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Don't allocate a local array at all if there are no locals

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Oliver Schneider 2018-03-23 10:47:55 +01:00
parent b18b776b8f
commit 4ea4dd23cd
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1 changed files with 22 additions and 16 deletions
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38
src/librustc_mir/interpret/eval_context.rs
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@ -383,24 +383,30 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
) -> EvalResult<'tcx> { ) -> EvalResult<'tcx> {
::log_settings::settings().indentation += 1; ::log_settings::settings().indentation += 1;
let mut locals = IndexVec::from_elem(Some(Value::ByVal(PrimVal::Undef)), &mir.local_decls); let locals = if mir.local_decls.len() > 1 {
match self.tcx.describe_def(instance.def_id()) { let mut locals = IndexVec::from_elem(Some(Value::ByVal(PrimVal::Undef)), &mir.local_decls);
// statics and constants don't have `Storage*` statements, no need to look for them match self.tcx.describe_def(instance.def_id()) {
Some(Def::Static(..)) | Some(Def::Const(..)) | Some(Def::AssociatedConst(..)) => {}, // statics and constants don't have `Storage*` statements, no need to look for them
_ => { Some(Def::Static(..)) | Some(Def::Const(..)) | Some(Def::AssociatedConst(..)) => {},
trace!("push_stack_frame: {:?}: num_bbs: {}", span, mir.basic_blocks().len()); _ => {
for block in mir.basic_blocks() { trace!("push_stack_frame: {:?}: num_bbs: {}", span, mir.basic_blocks().len());
for stmt in block.statements.iter() { for block in mir.basic_blocks() {
use rustc::mir::StatementKind::{StorageDead, StorageLive}; for stmt in block.statements.iter() {
match stmt.kind { use rustc::mir::StatementKind::{StorageDead, StorageLive};
StorageLive(local) | match stmt.kind {
StorageDead(local) => locals[local] = None, StorageLive(local) |
_ => {} StorageDead(local) => locals[local] = None,
_ => {}
}
} }
} }
} },
}, }
} locals
} else {
// don't allocate at all for trivial constants
IndexVec::new()
};
self.stack.push(Frame { self.stack.push(Frame {
mir, mir,