diff --git a/llvm/lib/CodeGen/MachineScheduler.cpp b/llvm/lib/CodeGen/MachineScheduler.cpp
--- a/llvm/lib/CodeGen/MachineScheduler.cpp
+++ b/llvm/lib/CodeGen/MachineScheduler.cpp
@@ -2331,20 +2331,24 @@
          "Cannot have zero instances of a ProcResource");
 
   if (isUnbufferedGroup(PIdx)) {
-    // If any subunits are used by the instruction, report that the resource
-    // group is available at 0, effectively removing the group record from
-    // hazarding and basing the hazarding decisions on the subunit records.
-    // Otherwise, choose the first available instance from among the subunits.
-    // Specifications which assign cycles to both the subunits and the group or
-    // which use an unbuffered group with buffered subunits will appear to
-    // schedule strangely. In the first case, the additional cycles for the
-    // group will be ignored.  In the second, the group will be ignored
-    // entirely.
+    // If any subunits are used by the instruction, report that the
+    // subunits of the resource group are available at the first cycle
+    // in which the unit is available, effectively removing the group
+    // record from hazarding and basing the hazarding decisions on the
+    // subunit records. Otherwise, choose the first available instance
+    // from among the subunits.  Specifications which assign cycles to
+    // both the subunits and the group or which use an unbuffered
+    // group with buffered subunits will appear to schedule
+    // strangely. In the first case, the additional cycles for the
+    // group will be ignored.  In the second, the group will be
+    // ignored entirely.
     for (const MCWriteProcResEntry &PE :
          make_range(SchedModel->getWriteProcResBegin(SC),
                     SchedModel->getWriteProcResEnd(SC)))
       if (ResourceGroupSubUnitMasks[PIdx][PE.ProcResourceIdx])
-        return std::make_pair(0u, StartIndex);
+        return std::make_pair(
+            getNextResourceCycleByInstance(StartIndex, Cycles, StartAtCycle),
+            StartIndex);
 
     auto SubUnits = SchedModel->getProcResource(PIdx)->SubUnitsIdxBegin;
     for (unsigned I = 0, End = NumberOfInstances; I < End; ++I) {
diff --git a/llvm/test/CodeGen/ARM/misched-prevent-erase-history-of-subunits.mir b/llvm/test/CodeGen/ARM/misched-prevent-erase-history-of-subunits.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/misched-prevent-erase-history-of-subunits.mir
@@ -0,0 +1,37 @@
+# RUN: llc -mtriple=thumbv7em-unknown-unknown -mcpu=cortex-m7 \
+# RUN:    -sched-model-force-enable-intervals \
+# RUN:    %s -run-pass=machine-scheduler -o - 2>&1 -debug | FileCheck %s
+# REQUIRES: arm-registered-target, asserts
+
+# NOTE: Without the bugfix introduced in this code, the test below
+# would raise the assertion "A resource is being overwritten" from
+# `ResourceSegments::add` when enforcing the use of resource intervals
+# via -sched-model-force-enable-intervals with the scheduling model
+# for -mcpu=cortex-m7.
+
+# CHECK-LABEL: *** Final schedule for %bb.0 ***
+# CHECK: SU(0):   %0:dpr = COPY $d0
+# CHECK: SU(1):   %1:dpr = VABSD %0:dpr, 14, $noreg
+# CHECK: SU(2):   %2:dpr = VLDRD %const.0, 0, 14, $noreg :: (load (s64) from constant-pool)
+# CHECK: SU(4):   %3:rgpr = t2MOVi 0, 14, $noreg, $noreg
+# CHECK: SU(3):   VCMPD %1:dpr, %2:dpr, 14, $noreg, implicit-def $fpscr_nzcv
+# CHECK: SU(5):   $r0 = COPY %3:rgpr
+---
+name:            test
+tracksRegLiveness: true
+constants:
+  - id:              0
+    value:           double 0x7FF0000000000000
+body:             |
+  bb.0:
+    liveins: $d0
+
+    %0:dpr = COPY $d0
+    %1:dpr = VABSD %0, 14 /* CC::al */, $noreg
+    %2:dpr = VLDRD %const.0, 0, 14 /* CC::al */, $noreg :: (load (s64) from constant-pool)
+    VCMPD %1, %2, 14 /* CC::al */, $noreg, implicit-def $fpscr_nzcv
+    %4:rgpr = t2MOVi 0, 14 /* CC::al */, $noreg, $noreg
+    $r0 = COPY %4
+    tBX_RET 14 /* CC::al */, $noreg, implicit killed $r0
+
+...