Index: llvm/tools/llvm-reduce/ReducerWorkItem.cpp
===================================================================
--- llvm/tools/llvm-reduce/ReducerWorkItem.cpp
+++ llvm/tools/llvm-reduce/ReducerWorkItem.cpp
@@ -21,14 +21,9 @@
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 
-// FIXME: Preserve frame index numbers. The numbering is off for fixed objects
-// since they are inserted at the beginning. This would avoid the need for the
-// Src2DstFrameIndex map and in the future target MFI code wouldn't need to
-// worry about it either.
 static void cloneFrameInfo(
     MachineFrameInfo &DstMFI, const MachineFrameInfo &SrcMFI,
-    const DenseMap<MachineBasicBlock *, MachineBasicBlock *> Src2DstMBB,
-    DenseMap<int, int> &Src2DstFrameIndex) {
+    const DenseMap<MachineBasicBlock *, MachineBasicBlock *> &Src2DstMBB) {
   DstMFI.setFrameAddressIsTaken(SrcMFI.isFrameAddressTaken());
   DstMFI.setReturnAddressIsTaken(SrcMFI.isReturnAddressTaken());
   DstMFI.setHasStackMap(SrcMFI.hasStackMap());
@@ -59,15 +54,22 @@
   if (MachineBasicBlock *RestorePt = SrcMFI.getRestorePoint())
     DstMFI.setRestorePoint(Src2DstMBB.find(RestorePt)->second);
 
-  for (int i = SrcMFI.getObjectIndexBegin(), e = SrcMFI.getObjectIndexEnd();
+
+  auto CopyObjectProperties = [](MachineFrameInfo &DstMFI,
+                                 const MachineFrameInfo &SrcMFI, int FI) {
+    if (SrcMFI.isStatepointSpillSlotObjectIndex(FI))
+      DstMFI.markAsStatepointSpillSlotObjectIndex(FI);
+    DstMFI.setObjectSSPLayout(FI, SrcMFI.getObjectSSPLayout(FI));
+    DstMFI.setObjectZExt(FI, SrcMFI.isObjectZExt(FI));
+    DstMFI.setObjectSExt(FI, SrcMFI.isObjectSExt(FI));
+  };
+
+  for (int i = 0, e = SrcMFI.getNumObjects() - SrcMFI.getNumFixedObjects();
        i != e; ++i) {
     int NewFI;
 
-    if (SrcMFI.isFixedObjectIndex(i)) {
-      NewFI = DstMFI.CreateFixedObject(
-          SrcMFI.getObjectSize(i), SrcMFI.getObjectOffset(i),
-          SrcMFI.isImmutableObjectIndex(i), SrcMFI.isAliasedObjectIndex(i));
-    } else if (SrcMFI.isVariableSizedObjectIndex(i)) {
+    assert(!SrcMFI.isFixedObjectIndex(i));
+    if (SrcMFI.isVariableSizedObjectIndex(i)) {
       NewFI = DstMFI.CreateVariableSizedObject(SrcMFI.getObjectAlign(i),
                                                SrcMFI.getObjectAllocation(i));
     } else {
@@ -78,13 +80,23 @@
       DstMFI.setObjectOffset(NewFI, SrcMFI.getObjectOffset(i));
     }
 
-    if (SrcMFI.isStatepointSpillSlotObjectIndex(i))
-      DstMFI.markAsStatepointSpillSlotObjectIndex(NewFI);
-    DstMFI.setObjectSSPLayout(NewFI, SrcMFI.getObjectSSPLayout(i));
-    DstMFI.setObjectZExt(NewFI, SrcMFI.isObjectZExt(i));
-    DstMFI.setObjectSExt(NewFI, SrcMFI.isObjectSExt(i));
+    CopyObjectProperties(DstMFI, SrcMFI, i);
+
+    (void)NewFI;
+    assert(i == NewFI && "expected to keep stable frame index numbering");
+  }
 
