; LLVM IR from nonstriater/Learn-Algorithms :: 9 Algorithms Job Interview/codes/1 string (string)

; 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"

; Function Attrs: nounwind uwtable
define dso_local void @revert(ptr noundef %0, ptr noundef %1) #0 {
  %3 = alloca ptr, align 8
  %4 = alloca ptr, align 8
  %5 = alloca ptr, align 8
  %6 = alloca ptr, align 8
  %7 = alloca i8, align 1
  store ptr %0, ptr %3, align 8, !tbaa !5
  store ptr %1, ptr %4, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %5) #2
  %8 = load ptr, ptr %3, align 8, !tbaa !5
  store ptr %8, ptr %5, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %6) #2
  %9 = load ptr, ptr %4, align 8, !tbaa !5
  store ptr %9, ptr %6, align 8, !tbaa !5
  br label %10

10:                                               ; preds = %14, %2
  %11 = load ptr, ptr %5, align 8, !tbaa !5
  %12 = load i8, ptr %11, align 1, !tbaa !9
  %13 = icmp ne i8 %12, 0
  br i1 %13, label %14, label %20

14:                                               ; preds = %10
  %15 = load ptr, ptr %5, align 8, !tbaa !5
  %16 = getelementptr inbounds i8, ptr %15, i32 1
  store ptr %16, ptr %5, align 8, !tbaa !5
  %17 = load i8, ptr %15, align 1, !tbaa !9
  %18 = load ptr, ptr %6, align 8, !tbaa !5
  %19 = getelementptr inbounds i8, ptr %18, i32 1
  store ptr %19, ptr %6, align 8, !tbaa !5
  store i8 %17, ptr %18, align 1, !tbaa !9
  br label %10, !llvm.loop !10

20:                                               ; preds = %10
  %21 = load ptr, ptr %6, align 8, !tbaa !5
  store i8 0, ptr %21, align 1, !tbaa !9
  %22 = load ptr, ptr %6, align 8, !tbaa !5
  %23 = getelementptr inbounds i8, ptr %22, i32 -1
  store ptr %23, ptr %6, align 8, !tbaa !5
  br label %24

24:                                               ; preds = %28, %20
  %25 = load ptr, ptr %6, align 8, !tbaa !5
  %26 = load ptr, ptr %4, align 8, !tbaa !5
  %27 = icmp ugt ptr %25, %26
  br i1 %27, label %28, label %40

28:                                               ; preds = %24
  call void @llvm.lifetime.start.p0(i64 1, ptr %7) #2
  %29 = load ptr, ptr %6, align 8, !tbaa !5
  %30 = load i8, ptr %29, align 1, !tbaa !9
  store i8 %30, ptr %7, align 1, !tbaa !9
  %31 = load ptr, ptr %4, align 8, !tbaa !5
  %32 = load i8, ptr %31, align 1, !tbaa !9
  %33 = load ptr, ptr %6, align 8, !tbaa !5
  store i8 %32, ptr %33, align 1, !tbaa !9
  %34 = load i8, ptr %7, align 1, !tbaa !9
  %35 = load ptr, ptr %4, align 8, !tbaa !5
  store i8 %34, ptr %35, align 1, !tbaa !9
  %36 = load ptr, ptr %6, align 8, !tbaa !5
  %37 = getelementptr inbounds i8, ptr %36, i32 -1
  store ptr %37, ptr %6, align 8, !tbaa !5
  %38 = load ptr, ptr %4, align 8, !tbaa !5
  %39 = getelementptr inbounds i8, ptr %38, i32 1
  store ptr %39, ptr %4, align 8, !tbaa !5
  call void @llvm.lifetime.end.p0(i64 1, ptr %7) #2
  br label %24, !llvm.loop !12

40:                                               ; preds = %24
  call void @llvm.lifetime.end.p0(i64 8, ptr %6) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %5) #2
  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: 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 = !{!7, !7, i64 0}
!10 = distinct !{!10, !11}
!11 = !{!"llvm.loop.mustprogress"}
!12 = distinct !{!12, !11}


; 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(readwrite, inaccessiblemem: none) uwtable
define dso_local void @revert(ptr nocapture noundef readonly %0, ptr noundef %1) local_unnamed_addr #0 {
  %3 = load i8, ptr %0, align 1, !tbaa !5
  %.not18 = icmp eq i8 %3, 0
  br i1 %.not18, label %._crit_edge, label %.lr.ph

.lr.ph:                                           ; preds = %2, %.lr.ph
  %4 = phi i8 [ %7, %.lr.ph ], [ %3, %2 ]
  %.01520 = phi ptr [ %6, %.lr.ph ], [ %1, %2 ]
  %.01619 = phi ptr [ %5, %.lr.ph ], [ %0, %2 ]
  %5 = getelementptr inbounds i8, ptr %.01619, i64 1
  %6 = getelementptr inbounds i8, ptr %.01520, i64 1
  store i8 %4, ptr %.01520, align 1, !tbaa !5
  %7 = load i8, ptr %5, align 1, !tbaa !5
  %.not = icmp eq i8 %7, 0
  br i1 %.not, label %._crit_edge, label %.lr.ph, !llvm.loop !8

._crit_edge:                                      ; preds = %.lr.ph, %2
  %.015.lcssa = phi ptr [ %1, %2 ], [ %6, %.lr.ph ]
  store i8 0, ptr %.015.lcssa, align 1, !tbaa !5
  %.121 = getelementptr inbounds i8, ptr %.015.lcssa, i64 -1
  %8 = icmp ugt ptr %.121, %1
  br i1 %8, label %.lr.ph25, label %._crit_edge26

.lr.ph25:                                         ; preds = %._crit_edge, %.lr.ph25
  %.123 = phi ptr [ %.1, %.lr.ph25 ], [ %.121, %._crit_edge ]
  %.022 = phi ptr [ %11, %.lr.ph25 ], [ %1, %._crit_edge ]
  %9 = load i8, ptr %.123, align 1, !tbaa !5
  %10 = load i8, ptr %.022, align 1, !tbaa !5
  store i8 %10, ptr %.123, align 1, !tbaa !5
  store i8 %9, ptr %.022, align 1, !tbaa !5
  %11 = getelementptr inbounds i8, ptr %.022, i64 1
  %.1 = getelementptr inbounds i8, ptr %.123, i64 -1
  %12 = icmp ugt ptr %.1, %11
  br i1 %12, label %.lr.ph25, label %._crit_edge26, !llvm.loop !10

._crit_edge26:                                    ; preds = %.lr.ph25, %._crit_edge
  ret void
}

attributes #0 = { nofree norecurse 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" }

!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 = !{!"omnipotent char", !7, i64 0}
!7 = !{!"Simple C/C++ TBAA"}
!8 = distinct !{!8, !9}
!9 = !{!"llvm.loop.mustprogress"}
!10 = distinct !{!10, !9}


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