Index: llvm/test/DebugInfo/assignment-tracking/X86/dbg-phi-produces-undef.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/dbg-phi-produces-undef.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/dbg-phi-produces-undef.ll
@@ -16,11 +16,11 @@
 ;;
 ;; exit:
 ;;                  ; <-- Dbg=!1, Stack=!1, Loc=Mem
-;;   memddef 1, !2  ; <-- Dbg=!1, Stack=!2, Loc=Val(undef) XXX
+;;   memddef 1, !2  ; <-- Dbg=!1, Stack=!2, Loc=Val(undef) @HERE
 ;;   call
 ;;   dbgdef !2
 ;;
-;; Check that the dbg.value inserted at XXX is undef because there's no
+;; Check that the dbg.value inserted at @HERE is undef because there's no
 ;; appropriate alternative value to choose.
 
 ; CHECK: bb.0.entry:
@@ -34,7 +34,7 @@
 
 ; CHECK:  bb.2.exit:
 ; CHECK-NEXT: MOV8mi %stack.0.c, 1, $noreg, 0, $noreg, 1
-;; XXX
+;; @HERE
 ; CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[var]], !DIExpression()
 ; CHECK: CALL64pcrel32 @d
 ; CHECK-NEXT: ADJCALLSTACKUP64
Index: llvm/test/DebugInfo/assignment-tracking/X86/loop-sink.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/loop-sink.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/loop-sink.ll
@@ -1,14 +1,16 @@
 ; RUN: llc %s -stop-after=finalize-isel -o - -experimental-assignment-tracking \
-; RUN: | FileCheck %s --implicit-check-not=DBG_VALUE
+; RUN: | FileCheck %s --implicit-check-not=DBG
 
 ;; Tiny loop with a store sunk out of it:
 ;; void e();
 ;; void es(int*);
 ;; int *g;
+;; int getInt();
 ;; int f(int a, int b) {
+;;   int z = getInt();
 ;;   while (g) {
 ;;     e();
-;;     a = b;
+;;     a = z;
 ;;   }
 ;;   es(&a);
 ;;   return a;
@@ -22,14 +24,13 @@
 
 ; CHECK-LABEL: bb.0.entry:
 ; CHECK: DBG_VALUE $edi, $noreg, ![[A]], !DIExpression()
+; CHECK: CALL64pcrel32 @getInt{{.*}}debug-instr-number 1
 
 ; CHECK-LABEL: bb.2.while.body:
-;; It's unfortunate that we see $noreg here -- the vreg use gets lost at some
-;; point by SelectionDAG.
-; CHECK: DBG_VALUE $noreg, $noreg, ![[A]], !DIExpression()
+; CHECK: DBG_INSTR_REF 1, 6, ![[A]], !DIExpression()
 
 ; CHECK-LABEL: bb.3.while.end:
-; CHECK: MOV32mr %stack.0.a.addr, 1, $noreg, 0, $noreg, %0
+; CHECK: MOV32mr %stack.0.a.addr, 1, $noreg, 0, $noreg, %1
 ; CHECK-NEXT: DBG_VALUE %stack.0.a.addr, $noreg, ![[A]], !DIExpression(DW_OP_deref)
 
 target triple = "x86_64-unknown-linux-gnu"
@@ -42,13 +43,14 @@
   %a.addr = alloca i32, align 4, !DIAssignID !18
   call void @llvm.dbg.assign(metadata i1 undef, metadata !16, metadata !DIExpression(), metadata !18, metadata ptr %a.addr, metadata !DIExpression()), !dbg !19
   call void @llvm.dbg.assign(metadata i32 %a, metadata !16, metadata !DIExpression(), metadata !20, metadata ptr %a.addr, metadata !DIExpression()), !dbg !19
+  %z = call i32 @getInt()
   %0 = load ptr, ptr @g, align 8, !dbg !22
   %tobool.not1 = icmp eq ptr %0, null, !dbg !22
   br i1 %tobool.not1, label %while.end, label %while.body, !dbg !27
 
 while.body:                                       ; preds = %entry, %while.body
   tail call void @_Z1ev(), !dbg !28
-  call void @llvm.dbg.assign(metadata i32 %b, metadata !16, metadata !DIExpression(), metadata !20, metadata ptr %a.addr, metadata !DIExpression()), !dbg !19
+  call void @llvm.dbg.assign(metadata i32 %z, metadata !16, metadata !DIExpression(), metadata !20, metadata ptr %a.addr, metadata !DIExpression()), !dbg !19
   %1 = load ptr, ptr @g, align 8, !dbg !22
   %tobool.not = icmp eq ptr %1, null, !dbg !22
   br i1 %tobool.not, label %while.end, label %while.body, !dbg !27, !llvm.loop !30
@@ -58,12 +60,14 @@
   store i32 %storemerge.lcssa, ptr %a.addr, align 4, !DIAssignID !20
   call void @_Z2esPi(ptr noundef nonnull %a.addr), !dbg !35
   %2 = load i32, ptr %a.addr, align 4, !dbg !36
-  ret i32 %2, !dbg !37
+  %r = add i32 %2, %z
+  ret i32 %r, !dbg !37
 }
 
 declare !dbg !38 dso_local void @_Z1ev() local_unnamed_addr #1
 declare !dbg !42 dso_local void @_Z2esPi(ptr noundef) local_unnamed_addr #1
 declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata) #2
+declare dso_local i32 @getInt()
 
