; LLVM IR from freddiev4/dailyprogrammerchallenges :: Easy Challenges/Challenge 0023 Easy/solutions (solution)

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

; Function Attrs: nounwind uwtable
define dso_local void @split_list(ptr noundef %0, ptr noundef %1, ptr noundef %2) #1 {
  %4 = alloca ptr, align 8
  %5 = alloca ptr, align 8
  %6 = alloca ptr, align 8
  %7 = alloca ptr, align 8
  %8 = alloca ptr, align 8
  %9 = alloca i32, align 4
  store ptr %0, ptr %4, align 8, !tbaa !5
  store ptr %1, ptr %5, align 8, !tbaa !5
  store ptr %2, ptr %6, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %7) #2
  %10 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %10, ptr %7, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %8) #2
  %11 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %11, ptr %8, align 8, !tbaa !5
  %12 = load ptr, ptr %4, align 8, !tbaa !5
  %13 = icmp eq ptr %12, null
  br i1 %13, label %14, label %15

14:                                               ; preds = %3
  store i32 1, ptr %9, align 4
  br label %51

15:                                               ; preds = %3
  br label %16

16:                                               ; preds = %33, %15
  %17 = load ptr, ptr %7, align 8, !tbaa !5
  %18 = icmp ne ptr %17, null
  br i1 %18, label %19, label %31

19:                                               ; preds = %16
  %20 = load ptr, ptr %7, align 8, !tbaa !5
  %21 = getelementptr inbounds %struct.l_node, ptr %20, i32 0, i32 1
  %22 = load ptr, ptr %21, align 8, !tbaa !9
  %23 = icmp ne ptr %22, null
  br i1 %23, label %24, label %31

24:                                               ; preds = %19
  %25 = load ptr, ptr %7, align 8, !tbaa !5
  %26 = getelementptr inbounds %struct.l_node, ptr %25, i32 0, i32 1
  %27 = load ptr, ptr %26, align 8, !tbaa !9
  %28 = getelementptr inbounds %struct.l_node, ptr %27, i32 0, i32 1
  %29 = load ptr, ptr %28, align 8, !tbaa !9
  %30 = icmp ne ptr %29, null
  br label %31

31:                                               ; preds = %24, %19, %16
  %32 = phi i1 [ false, %19 ], [ false, %16 ], [ %30, %24 ]
  br i1 %32, label %33, label %42

33:                                               ; preds = %31
  %34 = load ptr, ptr %8, align 8, !tbaa !5
  %35 = getelementptr inbounds %struct.l_node, ptr %34, i32 0, i32 1
  %36 = load ptr, ptr %35, align 8, !tbaa !9
  store ptr %36, ptr %8, align 8, !tbaa !5
  %37 = load ptr, ptr %7, align 8, !tbaa !5
  %38 = getelementptr inbounds %struct.l_node, ptr %37, i32 0, i32 1
  %39 = load ptr, ptr %38, align 8, !tbaa !9
  %40 = getelementptr inbounds %struct.l_node, ptr %39, i32 0, i32 1
  %41 = load ptr, ptr %40, align 8, !tbaa !9
  store ptr %41, ptr %7, align 8, !tbaa !5
  br label %16, !llvm.loop !12

42:                                               ; preds = %31
  %43 = load ptr, ptr %8, align 8, !tbaa !5
  %44 = getelementptr inbounds %struct.l_node, ptr %43, i32 0, i32 1
  %45 = load ptr, ptr %44, align 8, !tbaa !9
  %46 = load ptr, ptr %6, align 8, !tbaa !5
  store ptr %45, ptr %46, align 8, !tbaa !5
  %47 = load ptr, ptr %8, align 8, !tbaa !5
  %48 = getelementptr inbounds %struct.l_node, ptr %47, i32 0, i32 1
  store ptr null, ptr %48, align 8, !tbaa !9
  %49 = load ptr, ptr %4, align 8, !tbaa !5
  %50 = load ptr, ptr %5, align 8, !tbaa !5
  store ptr %49, ptr %50, align 8, !tbaa !5
  store i32 0, ptr %9, align 4
  br label %51

