Index: lib/Transforms/Utils/LoopUnrollRuntime.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -394,6 +394,12 @@
   if (CreateRemainderLoop) {
     Loop *NewLoop = NewLoops[L];
     assert(NewLoop && "L should have been cloned");
+
+    // Only add loop metadata if the loop is not going to be completely
+    // unrolled.
+    if (UnrollRemainder)
+      return NewLoop;
+
     // Add unroll disable metadata to disable future unrolling for this loop.
     SmallVector<Metadata *, 4> MDs;
     // Reserve first location for self reference to the LoopID metadata node.
@@ -414,13 +420,11 @@
     }
 
     LLVMContext &Context = NewLoop->getHeader()->getContext();
-    if (!UnrollRemainder) {
-      SmallVector<Metadata *, 1> DisableOperands;
-      DisableOperands.push_back(MDString::get(Context,
-                                              "llvm.loop.unroll.disable"));
-      MDNode *DisableNode = MDNode::get(Context, DisableOperands);
-      MDs.push_back(DisableNode);
-    }
+    SmallVector<Metadata *, 1> DisableOperands;
+    DisableOperands.push_back(MDString::get(Context,
+                                            "llvm.loop.unroll.disable"));
+    MDNode *DisableNode = MDNode::get(Context, DisableOperands);
+    MDs.push_back(DisableNode);
 
     MDNode *NewLoopID = MDNode::get(Context, MDs);
     // Set operand 0 to refer to the loop id itself.
@@ -536,6 +540,8 @@
                                       bool PreserveLCSSA) {
   DEBUG(dbgs() << "Trying runtime unrolling on Loop: \n");
   DEBUG(L->dump());
+  DEBUG(UseEpilogRemainder ? dbgs() << "Using epilog remainder.\n" :
+        dbgs() << "Using prolog remainder.\n");
 
   // Make sure the loop is in canonical form.
   if (!L->isLoopSimplifyForm()) {
@@ -892,6 +898,7 @@
   }
 
