; LLVM IR from JessonYue/LeetCodeLearning :: Array/liangguochang (straits)

; 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 i64 @stairs(i32 noundef %0) #0 {
  %2 = alloca i64, align 8
  %3 = alloca i32, align 4
  store i32 %0, ptr %3, align 4, !tbaa !5
  %4 = load i32, ptr %3, align 4, !tbaa !5
  %5 = icmp slt i32 %4, 1
  br i1 %5, label %6, label %7

6:                                                ; preds = %1
  store i64 0, ptr %2, align 8
  br label %25

7:                                                ; preds = %1
  %8 = load i32, ptr %3, align 4, !tbaa !5
  %9 = icmp eq i32 %8, 1
  br i1 %9, label %10, label %11

10:                                               ; preds = %7
  store i64 1, ptr %2, align 8
  br label %25

11:                                               ; preds = %7
  %12 = load i32, ptr %3, align 4, !tbaa !5
  %13 = icmp eq i32 %12, 2
  br i1 %13, label %14, label %17

14:                                               ; preds = %11
  %15 = call i64 @stairs(i32 noundef 1)
  %16 = add nsw i64 %15, 1
  store i64 %16, ptr %2, align 8
  br label %25

17:                                               ; preds = %11
  %18 = load i32, ptr %3, align 4, !tbaa !5
  %19 = sub nsw i32 %18, 2
  %20 = call i64 @stairs(i32 noundef %19)
  %21 = load i32, ptr %3, align 4, !tbaa !5
  %22 = sub nsw i32 %21, 1
  %23 = call i64 @stairs(i32 noundef %22)
  %24 = add nsw i64 %20, %23
  store i64 %24, ptr %2, align 8
  br label %25

25:                                               ; preds = %17, %14, %10, %6
  %26 = load i64, ptr %2, align 8
  ret i64 %26
}

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" }

!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 = !{!"int", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}


; 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(none) uwtable
define dso_local i64 @stairs(i32 noundef %0) local_unnamed_addr #0 {
  %2 = icmp slt i32 %0, 1
  br i1 %2, label %.loopexit, label %.lr.ph

.lr.ph:                                           ; preds = %1, %tailrecurse
  %.tr10 = phi i32 [ %5, %tailrecurse ], [ %0, %1 ]
  %accumulator.tr9 = phi i64 [ %6, %tailrecurse ], [ 0, %1 ]
  switch i32 %.tr10, label %tailrecurse [
    i32 1, label %.loopexit.loopexit
    i32 2, label %.loopexit
  ]

tailrecurse:                                      ; preds = %.lr.ph
  %3 = add nsw i32 %.tr10, -2
  %4 = tail call i64 @stairs(i32 noundef %3)
  %5 = add nsw i32 %.tr10, -1
  %6 = add nsw i64 %4, %accumulator.tr9
  br label %.lr.ph

.loopexit.loopexit:                               ; preds = %.lr.ph
  br label %.loopexit

.loopexit:                                        ; preds = %.lr.ph, %.loopexit.loopexit, %1
  %accumulator.tr8 = phi i64 [ 0, %1 ], [ %accumulator.tr9, %.loopexit.loopexit ], [ %accumulator.tr9, %.lr.ph ]
  %.0 = phi i64 [ 0, %1 ], [ 1, %.loopexit.loopexit ], [ 2, %.lr.ph ]
  %accumulator.ret.tr = add nsw i64 %.0, %accumulator.tr8
  ret i64 %accumulator.ret.tr
}

attributes #0 = { nofree nosync nounwind memory(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)"}


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