Index: llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
===================================================================
--- llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -2355,12 +2355,6 @@
     SmallPtrSet<const MachineBasicBlock *, 8> &InScopeBlocks,
     SmallPtrSet<const MachineBasicBlock *, 8> &BlocksToExplore,
     DbgValue &LiveIn) {
-  // To emulate VarLocBasedImpl, process this block if it's not in scope but
-  // _does_ assign a variable value. No live-ins for this scope are transferred
-  // in though, so we can return immediately.
-  if (InScopeBlocks.count(&MBB) == 0 && !ArtificialBlocks.count(&MBB))
-    return false;
-
   LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
   bool Changed = false;
 
@@ -2759,6 +2753,8 @@
         continue;
       if (BlockLiveIn->Kind == DbgValue::VPHI)
         BlockLiveIn->Kind = DbgValue::Def;
+      assert(BlockLiveIn->Properties.DIExpr->getFragmentInfo() ==
+             Var.getFragment() && "Fragment info missing during value prop");
       Output[MBB->getNumber()].push_back(std::make_pair(Var, *BlockLiveIn));
     }
   } // Per-variable loop.
Index: llvm/test/DebugInfo/MIR/InstrRef/out-of-scope-blocks.mir
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/MIR/InstrRef/out-of-scope-blocks.mir
@@ -0,0 +1,151 @@
+# RUN: llc %s -o - -run-pass=livedebugvalues -march=x86-64 \
+# RUN:     -experimental-debug-variable-locations=true \
+# RUN: | FileCheck %s
+#
+## This test used to crash InstrRefBasedLDV, due to fragment information going
+## missing; test for that, and also check what happens when we have assignments
+## outside of lexical scope. In the IR below, "_First" is only in scope in the
+## entry block, but is assigned in every block. Under current behaviour, that
+## means that InstrRefBasedLDV will propagate its location through all blocks.
+#
+# CHECK:       ![[FIRSTVAR:[0-9]+]] = !DILocalVariable(name: "_First",
+#
+# CHECK-LABEL: bb.0.entry:
+# CHECK:       DBG_VALUE $rbx, $noreg, ![[FIRSTVAR]],
+# CHECK-SAME:        !DIExpression(DW_OP_LLVM_fragment, 64, 64)
+#
+# CHECK-LABEL: bb.1.if.then.i.i.i.i.i:
+# CHECK:       DBG_VALUE $rbx, $noreg, ![[FIRSTVAR]],
+# CHECK-SAME:        !DIExpression(DW_OP_LLVM_fragment, 64, 64)
+# CHECK:       DBG_INSTR_REF {{.*}} ![[FIRSTVAR]],
+# CHECK:       DBG_VALUE $rbx, $noreg, ![[FIRSTVAR]],
+# CHECK-SAME:        !DIExpression(DW_OP_LLVM_fragment, 64, 64)
+
+# CHECK-LABEL: bb.2._Z17do_insert_cv_testI5_TreeEvv.exit:
+# CHECK:       DBG_VALUE $rbx, $noreg, ![[FIRSTVAR]],
+# CHECK-SAME:        !DIExpression(DW_OP_LLVM_fragment, 64, 64)
+# CHECK:       DBG_INSTR_REF {{.*}} ![[FIRSTVAR]],
+# CHECK:       DBG_VALUE $rbx, $noreg, ![[FIRSTVAR]],
+# CHECK-SAME:        !DIExpression(DW_OP_LLVM_fragment, 64, 64)
+
+--- |
+  source_filename = "reduced.ll"
+  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+  
+  %class._Tree = type { i8 }
+  %class._Tree_const_iterator = type { %class._Tree_unchecked_const_iterator }
+  %class._Tree_unchecked_const_iterator = type { %struct._Iterator_base0, i32* }
+  %struct._Iterator_base0 = type { i32 }
+  
+  define i32 @main({ i32, i32* } %call.i) !dbg !6 {
+  entry:
+    call void @llvm.dbg.value(metadata i32 2, metadata !10, metadata !DIExpression()), !dbg !12
+    %call.i1 = call { i32, i32* } undef(%class._Tree* null)
+    %0 = extractvalue { i32, i32* } %call.i, 1
+    call void @llvm.dbg.value(metadata i32* %0, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 64)), !dbg !15
+    %call.i.i.i.i.i = call i8 undef(i32* null), !dbg !15
+    br i1 undef, label %_Z17do_insert_cv_testI5_TreeEvv.exit, label %if.then.i.i.i.i.i
+  
+  if.then.i.i.i.i.i:
+    %call3.i.i.i.i.i = call i32* undef(i32* null)
+    call void @llvm.dbg.value(metadata i32* %call3.i.i.i.i.i, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 64)), !dbg !15
+    br label %_Z17do_insert_cv_testI5_TreeEvv.exit
+  
+  _Z17do_insert_cv_testI5_TreeEvv.exit:
+    %_First.sroa.2.0.i.i = phi i32* [ %0, %entry ], [ %call3.i.i.i.i.i, %if.then.i.i.i.i.i ]
+    call void @llvm.dbg.value(metadata i32* %_First.sroa.2.0.i.i, metadata !13, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 64)), !dbg !15
+    call void undef(%class._Tree_const_iterator* null, i32 0, i32* %_First.sroa.2.0.i.i), !dbg !16
+    ret i32 0
+  }
+  
+  declare void @llvm.dbg.value(metadata, metadata, metadata)
+  
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!2, !3, !4, !5}
+  
+  !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 14.0.0 (git@github.com:llvm/llvm-project ffb249520766d4e2ca120c09dae7afa3d64ef81d)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+  !1 = !DIFile(filename: "toolchain10279.cpp", directory: "/home/jmorse")
+  !2 = !{i32 7, !"Dwarf Version", i32 4}
+  !3 = !{i32 2, !"Debug Info Version", i32 3}
+  !4 = !{i32 1, !"wchar_size", i32 4}
+  !5 = !{i32 7, !"uwtable", i32 1}
+  !6 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 52, type: !7, scopeLine: 52, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+  !7 = !DISubroutineType(types: !8)
+  !8 = !{!9}
+  !9 = !DIBasicType(name: "int", size: 128, encoding: DW_ATE_signed)
+  !10 = !DILocalVariable(name: "v1", scope: !11, file: !1, line: 47, type: !9)
+  !11 = distinct !DILexicalBlock(scope: !6)
+  !12 = !DILocation(line: 0, scope: !11)
+  !13 = !DILocalVariable(name: "_First", arg: 1, scope: !14, file: !1, line: 11, type: !9)
+  !14 = distinct !DILexicalBlock(scope: !6)
+  !15 = !DILocation(line: 0, scope: !14)
+  !16 = !DILocation(line: 50, column: 11, scope: !11)
+
+...
