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use rustc::ty::{self, TyCtxt};
use rustc::middle::const_val::ConstVal;
use rustc::mir::*;
use rustc::mir::interpret::{Value, PrimVal};
use transform::{MirPass, MirSource};
use std::borrow::Cow;
pub struct SimplifyBranches { label: String }
impl SimplifyBranches {
pub fn new(label: &str) -> Self {
SimplifyBranches { label: format!("SimplifyBranches-{}", label) }
}
}
impl MirPass for SimplifyBranches {
fn name<'a>(&'a self) -> Cow<'a, str> {
Cow::Borrowed(&self.label)
}
fn run_pass<'a, 'tcx>(&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(box Constant {
literal: Literal::Value { ref value }, ..
}), ref values, ref targets, .. } => {
if let Some(constint) = value.val.to_raw_bits() {
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(box Constant {
literal: Literal::Value {
value: &ty::Const {
val: ConstVal::Value(Value::ByVal(PrimVal::Bytes(cond))),
.. }
}, ..
}), expected, .. } if (cond == 1) == expected => {
assert!(cond <= 1);
TerminatorKind::Goto { target: target }
},
TerminatorKind::FalseEdges { real_target, .. } => {
TerminatorKind::Goto { target: real_target }
},
TerminatorKind::FalseUnwind { real_target, .. } => {
TerminatorKind::Goto { target: real_target }
},
_ => continue
};
}
}
}