 !llvm.dbg.cu = !{!2}
 !llvm.module.flags = !{!7, !8, !9, !10}
Index: llvm/test/DebugInfo/assignment-tracking/X86/mem-loc-frag-fill.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/mem-loc-frag-fill.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/mem-loc-frag-fill.ll
@@ -45,7 +45,7 @@
 ; CHECK: MOV64mr %stack.0.nums, 1, $noreg, 0, $noreg, killed %0
   call void @llvm.dbg.assign(metadata i1 undef, metadata !12, metadata !DIExpression(), metadata !22, metadata ptr %nums, metadata !DIExpression()), !dbg !19
   call void @llvm.dbg.assign(metadata i1 undef, metadata !12, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 32), metadata !22, metadata ptr undef, metadata !DIExpression()), !dbg !19
-; CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[nums]], !DIExpression(DW_OP_deref, DW_OP_LLVM_fragment, 64, 32)
+; CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[nums]], !DIExpression(DW_OP_LLVM_fragment, 64, 32)
 ; CHECK-NEXT: DBG_VALUE %stack.0.nums, $noreg, ![[nums]], !DIExpression(DW_OP_deref, DW_OP_LLVM_fragment, 0, 64)
   tail call void @_Z4stepv(), !dbg !23
   %c = getelementptr inbounds %struct.Nums, ptr %nums, i64 0, i32 2, !dbg !24
Index: llvm/test/DebugInfo/assignment-tracking/X86/nested-loop.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/assignment-tracking/X86/nested-loop.ll
@@ -0,0 +1,367 @@
+; RUN: llc %s -stop-after=finalize-isel -o - -experimental-assignment-tracking \
+; RUN: | FileCheck %s --implicit-check-not=DBG
+
+;; Test a variety of block inputs and lattice configurations for the assignment
+;; tracking analysis (debug-ata).
+
+;; The CFG looks like this:
+;;     entry
+;;     |
+;;     v
+;;     do.body <-----+
+;;     |             |
+;;     V             |
+;;     do.body1 <--+ |
+;;    / \          | |
+;;   /   \         | |
+;;  /     \        | |
+;; v       v       | |
+;; if.then if.else | |
+;;  \      /       | |
+;;   \    /        | |
+;;    \  /         | |
+;;     do.cond ----+ |
+;;     |             |
+;;     v             |
+;;     do.cond4 -----+
+;;     |
+;;     v
+;;     do.end6
+
+;;  Key
+;; ╔═════════════════════╦═══════════════════════════════════════════════════════════════════╗
+;; ║ thing               ║ meaning                                                           ║
+;; ╠═════════════════════╬═══════════════════════════════════════════════════════════════════╣
+;; ║ mem=<!n|phi>        ║ assignment of !n or phi to memory                                 ║
+;; ║ dbg=<!n|phi>        ║ assignment of !n or phi to source variable                        ║
+;; ║ phi                 ║ phi of assignments (operands not traked)*                         ║
+;; ║ loc=<val|mem|none>  ║ location to use is value (implicit location), stack home, or none ║
+;; ╚═════════════════════╩═══════════════════════════════════════════════════════════════════╝
+;;  (*) A phi in the def column represents an assignment made by an untagged store.
+;;
+;; Variable 'a' (!21)
+;; Check initial dbg and mem assignment values are propagated through all blocks.
+;; ╔═════════════╦══════════════════════════╦═════════════════╦══════════════════════════╗
+;; ║ block       ║ in                       ║ def             ║ out                      ║
+;; ╠═════════════╬══════════════════════════╬═════════════════╬══════════════════════════╣
+;; ║ entry       ║                          ║ mem=!63 dbg=!70 ║ mem=!63 dbg=!70 loc=val  ║
+;; ║ do.end6     ║ mem=!63 dbg=!70 loc=val  ║ mem=!63         ║ mem=!63 dbg=!63 loc=mem  ║
+;; ╚═════════════╩══════════════════════════╩═════════════════╩══════════════════════════╝
+;;
+;; Variable 'b' (!22)
+;; Check mem=dbg assignment on branch in nested loop causes a mem=phi (tested by looking
+;; for value-based DBG_VALUE in do.end6).
+;; ╔═════════════╦══════════════════════════╦═════════════════╦══════════════════════════╗
+;; ║ block       ║ in                       ║ def             ║ out                      ║
+;; ╠═════════════╬══════════════════════════╬═════════════════╬══════════════════════════╣
+;; ║ entry       ║                          ║ mem=!65 dbg=!71 ║ mem=!65 dbg=!71 loc=val  ║
+;; ║ if.then     ║ mem=phi dbg=phi loc=none ║ mem=!66 dbg=!66 ║ mem=!66 dbg=!66 loc=mem  ║
+;; ║ do.end6     ║ mem=phi dbg=phi loc=none ║ mem=!65         ║ mem=phi dbg=!65 loc=val  ║
+;; ╚═════════════╩══════════════════════════╩═════════════════╩══════════════════════════╝
+;;
+;; Variable 'c' (!67)
+;; Check initial dbg and mem assignment values are propagated through all blocks, with
+;; dbg defs with the inital assignment ID put in do.cond and do.end6 (variable is always
+;; in memory).
+;; ╔═════════════╦══════════════════════════╦═════════════════╦══════════════════════════╗
+;; ║ block       ║ in                       ║ def             ║ out                      ║
+;; ╠═════════════╬══════════════════════════╬═════════════════╬══════════════════════════╣
+;; ║ entry       ║                          ║ mem=!69 dbg=!69 ║ mem=!69 dbg=!69 loc=mem  ║
+;; ║ do.cond     ║ mem=!69 dbg=!69 loc=mem  ║         dbg=!69 ║ mem=!69 dbg=!69 loc=mem  ║
+;; ║ do.end6     ║ mem=!69 dbg=!69 loc=mem  ║         dbg=!69 ║ mem=!69 dbg=!69 loc=mem  ║
+;; ╚═════════════╩══════════════════════════╩═════════════════╩══════════════════════════╝
+;;
+;; Variable 'd' (!72)
+;; Same as above, except the "if.then" dbg def has been swapped for a dbg=mem def (with
+;; the initial assignment ID) has been placed in if.else.
+;; ╔═════════════╦══════════════════════════╦═════════════════╦══════════════════════════╗
+;; ║ block       ║ in                       ║ def             ║ out                      ║
+;; ╠═════════════╬══════════════════════════╬═════════════════╬══════════════════════════╣
+;; ║ entry       ║                          ║ mem=!74 dbg=!74 ║ mem=!74 dbg=!74 loc=mem  ║
+;; ║ if.else     ║ mem=!74 dbg=!74 loc=mem  ║ mem=!74 dbg=!74 ║ mem=!74 dbg=!74 loc=mem  ║
+;; ║ do.end6     ║ mem=!74 dbg=!74 loc=mem  ║         dbg=!74 ║ mem=!74 dbg=!74 loc=mem  ║
