Index: llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -566,7 +566,7 @@
 
   if (BrInst.isUnconditional()) {
     // If the unconditional target is the layout successor, fallthrough.
-    if (!CurMBB.isLayoutSuccessor(Succ0MBB))
+    if (OptLevel == CodeGenOpt::None || !CurMBB.isLayoutSuccessor(Succ0MBB))
       MIRBuilder.buildBr(*Succ0MBB);
 
     // Link successors.
Index: llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
===================================================================
--- llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
+++ llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
@@ -2093,17 +2093,8 @@
     I.eraseFromParent();
     return true;
   }
-  case TargetOpcode::G_BR: {
-    // If the branch jumps to the fallthrough block, don't bother emitting it.
-    // Only do this for -O0 for a good code size improvement, because when
-    // optimizations are enabled we want to leave this choice to
-    // MachineBlockPlacement.
-    bool EnableOpt = MF.getTarget().getOptLevel() != CodeGenOpt::None;
-    if (EnableOpt || !MBB.isLayoutSuccessor(I.getOperand(0).getMBB()))
+  case TargetOpcode::G_BR:
       return false;
-    I.eraseFromParent();
-    return true;
-  }
   case TargetOpcode::G_SHL:
     return earlySelectSHL(I, MRI);
   case TargetOpcode::G_CONSTANT: {
Index: llvm/test/DebugInfo/AArch64/fallthrough-branch.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/AArch64/fallthrough-branch.ll
@@ -0,0 +1,52 @@
+; RUN: llc -O0 -stop-before=livedebugvalues < %s | FileCheck %s
+
+; ModuleID = '/tmp/t.o'
+source_filename = "/tmp/t.o"
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "arm64-apple-macosx11.0.0"
+
+@__swift_reflection_version = linkonce_odr hidden constant i16 3
+@llvm.swift_module_hash = private constant [16 x i8] c"\AD\85\B7\B6\00H\8F\19\17\F8\91V\14\0A\1F*", section "__LLVM,__swift_modhash"
+@llvm.used = appending global [3 x i8*] [i8* bitcast (void (i1)* @"$s1t1f1bySb_tF" to i8*), i8* bitcast (i16* @__swift_reflection_version to i8*), i8* getelementptr inbounds ([16 x i8], [16 x i8]* @llvm.swift_module_hash, i32 0, i32 0)], section "llvm.metadata", align 8
+
+define swiftcc void @"$s1t1f1bySb_tF"(i1 %0) !dbg !35 {
+  %2 = alloca i1, align 8
+  %3 = bitcast i1* %2 to i8*
+  call void @llvm.memset.p0i8.i64(i8* align 8 %3, i8 0, i64 1, i1 false)
+  store i1 %0, i1* %2, align 8, !dbg !37
+; CHECK:   B %bb.1, debug-location !{{[0-9]+}}
+  br i1 %0, label %4, label %5, !dbg !38
+
+4:                                                ; preds = %1
+; Check that at -O0 the branches and their debug locations are not eliminated.
+; CHECK:   B %bb.3, debug-location !{{[0-9]+}}
+  br label %6, !dbg !39
+
+5:                                                ; preds = %1
+; CHECK:   B %bb.3, debug-location !{{[0-9]+}}
+  br label %6, !dbg !40
+
+6:                                                ; preds = %4, %5
+  ret void, !dbg !39
+}
+
+; Function Attrs: argmemonly nofree nosync nounwind willreturn writeonly
+declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg) #1
+attributes #1 = { argmemonly nofree nosync nounwind willreturn writeonly }
+
+!llvm.module.flags = !{!6, !7, !14}
+!llvm.dbg.cu = !{!15, !27}
+
+!6 = !{i32 7, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = !{i32 1, !"Swift Version", i32 7}
+!15 = distinct !DICompileUnit(language: DW_LANG_Swift, file: !16, producer: "Swift", emissionKind: LineTablesOnly)
+!16 = !DIFile(filename: "t.swift", directory: "/tmp")
+!17 = !{}
+!27 = distinct !DICompileUnit(language: DW_LANG_ObjC, file: !16, emissionKind: LineTablesOnly)
+!35 = distinct !DISubprogram(name: "f", linkageName: "$s1t1f1bySb_tF", scope: !15, file: !16, line: 1, type: !36, scopeLine: 1, spFlags: DISPFlagDefinition, unit: !15, retainedNodes: !17)
+!36 = !DISubroutineType(types: null)
+!37 = !DILocation(line: 0, scope: !35)
+!38 = !DILocation(line: 2, column: 9, scope: !35)
+!39 = !DILocation(line: 3, column: 1, scope: !35)
+!40 = !DILocation(line: 2, column: 18, scope: !35)