rust/src/librustc/middle/trans/consts.rs

// Copyright 2012 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.

use core::prelude::*;

use back::abi;
use lib::llvm::{llvm, SetLinkage, PrivateLinkage,
                ValueRef, TypeRef, Bool, True, False};
use metadata::csearch;
use middle::const_eval;
use middle::trans::adt;
use middle::trans::base;
use middle::trans::base::get_insn_ctxt;
use middle::trans::common::*;
use middle::trans::consts;
use middle::trans::expr;
use middle::trans::inline;
use middle::trans::machine;
use middle::trans::type_of;
use middle::ty;
use util::ppaux::{Repr, ty_to_str};

use core::libc::c_uint;
use syntax::{ast, ast_util, ast_map};
use util::ppaux::ty_to_str;

pub fn const_lit(cx: @CrateContext, e: @ast::expr, lit: ast::lit)
    -> ValueRef {
    let _icx = cx.insn_ctxt("trans_lit");
    match lit.node {
      ast::lit_int(i, t) => C_integral(T_int_ty(cx, t), i as u64, True),
      ast::lit_uint(u, t) => C_integral(T_uint_ty(cx, t), u, False),
      ast::lit_int_unsuffixed(i) => {
        let lit_int_ty = ty::node_id_to_type(cx.tcx, e.id);
        match ty::get(lit_int_ty).sty {
          ty::ty_int(t) => {
            C_integral(T_int_ty(cx, t), i as u64, True)
          }
          ty::ty_uint(t) => {
            C_integral(T_uint_ty(cx, t), i as u64, False)
          }
          _ => cx.sess.span_bug(lit.span,
                   fmt!("integer literal has type %s (expected int or uint)",
                        ty_to_str(cx.tcx, lit_int_ty)))
        }
      }
      ast::lit_float(fs, t) => C_floating(/*bad*/copy *fs, T_float_ty(cx, t)),
      ast::lit_float_unsuffixed(fs) => {
        let lit_float_ty = ty::node_id_to_type(cx.tcx, e.id);
        match ty::get(lit_float_ty).sty {
          ty::ty_float(t) => {
            C_floating(/*bad*/copy *fs, T_float_ty(cx, t))
          }
          _ => {
            cx.sess.span_bug(lit.span,
                             ~"floating point literal doesn't have the right \
                               type");
          }
        }
      }
      ast::lit_bool(b) => C_bool(b),
      ast::lit_nil => C_nil(),
      ast::lit_str(s) => C_estr_slice(cx, s)
    }
}

pub fn const_ptrcast(cx: @CrateContext, a: ValueRef, t: TypeRef) -> ValueRef {
    unsafe {
        let b = llvm::LLVMConstPointerCast(a, T_ptr(t));
        assert!(cx.const_globals.insert(b as int, a));
        b
    }
}

pub fn const_vec(cx: @CrateContext, e: @ast::expr, es: &[@ast::expr])
    -> (ValueRef, ValueRef, TypeRef) {
    unsafe {
        let vec_ty = ty::expr_ty(cx.tcx, e);
        let unit_ty = ty::sequence_element_type(cx.tcx, vec_ty);
        let llunitty = type_of::type_of(cx, unit_ty);
        let unit_sz = machine::llsize_of(cx, llunitty);
        let sz = llvm::LLVMConstMul(C_uint(cx, es.len()), unit_sz);
        let vs = es.map(|e| const_expr(cx, *e));
        // If the vector contains enums, an LLVM array won't work.
        let v = if vs.any(|vi| val_ty(*vi) != llunitty) {
            C_struct(vs)
        } else {
            C_array(llunitty, vs)
        };
        return (v, sz, llunitty);
    }
}

fn const_addr_of(cx: @CrateContext, cv: ValueRef) -> ValueRef {
    unsafe {
        let gv = do str::as_c_str("const") |name| {
            llvm::LLVMAddGlobal(cx.llmod, val_ty(cv), name)
        };
        llvm::LLVMSetInitializer(gv, cv);
        llvm::LLVMSetGlobalConstant(gv, True);
        SetLinkage(gv, PrivateLinkage);
        gv
    }
}

fn const_deref_ptr(cx: @CrateContext, v: ValueRef) -> ValueRef {
    let v = match cx.const_globals.find(&(v as int)) {
        Some(&v) => v,
        None => v
    };
    unsafe {
        assert!(llvm::LLVMIsGlobalConstant(v) == True);
        llvm::LLVMGetInitializer(v)
    }
}

