diff --git a/llvm/lib/Transforms/IPO/MergeFunctions.cpp b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
index 89ddd7b6adebb..c19cf71ba4c6a 100644
--- a/llvm/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/llvm/lib/Transforms/IPO/MergeFunctions.cpp
@@ -653,7 +653,7 @@ static bool canCreateThunkFor(Function *F) {
   // Don't merge tiny functions using a thunk, since it can just end up
   // making the function larger.
   if (F->size() == 1) {
-    if (F->front().size() <= 2) {
+    if (F->front().sizeWithoutDebug() < 2) {
       LLVM_DEBUG(dbgs() << "canCreateThunkFor: " << F->getName()
                         << " is too small to bother creating a thunk for\n");
       return false;
diff --git a/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll b/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll
index 13d94f8cf6a25..72aa647ae0b2b 100644
--- a/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll
+++ b/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll
@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
 ; RUN: opt -passes='default<O0>,mergefunc' -S -mergefunc-preserve-debug-info < %s | FileCheck %s --check-prefix=OPTIMIZATION_LEVEL_0
 ; RUN: opt -passes='default<O2>,mergefunc' -S -mergefunc-preserve-debug-info < %s | FileCheck %s --check-prefix=OPTIMIZATION_LEVEL_2
 
@@ -43,6 +44,48 @@
 
 ; Function Attrs: nounwind uwtable
 define i32 @maxA(i32 %x, i32 %y) !dbg !6 {
+; OPTIMIZATION_LEVEL_0-LABEL: define i32 @maxA
+; OPTIMIZATION_LEVEL_0-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) !dbg [[DBG6:![0-9]+]] {
+; OPTIMIZATION_LEVEL_0-NEXT:  entry:
+; OPTIMIZATION_LEVEL_0-NEXT:    [[X_ADDR:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    [[Y_ADDR:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    [[I:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    [[M:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    [[J:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    store i32 [[X]], ptr [[X_ADDR]], align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[X_ADDR]], metadata [[META11:![0-9]+]], metadata !DIExpression()), !dbg [[DBG12:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    store i32 [[Y]], ptr [[Y_ADDR]], align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[Y_ADDR]], metadata [[META13:![0-9]+]], metadata !DIExpression()), !dbg [[DBG14:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[I]], metadata [[META15:![0-9]+]], metadata !DIExpression()), !dbg [[DBG16:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[M]], metadata [[META17:![0-9]+]], metadata !DIExpression()), !dbg [[DBG18:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[J]], metadata [[META19:![0-9]+]], metadata !DIExpression()), !dbg [[DBG20:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    [[TMP0:%.*]] = load i32, ptr [[X_ADDR]], align 4, !dbg [[DBG21:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    [[TMP1:%.*]] = load i32, ptr [[Y_ADDR]], align 4, !dbg [[DBG23:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[TMP0]], [[TMP1]], !dbg [[DBG24:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]], !dbg [[DBG25:![0-9]+]]
+; OPTIMIZATION_LEVEL_0:       if.then:
+; OPTIMIZATION_LEVEL_0-NEXT:    [[TMP2:%.*]] = load i32, ptr [[X_ADDR]], align 4, !dbg [[DBG26:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    store i32 [[TMP2]], ptr [[M]], align 4, !dbg [[DBG27:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    br label [[IF_END:%.*]], !dbg [[DBG28:![0-9]+]]
+; OPTIMIZATION_LEVEL_0:       if.else:
+; OPTIMIZATION_LEVEL_0-NEXT:    [[TMP3:%.*]] = load i32, ptr [[Y_ADDR]], align 4, !dbg [[DBG29:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    store i32 [[TMP3]], ptr [[M]], align 4, !dbg [[DBG30:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    br label [[IF_END]]
+; OPTIMIZATION_LEVEL_0:       if.end:
+; OPTIMIZATION_LEVEL_0-NEXT:    [[TMP4:%.*]] = load i32, ptr [[M]], align 4, !dbg [[DBG31:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    ret i32 [[TMP4]], !dbg [[DBG32:![0-9]+]]
+;
+; OPTIMIZATION_LEVEL_2-LABEL: define i32 @maxA
+; OPTIMIZATION_LEVEL_2-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] !dbg [[DBG6:![0-9]+]] {
+; OPTIMIZATION_LEVEL_2-NEXT:  entry:
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.value(metadata i32 [[X]], metadata [[META11:![0-9]+]], metadata !DIExpression()), !dbg [[DBG12:![0-9]+]]
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.value(metadata i32 [[Y]], metadata [[META13:![0-9]+]], metadata !DIExpression()), !dbg [[DBG12]]
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.declare(metadata ptr undef, metadata [[META14:![0-9]+]], metadata !DIExpression()), !dbg [[DBG15:![0-9]+]]
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.declare(metadata ptr undef, metadata [[META16:![0-9]+]], metadata !DIExpression()), !dbg [[DBG17:![0-9]+]]
+; OPTIMIZATION_LEVEL_2-NEXT:    [[X_Y:%.*]] = tail call i32 @llvm.smax.i32(i32 [[X]], i32 [[Y]])
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.value(metadata i32 [[X_Y]], metadata [[META18:![0-9]+]], metadata !DIExpression()), !dbg [[DBG12]]
+; OPTIMIZATION_LEVEL_2-NEXT:    ret i32 [[X_Y]], !dbg [[DBG19:![0-9]+]]
+;
 entry:
   %x.addr = alloca i32, align 4
   %y.addr = alloca i32, align 4
@@ -81,26 +124,27 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata)
 
