don't go through llvm for const indexing

closes #3170

Author: Oliver Schneider

src/librustc/middle/const_eval.rs

@@ -207,7 +207,9 @@ pub enum const_val {
     const_binary(Rc<Vec<u8>>),
     const_bool(bool),
     Struct(ast::NodeId),
-    Tuple(ast::NodeId)
+    Tuple(ast::NodeId),
+    Array(Vec<P<Expr>>),
+    Repeat(P<Expr>, u64),
 }
 
 pub fn const_expr_to_pat(tcx: &ty::ctxt, expr: &Expr, span: Span) -> P<ast::Pat> {
@@ -294,11 +296,15 @@ pub enum ErrKind {
     NegateOnBinary,
     NegateOnStruct,
     NegateOnTuple,
+    NegateOnArray,
+    NegateOnRepeat,
     NotOnFloat,
     NotOnString,
     NotOnBinary,
     NotOnStruct,
     NotOnTuple,
+    NotOnArray,
+    NotOnRepeat,
 
     NegateWithOverflow(i64),
     AddiWithOverflow(i64, i64),
@@ -318,6 +324,12 @@ pub enum ErrKind {
     ExpectedConstTuple,
     ExpectedConstStruct,
     TupleIndexOutOfBounds,
+    IndexedNonVec,
+    IndexNotNatural,
+    IndexNotInt,
+    IndexOutOfBounds,
+    RepeatCountNotNatural,
+    RepeatCountNotInt,
 
     MiscBinaryOp,
     MiscCatchAll,
@@ -339,11 +351,15 @@ impl ConstEvalErr {
             NegateOnBinary => "negate on binary literal".into_cow(),
             NegateOnStruct => "negate on struct".into_cow(),
             NegateOnTuple => "negate on tuple".into_cow(),
+            NegateOnArray => "negate on array".into_cow(),
+            NegateOnRepeat => "negate on repeat".into_cow(),
             NotOnFloat => "not on float or string".into_cow(),
             NotOnString => "not on float or string".into_cow(),
             NotOnBinary => "not on binary literal".into_cow(),
             NotOnStruct => "not on struct".into_cow(),
             NotOnTuple => "not on tuple".into_cow(),
+            NotOnArray => "not on array".into_cow(),
+            NotOnRepeat => "not on repeat".into_cow(),
 
             NegateWithOverflow(..) => "attempted to negate with overflow".into_cow(),
             AddiWithOverflow(..) => "attempted to add with overflow".into_cow(),
@@ -363,6 +379,12 @@ impl ConstEvalErr {
             ExpectedConstTuple => "expected constant tuple".into_cow(),
             ExpectedConstStruct => "expected constant struct".into_cow(),
             TupleIndexOutOfBounds => "tuple index out of bounds".into_cow(),
+            IndexedNonVec => "indexing is only supported for arrays".into_cow(),
+            IndexNotNatural => "indices must be a natural number".into_cow(),
+            IndexNotInt => "indices must be integers".into_cow(),
+            IndexOutOfBounds => "array index out of bounds".into_cow(),
+            RepeatCountNotNatural => "repeat count must be a natural number".into_cow(),
+            RepeatCountNotInt => "repeat count must be integers".into_cow(),
 
             MiscBinaryOp => "bad operands for binary".into_cow(),
             MiscCatchAll => "unsupported constant expr".into_cow(),
@@ -672,6 +694,8 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
           const_binary(_) => signal!(e, NegateOnBinary),
           const_val::Tuple(_) => signal!(e, NegateOnTuple),
           const_val::Struct(..) => signal!(e, NegateOnStruct),
+          const_val::Array(_) => signal!(e, NegateOnArray),
+          const_val::Repeat(..) => signal!(e, NegateOnRepeat),
         }
       }
       ast::ExprUnary(ast::UnNot, ref inner) => {
@@ -684,6 +708,8 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
           const_binary(_) => signal!(e, NotOnBinary),
           const_val::Tuple(_) => signal!(e, NotOnTuple),
           const_val::Struct(..) => signal!(e, NotOnStruct),
+          const_val::Array(_) => signal!(e, NotOnArray),
+          const_val::Repeat(..) => signal!(e, NotOnRepeat),
         }
       }
       ast::ExprBinary(op, ref a, ref b) => {
@@ -873,6 +899,33 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
       ast::ExprTup(_) => {
         const_val::Tuple(e.id)
       }
+      ast::ExprIndex(ref arr, ref idx) => {
+        let arr = try!(eval_const_expr_partial(tcx, arr, None));
+        let idx = try!(eval_const_expr_partial(tcx, idx, None));
+        let idx = match idx {
+            const_int(i) if i >= 0 => i as u64,
+            const_int(_) => signal!(e, IndexNotNatural),
+            const_uint(i) => i,
+            _ => signal!(e, IndexNotInt),
+        };
+        match arr {
+            const_val::Array(ref v) if idx as usize >= v.len() => signal!(e, IndexOutOfBounds),
+            const_val::Array(v) => try!(eval_const_expr_partial(tcx, &*v[idx as usize], None)),
+            const_val::Repeat(_, n) if idx >= n => signal!(e, IndexOutOfBounds),
+            const_val::Repeat(elem, _) => try!(eval_const_expr_partial(tcx, &*elem, None)),
+            _ => signal!(e, IndexedNonVec),
+        }
+      }
+      ast::ExprVec(ref arr) => const_val::Array(arr.clone()), // FIXME: eval elements?
+      ast::ExprRepeat(ref elem, ref n) => const_val::Repeat(
+        elem.clone(),
+        match try!(eval_const_expr_partial(tcx, &**n, None)) {
+            const_int(i) if i >= 0 => i as u64,
+            const_int(_) => signal!(e, RepeatCountNotNatural),
+            const_uint(i) => i,
+            _ => signal!(e, RepeatCountNotInt),
+        },
+      ),
       ast::ExprStruct(..) => {
         const_val::Struct(e.id)
       }

