llc -run-pass=regallocfast regallocfast.g.mir -o - -verify-machineinstrs

regallocfast.g.mir

--- |
  ; ModuleID = 'regallocfast.g.mir'
  source_filename = "x.c"
  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
  target triple = "x86_64-unknown-linux-gnu"
  
  ; Function Attrs: noinline nounwind optnone
  define dso_local i32 @main() #0 !dbg !9 {
  entry:
    %retval = alloca i32, align 4
    %x = alloca i32, align 4
    store i32 0, ptr %retval, align 4
    call void @llvm.dbg.declare(metadata ptr %x, metadata !14, metadata !DIExpression()), !dbg !15
    store i32 123, ptr %x, align 4, !dbg !15
    %0 = callbr i32 asm "mov $1, $0\0A\09jmp ${2:l}", "=r,r,!i,~{dirflag},~{fpsr},~{flags}"(i32 45) #3
            to label %asm.fallthrough [label %label.split], !dbg !16, !srcloc !17
  
  asm.fallthrough:                                  ; preds = %entry
    store i32 %0, ptr %x, align 4, !dbg !16
    store i32 6, ptr %x, align 4, !dbg !18
    br label %label, !dbg !19
  
  label:                                            ; preds = %label.split, %asm.fallthrough
    call void @llvm.dbg.label(metadata !20), !dbg !21
    %1 = load i32, ptr %x, align 4, !dbg !22
    ret i32 %1, !dbg !23
  
  label.split:                                      ; preds = %entry
    %2 = call i32 @llvm.callbr.landingpad.i32(i32 %0), !dbg !16
    store i32 %2, ptr %x, align 4, !dbg !16
    br label %label, !dbg !16
  }
  
  ; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
  declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
  
  ; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
  declare void @llvm.dbg.label(metadata) #1
  
  ; Function Attrs: nomerge nounwind
  declare i32 @llvm.callbr.landingpad.i32(i32) #2
  
  attributes #0 = { noinline nounwind optnone "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
  attributes #1 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
  attributes #2 = { nomerge nounwind }
  attributes #3 = { nounwind memory(none) }
  
  !llvm.dbg.cu = !{!0}
  !llvm.module.flags = !{!2, !3, !4, !5, !6, !7}
  !llvm.ident = !{!8}
  
  !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 17.0.0 (git@github.com:llvm/llvm-project.git 7de8ebde4f8f92129d47fda1c05d4b3d9a4d99d8)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
  !1 = !DIFile(filename: "x.c", directory: "/android0/llvm-project", checksumkind: CSK_MD5, checksum: "a7d7b4f8bb9445eef3bb86a226401f5c")
  !2 = !{i32 7, !"Dwarf Version", i32 5}
  !3 = !{i32 2, !"Debug Info Version", i32 3}
  !4 = !{i32 1, !"wchar_size", i32 4}
  !5 = !{i32 8, !"PIC Level", i32 2}
  !6 = !{i32 7, !"PIE Level", i32 2}
  !7 = !{i32 7, !"frame-pointer", i32 2}
  !8 = !{!"clang version 17.0.0 (git@github.com:llvm/llvm-project.git 7de8ebde4f8f92129d47fda1c05d4b3d9a4d99d8)"}
  !9 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 4, type: !10, scopeLine: 4, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !13)
  !10 = !DISubroutineType(types: !11)
  !11 = !{!12}
  !12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
  !13 = !{}
  !14 = !DILocalVariable(name: "x", scope: !9, file: !1, line: 5, type: !12)
  !15 = !DILocation(line: 5, column: 9, scope: !9)
  !16 = !DILocation(line: 6, column: 5, scope: !9)
  !17 = !{i64 166, i64 179}
  !18 = !DILocation(line: 7, column: 7, scope: !9)
  !19 = !DILocation(line: 7, column: 5, scope: !9)
  !20 = !DILabel(scope: !9, name: "label", file: !1, line: 8)
  !21 = !DILocation(line: 8, column: 5, scope: !9)
  !22 = !DILocation(line: 9, column: 12, scope: !9)
  !23 = !DILocation(line: 9, column: 5, scope: !9)

