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diff --git a/test/CodeGen/ARM/virtregrewriter-subregliveness.mir b/test/CodeGen/ARM/virtregrewriter-subregliveness.mir
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+# RUN: llc  -o -  -mtriple=thumbv7--windows-gnu -run-pass=greedy -run-pass=virtregrewriter %s | FileCheck %s
+--- |
+  target datalayout = "e-m:w-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+  target triple = "thumbv7--windows-gnu"
+  
+  define void @subregLiveThrough() { ret void }
+  define void @subregNotLiveThrough() { ret void }
+  define void @subregNotLiveThrough2() { ret void }
+
+...
+---
+# Check that we properly recognize that r1 is live through
+# the first subreg copy.
+# That will materialize as an implicit use of the big register
+# on that copy.
+# PR34107.
+#
+# CHECK-LABEL: name: subregLiveThrough
+name:            subregLiveThrough
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gprpair }
+body:             |
+  bb.0:
+    liveins: %r0, %r1
+
+    ; That copy is being coalesced so we should use a KILL
+    ; placeholder. If that's not a kill that means we probably
+    ; not coalescing %0 and %r0_r1 and thus we are not testing
+    ; the problematic code anymore.
+    ;
+    ; CHECK: %r0 = KILL %r0, implicit killed %r0_r1, implicit-def %r0_r1
+    ; CHECK-NEXT: %r1 = KILL %r1, implicit killed %r0_r1
+    undef %0.gsub_0 = COPY %r0
+    %0.gsub_1 = COPY %r1
+    tBX_RET 14, _, implicit %0
+  
+
+...
+
+---
+# Check that we properly recognize that r1 is *not* live through
+# the first subreg copy.
+# CHECK-LABEL: name: subregNotLiveThrough
+name:            subregNotLiveThrough
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gprpair }
+body:             |
+  bb.0:
+    liveins: %r0, %r1
+
+    ; r1 is not live through so check we are not implicitly using
+    ; the big register.
+    ; CHECK: %r0 = KILL %r0, implicit-def %r0_r1
+    ; CHECK-NEXT: tBX_RET
+    undef %0.gsub_0 = COPY %r0
+    tBX_RET 14, _, implicit %0
+  
+
+...
+
+---
+# Check that we properly recognize that r1 is *not* live through
+# the first subreg copy. It is defined by this copy, but is not
+# through.
+# CHECK-LABEL: name: subregNotLiveThrough2
+name:            subregNotLiveThrough2
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gprpair }
+body:             |
+  bb.0:
+    liveins: %r0, %r1
+
+    ; r1 is not live through so check we are not implicitly using
+    ; the big register.
+    ; CHECK: %r0 = KILL %r0, implicit-def %r1, implicit-def %r0_r1
+    ; CHECK-NEXT: tBX_RET
+    undef %0.gsub_0 = COPY %r0, implicit-def %r1
+    tBX_RET 14, _, implicit %0
+  
+
+...