Index: lib/CodeGen/LivePhysRegs.cpp
===================================================================
--- lib/CodeGen/LivePhysRegs.cpp
+++ lib/CodeGen/LivePhysRegs.cpp
@@ -70,6 +70,8 @@
 /// Simulates liveness when stepping backwards over an instruction(bundle):
 /// Remove Defs, add uses. This is the recommended way of calculating liveness.
 void LivePhysRegs::stepBackward(const MachineInstr &MI) {
+  if (MI.isDebugValue())
+    return;
   // Remove defined registers and regmask kills from the set.
   removeDefs(MI);
 
Index: test/CodeGen/X86/dbg-changes-codegen-branch-folding2.ll
===================================================================
--- test/CodeGen/X86/dbg-changes-codegen-branch-folding2.ll
+++ test/CodeGen/X86/dbg-changes-codegen-branch-folding2.ll
@@ -0,0 +1,209 @@
+; RUN: llc -mtriple=x86_64-linux < %s | FileCheck %s -check-prefixes CHECK,DEBUG
+; RUN: opt -strip-debug < %s | llc -mtriple=x86_64-linux | FileCheck %s
+; Previously, -g was influencing branch-folding to
+; move code.  This was because operands in a DBG_VALUE instruction were being
+; accounted for when calling 'LivePhysRegs::stepBackward()'.
+;
+; Original reproducer, compiled with:
+;   clang++ -emit-llvm -S -O2 -g
+;
+; // Reproducer:
+; typedef signed __attribute__((ext_vector_type(32))) schar32;
+; schar32 i, b;
+; char32_t a;
+; schar32 fn1() {
+;   char c = 1;
+;   volatile char d;
+;   for (char h = 0; h < 13 && c >= d; ++h)
+;     c *= h;
+;   bool e = c > a;
+;   schar32 f = 2 % b, g = e ? f : i;
+;   return g;
+; }
+
+; CHECK-LABEL: # %bb.12:
+; DEBUG:       .loc 1 7 32
+; CHECK-NEXT:    cmpb $0, {{-[0-9]+}}(%rsp)
+; DEBUG-NEXT:  .Ltmp{{[0-9]+}}:
+; DEBUG-NEXT:  .loc 1 7 3
+; CHECK-NEXT:    jg .LBB0_15
+; DEBUG-NEXT:  .Ltmp{{[0-9]+}}:
+; CHECK-LABEL: # %bb.14
+
+@i = dso_local local_unnamed_addr global <32 x i32> zeroinitializer, align 128, !dbg !0
+@b = dso_local local_unnamed_addr global <32 x i32> zeroinitializer, align 128, !dbg !6
+@a = dso_local local_unnamed_addr global i32 0, align 4, !dbg !13
+
+define dso_local <32 x i32> @_Z3fn1v() local_unnamed_addr !dbg !20 {
+  %1 = alloca i8, align 1
+  call void @llvm.dbg.value(metadata i8 1, metadata !24, metadata !DIExpression()), !dbg !34
+  call void @llvm.dbg.value(metadata i8* %1, metadata !26, metadata !DIExpression()), !dbg !35
+  call void @llvm.lifetime.start.p0i8(i64 1, i8* nonnull %1), !dbg !36
+  call void @llvm.dbg.value(metadata i8 0, metadata !28, metadata !DIExpression()), !dbg !37
+  call void @llvm.dbg.value(metadata i32 0, metadata !28, metadata !DIExpression()), !dbg !37
+  %2 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %2, metadata !26, metadata !DIExpression()), !dbg !35
+  %3 = icmp sgt i8 %2, 1, !dbg !40
+  br i1 %3, label %4, label %12, !dbg !41
+
+; <label>:4:                                      ; preds = %45, %42, %39, %36, %33, %30, %27, %24, %21, %18, %15, %12, %0
+  %5 = phi i32 [ 1, %0 ], [ 0, %12 ], [ 0, %15 ], [ 0, %18 ], [ 0, %21 ], [ 0, %24 ], [ 0, %27 ], [ 0, %30 ], [ 0, %33 ], [ 0, %36 ], [ 0, %39 ], [ 0, %42 ], [ 0, %45 ]
+  %6 = load i32, i32* @a, align 4, !dbg !42, !tbaa !43
+  %7 = icmp ugt i32 %5, %6, !dbg !47
+  %8 = load <32 x i32>, <32 x i32>* @b, align 128, !dbg !48, !tbaa !49
+  %9 = srem <32 x i32> <i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2>, %8, !dbg !50
+  call void @llvm.dbg.value(metadata <32 x i32> %9, metadata !32, metadata !DIExpression()), !dbg !51
+  %10 = load <32 x i32>, <32 x i32>* @i, align 128, !dbg !52
+  %11 = select i1 %7, <32 x i32> %9, <32 x i32> %10, !dbg !53
+  call void @llvm.dbg.value(metadata <32 x i32> %11, metadata !33, metadata !DIExpression()), !dbg !54
+  call void @llvm.dbg.value(metadata i8* %1, metadata !26, metadata !DIExpression()), !dbg !35
