; LLVM IR from codemistic/Data-Structures-and-Algorithms :: CPP/LINKED LIST/DOUBLY LINKED LIST/middleoflinkedlist.ll (Z9approach1P4nodei)

; 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"

%class.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: mustprogress nounwind uwtable
define dso_local noundef ptr @_Z9approach1P4nodei(ptr noundef %0, i32 noundef %1) #1 {
  %3 = alloca ptr, align 8
  %4 = alloca i32, align 4
  %5 = alloca i32, align 4
  %6 = alloca ptr, align 8
  %7 = alloca i32, align 4
  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 4, ptr %5) #2
  %8 = load i32, ptr %4, align 4, !tbaa !9
  %9 = sdiv i32 %8, 2
  %10 = add nsw i32 %9, 1
  store i32 %10, ptr %5, align 4, !tbaa !9
  call void @llvm.lifetime.start.p0(i64 8, ptr %6) #2
  %11 = load ptr, ptr %3, 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 1, ptr %7, align 4, !tbaa !9
  br label %12

12:                                               ; preds = %16, %2
  %13 = load i32, ptr %7, align 4, !tbaa !9
  %14 = load i32, ptr %5, align 4, !tbaa !9
  %15 = icmp slt i32 %13, %14
  br i1 %15, label %16, label %22

16:                                               ; preds = %12
  %17 = load ptr, ptr %6, align 8, !tbaa !5
  %18 = getelementptr inbounds %class.node, ptr %17, i32 0, i32 1
  %19 = load ptr, ptr %18, align 8, !tbaa !11
  store ptr %19, ptr %6, align 8, !tbaa !5
  %20 = load i32, ptr %7, align 4, !tbaa !9
  %21 = add nsw i32 %20, 1
  store i32 %21, ptr %7, align 4, !tbaa !9
  br label %12, !llvm.loop !13

22:                                               ; preds = %12
  %23 = load ptr, ptr %6, align 8, !tbaa !5
  call void @llvm.lifetime.end.p0(i64 4, ptr %7) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %6) #2
  call void @llvm.lifetime.end.p0(i64 4, ptr %5) #2
  ret ptr %23
}

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"}


; 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 willreturn memory(read, inaccessiblemem: none) uwtable
define dso_local noundef ptr @_Z9approach1P4nodei(ptr noundef readonly %0, i32 noundef %1) local_unnamed_addr #0 {
  %.not7 = icmp slt i32 %1, 2
  br i1 %.not7, label %._crit_edge, label %.lr.ph.preheader

.lr.ph.preheader:                                 ; preds = %2
  %3 = lshr i32 %1, 1
  %4 = add nsw i32 %3, -1
  %xtraiter = and i32 %3, 7
  %5 = icmp ult i32 %4, 7
  br i1 %5, label %._crit_edge.loopexit.unr-lcssa, label %.lr.ph.preheader.new

.lr.ph.preheader.new:                             ; preds = %.lr.ph.preheader
  %unroll_iter = and i32 %3, 1073741816
  br label %.lr.ph

.lr.ph:                                           ; preds = %.lr.ph, %.lr.ph.preheader.new
  %.068 = phi ptr [ %0, %.lr.ph.preheader.new ], [ %21, %.lr.ph ]
  %niter = phi i32 [ 0, %.lr.ph.preheader.new ], [ %niter.next.7, %.lr.ph ]
  %6 = getelementptr inbounds i8, ptr %.068, i64 8
  %7 = load ptr, ptr %6, align 8, !tbaa !5
  %8 = getelementptr inbounds i8, ptr %7, i64 8
  %9 = load ptr, ptr %8, align 8, !tbaa !5
  %10 = getelementptr inbounds i8, ptr %9, i64 8
  %11 = load ptr, ptr %10, align 8, !tbaa !5
  %12 = getelementptr inbounds i8, ptr %11, i64 8
  %13 = load ptr, ptr %12, align 8, !tbaa !5
  %14 = getelementptr inbounds i8, ptr %13, i64 8
  %15 = load ptr, ptr %14, align 8, !tbaa !5
  %16 = getelementptr inbounds i8, ptr %15, i64 8
  %17 = load ptr, ptr %16, align 8, !tbaa !5
  %18 = getelementptr inbounds i8, ptr %17, i64 8
  %19 = load ptr, ptr %18, align 8, !tbaa !5
  %20 = getelementptr inbounds i8, ptr %19, i64 8
  %21 = load ptr, ptr %20, align 8, !tbaa !5
  %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_edge.loopexit.unr-lcssa, label %.lr.ph, !llvm.loop !11

._crit_edge.loopexit.unr-lcssa:                   ; preds = %.lr.ph, %.lr.ph.preheader
  %.lcssa.ph = phi ptr [ poison, %.lr.ph.preheader ], [ %21, %.lr.ph ]
  %.068.unr = phi ptr [ %0, %.lr.ph.preheader ], [ %21, %.lr.ph ]
  %lcmp.mod.not = icmp eq i32 %xtraiter, 0
  br i1 %lcmp.mod.not, label %._crit_edge, label %.lr.ph.epil

.lr.ph.epil:                                      ; preds = %._crit_edge.loopexit.unr-lcssa, %.lr.ph.epil
  %.068.epil = phi ptr [ %23, %.lr.ph.epil ], [ %.068.unr, %._crit_edge.loopexit.unr-lcssa ]
  %epil.iter = phi i32 [ %epil.iter.next, %.lr.ph.epil ], [ 0, %._crit_edge.loopexit.unr-lcssa ]
  %22 = getelementptr inbounds i8, ptr %.068.epil, i64 8
  %23 = load ptr, ptr %22, align 8, !tbaa !5
  %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_edge, label %.lr.ph.epil, !llvm.loop !13

._crit_edge:                                      ; preds = %._crit_edge.loopexit.unr-lcssa, %.lr.ph.epil, %2
  %.06.lcssa = phi ptr [ %0, %2 ], [ %.lcssa.ph, %._crit_edge.loopexit.unr-lcssa ], [ %23, %.lr.ph.epil ]
  ret ptr %.06.lcssa
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn 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 = !{!"_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 = distinct !{!13, !14}
!14 = !{!"llvm.loop.unroll.disable"}


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