Index: llvm/include/llvm/CodeGen/AntiDepBreaker.h
===================================================================
--- llvm/include/llvm/CodeGen/AntiDepBreaker.h
+++ llvm/include/llvm/CodeGen/AntiDepBreaker.h
@@ -55,13 +55,20 @@
   /// Finish anti-dep breaking for a basic block.
   virtual void FinishBlock() = 0;
 
-  /// Update DBG_VALUE if dependency breaker is updating
+  /// Update DBG_VALUE or DBG_PHI if dependency breaker is updating
   /// other machine instruction to use NewReg.
   void UpdateDbgValue(MachineInstr &MI, unsigned OldReg, unsigned NewReg) {
-    assert(MI.isDebugValue() && "MI is not DBG_VALUE!");
-    if (MI.getDebugOperand(0).isReg() &&
-        MI.getDebugOperand(0).getReg() == OldReg)
-      MI.getDebugOperand(0).setReg(NewReg);
+    if (MI.isDebugValue()) {
+      if (MI.getDebugOperand(0).isReg() &&
+          MI.getDebugOperand(0).getReg() == OldReg)
+        MI.getDebugOperand(0).setReg(NewReg);
+    } else if (MI.isDebugPHI()) {
+      if (MI.getOperand(0).isReg() &&
+          MI.getOperand(0).getReg() == OldReg)
+        MI.getOperand(0).setReg(NewReg);
+    } else {
+      llvm_unreachable("MI is not DBG_VALUE / DBG_PHI!");
+    }
   }
 
   /// Update all DBG_VALUE instructions that may be affected by the dependency
Index: llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
===================================================================
--- llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -807,14 +807,12 @@
       DbgMI = nullptr;
     }
 
-    if (MI.isDebugValue() || MI.isDebugRef() || MI.isDebugPHI()) {
+    if (MI.isDebugValue() || MI.isDebugPHI()) {
       DbgMI = &MI;
       continue;
     }
-    if (MI.isDebugLabel())
-      continue;
 
-    if (MI.isPseudoProbe())
+    if (MI.isDebugLabel() || MI.isDebugRef() || MI.isPseudoProbe())
       continue;
 
     SUnit *SU = MISUnitMap[&MI];
Index: llvm/test/CodeGen/X86/post-ra-sched-with-debug.mir
===================================================================
--- llvm/test/CodeGen/X86/post-ra-sched-with-debug.mir
+++ llvm/test/CodeGen/X86/post-ra-sched-with-debug.mir
@@ -1,10 +1,12 @@
 # RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=btver2 -run-pass=post-RA-sched -o - %s | FileCheck %s
+# RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=btver2 -run-pass=post-RA-sched -o - %s -experimental-debug-variable-locations| FileCheck %s
 
-# Test that multiple DBG_VALUE's following an instruction whose register needs
-# to be changed during the post-RA scheduler pass are updated correctly.
+# Test that multiple DBG_VALUE's and DBG_PHIs following an instruction whose
+# register needs # to be changed during the post-RA scheduler pass are updated
+# correctly.
 
 # Test case was derived from the output from the following command and
-# the source code below:
+# the source code below. DBG_PHIs added manually later:
 #
 #   clang -S -emit-llvm -target x86_64 -march=btver2 -O2 -g -o - <srcfile> |
 #   llc -stop-before=post-RA-sched -o -
@@ -253,6 +255,8 @@
     ; CHECK:      [[REGISTER:\$r[a-z0-9]+]] = LEA64r {{\$r[a-z0-9]+}}, 1, $noreg, -20, $noreg
     ; CHECK-NEXT: DBG_VALUE [[REGISTER]], $noreg, ![[J_VAR]], !DIExpression(), debug-location ![[J_LOC]]
     ; CHECK-NEXT: DBG_VALUE [[REGISTER]], $noreg, ![[I_VAR]], !DIExpression(), debug-location ![[I_LOC]]
+    ; CHECK-NEXT: DBG_PHI [[REGISTER]], 0
+    ; CHECK-NEXT: DBG_PHI [[REGISTER]], 1
 
     frame-setup PUSH64r killed $rbp, implicit-def $rsp, implicit $rsp
     CFI_INSTRUCTION def_cfa_offset 16
@@ -288,10 +292,14 @@
     $rcx = LEA64r $rbp, 1, $noreg, -20, $noreg
     DBG_VALUE $rcx, $noreg, !46, !17, debug-location !48
     DBG_VALUE $rcx, $noreg, !39, !17, debug-location !44
+    DBG_PHI $rcx, 0
+    DBG_PHI $rcx, 1
     DBG_VALUE $rbp, -20, !29, !17, debug-location !36
     $rcx = CMOV64rr killed $rcx, killed $rdx, 5, implicit killed $eflags
     $rcx = OR64rr killed $rcx, killed $rsi, implicit-def dead $eflags
     $rdx = MOVSX64rm32 $rbx, 1, $noreg, 0, $noreg :: (load (s32), align 8)
+    DBG_INSTR_REF 1, 0, !46, !17, debug-location !48
+    DBG_INSTR_REF 2, 0, !39, !17, debug-location !44
     TEST32mr killed $rcx, 4, killed $rdx, 0, $noreg, killed $eax, implicit-def $eflags :: (load (s32))
     JCC_1 %bb.2, 5, implicit $eflags
     JMP_1 %bb.3