; LLVM IR from kazunetakahashi/atcoder :: 201510_201609/1005_ABC027/C2.ll (Z5depthv)

; 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"

@N = external dso_local global i64, align 8

; Function Attrs: mustprogress nounwind uwtable
define dso_local noundef i32 @_Z5depthv() #0 {
  %1 = alloca i64, align 8
  %2 = alloca i32, align 4
  call void @llvm.lifetime.start.p0(i64 8, ptr %1) #2
  %3 = load i64, ptr @N, align 8, !tbaa !5
  store i64 %3, ptr %1, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 4, ptr %2) #2
  store i32 0, ptr %2, align 4, !tbaa !9
  br label %4

4:                                                ; preds = %7, %0
  %5 = load i64, ptr %1, align 8, !tbaa !5
  %6 = icmp sgt i64 %5, 0
  br i1 %6, label %7, label %12

7:                                                ; preds = %4
  %8 = load i64, ptr %1, align 8, !tbaa !5
  %9 = sdiv i64 %8, 2
  store i64 %9, ptr %1, align 8, !tbaa !5
  %10 = load i32, ptr %2, align 4, !tbaa !9
  %11 = add nsw i32 %10, 1
  store i32 %11, ptr %2, align 4, !tbaa !9
  br label %4, !llvm.loop !11

12:                                               ; preds = %4
  %13 = load i32, ptr %2, align 4, !tbaa !9
  call void @llvm.lifetime.end.p0(i64 4, ptr %2) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %1) #2
  ret i32 %13
}

; 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 = { 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 #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 = !{!"long long", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C++ TBAA"}
!9 = !{!10, !10, i64 0}
!10 = !{!"int", !7, i64 0}
!11 = distinct !{!11, !12}
!12 = !{!"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"

@N = external dso_local local_unnamed_addr global i64, align 8

; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(read, argmem: none, inaccessiblemem: none) uwtable
define dso_local noundef i32 @_Z5depthv() local_unnamed_addr #0 {
  %1 = load i64, ptr @N, align 8, !tbaa !5
  %2 = icmp sgt i64 %1, 0
  br i1 %2, label %.lr.ph, label %._crit_edge

.lr.ph:                                           ; preds = %0, %.lr.ph
  %.06 = phi i32 [ %4, %.lr.ph ], [ 0, %0 ]
  %.045 = phi i64 [ %3, %.lr.ph ], [ %1, %0 ]
  %3 = lshr i64 %.045, 1
  %4 = add nuw nsw i32 %.06, 1
  %.not = icmp ult i64 %.045, 2
  br i1 %.not, label %._crit_edge, label %.lr.ph, !llvm.loop !9

._crit_edge:                                      ; preds = %.lr.ph, %0
  %.0.lcssa = phi i32 [ 0, %0 ], [ %4, %.lr.ph ]
  ret i32 %.0.lcssa
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn memory(read, argmem: none, 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 = !{!"long long", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C++ TBAA"}
!9 = distinct !{!9, !10}
!10 = !{!"llvm.loop.mustprogress"}


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