, !16, !DIExpression(), debug-location !17
    ;; Over-write eax, we should recover its location as being in ebx.
    $eax = MOV32ri 0, debug-location !17

    ; CHECK:      DBG_VALUE $eax
    ; CHECK-NEXT: $eax = MOV32ri 0
    ; CHECK-NEXT: DBG_VALUE $ebx

    ;; The same should occur for spills.
    $ebx = MOV32ri 2, debug-location !17
    MOV32mr $rsp, 1, _, -12, _, killed $ebx :: (store 4 into %stack.0)
    DBG_VALUE $ebx, $noreg, !16, !DIExpression(), debug-location !17
    $ebx = MOV32ri 0, debug-location !17

    ; CHECK-NEXT: $ebx = MOV32ri 2
    ; CHECK-NEXT: MOV32mr $rsp
    ; CHECK-NEXT: DBG_VALUE $ebx
    ; CHECK-NEXT: $ebx = MOV32ri
    ; CHECK-NEXT: DBG_VALUE $rsp

    ;; Now test copies and register masks.
    $eax = COPY $ebx
    DBG_VALUE $ebx, $noreg, !16, !DIExpression(), debug-location !17
    ;; Overwrite ebx with a copy.
    $ecx = MOV32ri 1, debug-location !17
    $ebx = COPY $ecx

    ; CHECK:      DBG_VALUE $ebx
    ; CHECK-NEXT: $ecx = MOV32ri
    ; CHECK-NEXT: $ebx = COPY
    ; CHECK-NEXT: DBG_VALUE $eax

    ;; Similarly, with a register mask
    $ebx = COPY $eax
    CALL64pcrel32 @use, csr_64, implicit $rsp, implicit $edi, implicit-def $rsp, debug-location !17

    ; CHECK-NEXT: $ebx = COPY $eax
    ; CHECK-NEXT: CALL64pcrel32
    ; CHECK-NEXT: DBG_VALUE $ebx

    RET64 $eax, debug-location !17
...