first half of fix for #1215

doc/rust.texi

@@ -2954,9 +2954,8 @@ analogous to a @code{become} expression in Newsqueak or Alef.}  destroys the
 current function activation frame and replaces it with an activation frame for
 the called function. In other words, @code{be} executes a tail-call. The
 syntactic form of a @code{be} expression is therefore limited to @emph{tail
-position}: its argument must be a @emph{call expression}, and it must be the
-last expression in a block.
-
+position}: its argument must be a @emph{call expression} or a @{trivial cast}
+of a @emph{call expression}, and it must be the last expression in a block.
 An example of a @code{be} expression:
 @example
 fn print_loop(n: int) @{
@@ -2971,6 +2970,7 @@ fn print_loop(n: int) @{
 
 The above example executes in constant space, replacing each frame with a new
 copy of itself.
+
 @end ignore
 
 
@@ -3001,6 +3001,7 @@ execution and destroying the iterator frame.
 @cindex As expression
 @cindex Cast
 @cindex Typecast
+@cindex Trivial cast
 
 Executing an @code{as} expression casts the value on the left-hand side to the
 type on the right-hand side.
@@ -3018,6 +3019,10 @@ fn avg(v: [float]) -> float @{
 @}
 @end example
 
+A cast is a @emph{trivial cast} iff the type of the casted expression and the
+target type are identical after replacing all occurences of @code{int},
+@code{uint}, @code{float} with their machine type equivalents of the
+target architecture in both types.
 
 @node       Ref.Expr.Fail
 @subsection Ref.Expr.Fail

src/comp/middle/check_const.rs

@@ -25,6 +25,7 @@ fn check_item(tcx: ty::ctxt, it: @item, &&s: (), v: visit::vt<()>) {
 fn check_const_expr(tcx: ty::ctxt, ex: @expr, &&s: (), v: visit::vt<()>) {
     visit::visit_expr(ex, s, v);
     alt ex.node {
+      expr_cast(_, _) { }
       expr_lit(_) { }
       expr_binary(_, _, _) { /* subexps covered by visit */ }
       expr_unary(u, _) {

src/comp/middle/trans.rs

@@ -4086,7 +4086,12 @@ fn trans_expr(bcx: @block_ctxt, e: @ast::expr, dest: dest) -> @block_ctxt {
         if !ty::expr_is_lval(tcx, a) { ret trans_expr(bcx, a, dest); }
         else { ret lval_to_dps(bcx, a, dest); }
       }
-      ast::expr_cast(val, _) { ret trans_cast(bcx, val, e.id, dest); }
+      ast::expr_cast(val, _) {
+        alt tcx.cast_map.find(e.id) {
+          some(ty::triv_cast.) { ret trans_expr(bcx, val, dest); }
+          _ { ret trans_cast(bcx, val, e.id, dest); }
+        }
+      }
       ast::expr_anon_obj(anon_obj) {
         ret trans_anon_obj(bcx, e.span, anon_obj, e.id, dest);
       }
@@ -4115,7 +4120,7 @@ fn trans_expr(bcx: @block_ctxt, e: @ast::expr, dest: dest) -> @block_ctxt {
         // that is_call_expr(ex) -- but we don't support that
         // yet
         // FIXME
-        check (ast_util::is_call_expr(ex));
+        check (ast_util::is_tail_call_expr(ex));
         ret trans_be(bcx, ex);
       }
       ast::expr_fail(expr) {
@@ -4448,7 +4453,8 @@ fn trans_ret(bcx: @block_ctxt, e: option::t<@ast::expr>) -> @block_ctxt {
 fn build_return(bcx: @block_ctxt) { Br(bcx, bcx_fcx(bcx).llreturn); }
 
 // fn trans_be(cx: &@block_ctxt, e: &@ast::expr) -> result {
-fn trans_be(cx: @block_ctxt, e: @ast::expr) : ast_util::is_call_expr(e) ->
+fn trans_be(cx: @block_ctxt, e: @ast::expr) :
+ast_util::is_tail_call_expr(e) ->
    @block_ctxt {
     // FIXME: Turn this into a real tail call once
     // calling convention issues are settled
@@ -5178,6 +5184,16 @@ fn trans_tag_variant(cx: @local_ctxt, tag_id: ast::node_id,
 // that does so later on?
 fn trans_const_expr(cx: @crate_ctxt, e: @ast::expr) -> ValueRef {
     alt e.node {
+      ast::expr_cast(e1, _) {
+        alt ccx_tcx(cx).cast_map.find(e.id) {
+          some(ty::triv_cast.) { trans_const_expr(cx, e1) }
+          _ {
+              cx.sess.span_err(e.span,
+                               "non-trivial cast in constant expression");
+              fail;
+            }
+        }
+      }
       ast::expr_lit(lit) { ret trans_crate_lit(cx, *lit); }
       ast::expr_binary(b, e1, e2) {
         let te1 = trans_const_expr(cx, e1);

