; LLVM IR from ritikbanger/Hacktoberfest2022-DSA :: 10. Linked List/c lang (Linked List)

; Unoptimized IR (clang -disable-llvm-passes):
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.node = type { i32, ptr }

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #0

; Function Attrs: nounwind uwtable
declare dso_local i32 @length(ptr noundef) #1

; Function Attrs: nounwind uwtable
define dso_local ptr @merge(ptr noundef %0, ptr noundef %1) #1 {
  %3 = alloca ptr, align 8
  %4 = alloca ptr, align 8
  %5 = alloca ptr, align 8
  %6 = alloca ptr, align 8
  %7 = alloca i32, align 4
  store ptr %0, ptr %4, align 8, !tbaa !5
  store ptr %1, ptr %5, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %6) #3
  %8 = call noalias ptr @malloc(i64 noundef 16) #4
  store ptr %8, ptr %6, align 8, !tbaa !5
  %9 = load ptr, ptr %4, align 8, !tbaa !5
  %10 = call i32 @length(ptr noundef %9)
  %11 = icmp eq i32 %10, 0
  br i1 %11, label %12, label %14

12:                                               ; preds = %2
  %13 = load ptr, ptr %5, align 8, !tbaa !5
  store ptr %13, ptr %3, align 8
  store i32 1, ptr %7, align 4
  br label %36

14:                                               ; preds = %2
  %15 = load ptr, ptr %5, align 8, !tbaa !5
  %16 = call i32 @length(ptr noundef %15)
  %17 = icmp eq i32 %16, 0
  br i1 %17, label %18, label %20

18:                                               ; preds = %14
  %19 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %19, ptr %3, align 8
  store i32 1, ptr %7, align 4
  br label %36

20:                                               ; preds = %14
  %21 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %21, ptr %6, align 8, !tbaa !5
  br label %22

22:                                               ; preds = %27, %20
  %23 = load ptr, ptr %4, align 8, !tbaa !5
  %24 = getelementptr inbounds %struct.node, ptr %23, i32 0, i32 1
  %25 = load ptr, ptr %24, align 8, !tbaa !9
  %26 = icmp ne ptr %25, null
  br i1 %26, label %27, label %31

27:                                               ; preds = %22
  %28 = load ptr, ptr %4, align 8, !tbaa !5
  %29 = getelementptr inbounds %struct.node, ptr %28, i32 0, i32 1
  %30 = load ptr, ptr %29, align 8, !tbaa !9
  store ptr %30, ptr %4, align 8, !tbaa !5
  br label %22, !llvm.loop !12

31:                                               ; preds = %22
  %32 = load ptr, ptr %5, align 8, !tbaa !5
  %33 = load ptr, ptr %4, align 8, !tbaa !5
  %34 = getelementptr inbounds %struct.node, ptr %33, i32 0, i32 1
  store ptr %32, ptr %34, align 8, !tbaa !9
  %35 = load ptr, ptr %6, align 8, !tbaa !5
  store ptr %35, ptr %3, align 8
  store i32 1, ptr %7, align 4
  br label %36

36:                                               ; preds = %31, %18, %12
  call void @llvm.lifetime.end.p0(i64 8, ptr %6) #3
  %37 = load ptr, ptr %3, align 8
  ret ptr %37
}

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #0

; Function Attrs: nounwind allocsize(0)
declare noalias ptr @malloc(i64 noundef) #2

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #1 = { nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #2 = { nounwind allocsize(0) "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #3 = { nounwind }
attributes #4 = { nounwind allocsize(0) }

!llvm.module.flags = !{!0, !1, !2, !3}
!llvm.ident = !{!4}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 8, !"PIC Level", i32 2}
!2 = !{i32 7, !"PIE Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 2}
!4 = !{!"clang version 19.1.0 (git@github.com:llvm/llvm-project.git a4bf6cd7cfb1a1421ba92bca9d017b49936c55e4)"}
!5 = !{!6, !6, i64 0}
!6 = !{!"any pointer", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}
!9 = !{!10, !6, i64 8}
!10 = !{!"node", !11, i64 0, !6, i64 8}
!11 = !{!"int", !7, i64 0}
!12 = distinct !{!12, !13}
!13 = !{!"llvm.loop.mustprogress"}


; Optimized IR (opt -passes='default<O3>'):
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; Function Attrs: nounwind uwtable
declare dso_local i32 @length(ptr noundef) local_unnamed_addr #0

; Function Attrs: nounwind uwtable
define dso_local noundef ptr @merge(ptr noundef %0, ptr noundef %1) local_unnamed_addr #0 {
  %3 = tail call i32 @length(ptr noundef %0)
  %4 = icmp eq i32 %3, 0
  br i1 %4, label %12, label %5

5:                                                ; preds = %2
  %6 = tail call i32 @length(ptr noundef %1)
  %7 = icmp eq i32 %6, 0
  br i1 %7, label %12, label %.preheader

.preheader:                                       ; preds = %5, %.preheader
  %.011 = phi ptr [ %9, %.preheader ], [ %0, %5 ]
  %8 = getelementptr inbounds i8, ptr %.011, i64 8
  %9 = load ptr, ptr %8, align 8, !tbaa !5
  %.not = icmp eq ptr %9, null
  br i1 %.not, label %10, label %.preheader, !llvm.loop !11

10:                                               ; preds = %.preheader
  %11 = getelementptr inbounds i8, ptr %.011, i64 8
  store ptr %1, ptr %11, align 8, !tbaa !5
  br label %12

12:                                               ; preds = %5, %2, %10
  %.0 = phi ptr [ %0, %10 ], [ %1, %2 ], [ %0, %5 ]
  ret ptr %.0
}

attributes #0 = { nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }

!llvm.module.flags = !{!0, !1, !2, !3}
!llvm.ident = !{!4}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 8, !"PIC Level", i32 2}
!2 = !{i32 7, !"PIE Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 2}
!4 = !{!"clang version 19.1.0 (git@github.com:llvm/llvm-project.git a4bf6cd7cfb1a1421ba92bca9d017b49936c55e4)"}
!5 = !{!6, !10, i64 8}
!6 = !{!"node", !7, i64 0, !10, i64 8}
!7 = !{!"int", !8, i64 0}
!8 = !{!"omnipotent char", !9, i64 0}
!9 = !{!"Simple C/C++ TBAA"}
!10 = !{!"any pointer", !8, i64 0}
!11 = distinct !{!11, !12}
!12 = !{!"llvm.loop.mustprogress"}


; Effective O3 passes: EarlyCSEPass,GVNPass,GlobalOptPass,InferFunctionAttrsPass,InstCombinePass,InstSimplifyPass,LCSSAPass,LICMPass,LoopSimplifyPass,LoopUnrollPass,PostOrderFunctionAttrsPass,SROAPass,SimplifyCFGPass,TailCallElimPass