+;; ╚═════════════╩══════════════════════════╩═════════════════╩══════════════════════════╝
+;;
+;; Variable 'e' (!75)
+;; mem defs in entry, if.then and if.else with same ID (!77). Check these join correct
+;; (tested using the dbg defs of the same ID - the memory location is valid at each of
+;; these with that ID).
+;; ╔═════════════╦══════════════════════════╦═════════════════╦══════════════════════════╗
+;; ║ block       ║ in                       ║ def             ║ out                      ║
+;; ╠═════════════╬══════════════════════════╬═════════════════╬══════════════════════════╣
+;; ║ entry       ║                          ║ mem=!77 dbg=!78 ║ mem=!77 dbg=!78 loc=val  ║
+;; ║ do.body     ║ mem=!77 dbg=phi loc=none ║         dbg=!77 ║ mem=!77 dbg=!77 loc=mem  ║
+;; ║ do.body1    ║ mem=!77 dbg=!77 loc=mem  ║         dbg=!77 ║ mem=!77 dbg=!77 loc=mem  ║
+;; ║ if.then     ║ mem=!77 dbg=!77 loc=mem  ║ mem=!77         ║ mem=!77 dbg=!77 loc=mem  ║
+;; ║ if.else     ║ mem=!77 dbg=!77 loc=mem  ║ mem=!77         ║ mem=!77 dbg=!77 loc=mem  ║
+;; ╚═════════════╩══════════════════════════╩═════════════════╩══════════════════════════╝
+;;
+;; Variable 'f' (!79)
+;; mem def in entry and an untagged store in if.else (results in mem=phi, dbg=phi defs).
+;; Use dbg defs in do.body, do.body1, do.cond and do.end6 to check the phi-ness
+;; has been propagated (the memory loc at each is not a valid location). Check the memory
+;; loc is used in if.else after the untagged store.
+;; ╔═════════════╦══════════════════════════╦═════════════════╦══════════════════════════╗
+;; ║ block       ║ in                       ║ def             ║ out                      ║
+;; ╠═════════════╬══════════════════════════╬═════════════════╬══════════════════════════╣
+;; ║ entry       ║                          ║ mem=!81 dbg=!81 ║ mem=!81 dbg=!81 loc=mem  ║
+;; ║ do.body     ║ mem=phi dbg=phi loc=none ║         dbg=!81 ║ mem=phi dbg=!81 loc=val  ║
+;; ║ do.body1    ║ mem=phi dbg=phi loc=none ║         dbg=!81 ║ mem=phi dbg=!81 loc=val  ║
+;; ║ if.else     ║ mem=phi dbg=phi loc=none ║ mem=phi dbg=phi ║ mem=phi dbg=phi loc=mem  ║
+;; ║ do.cond     ║ mem=phi dbg=phi loc=none ║         dbg=!81 ║ mem=phi dbg=!81 loc=val  ║
+;; ║ do.end6     ║ mem=phi dbg=!81 loc=val  ║         dbg=!81 ║ mem=!69 dbg=!81 loc=val  ║
+;; ╚═════════════╩══════════════════════════╩═════════════════╩══════════════════════════╝
+
+; CHECK-DAG: ![[a:[0-9]+]] = !DILocalVariable(name: "a",
+; CHECK-DAG: ![[b:[0-9]+]] = !DILocalVariable(name: "b",
+; CHECK-DAG: ![[c:[0-9]+]] = !DILocalVariable(name: "c",
+; CHECK-DAG: ![[d:[0-9]+]] = !DILocalVariable(name: "d",
+; CHECK-DAG: ![[e:[0-9]+]] = !DILocalVariable(name: "e",
+; CHECK-DAG: ![[f:[0-9]+]] = !DILocalVariable(name: "f",
+
+;; Variables 'c' (!67) and 'd' (!72) are always stack-homed.
+; CHECK:      - { id: 2, name: c.addr, type: default, offset: 0, size: 4, alignment: 4,
+; CHECK-NEXT:     stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+; CHECK-NEXT:     debug-info-variable: '![[c]]', debug-info-expression: '!DIExpression()',
+; CHECK:      - { id: 3, name: d.addr, type: default, offset: 0, size: 4, alignment: 4,
+; CHECK-NEXT:     stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+; CHECK-NEXT:     debug-info-variable: '![[d]]', debug-info-expression: '!DIExpression()',
+
+source_filename = "test.cpp"
+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"
+
+@g_a = dso_local local_unnamed_addr global i32 0, align 4, !dbg !0
+@g_b = dso_local local_unnamed_addr global i32 0, align 4, !dbg !5
+@g_c = dso_local local_unnamed_addr global i32 0, align 4, !dbg !8
+
+define dso_local noundef i32 @_Z3funii(i32 noundef %a, i32 noundef %b) local_unnamed_addr #0 !dbg !17 {
+entry:
+  %a.addr = alloca i32, align 4, !DIAssignID !58 ; VAR:a
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !21, metadata !DIExpression(), metadata !58, metadata ptr %a.addr, metadata !DIExpression()), !dbg !27 ; VAR:a
+  %b.addr = alloca i32, align 4, !DIAssignID !64 ; VAR:b
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !22, metadata !DIExpression(), metadata !64, metadata ptr %b.addr, metadata !DIExpression()), !dbg !27 ; VAR:b
+  %c.addr = alloca i32, align 4, !DIAssignID !68 ; VAR:c
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !67, metadata !DIExpression(), metadata !68, metadata ptr %c.addr, metadata !DIExpression()), !dbg !27 ; VAR:c
+  %d.addr = alloca i32, align 4, !DIAssignID !73 ; VAR:d
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !72, metadata !DIExpression(), metadata !73, metadata ptr %d.addr, metadata !DIExpression()), !dbg !27 ; VAR:d
+  %e.addr = alloca i32, align 4, !DIAssignID !76 ; VAR:e
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !75, metadata !DIExpression(), metadata !76, metadata ptr %e.addr, metadata !DIExpression()), !dbg !27 ; VAR:e
+  %f.addr = alloca i32, align 4, !DIAssignID !80 ; VAR:f
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !79, metadata !DIExpression(), metadata !80, metadata ptr %f.addr, metadata !DIExpression()), !dbg !27 ; VAR:f
+  store i32 1, ptr %a.addr, !DIAssignID !70 ; VAR:a
+  call void @llvm.dbg.assign(metadata i32 1, metadata !21, metadata !DIExpression(), metadata !70, metadata ptr %a.addr, metadata !DIExpression()), !dbg !27 ; VAR:a
+  store i32 2, ptr %b.addr, !DIAssignID !71 ; VAR:b
+  call void @llvm.dbg.assign(metadata i32 2, metadata !22, metadata !DIExpression(), metadata !71, metadata ptr %b.addr, metadata !DIExpression()), !dbg !27 ; VAR:b
+  store i32 9, ptr %e.addr, !DIAssignID !78 ; VAR:e
+  call void @llvm.dbg.assign(metadata i32 9, metadata !75, metadata !DIExpression(), metadata !78, metadata ptr %e.addr, metadata !DIExpression()), !dbg !27 ; VAR:c
+  store i32 3, ptr %a.addr, !DIAssignID !63 ; VAR:a
+  store i32 4, ptr %b.addr, !DIAssignID !65 ; VAR:b
+  store i32 5, ptr %c.addr, !DIAssignID !69 ; VAR:c
