; LLVM IR from facebook/hermes :: external/llvh/lib/Demangle/MicrosoftDemangle.ll (Z22countTrailingNullBytesPKhi)

; 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 i32 @_Z22countTrailingNullBytesPKhi(ptr noundef %0, i32 noundef %1) #1 {
  %3 = alloca ptr, align 8
  %4 = alloca i32, align 4
  %5 = alloca ptr, align 8
  %6 = alloca i32, align 4
  store ptr %0, ptr %3, align 8, !tbaa !5
  store i32 %1, ptr %4, align 4, !tbaa !9
  call void @llvm.lifetime.start.p0(i64 8, ptr %5) #2
  %7 = load ptr, ptr %3, align 8, !tbaa !5
  %8 = load i32, ptr %4, align 4, !tbaa !9
  %9 = sext i32 %8 to i64
  %10 = getelementptr inbounds i8, ptr %7, i64 %9
  %11 = getelementptr inbounds i8, ptr %10, i64 -1
  store ptr %11, ptr %5, align 8, !tbaa !5
  call void @llvm.lifetime.start.p0(i64 4, ptr %6) #2
  store i32 0, ptr %6, align 4, !tbaa !9
  br label %12

12:                                               ; preds = %22, %2
  %13 = load i32, ptr %4, align 4, !tbaa !9
  %14 = icmp sgt i32 %13, 0
  br i1 %14, label %15, label %20

15:                                               ; preds = %12
  %16 = load ptr, ptr %5, align 8, !tbaa !5
  %17 = load i8, ptr %16, align 1, !tbaa !11
  %18 = zext i8 %17 to i32
  %19 = icmp eq i32 %18, 0
  br label %20

20:                                               ; preds = %15, %12
  %21 = phi i1 [ false, %12 ], [ %19, %15 ]
  br i1 %21, label %22, label %29

22:                                               ; preds = %20
  %23 = load i32, ptr %4, align 4, !tbaa !9
  %24 = add nsw i32 %23, -1
  store i32 %24, ptr %4, align 4, !tbaa !9
  %25 = load ptr, ptr %5, align 8, !tbaa !5
  %26 = getelementptr inbounds i8, ptr %25, i32 -1
  store ptr %26, ptr %5, align 8, !tbaa !5
  %27 = load i32, ptr %6, align 4, !tbaa !9
  %28 = add i32 %27, 1
  store i32 %28, ptr %6, align 4, !tbaa !9
  br label %12, !llvm.loop !12

29:                                               ; preds = %20
  %30 = load i32, ptr %6, align 4, !tbaa !9
  call void @llvm.lifetime.end.p0(i64 4, ptr %6) #2
  call void @llvm.lifetime.end.p0(i64 8, ptr %5) #2
  ret i32 %30
}

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 = !{!"any pointer", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C++ TBAA"}
!9 = !{!10, !10, i64 0}
!10 = !{!"int", !7, i64 0}
!11 = !{!7, !7, i64 0}
!12 = distinct !{!12, !13}
!13 = !{!"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(read, inaccessiblemem: none) uwtable
define dso_local noundef i32 @_Z22countTrailingNullBytesPKhi(ptr nocapture noundef readonly %0, i32 noundef %1) local_unnamed_addr #0 {
  %3 = icmp sgt i32 %1, 0
  br i1 %3, label %.lr.ph.preheader, label %.critedge

.lr.ph.preheader:                                 ; preds = %2
  %4 = zext nneg i32 %1 to i64
  %5 = getelementptr inbounds i8, ptr %0, i64 %4
  br label %.lr.ph

.lr.ph:                                           ; preds = %.lr.ph.preheader, %8
  %.0712.pn = phi ptr [ %.0712, %8 ], [ %5, %.lr.ph.preheader ]
  %.011 = phi i32 [ %9, %8 ], [ 0, %.lr.ph.preheader ]
  %.0712 = getelementptr inbounds i8, ptr %.0712.pn, i64 -1
  %6 = load i8, ptr %.0712, align 1, !tbaa !5
  %7 = icmp eq i8 %6, 0
  br i1 %7, label %8, label %.critedge

8:                                                ; preds = %.lr.ph
  %9 = add nuw nsw i32 %.011, 1
  %exitcond.not = icmp eq i32 %9, %1
  br i1 %exitcond.not, label %.critedge, label %.lr.ph, !llvm.loop !8

.critedge:                                        ; preds = %.lr.ph, %8, %2
  %.0.lcssa = phi i32 [ 0, %2 ], [ %1, %8 ], [ %.011, %.lr.ph ]
  ret i32 %.0.lcssa
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn memory(read, 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"}


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