; LLVM IR from JessonYue/LeetCodeLearning :: Array/linchuanxin/Algorithm/day31_0701面试题 02.02. 返回倒数第 k 个节点 (kthToLast)

; 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.ListNode = type { i32, ptr }

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

9:                                                ; preds = %13, %2
  %10 = load i32, ptr %4, align 4, !tbaa !9
  %11 = add nsw i32 %10, -1
  store i32 %11, ptr %4, align 4, !tbaa !9
  %12 = icmp ne i32 %10, 0
  br i1 %12, label %13, label %17

13:                                               ; preds = %9
  %14 = load ptr, ptr %5, align 8, !tbaa !5
  %15 = getelementptr inbounds %struct.ListNode, ptr %14, i32 0, i32 1
  %16 = load ptr, ptr %15, align 8, !tbaa !11
  store ptr %16, ptr %5, align 8, !tbaa !5
  br label %9, !llvm.loop !13

17:                                               ; preds = %9
  br label %18

18:                                               ; preds = %21, %17
  %19 = load ptr, ptr %5, align 8, !tbaa !5
  %20 = icmp ne ptr %19, null
  br i1 %20, label %21, label %28

21:                                               ; preds = %18
  %22 = load ptr, ptr %5, align 8, !tbaa !5
  %23 = getelementptr inbounds %struct.ListNode, ptr %22, i32 0, i32 1
  %24 = load ptr, ptr %23, align 8, !tbaa !11
  store ptr %24, ptr %5, align 8, !tbaa !5
  %25 = load ptr, ptr %6, align 8, !tbaa !5
  %26 = getelementptr inbounds %struct.ListNode, ptr %25, i32 0, i32 1
  %27 = load ptr, ptr %26, align 8, !tbaa !11
  store ptr %27, ptr %6, align 8, !tbaa !5
  br label %18, !llvm.loop !15

28:                                               ; preds = %18
  %29 = load ptr, ptr %6, align 8, !tbaa !5
  %30 = getelementptr inbounds %struct.ListNode, ptr %29, i32 0, i32 0
  %31 = load i32, ptr %30, align 8, !tbaa !16
  call void @llvm.lifetime.end.p0(i64 8, ptr %6) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %5) #2
  ret i32 %31
}

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


; 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 i32 @kthToLast(ptr noundef readonly %0, i32 noundef %1) local_unnamed_addr #0 {
  %.not10 = icmp eq i32 %1, 0
  br i1 %.not10, label %.preheader, label %.lr.ph.preheader

.lr.ph.preheader:                                 ; preds = %2
  %xtraiter = and i32 %1, 7
  %lcmp.mod.not = icmp eq i32 %xtraiter, 0
  br i1 %lcmp.mod.not, label %.lr.ph.prol.loopexit, label %.lr.ph.prol

.lr.ph.prol:                                      ; preds = %.lr.ph.preheader, %.lr.ph.prol
  %.0712.prol = phi ptr [ %5, %.lr.ph.prol ], [ %0, %.lr.ph.preheader ]
  %.0811.prol = phi i32 [ %3, %.lr.ph.prol ], [ %1, %.lr.ph.preheader ]
  %prol.iter = phi i32 [ %prol.iter.next, %.lr.ph.prol ], [ 0, %.lr.ph.preheader ]
  %3 = add nsw i32 %.0811.prol, -1
  %4 = getelementptr inbounds i8, ptr %.0712.prol, i64 8
  %5 = load ptr, ptr %4, align 8, !tbaa !5
  %prol.iter.next = add i32 %prol.iter, 1
  %prol.iter.cmp.not = icmp eq i32 %prol.iter.next, %xtraiter
  br i1 %prol.iter.cmp.not, label %.lr.ph.prol.loopexit, label %.lr.ph.prol, !llvm.loop !11

.lr.ph.prol.loopexit:                             ; preds = %.lr.ph.prol, %.lr.ph.preheader
  %.lcssa21.unr = phi ptr [ poison, %.lr.ph.preheader ], [ %5, %.lr.ph.prol ]
  %.0712.unr = phi ptr [ %0, %.lr.ph.preheader ], [ %5, %.lr.ph.prol ]
  %.0811.unr = phi i32 [ %1, %.lr.ph.preheader ], [ %3, %.lr.ph.prol ]
  %6 = icmp ult i32 %1, 8
  br i1 %6, label %.preheader, label %.lr.ph

.preheader:                                       ; preds = %.lr.ph.prol.loopexit, %.lr.ph, %2
  %.07.lcssa = phi ptr [ %0, %2 ], [ %.lcssa21.unr, %.lr.ph.prol.loopexit ], [ %23, %.lr.ph ]
  %.not913 = icmp eq ptr %.07.lcssa, null
  br i1 %.not913, label %._crit_edge, label %.lr.ph16

.lr.ph:                                           ; preds = %.lr.ph.prol.loopexit, %.lr.ph
  %.0712 = phi ptr [ %23, %.lr.ph ], [ %.0712.unr, %.lr.ph.prol.loopexit ]
  %.0811 = phi i32 [ %21, %.lr.ph ], [ %.0811.unr, %.lr.ph.prol.loopexit ]
  %7 = getelementptr inbounds i8, ptr %.0712, i64 8
  %8 = load ptr, ptr %7, align 8, !tbaa !5
  %9 = getelementptr inbounds i8, ptr %8, i64 8
  %10 = load ptr, ptr %9, align 8, !tbaa !5
  %11 = getelementptr inbounds i8, ptr %10, i64 8
  %12 = load ptr, ptr %11, align 8, !tbaa !5
  %13 = getelementptr inbounds i8, ptr %12, i64 8
  %14 = load ptr, ptr %13, align 8, !tbaa !5
  %15 = getelementptr inbounds i8, ptr %14, i64 8
  %16 = load ptr, ptr %15, align 8, !tbaa !5
  %17 = getelementptr inbounds i8, ptr %16, i64 8
  %18 = load ptr, ptr %17, align 8, !tbaa !5
  %19 = getelementptr inbounds i8, ptr %18, i64 8
  %20 = load ptr, ptr %19, align 8, !tbaa !5
  %21 = add nsw i32 %.0811, -8
  %22 = getelementptr inbounds i8, ptr %20, i64 8
  %23 = load ptr, ptr %22, align 8, !tbaa !5
  %.not.7 = icmp eq i32 %21, 0
  br i1 %.not.7, label %.preheader, label %.lr.ph, !llvm.loop !13

.lr.ph16:                                         ; preds = %.preheader, %.lr.ph16
  %.015 = phi ptr [ %27, %.lr.ph16 ], [ %0, %.preheader ]
  %.114 = phi ptr [ %25, %.lr.ph16 ], [ %.07.lcssa, %.preheader ]
  %24 = getelementptr inbounds i8, ptr %.114, i64 8
  %25 = load ptr, ptr %24, align 8, !tbaa !5
  %26 = getelementptr inbounds i8, ptr %.015, i64 8
  %27 = load ptr, ptr %26, align 8, !tbaa !5
  %.not9 = icmp eq ptr %25, null
  br i1 %.not9, label %._crit_edge, label %.lr.ph16, !llvm.loop !15

._crit_edge:                                      ; preds = %.lr.ph16, %.preheader
  %.0.lcssa = phi ptr [ %0, %.preheader ], [ %27, %.lr.ph16 ]
  %28 = load i32, ptr %.0.lcssa, align 8, !tbaa !16
  ret i32 %28
}

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


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