; LLVM IR from upupming/algorithm :: acwing/算法竞赛进阶指南/0x02-递推与递归/92. 递归实现指数型枚举.ll (Z4pow2i)

; 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 noundef i32 @_Z4pow2i(i32 noundef %0) #0 {
  %2 = alloca i32, align 4
  %3 = alloca i32, align 4
  %4 = alloca i32, align 4
  store i32 %0, ptr %2, align 4, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 4, ptr %3) #2
  store i32 1, ptr %3, align 4, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 4, ptr %4) #2
  store i32 2, ptr %4, align 4, !tbaa !5
  br label %5

5:                                                ; preds = %16, %1
  %6 = load i32, ptr %2, align 4, !tbaa !5
  %7 = icmp sgt i32 %6, 0
  br i1 %7, label %8, label %22

8:                                                ; preds = %5
  %9 = load i32, ptr %2, align 4, !tbaa !5
  %10 = and i32 %9, 1
  %11 = icmp ne i32 %10, 0
  br i1 %11, label %12, label %16

12:                                               ; preds = %8
  %13 = load i32, ptr %4, align 4, !tbaa !5
  %14 = load i32, ptr %3, align 4, !tbaa !5
  %15 = mul nsw i32 %14, %13
  store i32 %15, ptr %3, align 4, !tbaa !5
  br label %16

16:                                               ; preds = %12, %8
  %17 = load i32, ptr %4, align 4, !tbaa !5
  %18 = load i32, ptr %4, align 4, !tbaa !5
  %19 = mul nsw i32 %18, %17
  store i32 %19, ptr %4, align 4, !tbaa !5
  %20 = load i32, ptr %2, align 4, !tbaa !5
  %21 = ashr i32 %20, 1
  store i32 %21, ptr %2, align 4, !tbaa !5
  br label %5, !llvm.loop !9

22:                                               ; preds = %5
  %23 = load i32, ptr %3, align 4, !tbaa !5
  call void @llvm.lifetime.end.p0(i64 4, ptr %4) #2
  call void @llvm.lifetime.end.p0(i64 4, ptr %3) #2
  ret i32 %23
}

; 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 = !{!"int", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C++ TBAA"}
!9 = distinct !{!9, !10}
!10 = !{!"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: mustprogress nofree norecurse nosync nounwind willreturn memory(none) uwtable
define dso_local noundef i32 @_Z4pow2i(i32 noundef %0) local_unnamed_addr #0 {
  %2 = icmp sgt i32 %0, 0
  br i1 %2, label %.lr.ph, label %._crit_edge

.lr.ph:                                           ; preds = %1, %.lr.ph
  %.012 = phi i32 [ %5, %.lr.ph ], [ 2, %1 ]
  %.0811 = phi i32 [ %spec.select, %.lr.ph ], [ 1, %1 ]
  %.0910 = phi i32 [ %6, %.lr.ph ], [ %0, %1 ]
  %3 = and i32 %.0910, 1
  %.not = icmp eq i32 %3, 0
  %4 = select i1 %.not, i32 1, i32 %.012
  %spec.select = mul nsw i32 %4, %.0811
  %5 = mul nsw i32 %.012, %.012
  %6 = lshr i32 %.0910, 1
  %.not13 = icmp ult i32 %.0910, 2
  br i1 %.not13, label %._crit_edge, label %.lr.ph, !llvm.loop !5

._crit_edge:                                      ; preds = %.lr.ph, %1
  %.08.lcssa = phi i32 [ 1, %1 ], [ %spec.select, %.lr.ph ]
  ret i32 %.08.lcssa
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn 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)"}
!5 = distinct !{!5, !6}
!6 = !{!"llvm.loop.mustprogress"}


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