+---
+name:            main
+alignment:       16
+tracksRegLiveness: true
+liveins:
+  - { reg: '$rsi' }
+frameInfo:
+  stackSize:       24
+  offsetAdjustment: -24
+  maxAlignment:    1
+  adjustsStack:    true
+  hasCalls:        true
+  maxCallFrameSize: 0
+  cvBytesOfCalleeSavedRegisters: 16
+fixedStack:
+  - { id: 0, type: spill-slot, offset: -24, size: 8, alignment: 8, callee-saved-register: '$rbx' }
+  - { id: 1, type: spill-slot, offset: -16, size: 8, alignment: 16, callee-saved-register: '$r14' }
+machineFunctionInfo: {}
+body:             |
+  bb.0.entry:
+    liveins: $rsi, $r14, $rbx
+  
+    frame-setup PUSH64r killed $r14, implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 16
+    frame-setup PUSH64r killed $rbx, implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 24
+    frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 32
+    CFI_INSTRUCTION offset $rbx, -24
+    CFI_INSTRUCTION offset $r14, -16
+    DBG_PHI $rsi, 2
+    $rbx = MOV64rr $rsi
+    DBG_VALUE 2, $noreg, !10, !DIExpression(), debug-location !12
+    renamable $r14d = XOR32rr undef $r14d, undef $r14d, implicit-def dead $eflags, implicit-def $r14
+    dead $edi = XOR32rr undef $edi, undef $edi, implicit-def dead $eflags, implicit-def $rdi
+    CALL64r undef renamable $rax, csr_64, implicit $rsp, implicit $ssp, implicit killed $rdi, implicit-def $rsp, implicit-def $ssp, implicit-def dead $eax, implicit-def dead $rdx
+    DBG_INSTR_REF 2, 0, !13, !DIExpression(DW_OP_LLVM_fragment, 64, 64), debug-location !15
+    dead $edi = XOR32rr undef $edi, undef $edi, implicit-def dead $eflags, implicit-def $rdi, debug-location !15
+    CALL64r undef renamable $rax, csr_64, implicit $rsp, implicit $ssp, implicit killed $rdi, implicit-def $rsp, implicit-def $ssp, implicit-def dead $al, debug-location !15
+    TEST8rr renamable $r14b, renamable $r14b, implicit-def $eflags, implicit killed $r14
+    JCC_1 %bb.2, 5, implicit $eflags
+  
+  bb.1.if.then.i.i.i.i.i:
+    dead $edi = XOR32rr undef $edi, undef $edi, implicit-def dead $eflags, implicit-def $rdi
+    CALL64r undef renamable $rax, csr_64, implicit $rsp, implicit $ssp, implicit killed $rdi, implicit-def $rsp, implicit-def $ssp, implicit-def $rax, debug-instr-number 3
+    $rbx = MOV64rr killed $rax
+    DBG_INSTR_REF 3, 7, !13, !DIExpression(DW_OP_LLVM_fragment, 64, 64), debug-location !15
+  
+  bb.2._Z17do_insert_cv_testI5_TreeEvv.exit:
+    liveins: $rbx
+  
+    DBG_PHI $rbx, 1
+    DBG_INSTR_REF 1, 0, !13, !DIExpression(DW_OP_LLVM_fragment, 64, 64), debug-location !15
+    dead $edi = XOR32rr undef $edi, undef $edi, implicit-def dead $eflags, implicit-def $rdi, debug-location !16
+    $esi = XOR32rr undef $esi, undef $esi, implicit-def dead $eflags, debug-location !16
+    $rdx = MOV64rr killed $rbx, debug-location !16
+    CALL64r undef renamable $rax, csr_64, implicit $rsp, implicit $ssp, implicit killed $rdi, implicit $esi, implicit killed $rdx, implicit-def $rsp, implicit-def $ssp, debug-location !16
+    $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags
+    $rsp = frame-destroy ADD64ri8 $rsp, 8, implicit-def dead $eflags
+    CFI_INSTRUCTION def_cfa_offset 24
+    $rbx = frame-destroy POP64r implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 16
+    $r14 = frame-destroy POP64r implicit-def $rsp, implicit $rsp
+    CFI_INSTRUCTION def_cfa_offset 8
+    RET64 killed $eax
+
+...