also step through promoteds, constants and statics

src/interpreter/mod.rs

@@ -20,6 +20,8 @@ use error::{EvalError, EvalResult};
 use memory::{Memory, Pointer};
 use primval::{self, PrimVal};
 
+use std::collections::HashMap;
+
 mod stepper;
 
 struct GlobalEvalContext<'a, 'tcx: 'a> {
@@ -45,6 +47,9 @@ struct GlobalEvalContext<'a, 'tcx: 'a> {
     ///   * Function DefIds and Substs to print proper substituted function names.
     ///   * Spans pointing to specific function calls in the source.
     name_stack: Vec<(DefId, &'tcx Substs<'tcx>, codemap::Span)>,
+
+    /// Precomputed statics and constants
+    statics: DefIdMap<Pointer>,
 }
 
 struct FnEvalContext<'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> {
@@ -88,6 +93,9 @@ struct Frame<'a, 'tcx: 'a> {
 
     /// The offset of the first temporary in `self.locals`.
     temp_offset: usize,
+
+    /// List of precomputed promoted constants
+    promoted: HashMap<usize, Pointer>,
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
@@ -122,6 +130,13 @@ enum TerminatorTarget {
     Return,
 }
 
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+enum ConstantId {
+    Promoted { index: usize },
+    Static { def_id: DefId },
+}
+
+
 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
         GlobalEvalContext {
@@ -135,10 +150,11 @@ impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
                                    .expect("Session::target::uint_type was usize")/8),
             substs_stack: Vec::new(),
             name_stack: Vec::new(),
+            statics: DefIdMap(),
         }
     }
 
-    fn call(&mut self, mir: &mir::Mir<'tcx>) -> EvalResult<Option<Pointer>> {
+    fn call(&mut self, mir: &mir::Mir<'tcx>, def_id: DefId) -> EvalResult<Option<Pointer>> {
         let mut nested_fecx = FnEvalContext::new(self);
 
         let return_ptr = match mir.return_ty {
@@ -150,6 +166,7 @@ impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
         };
 
         let substs = nested_fecx.substs();
+        nested_fecx.name_stack.push((def_id, substs, mir.span));
         nested_fecx.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
         nested_fecx.run()?;
         Ok(return_ptr)
@@ -193,9 +210,9 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
 
             loop {
                 match stepper.step()? {
-                    Assignment(statement) => trace!("{:?}", statement),
-                    Terminator(terminator) => {
-                        trace!("{:?}", terminator.kind);
+                    Assignment => trace!("{:?}", stepper.stmt()),
+                    Terminator => {
+                        trace!("{:?}", stepper.term().kind);
                         continue 'outer;
                     },
                     Done => return Ok(()),
@@ -230,6 +247,7 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
             locals: locals,
             var_offset: num_args,
             temp_offset: num_args + num_vars,
+            promoted: HashMap::new(),
         });
     }
 
@@ -983,13 +1001,7 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
                 match *literal {
                     Value { ref value } => Ok(self.const_to_ptr(value)?),
                     Item { .. } => Err(EvalError::Unimplemented(format!("literal items (e.g. mentions of function items) are unimplemented"))),
-                    Promoted { index } => {
-                        // TODO(solson): Mark constants and statics as read-only and cache their
-                        // values.
-                        let current_mir = self.mir();
-                        let mir = &current_mir.promoted[index];
-                        self.gecx.call(mir).map(Option::unwrap)
-                    }
+                    Promoted { index } => Ok(*self.frame().promoted.get(&index).expect("a promoted constant hasn't been precomputed")),
                 }
             }
         }
@@ -1004,11 +1016,7 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
 
-            Static(def_id) => {
-                // TODO(solson): Mark constants and statics as read-only and cache their values.
-                let mir = self.load_mir(def_id);
-                self.gecx.call(&mir)?.unwrap()
-            }
+            Static(def_id) => *self.gecx.statics.get(&def_id).expect("static should have been cached"),
 
             Projection(ref proj) => {
                 let base = self.eval_lvalue(&proj.base)?;
@@ -1412,7 +1420,7 @@ pub fn interpret_start_points<'a, 'tcx>(
                 debug!("Interpreting: {}", item.name);
 
                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
-                match gecx.call(mir) {
+                match gecx.call(mir, tcx.map.local_def_id(id)) {
                     Ok(Some(return_ptr)) => if log_enabled!(::log::LogLevel::Debug) {
                         gecx.memory.dump(return_ptr.alloc_id);
                     },

src/interpreter/stepper.rs

@@ -2,49 +2,61 @@ use super::{
     FnEvalContext,
     CachedMir,
     TerminatorTarget,
+    ConstantId,
 };
 use error::EvalResult;
 use rustc::mir::repr as mir;
+use rustc::ty::{self, subst};
+use rustc::mir::visit::Visitor;
+use syntax::codemap::Span;
+use memory::Pointer;
+use std::rc::Rc;
 
