Index: lib/CodeGen/ScheduleDAGInstrs.cpp
===================================================================
--- lib/CodeGen/ScheduleDAGInstrs.cpp
+++ lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -234,6 +234,11 @@
   // Ask the target if address-backscheduling is desirable, and if so how much.
   const TargetSubtargetInfo &ST = MF.getSubtarget();
 
+  // Only use any non-zero latency for real defs/uses, in contrast to
+  // "fake" operands added by regalloc.
+  const MCInstrDesc *DefMIDesc = &SU->getInstr()->getDesc();
+  bool ImplicitPseudoDef = (OperIdx >= DefMIDesc->getNumOperands() &&
+                            !DefMIDesc->hasImplicitDefOfPhysReg(MO.getReg()));
   for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
        Alias.isValid(); ++Alias) {
     if (!Uses.contains(*Alias))
@@ -257,11 +262,18 @@
         Dep = SDep(SU, SDep::Data, *Alias);
         RegUse = UseSU->getInstr();
       }
-      Dep.setLatency(
-        SchedModel.computeOperandLatency(SU->getInstr(), OperIdx, RegUse,
-                                         UseOp));
+      const MCInstrDesc *UseMIDesc =
+          (RegUse ? &UseSU->getInstr()->getDesc() : nullptr);
+      bool ImplicitPseudoUse =
+          (UseMIDesc && UseOp >= ((int)UseMIDesc->getNumOperands()) &&
+           !UseMIDesc->hasImplicitUseOfPhysReg(*Alias));
+      if (!ImplicitPseudoDef && !ImplicitPseudoUse) {
+        Dep.setLatency(SchedModel.computeOperandLatency(SU->getInstr(), OperIdx,
+                                                        RegUse, UseOp));
+        ST.adjustSchedDependency(SU, UseSU, Dep);
+      } else
+        Dep.setLatency(0);
 
-      ST.adjustSchedDependency(SU, UseSU, Dep);
       UseSU->addPred(Dep);
     }
   }
Index: test/CodeGen/SystemZ/misched-readadvances.mir
===================================================================
--- /dev/null
+++ test/CodeGen/SystemZ/misched-readadvances.mir
@@ -0,0 +1,31 @@
+# Check that the extra operand for the full register added by RegAlloc does
+# not have a latency that interferes with the latency adjustment
+# (ReadAdvance) for the MSY register operand.
+
+# RUN: llc %s -mtriple=s390x-linux-gnu -mcpu=z13 -start-before=machine-scheduler \
+# RUN:  -debug-only=machine-scheduler -o - 2>&1 | FileCheck %s
+# REQUIRES: asserts
+
+# CHECK: ScheduleDAGMI::schedule starting
+# CHECK: SU(4): renamable $r2l = MSR renamable $r2l(tied-def 0), renamable $r2l
+# CHECK:   Latency : 6
+# CHECK: SU(5): renamable $r2l = MSY renamable $r2l(tied-def 0), renamable $r1d, -4, $noreg, implicit $r2d
+# CHECK:   Predecessors:
+# CHECK:     SU(4): Data Latency=2 Reg=$r2l
+# CHECK:     SU(4): Data Latency=0 Reg=$r2d
+
+---
+name:            Perl_do_sv_dump
+alignment:       4
+tracksRegLiveness: true
+body:             |
+    bb.0 :
+    %1:addr64bit = IMPLICIT_DEF
+    %2:addr64bit = IMPLICIT_DEF
+    %3:vr64bit = IMPLICIT_DEF
+
+    bb.1 :
+    %2:addr64bit = ALGFI %2, 4294967291, implicit-def dead $cc
+    %2.subreg_l32:addr64bit = MSR %2.subreg_l32, %2.subreg_l32
+    %2.subreg_l32:addr64bit = MSY %2.subreg_l32, %1, -4, $noreg
+...