-    Src2DstFrameIndex[i] = NewFI;
+  // Copy the fixed frame objects backwards to preserve frame index numbers,
+  // since CreateFixedObject uses front insertion.
+  for (int i = -1; i >= (int)-SrcMFI.getNumFixedObjects(); --i) {
+    assert(SrcMFI.isFixedObjectIndex(i));
+    int NewFI = DstMFI.CreateFixedObject(
+      SrcMFI.getObjectSize(i), SrcMFI.getObjectOffset(i),
+      SrcMFI.isImmutableObjectIndex(i), SrcMFI.isAliasedObjectIndex(i));
+    CopyObjectProperties(DstMFI, SrcMFI, i);
+
+    (void)NewFI;
+    assert(i == NewFI && "expected to keep stable frame index numbering");
   }
 
   for (unsigned I = 0, E = SrcMFI.getLocalFrameObjectCount(); I < E; ++I) {
@@ -92,24 +104,15 @@
     DstMFI.mapLocalFrameObject(LocalObject.first, LocalObject.second);
   }
 
-  // Remap the frame indexes in the CalleeSavedInfo
-  std::vector<CalleeSavedInfo> CalleeSavedInfos = SrcMFI.getCalleeSavedInfo();
-  for (CalleeSavedInfo &CSInfo : CalleeSavedInfos) {
-    if (!CSInfo.isSpilledToReg())
-      CSInfo.setFrameIdx(Src2DstFrameIndex[CSInfo.getFrameIdx()]);
-  }
-
-  DstMFI.setCalleeSavedInfo(std::move(CalleeSavedInfos));
+  DstMFI.setCalleeSavedInfo(SrcMFI.getCalleeSavedInfo());
 
   if (SrcMFI.hasStackProtectorIndex()) {
-    DstMFI.setStackProtectorIndex(
-        Src2DstFrameIndex[SrcMFI.getStackProtectorIndex()]);
+    DstMFI.setStackProtectorIndex(SrcMFI.getStackProtectorIndex());
   }
 
   // FIXME: Needs test, missing MIR serialization.
   if (SrcMFI.hasFunctionContextIndex()) {
-    DstMFI.setFunctionContextIndex(
-        Src2DstFrameIndex[SrcMFI.getFunctionContextIndex()]);
+    DstMFI.setFunctionContextIndex(SrcMFI.getFunctionContextIndex());
   }
 }
 
@@ -119,7 +122,6 @@
       SrcMF->getFunctionNumber(), SrcMF->getMMI());
   DenseMap<MachineBasicBlock *, MachineBasicBlock *> Src2DstMBB;
   DenseMap<Register, Register> Src2DstReg;
-  DenseMap<int, int> Src2DstFrameIndex;
 
   auto *SrcMRI = &SrcMF->getRegInfo();
   auto *DstMRI = &DstMF->getRegInfo();
@@ -132,12 +134,10 @@
   MachineFrameInfo &DstMFI = DstMF->getFrameInfo();
 
   // Copy stack objects and other info
-  cloneFrameInfo(DstMFI, SrcMFI, Src2DstMBB, Src2DstFrameIndex);
+  cloneFrameInfo(DstMFI, SrcMFI, Src2DstMBB);
 
   // Remap the debug info frame index references.
   DstMF->VariableDbgInfos = SrcMF->VariableDbgInfos;
-  for (MachineFunction::VariableDbgInfo &DbgInfo : DstMF->VariableDbgInfos)
-    DbgInfo.Slot = Src2DstFrameIndex[DbgInfo.Slot];
 
   // FIXME: Need to clone MachineFunctionInfo, which may also depend on frame
   // index and block mapping.
@@ -219,9 +219,6 @@
         // Update MBB.
         if (DstMO.isMBB()) {
           DstMO.setMBB(Src2DstMBB[DstMO.getMBB()]);
-        } else if (DstMO.isFI()) {
-          // Update frame indexes
-          DstMO.setIndex(Src2DstFrameIndex[DstMO.getIndex()]);
         }
 
         DstMI->addOperand(DstMO);