diff options
| -rw-r--r-- | src/libcore/intrinsics.rs | 14 | ||||
| -rw-r--r-- | src/librustc_trans/intrinsic.rs | 8 | ||||
| -rw-r--r-- | src/librustc_typeck/check/intrinsic.rs | 2 | ||||
| -rw-r--r-- | src/test/codegen/likely.rs | 41 |
4 files changed, 65 insertions, 0 deletions
diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs index 06b506ab014..22abe7a99b1 100644 --- a/src/libcore/intrinsics.rs +++ b/src/libcore/intrinsics.rs @@ -194,6 +194,20 @@ extern "rust-intrinsic" { /// own, or if it does not enable any significant optimizations. pub fn assume(b: bool); + #[cfg(not(stage0))] + /// Hints to the compiler that branch condition is likely to be true. + /// Returns the value passed to it. + /// + /// Any use other than with `if` statements will probably not have an effect. + pub fn likely(b: bool) -> bool; + + #[cfg(not(stage0))] + /// Hints to the compiler that branch condition is likely to be false. + /// Returns the value passed to it. + /// + /// Any use other than with `if` statements will probably not have an effect. + pub fn unlikely(b: bool) -> bool; + /// Executes a breakpoint trap, for inspection by a debugger. pub fn breakpoint(); diff --git a/src/librustc_trans/intrinsic.rs b/src/librustc_trans/intrinsic.rs index 2049696ee4f..694db035e28 100644 --- a/src/librustc_trans/intrinsic.rs +++ b/src/librustc_trans/intrinsic.rs @@ -136,6 +136,14 @@ pub fn trans_intrinsic_call<'a, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>, (Some(llfn), _) => { Call(bcx, llfn, &llargs, call_debug_location) } + (_, "likely") => { + let expect = ccx.get_intrinsic(&("llvm.expect.i1")); + Call(bcx, expect, &[llargs[0], C_bool(ccx, true)], call_debug_location) + } + (_, "unlikely") => { + let expect = ccx.get_intrinsic(&("llvm.expect.i1")); + Call(bcx, expect, &[llargs[0], C_bool(ccx, false)], call_debug_location) + } (_, "try") => { bcx = try_intrinsic(bcx, llargs[0], llargs[1], llargs[2], llresult, call_debug_location); diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs index eb87c230b74..563b645910e 100644 --- a/src/librustc_typeck/check/intrinsic.rs +++ b/src/librustc_typeck/check/intrinsic.rs @@ -285,6 +285,8 @@ pub fn check_intrinsic_type(ccx: &CrateCtxt, it: &hir::ForeignItem) { (1, vec![param(ccx, 0), param(ccx, 0)], param(ccx, 0)), "assume" => (0, vec![tcx.types.bool], tcx.mk_nil()), + "likely" => (0, vec![tcx.types.bool], tcx.types.bool), + "unlikely" => (0, vec![tcx.types.bool], tcx.types.bool), "discriminant_value" => (1, vec![ tcx.mk_imm_ref(tcx.mk_region(ty::ReLateBound(ty::DebruijnIndex::new(1), diff --git a/src/test/codegen/likely.rs b/src/test/codegen/likely.rs new file mode 100644 index 00000000000..acaec0350bf --- /dev/null +++ b/src/test/codegen/likely.rs @@ -0,0 +1,41 @@ +// Copyright 2016 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. + +// compile-flags: -C no-prepopulate-passes + +#![crate_type = "lib"] +#![feature(core_intrinsics)] + +use std::intrinsics::{likely,unlikely}; + +#[no_mangle] +pub fn check_likely(x: i32, y: i32) -> Option<i32> { + unsafe { + // CHECK: call i1 @llvm.expect.i1(i1 %{{.*}}, i1 true) + if likely(x == y) { + None + } else { + Some(x + y) + } + } +} + +#[no_mangle] +pub fn check_unlikely(x: i32, y: i32) -> Option<i32> { + unsafe { + // CHECK: call i1 @llvm.expect.i1(i1 %{{.*}}, i1 false) + if unlikely(x == y) { + None + } else { + Some(x + y) + } + } +} + |