chain-more-codegen.ll

; ModuleID = 'chain_more_codegen.cgu-0.rs'
source_filename = "chain_more_codegen.cgu-0.rs"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%"8.unwind::libunwind::_Unwind_Exception" = type { i64, void (i32, %"8.unwind::libunwind::_Unwind_Exception"*)*, [6 x i64] }
%"8.unwind::libunwind::_Unwind_Context" = type {}

; Function Attrs: uwtable
define i64 @range_chain_default_fold(i64, i64, i64 (i64, i64)* nocapture) unnamed_addr #0 personality i32 (i32, i32, i64, %"8.unwind::libunwind::_Unwind_Exception"*, %"8.unwind::libunwind::_Unwind_Context"*)* @rust_eh_personality {
entry-block:
  br label %bb6.i

bb6.i:                                            ; preds = %bb11.i, %entry-block
  %iter.sroa.9.0.i = phi i64 [ 0, %entry-block ], [ %iter.sroa.9.3.ph.i, %bb11.i ]
  %iter.sroa.15.0.i = phi i8 [ 0, %entry-block ], [ %iter.sroa.15.1.ph.i, %bb11.i ]
  %iter.sroa.0.0.i = phi i64 [ 0, %entry-block ], [ %iter.sroa.0.2.ph.i, %bb11.i ]
  %accum.0.i = phi i64 [ 0, %entry-block ], [ %11, %bb11.i ]
  %trunc.i.i = trunc i8 %iter.sroa.15.0.i to i2
  switch i2 %trunc.i.i, label %unreachable.i.i [
    i2 0, label %bb1.i.i
    i2 1, label %bb2.i.i
    i2 -2, label %bb3.i.i
  ]

bb1.i.i:                                          ; preds = %bb6.i
  %3 = icmp ult i64 %iter.sroa.0.0.i, %0
  br i1 %3, label %bb9.i.i, label %bb8.i.i

bb2.i.i:                                          ; preds = %bb6.i
  %4 = icmp ult i64 %iter.sroa.0.0.i, %0
  br i1 %4, label %bb2.i21.i.i, label %_ZN4core4iter8iterator8Iterator4fold17h2dd9e388c2016361E.exit

bb2.i21.i.i:                                      ; preds = %bb2.i.i
  %5 = add i64 %iter.sroa.0.0.i, 1
  br label %bb11.i

bb3.i.i:                                          ; preds = %bb6.i
  %6 = icmp ult i64 %iter.sroa.9.0.i, %1
  br i1 %6, label %bb2.i16.i.i, label %_ZN4core4iter8iterator8Iterator4fold17h2dd9e388c2016361E.exit

bb2.i16.i.i:                                      ; preds = %bb3.i.i
  %7 = add i64 %iter.sroa.9.0.i, 1
  br label %bb11.i

bb8.i.i:                                          ; preds = %bb1.i.i
  %8 = icmp ult i64 %iter.sroa.9.0.i, %1
  br i1 %8, label %bb2.i11.i.i, label %_ZN4core4iter8iterator8Iterator4fold17h2dd9e388c2016361E.exit

bb2.i11.i.i:                                      ; preds = %bb8.i.i
  %9 = add i64 %iter.sroa.9.0.i, 1
  br label %bb11.i

bb9.i.i:                                          ; preds = %bb1.i.i
  %10 = add i64 %iter.sroa.0.0.i, 1
  br label %bb11.i

