Add a MIR visitor

src/librustc_mir/lib.rs

@@ -35,4 +35,5 @@ mod hair;
 pub mod repr;
 mod graphviz;
 pub mod tcx;
+pub mod visit;
 

src/librustc_mir/visit.rs

@@ -0,0 +1,239 @@
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use rustc::middle::ty::Region;
+use repr::*;
+
+pub trait Visitor<'tcx> {
+    // Override these, and call `self.super_xxx` to revert back to the
+    // default behavior.
+
+    fn visit_mir(&mut self, mir: &Mir<'tcx>) {
+        self.super_mir(mir);
+    }
+
+    fn visit_basic_block_data(&mut self, block: BasicBlock, data: &BasicBlockData<'tcx>) {
+        self.super_basic_block_data(block, data);
+    }
+
+    fn visit_statement(&mut self, block: BasicBlock, statement: &Statement<'tcx>) {
+        self.super_statement(block, statement);
+    }
+
+    fn visit_assign(&mut self, block: BasicBlock, lvalue: &Lvalue<'tcx>, rvalue: &Rvalue<'tcx>) {
+        self.super_assign(block, lvalue, rvalue);
+    }
+
+    fn visit_terminator(&mut self, block: BasicBlock, terminator: &Terminator<'tcx>) {
+        self.super_terminator(block, terminator);
+    }
+
+    fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>) {
+        self.super_rvalue(rvalue);
+    }
+
+    fn visit_operand(&mut self, operand: &Operand<'tcx>) {
+        self.super_operand(operand);
+    }
+
+    fn visit_lvalue(&mut self, lvalue: &Lvalue<'tcx>, context: LvalueContext) {
+        self.super_lvalue(lvalue, context);
+    }
+
+    fn visit_branch(&mut self, source: BasicBlock, target: BasicBlock) {
+        self.super_branch(source, target);
+    }
+
+    fn visit_constant(&mut self, constant: &Constant<'tcx>) {
+        self.super_constant(constant);
+    }
+
+    // The `super_xxx` methods comprise the default behavior and are
+    // not meant to be overidden.
+
+    fn super_mir(&mut self, mir: &Mir<'tcx>) {
+        for block in mir.all_basic_blocks() {
+            let data = mir.basic_block_data(block);
+            self.visit_basic_block_data(block, data);
+        }
+    }
+
+    fn super_basic_block_data(&mut self, block: BasicBlock, data: &BasicBlockData<'tcx>) {
+        for statement in &data.statements {
+            self.visit_statement(block, statement);
+        }
+        self.visit_terminator(block, &data.terminator);
+    }
+
+    fn super_statement(&mut self, block: BasicBlock, statement: &Statement<'tcx>) {
+        match statement.kind {
+            StatementKind::Assign(ref lvalue, ref rvalue) => {
+                self.visit_assign(block, lvalue, rvalue);
+            }
+            StatementKind::Drop(_, ref lvalue) => {
+                self.visit_lvalue(lvalue, LvalueContext::Drop);
+            }
+        }
+    }
+
+    fn super_assign(&mut self, _block: BasicBlock, lvalue: &Lvalue<'tcx>, rvalue: &Rvalue<'tcx>) {
+        self.visit_lvalue(lvalue, LvalueContext::Store);
+        self.visit_rvalue(rvalue);
+    }
+
+    fn super_terminator(&mut self, block: BasicBlock, terminator: &Terminator<'tcx>) {
+        match *terminator {
+            Terminator::Goto { target } |
+            Terminator::Panic { target } => {
+                self.visit_branch(block, target);
+            }
+
+            Terminator::If { ref cond, ref targets } => {
+                self.visit_operand(cond);
+                for &target in &targets[..] {
+                    self.visit_branch(block, target);
+                }
+            }
+
+            Terminator::Switch { ref discr, adt_def: _, ref targets } => {
+                self.visit_lvalue(discr, LvalueContext::Inspect);
+                for &target in targets {
+                    self.visit_branch(block, target);
+                }
+            }
+
+            Terminator::Diverge |
+            Terminator::Return => {
+            }
+
+            Terminator::Call { ref data, ref targets } => {
+                self.visit_lvalue(&data.destination, LvalueContext::Store);
+                self.visit_operand(&data.func);
+                for arg in &data.args {
+                    self.visit_operand(arg);
+                }
+                for &target in &targets[..] {
+                    self.visit_branch(block, target);
+                }
+            }
+        }
+    }
+
+    fn super_rvalue(&mut self, rvalue: &Rvalue<'tcx>) {
+        match *rvalue {
+            Rvalue::Use(ref operand) => {
+                self.visit_operand(operand);
+            }
+
+            Rvalue::Repeat(ref value, ref len) => {
+                self.visit_operand(value);
+                self.visit_operand(len);
+            }
+
+            Rvalue::Ref(r, bk, ref path) => {
+                self.visit_lvalue(path, LvalueContext::Borrow {
+                    region: r,
+                    kind: bk
+                });
+            }
+
+            Rvalue::Len(ref path) => {
+                self.visit_lvalue(path, LvalueContext::Inspect);
+            }
+
+            Rvalue::Cast(_, ref operand, _) => {
+                self.visit_operand(operand);
+            }
+
+            Rvalue::BinaryOp(_, ref lhs, ref rhs) => {
+                self.visit_operand(lhs);
+                self.visit_operand(rhs);
+            }
+
+            Rvalue::UnaryOp(_, ref op) => {
+                self.visit_operand(op);
+            }
+
+            Rvalue::Box(_) => {
+            }
+
+            Rvalue::Aggregate(_, ref operands) => {
+                for operand in operands {
+                    self.visit_operand(operand);
+                }
+            }
+
+            Rvalue::Slice { ref input, from_start, from_end } => {
+                self.visit_lvalue(input, LvalueContext::Slice {
+                    from_start: from_start,
+                    from_end: from_end,
+                });
+            }
+
+            Rvalue::InlineAsm(_) => {
+            }
+        }
+    }
+
+    fn super_operand(&mut self, operand: &Operand<'tcx>) {
+        match *operand {
+            Operand::Consume(ref lvalue) => {
+                self.visit_lvalue(lvalue, LvalueContext::Consume);
+            }
+            Operand::Constant(ref constant) => {
+                self.visit_constant(constant);
+            }
+        }
+    }
+
+    fn super_lvalue(&mut self, lvalue: &Lvalue<'tcx>, _context: LvalueContext) {
+        match *lvalue {
+            Lvalue::Var(_) |
+            Lvalue::Temp(_) |
+            Lvalue::Arg(_) |
+            Lvalue::Static(_) |
+            Lvalue::ReturnPointer => {
+            }
+            Lvalue::Projection(ref proj) => {
+                self.visit_lvalue(&proj.base, LvalueContext::Projection);
+            }
+        }
+    }
+
+    fn super_branch(&mut self, _source: BasicBlock, _target: BasicBlock) {
+    }
+
+    fn super_constant(&mut self, _constant: &Constant<'tcx>) {
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum LvalueContext {
+    // Appears as LHS of an assignment or as dest of a call
+    Store,
+
+    // Being dropped
+    Drop,
+
+    // Being inspected in some way, like loading a len
+    Inspect,
+
+    // Being borrowed
+    Borrow { region: Region, kind: BorrowKind },
+
+    // Being sliced -- this should be same as being borrowed, probably
+    Slice { from_start: usize, from_end: usize },
+
+    // Used as base for another lvalue, e.g. `x` in `x.y`
+    Projection,
+
+    // Consumed as part of an operand
+    Consume,
+}