; LLVM IR from eyangch/competitive-programming :: Codeforces/1304/b.ll/Z3revNSt7 (cxx1112basic_stringIcSt11char_traitsIcESaIcEEE)

; 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.std::__cxx11::basic_string" = type { %"struct.std::__cxx11::basic_string<char>::_Alloc_hider", i64, %union.anon }
%"struct.std::__cxx11::basic_string<char>::_Alloc_hider" = type { ptr }
%union.anon = type { i64, [8 x i8] }

; Function Attrs: mustprogress uwtable
define dso_local void @_Z3revNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE(ptr dead_on_unwind noalias writable sret(%"class.std::__cxx11::basic_string") align 8 %0, ptr noundef %1) #0 {
  %3 = alloca ptr, align 8
  %4 = alloca ptr, align 8
  %5 = alloca i32, align 4
  store ptr %0, ptr %3, align 8
  store ptr %1, ptr %4, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 4, ptr %5) #4
  store i32 0, ptr %5, align 4, !tbaa !9
  br label %6

6:                                                ; preds = %23, %2
  %7 = load i32, ptr %5, align 4, !tbaa !9
  %8 = sext i32 %7 to i64
  %9 = call noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32) %1) #4
  %10 = udiv i64 %9, 2
  %11 = icmp ult i64 %8, %10
  br i1 %11, label %13, label %12

12:                                               ; preds = %6
  call void @llvm.lifetime.end.p0(i64 4, ptr %5) #4
  br label %26

13:                                               ; preds = %6
  %14 = load i32, ptr %5, align 4, !tbaa !9
  %15 = sext i32 %14 to i64
  %16 = call noundef nonnull align 1 dereferenceable(1) ptr @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEixEm(ptr noundef nonnull align 8 dereferenceable(32) %1, i64 noundef %15)
  %17 = call noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32) %1) #4
  %18 = sub i64 %17, 1
  %19 = load i32, ptr %5, align 4, !tbaa !9
  %20 = sext i32 %19 to i64
  %21 = sub i64 %18, %20
  %22 = call noundef nonnull align 1 dereferenceable(1) ptr @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEixEm(ptr noundef nonnull align 8 dereferenceable(32) %1, i64 noundef %21)
  call void @_ZSt4swapIcENSt9enable_ifIXsr6__and_ISt6__not_ISt15__is_tuple_likeIT_EESt21is_move_constructibleIS3_ESt18is_move_assignableIS3_EEE5valueEvE4typeERS3_SC_(ptr noundef nonnull align 1 dereferenceable(1) %16, ptr noundef nonnull align 1 dereferenceable(1) %22) #4
  br label %23

23:                                               ; preds = %13
  %24 = load i32, ptr %5, align 4, !tbaa !9
  %25 = add nsw i32 %24, 1
  store i32 %25, ptr %5, align 4, !tbaa !9
  br label %6, !llvm.loop !11

26:                                               ; preds = %12
  call void @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC2EOS4_(ptr noundef nonnull align 8 dereferenceable(32) %0, ptr noundef nonnull align 8 dereferenceable(32) %1) #4
  ret void
}

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: mustprogress nounwind uwtable
declare noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32)) #2 align 2

; Function Attrs: inlinehint mustprogress nounwind uwtable
declare dso_local void @_ZSt4swapIcENSt9enable_ifIXsr6__and_ISt6__not_ISt15__is_tuple_likeIT_EESt21is_move_constructibleIS3_ESt18is_move_assignableIS3_EEE5valueEvE4typeERS3_SC_(ptr noundef nonnull align 1 dereferenceable(1), ptr noundef nonnull align 1 dereferenceable(1)) #3

; Function Attrs: mustprogress nounwind uwtable
declare noundef nonnull align 1 dereferenceable(1) ptr @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEixEm(ptr noundef nonnull align 8 dereferenceable(32), i64 noundef) #2 align 2

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: mustprogress nounwind uwtable
declare void @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC2EOS4_(ptr noundef nonnull align 8 dereferenceable(32), ptr noundef nonnull align 8 dereferenceable(32)) unnamed_addr #2 align 2

attributes #0 = { mustprogress 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 = { 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 #3 = { inlinehint 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 #4 = { 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 = 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"