+  call void @llvm.dbg.assign(metadata i32 5, metadata !67, metadata !DIExpression(), metadata !69, metadata ptr %c.addr, metadata !DIExpression()), !dbg !27 ; VAR:c
+  store i32 6, ptr %d.addr, !DIAssignID !74 ; VAR:d
+  call void @llvm.dbg.assign(metadata i32 6, metadata !72, metadata !DIExpression(), metadata !74, metadata ptr %d.addr, metadata !DIExpression()), !dbg !27 ; VAR:d
+  store i32 8, ptr %e.addr, !DIAssignID !77 ; VAR:e
+  store i32 11, ptr %f.addr, !DIAssignID !81 ; VAR:f
+  call void @llvm.dbg.assign(metadata i32 11, metadata !79, metadata !DIExpression(), metadata !81, metadata ptr %f.addr, metadata !DIExpression()), !dbg !27 ; VAR:f
+  br label %do.body, !dbg !24
+; CHECK-LABEL: bb.0.entry:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK-NEXT:    DBG_VALUE %stack.0.a.addr, $noreg, ![[a]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    DBG_VALUE %stack.1.b.addr, $noreg, ![[b]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    DBG_VALUE %stack.4.e.addr, $noreg, ![[e]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    DBG_VALUE %stack.5.f.addr, $noreg, ![[f]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    MOV32mi %stack.0.a.addr, 1, $noreg, 0, $noreg, 3
+; CHECK-NEXT:    DBG_VALUE 1, $noreg, ![[a]], !DIExpression()
+; CHECK-NEXT:    MOV32mi %stack.1.b.addr, 1, $noreg, 0, $noreg, 4
+; CHECK-NEXT:    DBG_VALUE 2, $noreg, ![[b]], !DIExpression()
+; CHECK-NEXT:    MOV32mi %stack.2.c.addr, 1, $noreg, 0, $noreg, 5
+; CHECK-NEXT:    MOV32mi %stack.3.d.addr, 1, $noreg, 0, $noreg, 6
+; CHECK-NEXT:    MOV32mi %stack.4.e.addr, 1, $noreg, 0, $noreg, 8
+; CHECK-NEXT:    DBG_VALUE 9, $noreg, ![[e]], !DIExpression()
+; CHECK-NEXT:    MOV32mi %stack.5.f.addr, 1, $noreg, 0, $noreg, 11
+; CHECK-NEXT: {{^ *$}}
+
+do.body:                                          ; preds = %do.cond4, %entry
+  call void @llvm.dbg.assign(metadata i32 8, metadata !75, metadata !DIExpression(), metadata !77, metadata ptr %e.addr, metadata !DIExpression()), !dbg !27 ; VAR:e
+  call void @llvm.dbg.assign(metadata i32 11, metadata !79, metadata !DIExpression(), metadata !81, metadata ptr %f.addr, metadata !DIExpression()), !dbg !27 ; VAR:f
+  %.pre10 = load i32, ptr @g_a, align 4, !dbg !27
+  br label %do.body1, !dbg !34
+; CHECK-LABEL: bb.1.do.body:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK-NEXT:    DBG_VALUE %stack.4.e.addr, $noreg, ![[e]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    DBG_VALUE 11, $noreg, ![[f]], !DIExpression()
+; CHECK-NEXT:    %0:gr32 = MOV32rm $rip, 1, $noreg, @g_a, $noreg
+; CHECK-NEXT: {{^ *$}}
+
+do.body1:                                         ; preds = %do.cond, %do.body
+  %0 = phi i32 [ %.pre10, %do.body ], [ %1, %do.cond ], !dbg !27
+  call void @llvm.dbg.assign(metadata i32 8, metadata !75, metadata !DIExpression(), metadata !77, metadata ptr %e.addr, metadata !DIExpression()), !dbg !27 ; VAR:e
+  call void @llvm.dbg.assign(metadata i32 11, metadata !79, metadata !DIExpression(), metadata !81, metadata ptr %f.addr, metadata !DIExpression()), !dbg !27 ; VAR:f
+  %tobool.not = icmp eq i32 %0, 0, !dbg !27
+  br i1 %tobool.not, label %if.else, label %if.then, !dbg !35
+; CHECK-LABEL: bb.2.do.body1:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK:         DBG_VALUE %stack.4.e.addr, $noreg, ![[e]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    DBG_VALUE 11, $noreg, ![[f]], !DIExpression()
+; CHECK:         JMP_1
+; CHECK-NEXT: {{^ *$}}
+
+if.then:                                          ; preds = %do.body1
+  %.pre = load i32, ptr @g_a, align 4, !dbg !27
+  store i32 %.pre, ptr %b.addr, !DIAssignID !66 ; VAR:b
+  call void @llvm.dbg.assign(metadata i32 %.pre, metadata !22, metadata !DIExpression(), metadata !66, metadata ptr %b.addr, metadata !DIExpression()), !dbg !27 ; VAR:b
+  store i32 8, ptr %e.addr, !DIAssignID !77 ; VAR:e
+  br label %do.cond, !dbg !39
+; CHECK-LABEL: bb.3.if.then:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK-NEXT:    %5:gr32 = MOV32rm
+; CHECK-NEXT:    MOV32mr %stack.1.b.addr, 1, $noreg, 0, $noreg, killed %5
+; CHECK-NEXT:    DBG_VALUE %stack.1.b.addr, $noreg, ![[b]], !DIExpression(DW_OP_deref
+; CHECK-NEXT:    MOV32mi %stack.4.e.addr, 1, $noreg, 0, $noreg, 8
+; CHECK-NEXT:    DBG_VALUE %stack.4.e.addr, $noreg, ![[e]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    JMP_1 %bb.5
+; CHECK-NEXT: {{^ *$}}
+
+if.else:                                          ; preds = %do.body1
+  store i32 6, ptr %d.addr, !DIAssignID !74 ; VAR:d
+  call void @llvm.dbg.assign(metadata i32 6, metadata !72, metadata !DIExpression(), metadata !74, metadata ptr %d.addr, metadata !DIExpression()), !dbg !27 ; VAR:d
+  store i32 8, ptr %e.addr, !DIAssignID !77 ; VAR:e
+  store i32 10, ptr %f.addr ; VAR:f
+  br label %do.cond
+; CHECK-LABEL: bb.4.if.else:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK-NEXT:    MOV32mi %stack.3.d.addr, 1, $noreg, 0, $noreg, 6
+; CHECK-NEXT:    MOV32mi %stack.4.e.addr, 1, $noreg, 0, $noreg, 8
+; CHECK-NEXT:    DBG_VALUE %stack.4.e.addr, $noreg, ![[e]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    MOV32mi %stack.5.f.addr, 1, $noreg, 0, $noreg, 10
+; CHECK-NEXT:    DBG_VALUE %stack.5.f.addr, $noreg, !36, !DIExpression(DW_OP_deref)
+; CHECK-NEXT: {{^ *$}}
+
+do.cond:                                          ; preds = %if.then, %if.else
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !67, metadata !DIExpression(), metadata !69, metadata ptr %c.addr, metadata !DIExpression()), !dbg !27 ; VAR:c
+  call void @llvm.dbg.assign(metadata i32 11, metadata !79, metadata !DIExpression(), metadata !81, metadata ptr %f.addr, metadata !DIExpression()), !dbg !27 ; VAR:f
+  %1 = load i32, ptr @g_b, align 4, !dbg !43
+  %tobool3.not = icmp eq i32 %1, 0, !dbg !43
+  br i1 %tobool3.not, label %do.cond4, label %do.body1, !dbg !44, !llvm.loop !45
+; CHECK-LABEL: bb.5.do.cond:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK-NEXT:    DBG_VALUE 11, $noreg, ![[f]], !DIExpression()
+; CHECK:      {{^ *$}}
+
