rust/src/librustc_codegen_ssa/common.rs

// Copyright 2018 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.
#![allow(non_camel_case_types, non_snake_case)]

use rustc::ty::{self, Ty, TyCtxt};
use syntax_pos::{DUMMY_SP, Span};

use rustc::hir::def_id::DefId;
use rustc::middle::lang_items::LangItem;
use base;
use traits::*;

use rustc::hir;
use traits::BuilderMethods;

pub fn type_needs_drop<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> bool {
    ty.needs_drop(tcx, ty::ParamEnv::reveal_all())
}

pub fn type_is_sized<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> bool {
    ty.is_sized(tcx.at(DUMMY_SP), ty::ParamEnv::reveal_all())
}

pub fn type_is_freeze<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> bool {
    ty.is_freeze(tcx, ty::ParamEnv::reveal_all(), DUMMY_SP)
}

pub enum IntPredicate {
    IntEQ,
    IntNE,
    IntUGT,
    IntUGE,
    IntULT,
    IntULE,
    IntSGT,
    IntSGE,
    IntSLT,
    IntSLE
}


#[allow(dead_code)]
pub enum RealPredicate {
    RealPredicateFalse,
    RealOEQ,
    RealOGT,
    RealOGE,
    RealOLT,
    RealOLE,
    RealONE,
    RealORD,
    RealUNO,
    RealUEQ,
    RealUGT,
    RealUGE,
    RealULT,
    RealULE,
    RealUNE,
    RealPredicateTrue
}

pub enum AtomicRmwBinOp {
    AtomicXchg,
    AtomicAdd,
    AtomicSub,
    AtomicAnd,
    AtomicNand,
    AtomicOr,
    AtomicXor,
    AtomicMax,
    AtomicMin,
    AtomicUMax,
    AtomicUMin
}

pub enum AtomicOrdering {
    #[allow(dead_code)]
    NotAtomic,
    Unordered,
    Monotonic,
    // Consume,  // Not specified yet.
    Acquire,
    Release,
    AcquireRelease,
    SequentiallyConsistent,
}

pub enum SynchronizationScope {
    // FIXME: figure out if this variant is needed at all.
    #[allow(dead_code)]
    Other,
    SingleThread,
    CrossThread,
}

#[derive(Copy, Clone, PartialEq, Debug)]
pub enum TypeKind {
    Void,
    Half,
    Float,
    Double,
    X86_FP80,
    FP128,
    PPC_FP128,
    Label,
    Integer,
    Function,
    Struct,
    Array,
    Pointer,
    Vector,
    Metadata,
    X86_MMX,
    Token,
}

// FIXME(mw): Anything that is produced via DepGraph::with_task() must implement
//            the HashStable trait. Normally DepGraph::with_task() calls are
//            hidden behind queries, but CGU creation is a special case in two
//            ways: (1) it's not a query and (2) CGU are output nodes, so their
//            Fingerprints are not actually needed. It remains to be clarified
//            how exactly this case will be handled in the red/green system but
//            for now we content ourselves with providing a no-op HashStable
//            implementation for CGUs.
mod temp_stable_hash_impls {
    use rustc_data_structures::stable_hasher::{StableHasherResult, StableHasher,
                                               HashStable};
    use ModuleCodegen;

    impl<HCX, M> HashStable<HCX> for ModuleCodegen<M> {
        fn hash_stable<W: StableHasherResult>(&self,
                                              _: &mut HCX,
                                              _: &mut StableHasher<W>) {
            // do nothing
        }
    }
}

pub fn langcall(tcx: TyCtxt,
                span: Option<Span>,
                msg: &str,
                li: LangItem)
                -> DefId {
    tcx.lang_items().require(li).unwrap_or_else(|s| {
        let msg = format!("{} {}", msg, s);
        match span {
            Some(span) => tcx.sess.span_fatal(span, &msg[..]),
            None => tcx.sess.fatal(&msg[..]),
        }
    })
}

// To avoid UB from LLVM, these two functions mask RHS with an
// appropriate mask unconditionally (i.e. the fallback behavior for
// all shifts). For 32- and 64-bit types, this matches the semantics
// of Java. (See related discussion on #1877 and #10183.)

pub fn build_unchecked_lshift<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
    bx: &mut Bx,
    lhs: Bx::Value,
    rhs: Bx::Value
) -> Bx::Value {
    let rhs = base::cast_shift_expr_rhs(bx, hir::BinOpKind::Shl, lhs, rhs);
    // #1877, #10183: Ensure that input is always valid
    let rhs = shift_mask_rhs(bx, rhs);
    bx.shl(lhs, rhs)
}

pub fn build_unchecked_rshift<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
    bx: &mut Bx,
    lhs_t: Ty<'tcx>,
    lhs: Bx::Value,
    rhs: Bx::Value
) -> Bx::Value {
    let rhs = base::cast_shift_expr_rhs(bx, hir::BinOpKind::Shr, lhs, rhs);
    // #1877, #10183: Ensure that input is always valid
    let rhs = shift_mask_rhs(bx, rhs);
    let is_signed = lhs_t.is_signed();
    if is_signed {
        bx.ashr(lhs, rhs)
    } else {
        bx.lshr(lhs, rhs)
    }
}

fn shift_mask_rhs<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
    bx: &mut Bx,
    rhs: Bx::Value
) -> Bx::Value {
    let rhs_llty = bx.cx().val_ty(rhs);
    let shift_val = shift_mask_val(bx, rhs_llty, rhs_llty, false);
    bx.and(rhs, shift_val)
}

pub fn shift_mask_val<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
    bx: &mut Bx,
    llty: Bx::Type,
    mask_llty: Bx::Type,
    invert: bool
) -> Bx::Value {
    let kind = bx.cx().type_kind(llty);
    match kind {
        TypeKind::Integer => {
            // i8/u8 can shift by at most 7, i16/u16 by at most 15, etc.
            let val = bx.cx().int_width(llty) - 1;
            if invert {
                bx.cx().const_int(mask_llty, !val as i64)
            } else {
                bx.cx().const_uint(mask_llty, val)
            }
        },
        TypeKind::Vector => {
            let mask = shift_mask_val(
                bx,
                bx.cx().element_type(llty),
                bx.cx().element_type(mask_llty),
                invert
            );
            bx.vector_splat(bx.cx().vector_length(mask_llty), mask)
        },
        _ => bug!("shift_mask_val: expected Integer or Vector, found {:?}", kind),
    }
}