303 lines
12 KiB
Rust
303 lines
12 KiB
Rust
//! This module contains the `EvalContext` methods for executing a single step of the interpreter.
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//!
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//! The main entry point is the `step` method.
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use rustc::hir::def_id::DefId;
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use rustc::hir;
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use rustc::mir::visit::{Visitor, LvalueContext};
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use rustc::mir::{self, ValidationOp};
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use rustc::traits::Reveal;
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use rustc::ty::layout::Layout;
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use rustc::ty::{subst, self};
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use error::{EvalResult, EvalError};
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use eval_context::{EvalContext, StackPopCleanup};
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use lvalue::{Global, GlobalId, Lvalue};
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use value::{Value, PrimVal};
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use syntax::codemap::Span;
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use syntax::ast::Mutability;
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impl<'a, 'tcx> EvalContext<'a, 'tcx> {
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pub fn inc_step_counter_and_check_limit(&mut self, n: u64) -> EvalResult<'tcx> {
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self.steps_remaining = self.steps_remaining.saturating_sub(n);
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if self.steps_remaining > 0 {
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Ok(())
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} else {
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Err(EvalError::ExecutionTimeLimitReached)
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}
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}
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/// Returns true as long as there are more things to do.
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pub fn step(&mut self) -> EvalResult<'tcx, bool> {
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self.inc_step_counter_and_check_limit(1)?;
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if self.stack.is_empty() {
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return Ok(false);
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}
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let cur_frame = self.cur_frame();
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self.memory.set_cur_frame(cur_frame);
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let block = self.frame().block;
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let stmt_id = self.frame().stmt;
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let mir = self.mir();
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let basic_block = &mir.basic_blocks()[block];
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if let Some(stmt) = basic_block.statements.get(stmt_id) {
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let mut new = Ok(0);
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ConstantExtractor {
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span: stmt.source_info.span,
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instance: self.frame().instance,
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ecx: self,
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mir,
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new_constants: &mut new,
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}.visit_statement(block, stmt, mir::Location { block, statement_index: stmt_id });
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// if ConstantExtractor added new frames, we don't execute anything here
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// but await the next call to step
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if new? == 0 {
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self.statement(stmt)?;
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}
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return Ok(true);
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}
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let terminator = basic_block.terminator();
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let mut new = Ok(0);
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ConstantExtractor {
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span: terminator.source_info.span,
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instance: self.frame().instance,
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ecx: self,
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mir,
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new_constants: &mut new,
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}.visit_terminator(block, terminator, mir::Location { block, statement_index: stmt_id });
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// if ConstantExtractor added new frames, we don't execute anything here
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// but await the next call to step
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if new? == 0 {
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self.terminator(terminator)?;
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}
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Ok(true)
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}
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fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> EvalResult<'tcx> {
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trace!("{:?}", stmt);
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use rustc::mir::StatementKind::*;
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match stmt.kind {
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Assign(ref lvalue, ref rvalue) => self.eval_rvalue_into_lvalue(rvalue, lvalue)?,
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SetDiscriminant { ref lvalue, variant_index } => {
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let dest = self.eval_lvalue(lvalue)?;
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let dest_ty = self.lvalue_ty(lvalue);
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let dest_layout = self.type_layout(dest_ty)?;
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match *dest_layout {
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Layout::General { discr, .. } => {
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let discr_size = discr.size().bytes();
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let dest_ptr = self.force_allocation(dest)?.to_ptr()?;
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self.memory.write_uint(dest_ptr, variant_index as u128, discr_size)?
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}
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Layout::RawNullablePointer { nndiscr, .. } => {
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if variant_index as u64 != nndiscr {
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self.write_null(dest, dest_ty)?;
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}
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}
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Layout::StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
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if variant_index as u64 != nndiscr {
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let (offset, ty) = self.nonnull_offset_and_ty(dest_ty, nndiscr, discrfield)?;
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let nonnull = self.force_allocation(dest)?.to_ptr()?.offset(offset.bytes(), &self)?;
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trace!("struct wrapped nullable pointer type: {}", ty);
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// only the pointer part of a fat pointer is used for this space optimization
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let discr_size = self.type_size(ty)?.expect("bad StructWrappedNullablePointer discrfield");
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self.memory.write_uint(nonnull, 0, discr_size)?;
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}
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},
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_ => bug!("SetDiscriminant on {} represented as {:#?}", dest_ty, dest_layout),
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}
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}
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// Mark locals as dead or alive.
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StorageLive(ref lvalue) | StorageDead(ref lvalue)=> {
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let (frame, local) = match self.eval_lvalue(lvalue)? {
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Lvalue::Local{ frame, local } if self.cur_frame() == frame => (frame, local),
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_ => return Err(EvalError::Unimplemented("Storage annotations must refer to locals of the topmost stack frame.".to_owned())) // FIXME maybe this should get its own error type
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};
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let old_val = match stmt.kind {
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StorageLive(_) => self.stack[frame].storage_live(local)?,
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StorageDead(_) => self.stack[frame].storage_dead(local)?,
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_ => bug!("We already checked that we are a storage stmt")
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};
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self.deallocate_local(old_val)?;
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}
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// Validity checks.
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Validate(ref op, ref lvalues) => {
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match *op {
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ValidationOp::Acquire => {
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for operand in lvalues {
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let lvalue = self.eval_lvalue(&operand.lval)?;
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self.acquire_valid(lvalue, operand.ty, hir::MutMutable)?;
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}
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}
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_ => { /* not yet implemented */ }
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}
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}
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// Just a borrowck thing
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EndRegion(..) => {}
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// Defined to do nothing. These are added by optimization passes, to avoid changing the
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// size of MIR constantly.