-pub enum Event<'a, 'tcx: 'a> {
-    Assignment(&'a mir::Statement<'tcx>),
-    Terminator(&'a mir::Terminator<'tcx>),
+pub enum Event {
+    Assignment,
+    Terminator,
     Done,
 }
 
 pub struct Stepper<'fncx, 'a: 'fncx, 'b: 'a + 'mir, 'mir: 'fncx, 'tcx: 'b>{
     fncx: &'fncx mut FnEvalContext<'a, 'b, 'mir, 'tcx>,
     block: mir::BasicBlock,
-    stmt: usize,
+    // a stack of statement positions
+    stmt: Vec<usize>,
     mir: CachedMir<'mir, 'tcx>,
     process: fn (&mut Stepper<'fncx, 'a, 'b, 'mir, 'tcx>) -> EvalResult<()>,
+    // a stack of constants
+    constants: Vec<Vec<(ConstantId, Span)>>,
 }
 
 impl<'fncx, 'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> Stepper<'fncx, 'a, 'b, 'mir, 'tcx> {
     pub(super) fn new(fncx: &'fncx mut FnEvalContext<'a, 'b, 'mir, 'tcx>) -> Self {
-        Stepper {
+        let mut stepper = Stepper {
             block: fncx.frame().next_block,
             mir: fncx.mir(),
             fncx: fncx,
-            stmt: 0,
+            stmt: vec![0],
             process: Self::dummy,
-        }
+            constants: Vec::new(),
+        };
+        stepper.extract_constants();
+        stepper
     }
 
     fn dummy(&mut self) -> EvalResult<()> { Ok(()) }
 
     fn statement(&mut self) -> EvalResult<()> {
         let block_data = self.mir.basic_block_data(self.block);
-        let stmt = &block_data.statements[self.stmt];
+        let stmt = &block_data.statements[*self.stmt.last().unwrap()];
         let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
         let result = self.fncx.eval_assignment(lvalue, rvalue);
         self.fncx.maybe_report(stmt.span, result)?;
-        self.stmt += 1;
+        *self.stmt.last_mut().unwrap() += 1;
         Ok(())
     }
 
     fn terminator(&mut self) -> EvalResult<()> {
-        self.stmt = 0;
+        *self.stmt.last_mut().unwrap() = 0;
         let term = {
             let block_data = self.mir.basic_block_data(self.block);
             let terminator = block_data.terminator();
@@ -58,6 +70,9 @@ impl<'fncx, 'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> Stepper<'fncx, 'a, 'b, 'mir, 'tcx
             TerminatorTarget::Return => {
                 self.fncx.pop_stack_frame();
                 self.fncx.name_stack.pop();
+                self.stmt.pop();
+                assert!(self.constants.last().unwrap().is_empty());
+                self.constants.pop();
                 if !self.fncx.stack.is_empty() {
                     self.block = self.fncx.frame().next_block;
                     self.mir = self.fncx.mir();
@@ -66,12 +81,24 @@ impl<'fncx, 'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> Stepper<'fncx, 'a, 'b, 'mir, 'tcx
             TerminatorTarget::Call => {
                 self.block = self.fncx.frame().next_block;
                 self.mir = self.fncx.mir();
+                self.stmt.push(0);
+                self.extract_constants();
             },
         }
         Ok(())
     }
 
-    pub fn step<'step>(&'step mut self) -> EvalResult<Event<'step, 'tcx>> {
+    fn alloc(&mut self, ty: ty::FnOutput<'tcx>) -> Pointer {
+        match ty {
+            ty::FnConverging(ty) => {
+                let size = self.fncx.type_size(ty);
+                self.fncx.memory.allocate(size)
+            }
+            ty::FnDiverging => panic!("there's no such thing as an unreachable static"),
+        }
+    }
+
+    pub fn step(&mut self) -> EvalResult<Event> {
         (self.process)(self)?;
 
         if self.fncx.stack.is_empty() {
@@ -80,18 +107,97 @@ impl<'fncx, 'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> Stepper<'fncx, 'a, 'b, 'mir, 'tcx
             return Ok(Event::Done);
         }
 