unreachable.i.i:                                  ; preds = %bb6.i
  unreachable

bb11.i:                                           ; preds = %bb9.i.i, %bb2.i11.i.i, %bb2.i16.i.i, %bb2.i21.i.i
  %iter.sroa.9.3.ph.i = phi i64 [ %9, %bb2.i11.i.i ], [ %7, %bb2.i16.i.i ], [ %iter.sroa.9.0.i, %bb2.i21.i.i ], [ %iter.sroa.9.0.i, %bb9.i.i ]
  %iter.sroa.15.1.ph.i = phi i8 [ 2, %bb2.i11.i.i ], [ %iter.sroa.15.0.i, %bb2.i16.i.i ], [ %iter.sroa.15.0.i, %bb2.i21.i.i ], [ %iter.sroa.15.0.i, %bb9.i.i ]
  %iter.sroa.0.2.ph.i = phi i64 [ %iter.sroa.0.0.i, %bb2.i11.i.i ], [ %iter.sroa.0.0.i, %bb2.i16.i.i ], [ %5, %bb2.i21.i.i ], [ %10, %bb9.i.i ]
  %_15.sroa.8.4.ph.i = phi i64 [ %iter.sroa.9.0.i, %bb2.i11.i.i ], [ %iter.sroa.9.0.i, %bb2.i16.i.i ], [ %iter.sroa.0.0.i, %bb2.i21.i.i ], [ %iter.sroa.0.0.i, %bb9.i.i ]
  %11 = tail call i64 %2(i64 %accum.0.i, i64 %_15.sroa.8.4.ph.i), !noalias !0
  br label %bb6.i

_ZN4core4iter8iterator8Iterator4fold17h2dd9e388c2016361E.exit: ; preds = %bb2.i.i, %bb3.i.i, %bb8.i.i
  ret i64 %accum.0.i
}

; Function Attrs: uwtable
define i64 @range_chain_custom_fold(i64, i64, i64 (i64, i64)* nocapture) unnamed_addr #0 personality i32 (i32, i32, i64, %"8.unwind::libunwind::_Unwind_Exception"*, %"8.unwind::libunwind::_Unwind_Context"*)* @rust_eh_personality {
bb5.i:
  %3 = icmp eq i64 %0, 0
  br i1 %3, label %bb8.i, label %bb11.i.i.preheader

bb11.i.i.preheader:                               ; preds = %bb5.i
  br label %bb11.i.i

bb11.i.i:                                         ; preds = %bb11.i.i.preheader, %bb11.i.i
  %accum.012.i.i = phi i64 [ %5, %bb11.i.i ], [ 0, %bb11.i.i.preheader ]
  %iter.sroa.0.011.i.i = phi i64 [ %4, %bb11.i.i ], [ 0, %bb11.i.i.preheader ]
  %4 = add nuw i64 %iter.sroa.0.011.i.i, 1
  %5 = tail call i64 %2(i64 %accum.012.i.i, i64 %iter.sroa.0.011.i.i), !noalias !3
  %exitcond.i.i = icmp eq i64 %4, %0
  br i1 %exitcond.i.i, label %bb8.i.loopexit, label %bb11.i.i

bb8.i.loopexit:                                   ; preds = %bb11.i.i
  br label %bb8.i

bb8.i:                                            ; preds = %bb8.i.loopexit, %bb5.i
  %accum.0.i = phi i64 [ 0, %bb5.i ], [ %5, %bb8.i.loopexit ]
  %6 = icmp eq i64 %1, 0
  br i1 %6, label %_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit, label %bb11.i7.i.preheader

bb11.i7.i.preheader:                              ; preds = %bb8.i
  br label %bb11.i7.i

bb11.i7.i:                                        ; preds = %bb11.i7.i.preheader, %bb11.i7.i
  %accum.012.i3.i = phi i64 [ %8, %bb11.i7.i ], [ %accum.0.i, %bb11.i7.i.preheader ]
  %iter.sroa.0.011.i4.i = phi i64 [ %7, %bb11.i7.i ], [ 0, %bb11.i7.i.preheader ]
  %7 = add nuw i64 %iter.sroa.0.011.i4.i, 1
  %8 = tail call i64 %2(i64 %accum.012.i3.i, i64 %iter.sroa.0.011.i4.i), !noalias !3
  %exitcond.i6.i = icmp eq i64 %7, %1
  br i1 %exitcond.i6.i, label %_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit.loopexit, label %bb11.i7.i