51:                                               ; preds = %42, %14
  call void @llvm.lifetime.end.p0(i64 8, ptr %8) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %7) #2
  %52 = load i32, ptr %9, align 4
  switch i32 %52, label %54 [
    i32 0, label %53
    i32 1, label %53
  ]

53:                                               ; preds = %51, %51
  ret void

54:                                               ; preds = %51
  unreachable
}

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 }

!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 = !{!"l_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: nofree norecurse nosync nounwind memory(readwrite, inaccessiblemem: none) uwtable
define dso_local void @split_list(ptr noundef %0, ptr nocapture noundef writeonly %1, ptr nocapture noundef writeonly %2) local_unnamed_addr #0 {
  %4 = icmp eq ptr %0, null
  br i1 %4, label %17, label %.preheader

.preheader:                                       ; preds = %3
  %5 = getelementptr inbounds i8, ptr %0, i64 8
  %6 = load ptr, ptr %5, align 8, !tbaa !5
  %.not18 = icmp eq ptr %6, null
  br i1 %.not18, label %.critedge, label %.lr.ph

.lr.ph:                                           ; preds = %.preheader, %10
  %7 = phi ptr [ %14, %10 ], [ %6, %.preheader ]
  %.019 = phi ptr [ %12, %10 ], [ %0, %.preheader ]
  %8 = getelementptr inbounds i8, ptr %7, i64 8
  %9 = load ptr, ptr %8, align 8, !tbaa !5
  %.not17 = icmp eq ptr %9, null
  br i1 %.not17, label %.critedge.loopexit, label %10

10:                                               ; preds = %.lr.ph
  %11 = getelementptr inbounds i8, ptr %.019, i64 8
  %12 = load ptr, ptr %11, align 8, !tbaa !5
  %13 = getelementptr inbounds i8, ptr %9, i64 8
  %14 = load ptr, ptr %13, align 8, !tbaa !5
  %.not = icmp eq ptr %14, null
  br i1 %.not, label %.critedge.loopexit, label %.lr.ph, !llvm.loop !11

.critedge.loopexit:                               ; preds = %10, %.lr.ph
  %.0.lcssa.ph = phi ptr [ %.019, %.lr.ph ], [ %12, %10 ]
  %.phi.trans.insert = getelementptr inbounds i8, ptr %.0.lcssa.ph, i64 8
  %.pre = load ptr, ptr %.phi.trans.insert, align 8, !tbaa !5
  br label %.critedge

.critedge:                                        ; preds = %.critedge.loopexit, %.preheader
  %15 = phi ptr [ null, %.preheader ], [ %.pre, %.critedge.loopexit ]
  %.0.lcssa = phi ptr [ %0, %.preheader ], [ %.0.lcssa.ph, %.critedge.loopexit ]
  %16 = getelementptr inbounds i8, ptr %.0.lcssa, i64 8
  store ptr %15, ptr %2, align 8, !tbaa !13
  store ptr null, ptr %16, align 8, !tbaa !5
  store ptr %0, ptr %1, align 8, !tbaa !13
  br label %17

17:                                               ; preds = %3, %.critedge
  ret void
}

attributes #0 = { nofree norecurse nosync nounwind memory(readwrite, inaccessiblemem: none) 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 = !{!"l_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"}
!13 = !{!10, !10, i64 0}


; Effective O3 passes: EarlyCSEPass,GVNPass,GlobalOptPass,IPSCCPPass,InferFunctionAttrsPass,InstCombinePass,LCSSAPass,LoopRotatePass,LoopSimplifyPass,LoopUnrollPass,PostOrderFunctionAttrsPass,SROAPass,SimplifyCFGPass