Index: include/llvm/CodeGen/MachineScheduler.h
===================================================================
--- include/llvm/CodeGen/MachineScheduler.h
+++ include/llvm/CodeGen/MachineScheduler.h
@@ -461,6 +461,16 @@
   /// bottom of the DAG region without covereing any unscheduled instruction.
   void buildDAGWithRegPressure();
 
+  /// Release ExitSU predecessors and setup scheduler queues. Re-position
+  /// the Top RP tracker in case the region beginning has changed.
+  void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots) {
+    ScheduleDAGMI::initQueues(TopRoots, BotRoots);
+    if (ShouldTrackPressure) {
+      assert(TopRPTracker.getPos() == RegionBegin && "bad initial Top tracker");
+      TopRPTracker.setPos(CurrentTop);
+    }
+  }
+
   /// Move an instruction and update register pressure.
   void scheduleMI(SUnit *SU, bool IsTopNode);
 
Index: lib/CodeGen/MachineScheduler.cpp
===================================================================
--- lib/CodeGen/MachineScheduler.cpp
+++ lib/CodeGen/MachineScheduler.cpp
@@ -1113,11 +1113,6 @@
   // Initialize ready queues now that the DAG and priority data are finalized.
   initQueues(TopRoots, BotRoots);
 
-  if (ShouldTrackPressure) {
-    assert(TopRPTracker.getPos() == RegionBegin && "bad initial Top tracker");
-    TopRPTracker.setPos(CurrentTop);
-  }
-
   bool IsTopNode = false;
   while (true) {
     DEBUG(dbgs() << "** ScheduleDAGMILive::schedule picking next node\n");
Index: test/CodeGen/Hexagon/misched-top-rptracker-sync.ll
===================================================================
--- /dev/null
+++ test/CodeGen/Hexagon/misched-top-rptracker-sync.ll
@@ -0,0 +1,151 @@
+; RUN: llc -march=hexagon < %s
+; REQUIRES: asserts
+
+; Check that we no longer get this error:
+; void llvm::ScheduleDAGMILive::scheduleMI(llvm::SUnit *, bool):
+; Assertion `TopRPTracker.getPos() == CurrentTop && "out of sync"' failed.
+
+target triple = "hexagon"
+
+%struct.A = type { %struct.B*, %struct.B* }
+%struct.B = type { i8*, %struct.B*, %struct.B* }
+
+@.str.4 = external hidden unnamed_addr constant [41 x i8], align 1
+@__func__.fred = external hidden unnamed_addr constant [16 x i8], align 1
+@.str.5 = external hidden unnamed_addr constant [43 x i8], align 1
+
+; Function Attrs: nounwind
+declare void @_Assert(i8*, i8*) #0
+
+; Function Attrs: nounwind
+define void @fred(%struct.A* %pA, %struct.B* %p) #0 !dbg !6 {
+entry:
+  tail call void @llvm.dbg.value(metadata %struct.A* %pA, i64 0, metadata !26, metadata !28), !dbg !29
+  tail call void @llvm.dbg.value(metadata %struct.B* %p, i64 0, metadata !27, metadata !28), !dbg !30
+  %cmp = icmp eq %struct.B* %p, null, !dbg !31
+  br i1 %cmp, label %cond.false, label %cond.end, !dbg !31
+
+cond.false:                                       ; preds = %entry
+  tail call void @_Assert(i8* getelementptr inbounds ([41 x i8], [41 x i8]* @.str.4, i32 0, i32 0), i8* getelementptr inbounds ([16 x i8], [16 x i8]* @__func__.fred, i32 0, i32 0)) #0, !dbg !32
+  br label %cond.end, !dbg !32
+
+cond.end:                                         ; preds = %cond.false, %entry
+  %cmp1 = icmp eq %struct.A* %pA, null, !dbg !34
+  br i1 %cmp1, label %cond.false3, label %cond.end4, !dbg !34
+
