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Auto merge of #38332 - bluss:copy-prop-arguments, r=eddyb

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Allow copy-propagation of function arguments

Allow propagating function argument locals in copy propagation.
This commit is contained in:
bors 2016-12-14 06:26:21 +00:00
commit 5d3ec6b0a0
2 changed files with 40 additions and 4 deletions
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10
src/librustc_mir/transform/copy_prop.rs
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@ -30,7 +30,7 @@
//! future.
use def_use::DefUseAnalysis;
use rustc::mir::{Constant, Local, Location, Lvalue, Mir, Operand, Rvalue, StatementKind};
use rustc::mir::{Constant, Local, LocalKind, Location, Lvalue, Mir, Operand, Rvalue, StatementKind};
use rustc::mir::transform::{MirPass, MirSource, Pass};
use rustc::mir::visit::MutVisitor;
use rustc::ty::TyCtxt;
@ -122,7 +122,7 @@ impl<'tcx> MirPass<'tcx> for CopyPropagation {
local == dest_local => {
let maybe_action = match *operand {
Operand::Consume(ref src_lvalue) => {
Action::local_copy(&def_use_analysis, src_lvalue)
Action::local_copy(&mir, &def_use_analysis, src_lvalue)
}
Operand::Constant(ref src_constant) => {
Action::constant(src_constant)
@ -159,7 +159,7 @@ enum Action<'tcx> {
}
impl<'tcx> Action<'tcx> {
fn local_copy(def_use_analysis: &DefUseAnalysis, src_lvalue: &Lvalue<'tcx>)
fn local_copy(mir: &Mir<'tcx>, def_use_analysis: &DefUseAnalysis, src_lvalue: &Lvalue<'tcx>)
-> Option<Action<'tcx>> {
// The source must be a local.
let src_local = if let Lvalue::Local(local) = *src_lvalue {
@ -195,7 +195,9 @@ impl<'tcx> Action<'tcx> {
// SRC = X;
// USE(SRC);
let src_def_count = src_use_info.def_count_not_including_drop();
if src_def_count != 1 {
// allow function arguments to be propagated
if src_def_count > 1 ||
(src_def_count == 0 && mir.local_kind(src_local) != LocalKind::Arg) {
debug!(" Can't copy-propagate local: {} defs of src",
src_use_info.def_count_not_including_drop());
return None

34
src/test/mir-opt/copy_propagation.rs Normal file
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@ -0,0 +1,34 @@
// 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.
fn test(x: u32) -> u32 {
let y = x;
y
}
fn main() { }
// END RUST SOURCE
// START rustc.node4.CopyPropagation.before.mir
// bb0: {
// _2 = _1;
// _4 = _2;
// _3 = _4;
// _5 = _3;
// _0 = _5;
// return;
// }
// END rustc.node4.CopyPropagation.before.mir
// START rustc.node4.CopyPropagation.after.mir
// bb0: {
// _0 = _1;
// return;
// }
// END rustc.node4.CopyPropagation.after.mir