; LLVM IR from sbshah97/DS-Algo-Handbook :: Data-Structures/Linked_List/Doubly_Linked_List (doubly)

; 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, i32, ptr, ptr }

@head = external dso_local global ptr, align 8
@last = external dso_local global ptr, align 8

; 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 ptr @delete(i32 noundef %0) #1 {
  %2 = alloca ptr, align 8
  %3 = alloca i32, align 4
  %4 = alloca ptr, align 8
  %5 = alloca ptr, align 8
  %6 = alloca i32, align 4
  store i32 %0, ptr %3, align 4, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %4) #2
  %7 = load ptr, ptr @head, align 8, !tbaa !9
  store ptr %7, ptr %4, align 8, !tbaa !9
  call void @llvm.lifetime.start.p0(i64 8, ptr %5) #2
  store ptr null, ptr %5, align 8, !tbaa !9
  %8 = load ptr, ptr @head, align 8, !tbaa !9
  %9 = icmp eq ptr %8, null
  br i1 %9, label %10, label %11

10:                                               ; preds = %1
  store ptr null, ptr %2, align 8
  store i32 1, ptr %6, align 4
  br label %64

11:                                               ; preds = %1
  br label %12

12:                                               ; preds = %29, %11
  %13 = load ptr, ptr %4, align 8, !tbaa !9
  %14 = getelementptr inbounds %struct.node, ptr %13, i32 0, i32 1
  %15 = load i32, ptr %14, align 4, !tbaa !11
  %16 = load i32, ptr %3, align 4, !tbaa !5
  %17 = icmp ne i32 %15, %16
  br i1 %17, label %18, label %30

18:                                               ; preds = %12
  %19 = load ptr, ptr %4, align 8, !tbaa !9
  %20 = getelementptr inbounds %struct.node, ptr %19, i32 0, i32 2
  %21 = load ptr, ptr %20, align 8, !tbaa !13
  %22 = icmp eq ptr %21, null
  br i1 %22, label %23, label %24

23:                                               ; preds = %18
  store ptr null, ptr %2, align 8
  store i32 1, ptr %6, align 4
  br label %64

24:                                               ; preds = %18
  %25 = load ptr, ptr %4, align 8, !tbaa !9
  store ptr %25, ptr %5, align 8, !tbaa !9
  %26 = load ptr, ptr %4, align 8, !tbaa !9
  %27 = getelementptr inbounds %struct.node, ptr %26, i32 0, i32 2
  %28 = load ptr, ptr %27, align 8, !tbaa !13
  store ptr %28, ptr %4, align 8, !tbaa !9
  br label %29

29:                                               ; preds = %24
  br label %12, !llvm.loop !14

30:                                               ; preds = %12
  %31 = load ptr, ptr %4, align 8, !tbaa !9
  %32 = load ptr, ptr @head, align 8, !tbaa !9
  %33 = icmp eq ptr %31, %32
  br i1 %33, label %34, label %38

34:                                               ; preds = %30
  %35 = load ptr, ptr @head, align 8, !tbaa !9
  %36 = getelementptr inbounds %struct.node, ptr %35, i32 0, i32 2
  %37 = load ptr, ptr %36, align 8, !tbaa !13
  store ptr %37, ptr @head, align 8, !tbaa !9
  br label %46

38:                                               ; preds = %30
  %39 = load ptr, ptr %4, align 8, !tbaa !9
  %40 = getelementptr inbounds %struct.node, ptr %39, i32 0, i32 2
  %41 = load ptr, ptr %40, align 8, !tbaa !13
  %42 = load ptr, ptr %4, align 8, !tbaa !9
  %43 = getelementptr inbounds %struct.node, ptr %42, i32 0, i32 3
  %44 = load ptr, ptr %43, align 8, !tbaa !16
  %45 = getelementptr inbounds %struct.node, ptr %44, i32 0, i32 2
  store ptr %41, ptr %45, align 8, !tbaa !13
  br label %46

46:                                               ; preds = %38, %34
  %47 = load ptr, ptr %4, align 8, !tbaa !9
  %48 = load ptr, ptr @last, align 8, !tbaa !9
  %49 = icmp eq ptr %47, %48
  br i1 %49, label %50, label %54

50:                                               ; preds = %46
  %51 = load ptr, ptr %4, align 8, !tbaa !9
  %52 = getelementptr inbounds %struct.node, ptr %51, i32 0, i32 3
  %53 = load ptr, ptr %52, align 8, !tbaa !16
  store ptr %53, ptr @last, align 8, !tbaa !9
  br label %62