+cond.false3:                                      ; preds = %cond.end
+  tail call void @_Assert(i8* getelementptr inbounds ([43 x i8], [43 x i8]* @.str.5, i32 0, i32 0), i8* getelementptr inbounds ([16 x i8], [16 x i8]* @__func__.fred, i32 0, i32 0)) #0, !dbg !35
+  br label %cond.end4, !dbg !35
+
+cond.end4:                                        ; preds = %cond.false3, %cond.end
+  %p2 = getelementptr inbounds %struct.A, %struct.A* %pA, i32 0, i32 0, !dbg !36
+  %0 = load %struct.B*, %struct.B** %p2, align 4, !dbg !38, !tbaa !39
+  %cmp5 = icmp eq %struct.B* %0, null, !dbg !44
+  br i1 %cmp5, label %if.then, label %if.end, !dbg !45
+
+if.then:                                          ; preds = %cond.end4
+  %p1 = getelementptr inbounds %struct.A, %struct.A* %pA, i32 0, i32 1, !dbg !46
+  store %struct.B* %p, %struct.B** %p1, align 4, !dbg !48, !tbaa !49
+  store %struct.B* %p, %struct.B** %p2, align 4, !dbg !50, !tbaa !39
+  %p4 = getelementptr inbounds %struct.B, %struct.B* %p, i32 0, i32 1, !dbg !51
+  store %struct.B* null, %struct.B** %p4, align 4, !dbg !52, !tbaa !53
+  %p5 = getelementptr inbounds %struct.B, %struct.B* %p, i32 0, i32 2, !dbg !55
+  store %struct.B* null, %struct.B** %p5, align 4, !dbg !56, !tbaa !57
+  br label %return, !dbg !58
+
+if.end:                                           ; preds = %cond.end4
+  %1 = ptrtoint %struct.B* %0 to i32, !dbg !59
+  %p57 = getelementptr inbounds %struct.B, %struct.B* %p, i32 0, i32 2, !dbg !60
+  store %struct.B* null, %struct.B** %p57, align 4, !dbg !61, !tbaa !57
+  %p49 = getelementptr inbounds %struct.B, %struct.B* %p, i32 0, i32 1, !dbg !62
+  %2 = bitcast %struct.B** %p49 to i32*, !dbg !63
+  store i32 %1, i32* %2, align 4, !dbg !63, !tbaa !53
+  %p511 = getelementptr inbounds %struct.B, %struct.B* %0, i32 0, i32 2, !dbg !64
+  store %struct.B* %p, %struct.B** %p511, align 4, !dbg !65, !tbaa !57
+  store %struct.B* %p, %struct.B** %p2, align 4, !dbg !66, !tbaa !39
+  br label %return, !dbg !67
+
+return:                                           ; preds = %if.end, %if.then
+  ret void, !dbg !68
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 (http://llvm.org/git/clang.git 4b380bc1db8b0c72bdbdaf0e4697b1a84100a369) (http://llvm.org/git/llvm.git 6217a62bc009d55e160dbb694f2e94a22c80809f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "bug.c", directory: "/")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!"clang version 3.9.0 (http://llvm.org/git/clang.git 4b380bc1db8b0c72bdbdaf0e4697b1a84100a369) (http://llvm.org/git/llvm.git 6217a62bc009d55e160dbb694f2e94a22c80809f)"}
+!6 = distinct !DISubprogram(name: "fred", scope: !1, file: !1, line: 138, type: !7, isLocal: false, isDefinition: true, scopeLine: 139, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !25)
+!7 = !DISubroutineType(types: !8)
+!8 = !{null, !9, !15}
+!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 32, align: 32)
+!10 = !DIDerivedType(tag: DW_TAG_typedef, name: "A", file: !11, line: 57, baseType: !12)
+!11 = !DIFile(filename: "bug.h", directory: "/")
+!12 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !11, line: 54, size: 64, align: 32, elements: !13)
+!13 = !{!14, !24}
+!14 = !DIDerivedType(tag: DW_TAG_member, name: "p2", scope: !12, file: !11, line: 55, baseType: !15, size: 32, align: 32)