+  call void @llvm.lifetime.end.p0i8(i64 1, i8* nonnull %1), !dbg !55
+  ret <32 x i32> %11, !dbg !56
+
+; <label>:12:                                     ; preds = %0
+  call void @llvm.dbg.value(metadata i32 1, metadata !28, metadata !DIExpression()), !dbg !37
+  %13 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %13, metadata !26, metadata !DIExpression()), !dbg !35
+  %14 = icmp sgt i8 %13, 0, !dbg !40
+  br i1 %14, label %4, label %15, !dbg !41
+
+; <label>:15:                                     ; preds = %12
+  call void @llvm.dbg.value(metadata i32 2, metadata !28, metadata !DIExpression()), !dbg !37
+  %16 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %16, metadata !26, metadata !DIExpression()), !dbg !35
+  %17 = icmp sgt i8 %16, 0, !dbg !40
+  br i1 %17, label %4, label %18, !dbg !41
+
+; <label>:18:                                     ; preds = %15
+  call void @llvm.dbg.value(metadata i32 3, metadata !28, metadata !DIExpression()), !dbg !37
+  %19 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %19, metadata !26, metadata !DIExpression()), !dbg !35
+  %20 = icmp sgt i8 %19, 0, !dbg !40
+  br i1 %20, label %4, label %21, !dbg !41
+
+; <label>:21:                                     ; preds = %18
+  call void @llvm.dbg.value(metadata i32 4, metadata !28, metadata !DIExpression()), !dbg !37
+  %22 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %22, metadata !26, metadata !DIExpression()), !dbg !35
+  %23 = icmp sgt i8 %22, 0, !dbg !40
+  br i1 %23, label %4, label %24, !dbg !41
+
+; <label>:24:                                     ; preds = %21
+  call void @llvm.dbg.value(metadata i32 5, metadata !28, metadata !DIExpression()), !dbg !37
+  %25 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %25, metadata !26, metadata !DIExpression()), !dbg !35
+  %26 = icmp sgt i8 %25, 0, !dbg !40
+  br i1 %26, label %4, label %27, !dbg !41
+
+; <label>:27:                                     ; preds = %24
+  call void @llvm.dbg.value(metadata i32 6, metadata !28, metadata !DIExpression()), !dbg !37
+  %28 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %28, metadata !26, metadata !DIExpression()), !dbg !35
+  %29 = icmp sgt i8 %28, 0, !dbg !40
+  br i1 %29, label %4, label %30, !dbg !41
+
+; <label>:30:                                     ; preds = %27
+  call void @llvm.dbg.value(metadata i32 7, metadata !28, metadata !DIExpression()), !dbg !37
+  %31 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %31, metadata !26, metadata !DIExpression()), !dbg !35
+  %32 = icmp sgt i8 %31, 0, !dbg !40
+  br i1 %32, label %4, label %33, !dbg !41
+
+; <label>:33:                                     ; preds = %30
+  call void @llvm.dbg.value(metadata i32 8, metadata !28, metadata !DIExpression()), !dbg !37
+  %34 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %34, metadata !26, metadata !DIExpression()), !dbg !35
+  %35 = icmp sgt i8 %34, 0, !dbg !40
+  br i1 %35, label %4, label %36, !dbg !41
+
+; <label>:36:                                     ; preds = %33
+  call void @llvm.dbg.value(metadata i32 9, metadata !28, metadata !DIExpression()), !dbg !37
+  %37 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %37, metadata !26, metadata !DIExpression()), !dbg !35
+  %38 = icmp sgt i8 %37, 0, !dbg !40
+  br i1 %38, label %4, label %39, !dbg !41
+
+; <label>:39:                                     ; preds = %36
+  call void @llvm.dbg.value(metadata i32 10, metadata !28, metadata !DIExpression()), !dbg !37
+  %40 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %40, metadata !26, metadata !DIExpression()), !dbg !35
+  %41 = icmp sgt i8 %40, 0, !dbg !40
+  br i1 %41, label %4, label %42, !dbg !41
+