+do.cond4:                                         ; preds = %do.cond
+  %2 = load i32, ptr @g_c, align 4, !dbg !48
+  %tobool5.not = icmp eq i32 %2, 0, !dbg !48
+  br i1 %tobool5.not, label %do.end6, label %do.body, !dbg !49, !llvm.loop !50
+; CHECK-LABEL: bb.6.do.cond4:
+; CHECK-NEXT: successors
+; CHECK-NEXT: {{^ *$}}
+; CHECK-NOT:     DBG
+; CHECK: {{^ *$}}
+
+do.end6:                                          ; preds = %do.cond4
+  call void @llvm.dbg.assign(metadata i32 3, metadata !21, metadata !DIExpression(), metadata !63, metadata ptr %a.addr, metadata !DIExpression()), !dbg !27; VAR:a
+  call void @llvm.dbg.assign(metadata i32 4, metadata !22, metadata !DIExpression(), metadata !65, metadata ptr %b.addr, metadata !DIExpression()), !dbg !27 ; VAR:b
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !67, metadata !DIExpression(), metadata !69, metadata ptr %c.addr, metadata !DIExpression()), !dbg !27 ; VAR:c
+  call void @llvm.dbg.assign(metadata i32 6, metadata !72, metadata !DIExpression(), metadata !74, metadata ptr %d.addr, metadata !DIExpression()), !dbg !27 ; VAR:d
+  call void @llvm.dbg.assign(metadata i32 11, metadata !79, metadata !DIExpression(), metadata !81, metadata ptr %f.addr, metadata !DIExpression()), !dbg !27 ; VAR:f
+  ret i32 0, !dbg !53
+; CHECK-LABEL: bb.7.do.end6:
+; CHECK-NEXT:    DBG_VALUE %stack.0.a.addr, $noreg, ![[a]], !DIExpression(DW_OP_deref)
+; CHECK-NEXT:    DBG_VALUE 4, $noreg, ![[b]], !DIExpression()
+; CHECK-NEXT:    DBG_VALUE 11, $noreg, ![[f]], !DIExpression()
+}
+
+declare !dbg !54 void @_Z4calli(i32 noundef) local_unnamed_addr #1
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!10, !11, !12, !13, !14, !15}
+!llvm.ident = !{!16}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "g_a", scope: !2, file: !3, line: 1, type: !7, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 16.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "test.cpp", directory: "/")
+!4 = !{!0, !5, !8}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "g_b", scope: !2, file: !3, line: 1, type: !7, isLocal: false, isDefinition: true)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = !DIGlobalVariableExpression(var: !9, expr: !DIExpression())
+!9 = distinct !DIGlobalVariable(name: "g_c", scope: !2, file: !3, line: 1, type: !7, isLocal: false, isDefinition: true)
+!10 = !{i32 7, !"Dwarf Version", i32 5}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{i32 8, !"PIC Level", i32 2}
+!14 = !{i32 7, !"PIE Level", i32 2}
+!15 = !{i32 7, !"uwtable", i32 2}
+!16 = !{!"clang version 16.0.0"}
+!17 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funii", scope: !3, file: !3, line: 3, type: !18, scopeLine: 3, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !20)
+!18 = !DISubroutineType(types: !19)
+!19 = !{!7, !7, !7}
+!20 = !{!21, !22}
+!21 = !DILocalVariable(name: "a", arg: 1, scope: !17, file: !3, line: 3, type: !7)
+!22 = !DILocalVariable(name: "b", arg: 2, scope: !17, file: !3, line: 3, type: !7)
+!23 = !DILocation(line: 0, scope: !17)
+!24 = !DILocation(line: 4, column: 3, scope: !17)
+!25 = !DILocation(line: 5, column: 5, scope: !26)
+!26 = distinct !DILexicalBlock(scope: !17, file: !3, line: 4, column: 6)
+!27 = !DILocation(line: 7, column: 11, scope: !28)
+!28 = distinct !DILexicalBlock(scope: !29, file: !3, line: 7, column: 11)
+!29 = distinct !DILexicalBlock(scope: !26, file: !3, line: 6, column: 8)
+!34 = !DILocation(line: 6, column: 5, scope: !26)
+!35 = !DILocation(line: 7, column: 11, scope: !29)
+!36 = !DILocation(line: 8, column: 11, scope: !37)
+!37 = distinct !DILexicalBlock(scope: !28, file: !3, line: 7, column: 16)
+!38 = !DILocation(line: 9, column: 9, scope: !37)
+!39 = !DILocation(line: 10, column: 7, scope: !37)
+!40 = !DILocation(line: 11, column: 11, scope: !41)
+!41 = distinct !DILexicalBlock(scope: !28, file: !3, line: 10, column: 14)
+!42 = !DILocation(line: 0, scope: !28)
+!43 = !DILocation(line: 13, column: 14, scope: !26)
+!44 = !DILocation(line: 13, column: 5, scope: !29)
+!45 = distinct !{!45, !34, !46, !47}
+!46 = !DILocation(line: 13, column: 17, scope: !26)
+!47 = !{!"llvm.loop.mustprogress"}
+!48 = !DILocation(line: 14, column: 12, scope: !17)
+!49 = !DILocation(line: 14, column: 3, scope: !26)
+!50 = distinct !{!50, !24, !51, !47}
+!51 = !DILocation(line: 14, column: 15, scope: !17)
+!52 = !DILocation(line: 15, column: 12, scope: !17)
+!53 = !DILocation(line: 15, column: 3, scope: !17)
+!54 = !DISubprogram(name: "call", linkageName: "_Z4calli", scope: !3, file: !3, line: 2, type: !55, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !57)
+!55 = !DISubroutineType(types: !56)
+!56 = !{null, !7}
+!57 = !{}
+!58 = distinct !DIAssignID()
+!59 = !DILocalVariable(name: "Arr", scope: !17, file: !3, line: 4, type: !60)
+!60 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, size: 96, elements: !61)
+!61 = !{!62}
+!62 = !DISubrange(count: 3)
+!63 = distinct !DIAssignID()
+!64 = distinct !DIAssignID()
+!65 = distinct !DIAssignID()
+!66 = distinct !DIAssignID()
+!67 = !DILocalVariable(name: "c", scope: !17, file: !3, line: 3, type: !7)
+!68 = distinct !DIAssignID()
+!69 = distinct !DIAssignID()
+!70 = distinct !DIAssignID()
+!71 = distinct !DIAssignID()
+!72 = !DILocalVariable(name: "d", scope: !17, file: !3, line: 3, type: !7)
+!73 = distinct !DIAssignID()
+!74 = distinct !DIAssignID()
+!75 = !DILocalVariable(name: "e", scope: !17, file: !3, line: 3, type: !7)
+!76 = distinct !DIAssignID()
+!77 = distinct !DIAssignID()
+!78 = distinct !DIAssignID()
+!79 = !DILocalVariable(name: "f", scope: !17, file: !3, line: 3, type: !7)
+!80 = distinct !DIAssignID()
+!81 = distinct !DIAssignID()
Index: llvm/test/DebugInfo/assignment-tracking/X86/order-of-defs.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/order-of-defs.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/order-of-defs.ll
@@ -8,10 +8,10 @@
 ; CHECK-DAG: ![[B:[0-9]+]] = !DILocalVariable(name: "b",
 ; CHECK-DAG: ![[C:[0-9]+]] = !DILocalVariable(name: "c",
 