 ; Function Attrs: nounwind uwtable
 define i32 @maxB(i32 %x, i32 %y) !dbg !34 {
+; OPTIMIZATION_LEVEL_0-LABEL: define i32 @maxB
+; OPTIMIZATION_LEVEL_0-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) !dbg [[DBG33:![0-9]+]] {
+; OPTIMIZATION_LEVEL_0-NEXT:  entry:
+; OPTIMIZATION_LEVEL_0-NEXT:    [[X_ADDR:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    [[Y_ADDR:%.*]] = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    store i32 [[X]], ptr [[X_ADDR]], align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[X_ADDR]], metadata [[META34:![0-9]+]], metadata !DIExpression()), !dbg [[DBG35:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    store i32 [[Y]], ptr [[Y_ADDR]], align 4
+; OPTIMIZATION_LEVEL_0-NEXT:    call void @llvm.dbg.declare(metadata ptr [[Y_ADDR]], metadata [[META36:![0-9]+]], metadata !DIExpression()), !dbg [[DBG37:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    [[TMP0:%.*]] = tail call i32 @maxA(i32 [[X]], i32 [[Y]]), !dbg [[DBG38:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    ret i32 [[TMP0]], !dbg [[DBG38]]
+;
+; OPTIMIZATION_LEVEL_2-LABEL: define i32 @maxB
+; OPTIMIZATION_LEVEL_2-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) local_unnamed_addr #[[ATTR0]] !dbg [[DBG20:![0-9]+]] {
+; OPTIMIZATION_LEVEL_2-NEXT:  entry:
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.value(metadata i32 [[X]], metadata [[META21:![0-9]+]], metadata !DIExpression()), !dbg [[DBG22:![0-9]+]]
+; OPTIMIZATION_LEVEL_2-NEXT:    call void @llvm.dbg.value(metadata i32 [[Y]], metadata [[META23:![0-9]+]], metadata !DIExpression()), !dbg [[DBG22]]
+; OPTIMIZATION_LEVEL_2-NEXT:    [[TMP0:%.*]] = tail call i32 @maxA(i32 [[X]], i32 [[Y]]) #[[ATTR0]], !dbg [[DBG24:![0-9]+]]
+; OPTIMIZATION_LEVEL_2-NEXT:    ret i32 [[TMP0]], !dbg [[DBG24]]
+;
 
-; OPTIMIZATION_LEVEL_0: define i32 @maxB(i32 %x, i32 %y)
-; OPTIMIZATION_LEVEL_0-NEXT: entry:
-; OPTIMIZATION_LEVEL_0-NEXT: %x.addr = alloca i32, align 4
-; OPTIMIZATION_LEVEL_0-NEXT: %y.addr = alloca i32, align 4
-; OPTIMIZATION_LEVEL_0-NEXT: store i32 %x, ptr %x.addr, align 4
-; OPTIMIZATION_LEVEL_0-NEXT: call void @llvm.dbg.declare(metadata ptr %x.addr, metadata !{{[0-9]+}}, metadata !DIExpression()), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_0-NEXT: store i32 %y, ptr %y.addr, align 4
-; OPTIMIZATION_LEVEL_0-NEXT: call void @llvm.dbg.declare(metadata ptr %y.addr, metadata !{{[0-9]+}}, metadata !DIExpression()), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_0-NEXT: %0 = tail call i32 @maxA(i32 %x, i32 %y), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_0-NEXT: ret i32 %0, !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_0-NEXT: }
-
-; OPTIMIZATION_LEVEL_2: define i32 @maxB(i32 %x, i32 %y)
-; OPTIMIZATION_LEVEL_2-NEXT: entry:
-; OPTIMIZATION_LEVEL_2-NEXT: call void @llvm.dbg.value(metadata i32 %x, metadata !{{[0-9]+}}, metadata !DIExpression()), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_2-NEXT: call void @llvm.dbg.value(metadata i32 %y, metadata !{{[0-9]+}}, metadata !DIExpression()), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_2-NEXT: %0 = tail call i32 @maxA(i32 %x, i32 %y) #{{[0-9]+}}, !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_2-NEXT: ret i32 %0, !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_2-NEXT: }
 
 entry:
   %x.addr = alloca i32, align 4
@@ -137,18 +181,19 @@ if.end:                                           ; preds = %if.else, %if.then
 
