; LLVM IR from smv1999/CompetitiveProgrammingQuestionBank :: Data Structures/Linked Lists/Singly Linked List (nth_node_from_last)

; 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, ptr }

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

; Function Attrs: mustprogress nounwind uwtable
define dso_local noundef i32 @_Z14getNthFromLastP4Nodei(ptr noundef %0, i32 noundef %1) #1 {
  %3 = alloca i32, align 4
  %4 = alloca ptr, align 8
  %5 = alloca i32, align 4
  %6 = alloca ptr, align 8
  %7 = alloca i32, align 4
  %8 = alloca i32, align 4
  %9 = alloca i32, align 4
  %10 = alloca i32, align 4
  store ptr %0, ptr %4, align 8, !tbaa !5
  store i32 %1, ptr %5, align 4, !tbaa !9
  call void @llvm.lifetime.start.p0(i64 8, ptr %6) #2
  %11 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %11, ptr %6, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 4, ptr %7) #2
  store i32 0, ptr %7, align 4, !tbaa !9
  br label %12

12:                                               ; preds = %15, %2
  %13 = load ptr, ptr %6, align 8, !tbaa !5
  %14 = icmp ne ptr %13, null
  br i1 %14, label %15, label %21

15:                                               ; preds = %12
  %16 = load i32, ptr %7, align 4, !tbaa !9
  %17 = add nsw i32 %16, 1
  store i32 %17, ptr %7, align 4, !tbaa !9
  %18 = load ptr, ptr %6, align 8, !tbaa !5
  %19 = getelementptr inbounds %struct.Node, ptr %18, i32 0, i32 1
  %20 = load ptr, ptr %19, align 8, !tbaa !11
  store ptr %20, ptr %6, align 8, !tbaa !5
  br label %12, !llvm.loop !13

21:                                               ; preds = %12
  call void @llvm.lifetime.start.p0(i64 4, ptr %8) #2
  %22 = load i32, ptr %7, align 4, !tbaa !9
  %23 = load i32, ptr %5, align 4, !tbaa !9
  %24 = sub nsw i32 %23, 1
  %25 = sub nsw i32 %22, %24
  store i32 %25, ptr %8, align 4, !tbaa !9
  call void @llvm.lifetime.start.p0(i64 4, ptr %9) #2
  store i32 0, ptr %9, align 4, !tbaa !9
  %26 = load i32, ptr %5, align 4, !tbaa !9
  %27 = load i32, ptr %7, align 4, !tbaa !9
  %28 = icmp sgt i32 %26, %27
  br i1 %28, label %29, label %30

29:                                               ; preds = %21
  store i32 -1, ptr %3, align 4
  store i32 1, ptr %10, align 4
  br label %50

30:                                               ; preds = %21
  %31 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %31, ptr %6, align 8, !tbaa !5
  br label %32

32:                                               ; preds = %45, %30
  %33 = load ptr, ptr %6, align 8, !tbaa !5
  %34 = icmp ne ptr %33, null
  br i1 %34, label %35, label %49

35:                                               ; preds = %32
  %36 = load i32, ptr %9, align 4, !tbaa !9
  %37 = add nsw i32 %36, 1
  store i32 %37, ptr %9, align 4, !tbaa !9
  %38 = load i32, ptr %9, align 4, !tbaa !9
  %39 = load i32, ptr %8, align 4, !tbaa !9
  %40 = icmp eq i32 %38, %39
  br i1 %40, label %41, label %45

41:                                               ; preds = %35
  %42 = load ptr, ptr %6, align 8, !tbaa !5
  %43 = getelementptr inbounds %struct.Node, ptr %42, i32 0, i32 0
  %44 = load i32, ptr %43, align 8, !tbaa !15
  store i32 %44, ptr %3, align 4
  store i32 1, ptr %10, align 4
  br label %50

45:                                               ; preds = %35
  %46 = load ptr, ptr %6, align 8, !tbaa !5
  %47 = getelementptr inbounds %struct.Node, ptr %46, i32 0, i32 1
  %48 = load ptr, ptr %47, align 8, !tbaa !11
  store ptr %48, ptr %6, align 8, !tbaa !5
  br label %32, !llvm.loop !16

49:                                               ; preds = %32
  unreachable

50:                                               ; preds = %41, %29
  call void @llvm.lifetime.end.p0(i64 4, ptr %9) #2
  call void @llvm.lifetime.end.p0(i64 4, ptr %8) #2
  call void @llvm.lifetime.end.p0(i64 4, ptr %7) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %6) #2
  %51 = load i32, ptr %3, align 4
  ret i32 %51
}

; 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 = { 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, !10, i64 0}
!10 = !{!"int", !7, i64 0}
!11 = !{!12, !6, i64 8}
!12 = !{!"_ZTS4Node", !10, i64 0, !6, i64 8}
!13 = distinct !{!13, !14}
!14 = !{!"llvm.loop.mustprogress"}
!15 = !{!12, !10, i64 0}
!16 = distinct !{!16, !14}


; 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(read, inaccessiblemem: write) uwtable
define dso_local noundef i32 @_Z14getNthFromLastP4Nodei(ptr noundef readonly %0, i32 noundef %1) local_unnamed_addr #0 {
  %.not20 = icmp eq ptr %0, null
  br i1 %.not20, label %._crit_edge, label %.lr.ph

.lr.ph:                                           ; preds = %2, %.lr.ph
  %.01622 = phi i32 [ %3, %.lr.ph ], [ 0, %2 ]
  %.01721 = phi ptr [ %5, %.lr.ph ], [ %0, %2 ]
  %3 = add nuw nsw i32 %.01622, 1
  %4 = getelementptr inbounds i8, ptr %.01721, i64 8
  %5 = load ptr, ptr %4, align 8, !tbaa !5
  %.not = icmp eq ptr %5, null
  br i1 %.not, label %._crit_edge, label %.lr.ph, !llvm.loop !11

