; LLVM IR from freddiev4/dailyprogrammerchallenges :: Easy Challenges/Challenge 0014 Easy/solutions (solution)

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

10:                                               ; preds = %19, %2
  %11 = load ptr, ptr %6, align 8, !tbaa !5
  %12 = icmp ne ptr %11, null
  br i1 %12, label %13, label %17

13:                                               ; preds = %10
  %14 = load i32, ptr %8, align 4, !tbaa !9
  %15 = load i32, ptr %4, align 4, !tbaa !9
  %16 = icmp slt i32 %14, %15
  br label %17

17:                                               ; preds = %13, %10
  %18 = phi i1 [ false, %10 ], [ %16, %13 ]
  br i1 %18, label %19, label %30

19:                                               ; preds = %17
  %20 = load ptr, ptr %6, align 8, !tbaa !5
  %21 = getelementptr inbounds %struct._L_NODE_, ptr %20, i32 0, i32 1
  %22 = load ptr, ptr %21, align 8, !tbaa !11
  store ptr %22, ptr %7, align 8, !tbaa !5
  %23 = load ptr, ptr %5, align 8, !tbaa !5
  %24 = load ptr, ptr %6, align 8, !tbaa !5
  %25 = getelementptr inbounds %struct._L_NODE_, ptr %24, i32 0, i32 1
  store ptr %23, ptr %25, align 8, !tbaa !11
  %26 = load ptr, ptr %6, align 8, !tbaa !5
  store ptr %26, ptr %5, align 8, !tbaa !5
  %27 = load ptr, ptr %7, align 8, !tbaa !5
  store ptr %27, ptr %6, align 8, !tbaa !5
  %28 = load i32, ptr %8, align 4, !tbaa !9
  %29 = add nsw i32 %28, 1
  store i32 %29, ptr %8, align 4, !tbaa !9
  br label %10, !llvm.loop !13

30:                                               ; preds = %17
  %31 = load ptr, ptr %7, align 8, !tbaa !5
  %32 = icmp ne ptr %31, null
  br i1 %32, label %33, label %39

33:                                               ; preds = %30
  %34 = load ptr, ptr %7, align 8, !tbaa !5
  %35 = load i32, ptr %4, align 4, !tbaa !9
  %36 = call ptr @reverse_in_group(ptr noundef %34, i32 noundef %35)
  %37 = load ptr, ptr %3, align 8, !tbaa !5
  %38 = getelementptr inbounds %struct._L_NODE_, ptr %37, i32 0, i32 1
  store ptr %36, ptr %38, align 8, !tbaa !11
  br label %39

39:                                               ; preds = %33, %30
  %40 = load ptr, ptr %5, align 8, !tbaa !5
  call void @llvm.lifetime.end.p0(i64 4, ptr %8) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %7) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %6) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %5) #2
  ret ptr %40
}

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #1 = { 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/C++ TBAA"}
!9 = !{!10, !10, i64 0}
!10 = !{!"int", !7, i64 0}
!11 = !{!12, !6, i64 8}
!12 = !{!"_L_NODE_", !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: nofree nosync nounwind memory(readwrite, inaccessiblemem: none) uwtable
define dso_local ptr @reverse_in_group(ptr noundef %0, i32 noundef %1) local_unnamed_addr #0 {
  %3 = icmp ne ptr %0, null
  %4 = icmp sgt i32 %1, 0
  tail call void @llvm.assume(i1 %3)
  tail call void @llvm.assume(i1 %4)
  br label %.lr.ph

.lr.ph:                                           ; preds = %2, %.lr.ph
  %.019 = phi i32 [ %7, %.lr.ph ], [ 0, %2 ]
  %.01518 = phi ptr [ %6, %.lr.ph ], [ %0, %2 ]
  %.01617 = phi ptr [ %.01518, %.lr.ph ], [ null, %2 ]
  %5 = getelementptr inbounds i8, ptr %.01518, i64 8
  %6 = load ptr, ptr %5, align 8, !tbaa !5
  store ptr %.01617, ptr %5, align 8, !tbaa !5
  %7 = add nuw nsw i32 %.019, 1
  %8 = icmp ne ptr %6, null
  %9 = icmp ult i32 %7, %1
  %10 = select i1 %8, i1 %9, i1 false
  br i1 %10, label %.lr.ph, label %._crit_edge, !llvm.loop !11

._crit_edge:                                      ; preds = %.lr.ph
  %.not = icmp eq ptr %6, null
  br i1 %.not, label %common.ret27, label %._crit_edge.thread

common.ret27:                                     ; preds = %._crit_edge, %._crit_edge.thread
  ret ptr %.01518

._crit_edge.thread:                               ; preds = %._crit_edge
  %11 = tail call ptr @reverse_in_group(ptr noundef nonnull %6, i32 noundef %1)
  %12 = getelementptr inbounds i8, ptr %0, i64 8
  store ptr %11, ptr %12, align 8, !tbaa !5
  br label %common.ret27
}

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

attributes #0 = { nofree nosync nounwind memory(readwrite, 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" }
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 = !{!"_L_NODE_", !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.mustprogress"}


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