; LLVM IR from kaynewbie/algorithm :: algorithm/CodingInterviews (question-23)

; 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.ListNode = 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
define dso_local ptr @meetingNode(ptr noundef %0) #1 {
  %2 = alloca ptr, align 8
  %3 = alloca ptr, align 8
  %4 = alloca ptr, align 8
  %5 = alloca ptr, align 8
  %6 = alloca i32, align 4
  store ptr %0, ptr %3, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %4) #2
  call void @llvm.lifetime.start.p0(i64 8, ptr %5) #2
  %7 = load ptr, ptr %3, align 8, !tbaa !5
  %8 = icmp eq ptr %7, null
  br i1 %8, label %9, label %10

9:                                                ; preds = %1
  store ptr null, ptr %2, align 8
  store i32 1, ptr %6, align 4
  br label %44

10:                                               ; preds = %1
  %11 = load ptr, ptr %3, align 8, !tbaa !5
  store ptr %11, ptr %4, align 8, !tbaa !5
  %12 = load ptr, ptr %4, align 8, !tbaa !5
  %13 = getelementptr inbounds %struct.ListNode, ptr %12, i32 0, i32 1
  %14 = load ptr, ptr %13, align 8, !tbaa !9
  store ptr %14, ptr %5, align 8, !tbaa !5
  br label %15

15:                                               ; preds = %42, %10
  %16 = load ptr, ptr %4, align 8, !tbaa !5
  %17 = icmp ne ptr %16, null
  br i1 %17, label %18, label %21

18:                                               ; preds = %15
  %19 = load ptr, ptr %5, align 8, !tbaa !5
  %20 = icmp ne ptr %19, null
  br label %21

21:                                               ; preds = %18, %15
  %22 = phi i1 [ false, %15 ], [ %20, %18 ]
  br i1 %22, label %23, label %43

23:                                               ; preds = %21
  %24 = load ptr, ptr %4, align 8, !tbaa !5
  %25 = load ptr, ptr %5, align 8, !tbaa !5
  %26 = icmp eq ptr %24, %25
  br i1 %26, label %27, label %29

27:                                               ; preds = %23
  %28 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %28, ptr %2, align 8
  store i32 1, ptr %6, align 4
  br label %44

29:                                               ; preds = %23
  %30 = load ptr, ptr %4, align 8, !tbaa !5
  %31 = getelementptr inbounds %struct.ListNode, ptr %30, i32 0, i32 1
  %32 = load ptr, ptr %31, align 8, !tbaa !9
  store ptr %32, ptr %4, align 8, !tbaa !5
  %33 = load ptr, ptr %5, align 8, !tbaa !5
  %34 = getelementptr inbounds %struct.ListNode, ptr %33, i32 0, i32 1
  %35 = load ptr, ptr %34, align 8, !tbaa !9
  store ptr %35, ptr %5, align 8, !tbaa !5
  %36 = load ptr, ptr %5, align 8, !tbaa !5
  %37 = icmp ne ptr %36, null
  br i1 %37, label %38, label %42

38:                                               ; preds = %29
  %39 = load ptr, ptr %5, align 8, !tbaa !5
  %40 = getelementptr inbounds %struct.ListNode, ptr %39, i32 0, i32 1
  %41 = load ptr, ptr %40, align 8, !tbaa !9
  store ptr %41, ptr %5, align 8, !tbaa !5
  br label %42

42:                                               ; preds = %38, %29
  br label %15, !llvm.loop !12

43:                                               ; preds = %21
  store ptr null, ptr %2, align 8
  store i32 1, ptr %6, align 4
  br label %44

44:                                               ; preds = %43, %27, %9
  call void @llvm.lifetime.end.p0(i64 8, ptr %5) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %4) #2
  %45 = load ptr, ptr %2, align 8
  ret ptr %45
}

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

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 = !{!"ListNode", !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(read, inaccessiblemem: none) uwtable
define dso_local ptr @meetingNode(ptr noundef readonly %0) local_unnamed_addr #0 {
  %2 = icmp eq ptr %0, null
  br i1 %2, label %.loopexit, label %3

3:                                                ; preds = %1
  %4 = getelementptr inbounds i8, ptr %0, i64 8
  %5 = load ptr, ptr %4, align 8, !tbaa !5
  %.not22 = icmp eq ptr %5, null
  br i1 %.not22, label %.loopexit, label %.lr.ph

.lr.ph:                                           ; preds = %3, %10
  %.019 = phi ptr [ %14, %10 ], [ %5, %3 ]
  %.01318 = phi ptr [ %12, %10 ], [ %0, %3 ]
  %6 = icmp eq ptr %.01318, %.019
  br i1 %6, label %.loopexit, label %7

7:                                                ; preds = %.lr.ph
  %8 = getelementptr inbounds i8, ptr %.019, i64 8
  %9 = load ptr, ptr %8, align 8, !tbaa !5
  %.not = icmp eq ptr %9, null
  br i1 %.not, label %.loopexit, label %10

10:                                               ; preds = %7
  %11 = getelementptr inbounds i8, ptr %.01318, 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
  %15 = icmp ne ptr %12, null
  %16 = icmp ne ptr %14, null
  %17 = select i1 %15, i1 %16, i1 false
  br i1 %17, label %.lr.ph, label %.loopexit, !llvm.loop !11

.loopexit:                                        ; preds = %7, %.lr.ph, %10, %3, %1
  %.014 = phi ptr [ null, %1 ], [ null, %3 ], [ null, %7 ], [ %.01318, %.lr.ph ], [ null, %10 ]
  ret ptr %.014
}

attributes #0 = { nofree norecurse nosync nounwind memory(read, 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 = !{!"ListNode", !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: GlobalOptPass,IPSCCPPass,InferFunctionAttrsPass,InstCombinePass,JumpThreadingPass,LoopRotatePass,LoopSimplifyPass,LoopUnrollPass,PostOrderFunctionAttrsPass,SROAPass,SimplifyCFGPass