inline iter in repr/primitive.rs

[Fuuzetsu]

We have a piece of simple code that looks a bit like this:

   let action = self.iter().next()?;
   self.0.remove(action);
   Some(action)

where self.iter() just defers to EnumSet::iter().

Looking at the asm with cargo asm, I see something like below. There's a non-inlined call to iter. After adding #[inline] in enumset, you can see at the bottom snipped that the call disappears and assembly ends up being much better.

.section .text.trader::policy::ToDoList::pop,"ax",@progbits
        .globl  trader::policy::ToDoList::pop
        .p2align        4, 0x90
        .type   trader::policy::ToDoList::pop,@function
trader::policy::ToDoList::pop:

                // /home/shana/programming/engine/trader/src/policy.rs : 309
                pub fn pop(&mut self) -> Option<TraderAction> {
        .cfi_startproc
        push rbp
        .cfi_def_cfa_offset 16
        push rbx
        .cfi_def_cfa_offset 24
        push rax
        .cfi_def_cfa_offset 32
        .cfi_offset rbx, -24
        .cfi_offset rbp, -16
        mov rbx, rdi

                // /home/shana/programming/engine/trader/src/policy.rs : 329
                self.0.iter()
        mov ebp, dword ptr [rdi]

                // /home/shana/.cargo/registry/src/index.crates.io-6f17d22bba15001f/enumset-1.1.2/src/set.rs : 760
                EnumSetIter { iter: set.__priv_repr.iter() }
        mov edi, ebp

        call qword ptr [rip + enumset::repr::primitive::_::<impl enumset::repr::EnumSetTypeRepr for u32>::iter@GOTPCREL]
        mov ecx, eax
        mov al, 21

                // /home/shana/.cargo/registry/src/index.crates.io-6f17d22bba15001f/enumset-1.1.2/src/repr/primitive.rs : 20
                *self == 0
        test ecx, ecx

                // /home/shana/.cargo/registry/src/index.crates.io-6f17d22bba15001f/enumset-1.1.2/src/repr/primitive.rs : 275
                if self.0.is_empty() {
        je .LBB4674_4

                // /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/num/mod.rs : 1143
                uint_impl! {
        rep bsf ecx, ecx

                // /home/shana/programming/engine/trader/src/action.rs : 36
                enumset::EnumSetType,
        cmp ecx, 21
        jb .LBB4674_3

        cmp cl, 21
        jne .LBB4674_3

.LBB4674_4:
                // /home/shana/programming/engine/trader/src/policy.rs : 313
                }
        add rsp, 8
        .cfi_def_cfa_offset 24
        pop rbx

        .cfi_def_cfa_offset 16
        pop rbp
        .cfi_def_cfa_offset 8
        ret

.LBB4674_3:
        .cfi_def_cfa_offset 32
                // /home/shana/.cargo/registry/src/index.crates.io-6f17d22bba15001f/enumset-1.1.2/src/repr/primitive.rs : 29
                *self &= !(1 << bit as $name);
        btr ebp, ecx
        mov dword ptr [rbx], ebp
        mov eax, ecx

                // /home/shana/programming/engine/trader/src/policy.rs : 313
                }
        add rsp, 8
        .cfi_def_cfa_offset 24
        pop rbx

        .cfi_def_cfa_offset 16
        pop rbp
        .cfi_def_cfa_offset 8
        ret

.section .text.trader::policy::ToDoList::pop,"ax",@progbits
        .globl  trader::policy::ToDoList::pop
        .p2align        4, 0x90
        .type   trader::policy::ToDoList::pop,@function
trader::policy::ToDoList::pop:

        .cfi_startproc
                // /home/shana/programming/engine/trader/src/policy.rs : 329
                self.0.iter()
        mov ecx, dword ptr [rdi]
        mov al, 21

                // /tmp/enumset/enumset/src/repr/primitive.rs : 20
                *self == 0
        test ecx, ecx

                // /tmp/enumset/enumset/src/repr/primitive.rs : 276
                if self.0.is_empty() {
        je .LBB4674_4

                // /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/num/uint_macros.rs : 170
                intrinsics::cttz(self) as u32
        rep bsf edx, ecx

                // /home/shana/programming/engine/trader/src/action.rs : 36
                enumset::EnumSetType,
        cmp edx, 21
        jb .LBB4674_3

        cmp dl, 21
        jne .LBB4674_3

.LBB4674_4:
                // /home/shana/programming/engine/trader/src/policy.rs : 313
                }
        ret

.LBB4674_3:
                // /tmp/enumset/enumset/src/repr/primitive.rs : 29
                *self &= !(1 << bit as $name);
        btr ecx, edx
        mov dword ptr [rdi], ecx
        mov eax, edx

                // /home/shana/programming/engine/trader/src/policy.rs : 313
                }
        ret