; LLVM IR from ahampriyanshu/algo-ds-101 :: Data-Structures/LinkedList/Circular_Linked_List (CircularLinkedList)

; 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 }

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

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

6:                                                ; preds = %0
  store i32 0, ptr %1, align 4
  store i32 1, ptr %3, align 4
  br label %23

7:                                                ; preds = %0
  %8 = load ptr, ptr @head, align 8, !tbaa !9
  %9 = getelementptr inbounds %struct.node, ptr %8, i32 0, i32 2
  %10 = load ptr, ptr %9, align 8, !tbaa !11
  store ptr %10, ptr @current, align 8, !tbaa !9
  br label %11

11:                                               ; preds = %15, %7
  %12 = load ptr, ptr @current, align 8, !tbaa !9
  %13 = load ptr, ptr @head, align 8, !tbaa !9
  %14 = icmp ne ptr %12, %13
  br i1 %14, label %15, label %21

15:                                               ; preds = %11
  %16 = load i32, ptr %2, align 4, !tbaa !5
  %17 = add nsw i32 %16, 1
  store i32 %17, ptr %2, align 4, !tbaa !5
  %18 = load ptr, ptr @current, align 8, !tbaa !9
  %19 = getelementptr inbounds %struct.node, ptr %18, i32 0, i32 2
  %20 = load ptr, ptr %19, align 8, !tbaa !11
  store ptr %20, ptr @current, align 8, !tbaa !9
  br label %11, !llvm.loop !13

21:                                               ; preds = %11
  %22 = load i32, ptr %2, align 4, !tbaa !5
  store i32 %22, ptr %1, align 4
  store i32 1, ptr %3, align 4
  br label %23

23:                                               ; preds = %21, %6
  call void @llvm.lifetime.end.p0(i64 4, ptr %2) #2
  %24 = load i32, ptr %1, align 4
  ret i32 %24
}

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #1

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" }
attributes #1 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
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, !10, i64 8}
!12 = !{!"node", !6, i64 0, !6, i64 4, !10, 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"

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

; Function Attrs: nofree norecurse nosync nounwind memory(readwrite, argmem: read, inaccessiblemem: none) uwtable
define dso_local i32 @length() local_unnamed_addr #0 {
  %1 = load ptr, ptr @head, align 8, !tbaa !5
  %2 = icmp eq ptr %1, null
  br i1 %2, label %4, label %.preheader

.preheader:                                       ; preds = %0, %.preheader
  %.pn = phi ptr [ %storemerge, %.preheader ], [ %1, %0 ]
  %.0 = phi i32 [ %3, %.preheader ], [ 0, %0 ]
  %storemerge.in = getelementptr inbounds i8, ptr %.pn, i64 8
  %storemerge = load ptr, ptr %storemerge.in, align 8, !tbaa !9
  %.not = icmp eq ptr %storemerge, %1
  %3 = add nuw nsw i32 %.0, 1
  br i1 %.not, label %.loopexit, label %.preheader, !llvm.loop !12

.loopexit:                                        ; preds = %.preheader
  store ptr %storemerge, ptr @current, align 8, !tbaa !5
  br label %4

4:                                                ; preds = %.loopexit, %0
  %.03 = phi i32 [ 0, %0 ], [ %.0, %.loopexit ]
  ret i32 %.03
}

attributes #0 = { nofree norecurse nosync nounwind memory(readwrite, argmem: 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, !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, !11, i64 4, !6, i64 8}
!11 = !{!"int", !7, i64 0}
!12 = distinct !{!12, !13}
!13 = !{!"llvm.loop.mustprogress"}


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