use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
use tracing::trace;
pub enum SimplifyConstCondition {
AfterConstProp,
Final,
}
impl<'tcx> MirPass<'tcx> for SimplifyConstCondition {
fn name(&self) -> &'static str {
match self {
SimplifyConstCondition::AfterConstProp => "SimplifyConstCondition-after-const-prop",
SimplifyConstCondition::Final => "SimplifyConstCondition-final",
}
}
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
trace!("Running SimplifyConstCondition on {:?}", body.source);
let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
'blocks: for block in body.basic_blocks_mut() {
for stmt in block.statements.iter_mut() {
if let StatementKind::Intrinsic(box ref intrinsic) = stmt.kind
&& let NonDivergingIntrinsic::Assume(discr) = intrinsic
&& let Operand::Constant(ref c) = discr
&& let Some(constant) = c.const_.try_eval_bool(tcx, param_env)
{
if constant {
stmt.make_nop();
} else {
block.statements.clear();
block.terminator_mut().kind = TerminatorKind::Unreachable;
continue 'blocks;
}
}
}
let terminator = block.terminator_mut();
terminator.kind = match terminator.kind {
TerminatorKind::SwitchInt {
discr: Operand::Constant(ref c), ref targets, ..
} => {
let constant = c.const_.try_eval_bits(tcx, param_env);
if let Some(constant) = constant {
let target = targets.target_for_value(constant);
TerminatorKind::Goto { target }
} else {
continue;
}
}
TerminatorKind::Assert {
target, cond: Operand::Constant(ref c), expected, ..
} => match c.const_.try_eval_bool(tcx, param_env) {
Some(v) if v == expected => TerminatorKind::Goto { target },
_ => continue,
},
_ => continue,
};
}
}
}