40ae34194c
detects redundant imports that can be eliminated. for #117772 : In order to facilitate review and modification, split the checking code and removing redundant imports code into two PR.
60 lines
2.4 KiB
Rust
60 lines
2.4 KiB
Rust
use rustc_middle::mir::*;
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use rustc_middle::ty::TyCtxt;
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pub enum SimplifyConstCondition {
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AfterConstProp,
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Final,
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}
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/// A pass that replaces a branch with a goto when its condition is known.
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impl<'tcx> MirPass<'tcx> for SimplifyConstCondition {
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fn name(&self) -> &'static str {
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match self {
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SimplifyConstCondition::AfterConstProp => "SimplifyConstCondition-after-const-prop",
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SimplifyConstCondition::Final => "SimplifyConstCondition-final",
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}
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}
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fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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trace!("Running SimplifyConstCondition on {:?}", body.source);
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let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
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'blocks: for block in body.basic_blocks_mut() {
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for stmt in block.statements.iter_mut() {
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if let StatementKind::Intrinsic(box ref intrinsic) = stmt.kind
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&& let NonDivergingIntrinsic::Assume(discr) = intrinsic
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&& let Operand::Constant(ref c) = discr
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&& let Some(constant) = c.const_.try_eval_bool(tcx, param_env)
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{
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if constant {
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stmt.make_nop();
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} else {
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block.statements.clear();
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block.terminator_mut().kind = TerminatorKind::Unreachable;
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continue 'blocks;
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}
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}
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}
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let terminator = block.terminator_mut();
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terminator.kind = match terminator.kind {
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TerminatorKind::SwitchInt {
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discr: Operand::Constant(ref c), ref targets, ..
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} => {
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let constant = c.const_.try_eval_bits(tcx, param_env);
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if let Some(constant) = constant {
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let target = targets.target_for_value(constant);
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TerminatorKind::Goto { target }
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} else {
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continue;
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}
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}
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TerminatorKind::Assert {
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target, cond: Operand::Constant(ref c), expected, ..
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} => match c.const_.try_eval_bool(tcx, param_env) {
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Some(v) if v == expected => TerminatorKind::Goto { target },
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_ => continue,
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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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