 ; Function Attrs: nounwind uwtable
 define void @f() !dbg !57 {
+; OPTIMIZATION_LEVEL_0-LABEL: define void @f
+; OPTIMIZATION_LEVEL_0-SAME: () !dbg [[DBG39:![0-9]+]] {
+; OPTIMIZATION_LEVEL_0-NEXT:  entry:
+; OPTIMIZATION_LEVEL_0-NEXT:    [[CALL:%.*]] = call i32 @maxA(i32 3, i32 4), !dbg [[DBG42:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    [[CALL1:%.*]] = call i32 @maxB(i32 1, i32 9), !dbg [[DBG43:![0-9]+]]
+; OPTIMIZATION_LEVEL_0-NEXT:    ret void, !dbg [[DBG44:![0-9]+]]
+;
+; OPTIMIZATION_LEVEL_2-LABEL: define void @f
+; OPTIMIZATION_LEVEL_2-SAME: () local_unnamed_addr #[[ATTR2:[0-9]+]] !dbg [[DBG25:![0-9]+]] {
+; OPTIMIZATION_LEVEL_2-NEXT:  entry:
+; OPTIMIZATION_LEVEL_2-NEXT:    ret void, !dbg [[DBG28:![0-9]+]]
+;
 entry:
-
-; OPTIMIZATION_LEVEL_0: define void @f()
-; OPTIMIZATION_LEVEL_0-NEXT: entry:
-; OPTIMIZATION_LEVEL_0-NEXT: %call = call i32 @maxA(i32 3, i32 4), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_0-NEXT: %call1 = call i32 @maxB(i32 1, i32 9), !dbg !{{[0-9]+}}
-; OPTIMIZATION_LEVEL_0-NEXT: ret void, !dbg !{{[0-9]+}}
-
-; OPTIMIZATION_LEVEL_2: define void @f()
-; OPTIMIZATION_LEVEL_2-NEXT: entry:
-; OPTIMIZATION_LEVEL_2-NEXT: ret void, !dbg !{{[0-9]+}}
-
   %call = call i32 @maxA(i32 3, i32 4), !dbg !60
   %call1 = call i32 @maxB(i32 1, i32 9), !dbg !61
   ret void, !dbg !62
diff --git a/llvm/test/Transforms/MergeFunc/no-merge-debug-thunks.ll b/llvm/test/Transforms/MergeFunc/no-merge-debug-thunks.ll
new file mode 100644
index 0000000000000..80467c7aee407
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/no-merge-debug-thunks.ll
@@ -0,0 +1,61 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+;; Make sure debug instructions are not counted when deciding to merge functions
+; RUN: opt -S -passes=mergefunc < %s | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+; Function Attrs: nounwind readnone
+define hidden i32 @f(i32 %t) {
+; CHECK-LABEL: define hidden i32 @f
+; CHECK-SAME: (i32 [[T:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @llvm.dbg.value(metadata i32 [[T]], metadata [[META6:![0-9]+]], metadata !DIExpression()), !dbg [[DBG12:![0-9]+]]
+; CHECK-NEXT:    call void @llvm.dbg.value(metadata i32 [[T]], metadata [[META6]], metadata !DIExpression()), !dbg [[DBG12]]
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  call void @llvm.dbg.value(metadata i32 %t, metadata !12, metadata !DIExpression()), !dbg !13
+  call void @llvm.dbg.value(metadata i32 %t, metadata !12, metadata !DIExpression()), !dbg !13
+  ret i32 0
+}
+
+; Function Attrs: nounwind readnone
+define hidden i32 @f_thunk(i32 %t) {
+; CHECK-LABEL: define hidden i32 @f_thunk
+; CHECK-SAME: (i32 [[T:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @llvm.dbg.value(metadata i32 [[T]], metadata [[META6]], metadata !DIExpression()), !dbg [[DBG12]]
+; CHECK-NEXT:    call void @llvm.dbg.value(metadata i32 [[T]], metadata [[META6]], metadata !DIExpression()), !dbg [[DBG12]]
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  call void @llvm.dbg.value(metadata i32 %t, metadata !12, metadata !DIExpression()), !dbg !13
+  call void @llvm.dbg.value(metadata i32 %t, metadata !12, metadata !DIExpression()), !dbg !13
+  ret i32 0
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "no-merge-debug-thunks.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!7 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 3, type: !8, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DILocalVariable(name: "t", arg: 1, scope: !7, file: !1, line: 3, type: !10)
+!13 = !DILocation(line: 3, column: 14, scope: !7)
+!14 = !DILocation(line: 4, column: 12, scope: !7)
+!16 = distinct !DISubprogram(name: "_start", scope: !1, file: !1, line: 7, type: !17, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: true, unit: !0, retainedNodes: !2)
+!17 = !DISubroutineType(types: !18)
+!18 = !{!10}
+!19 = !DILocation(line: 8, column: 3, scope: !16)
+!20 = !DILocation(line: 9, column: 3, scope: !16)