+        match self.constants.last_mut().unwrap().pop() {
+            Some((ConstantId::Promoted { index }, span)) => {
+                trace!("adding promoted constant {}", index);
+                let mir = self.mir.promoted[index].clone();
+                let return_ptr = self.alloc(mir.return_ty);
+                self.fncx.frame_mut().promoted.insert(index, return_ptr);
+                let substs = self.fncx.substs();
+                // FIXME: somehow encode that this is a promoted constant's frame
+                println!("{}, {}, {}", self.fncx.stack.len(), self.fncx.name_stack.len(), self.fncx.substs_stack.len());
+                let def_id = self.fncx.name_stack.last().unwrap().0;
+                self.fncx.name_stack.push((def_id, substs, span));
+                self.fncx.push_stack_frame(CachedMir::Owned(Rc::new(mir)), substs, Some(return_ptr));
+                self.stmt.push(0);
+                self.constants.push(Vec::new());
+                self.block = self.fncx.frame().next_block;
+                self.mir = self.fncx.mir();
+            },
+            Some((ConstantId::Static { def_id }, span)) => {
+                trace!("adding static {:?}", def_id);
+                let mir = self.fncx.load_mir(def_id);
+                let return_ptr = self.alloc(mir.return_ty);
+                self.fncx.gecx.statics.insert(def_id, return_ptr);
+                let substs = self.fncx.tcx.mk_substs(subst::Substs::empty());
+                self.fncx.name_stack.push((def_id, substs, span));
+                self.fncx.push_stack_frame(mir, substs, Some(return_ptr));
+                self.stmt.push(0);
+                self.constants.push(Vec::new());
+                self.block = self.fncx.frame().next_block;
+                self.mir = self.fncx.mir();
+            },
+            None => {},
+        }
+
         let basic_block = self.mir.basic_block_data(self.block);
 
-        if let Some(stmt) = basic_block.statements.get(self.stmt) {
+        if basic_block.statements.len() > *self.stmt.last().unwrap() {
             self.process = Self::statement;
-            return Ok(Event::Assignment(&stmt));
+            return Ok(Event::Assignment);
         }
 
         self.process = Self::terminator;
-        Ok(Event::Terminator(basic_block.terminator()))
+        Ok(Event::Terminator)
     }
-    
+
+    /// returns the basic block index of the currently processed block
     pub fn block(&self) -> mir::BasicBlock {
         self.block
     }
+
+    /// returns the statement that will be processed next
+    pub fn stmt(&self) -> &mir::Statement {
+        let block_data = self.mir.basic_block_data(self.block);
+        &block_data.statements[*self.stmt.last().unwrap()]
+    }
+
+    /// returns the terminator of the current block
+    pub fn term(&self) -> &mir::Terminator {
+        let block_data = self.mir.basic_block_data(self.block);
+        block_data.terminator()
+    }
+
+    fn extract_constants(&mut self) {
+        let mut extractor = ConstantExtractor {
+            constants: Vec::new(),
+        };
+        extractor.visit_mir(&self.mir);
+        self.constants.push(extractor.constants);
+    }
+}
+
+struct ConstantExtractor {
+    constants: Vec<(ConstantId, Span)>,
+}
+
+impl<'tcx> Visitor<'tcx> for ConstantExtractor {
+    fn visit_constant(&mut self, constant: &mir::Constant<'tcx>) {
+        self.super_constant(constant);
+        match constant.literal {
+            // already computed by rustc
+            mir::Literal::Value { .. } => {}
+            mir::Literal::Item { .. } => {}, // FIXME: unimplemented
+            mir::Literal::Promoted { index } => {
+                self.constants.push((ConstantId::Promoted { index: index }, constant.span));
+            }
+        }
+    }
+
+    fn visit_statement(&mut self, block: mir::BasicBlock, stmt: &mir::Statement<'tcx>) {
+        self.super_statement(block, stmt);
+        if let mir::StatementKind::Assign(mir::Lvalue::Static(def_id), _) = stmt.kind {
+            self.constants.push((ConstantId::Static { def_id: def_id }, stmt.span));
+        }
+    }
 }

tests/compile-fail/unimplemented.rs

@@ -1,16 +1,12 @@
 #![feature(custom_attribute)]
 #![allow(dead_code, unused_attributes)]
 
-//error-pattern:literal items (e.g. mentions of function items) are unimplemented
+//error-pattern:static should have been cached
 
-static mut X: usize = 5;
 
 #[miri_run]
-fn static_mut() {
-    unsafe {
-        X = 6;
-        assert_eq!(X, 6);
-    }
+fn failed_assertions() {
+    assert_eq!(5, 6);
 }
 
 fn main() {}

tests/run-pass/bug.rs

@@ -0,0 +1,14 @@
+#![feature(custom_attribute)]
+#![allow(dead_code, unused_attributes)]
+
+static mut X: usize = 5;
+
+#[miri_run]
+fn static_mut() {
+    unsafe {
+        X = 6;
+        assert_eq!(X, 6);
+    }
+}
+
+fn main() {}