src/comp/middle/ty.rs

@@ -32,6 +32,7 @@ export ast_constr_to_constr;
 export bind_params_in_type;
 export block_ty;
 export constr;
+export cast_type;
 export constr_general;
 export constr_table;
 export count_ty_params;
@@ -102,6 +103,8 @@ export substitute_type_params;
 export t;
 export tag_variants;
 export tag_variant_with_id;
+export triv_cast;
+export triv_eq_ty;
 export ty_param_substs_opt_and_ty;
 export ty_param_kinds_and_ty;
 export ty_native_fn;
@@ -128,6 +131,7 @@ export ty_param;
 export ty_ptr;
 export ty_rec;
 export ty_tag;
+export ty_to_machine_ty;
 export ty_tup;
 export ty_type;
 export ty_uint;
@@ -198,6 +202,12 @@ type mt = {ty: t, mut: ast::mutability};
 // the types of AST nodes.
 type creader_cache = hashmap<{cnum: int, pos: uint, len: uint}, ty::t>;
 
+tag cast_type {
+    /* cast may be ignored after substituting primitive with machine types
+       since expr already has the right type */
+    triv_cast;
+}
+
 type ctxt =
     //        constr_table fn_constrs,
     // We need the ext_map just for printing the types of tags defined in
@@ -206,6 +216,7 @@ type ctxt =
       sess: session::session,
       def_map: resolve::def_map,
       ext_map: resolve::ext_map,
+      cast_map: hashmap<ast::node_id, cast_type>,
       node_types: node_type_table,
       items: ast_map::map,
       freevars: freevars::freevar_map,
@@ -393,6 +404,7 @@ fn mk_ctxt(s: session::session, dm: resolve::def_map,
           sess: s,
           def_map: dm,
           ext_map: em,
+          cast_map: ast_util::new_node_hash(),
           node_types: ntt,
           items: amap,
           freevars: freevars,
@@ -1481,6 +1493,38 @@ fn eq_raw_ty(&&a: @raw_t, &&b: @raw_t) -> bool {
 fn eq_ty(&&a: t, &&b: t) -> bool { ret a == b; }
 
 
+// Convert type to machine type
+// (i.e. replace uint, int, float with target architecture machine types)
+//
+// FIXME somewhat expensive but this should only be called rarely
+fn ty_to_machine_ty(cx: ctxt, ty: t) -> t {
+    fn sub_fn(cx: ctxt, uint_ty: t, int_ty: t, float_ty: t, in: t) -> t {
+        alt struct(cx, in) {
+          ty_uint. { ret uint_ty; }
+          ty_int. { ret int_ty; }
+          ty_float. { ret float_ty; }
+          _ { ret in; }
+        }
+    }
+
+    let cfg      = cx.sess.get_targ_cfg();
+    let uint_ty  = mk_mach(cx, cfg.uint_type);
+    let int_ty   = mk_mach(cx, cfg.int_type);
+    let float_ty = mk_mach(cx, cfg.float_type);
+    let fold_m   = fm_general(bind sub_fn(cx, uint_ty, int_ty, float_ty, _));
+
+    ret fold_ty(cx, fold_m, ty);
+}
+
+// Two types are trivially equal if they are either
+// equal or if they are equal after substituting all occurences of
+//  machine independent primitive types by their machine type equivalents
+// for the current target architecture
+fn triv_eq_ty(cx: ctxt, &&a: t, &&b: t) -> bool {
+    ret eq_ty(a, b)
+        || eq_ty(ty_to_machine_ty(cx, a), ty_to_machine_ty(cx, b));
+}
+
 // Type lookups
 fn node_id_to_ty_param_substs_opt_and_ty(cx: ctxt, id: ast::node_id) ->
    ty_param_substs_opt_and_ty {

