; LLVM IR from UtkarshPathrabe/Competitive-Coding :: HackerRank Solutions/Data Structures/Linked Lists (Reverse a doubly 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"

%class.DoublyLinkedListNode = type { i32, ptr, 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: mustprogress nounwind uwtable
define dso_local noundef ptr @_Z7reverseP20DoublyLinkedListNode(ptr noundef %0) #1 {
  %2 = alloca ptr, align 8
  %3 = alloca ptr, align 8
  %4 = alloca ptr, align 8
  %5 = alloca i32, align 4
  store ptr %0, ptr %3, align 8, !tbaa !5
  %6 = load ptr, ptr %3, align 8, !tbaa !5
  %7 = icmp eq ptr %6, null
  br i1 %7, label %8, label %9

8:                                                ; preds = %1
  store ptr null, ptr %2, align 8
  br label %40

9:                                                ; preds = %1
  br label %10

10:                                               ; preds = %37, %9
  %11 = load ptr, ptr %3, align 8, !tbaa !5
  %12 = icmp ne ptr %11, null
  br i1 %12, label %13, label %38

13:                                               ; preds = %10
  call void @llvm.lifetime.start.p0(i64 8, ptr %4) #2
  %14 = load ptr, ptr %3, align 8, !tbaa !5
  %15 = getelementptr inbounds %class.DoublyLinkedListNode, ptr %14, i32 0, i32 2
  %16 = load ptr, ptr %15, align 8, !tbaa !9
  store ptr %16, ptr %4, align 8, !tbaa !5
  %17 = load ptr, ptr %3, align 8, !tbaa !5
  %18 = getelementptr inbounds %class.DoublyLinkedListNode, ptr %17, i32 0, i32 1
  %19 = load ptr, ptr %18, align 8, !tbaa !12
  %20 = load ptr, ptr %3, align 8, !tbaa !5
  %21 = getelementptr inbounds %class.DoublyLinkedListNode, ptr %20, i32 0, i32 2
  store ptr %19, ptr %21, align 8, !tbaa !9
  %22 = load ptr, ptr %4, align 8, !tbaa !5
  %23 = load ptr, ptr %3, align 8, !tbaa !5
  %24 = getelementptr inbounds %class.DoublyLinkedListNode, ptr %23, i32 0, i32 1
  store ptr %22, ptr %24, align 8, !tbaa !12
  %25 = load ptr, ptr %3, align 8, !tbaa !5
  %26 = getelementptr inbounds %class.DoublyLinkedListNode, ptr %25, i32 0, i32 2
  %27 = load ptr, ptr %26, align 8, !tbaa !9
  %28 = icmp eq ptr %27, null
  br i1 %28, label %29, label %31

29:                                               ; preds = %13
  %30 = load ptr, ptr %3, align 8, !tbaa !5
  store ptr %30, ptr %2, align 8
  store i32 1, ptr %5, align 4
  br label %35

31:                                               ; preds = %13
  %32 = load ptr, ptr %3, align 8, !tbaa !5
  %33 = getelementptr inbounds %class.DoublyLinkedListNode, ptr %32, i32 0, i32 2
  %34 = load ptr, ptr %33, align 8, !tbaa !9
  store ptr %34, ptr %3, align 8, !tbaa !5
  store i32 0, ptr %5, align 4
  br label %35

35:                                               ; preds = %31, %29
  call void @llvm.lifetime.end.p0(i64 8, ptr %4) #2
  %36 = load i32, ptr %5, align 4
  switch i32 %36, label %42 [
    i32 0, label %37
    i32 1, label %40
  ]

37:                                               ; preds = %35
  br label %10, !llvm.loop !13

38:                                               ; preds = %10
  %39 = load ptr, ptr %3, align 8, !tbaa !5
  store ptr %39, ptr %2, align 8
  br label %40

40:                                               ; preds = %38, %35, %8
  %41 = load ptr, ptr %2, align 8
  ret ptr %41

42:                                               ; preds = %35
  unreachable
}

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #1 = { mustprogress 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++ TBAA"}
!9 = !{!10, !6, i64 16}
!10 = !{!"_ZTS20DoublyLinkedListNode", !11, i64 0, !6, i64 8, !6, i64 16}
!11 = !{!"int", !7, i64 0}
!12 = !{!10, !6, i64 8}
!13 = distinct !{!13, !14}
!14 = !{!"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: mustprogress nofree norecurse nosync nounwind memory(readwrite, inaccessiblemem: none) uwtable
define dso_local noundef ptr @_Z7reverseP20DoublyLinkedListNode(ptr noundef %0) local_unnamed_addr #0 {
  %2 = icmp eq ptr %0, null
  br i1 %2, label %.loopexit, label %.preheader

.preheader:                                       ; preds = %1, %.preheader
  %.013 = phi ptr [ %6, %.preheader ], [ %0, %1 ]
  %3 = getelementptr inbounds i8, ptr %.013, i64 16
  %4 = load ptr, ptr %3, align 8, !tbaa !5
  %5 = getelementptr inbounds i8, ptr %.013, i64 8
  %6 = load ptr, ptr %5, align 8, !tbaa !11
  store ptr %6, ptr %3, align 8, !tbaa !5
  store ptr %4, ptr %5, align 8, !tbaa !11
  %.not = icmp eq ptr %6, null
  br i1 %.not, label %.loopexit, label %.preheader

.loopexit:                                        ; preds = %.preheader, %1
  %.2 = phi ptr [ null, %1 ], [ %.013, %.preheader ]
  ret ptr %.2
}

attributes #0 = { mustprogress 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 16}
!6 = !{!"_ZTS20DoublyLinkedListNode", !7, i64 0, !10, i64 8, !10, i64 16}
!7 = !{!"int", !8, i64 0}
!8 = !{!"omnipotent char", !9, i64 0}
!9 = !{!"Simple C++ TBAA"}
!10 = !{!"any pointer", !8, i64 0}
!11 = !{!6, !10, i64 8}


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