-; CHECK:      DBG_VALUE $esi, $noreg, ![[B]], !DIExpression(), debug-location !20
-; CHECK-NEXT: DBG_VALUE $edx, $noreg, ![[C]], !DIExpression(), debug-location !20
-; CHECK-NEXT: DBG_VALUE $esi, $noreg, ![[A]], !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !20
-; CHECK-NEXT: DBG_VALUE $edx, $noreg, ![[A]], !DIExpression(DW_OP_LLVM_fragment, 32, 32), debug-location !20
+; CHECK:      DBG_VALUE $esi, $noreg, ![[B]], !DIExpression()
+; CHECK-NEXT: DBG_VALUE $edx, $noreg, ![[C]], !DIExpression()
+; CHECK-NEXT: DBG_VALUE $esi, $noreg, ![[A]], !DIExpression(DW_OP_LLVM_fragment, 0, 32)
+; CHECK-NEXT: DBG_VALUE $edx, $noreg, ![[A]], !DIExpression(DW_OP_LLVM_fragment, 32, 32)
 
 target triple = "x86_64-unknown-linux-gnu"
 
Index: llvm/test/DebugInfo/assignment-tracking/X86/remove-redundant-defs-to-prevent-reordering.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/remove-redundant-defs-to-prevent-reordering.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/remove-redundant-defs-to-prevent-reordering.ll
@@ -17,7 +17,7 @@
 ;;   a += b;
 ;;   return a;
 ;; }
-;; An `dbg.assign(undef, ...)` has been added by hand in if.end.
+;; A `dbg.assign(undef, ...)` has been added by hand in if.end.
 