fn const_deref_newtype(cx: @CrateContext, v: ValueRef, t: ty::t)
    -> ValueRef {
    let repr = adt::represent_type(cx, t);
    adt::const_get_field(cx, repr, v, 0, 0)
}

fn const_deref(cx: @CrateContext, v: ValueRef, t: ty::t, explicit: bool)
    -> (ValueRef, ty::t) {
    match ty::deref(cx.tcx, t, explicit) {
        Some(ref mt) => {
            assert!(mt.mutbl != ast::m_mutbl);
            let dv = match ty::get(t).sty {
                ty::ty_ptr(*) | ty::ty_rptr(*) => {
                     const_deref_ptr(cx, v)
                }
                ty::ty_enum(*) | ty::ty_struct(*) => {
                    const_deref_newtype(cx, v, t)
                }
                _ => {
                    cx.sess.bug(fmt!("Unexpected dereferenceable type %s",
                                     ty_to_str(cx.tcx, t)))
                }
            };
            (dv, mt.ty)
        }
        None => {
            cx.sess.bug(fmt!("Can't dereference const of type %s",
                             ty_to_str(cx.tcx, t)))
        }
    }
}

pub fn get_const_val(cx: @CrateContext, def_id: ast::def_id) -> ValueRef {
    let mut def_id = def_id;
    if !ast_util::is_local(def_id) ||
       !cx.const_values.contains_key(&def_id.node) {
        if !ast_util::is_local(def_id) {
            def_id = inline::maybe_instantiate_inline(cx, def_id, true);
        }
        match *cx.tcx.items.get(&def_id.node) {
            ast_map::node_item(@ast::item {
                node: ast::item_const(_, subexpr), _
            }, _) => {
                trans_const(cx, subexpr, def_id.node);
            }
            _ => cx.tcx.sess.bug(~"expected a const to be an item")
        }
    }
    *cx.const_values.get(&def_id.node)
}

pub fn const_expr(cx: @CrateContext, e: @ast::expr) -> ValueRef {
    let mut llconst = const_expr_unadjusted(cx, e);
    let ety = ty::expr_ty(cx.tcx, e);
    match cx.tcx.adjustments.find(&e.id) {
        None => { }
        Some(&@ty::AutoAddEnv(ty::re_static, ast::BorrowedSigil)) => {
            llconst = C_struct(~[llconst, C_null(T_opaque_box_ptr(cx))])
        }
        Some(&@ty::AutoAddEnv(ref r, ref s)) => {
            cx.sess.span_bug(e.span, fmt!("unexpected static function: \
                                           region %? sigil %?", *r, *s))
        }
        Some(&@ty::AutoDerefRef(ref adj)) => {
            let mut ty = ety;
            let mut maybe_ptr = None;
            for adj.autoderefs.times {
                let (dv, dt) = const_deref(cx, llconst, ty, false);
                maybe_ptr = Some(llconst);
                llconst = dv;
                ty = dt;
            }

            match adj.autoref {
                None => { }
                Some(ref autoref) => {
                    assert!(autoref.region == ty::re_static);
                    assert!(autoref.mutbl != ast::m_mutbl);
                    // Don't copy data to do a deref+ref.
                    let llptr = match maybe_ptr {
                        Some(ptr) => ptr,
                        None => const_addr_of(cx, llconst)
                    };
                    match autoref.kind {
                        ty::AutoPtr => {
                            llconst = llptr;
                        }
                        ty::AutoBorrowVec => {
                            let size = machine::llsize_of(cx,
                                                          val_ty(llconst));
                            assert!(abi::slice_elt_base == 0);
                            assert!(abi::slice_elt_len == 1);
                            llconst = C_struct(~[llptr, size]);
                        }
                        _ => {
                            cx.sess.span_bug(e.span,
                                             fmt!("unimplemented const \
                                                   autoref %?", autoref))
                        }
                    }
                }
            }
        }
    }

    let ety_adjusted = ty::expr_ty_adjusted(cx.tcx, e);
    let llty = type_of::sizing_type_of(cx, ety_adjusted);
    let csize = machine::llsize_of_alloc(cx, val_ty(llconst));
    let tsize = machine::llsize_of_alloc(cx, llty);
    if csize != tsize {
        unsafe {
            // XXX these values could use some context
            llvm::LLVMDumpValue(llconst);
            llvm::LLVMDumpValue(C_undef(llty));
        }
        cx.sess.bug(fmt!("const %s of type %s has size %u instead of %u",
                         e.repr(cx.tcx), ty_to_str(cx.tcx, ety),
                         csize, tsize));
    }
    llconst
}