   if (remainderLoop && UnrollRemainder) {
+    DEBUG(dbgs() << "Unrolling remainder loop\n");
     UnrollLoop(remainderLoop, /*Count*/Count - 1, /*TripCount*/Count - 1,
                /*Force*/false, /*AllowRuntime*/false,
                /*AllowExpensiveTripCount*/false, /*PreserveCondBr*/true,
Index: test/DebugInfo/unrolled-loop-remainder.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/unrolled-loop-remainder.ll
@@ -0,0 +1,106 @@
+; RUN: opt -loop-unroll -unroll-runtime -unroll-allow-remainder -unroll-count=4 -unroll-remainder -S %s -o - | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@b = common local_unnamed_addr global i32 0, align 4, !dbg !0
+@a = common local_unnamed_addr global i32* null, align 8, !dbg !6
+
+; Test that loop remainder unrolling doesn't corrupt debuginfo. This example
+; used to cause an assert, but also test that the unrolled backwards branches
+; have the same DILocation.
+
+; CHECK-LABEL: func_c
+; CHECK-LABEL: for.body.lr.ph:
+; CHECK: br i1 %[[CMP0:.*]], label %[[PRE:.*]], label %for.body.prol.loopexit, !dbg !24
+; CHECK-LABEL: for.body:
+; CHECK: br i1 %[[CMP1:.*]], label %[[CRIT_EDGE:.*]], label %for.body, !dbg !24, !llvm.loop !30
+; CHECK-LABEL: for.cond.for.end_crit_edge:
+; CHECK: br label %for.end, !dbg !24
+; CHECK-LABEL: for.body.prol.1:
+; CHECK: br i1 %[[CMP2:.*]], label %for.body.prol.2, label %[[EXIT:.*]], !dbg !24
+; CHECK-LABEL: for.body.prol.2:
+define i32 @func_c() local_unnamed_addr #0 !dbg !14 {
+entry:
+  %.pr = load i32, i32* @b, align 4, !dbg !17, !tbaa !20
+  %tobool1 = icmp eq i32 %.pr, 0, !dbg !24
+  br i1 %tobool1, label %for.end, label %for.body.lr.ph, !dbg !24
+
+for.body.lr.ph:
+  %a.promoted = load i32*, i32** @a, align 8, !dbg !25, !tbaa !26
+  %0 = sub i32 -2, %.pr, !dbg !24
+  %1 = and i32 %0, -2, !dbg !24
+  %2 = add i32 %.pr, %1, !dbg !24
+  br label %for.body, !dbg !24
+
+for.body:
+  %3 = phi i32* [ %a.promoted, %for.body.lr.ph ], [ %6, %for.body ], !dbg !28
+  %4 = phi i32 [ %.pr, %for.body.lr.ph ], [ %add, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %3, i64 1, !dbg !28
+  %5 = load i32, i32* %arrayidx, align 4, !dbg !28, !tbaa !20
+  %conv = sext i32 %5 to i64, !dbg !28
+  %6 = inttoptr i64 %conv to i32*, !dbg !28
+  %add = add nsw i32 %4, 2, !dbg !29
+  %tobool = icmp eq i32 %add, 0, !dbg !24
+  br i1 %tobool, label %for.cond.for.end_crit_edge, label %for.body, !dbg !24, !llvm.loop !30
+
+for.cond.for.end_crit_edge:
+  %7 = add i32 %2, 2, !dbg !24
+  store i32* %6, i32** @a, align 8, !dbg !25, !tbaa !26
+  store i32 %7, i32* @b, align 4, !dbg !32, !tbaa !20
+  br label %for.end, !dbg !24
+
+for.end:
+  ret i32 undef, !dbg !33
+}
+
+; CHECK-LABEL: func_d
+define void @func_d() local_unnamed_addr #1 !dbg !34 {
+entry:
+  ret void, !dbg !37
+}
+
+attributes #0 = { norecurse nounwind uwtable }
+attributes #0 = { norecurse nounwind readnone uwtable }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!10, !11, !12}
+!llvm.ident = !{!13}
+
+!0 = !DIGlobalVariableExpression(var: !1)
+!1 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 2, type: !9, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 (http://llvm.org/git/clang.git 044091b728654e62444a7ea10e6efb489c705bed) (http://llvm.org/git/llvm.git 1c7b55afdb1c5791e0557d9e32e2dd07c7acb2b0)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "loop.c", directory: "/work/projects/src/tests/unroll-debug-info")
+!4 = !{}
+!5 = !{!6, !0}
+!6 = !DIGlobalVariableExpression(var: !7)
+!7 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !{i32 2, !"Dwarf Version", i32 4}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{!"clang version 6.0.0 (http://llvm.org/git/clang.git 044091b728654e62444a7ea10e6efb489c705bed) (http://llvm.org/git/llvm.git 1c7b55afdb1c5791e0557d9e32e2dd07c7acb2b0)"}
+!14 = distinct !DISubprogram(name: "c", scope: !3, file: !3, line: 3, type: !15, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, unit: !2, variables: !4)
+!15 = !DISubroutineType(types: !16)
+!16 = !{!9}
+!17 = !DILocation(line: 4, column: 12, scope: !18)
+!18 = distinct !DILexicalBlock(scope: !19, file: !3, line: 4, column: 5)
+!19 = distinct !DILexicalBlock(scope: !14, file: !3, line: 4, column: 5)
+!20 = !{!21, !21, i64 0}
+!21 = !{!"int", !22, i64 0}
+!22 = !{!"omnipotent char", !23, i64 0}
+!23 = !{!"Simple C/C++ TBAA"}
+!24 = !DILocation(line: 4, column: 5, scope: !19)
+!25 = !DILocation(line: 5, column: 13, scope: !18)
+!26 = !{!27, !27, i64 0}
+!27 = !{!"any pointer", !22, i64 0}
+!28 = !DILocation(line: 5, column: 15, scope: !18)
+!29 = !DILocation(line: 4, column: 21, scope: !18)
+!30 = distinct !{!30, !24, !31}
+!31 = !DILocation(line: 5, column: 18, scope: !19)
+!32 = !DILocation(line: 4, column: 17, scope: !18)
+!33 = !DILocation(line: 6, column: 1, scope: !14)
+!34 = distinct !DISubprogram(name: "d", scope: !3, file: !3, line: 7, type: !35, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: true, unit: !2, variables: !4)
+!35 = !DISubroutineType(types: !36)
+!36 = !{null}
+!37 = !DILocation(line: 7, column: 11, scope: !34)
Index: test/Transforms/LoopUnroll/runtime-unroll-remainder.ll
===================================================================
--- test/Transforms/LoopUnroll/runtime-unroll-remainder.ll
+++ test/Transforms/LoopUnroll/runtime-unroll-remainder.ll
@@ -33,7 +33,7 @@
 
 ; CHECK: [[EPIL_PEEL0]]:
 ; CHECK: [[PEEL_CMP0:%[a-z.0-9]+]] = icmp eq i64 %xtraiter, 1
-; CHECK: br i1 [[PEEL_CMP0]], label %[[EPIL_EXIT:.*]], label %[[EPIL_PEEL1:.*]],
+; CHECK: br i1 [[PEEL_CMP0]], label %[[EPIL_EXIT:.*]], label %[[EPIL_PEEL1:.*]]
 
 ; CHECK: [[EPIL_EXIT]]:
 ; CHECK: br label %[[EXIT]]
@@ -54,7 +54,7 @@
 
 ; CHECK: [[EPIL_PEEL1]]:
 ; CHECK: [[PEEL_CMP1:%[a-z.0-9]+]] = icmp eq i64 %xtraiter, 2
-; CHECK: br i1 [[PEEL_CMP1]], label %[[EPIL_EXIT]], label %[[EPIL_PEEL2:.*]],
+; CHECK: br i1 [[PEEL_CMP1]], label %[[EPIL_EXIT]], label %[[EPIL_PEEL2:.*]]
 
 ; CHECK: [[EPIL_PEEL2]]:
 ; CHECK: br label %[[EXIT]]