%"class.std::__cxx11::basic_string" = type { %"struct.std::__cxx11::basic_string<char>::_Alloc_hider", i64, %union.anon }
%"struct.std::__cxx11::basic_string<char>::_Alloc_hider" = type { ptr }
%union.anon = type { i64, [8 x i8] }

; Function Attrs: mustprogress nounwind uwtable
define dso_local void @_Z3revNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE(ptr dead_on_unwind noalias writable sret(%"class.std::__cxx11::basic_string") align 8 %0, ptr noundef nonnull %1) local_unnamed_addr #0 {
  %3 = tail call noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32) %1) #2
  %.not = icmp ult i64 %3, 2
  br i1 %.not, label %._crit_edge, label %.lr.ph

._crit_edge:                                      ; preds = %.lr.ph, %2
  tail call void @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC2EOS4_(ptr noundef nonnull align 8 dereferenceable(32) %0, ptr noundef nonnull align 8 dereferenceable(32) %1) #2
  ret void

.lr.ph:                                           ; preds = %2, %.lr.ph
  %indvars.iv = phi i64 [ %indvars.iv.next, %.lr.ph ], [ 0, %2 ]
  %4 = tail call noundef nonnull align 1 dereferenceable(1) ptr @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEixEm(ptr noundef nonnull align 8 dereferenceable(32) %1, i64 noundef %indvars.iv)
  %5 = tail call noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32) %1) #2
  %6 = xor i64 %indvars.iv, -1
  %7 = add i64 %5, %6
  %8 = tail call noundef nonnull align 1 dereferenceable(1) ptr @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEixEm(ptr noundef nonnull align 8 dereferenceable(32) %1, i64 noundef %7)
  tail call void @_ZSt4swapIcENSt9enable_ifIXsr6__and_ISt6__not_ISt15__is_tuple_likeIT_EESt21is_move_constructibleIS3_ESt18is_move_assignableIS3_EEE5valueEvE4typeERS3_SC_(ptr noundef nonnull align 1 dereferenceable(1) %4, ptr noundef nonnull align 1 dereferenceable(1) %8) #2
  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
  %9 = tail call noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32) %1) #2
  %10 = lshr i64 %9, 1
  %11 = icmp ugt i64 %10, %indvars.iv.next
  br i1 %11, label %.lr.ph, label %._crit_edge, !llvm.loop !5
}

; Function Attrs: mustprogress nounwind uwtable
declare noundef i64 @_ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE6lengthEv(ptr noundef nonnull align 8 dereferenceable(32)) local_unnamed_addr #0 align 2

; Function Attrs: inlinehint mustprogress nounwind uwtable
declare dso_local void @_ZSt4swapIcENSt9enable_ifIXsr6__and_ISt6__not_ISt15__is_tuple_likeIT_EESt21is_move_constructibleIS3_ESt18is_move_assignableIS3_EEE5valueEvE4typeERS3_SC_(ptr noundef nonnull align 1 dereferenceable(1), ptr noundef nonnull align 1 dereferenceable(1)) local_unnamed_addr #1

; Function Attrs: mustprogress nounwind uwtable
declare noundef nonnull align 1 dereferenceable(1) ptr @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEixEm(ptr noundef nonnull align 8 dereferenceable(32), i64 noundef) local_unnamed_addr #0 align 2

; Function Attrs: mustprogress nounwind uwtable
declare void @_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEC2EOS4_(ptr noundef nonnull align 8 dereferenceable(32), ptr noundef nonnull align 8 dereferenceable(32)) unnamed_addr #0 align 2

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 = { inlinehint 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 = distinct !{!5, !6}
!6 = !{!"llvm.loop.mustprogress"}


; Effective O3 passes: EarlyCSEPass,GlobalOptPass,IndVarSimplifyPass,InferFunctionAttrsPass,InstCombinePass,JumpThreadingPass,LoopRotatePass,LoopSimplifyPass,LoopUnrollPass,PostOrderFunctionAttrsPass,SROAPass,SimplifyCFGPass,TailCallElimPass