auto merge of #7452 : dotdash/rust/self_indirection, r=cmr

Currently we pass all "self" arguments by reference, for the pointer
variants this means that we end up with double indirection which causes
a unnecessary performance hit.

The fix itself is pretty straight-forward and just means that "self"
needs to be handled like any other argument, except for by-value "self"
which still needs to be passed by reference. This is because
non-pointer types can't just be stuffed into the environment slot which
is used to pass "self".

What made things tricky is that there was also a bug in the typechecker
where the method map entries are created. For type impls, that stored
the base type instead of the actual self-type in the method map, e.g.
Foo instead of &Foo for &self. That worked with pass-by-reference, but
fails with pass-by-value which needs the real type.

Code that makes use of methods seems to be about 10% faster with this
change. Also, build times are reduced by about 4%.

Fixes #4355, #4402, #5280, #4406 and #7285

Author: bors

src/librustc/middle/trans/asm.rs

@@ -41,7 +41,6 @@ pub fn trans_inline_asm(bcx: block, ia: &ast::inline_asm) -> block {
             callee::trans_arg_expr(bcx,
                                    expr_ty(bcx, out),
                                    ty::ByCopy,
-                                   ast::sty_static,
                                    out,
                                    &mut cleanups,
                                    None,
@@ -57,7 +56,6 @@ pub fn trans_inline_asm(bcx: block, ia: &ast::inline_asm) -> block {
             callee::trans_arg_expr(bcx,
                                    expr_ty(bcx, e),
                                    ty::ByCopy,
-                                   ast::sty_static,
                                    e,
                                    &mut cleanups,
                                    None,
@@ -79,7 +77,6 @@ pub fn trans_inline_asm(bcx: block, ia: &ast::inline_asm) -> block {
             callee::trans_arg_expr(bcx,
                                    expr_ty(bcx, in),
                                    ty::ByCopy,
-                                   ast::sty_static,
                                    in,
                                    &mut cleanups,
                                    None,

src/librustc/middle/trans/base.rs

@@ -1626,18 +1626,11 @@ pub fn create_llargs_for_fn_args(cx: fn_ctxt,
     let _icx = push_ctxt("create_llargs_for_fn_args");
 
     match self_arg {
-      impl_self(tt) => {
+      impl_self(tt, self_mode) => {
         cx.llself = Some(ValSelfData {
             v: cx.llenv,
             t: tt,
-            is_owned: false
-        });
-      }
-      impl_owned_self(tt) => {
-        cx.llself = Some(ValSelfData {
-            v: cx.llenv,
-            t: tt,
-            is_owned: true
+            is_copy: self_mode == ty::ByCopy
         });
       }
       no_self => ()
@@ -1676,12 +1669,18 @@ pub fn copy_args_to_allocas(fcx: fn_ctxt,
 
     match fcx.llself {
         Some(slf) => {
-            let self_val = PointerCast(bcx, slf.v, type_of(bcx.ccx(), slf.t).ptr_to());
-            fcx.llself = Some(ValSelfData {v: self_val, ..slf});
+            let self_val = if slf.is_copy
+                    && datum::appropriate_mode(slf.t).is_by_value() {
+                let tmp = BitCast(bcx, slf.v, type_of(bcx.ccx(), slf.t));
+                let alloc = alloc_ty(bcx, slf.t);
+                Store(bcx, tmp, alloc);
+                alloc
+            } else {
+                PointerCast(bcx, slf.v, type_of(bcx.ccx(), slf.t).ptr_to())
+            };
 
-            if slf.is_owned {
-                add_clean(bcx, slf.v, slf.t);
-            }
+            fcx.llself = Some(ValSelfData {v: self_val, ..slf});
+            add_clean(bcx, self_val, slf.t);
         }
         _ => {}
     }
@@ -1758,7 +1757,7 @@ pub fn tie_up_header_blocks(fcx: fn_ctxt, lltop: BasicBlockRef) {
     }
 }
 
-pub enum self_arg { impl_self(ty::t), impl_owned_self(ty::t), no_self, }
+pub enum self_arg { impl_self(ty::t, ty::SelfMode), no_self, }
 