+!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 32, align: 32)
+!16 = !DIDerivedType(tag: DW_TAG_typedef, name: "B", file: !11, line: 50, baseType: !17)
+!17 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "B", file: !11, line: 45, size: 96, align: 32, elements: !18)
+!18 = !{!19, !21, !23}
+!19 = !DIDerivedType(tag: DW_TAG_member, name: "p3", scope: !17, file: !11, line: 47, baseType: !20, size: 32, align: 32)
+!20 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 32, align: 32)
+!21 = !DIDerivedType(tag: DW_TAG_member, name: "p4", scope: !17, file: !11, line: 48, baseType: !22, size: 32, align: 32, offset: 32)
+!22 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !17, size: 32, align: 32)
+!23 = !DIDerivedType(tag: DW_TAG_member, name: "p5", scope: !17, file: !11, line: 49, baseType: !22, size: 32, align: 32, offset: 64)
+!24 = !DIDerivedType(tag: DW_TAG_member, name: "p1", scope: !12, file: !11, line: 56, baseType: !15, size: 32, align: 32, offset: 32)
+!25 = !{!26, !27}
+!26 = !DILocalVariable(name: "pA", arg: 1, scope: !6, file: !1, line: 138, type: !9)
+!27 = !DILocalVariable(name: "p", arg: 2, scope: !6, file: !1, line: 138, type: !15)
+!28 = !DIExpression()
+!29 = !DILocation(line: 138, column: 34, scope: !6)
+!30 = !DILocation(line: 138, column: 57, scope: !6)
+!31 = !DILocation(line: 140, column: 5, scope: !6)
+!32 = !DILocation(line: 140, column: 5, scope: !33)
+!33 = !DILexicalBlockFile(scope: !6, file: !1, discriminator: 2)
+!34 = !DILocation(line: 141, column: 5, scope: !6)
+!35 = !DILocation(line: 141, column: 5, scope: !33)
+!36 = !DILocation(line: 143, column: 30, scope: !37)
+!37 = distinct !DILexicalBlock(scope: !6, file: !1, line: 143, column: 9)
+!38 = !DILocation(line: 155, column: 18, scope: !6)
+!39 = !{!40, !41, i64 0}
+!40 = !{!"", !41, i64 0, !41, i64 4}
+!41 = !{!"any pointer", !42, i64 0}
+!42 = !{!"omnipotent char", !43, i64 0}
+!43 = !{!"Simple C/C++ TBAA"}
+!44 = !DILocation(line: 143, column: 14, scope: !37)
+!45 = !DILocation(line: 143, column: 9, scope: !6)
+!46 = !DILocation(line: 146, column: 26, scope: !47)
+!47 = distinct !DILexicalBlock(scope: !37, file: !1, line: 143, column: 41)
+!48 = !DILocation(line: 146, column: 36, scope: !47)
+!49 = !{!40, !41, i64 4}
+!50 = !DILocation(line: 145, column: 32, scope: !47)
+!51 = !DILocation(line: 147, column: 20, scope: !47)
+!52 = !DILocation(line: 147, column: 29, scope: !47)
+!53 = !{!54, !41, i64 4}
+!54 = !{!"B", !41, i64 0, !41, i64 4, !41, i64 8}
+!55 = !DILocation(line: 148, column: 20, scope: !47)
+!56 = !DILocation(line: 148, column: 29, scope: !47)
+!57 = !{!54, !41, i64 8}
+!58 = !DILocation(line: 149, column: 9, scope: !47)
+!59 = !DILocation(line: 154, column: 41, scope: !6)
+!60 = !DILocation(line: 153, column: 16, scope: !6)
+!61 = !DILocation(line: 153, column: 25, scope: !6)
+!62 = !DILocation(line: 154, column: 16, scope: !6)
+!63 = !DILocation(line: 154, column: 26, scope: !6)
+!64 = !DILocation(line: 155, column: 29, scope: !6)
+!65 = !DILocation(line: 155, column: 39, scope: !6)
+!66 = !DILocation(line: 156, column: 28, scope: !6)
+!67 = !DILocation(line: 157, column: 1, scope: !6)
+!68 = !DILocation(line: 157, column: 1, scope: !69)
+!69 = !DILexicalBlockFile(scope: !6, file: !1, discriminator: 1)