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use rustc::ty::TyCtxt;
use rustc::middle::const_val::ConstVal;
use rustc::mir::transform::{MirPass, MirSource, Pass};
use rustc::mir::*;
use std::fmt;
pub struct SimplifyBranches<'a> { label: &'a str }
impl<'a> SimplifyBranches<'a> {
pub fn new(label: &'a str) -> Self {
SimplifyBranches { label: label }
}
}
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::SwitchInt { discr: Operand::Constant(Constant {
literal: Literal::Value { ref value }, ..
}), ref values, ref targets, .. } => {
if let Some(ref constint) = value.to_const_int() {
let (otherwise, targets) = targets.split_last().unwrap();
let mut ret = TerminatorKind::Goto { target: *otherwise };
for (v, t) in values.iter().zip(targets.iter()) {
if v == constint {
ret = TerminatorKind::Goto { target: *t };
break;
}
}
ret
} else {
continue
}
},
TerminatorKind::Assert { target, cond: Operand::Constant(Constant {
literal: Literal::Value {
value: ConstVal::Bool(cond)
}, ..
}), expected, .. } if cond == expected => {
TerminatorKind::Goto { target: target }
},
_ => continue
};
}
}
}
impl<'l> Pass for SimplifyBranches<'l> {
fn disambiguator<'a>(&'a self) -> Option<Box<fmt::Display+'a>> {
Some(Box::new(self.label))
}
fn name(&self) -> ::std::borrow::Cow<'static, str> { "SimplifyBranches".into() }
}