Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -4349,6 +4349,13 @@
   bool MadeIRChange = false;
   if (ShouldLowerDbgDeclare)
     MadeIRChange = LowerDbgDeclare(F);
+  // LowerDbgDeclare calls RemoveRedundantDbgInstrs, but LowerDbgDeclare will
+  // almost never return true when running an assignment tracking build. Take
+  // this opportunity to do some clean up for assignment tracking builds too.
+  if (!MadeIRChange && getEnableAssignmentTracking()) {
+    for (auto &BB : F)
+      RemoveRedundantDbgInstrs(&BB);
+  }
 
   // Iterate while there is work to do.
   unsigned Iteration = 0;
Index: llvm/test/DebugInfo/Generic/assignment-tracking/instcombine/remove-redundant-dbg.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/Generic/assignment-tracking/instcombine/remove-redundant-dbg.ll
@@ -0,0 +1,45 @@
+; RUN: opt -passes=instcombine -S %s -o - -experimental-assignment-tracking \
+; RUN: | FileCheck %s --implicit-check-not="call void @llvm.dbg"
+
+;; Check that instcombine removes redundant debug intrinsics. This has a
+;; significant positive impact on peak memory. CTMark's tramp3d-v4's peak
+;; memory with assignment tracking enabled is reduced by about 15% with this
+;; change.
+
+; CHECK: @llvm.dbg.assign(metadata i32 1
+
+define dso_local void @_Z3funv() local_unnamed_addr !dbg !7 {
+entry:
+   call void @llvm.dbg.assign(metadata i32 undef, metadata !11, metadata !DIExpression(), metadata !13, metadata i32* undef, metadata !DIExpression()), !dbg !14
+   call void @_Z3extv(), !dbg !15
+  call void @llvm.dbg.assign(metadata i32 0, metadata !11, metadata !DIExpression(), metadata !13, metadata i32* undef, metadata !DIExpression()), !dbg !14
+  call void @llvm.dbg.assign(metadata i32 1, metadata !11, metadata !DIExpression(), metadata !13, metadata i32* undef, metadata !DIExpression()), !dbg !14
+  ret void, !dbg !16
+}
+
+declare !dbg !17 dso_local void @_Z3extv() local_unnamed_addr #1
+declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata) #2
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 14.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", directory: "/")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 7, !"uwtable", i32 1}
+!6 = !{!"clang version 14.0.0)"}
+!7 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funv", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !10)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !{!11}
+!11 = !DILocalVariable(name: "a", scope: !7, file: !1, line: 2, type: !12)
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = distinct !DIAssignID()
+!14 = !DILocation(line: 0, scope: !7)
+!15 = !DILocation(line: 2, column: 25, scope: !7)
+!16 = !DILocation(line: 2, column: 32, scope: !7)
+!17 = !DISubprogram(name: "ext", linkageName: "_Z3extv", scope: !1, file: !1, line: 1, type: !8, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !18)
+!18 = !{}