fn const_expr_unadjusted(cx: @CrateContext, e: @ast::expr) -> ValueRef {
    unsafe {
        let _icx = cx.insn_ctxt("const_expr");
        return match e.node {
          ast::expr_lit(lit) => consts::const_lit(cx, e, *lit),
          ast::expr_binary(b, e1, e2) => {
            let te1 = const_expr(cx, e1);
            let te2 = const_expr(cx, e2);

            let te2 = base::cast_shift_const_rhs(b, te1, te2);

            /* Neither type is bottom, and we expect them to be unified
             * already, so the following is safe. */
            let ty = ty::expr_ty(cx.tcx, e1);
            let is_float = ty::type_is_fp(ty);
            let signed = ty::type_is_signed(ty);
            return match b {
              ast::add   => {
                if is_float { llvm::LLVMConstFAdd(te1, te2) }
                else        { llvm::LLVMConstAdd(te1, te2) }
              }
              ast::subtract => {
                if is_float { llvm::LLVMConstFSub(te1, te2) }
                else        { llvm::LLVMConstSub(te1, te2) }
              }
              ast::mul    => {
                if is_float { llvm::LLVMConstFMul(te1, te2) }
                else        { llvm::LLVMConstMul(te1, te2) }
              }
              ast::div    => {
                if is_float    { llvm::LLVMConstFDiv(te1, te2) }
                else if signed { llvm::LLVMConstSDiv(te1, te2) }
                else           { llvm::LLVMConstUDiv(te1, te2) }
              }
              ast::rem    => {
                if is_float    { llvm::LLVMConstFRem(te1, te2) }
                else if signed { llvm::LLVMConstSRem(te1, te2) }
                else           { llvm::LLVMConstURem(te1, te2) }
              }
              ast::and    |
              ast::or     => cx.sess.span_unimpl(e.span, ~"binop logic"),
              ast::bitxor => llvm::LLVMConstXor(te1, te2),
              ast::bitand => llvm::LLVMConstAnd(te1, te2),
              ast::bitor  => llvm::LLVMConstOr(te1, te2),
              ast::shl    => llvm::LLVMConstShl(te1, te2),
              ast::shr    => {
                if signed { llvm::LLVMConstAShr(te1, te2) }
                else      { llvm::LLVMConstLShr(te1, te2) }
              }
              ast::eq     |
              ast::lt     |
              ast::le     |
              ast::ne     |
              ast::ge     |
              ast::gt     => cx.sess.span_unimpl(e.span, ~"binop comparator")
            }
          }
          ast::expr_unary(u, e) => {
            let te = const_expr(cx, e);
            let ty = ty::expr_ty(cx.tcx, e);
            let is_float = ty::type_is_fp(ty);
            return match u {
              ast::box(_)  |
              ast::uniq(_) |
              ast::deref  => {
                let (dv, _dt) = const_deref(cx, te, ty, true);
                dv
              }
              ast::not    => {
                match ty::get(ty).sty {
                    ty::ty_bool => {
                        // Somewhat questionable, but I believe this is
                        // correct.
                        let te = llvm::LLVMConstTrunc(te, T_i1());
                        let te = llvm::LLVMConstNot(te);
                        llvm::LLVMConstZExt(te, T_bool())
                    }
                    _ => llvm::LLVMConstNot(te),
                }
              }
              ast::neg    => {
                if is_float { llvm::LLVMConstFNeg(te) }
                else        { llvm::LLVMConstNeg(te) }
              }
            }
          }
          ast::expr_field(base, field, _) => {
              let bt = ty::expr_ty_adjusted(cx.tcx, base);
              let brepr = adt::represent_type(cx, bt);
              let bv = const_expr(cx, base);
              do expr::with_field_tys(cx.tcx, bt, None) |discr, field_tys| {
                  let ix = ty::field_idx_strict(cx.tcx, field, field_tys);
                  adt::const_get_field(cx, brepr, bv, discr, ix)
              }
          }

