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Small optimization

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Optimiize ExprKind::EmptyToAny expressions applied to function calls.
This commit is contained in:
Andrew Cann 2016-06-28 01:44:50 +08:00
parent 798f719daf
commit 533a389962
1 changed files with 16 additions and 4 deletions
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20
src/librustc_mir/build/expr/into.rs
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@ -46,12 +46,24 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
this.match_expr(destination, expr_span, block, discriminant, arms)
}
ExprKind::EmptyToAny { source } => {
// TODO(canndrew): Do we need to do this?
let source = this.hir.mirror(source);
let is_call = match source.kind {
ExprKind::Call { .. } => true,
_ => false,
};
unpack!(block = this.as_rvalue(block, source));
this.cfg.terminate(block, source_info, TerminatorKind::Unreachable);
let end_block = this.cfg.start_new_block();
end_block.unit()
// This is an optimization. If the expression was a call then we already have an
// unreachable block. Don't bother to terminate it and create a new one.
if is_call {
block.unit()
}
else {
this.cfg.terminate(block, source_info, TerminatorKind::Unreachable);
let end_block = this.cfg.start_new_block();
end_block.unit()
}
}
ExprKind::If { condition: cond_expr, then: then_expr, otherwise: else_expr } => {
let operand = unpack!(block = this.as_operand(block, cond_expr));