_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit.loopexit: ; preds = %bb11.i7.i
  br label %_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit

_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit: ; preds = %_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit.loopexit, %bb8.i
  %accum.1.i = phi i64 [ %accum.0.i, %bb8.i ], [ %8, %_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E.exit.loopexit ]
  ret i64 %accum.1.i
}

; Function Attrs: nounwind
declare i32 @rust_eh_personality(i32, i32, i64, %"8.unwind::libunwind::_Unwind_Exception"*, %"8.unwind::libunwind::_Unwind_Context"*) unnamed_addr #1

attributes #0 = { uwtable }
attributes #1 = { nounwind }

!0 = !{!1}
!1 = distinct !{!1, !2, !"_ZN4core4iter8iterator8Iterator4fold17h2dd9e388c2016361E: argument 0"}
!2 = distinct !{!2, !"_ZN4core4iter8iterator8Iterator4fold17h2dd9e388c2016361E"}
!3 = !{!4}
!4 = distinct !{!4, !5, !"_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E: argument 0"}
!5 = distinct !{!5, !"_ZN18chain_more_codegen4fold17h9ac2aaed4568fdf9E"}

chain-more-codegen.rs

#![crate_type="lib"]


#[no_mangle]
pub fn range_chain_default_fold(xs: usize, ys: usize, f: fn(usize, usize) -> usize) -> usize {
    chain(0..xs, 0..ys).fold(0, f)
}

#[no_mangle]
pub fn range_chain_custom_fold(xs: usize, ys: usize, f: fn(usize, usize) -> usize) -> usize {
    fold(chain(0..xs, 0..ys), 0, f)
}

pub struct Chain<A, B> {
    a: A,
    b: B,
    state: ChainState,
}

fn chain<A, B>(a: A, b: B) -> Chain<A::IntoIter, B::IntoIter>
    where A: IntoIterator, B: IntoIterator<Item=A::Item>,
{
    Chain {
        a: a.into_iter(),
        b: b.into_iter(),
        state: ChainState::Both,
    }
}

// The iterator protocol specifies that iteration ends with the return value
// `None` from `.next()` (or `.next_back()`) and it is unspecified what
// further calls return. The chain adaptor must account for this since it uses
// two subiterators.
//
//  It uses three states:
//
//  - Both: `a` and `b` are remaining
//  - Front: `a` remaining
//  - Back: `b` remaining
//
//  The fourth state (neither iterator is remaining) only occurs after Chain has
//  returned None once, so we don't need to store this state.
enum ChainState {
    // both front and back iterator are remaining
    Both,
    // only front is remaining
    Front,
    // only back is remaining
    Back,
}

impl<A, B> Iterator for Chain<A, B> where
    A: Iterator,
    B: Iterator<Item = A::Item>
{
    type Item = A::Item;

    #[inline]
    fn next(&mut self) -> Option<A::Item> {
        match self.state {
            ChainState::Both => match self.a.next() {
                elt @ Some(..) => elt,
                None => {
                    self.state = ChainState::Back;
                    self.b.next()
                }
            },
            ChainState::Front => self.a.next(),
            ChainState::Back => self.b.next(),
        }
    }
}

fn fold<A, B, Acc, F>(self_: Chain<A, B>, init: Acc, mut f: F) -> Acc
    where F: FnMut(Acc, A::Item) -> Acc,
          A: Iterator,
          B: Iterator<Item=A::Item>,
{
    let mut accum = init;
    match self_.state {
        ChainState::Both | ChainState::Front => {
            accum = self_.a.fold(accum, &mut f);
        }
        _ => { }
    }
    match self_.state {
        ChainState::Both | ChainState::Back => {
            accum = self_.b.fold(accum, &mut f);
        }
        _ => { }
    }
    accum
}