Auto merge of #29616 - nagisa:mir-repeat, r=nikomatsakis

r? @nikomatsakis

I went ahead and replaced repeat count with a `Constant`, because it cannot be non-constant to the best of my knowledge.

src/librustc_mir/build/expr/as_rvalue.rs

@@ -44,8 +44,8 @@ impl<'a,'tcx> Builder<'a,'tcx> {
             }
             ExprKind::Repeat { value, count } => {
                 let value_operand = unpack!(block = this.as_operand(block, value));
-                let count_operand = unpack!(block = this.as_operand(block, count));
-                block.and(Rvalue::Repeat(value_operand, count_operand))
+                let count = this.as_constant(count);
+                block.and(Rvalue::Repeat(value_operand, count))
             }
             ExprKind::Borrow { region, borrow_kind, arg } => {
                 let arg_lvalue = unpack!(block = this.as_lvalue(block, arg));

src/librustc_mir/hair/cx/expr.rs

@@ -15,7 +15,6 @@ use hair::cx::Cx;
 use hair::cx::block;
 use hair::cx::to_ref::ToRef;
 use rustc::front::map;
-use rustc::middle::const_eval;
 use rustc::middle::def;
 use rustc::middle::region::CodeExtent;
 use rustc::middle::pat_util;
@@ -80,10 +79,9 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
                 }
             }
 
-            hir::ExprLit(..) => {
-                let value = const_eval::eval_const_expr(cx.tcx, self);
-                ExprKind::Literal { literal: Literal::Value { value: value } }
-            }
+            hir::ExprLit(..) => ExprKind::Literal {
+                literal: cx.const_eval_literal(self)
+            },
 
             hir::ExprBinary(op, ref lhs, ref rhs) => {
                 if cx.tcx.is_method_call(self.id) {
@@ -272,8 +270,17 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
 
             // Now comes the rote stuff:
 
-            hir::ExprRepeat(ref v, ref c) =>
-                ExprKind::Repeat { value: v.to_ref(), count: c.to_ref() },
+            hir::ExprRepeat(ref v, ref c) => ExprKind::Repeat {
+                value: v.to_ref(),
+                count: Expr {
+                    ty: cx.tcx.expr_ty(c),
+                    temp_lifetime: None,
+                    span: c.span,
+                    kind: ExprKind::Literal {
+                        literal: cx.const_eval_literal(c)
+                    }
+                }.to_ref()
+            },
             hir::ExprRet(ref v) =>
                 ExprKind::Return { value: v.to_ref() },
             hir::ExprBreak(label) =>

src/librustc_mir/hair/cx/mod.rs

@@ -18,13 +18,14 @@
 use hair::*;
 use repr::*;
 
-use rustc::middle::const_eval::ConstVal;
+use rustc::middle::const_eval::{self, ConstVal};
 use rustc::middle::def_id::DefId;
 use rustc::middle::infer::InferCtxt;
 use rustc::middle::subst::{Subst, Substs};
 use rustc::middle::ty::{self, Ty};
 use syntax::codemap::Span;
 use syntax::parse::token;
+use rustc_front::hir;
 
 #[derive(Copy, Clone)]
 pub struct Cx<'a, 'tcx: 'a> {
@@ -71,6 +72,10 @@ impl<'a,'tcx:'a> Cx<'a, 'tcx> {
         Literal::Value { value: ConstVal::Bool(false) }
     }
 
+    pub fn const_eval_literal(&mut self, e: &hir::Expr) -> Literal<'tcx> {
+        Literal::Value { value: const_eval::eval_const_expr(self.tcx, e) }
+    }
+
     pub fn partial_eq(&mut self, ty: Ty<'tcx>) -> ItemRef<'tcx> {
         let eq_def_id = self.tcx.lang_items.eq_trait().unwrap();
         self.cmp_method_ref(eq_def_id, "eq", ty)

src/librustc_mir/hair/mod.rs

@@ -210,6 +210,9 @@ pub enum ExprKind<'tcx> {
     },
     Repeat {
         value: ExprRef<'tcx>,
+        // FIXME(#29789): Add a separate hair::Constant<'tcx> so this could be more explicit about
+        // its contained data. Currently this should only contain expression of ExprKind::Literal
+        // kind.
         count: ExprRef<'tcx>,
     },
     Vec {

src/librustc_mir/repr.rs

@@ -569,7 +569,7 @@ pub enum Rvalue<'tcx> {
     Use(Operand<'tcx>),
 
     // [x; 32]
-    Repeat(Operand<'tcx>, Operand<'tcx>),
+    Repeat(Operand<'tcx>, Constant<'tcx>),
 
     // &x or &mut x
     Ref(Region, BorrowKind, Lvalue<'tcx>),

src/librustc_mir/visit.rs

@@ -141,7 +141,7 @@ pub trait Visitor<'tcx> {
 
             Rvalue::Repeat(ref value, ref len) => {
                 self.visit_operand(value);
-                self.visit_operand(len);
+                self.visit_constant(len);
             }
 
             Rvalue::Ref(r, bk, ref path) => {

src/librustc_trans/trans/mir/rvalue.rs

@@ -49,8 +49,14 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
                 unimplemented!()
             }
 
-            mir::Rvalue::Repeat(..) => {
-                unimplemented!()
+            mir::Rvalue::Repeat(ref elem, ref count) => {
+                let elem = self.trans_operand(bcx, elem);
+                let size = self.trans_constant(bcx, count);
+                let base = expr::get_dataptr(bcx, lldest);
+                tvec::iter_vec_raw(bcx, base, elem.ty, size, |b, vref, _| {
+                    build::Store(b, elem.llval, vref);
+                    b
+                })
             }
 
             mir::Rvalue::Aggregate(_, ref operands) => {

src/test/run-pass/mir_trans_array.rs

@@ -0,0 +1,21 @@
+// Copyright 2015 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.
+#![feature(rustc_attrs)]
+
+#[rustc_mir]
+fn into_inner() -> [u64; 1024] {
+    let mut x = 10 + 20;
+    [x; 1024]
+}
+
+fn main(){
+    let x: &[u64] = &[30; 1024];
+    assert_eq!(&into_inner()[..], x);
+}

src/test/run-pass/mir_trans_array_2.rs

@@ -0,0 +1,20 @@
+// Copyright 2015 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.
+#![feature(rustc_attrs)]
+
+#[rustc_mir]
+fn into_inner(x: u64) -> [u64; 1024] {
+    [x; 2*4*8*16]
+}
+
+fn main(){
+    let x: &[u64] = &[42; 1024];
+    assert_eq!(&into_inner(42)[..], x);
+}