; LLVM IR from AllenDowney/ExercisesInC :: examples (palindrome)

; 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: nounwind willreturn memory(read)
declare i64 @strlen(ptr noundef) #1

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

9:                                                ; preds = %40, %1
  %10 = load ptr, ptr %2, align 8, !tbaa !5
  %11 = load ptr, ptr %3, align 8, !tbaa !5
  %12 = icmp ult ptr %10, %11
  br i1 %12, label %13, label %45

13:                                               ; preds = %9
  br label %14

14:                                               ; preds = %13
  %15 = load ptr, ptr %3, align 8, !tbaa !5
  %16 = load i8, ptr %15, align 1, !tbaa !9
  %17 = sext i8 %16 to i32
  %18 = load ptr, ptr %2, align 8, !tbaa !5
  %19 = load i8, ptr %18, align 1, !tbaa !9
  %20 = sext i8 %19 to i32
  %21 = xor i32 %20, %17
  %22 = trunc i32 %21 to i8
  store i8 %22, ptr %18, align 1, !tbaa !9
  %23 = load ptr, ptr %2, align 8, !tbaa !5
  %24 = load i8, ptr %23, align 1, !tbaa !9
  %25 = sext i8 %24 to i32
  %26 = load ptr, ptr %3, align 8, !tbaa !5
  %27 = load i8, ptr %26, align 1, !tbaa !9
  %28 = sext i8 %27 to i32
  %29 = xor i32 %28, %25
  %30 = trunc i32 %29 to i8
  store i8 %30, ptr %26, align 1, !tbaa !9
  %31 = load ptr, ptr %3, align 8, !tbaa !5
  %32 = load i8, ptr %31, align 1, !tbaa !9
  %33 = sext i8 %32 to i32
  %34 = load ptr, ptr %2, align 8, !tbaa !5
  %35 = load i8, ptr %34, align 1, !tbaa !9
  %36 = sext i8 %35 to i32
  %37 = xor i32 %36, %33
  %38 = trunc i32 %37 to i8
  store i8 %38, ptr %34, align 1, !tbaa !9
  br label %39

39:                                               ; preds = %14
  br label %40

40:                                               ; preds = %39
  %41 = load ptr, ptr %2, align 8, !tbaa !5
  %42 = getelementptr inbounds i8, ptr %41, i32 1
  store ptr %42, ptr %2, align 8, !tbaa !5
  %43 = load ptr, ptr %3, align 8, !tbaa !5
  %44 = getelementptr inbounds i8, ptr %43, i32 -1
  store ptr %44, ptr %3, align 8, !tbaa !5
  br label %9, !llvm.loop !10

45:                                               ; preds = %9
  call void @llvm.lifetime.end.p0(i64 8, ptr %3) #3
  ret void
}

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #1 = { nounwind willreturn memory(read) "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 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 #3 = { nounwind }
attributes #4 = { nounwind willreturn memory(read) }

!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 = !{!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 nounwind willreturn memory(argmem: read)
declare i64 @strlen(ptr nocapture noundef) local_unnamed_addr #0

; Function Attrs: nofree nounwind memory(readwrite, inaccessiblemem: none) uwtable
define dso_local void @inplace_reverse(ptr noundef %0) local_unnamed_addr #1 {
  %2 = tail call i64 @strlen(ptr noundef nonnull dereferenceable(1) %0) #2
  %3 = getelementptr inbounds i8, ptr %0, i64 %2
  %.013 = getelementptr inbounds i8, ptr %3, i64 -1
  %4 = icmp ugt ptr %.013, %0
  br i1 %4, label %.lr.ph, label %._crit_edge

.lr.ph:                                           ; preds = %1, %.lr.ph
  %.015 = phi ptr [ %.0, %.lr.ph ], [ %.013, %1 ]
  %.01214 = phi ptr [ %12, %.lr.ph ], [ %0, %1 ]
  %5 = load i8, ptr %.015, align 1, !tbaa !5
  %6 = load i8, ptr %.01214, align 1, !tbaa !5
  %7 = xor i8 %6, %5
  store i8 %7, ptr %.01214, align 1, !tbaa !5
  %8 = load i8, ptr %.015, align 1, !tbaa !5
  %9 = xor i8 %8, %7
  store i8 %9, ptr %.015, align 1, !tbaa !5
  %10 = load i8, ptr %.01214, align 1, !tbaa !5
  %11 = xor i8 %10, %9
  store i8 %11, ptr %.01214, align 1, !tbaa !5
  %12 = getelementptr inbounds i8, ptr %.01214, i64 1
  %.0 = getelementptr inbounds i8, ptr %.015, i64 -1
  %13 = icmp ult ptr %12, %.0
  br i1 %13, label %.lr.ph, label %._crit_edge, !llvm.loop !8

._crit_edge:                                      ; preds = %.lr.ph, %1
  ret void
}

attributes #0 = { mustprogress nofree nounwind willreturn memory(argmem: read) "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 = { nofree nounwind 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" }
attributes #2 = { nounwind willreturn memory(read) }

!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/C++ TBAA"}
!8 = distinct !{!8, !9}
!9 = !{!"llvm.loop.mustprogress"}


; Effective O3 passes: EarlyCSEPass,GlobalOptPass,InferFunctionAttrsPass,InstCombinePass,JumpThreadingPass,LoopRotatePass,LoopSimplifyPass,LoopUnrollPass,PostOrderFunctionAttrsPass,SROAPass,SimplifyCFGPass,TailCallElimPass