src/comp/middle/typeck.rs

@@ -1848,8 +1848,21 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
       }
       ast::expr_be(e) {
         // FIXME: prove instead of assert
-        assert (ast_util::is_call_expr(e));
+        assert (ast_util::is_tail_call_expr(e));
         check_expr_with(fcx, e, fcx.ret_ty);
+
+        alt e.node {
+          ast::expr_cast(_, _) {
+            alt tcx.cast_map.find(e.id) {
+              option::some(ty::triv_cast.) { }
+              _ { tcx.sess.span_err(expr.span,
+                    "non-trivial cast of tail-call return value");
+                }
+            }
+          }
+          _ { /* regular tail call */ }
+        }
+
         bot = true;
         write::nil_ty(tcx, id);
       }
@@ -2103,15 +2116,21 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
       ast::expr_cast(e, t) {
         bot = check_expr(fcx, e);
         let t_1 = ast_ty_to_ty_crate(fcx.ccx, t);
-        // FIXME: there are more forms of cast to support, eventually.
+        let t_e = expr_ty(tcx, e);
 
-        if !(type_is_scalar(fcx, expr.span, expr_ty(tcx, e)) &&
-                 type_is_scalar(fcx, expr.span, t_1)) {
+        // FIXME there are more forms of cast to support, eventually.
+        if !(   type_is_scalar(fcx, expr.span, t_e)
+             && type_is_scalar(fcx, expr.span, t_1)) {
             tcx.sess.span_err(expr.span,
                               "non-scalar cast: " +
                                   ty_to_str(tcx, expr_ty(tcx, e)) + " as " +
                                   ty_to_str(tcx, t_1));
         }
+
+        // mark as triv_cast for later dropping in trans
+        if ty::triv_eq_ty(tcx, t_1, t_e)
+            { tcx.cast_map.insert(expr.id, ty::triv_cast); }
+
         write::ty_only_fixup(fcx, id, t_1);
       }
       ast::expr_vec(args, mut) {

src/comp/syntax/ast_util.rs

@@ -1,11 +1,18 @@
-import std::{str, option};
+import std::{str, option, int, map};
 import codemap::span;
 import ast::*;
 
 fn respan<copy T>(sp: span, t: T) -> spanned<T> {
     ret {node: t, span: sp};
 }
 
+fn new_node_hash<copy V>() -> map::hashmap<node_id, V> {
+    fn node_id_hash(&&i: node_id) -> uint { ret int::hash(i as int); }
+    fn node_id_eq(&&a: node_id, &&b: node_id) -> bool
+        { ret int::eq(a as int, b as int); }
+    ret map::mk_hashmap(node_id_hash, node_id_eq);
+}
+
 /* assuming that we're not in macro expansion */
 fn mk_sp(lo: uint, hi: uint) -> span {
     ret {lo: lo, hi: hi, expanded_from: codemap::os_none};
@@ -168,6 +175,14 @@ pure fn is_call_expr(e: @expr) -> bool {
     alt e.node { expr_call(_, _, _) { true } _ { false } }
 }
 
+pure fn is_tail_call_expr(e: @expr) -> bool {
+    alt e.node {
+      expr_call(_, _, _) { true }
+      expr_cast(inner_e, _) { is_call_expr(inner_e) }
+      _ { false }
+    }
+}
+
 fn is_constraint_arg(e: @expr) -> bool {
     alt e.node {
       expr_lit(_) { ret true; }

src/comp/syntax/parse/parser.rs

@@ -962,7 +962,7 @@ fn parse_bottom_expr(p: parser) -> @ast::expr {
         let e = parse_expr(p);
 
         // FIXME: Is this the right place for this check?
-        if /*check*/ast_util::is_call_expr(e) {
+        if /*check*/ ast_util::is_tail_call_expr(e) {
             hi = e.span.hi;
             ex = ast::expr_be(e);
         } else { p.fatal("Non-call expression in tail call"); }

src/lib/ctypes.rs

@@ -5,6 +5,7 @@ Definitions useful for C interop
 */
 
 type c_int = i32;
+type c_uint = u32;
 
 type void = int; // Not really the same as C
 type long = int;
@@ -15,8 +16,20 @@ type intptr_t = uint;
 type uintptr_t = uint;
 type uint32_t = u32;
 
-// This *must* match with "import c_float = fXX" in std::math per arch
-type c_float = f64;
+// machine type equivalents of rust int, uint, float
+
+#[cfg(target_arch="x86")]
+type m_int = i32;
+#[cfg(target_arch="x86_64")]
+type m_int = i64;
+
+#[cfg(target_arch="x86")]
+type m_uint = u32;
+#[cfg(target_arch="x86_64")]
+type m_uint = u64;
+
+// This *must* match with "import m_float = fXX" in std::math per arch
+type m_float = f64;
 
 type size_t = uint;
 type ssize_t = int;