Index: llvm/lib/CodeGen/RegisterCoalescer.cpp
===================================================================
--- llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -3866,7 +3866,7 @@
 copyCoalesceWorkList(MutableArrayRef<MachineInstr*> CurrList) {
   bool Progress = false;
   for (unsigned i = 0, e = CurrList.size(); i != e; ++i) {
-    if (!CurrList[i])
+    if (!CurrList[i] || !CurrList[i]->getParent())
       continue;
     // Skip instruction pointers that have already been erased, for example by
     // dead code elimination.
Index: llvm/test/CodeGen/AArch64/avoid-coalescing-erased-instructions.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/avoid-coalescing-erased-instructions.mir
@@ -0,0 +1,234 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=aarch64-arm-none-eabi -o - %s \
+# RUN: -run-pass simple-register-coalescing | FileCheck %s
+--- |
+  target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+  target triple = "aarch64-arm-none-eabi"
+
+  @u = common dso_local local_unnamed_addr global i32 0, align 4
+  @r = common dso_local local_unnamed_addr global i32 0, align 4
+  @q = common dso_local local_unnamed_addr global i32 0, align 4
+
+  define dso_local i32 @s() local_unnamed_addr {
+    ret i32 0
+  }
+...
+---
+name:            s
+alignment:       4
+body:             |
+  ; CHECK-LABEL: name: s
+  ; CHECK: bb.0:
+  ; CHECK:   successors: %bb.2(0x40000000), %bb.1(0x40000000)
+  ; CHECK:   [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 841054
+  ; CHECK:   dead $wzr = SUBSWri undef %2:gpr32sp, 2, 0, implicit-def $nzcv
+  ; CHECK:   Bcc 13, %bb.2, implicit killed $nzcv
+  ; CHECK: bb.1:
+  ; CHECK:   successors: %bb.7(0x80000000)
+  ; CHECK:   [[COPY:%[0-9]+]]:gpr32 = COPY $wzr
+  ; CHECK:   [[COPY1:%[0-9]+]]:gpr32 = COPY $wzr
+  ; CHECK:   [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 841054
+  ; CHECK:   B %bb.7
+  ; CHECK: bb.2:
+  ; CHECK:   successors: %bb.4(0x40000000), %bb.3(0x40000000)
+  ; CHECK:   [[ADRP:%[0-9]+]]:gpr64common = ADRP target-flags(aarch64-page) @u
+  ; CHECK:   [[LDRWui:%[0-9]+]]:gpr32common = LDRWui [[ADRP]], target-flags(aarch64-pageoff, aarch64-nc) @u
+  ; CHECK:   [[ADRP1:%[0-9]+]]:gpr64common = ADRP target-flags(aarch64-page) @r
+  ; CHECK:   [[LDRWui1:%[0-9]+]]:gpr32 = LDRWui [[ADRP1]], target-flags(aarch64-pageoff, aarch64-nc) @r
+  ; CHECK:   dead $wzr = SUBSWri [[LDRWui]], 0, 0, implicit-def $nzcv
+  ; CHECK:   [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[COPY]], [[LDRWui1]], 0, implicit killed $nzcv
+  ; CHECK:   [[COPY2:%[0-9]+]]:gpr32 = COPY $wzr
+  ; CHECK:   CBNZW $wzr, %bb.4
+  ; CHECK:   B %bb.3
+  ; CHECK: bb.3:
+  ; CHECK:   successors: %bb.15(0x80000000)
+  ; CHECK:   [[SDIVWr:%[0-9]+]]:gpr32 = SDIVWr [[COPY2]], [[COPY]]
+  ; CHECK:   [[MSUBWrrr:%[0-9]+]]:gpr32 = MSUBWrrr [[SDIVWr]], [[COPY]], [[COPY2]]
+  ; CHECK:   [[ADDWrr:%[0-9]+]]:gpr32 = nsw ADDWrr [[MSUBWrrr]], [[CSELWr]]
+  ; CHECK:   [[ADRP2:%[0-9]+]]:gpr64common = ADRP target-flags(aarch64-page) @q
+  ; CHECK:   STRWui [[ADDWrr]], [[ADRP2]], target-flags(aarch64-pageoff, aarch64-nc) @q :: (store 4 into @q)
+  ; CHECK:   B %bb.15
+  ; CHECK: bb.4:
+  ; CHECK:   successors: %bb.6(0x40000000), %bb.5(0x40000000)
+  ; CHECK:   CBNZW $wzr, %bb.6
+  ; CHECK:   B %bb.5
+  ; CHECK: bb.5:
+  ; CHECK:   successors: %bb.6(0x80000000)
+  ; CHECK:   B %bb.6
+  ; CHECK: bb.6:
+  ; CHECK:   successors: %bb.7(0x80000000)
+  ; CHECK: bb.7:
+  ; CHECK:   successors: %bb.8(0x80000000)
+  ; CHECK: bb.8:
+  ; CHECK:   successors: %bb.9(0x40000000), %bb.8(0x40000000)
+  ; CHECK:   CBNZW $wzr, %bb.8
+  ; CHECK:   B %bb.9
+  ; CHECK: bb.9:
+  ; CHECK:   successors: %bb.14(0x40000000), %bb.10(0x40000000)
+  ; CHECK:   CBNZW $wzr, %bb.14
+  ; CHECK:   B %bb.10
+  ; CHECK: bb.10:
+  ; CHECK:   successors: %bb.15(0x40000000), %bb.11(0x40000000)
+  ; CHECK:   CBNZW $wzr, %bb.15
+  ; CHECK:   B %bb.11
+  ; CHECK: bb.11:
+  ; CHECK:   successors: %bb.14(0x40000000), %bb.12(0x40000000)
+  ; CHECK:   CBNZW $wzr, %bb.14
+  ; CHECK:   B %bb.12
+  ; CHECK: bb.12:
+  ; CHECK:   successors: %bb.14(0x40000000), %bb.13(0x40000000)
+  ; CHECK:   CBZW $wzr, %bb.14
+  ; CHECK: bb.13:
+  ; CHECK:   successors: %bb.3(0x80000000)
+  ; CHECK:   [[DEF:%[0-9]+]]:gpr32 = IMPLICIT_DEF
+  ; CHECK:   B %bb.3
+  ; CHECK: bb.14:
+  ; CHECK:   successors: %bb.3(0x80000000)
+  ; CHECK:   ADJCALLSTACKDOWN 0, 0, implicit-def dead $sp, implicit $sp
+  ; CHECK:   ADJCALLSTACKUP 0, 0, implicit-def dead $sp, implicit $sp
+  ; CHECK:   B %bb.3
+  ; CHECK: bb.15:
+  ; CHECK:   $w0 = COPY $wzr
+  ; CHECK:   RET_ReallyLR implicit killed $w0
+  bb.0:
+    successors: %bb.2, %bb.1
+
+    %13:gpr32 = MOVi32imm 841054
+    %0:gpr32 = COPY %13
+    dead $wzr = SUBSWri undef %16:gpr32sp, 2, 0, implicit-def $nzcv
+    Bcc 13, %bb.2, implicit killed $nzcv
+
+  bb.1:
+    successors: %bb.7
+
+    %14:gpr32all = COPY $wzr
+    %1:gpr32all = COPY killed %14
+    %48:gpr32all = COPY %1
+    %49:gpr32all = COPY killed %1
+    %50:gpr32all = COPY killed %0
+    B %bb.7
+
+  bb.2:
+    successors: %bb.4, %bb.3
+
+    %18:gpr64common = ADRP target-flags(aarch64-page) @u
+    %19:gpr32common = LDRWui killed %18, target-flags(aarch64-pageoff, aarch64-nc) @u
+    %20:gpr64common = ADRP target-flags(aarch64-page) @r
+    %21:gpr32 = LDRWui killed %20, target-flags(aarch64-pageoff, aarch64-nc) @r
