generate MIR for statics and constants

This does not generate MIR for associated constants

Author: oli-obk

src/librustc_mir/build/expr/as_temp.rs

@@ -35,13 +35,11 @@ impl<'a,'tcx> Builder<'a,'tcx> {
 
         let expr_ty = expr.ty.clone();
         let temp = this.temp(expr_ty.clone());
-        let temp_lifetime = match expr.temp_lifetime {
-            Some(t) => t,
-            None => {
-                span_bug!(expr.span, "no temp_lifetime for expr");
-            }
-        };
-        this.schedule_drop(expr.span, temp_lifetime, &temp, expr_ty);
+        if let Some(temp_lifetime) = expr.temp_lifetime {
+            this.schedule_drop(expr.span, temp_lifetime, &temp, expr_ty);
+        }
+        // if expression is inside a constant then
+        // there's no temp_lifetime and no need to drop
 
         // Careful here not to cause an infinite cycle. If we always
         // called `into`, then for lvalues like `x.f`, it would

src/librustc_mir/build/mod.rs

@@ -264,6 +264,76 @@ pub fn construct<'a,'tcx>(hir: Cx<'a,'tcx>,
     )
 }
 
+
+///////////////////////////////////////////////////////////////////////////
+/// the main entry point for building MIR for an arbitrary expression
+
+pub fn construct_expr<'a,'tcx>(hir: Cx<'a,'tcx>,
+                          id: ast::NodeId,
+                          span: Span,
+                          expr: &'tcx hir::Expr)
+                          -> (Mir<'tcx>, ScopeAuxiliaryVec) {
+    let tcx = hir.tcx();
+    let cfg = CFG { basic_blocks: vec![] };
+    let ty = tcx.node_id_to_type(id);
+
+    let mut builder = Builder {
+        hir: hir,
+        cfg: cfg,
+        fn_span: span,
+        scopes: vec![],
+        scope_datas: vec![],
+        scope_auxiliary: ScopeAuxiliaryVec { vec: vec![] },
+        loop_scopes: vec![],
+        temp_decls: vec![],
+        var_decls: vec![],
+        var_indices: FnvHashMap(),
+        unit_temp: None,
+        cached_resume_block: None,
+    };
+
+    assert_eq!(builder.cfg.start_new_block(), START_BLOCK);
+    assert_eq!(builder.cfg.start_new_block(), END_BLOCK);
+
+    let call_site_extent = tcx.region_maps.item_extent(id);
+    let _ = builder.in_scope(call_site_extent, START_BLOCK, |builder, call_site_scope_id| {
+        let mut block = START_BLOCK;
+        let expr = builder.hir.mirror(expr);
+        unpack!(block = builder.into(&Lvalue::ReturnPointer, block, expr));
+        builder.cfg.terminate(block, call_site_scope_id, span,
+                              TerminatorKind::Goto { target: END_BLOCK });
+        builder.cfg.terminate(END_BLOCK, call_site_scope_id, span,
+                              TerminatorKind::Return);
+
+        END_BLOCK.unit()
+    });
+
+    assert!(
+        builder.cfg.basic_blocks
+                   .iter()
+                   .enumerate()
+                   .all(|(index, block)| {
+                       if block.terminator.is_none() {
+                           bug!("no terminator on block {:?} in fn {:?}",
+                                index, id)
+                       }
+                       true
+                   }));
+
+    (
+        Mir {
+            basic_blocks: builder.cfg.basic_blocks,
+            scopes: builder.scope_datas,
+            var_decls: builder.var_decls,
+            arg_decls: Vec::new(),
+            temp_decls: builder.temp_decls,
+            return_ty: FnOutput::FnConverging(ty),
+            span: span
+        },
+        builder.scope_auxiliary,
+    )
+}
+
 impl<'a,'tcx> Builder<'a,'tcx> {
     fn args_and_body(&mut self,
                      mut block: BasicBlock,

src/librustc_mir/mir_map.rs

@@ -80,7 +80,7 @@ impl<'a, 'tcx> OuterDump<'a, 'tcx> {
 
 impl<'a, 'tcx> Visitor<'tcx> for OuterDump<'a, 'tcx> {
     fn visit_item(&mut self, item: &'tcx hir::Item) {
-        self.visit_mir(&item.attrs, |c| intravisit::walk_item(c, item));
+        self.visit_mir(&item.attrs, |c| c.visit_item(item));
         intravisit::walk_item(self, item);
     }
 
@@ -150,6 +150,32 @@ impl<'a, 'm, 'tcx> Visitor<'tcx> for InnerDump<'a,'m,'tcx> {
 
         intravisit::walk_fn(self, fk, decl, body, span);
     }
+
+    fn visit_item(&mut self, i: &'tcx hir::Item) {
+        match i.node {
+            hir::ItemConst(_, ref expr) |
+            hir::ItemStatic(_, _, ref expr) => {
+                let param_env = ty::ParameterEnvironment::for_item(self.tcx, i.id);
+                let infcx = infer::new_infer_ctxt(self.tcx,
+                                                  &self.tcx.tables,
+                                                  Some(param_env),
+                                                  ProjectionMode::AnyFinal);
+                let (mir, scope_auxiliary) = build::construct_expr(Cx::new(&infcx),
+                                                                   i.id,
+                                                                   i.span,
+                                                                   expr);
+                pretty::dump_mir(self.tcx,
+                                 "mir_map",
+                                 &0,
+                                 i.id,
+                                 &mir,
+                                 Some(&scope_auxiliary));
+                assert!(self.map.map.insert(i.id, mir).is_none());
+            },
+            _ => {},
+        }
+        intravisit::walk_item(self, i);
+    }
 }
 
 fn build_mir<'a,'tcx:'a>(cx: Cx<'a,'tcx>,

src/test/run-pass/mir_constant.rs

@@ -0,0 +1,24 @@
+// Copyright 2016 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.
+
+// This test does nothing useful yet, it just generates MIR for constants
+
+#![feature(rustc_attrs)]
+
+#[rustc_mir]
+const C: i32 = 5 + 6;
+
+#[rustc_mir]
+const D: i32 = C - 3;
+
+fn main() {
+    assert_eq!(D, 8);
+    assert_eq!(C, 11);
+}