54:                                               ; preds = %46
  %55 = load ptr, ptr %4, align 8, !tbaa !9
  %56 = getelementptr inbounds %struct.node, ptr %55, i32 0, i32 3
  %57 = load ptr, ptr %56, align 8, !tbaa !16
  %58 = load ptr, ptr %4, align 8, !tbaa !9
  %59 = getelementptr inbounds %struct.node, ptr %58, i32 0, i32 2
  %60 = load ptr, ptr %59, align 8, !tbaa !13
  %61 = getelementptr inbounds %struct.node, ptr %60, i32 0, i32 3
  store ptr %57, ptr %61, align 8, !tbaa !16
  br label %62

62:                                               ; preds = %54, %50
  %63 = load ptr, ptr %4, align 8, !tbaa !9
  store ptr %63, ptr %2, align 8
  store i32 1, ptr %6, align 4
  br label %64

64:                                               ; preds = %62, %23, %10
  call void @llvm.lifetime.end.p0(i64 8, ptr %5) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %4) #2
  %65 = load ptr, ptr %2, align 8
  ret ptr %65
}

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 = !{!"int", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}
!9 = !{!10, !10, i64 0}
!10 = !{!"any pointer", !7, i64 0}
!11 = !{!12, !6, i64 4}
!12 = !{!"node", !6, i64 0, !6, i64 4, !10, i64 8, !10, i64 16}
!13 = !{!12, !10, i64 8}
!14 = distinct !{!14, !15}
!15 = !{!"llvm.loop.mustprogress"}
!16 = !{!12, !10, i64 16}


; 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"

@head = external dso_local local_unnamed_addr global ptr, align 8
@last = external dso_local local_unnamed_addr global ptr, align 8

; Function Attrs: nofree norecurse nosync nounwind memory(readwrite, inaccessiblemem: none) uwtable
define dso_local ptr @delete(i32 noundef %0) local_unnamed_addr #0 {
  %2 = load ptr, ptr @head, align 8, !tbaa !5
  %3 = icmp eq ptr %2, null
  br i1 %3, label %.loopexit, label %.preheader

.preheader:                                       ; preds = %1, %6
  %.0 = phi ptr [ %8, %6 ], [ %2, %1 ]
  %4 = getelementptr inbounds i8, ptr %.0, i64 4
  %5 = load i32, ptr %4, align 4, !tbaa !9
  %.not = icmp eq i32 %5, %0
  br i1 %.not, label %10, label %6

6:                                                ; preds = %.preheader
  %7 = getelementptr inbounds i8, ptr %.0, i64 8
  %8 = load ptr, ptr %7, align 8, !tbaa !12
  %9 = icmp eq ptr %8, null
  br i1 %9, label %.loopexit, label %.preheader, !llvm.loop !13

10:                                               ; preds = %.preheader
  %11 = icmp eq ptr %.0, %2
  br i1 %11, label %12, label %15

12:                                               ; preds = %10
  %13 = getelementptr inbounds i8, ptr %2, i64 8
  %14 = load ptr, ptr %13, align 8, !tbaa !12
  store ptr %14, ptr @head, align 8, !tbaa !5
  br label %21

15:                                               ; preds = %10
  %16 = getelementptr inbounds i8, ptr %.0, i64 8
  %17 = load ptr, ptr %16, align 8, !tbaa !12
  %18 = getelementptr inbounds i8, ptr %.0, i64 16
  %19 = load ptr, ptr %18, align 8, !tbaa !15
  %20 = getelementptr inbounds i8, ptr %19, i64 8
  store ptr %17, ptr %20, align 8, !tbaa !12
  br label %21

21:                                               ; preds = %15, %12
  %22 = load ptr, ptr @last, align 8, !tbaa !5
  %23 = icmp eq ptr %.0, %22
  %24 = getelementptr inbounds i8, ptr %.0, i64 16
  %25 = load ptr, ptr %24, align 8, !tbaa !15
  br i1 %23, label %.loopexit.sink.split, label %26

26:                                               ; preds = %21
  %27 = getelementptr inbounds i8, ptr %.0, i64 8
  %28 = load ptr, ptr %27, align 8, !tbaa !12
  %29 = getelementptr inbounds i8, ptr %28, i64 16
  br label %.loopexit.sink.split

.loopexit.sink.split:                             ; preds = %21, %26
  %last.sink = phi ptr [ %29, %26 ], [ @last, %21 ]
  store ptr %25, ptr %last.sink, align 8, !tbaa !5
  br label %.loopexit

.loopexit:                                        ; preds = %6, %.loopexit.sink.split, %1
  %.013 = phi ptr [ null, %1 ], [ %.0, %.loopexit.sink.split ], [ null, %6 ]
  ret ptr %.013
}

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, !6, i64 0}
!6 = !{!"any pointer", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}
!9 = !{!10, !11, i64 4}
!10 = !{!"node", !11, i64 0, !11, i64 4, !6, i64 8, !6, i64 16}
!11 = !{!"int", !7, i64 0}
!12 = !{!10, !6, i64 8}
!13 = distinct !{!13, !14}
!14 = !{!"llvm.loop.mustprogress"}
!15 = !{!10, !6, i64 16}


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