; LLVM IR from KishanBGajera/2024-366-Days-Of-DSA :: Algorithms/Two Pointers - Hare and Tortoise Algorithm/Cycle or Loop Detection (getNodeAt)

; 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.LinkedList = type { ptr, i32 }
%struct.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 ptr @getNodeAt(ptr noundef %0, i32 noundef %1) #1 {
  %3 = alloca ptr, align 8
  %4 = alloca ptr, align 8
  %5 = alloca i32, align 4
  %6 = alloca i32, align 4
  %7 = alloca ptr, align 8
  store ptr %0, ptr %4, align 8, !tbaa !5
  store i32 %1, ptr %5, align 4, !tbaa !9
  %8 = load ptr, ptr %4, align 8, !tbaa !5
  %9 = getelementptr inbounds %struct.LinkedList, ptr %8, i32 0, i32 0
  %10 = load ptr, ptr %9, align 8, !tbaa !11
  %11 = icmp ne ptr %10, null
  br i1 %11, label %13, label %12

12:                                               ; preds = %2
  store ptr null, ptr %3, align 8
  br label %29

13:                                               ; preds = %2
  call void @llvm.lifetime.start.p0(i64 4, ptr %6) #2
  store i32 0, ptr %6, align 4, !tbaa !9
  call void @llvm.lifetime.start.p0(i64 8, ptr %7) #2
  %14 = load ptr, ptr %4, align 8, !tbaa !5
  %15 = getelementptr inbounds %struct.LinkedList, ptr %14, i32 0, i32 0
  %16 = load ptr, ptr %15, align 8, !tbaa !11
  store ptr %16, ptr %7, align 8, !tbaa !5
  br label %17

17:                                               ; preds = %21, %13
  %18 = load i32, ptr %6, align 4, !tbaa !9
  %19 = load i32, ptr %5, align 4, !tbaa !9
  %20 = icmp ne i32 %18, %19
  br i1 %20, label %21, label %27

21:                                               ; preds = %17
  %22 = load i32, ptr %6, align 4, !tbaa !9
  %23 = add nsw i32 %22, 1
  store i32 %23, ptr %6, align 4, !tbaa !9
  %24 = load ptr, ptr %7, align 8, !tbaa !5
  %25 = getelementptr inbounds %struct.Node, ptr %24, i32 0, i32 1
  %26 = load ptr, ptr %25, align 8, !tbaa !13
  store ptr %26, ptr %7, align 8, !tbaa !5
  br label %17, !llvm.loop !15

27:                                               ; preds = %17
  %28 = load ptr, ptr %7, align 8, !tbaa !5
  store ptr %28, ptr %3, align 8
  call void @llvm.lifetime.end.p0(i64 8, ptr %7) #2
  call void @llvm.lifetime.end.p0(i64 4, ptr %6) #2
  br label %29

29:                                               ; preds = %27, %12
  %30 = load ptr, ptr %3, align 8
  ret ptr %30
}

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, !10, i64 0}
!10 = !{!"int", !7, i64 0}
!11 = !{!12, !6, i64 0}
!12 = !{!"LinkedList", !6, i64 0, !10, i64 8}
!13 = !{!14, !6, i64 8}
!14 = !{!"Node", !10, i64 0, !6, i64 8}
!15 = distinct !{!15, !16}
!16 = !{!"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 @getNodeAt(ptr nocapture noundef readonly %0, i32 noundef %1) local_unnamed_addr #0 {
  %3 = load ptr, ptr %0, align 8, !tbaa !5
  %.not = icmp eq ptr %3, null
  br i1 %.not, label %.loopexit, label %.preheader

.preheader:                                       ; preds = %2
  %.not1011 = icmp eq i32 %1, 0
  br i1 %.not1011, label %.loopexit, label %.lr.ph.preheader

.lr.ph.preheader:                                 ; preds = %.preheader
  %xtraiter = and i32 %1, 7
  %4 = icmp ult i32 %1, 8
  br i1 %4, label %.loopexit.loopexit.unr-lcssa, label %.lr.ph.preheader.new

.lr.ph.preheader.new:                             ; preds = %.lr.ph.preheader
  %unroll_iter = and i32 %1, -8
  br label %.lr.ph

.lr.ph:                                           ; preds = %.lr.ph, %.lr.ph.preheader.new
  %.013 = phi ptr [ %3, %.lr.ph.preheader.new ], [ %20, %.lr.ph ]
  %niter = phi i32 [ 0, %.lr.ph.preheader.new ], [ %niter.next.7, %.lr.ph ]
  %5 = getelementptr inbounds i8, ptr %.013, i64 8
  %6 = load ptr, ptr %5, align 8, !tbaa !11
  %7 = getelementptr inbounds i8, ptr %6, i64 8
  %8 = load ptr, ptr %7, align 8, !tbaa !11
  %9 = getelementptr inbounds i8, ptr %8, i64 8
  %10 = load ptr, ptr %9, align 8, !tbaa !11
  %11 = getelementptr inbounds i8, ptr %10, i64 8
  %12 = load ptr, ptr %11, align 8, !tbaa !11
  %13 = getelementptr inbounds i8, ptr %12, i64 8
  %14 = load ptr, ptr %13, align 8, !tbaa !11
  %15 = getelementptr inbounds i8, ptr %14, i64 8
  %16 = load ptr, ptr %15, align 8, !tbaa !11
  %17 = getelementptr inbounds i8, ptr %16, i64 8
  %18 = load ptr, ptr %17, align 8, !tbaa !11
  %19 = getelementptr inbounds i8, ptr %18, i64 8
  %20 = load ptr, ptr %19, align 8, !tbaa !11
  %niter.next.7 = add i32 %niter, 8
  %niter.ncmp.7 = icmp eq i32 %niter.next.7, %unroll_iter
  br i1 %niter.ncmp.7, label %.loopexit.loopexit.unr-lcssa, label %.lr.ph, !llvm.loop !13

.loopexit.loopexit.unr-lcssa:                     ; preds = %.lr.ph, %.lr.ph.preheader
  %.lcssa.ph = phi ptr [ poison, %.lr.ph.preheader ], [ %20, %.lr.ph ]
  %.013.unr = phi ptr [ %3, %.lr.ph.preheader ], [ %20, %.lr.ph ]
  %lcmp.mod.not = icmp eq i32 %xtraiter, 0
  br i1 %lcmp.mod.not, label %.loopexit, label %.lr.ph.epil

.lr.ph.epil:                                      ; preds = %.loopexit.loopexit.unr-lcssa, %.lr.ph.epil
  %.013.epil = phi ptr [ %22, %.lr.ph.epil ], [ %.013.unr, %.loopexit.loopexit.unr-lcssa ]
  %epil.iter = phi i32 [ %epil.iter.next, %.lr.ph.epil ], [ 0, %.loopexit.loopexit.unr-lcssa ]
  %21 = getelementptr inbounds i8, ptr %.013.epil, i64 8
  %22 = load ptr, ptr %21, align 8, !tbaa !11
  %epil.iter.next = add i32 %epil.iter, 1
  %epil.iter.cmp.not = icmp eq i32 %epil.iter.next, %xtraiter
  br i1 %epil.iter.cmp.not, label %.loopexit, label %.lr.ph.epil, !llvm.loop !15

.loopexit:                                        ; preds = %.loopexit.loopexit.unr-lcssa, %.lr.ph.epil, %.preheader, %2
  %.08 = phi ptr [ null, %2 ], [ %3, %.preheader ], [ %.lcssa.ph, %.loopexit.loopexit.unr-lcssa ], [ %22, %.lr.ph.epil ]
  ret ptr %.08
}

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


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