+    dead $wzr = SUBSWri killed %19, 0, 0, implicit-def $nzcv
+    %23:gpr32 = CSELWr killed %13, killed %21, 0, implicit killed $nzcv
+    %24:gpr32 = COPY $wzr
+    %17:gpr32all = COPY %24
+    %2:gpr32all = COPY killed %23
+    %42:gpr32 = COPY %0
+    %43:gpr32 = COPY %17
+    %44:gpr32 = COPY %2
+    %45:gpr32all = COPY killed %0
+    %46:gpr32all = COPY killed %17
+    %47:gpr32all = COPY killed %2
+    CBNZW killed %24, %bb.4
+    B %bb.3
+
+  bb.3:
+    successors: %bb.14
+
+    %5:gpr32 = COPY killed %44
+    %4:gpr32 = COPY killed %43
+    %3:gpr32 = COPY killed %42
+    %37:gpr32 = SDIVWr %4, %3
+    %39:gpr32 = MSUBWrrr killed %37, %3, %4
+    %40:gpr32 = nsw ADDWrr killed %39, %5
+    %41:gpr64common = ADRP target-flags(aarch64-page) @q
+    STRWui killed %40, killed %41, target-flags(aarch64-pageoff, aarch64-nc) @q :: (store 4 into @q)
+    %45:gpr32all = COPY killed %3
+    %46:gpr32all = COPY killed %4
+    %47:gpr32all = COPY killed %5
+    B %bb.14
+
+  bb.4:
+    successors: %bb.6, %bb.5
+
+    %8:gpr32all = COPY killed %47
+    %7:gpr32all = COPY killed %46
+    %6:gpr32all = COPY killed %45
+    %25:gpr32 = COPY $wzr
+    CBNZW killed %25, %bb.6
+    B %bb.5
+
+  bb.5:
+    successors: %bb.6
+
+    B %bb.6
+
+  bb.6:
+    successors: %bb.7
+
+    %48:gpr32all = COPY killed %6
+    %49:gpr32all = COPY killed %7
+    %50:gpr32all = COPY killed %8
+
+  bb.7:
+    successors: %bb.8
+
+    %11:gpr32all = COPY killed %50
+    %10:gpr32all = COPY killed %49
+    %9:gpr32all = COPY killed %48
+
+  bb.8:
+    successors: %bb.9, %bb.8
+
+    %27:gpr32 = COPY $wzr
+    CBNZW killed %27, %bb.8
+    B %bb.9
+
+  bb.9:
+    successors: %bb.13, %bb.10
+
+    %28:gpr32 = COPY $wzr
+    CBNZW killed %28, %bb.13
+    B %bb.10
+
+  bb.10:
+    successors: %bb.14, %bb.11
+
+    %29:gpr32 = COPY $wzr
+    CBNZW killed %29, %bb.14
+    B %bb.11
+
+  bb.11:
+    successors: %bb.13, %bb.12
+
+    %32:gpr32 = COPY $wzr
+    CBNZW killed %32, %bb.13
+    B %bb.12
+
+  bb.12:
+    successors: %bb.13, %bb.15
+
+    %33:gpr32 = COPY $wzr
+    CBZW killed %33, %bb.13
+
+  bb.15:
+    successors: %bb.3
+
+    %42:gpr32 = COPY killed %9
+    %43:gpr32 = IMPLICIT_DEF
+    %44:gpr32 = COPY killed %11
+    B %bb.3
+
+  bb.13:
+    successors: %bb.3
+
+    ADJCALLSTACKDOWN 0, 0, implicit-def dead $sp, implicit $sp
+    ADJCALLSTACKUP 0, 0, implicit-def dead $sp, implicit $sp
+    %42:gpr32 = COPY killed %9
+    %43:gpr32 = COPY killed %10
+    %44:gpr32 = COPY killed %11
+    B %bb.3
+
+  bb.14:
+    %30:gpr32all = COPY $wzr
+    $w0 = COPY killed %30
+    RET_ReallyLR implicit killed $w0
+
+...