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Nop => {}
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InlineAsm { .. } => return Err(EvalError::InlineAsm),
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}
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self.frame_mut().stmt += 1;
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Ok(())
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}
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fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> EvalResult<'tcx> {
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trace!("{:?}", terminator.kind);
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self.eval_terminator(terminator)?;
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if !self.stack.is_empty() {
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trace!("// {:?}", self.frame().block);
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}
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Ok(())
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}
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}
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// WARNING: make sure that any methods implemented on this type don't ever access ecx.stack
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// this includes any method that might access the stack
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// basically don't call anything other than `load_mir`, `alloc_ptr`, `push_stack_frame`
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// The reason for this is, that `push_stack_frame` modifies the stack out of obvious reasons
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struct ConstantExtractor<'a, 'b: 'a, 'tcx: 'b> {
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span: Span,
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ecx: &'a mut EvalContext<'b, 'tcx>,
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mir: &'tcx mir::Mir<'tcx>,
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instance: ty::Instance<'tcx>,
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new_constants: &'a mut EvalResult<'tcx, u64>,
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}
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impl<'a, 'b, 'tcx> ConstantExtractor<'a, 'b, 'tcx> {
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fn global_item(
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&mut self,
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def_id: DefId,
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substs: &'tcx subst::Substs<'tcx>,
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span: Span,
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mutability: Mutability,
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) {
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let instance = self.ecx.resolve_associated_const(def_id, substs);
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let cid = GlobalId { instance, promoted: None };
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if self.ecx.globals.contains_key(&cid) {
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return;
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}
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if self.ecx.tcx.has_attr(def_id, "linkage") {
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trace!("Initializing an extern global with NULL");
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self.ecx.globals.insert(cid, Global::initialized(self.ecx.tcx.type_of(def_id), Value::ByVal(PrimVal::Bytes(0)), mutability));
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return;
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}
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self.try(|this| {
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let mir = this.ecx.load_mir(instance.def)?;
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this.ecx.globals.insert(cid, Global::uninitialized(mir.return_ty));
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let internally_mutable = !mir.return_ty.is_freeze(
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this.ecx.tcx,
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ty::ParamEnv::empty(Reveal::All),
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span);
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let mutability = if mutability == Mutability::Mutable || internally_mutable {
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Mutability::Mutable
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} else {
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Mutability::Immutable
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};
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let cleanup = StackPopCleanup::MarkStatic(mutability);
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let name = ty::tls::with(|tcx| tcx.item_path_str(def_id));
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trace!("pushing stack frame for global: {}", name);
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this.ecx.push_stack_frame(
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instance,
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span,
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mir,
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Lvalue::Global(cid),
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cleanup,
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)
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});
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}
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fn try<F: FnOnce(&mut Self) -> EvalResult<'tcx>>(&mut self, f: F) {
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if let Ok(ref mut n) = *self.new_constants {
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*n += 1;
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} else {
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return;
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}
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if let Err(e) = f(self) {
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*self.new_constants = Err(e);
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}
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}
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}
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impl<'a, 'b, 'tcx> Visitor<'tcx> for ConstantExtractor<'a, 'b, 'tcx> {
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fn visit_constant(&mut self, constant: &mir::Constant<'tcx>, location: mir::Location) {
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self.super_constant(constant, location);
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match constant.literal {
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// already computed by rustc
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mir::Literal::Value { .. } => {}
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mir::Literal::Item { def_id, substs } => {
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self.global_item(def_id, substs, constant.span, Mutability::Immutable);
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},
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mir::Literal::Promoted { index } => {
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let cid = GlobalId {
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instance: self.instance,
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promoted: Some(index),
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};
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if self.ecx.globals.contains_key(&cid) {
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return;
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}
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let mir = &self.mir.promoted[index];
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self.try(|this| {
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let ty = this.ecx.monomorphize(mir.return_ty, this.instance.substs);
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this.ecx.globals.insert(cid, Global::uninitialized(ty));
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trace!("pushing stack frame for {:?}", index);
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this.ecx.push_stack_frame(this.instance,
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constant.span,
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mir,
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Lvalue::Global(cid),
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StackPopCleanup::MarkStatic(Mutability::Immutable),
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)
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});
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}
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}
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}
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fn visit_lvalue(
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&mut self,
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lvalue: &mir::Lvalue<'tcx>,
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context: LvalueContext<'tcx>,
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location: mir::Location
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) {
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self.super_lvalue(lvalue, context, location);
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if let mir::Lvalue::Static(ref static_) = *lvalue {
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let def_id = static_.def_id;
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let substs = self.ecx.tcx.intern_substs(&[]);
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let span = self.span;
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if let Some(node_item) = self.ecx.tcx.hir.get_if_local(def_id) {
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if let hir::map::Node::NodeItem(&hir::Item { ref node, .. }) = node_item {
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if let hir::ItemStatic(_, m, _) = *node {
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self.global_item(def_id, substs, span, if m == hir::MutMutable { Mutability::Mutable } else { Mutability::Immutable });
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return;
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} else {
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bug!("static def id doesn't point to static");
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}
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} else {
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bug!("static def id doesn't point to item");
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}
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} else {
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let def = self.ecx.tcx.describe_def(def_id).expect("static not found");
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if let hir::def::Def::Static(_, mutable) = def {
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self.global_item(def_id, substs, span, if mutable { Mutability::Mutable } else { Mutability::Immutable });
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} else {
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bug!("static found but isn't a static: {:?}", def);
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}
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}
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}
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}
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}
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