 // trans_closure: Builds an LLVM function out of a source function.
 // If the function closes over its environment a closure will be

src/librustc/middle/trans/callee.rs

@@ -62,9 +62,9 @@ pub struct FnData {
 pub struct MethodData {
     llfn: ValueRef,
     llself: ValueRef,
+    temp_cleanup: Option<ValueRef>,
     self_ty: ty::t,
     self_mode: ty::SelfMode,
-    explicit_self: ast::explicit_self_
 }
 
 pub enum CalleeData {
@@ -615,10 +615,7 @@ pub fn trans_call_inner(in_cx: block,
                 }
                 Method(d) => {
                     // Weird but true: we pass self in the *environment* slot!
-                    let llself = PointerCast(bcx,
-                                             d.llself,
-                                             Type::opaque_box(ccx).ptr_to());
-                    (d.llfn, llself)
+                    (d.llfn, d.llself)
                 }
                 Closure(d) => {
                     // Closures are represented as (llfn, llclosure) pair:
@@ -647,11 +644,12 @@ pub fn trans_call_inner(in_cx: block,
 
 
         // Now that the arguments have finished evaluating, we need to revoke
-        // the cleanup for the self argument, if it exists
+        // the cleanup for the self argument
         match callee.data {
-            Method(d) if d.self_mode == ty::ByCopy ||
-                         d.explicit_self == ast::sty_value => {
-                revoke_clean(bcx, d.llself);
+            Method(d) => {
+                for d.temp_cleanup.iter().advance |&v| {
+                    revoke_clean(bcx, v);
+                }
             }
             _ => {}
         }
@@ -772,7 +770,6 @@ pub fn trans_args(cx: block,
                 trans_arg_expr(bcx,
                                arg_tys[i],
                                ty::ByCopy,
-                               ast::sty_static,
                                *arg_expr,
                                &mut temp_cleanups,
                                if i == last { ret_flag } else { None },
@@ -806,18 +803,16 @@ pub enum AutorefArg {
 pub fn trans_arg_expr(bcx: block,
                       formal_arg_ty: ty::t,
                       self_mode: ty::SelfMode,
-                      ex_self: ast::explicit_self_,
                       arg_expr: @ast::expr,
                       temp_cleanups: &mut ~[ValueRef],
                       ret_flag: Option<ValueRef>,
                       autoref_arg: AutorefArg) -> Result {
     let _icx = push_ctxt("trans_arg_expr");
     let ccx = bcx.ccx();
 
-    debug!("trans_arg_expr(formal_arg_ty=(%s), explicit_self=%? self_mode=%?, arg_expr=%s, \
+    debug!("trans_arg_expr(formal_arg_ty=(%s), self_mode=%?, arg_expr=%s, \
             ret_flag=%?)",
            formal_arg_ty.repr(bcx.tcx()),
-           ex_self,
            self_mode,
            arg_expr.repr(bcx.tcx()),
            ret_flag.map(|v| bcx.val_to_str(*v)));
@@ -877,9 +872,15 @@ pub fn trans_arg_expr(bcx: block,
                 val = arg_datum.to_ref_llval(bcx);
             }
             DontAutorefArg => {
-                match (self_mode, ex_self) {
-                    (ty::ByRef, ast::sty_value) => {
-                        debug!("by value self with type %s, storing to scratch",
+                match self_mode {
+                    ty::ByRef => {
+                        // This assertion should really be valid, but because
+                        // the explicit self code currently passes by-ref, it
+                        // does not hold.
+                        //
+                        //assert !bcx.ccx().maps.moves_map.contains_key(
+                        //    &arg_expr.id);
+                        debug!("by ref arg with type %s, storing to scratch",
                                bcx.ty_to_str(arg_datum.ty));
                         let scratch = scratch_datum(bcx, arg_datum.ty, false);
 
