; LLVM IR from sbshah97/DS-Algo-Handbook :: Data-Structures/Linked_List/Doubly_Linked_List (doubly)

; 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"

%struct.node = type { i32, i32, ptr, ptr }

@head = external dso_local global ptr, align 8
@last = external dso_local global ptr, align 8

; 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: nounwind uwtable
define dso_local ptr @deleteLast() #1 {
  %1 = alloca ptr, align 8
  call void @llvm.lifetime.start.p0(i64 8, ptr %1) #2
  %2 = load ptr, ptr @last, align 8, !tbaa !5
  store ptr %2, ptr %1, align 8, !tbaa !5
  %3 = load ptr, ptr @head, align 8, !tbaa !5
  %4 = getelementptr inbounds %struct.node, ptr %3, i32 0, i32 2
  %5 = load ptr, ptr %4, align 8, !tbaa !9
  %6 = icmp eq ptr %5, null
  br i1 %6, label %7, label %8

7:                                                ; preds = %0
  store ptr null, ptr @head, align 8, !tbaa !5
  br label %13

8:                                                ; preds = %0
  %9 = load ptr, ptr @last, align 8, !tbaa !5
  %10 = getelementptr inbounds %struct.node, ptr %9, i32 0, i32 3
  %11 = load ptr, ptr %10, align 8, !tbaa !12
  %12 = getelementptr inbounds %struct.node, ptr %11, i32 0, i32 2
  store ptr null, ptr %12, align 8, !tbaa !9
  br label %13

13:                                               ; preds = %8, %7
  %14 = load ptr, ptr @last, align 8, !tbaa !5
  %15 = getelementptr inbounds %struct.node, ptr %14, i32 0, i32 3
  %16 = load ptr, ptr %15, align 8, !tbaa !12
  store ptr %16, ptr @last, align 8, !tbaa !5
  %17 = load ptr, ptr %1, align 8, !tbaa !5
  call void @llvm.lifetime.end.p0(i64 8, ptr %1) #2
  ret ptr %17
}

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #1 = { 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/C++ TBAA"}
!9 = !{!10, !6, i64 8}
!10 = !{!"node", !11, i64 0, !11, i64 4, !6, i64 8, !6, i64 16}
!11 = !{!"int", !7, i64 0}
!12 = !{!10, !6, i64 16}


; 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"

@head = external dso_local local_unnamed_addr global ptr, align 8
@last = external dso_local local_unnamed_addr global ptr, align 8

; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(readwrite, inaccessiblemem: none) uwtable
define dso_local ptr @deleteLast() local_unnamed_addr #0 {
  %1 = load ptr, ptr @last, align 8, !tbaa !5
  %2 = load ptr, ptr @head, align 8, !tbaa !5
  %3 = getelementptr inbounds i8, ptr %2, i64 8
  %4 = load ptr, ptr %3, align 8, !tbaa !9
  %5 = icmp eq ptr %4, null
  br i1 %5, label %6, label %7

6:                                                ; preds = %0
  store ptr null, ptr @head, align 8, !tbaa !5
  %.phi.trans.insert = getelementptr inbounds i8, ptr %1, i64 16
  %.pre = load ptr, ptr %.phi.trans.insert, align 8, !tbaa !12
  br label %11

7:                                                ; preds = %0
  %8 = getelementptr inbounds i8, ptr %1, i64 16
  %9 = load ptr, ptr %8, align 8, !tbaa !12
  %10 = getelementptr inbounds i8, ptr %9, i64 8
  store ptr null, ptr %10, align 8, !tbaa !9
  br label %11

11:                                               ; preds = %7, %6
  %12 = phi ptr [ %9, %7 ], [ %.pre, %6 ]
  store ptr %12, ptr @last, align 8, !tbaa !5
  ret ptr %1
}

attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn 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 = !{!"any pointer", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}
!9 = !{!10, !6, i64 8}
!10 = !{!"node", !11, i64 0, !11, i64 4, !6, i64 8, !6, i64 16}
!11 = !{!"int", !7, i64 0}
!12 = !{!10, !6, i64 16}


; Effective O3 passes: BDCEPass,EarlyCSEPass,GVNPass,GlobalOptPass,InferFunctionAttrsPass,InstCombinePass,PostOrderFunctionAttrsPass,SROAPass