...
---
name:            main
alignment:       16
exposesReturnsTwice: false
legalized:       false
regBankSelected: false
selected:        false
failedISel:      false
tracksRegLiveness: true
hasWinCFI:       false
callsEHReturn:   false
callsUnwindInit: false
hasEHCatchret:   false
hasEHScopes:     false
hasEHFunclets:   false
debugInstrRef:   false
failsVerification: false
tracksDebugUserValues: false
registers:       []
liveins:         []
frameInfo:
  isFrameAddressTaken: false
  isReturnAddressTaken: false
  hasStackMap:     false
  hasPatchPoint:   false
  stackSize:       0
  offsetAdjustment: 0
  maxAlignment:    4
  adjustsStack:    false
  hasCalls:        false
  stackProtector:  ''
  functionContext: ''
  maxCallFrameSize: 4294967295
  cvBytesOfCalleeSavedRegisters: 0
  hasOpaqueSPAdjustment: false
  hasVAStart:      false
  hasMustTailInVarArgFunc: false
  hasTailCall:     false
  localFrameSize:  0
  savePoint:       ''
  restorePoint:    ''
fixedStack:      []
stack:
  - { id: 0, name: retval, type: default, offset: 0, size: 4, alignment: 4, 
      stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
  - { id: 1, name: x, type: default, offset: 0, size: 4, alignment: 4, 
      stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
      debug-info-variable: '!14', debug-info-expression: '!DIExpression()', 
      debug-info-location: '!15' }
  - { id: 2, name: '', type: spill-slot, offset: 0, size: 4, alignment: 4, 
      stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
  - { id: 3, name: '', type: spill-slot, offset: 0, size: 4, alignment: 4, 
      stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
callSites:       []
debugValueSubstitutions: []
constants:       []
machineFunctionInfo: {}
body:             |
  bb.0.entry:
    successors: %bb.1(0x40000000), %bb.3(0x40000000)
  
    MOV32mi %stack.0.retval, 1, $noreg, 0, $noreg, 0 :: (store (s32) into %ir.retval)
    MOV32mi %stack.1.x, 1, $noreg, 0, $noreg, 123, debug-location !15 :: (store (s32) into %ir.x)
    renamable $eax = MOV32ri 45
    INLINEASM_BR &"mov $1, $0\0A\09jmp ${2:l}", 0 /* attdialect */, 2359306 /* regdef:GR32 */, def renamable $eax, 2359305 /* reguse:GR32 */, killed renamable $eax, 13 /* imm */, %bb.3, 12 /* clobber */, implicit-def dead early-clobber $df, 12 /* clobber */, implicit-def early-clobber $fpsw, 12 /* clobber */, implicit-def dead early-clobber $eflags, !17, debug-location !16
    MOV32mr %stack.3, 1, $noreg, 0, $noreg, $eax :: (store (s32) into %stack.3)
    MOV32mr %stack.2, 1, $noreg, 0, $noreg, killed $eax :: (store (s32) into %stack.2)
    JMP_1 %bb.1, debug-location !16
  
  bb.1.asm.fallthrough:
    successors: %bb.2(0x80000000)
  
    $eax = MOV32rm %stack.2, 1, $noreg, 0, $noreg :: (load (s32) from %stack.2)
    MOV32mr %stack.1.x, 1, $noreg, 0, $noreg, renamable $eax, debug-location !16 :: (store (s32) into %ir.x)
    MOV32mi %stack.1.x, 1, $noreg, 0, $noreg, 6, debug-location !18 :: (store (s32) into %ir.x)
  
  bb.2.label:
    DBG_LABEL !20, debug-location !21
    renamable $eax = MOV32rm %stack.1.x, 1, $noreg, 0, $noreg, debug-location !22 :: (load (s32) from %ir.x)
    RET64 implicit killed $eax, debug-location !23
  
  bb.3.label.split (machine-block-address-taken, inlineasm-br-indirect-target):
    successors: %bb.2(0x80000000)
    liveins: $eax
  
    MOV32mr %stack.3, 1, $noreg, 0, $noreg, $eax :: (store (s32) into %stack.3)
    $eax = MOV32rm %stack.3, 1, $noreg, 0, $noreg :: (load (s32) from %stack.3)
    MOV32mr %stack.1.x, 1, $noreg, 0, $noreg, killed renamable $eax, debug-location !16 :: (store (s32) into %ir.x)
    JMP_1 %bb.2, debug-location !16

...

Of the above, it looks like the following are missing debug-location:

    MOV32mi %stack.0.retval, 1, $noreg, 0, $noreg, 0 :: (store (s32) into %ir.retval)
    renamable $eax = MOV32ri 45
    MOV32mr %stack.3, 1, $noreg, 0, $noreg, $eax :: (store (s32) into %stack.3)
    MOV32mr %stack.2, 1, $noreg, 0, $noreg, killed $eax :: (store (s32) into %stack.2)
    $eax = MOV32rm %stack.2, 1, $noreg, 0, $noreg :: (load (s32) from %stack.2)
    MOV32mr %stack.3, 1, $noreg, 0, $noreg, $eax :: (store (s32) into %stack.3)
    $eax = MOV32rm %stack.3, 1, $noreg, 0, $noreg :: (load (s32) from %stack.3)