; LLVM IR from facebook/redex :: libredex/IRInstruction.ll (Z18required_bit_widtht)

; 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: 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: mustprogress nounwind uwtable
define dso_local noundef zeroext i8 @_Z18required_bit_widtht(i16 noundef zeroext %0) #1 {
  %2 = alloca i16, align 2
  %3 = alloca i8, align 1
  store i16 %0, ptr %2, align 2, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 1, ptr %3) #2
  store i8 1, ptr %3, align 1, !tbaa !9
  br label %4

4:                                                ; preds = %10, %1
  %5 = load i16, ptr %2, align 2, !tbaa !5
  %6 = zext i16 %5 to i32
  %7 = ashr i32 %6, 1
  %8 = trunc i32 %7 to i16
  store i16 %8, ptr %2, align 2, !tbaa !5
  %9 = icmp ne i16 %8, 0
  br i1 %9, label %10, label %13

10:                                               ; preds = %4
  %11 = load i8, ptr %3, align 1, !tbaa !9
  %12 = add i8 %11, 1
  store i8 %12, ptr %3, align 1, !tbaa !9
  br label %4, !llvm.loop !10

13:                                               ; preds = %4
  %14 = load i8, ptr %3, align 1, !tbaa !9
  call void @llvm.lifetime.end.p0(i64 1, ptr %3) #2
  ret i8 %14
}

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #1 = { 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 #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 = !{!"short", !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"}


; 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 zeroext i8 @_Z18required_bit_widtht(i16 noundef zeroext %0) local_unnamed_addr #0 {
._crit_edge:
  %.not5 = icmp ult i16 %0, 2
  %1 = tail call range(i16 0, 17) i16 @llvm.ctlz.i16(i16 %0, i1 true)
  %2 = trunc nuw nsw i16 %1 to i8
  %3 = sub nuw nsw i8 16, %2
  %.0.lcssa = select i1 %.not5, i8 1, i8 %3
  ret i8 %.0.lcssa
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare i16 @llvm.ctlz.i16(i16, i1 immarg) #1

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" }
attributes #1 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }

!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: GVNPass,GlobalOptPass,IPSCCPPass,IndVarSimplifyPass,InferFunctionAttrsPass,InstCombinePass,LCSSAPass,LoopIdiomRecognizePass,LoopRotatePass,LoopSimplifyPass,PostOrderFunctionAttrsPass,SCCPPass,SROAPass,SimplifyCFGPass,TailCallElimPass