src/librustc/middle/ty.rs

@@ -6198,7 +6198,9 @@ pub fn eval_repeat_count(tcx: &ctxt, count_expr: &ast::Expr) -> usize {
                 const_eval::const_bool(_) => "boolean",
                 const_eval::const_binary(_) => "binary array",
                 const_eval::Struct(..) => "struct",
-                const_eval::Tuple(_) => "tuple"
+                const_eval::Tuple(_) => "tuple",
+                const_eval::Array(_) => "array",
+                const_eval::Repeat(..) => "repeat",
             };
             span_err!(tcx.sess, count_expr.span, E0306,
                 "expected positive integer for repeat count, found {}",

src/librustc_trans/trans/consts.rs

@@ -34,7 +34,6 @@ use middle::ty::{self, Ty};
 use util::ppaux::{Repr, ty_to_string};
 
 use std::iter::repeat;
-use libc::c_uint;
 use syntax::{ast, ast_util};
 use syntax::parse::token;
 use syntax::ptr::P;
@@ -565,56 +564,6 @@ fn const_expr_unadjusted<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
               })
           }
 
-          ast::ExprIndex(ref base, ref index) => {
-              let (bv, bt) = const_expr(cx, &**base, param_substs);
-              let iv = match const_eval::eval_const_expr_partial(cx.tcx(), &**index, None) {
-                  Ok(const_eval::const_int(i)) => i as u64,
-                  Ok(const_eval::const_uint(u)) => u,
-                  _ => cx.sess().span_bug(index.span,
-                                          "index is not an integer-constant expression")
-              };
-              let (arr, len) = match bt.sty {
-                  ty::ty_vec(_, Some(u)) => (bv, C_uint(cx, u)),
-                  ty::ty_vec(_, None) | ty::ty_str => {
-                      let e1 = const_get_elt(cx, bv, &[0]);
-                      (const_deref_ptr(cx, e1), const_get_elt(cx, bv, &[1]))
-                  }
-                  ty::ty_rptr(_, mt) => match mt.ty.sty {
-                      ty::ty_vec(_, Some(u)) => {
-                          (const_deref_ptr(cx, bv), C_uint(cx, u))
-                      },
-                      _ => cx.sess().span_bug(base.span,
-                                              &format!("index-expr base must be a vector \
-                                                       or string type, found {}",
-                                                      ty_to_string(cx.tcx(), bt)))
-                  },
-                  _ => cx.sess().span_bug(base.span,
-                                          &format!("index-expr base must be a vector \
-                                                   or string type, found {}",
-                                                  ty_to_string(cx.tcx(), bt)))
-              };
-
-              let len = llvm::LLVMConstIntGetZExtValue(len) as u64;
-              let len = match bt.sty {
-                  ty::ty_uniq(ty) | ty::ty_rptr(_, ty::mt{ty, ..}) => match ty.sty {
-                      ty::ty_str => {
-                          assert!(len > 0);
-                          len - 1
-                      }
-                      _ => len
-                  },
-                  _ => len
-              };
-              if iv >= len {
-                  // FIXME #3170: report this earlier on in the const-eval
-                  // pass. Reporting here is a bit late.
-                  cx.sess().span_err(e.span,
-                                     "const index-expr is out of bounds");
-                  C_undef(type_of::type_of(cx, bt).element_type())
-              } else {
-                  const_get_elt(cx, arr, &[iv as c_uint])
-              }
-          }
           ast::ExprCast(ref base, _) => {
             let llty = type_of::type_of(cx, ety);
             let (v, basety) = const_expr(cx, &**base, param_substs);

src/test/run-pass/array_const_index-0.rs

@@ -0,0 +1,14 @@
+// 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.
+
+static a: &'static [int] = &[];
+static b: int = a[1];
+
+fn main() {}

src/test/run-pass/array_const_index-1.rs

@@ -0,0 +1,16 @@
+// 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.
+
+
+fn main() {
+    const arr: [i32; 6] = [42, 43, 44, 45, 46, 47];
+    const idx: usize = 3;
+    const val: i32 = arr[idx];
+}