+; <label>:42:                                     ; preds = %39
+  call void @llvm.dbg.value(metadata i32 11, metadata !28, metadata !DIExpression()), !dbg !37
+  %43 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %43, metadata !26, metadata !DIExpression()), !dbg !35
+  %44 = icmp sgt i8 %43, 0, !dbg !40
+  br i1 %44, label %4, label %45, !dbg !41
+
+; <label>:45:                                     ; preds = %42
+  call void @llvm.dbg.value(metadata i32 12, metadata !28, metadata !DIExpression()), !dbg !37
+  %46 = load volatile i8, i8* %1, align 1, !dbg !38
+  call void @llvm.dbg.value(metadata i8 %46, metadata !26, metadata !DIExpression()), !dbg !35
+  br label %4, !dbg !41
+}
+
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!16, !17, !18}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "i", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "reduced.cpp", directory: "test/CodeGen/X86")
+!4 = !{}
+!5 = !{!0, !6, !13}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIDerivedType(tag: DW_TAG_typedef, name: "schar32", file: !3, line: 1, baseType: !9)
+!9 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, size: 1024, flags: DIFlagVector, elements: !11)
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DISubrange(count: 32)
+!13 = !DIGlobalVariableExpression(var: !14, expr: !DIExpression())
+!14 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 3, type: !15, isLocal: false, isDefinition: true)
+!15 = !DIBasicType(name: "char32_t", size: 32, encoding: DW_ATE_UTF)
+!16 = !{i32 2, !"Dwarf Version", i32 4}
+!17 = !{i32 2, !"Debug Info Version", i32 3}
+!18 = !{i32 1, !"wchar_size", i32 4}
+!20 = distinct !DISubprogram(name: "fn1", linkageName: "_Z3fn1v", scope: !3, file: !3, line: 4, type: !21, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: true, unit: !2, variables: !23)
+!21 = !DISubroutineType(types: !22)
+!22 = !{!8}
+!23 = !{!24, !26, !28, !30, !32, !33}
+!24 = !DILocalVariable(name: "c", scope: !20, file: !3, line: 5, type: !25)
+!25 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!26 = !DILocalVariable(name: "d", scope: !20, file: !3, line: 6, type: !27)
+!27 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !25)
+!28 = !DILocalVariable(name: "h", scope: !29, file: !3, line: 7, type: !25)
+!29 = distinct !DILexicalBlock(scope: !20, file: !3, line: 7, column: 3)
+!30 = !DILocalVariable(name: "e", scope: !20, file: !3, line: 9, type: !31)
+!31 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
+!32 = !DILocalVariable(name: "f", scope: !20, file: !3, line: 10, type: !8)
+!33 = !DILocalVariable(name: "g", scope: !20, file: !3, line: 10, type: !8)
+!34 = !DILocation(line: 5, column: 8, scope: !20)
+!35 = !DILocation(line: 6, column: 17, scope: !20)
+!36 = !DILocation(line: 6, column: 3, scope: !20)
+!37 = !DILocation(line: 7, column: 13, scope: !29)
+!38 = !DILocation(line: 7, column: 35, scope: !39)
+!39 = distinct !DILexicalBlock(scope: !29, file: !3, line: 7, column: 3)
+!40 = !DILocation(line: 7, column: 32, scope: !39)
+!41 = !DILocation(line: 7, column: 3, scope: !29)
+!42 = !DILocation(line: 9, column: 16, scope: !20)
+!43 = !{!44, !44, i64 0}
+!44 = !{!"char32_t", !45, i64 0}
+!45 = !{!"omnipotent char", !46, i64 0}
+!46 = !{!"Simple C++ TBAA"}
+!47 = !DILocation(line: 9, column: 14, scope: !20)
+!48 = !DILocation(line: 10, column: 19, scope: !20)
+!49 = !{!45, !45, i64 0}
+!50 = !DILocation(line: 10, column: 17, scope: !20)
+!51 = !DILocation(line: 10, column: 11, scope: !20)
+!52 = !DILocation(line: 10, column: 34, scope: !20)
+!53 = !DILocation(line: 10, column: 26, scope: !20)
+!54 = !DILocation(line: 10, column: 22, scope: !20)
+!55 = !DILocation(line: 12, column: 1, scope: !20)
+!56 = !DILocation(line: 11, column: 3, scope: !20)