          ast::expr_index(base, index) => {
              let bt = ty::expr_ty_adjusted(cx.tcx, base);
              let bv = const_expr(cx, base);
              let iv = match const_eval::eval_const_expr(cx.tcx, index) {
                  const_eval::const_int(i) => i as u64,
                  const_eval::const_uint(u) => u,
                  _ => cx.sess.span_bug(index.span,
                                        ~"index is not an integer-constant \
                                          expression")
              };
              let (arr, len) = match ty::get(bt).sty {
                  ty::ty_evec(_, vstore) | ty::ty_estr(vstore) =>
                      match vstore {
                      ty::vstore_fixed(u) =>
                          (bv, C_uint(cx, u)),

                      ty::vstore_slice(_) => {
                          let unit_ty = ty::sequence_element_type(cx.tcx, bt);
                          let llunitty = type_of::type_of(cx, unit_ty);
                          let unit_sz = machine::llsize_of(cx, llunitty);

                          (const_deref_ptr(cx, const_get_elt(cx, bv, [0])),
                           llvm::LLVMConstUDiv(const_get_elt(cx, bv, [1]),
                                               unit_sz))
                      },
                      _ => cx.sess.span_bug(base.span,
                                            ~"index-expr base must be \
                                              fixed-size or slice")
                  },
                  _ =>  cx.sess.span_bug(base.span,
                                         ~"index-expr base must be \
                                           a vector or string type")
              };

              let len = llvm::LLVMConstIntGetZExtValue(len) as u64;
              let len = match ty::get(bt).sty {
                  ty::ty_estr(*) => {assert!(len > 0); len - 1},
                  _ => 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");
              }
              const_get_elt(cx, arr, [iv as c_uint])
          }
          ast::expr_cast(base, _) => {
            let ety = ty::expr_ty(cx.tcx, e);
            let llty = type_of::type_of(cx, ety);
            let basety = ty::expr_ty(cx.tcx, base);
            let v = const_expr(cx, base);
            match (expr::cast_type_kind(basety),
                   expr::cast_type_kind(ety)) {

