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refactor simplify_cfg and split off simplify_branches
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// 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. | ||
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//! A pass that simplifies branches when their condition is known. | ||
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use rustc::ty::TyCtxt; | ||
use rustc::middle::const_val::ConstVal; | ||
use rustc::mir::transform::{MirPass, MirSource, Pass}; | ||
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> { | ||
pub fn new(label: &'a str) -> Self { | ||
SimplifyBranches { label: label } | ||
} | ||
} | ||
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impl<'l, 'tcx> MirPass<'tcx> for SimplifyBranches<'l> { | ||
fn run_pass<'a>(&mut self, _tcx: TyCtxt<'a, 'tcx, 'tcx>, _src: MirSource, mir: &mut Mir<'tcx>) { | ||
for block in mir.basic_blocks_mut() { | ||
let terminator = block.terminator_mut(); | ||
terminator.kind = match terminator.kind { | ||
TerminatorKind::If { ref targets, cond: Operand::Constant(Constant { | ||
literal: Literal::Value { | ||
value: ConstVal::Bool(cond) | ||
}, .. | ||
}) } => { | ||
if cond { | ||
TerminatorKind::Goto { target: targets.0 } | ||
} else { | ||
TerminatorKind::Goto { target: targets.1 } | ||
} | ||
} | ||
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TerminatorKind::Assert { target, cond: Operand::Constant(Constant { | ||
literal: Literal::Value { | ||
value: ConstVal::Bool(cond) | ||
}, .. | ||
}), expected, .. } if cond == expected => { | ||
TerminatorKind::Goto { target: target } | ||
} | ||
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_ => continue | ||
}; | ||
} | ||
} | ||
} | ||
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impl<'l> Pass for SimplifyBranches<'l> { | ||
fn name(&self) -> &str { "simplify-branches" } | ||
fn disambiguator<'a>(&'a self) -> Option<Box<fmt::Display+'a>> { | ||
Some(Box::new(self.label)) | ||
} | ||
} |
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