67 lines
2.3 KiB
Rust
67 lines
2.3 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A pass that simplifies branches when their condition is known.
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use rustc::ty::TyCtxt;
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use rustc::middle::const_val::ConstVal;
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use rustc::mir::transform::{MirPass, MirSource, Pass};
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use rustc::mir::repr::*;
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use std::fmt;
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pub struct SimplifyBranches<'a> { label: &'a str }
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impl<'a> SimplifyBranches<'a> {
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pub fn new(label: &'a str) -> Self {
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SimplifyBranches { label: label }
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}
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}
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impl<'l, 'tcx> MirPass<'tcx> for SimplifyBranches<'l> {
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fn run_pass<'a>(&mut self, _tcx: TyCtxt<'a, 'tcx, 'tcx>, _src: MirSource, mir: &mut Mir<'tcx>) {
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for block in mir.basic_blocks_mut() {
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let terminator = block.terminator_mut();
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terminator.kind = match terminator.kind {
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TerminatorKind::If { ref targets, cond: Operand::Constant(Constant {
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literal: Literal::Value {
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value: ConstVal::Bool(cond)
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}, ..
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}) } => {
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if cond {
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TerminatorKind::Goto { target: targets.0 }
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} else {
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TerminatorKind::Goto { target: targets.1 }
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}
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}
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TerminatorKind::Assert { target, cond: Operand::Constant(Constant {
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literal: Literal::Value {
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value: ConstVal::Bool(cond)
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}, ..
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}), expected, .. } if cond == expected => {
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TerminatorKind::Goto { target: target }
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}
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_ => continue
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};
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}
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}
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}
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impl<'l> Pass for SimplifyBranches<'l> {
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fn disambiguator<'a>(&'a self) -> Option<Box<fmt::Display+'a>> {
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Some(Box::new(self.label))
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}
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// avoid calling `type_name` - it contains `<'static>`
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fn name(&self) -> &str { "SimplifyBranches" }
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}
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