._crit_edge:                                      ; preds = %.lr.ph, %2
  %.016.lcssa = phi i32 [ 0, %2 ], [ %3, %.lr.ph ]
  %reass.sub = sub i32 %.016.lcssa, %1
  %6 = icmp slt i32 %.016.lcssa, %1
  br i1 %6, label %30, label %.preheader

.preheader:                                       ; preds = %._crit_edge
  %7 = icmp ne ptr %0, null
  tail call void @llvm.assume(i1 %7)
  %8 = icmp eq i32 %.016.lcssa, %1
  br i1 %8, label %._crit_edge25, label %.lr.ph24.preheader

.lr.ph24.preheader:                               ; preds = %.preheader
  %xtraiter = and i32 %reass.sub, 7
  %9 = sub i32 %1, %.016.lcssa
  %10 = icmp ugt i32 %9, -8
  br i1 %10, label %._crit_edge25.loopexit.unr-lcssa, label %.lr.ph24.preheader.new

.lr.ph24.preheader.new:                           ; preds = %.lr.ph24.preheader
  %unroll_iter = and i32 %reass.sub, -8
  br label %.lr.ph24

._crit_edge25.loopexit.unr-lcssa:                 ; preds = %.lr.ph24, %.lr.ph24.preheader
  %.lcssa.ph = phi ptr [ poison, %.lr.ph24.preheader ], [ %29, %.lr.ph24 ]
  %.123.unr = phi ptr [ %0, %.lr.ph24.preheader ], [ %29, %.lr.ph24 ]
  %lcmp.mod.not = icmp eq i32 %xtraiter, 0
  br i1 %lcmp.mod.not, label %._crit_edge25, label %.lr.ph24.epil

.lr.ph24.epil:                                    ; preds = %._crit_edge25.loopexit.unr-lcssa, %.lr.ph24.epil
  %.123.epil = phi ptr [ %12, %.lr.ph24.epil ], [ %.123.unr, %._crit_edge25.loopexit.unr-lcssa ]
  %epil.iter = phi i32 [ %epil.iter.next, %.lr.ph24.epil ], [ 0, %._crit_edge25.loopexit.unr-lcssa ]
  %11 = getelementptr inbounds i8, ptr %.123.epil, i64 8
  %12 = load ptr, ptr %11, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %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 %._crit_edge25, label %.lr.ph24.epil, !llvm.loop !14

._crit_edge25:                                    ; preds = %._crit_edge25.loopexit.unr-lcssa, %.lr.ph24.epil, %.preheader
  %.1.lcssa = phi ptr [ %0, %.preheader ], [ %.lcssa.ph, %._crit_edge25.loopexit.unr-lcssa ], [ %12, %.lr.ph24.epil ]
  %13 = load i32, ptr %.1.lcssa, align 8, !tbaa !16
  br label %30

.lr.ph24:                                         ; preds = %.lr.ph24, %.lr.ph24.preheader.new
  %.123 = phi ptr [ %0, %.lr.ph24.preheader.new ], [ %29, %.lr.ph24 ]
  %niter = phi i32 [ 0, %.lr.ph24.preheader.new ], [ %niter.next.7, %.lr.ph24 ]
  %14 = getelementptr inbounds i8, ptr %.123, i64 8
  %15 = load ptr, ptr %14, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %16 = getelementptr inbounds i8, ptr %15, i64 8
  %17 = load ptr, ptr %16, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %18 = getelementptr inbounds i8, ptr %17, i64 8
  %19 = load ptr, ptr %18, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %20 = getelementptr inbounds i8, ptr %19, i64 8
  %21 = load ptr, ptr %20, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %22 = getelementptr inbounds i8, ptr %21, i64 8
  %23 = load ptr, ptr %22, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %24 = getelementptr inbounds i8, ptr %23, i64 8
  %25 = load ptr, ptr %24, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %26 = getelementptr inbounds i8, ptr %25, i64 8
  %27 = load ptr, ptr %26, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %28 = getelementptr inbounds i8, ptr %27, i64 8
  %29 = load ptr, ptr %28, align 8, !tbaa !5, !nonnull !13, !noundef !13
  %niter.next.7 = add i32 %niter, 8
  %niter.ncmp.7 = icmp eq i32 %niter.next.7, %unroll_iter
  br i1 %niter.ncmp.7, label %._crit_edge25.loopexit.unr-lcssa, label %.lr.ph24, !llvm.loop !17

30:                                               ; preds = %._crit_edge, %._crit_edge25
  %.015 = phi i32 [ %13, %._crit_edge25 ], [ -1, %._crit_edge ]
  ret i32 %.015
}

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write)
declare void @llvm.assume(i1 noundef) #1

attributes #0 = { mustprogress nofree norecurse nosync nounwind memory(read, inaccessiblemem: write) 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(inaccessiblemem: write) }

!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 = !{!"_ZTS4Node", !7, i64 0, !10, i64 8}
!7 = !{!"int", !8, i64 0}
!8 = !{!"omnipotent char", !9, i64 0}
!9 = !{!"Simple C++ TBAA"}
!10 = !{!"any pointer", !8, i64 0}
!11 = distinct !{!11, !12}
!12 = !{!"llvm.loop.mustprogress"}
!13 = !{}
!14 = distinct !{!14, !15}
!15 = !{!"llvm.loop.unroll.disable"}
!16 = !{!6, !7, i64 0}
!17 = distinct !{!17, !12}


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