; LLVM IR from UtkarshPathrabe/Competitive-Coding :: Cracking the Coding Interview/Chapter 01/Question02.ll (Z7reversePc)

; 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: mustprogress nounwind uwtable
define dso_local void @_Z7reversePc(ptr noundef %0) #0 {
  %2 = alloca ptr, align 8
  %3 = alloca ptr, align 8
  %4 = alloca i8, align 1
  store ptr %0, ptr %2, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 8, ptr %3) #2
  %5 = load ptr, ptr %2, align 8, !tbaa !5
  store ptr %5, ptr %3, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 1, ptr %4) #2
  %6 = load ptr, ptr %2, align 8, !tbaa !5
  %7 = icmp ne ptr %6, null
  br i1 %7, label %8, label %34

8:                                                ; preds = %1
  br label %9

9:                                                ; preds = %13, %8
  %10 = load ptr, ptr %3, align 8, !tbaa !5
  %11 = load i8, ptr %10, align 1, !tbaa !9
  %12 = icmp ne i8 %11, 0
  br i1 %12, label %13, label %16

13:                                               ; preds = %9
  %14 = load ptr, ptr %3, align 8, !tbaa !5
  %15 = getelementptr inbounds i8, ptr %14, i32 1
  store ptr %15, ptr %3, align 8, !tbaa !5
  br label %9, !llvm.loop !10

16:                                               ; preds = %9
  %17 = load ptr, ptr %3, align 8, !tbaa !5
  %18 = getelementptr inbounds i8, ptr %17, i32 -1
  store ptr %18, ptr %3, align 8, !tbaa !5
  br label %19

19:                                               ; preds = %23, %16
  %20 = load ptr, ptr %2, align 8, !tbaa !5
  %21 = load ptr, ptr %3, align 8, !tbaa !5
  %22 = icmp ult ptr %20, %21
  br i1 %22, label %23, label %33

23:                                               ; preds = %19
  %24 = load ptr, ptr %2, align 8, !tbaa !5
  %25 = load i8, ptr %24, align 1, !tbaa !9
  store i8 %25, ptr %4, align 1, !tbaa !9
  %26 = load ptr, ptr %3, align 8, !tbaa !5
  %27 = load i8, ptr %26, align 1, !tbaa !9
  %28 = load ptr, ptr %2, align 8, !tbaa !5
  %29 = getelementptr inbounds i8, ptr %28, i32 1
  store ptr %29, ptr %2, align 8, !tbaa !5
  store i8 %27, ptr %28, align 1, !tbaa !9
  %30 = load i8, ptr %4, align 1, !tbaa !9
  %31 = load ptr, ptr %3, align 8, !tbaa !5
  %32 = getelementptr inbounds i8, ptr %31, i32 -1
  store ptr %32, ptr %3, align 8, !tbaa !5
  store i8 %30, ptr %31, align 1, !tbaa !9
  br label %19, !llvm.loop !12

33:                                               ; preds = %19
  br label %34

34:                                               ; preds = %33, %1
  call void @llvm.lifetime.end.p0(i64 1, ptr %4) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %3) #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 = { 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 = !{!"any pointer", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple 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: mustprogress nofree norecurse nosync nounwind memory(readwrite, inaccessiblemem: none) uwtable
define dso_local void @_Z7reversePc(ptr noundef %0) local_unnamed_addr #0 {
  %.not = icmp eq ptr %0, null
  br i1 %.not, label %.loopexit, label %.preheader14

.preheader14:                                     ; preds = %1, %.preheader14
  %.011 = phi ptr [ %3, %.preheader14 ], [ %0, %1 ]
  %2 = load i8, ptr %.011, align 1, !tbaa !5
  %.not13 = icmp eq i8 %2, 0
  %3 = getelementptr inbounds i8, ptr %.011, i64 1
  br i1 %.not13, label %.preheader, label %.preheader14, !llvm.loop !8

.preheader:                                       ; preds = %.preheader14
  %.115 = getelementptr inbounds i8, ptr %.011, i64 -1
  %4 = icmp ugt ptr %.115, %0
  br i1 %4, label %.lr.ph, label %.loopexit

.lr.ph:                                           ; preds = %.preheader, %.lr.ph
  %.117 = phi ptr [ %.1, %.lr.ph ], [ %.115, %.preheader ]
  %.016 = phi ptr [ %7, %.lr.ph ], [ %0, %.preheader ]
  %5 = load i8, ptr %.016, align 1, !tbaa !5
  %6 = load i8, ptr %.117, align 1, !tbaa !5
  %7 = getelementptr inbounds i8, ptr %.016, i64 1
  store i8 %6, ptr %.016, align 1, !tbaa !5
  store i8 %5, ptr %.117, align 1, !tbaa !5
  %.1 = getelementptr inbounds i8, ptr %.117, i64 -1
  %8 = icmp ult ptr %7, %.1
  br i1 %8, label %.lr.ph, label %.loopexit, !llvm.loop !10

.loopexit:                                        ; preds = %.lr.ph, %.preheader, %1
  ret void
}

attributes #0 = { mustprogress 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++ TBAA"}
!8 = distinct !{!8, !9}
!9 = !{!"llvm.loop.mustprogress"}
!10 = distinct !{!10, !9}


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