 ;; For some variable we generate:
 ;;     %inc = add nuw nsw i32 %i.0128, 1
Index: llvm/test/DebugInfo/assignment-tracking/X86/remove-undef-fragment.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/remove-undef-fragment.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/remove-undef-fragment.ll
@@ -67,9 +67,9 @@
 
 define void @_Z1kv({ <2 x float>, <2 x float> } %call, <2 x float> %0, float %n.sroa.6.8.vec.extract) !dbg !7 {
 entry:
-  %call1 = tail call { <2 x float>, <2 x float> } undef(), !dbg !13
+  %call1 = tail call { <2 x float>, <2 x float> } poison(), !dbg !13
   %1 = extractvalue { <2 x float>, <2 x float> } %call, 1
-  %add.i = fadd float undef, 0.000000e+00
+  %add.i = fadd float poison, 0.000000e+00
   call void @llvm.dbg.assign(metadata float %add.i, metadata !11, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 32), metadata !14, metadata ptr undef, metadata !DIExpression()), !dbg !15
   %n.sroa.6.8.vec.extract2 = extractelement <2 x float> %0, i64 0
   %add4.i = fadd float %n.sroa.6.8.vec.extract, 0.000000e+00
@@ -77,7 +77,7 @@
   call void @llvm.dbg.assign(metadata float %add4.i, metadata !11, metadata !DIExpression(DW_OP_LLVM_fragment, 64, 32), metadata !16, metadata ptr undef, metadata !DIExpression()), !dbg !15
   %add.i23 = fadd float 0.000000e+00, 0.000000e+00
   %ah.sroa.0.0.vec.insert = insertelement <2 x float> zeroinitializer, float %add4.i, i64 0
-  tail call void undef(<2 x float> zeroinitializer, <2 x float> zeroinitializer, <2 x float> %ah.sroa.0.0.vec.insert, <2 x float> zeroinitializer)
+  tail call void poison(<2 x float> zeroinitializer, <2 x float> zeroinitializer, <2 x float> %ah.sroa.0.0.vec.insert, <2 x float> zeroinitializer)
   ret void
 }
 