@@ -896,18 +897,7 @@ pub fn trans_arg_expr(bcx: block,
 
                         val = scratch.to_ref_llval(bcx);
                     }
-                    (ty::ByRef, _) => {
-                        // This assertion should really be valid, but because
-                        // the explicit self code currently passes by-ref, it
-                        // does not hold.
-                        //
-                        //assert !bcx.ccx().maps.moves_map.contains_key(
-                        //    &arg_expr.id);
-                        debug!("by ref arg with type %s",
-                               bcx.ty_to_str(arg_datum.ty));
-                        val = arg_datum.to_ref_llval(bcx);
-                    }
-                    (ty::ByCopy, _) => {
+                    ty::ByCopy => {
                         if ty::type_needs_drop(bcx.tcx(), arg_datum.ty) ||
                                 arg_datum.appropriate_mode().is_by_ref() {
                             debug!("by copy arg with type %s, storing to scratch",
@@ -930,7 +920,7 @@ pub fn trans_arg_expr(bcx: block,
                                 ByRef(_) => val = scratch.val,
                             }
                         } else {
-                            debug!("by copy arg with type %s");
+                            debug!("by copy arg with type %s", bcx.ty_to_str(arg_datum.ty));
                             match arg_datum.mode {
                                 ByRef(_) => val = Load(bcx, arg_datum.val),
                                 ByValue => val = arg_datum.val,
@@ -944,10 +934,6 @@ pub fn trans_arg_expr(bcx: block,
         if formal_arg_ty != arg_datum.ty {
             // this could happen due to e.g. subtyping
             let llformal_arg_ty = type_of::type_of_explicit_arg(ccx, &formal_arg_ty);
-            let llformal_arg_ty = match self_mode {
-                ty::ByRef => llformal_arg_ty.ptr_to(),
-                ty::ByCopy => llformal_arg_ty,
-            };
             debug!("casting actual type (%s) to match formal (%s)",
                    bcx.val_to_str(val), bcx.llty_str(llformal_arg_ty));
             val = PointerCast(bcx, val, llformal_arg_ty);

src/librustc/middle/trans/common.rs

@@ -125,7 +125,7 @@ pub type ExternMap = HashMap<@str, ValueRef>;
 pub struct ValSelfData {
     v: ValueRef,
     t: ty::t,
-    is_owned: bool
+    is_copy: bool,
 }
 
 // Here `self_ty` is the real type of the self parameter to this method. It

src/librustc/middle/trans/glue.rs

@@ -425,12 +425,7 @@ pub fn trans_struct_drop_flag(bcx: block, t: ty::t, v0: ValueRef, dtor_did: ast:
         // just consist of the environment (self)
         assert_eq!(params.len(), 1);
 
-        // Take a reference to the class (because it's using the Drop trait),
-        // do so now.
-        let llval = alloca(bcx, val_ty(v0));
-        Store(bcx, v0, llval);
-
-        let self_arg = PointerCast(bcx, llval, params[0]);
+        let self_arg = PointerCast(bcx, v0, params[0]);
         let args = ~[self_arg];
 
         Call(bcx, dtor_addr, args);
@@ -465,12 +460,7 @@ pub fn trans_struct_drop(mut bcx: block, t: ty::t, v0: ValueRef, dtor_did: ast::
     // just consist of the environment (self)
     assert_eq!(params.len(), 1);
 
-    // Take a reference to the class (because it's using the Drop trait),
-    // do so now.
-    let llval = alloca(bcx, val_ty(v0));
-    Store(bcx, v0, llval);
-
-    let self_arg = PointerCast(bcx, llval, params[0]);
+    let self_arg = PointerCast(bcx, v0, params[0]);
     let args = ~[self_arg];
 
     Call(bcx, dtor_addr, args);

src/librustc/middle/trans/inline.rs

@@ -12,7 +12,7 @@ use core::prelude::*;
 
 use metadata::csearch;
 use middle::astencode;
-use middle::trans::base::{push_ctxt,impl_owned_self, impl_self, no_self};
+use middle::trans::base::{push_ctxt, impl_self, no_self};
 use middle::trans::base::{trans_item, get_item_val, trans_fn};
 use middle::trans::common::*;
 use middle::ty;
@@ -114,8 +114,8 @@ pub fn maybe_instantiate_inline(ccx: @mut CrateContext, fn_id: ast::def_id,
                       debug!("calling inline trans_fn with self_ty %s",
                              ty_to_str(ccx.tcx, self_ty));
                       match mth.explicit_self.node {
-                          ast::sty_value => impl_owned_self(self_ty),
-                          _ => impl_self(self_ty),
+                          ast::sty_value => impl_self(self_ty, ty::ByRef),
+                          _ => impl_self(self_ty, ty::ByCopy),
                       }
                   }
               };