              (expr::cast_integral, expr::cast_integral) => {
                let s = ty::type_is_signed(basety) as Bool;
                llvm::LLVMConstIntCast(v, llty, s)
              }
              (expr::cast_integral, expr::cast_float) => {
                if ty::type_is_signed(basety) {
                    llvm::LLVMConstSIToFP(v, llty)
                } else {
                    llvm::LLVMConstUIToFP(v, llty)
                }
              }
              (expr::cast_float, expr::cast_float) => {
                llvm::LLVMConstFPCast(v, llty)
              }
              (expr::cast_float, expr::cast_integral) => {
                if ty::type_is_signed(ety) { llvm::LLVMConstFPToSI(v, llty) }
                else { llvm::LLVMConstFPToUI(v, llty) }
              }
              (expr::cast_enum, expr::cast_integral) |
              (expr::cast_enum, expr::cast_float)  => {
                let repr = adt::represent_type(cx, basety);
                let iv = C_int(cx, adt::const_get_discrim(cx, repr, v));
                let ety_cast = expr::cast_type_kind(ety);
                match ety_cast {
                    expr::cast_integral => {
                        let s = ty::type_is_signed(ety) as Bool;
                        llvm::LLVMConstIntCast(iv, llty, s)
                    }
                    expr::cast_float => llvm::LLVMConstUIToFP(iv, llty),
                    _ => cx.sess.bug(~"enum cast destination is not \
                                       integral or float")
                }
              }
              (expr::cast_pointer, expr::cast_pointer) => {
                llvm::LLVMConstPointerCast(v, llty)
              }
              (expr::cast_integral, expr::cast_pointer) => {
                llvm::LLVMConstIntToPtr(v, llty)
              }
              _ => {
                cx.sess.impossible_case(e.span,
                                        ~"bad combination of types for cast")
              }
            }
          }
          ast::expr_addr_of(ast::m_imm, sub) => {
              const_addr_of(cx, const_expr(cx, sub))
          }
          ast::expr_tup(ref es) => {
              let ety = ty::expr_ty(cx.tcx, e);
              let repr = adt::represent_type(cx, ety);
              adt::trans_const(cx, repr, 0, es.map(|e| const_expr(cx, *e)))
          }
          ast::expr_struct(_, ref fs, None) => {
              let ety = ty::expr_ty(cx.tcx, e);
              let repr = adt::represent_type(cx, ety);
              do expr::with_field_tys(cx.tcx, ety, Some(e.id))
                  |discr, field_tys| {
                  let cs = field_tys.map(|field_ty| {
                      match fs.find(|f| field_ty.ident == f.node.ident) {
                          Some(ref f) => const_expr(cx, (*f).node.expr),
                          None => {
                              cx.tcx.sess.span_bug(
                                  e.span, ~"missing struct field");
                          }
                      }
                  });
                  adt::trans_const(cx, repr, discr, cs)
              }
          }
          ast::expr_vec(ref es, ast::m_imm) => {
            let (v, _, _) = const_vec(cx, e, *es);
            v
          }
          ast::expr_vstore(sub, ast::expr_vstore_slice) => {
            match sub.node {
              ast::expr_lit(ref lit) => {
                match lit.node {
                  ast::lit_str(*) => { const_expr(cx, sub) }
                  _ => { cx.sess.span_bug(e.span,
                                          ~"bad const-slice lit") }
                }
              }
              ast::expr_vec(ref es, ast::m_imm) => {
                let (cv, sz, llunitty) = const_vec(cx, e, *es);
                let llty = val_ty(cv);
                let gv = do str::as_c_str("const") |name| {
                    llvm::LLVMAddGlobal(cx.llmod, llty, name)
                };
                llvm::LLVMSetInitializer(gv, cv);
                llvm::LLVMSetGlobalConstant(gv, True);
                SetLinkage(gv, PrivateLinkage);
                let p = const_ptrcast(cx, gv, llunitty);
                C_struct(~[p, sz])
              }
              _ => cx.sess.span_bug(e.span,
                                    ~"bad const-slice expr")
            }
          }
          ast::expr_path(pth) => {
            assert!(pth.types.len() == 0);
            match cx.tcx.def_map.find(&e.id) {
                Some(&ast::def_fn(def_id, _purity)) => {
                    if !ast_util::is_local(def_id) {
                        let ty = csearch::get_type(cx.tcx, def_id).ty;
                        base::trans_external_path(cx, def_id, ty)
                    } else {
                        assert!(ast_util::is_local(def_id));
                        base::get_item_val(cx, def_id.node)
                    }
                }
                Some(&ast::def_const(def_id)) => {
                    get_const_val(cx, def_id)
                }
                Some(&ast::def_variant(enum_did, variant_did)) => {
                    let ety = ty::expr_ty(cx.tcx, e);
                    let repr = adt::represent_type(cx, ety);
                    let vinfo = ty::enum_variant_with_id(cx.tcx,
                                                         enum_did,
                                                         variant_did);
                    adt::trans_const(cx, repr, vinfo.disr_val, [])
                }
                Some(&ast::def_struct(_)) => {
                    let ety = ty::expr_ty(cx.tcx, e);
                    let llty = type_of::type_of(cx, ety);
                    C_null(llty)
                }
                _ => {
                    cx.sess.span_bug(e.span, ~"expected a const, fn, \
                                               struct, or variant def")
                }
            }
          }
          ast::expr_call(callee, ref args, _) => {
              match cx.tcx.def_map.find(&callee.id) {
                  Some(&ast::def_struct(_)) => {
                      let ety = ty::expr_ty(cx.tcx, e);
                      let repr = adt::represent_type(cx, ety);
                      adt::trans_const(cx, repr, 0,
                                       args.map(|a| const_expr(cx, *a)))
                  }
                  Some(&ast::def_variant(enum_did, variant_did)) => {
                      let ety = ty::expr_ty(cx.tcx, e);
                      let repr = adt::represent_type(cx, ety);
                      let vinfo = ty::enum_variant_with_id(cx.tcx,
                                                           enum_did,
                                                           variant_did);
                      adt::trans_const(cx, repr, vinfo.disr_val,
                                       args.map(|a| const_expr(cx, *a)))
                  }
                  _ => cx.sess.span_bug(e.span, ~"expected a struct or \
                                                  variant def")
              }
          }
          ast::expr_paren(e) => { return const_expr(cx, e); }
          _ => cx.sess.span_bug(e.span,
                ~"bad constant expression type in consts::const_expr")
        };
    }
}

pub fn trans_const(ccx: @CrateContext, _e: @ast::expr, id: ast::node_id) {
    unsafe {
        let _icx = ccx.insn_ctxt("trans_const");
        let g = base::get_item_val(ccx, id);
        // At this point, get_item_val has already translated the
        // constant's initializer to determine its LLVM type.
        let v = *ccx.const_values.get(&id);
        llvm::LLVMSetInitializer(g, v);
        llvm::LLVMSetGlobalConstant(g, True);
    }
}