Index: llvm/test/DebugInfo/assignment-tracking/X86/untagged-store-frag.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/untagged-store-frag.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/untagged-store-frag.ll
@@ -34,6 +34,10 @@
 ; CHECK-NEXT:   MOV32mr %stack.0.a.addr, 1, $noreg, 4, $noreg, %1 :: (store (s32) into %ir.add.ptr, align 8)
 ; CHECK-NEXT: DBG_VALUE %stack.0.a.addr, $noreg, ![[A]], !DIExpression(DW_OP_deref, DW_OP_LLVM_fragment, 32, 32)
 
+;; NOTE: The second and third DBG_VALUE combined make the first redundant. If
+;; removeRedundantDbgInstrs gets smarter, add an instruction between the first
+;; dbg.assign and the subsequent dbg.value.
+
 target triple = "x86_64-unknown-linux-gnu"
 
 define dso_local noundef i64 @_Z1fl(i64 noundef %a, i32 %b) #0 !dbg !8 {
Index: llvm/test/DebugInfo/assignment-tracking/X86/use-known-value-at-early-mem-def.ll
===================================================================
--- llvm/test/DebugInfo/assignment-tracking/X86/use-known-value-at-early-mem-def.ll
+++ llvm/test/DebugInfo/assignment-tracking/X86/use-known-value-at-early-mem-def.ll
@@ -2,7 +2,7 @@
 ; RUN:    -experimental-assignment-tracking  \
 ; RUN: | FileCheck %s --implicit-check-not=DBG_VALUE
 
-;; Check that sandwitching instructions between a linked store and dbg.assign
+;; Check that sandwiching instructions between a linked store and dbg.assign
 ;; results in a dbg.value(prev_value) being inserted at the store, and a
 ;; dbg.value(deref) at the dbg.assign.