Florian Zeitz d721c1f9e3 trans: Reorder basic blocks in slice_for_each
This is mainly for readability of the generated LLVM IR and subsequently
assembly. There is a slight positive performance impact, likely due to
I-cache effects.
2017-07-26 16:23:07 +02:00

54 lines
1.8 KiB
Rust

// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use llvm;
use builder::Builder;
use llvm::{BasicBlockRef, ValueRef};
use common::*;
use rustc::ty::Ty;
pub fn slice_for_each<'a, 'tcx, F>(
bcx: &Builder<'a, 'tcx>,
data_ptr: ValueRef,
unit_ty: Ty<'tcx>,
len: ValueRef,
f: F
) -> Builder<'a, 'tcx> where F: FnOnce(&Builder<'a, 'tcx>, ValueRef, BasicBlockRef) {
// Special-case vectors with elements of size 0 so they don't go out of bounds (#9890)
let zst = type_is_zero_size(bcx.ccx, unit_ty);
let add = |bcx: &Builder, a, b| if zst {
bcx.add(a, b)
} else {
bcx.inbounds_gep(a, &[b])
};
let body_bcx = bcx.build_sibling_block("slice_loop_body");
let header_bcx = bcx.build_sibling_block("slice_loop_header");
let next_bcx = bcx.build_sibling_block("slice_loop_next");
let start = if zst {
C_uint(bcx.ccx, 0usize)
} else {
data_ptr
};
let end = add(&bcx, start, len);
bcx.br(header_bcx.llbb());
let current = header_bcx.phi(val_ty(start), &[start], &[bcx.llbb()]);
let keep_going = header_bcx.icmp(llvm::IntNE, current, end);
header_bcx.cond_br(keep_going, body_bcx.llbb(), next_bcx.llbb());
let next = add(&body_bcx, current, C_uint(bcx.ccx, 1usize));
f(&body_bcx, if zst { data_ptr } else { current }, header_bcx.llbb());
header_bcx.add_incoming_to_phi(current, next, body_bcx.llbb());
next_bcx
}