context.rs

// Copyright 2013 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 attributes;
use llvm;
use llvm_util;
use rustc::dep_graph::DepGraphSafe;
use rustc::hir;
use debuginfo;
use monomorphize::Instance;
use value::Value;

use monomorphize::partitioning::CodegenUnit;
use type_::Type;
use type_of::PointeeInfo;
use rustc_codegen_ssa::traits::*;
use libc::c_uint;

use rustc_data_structures::base_n;
use rustc_data_structures::small_c_str::SmallCStr;
use rustc::mir::mono::Stats;
use rustc::session::config::{self, DebugInfo};
use rustc::session::Session;
use rustc::ty::layout::{LayoutError, LayoutOf, Size, TyLayout, VariantIdx};
use rustc::ty::{self, Ty, TyCtxt};
use rustc::util::nodemap::FxHashMap;
use rustc_target::spec::{HasTargetSpec, Target};
use rustc_codegen_ssa::callee::resolve_and_get_fn;
use rustc_codegen_ssa::base::wants_msvc_seh;
use callee::get_fn;

use std::ffi::CStr;
use std::cell::{Cell, RefCell};
use std::iter;
use std::str;
use std::sync::Arc;
use syntax::symbol::LocalInternedString;
use abi::Abi;

/// There is one `CodegenCx` per compilation unit. Each one has its own LLVM
/// `llvm::Context` so that several compilation units may be optimized in parallel.
/// All other LLVM data structures in the `CodegenCx` are tied to that `llvm::Context`.
pub struct CodegenCx<'ll, 'tcx: 'll> {
    pub tcx: TyCtxt<'ll, 'tcx, 'tcx>,
    pub check_overflow: bool,
    pub use_dll_storage_attrs: bool,
    pub tls_model: llvm::ThreadLocalMode,

    pub llmod: &'ll llvm::Module,
    pub llcx: &'ll llvm::Context,
    pub stats: RefCell<Stats>,
    pub codegen_unit: Arc<CodegenUnit<'tcx>>,

    /// Cache instances of monomorphic and polymorphic items
    pub instances: RefCell<FxHashMap<Instance<'tcx>, &'ll Value>>,
    /// Cache generated vtables
    pub vtables: RefCell<FxHashMap<(Ty<'tcx>, ty::PolyExistentialTraitRef<'tcx>), &'ll Value>>,
    /// Cache of constant strings,
    pub const_cstr_cache: RefCell<FxHashMap<LocalInternedString, &'ll Value>>,

    /// Reverse-direction for const ptrs cast from globals.
    /// Key is a Value holding a *T,
    /// Val is a Value holding a *[T].
    ///
    /// Needed because LLVM loses pointer->pointee association
    /// when we ptrcast, and we have to ptrcast during codegen
    /// of a [T] const because we form a slice, a (*T,usize) pair, not
    /// a pointer to an LLVM array type. Similar for trait objects.
    pub const_unsized: RefCell<FxHashMap<&'ll Value, &'ll Value>>,

    /// Cache of emitted const globals (value -> global)
    pub const_globals: RefCell<FxHashMap<&'ll Value, &'ll Value>>,

    /// List of globals for static variables which need to be passed to the
    /// LLVM function ReplaceAllUsesWith (RAUW) when codegen is complete.
    /// (We have to make sure we don't invalidate any Values referring
    /// to constants.)
    pub statics_to_rauw: RefCell<Vec<(&'ll Value, &'ll Value)>>,

    /// Statics that will be placed in the llvm.used variable
    /// See http://llvm.org/docs/LangRef.html#the-llvm-used-global-variable for details
    pub used_statics: RefCell<Vec<&'ll Value>>,

    pub lltypes: RefCell<FxHashMap<(Ty<'tcx>, Option<VariantIdx>), &'ll Type>>,
    pub scalar_lltypes: RefCell<FxHashMap<Ty<'tcx>, &'ll Type>>,
    pub pointee_infos: RefCell<FxHashMap<(Ty<'tcx>, Size), Option<PointeeInfo>>>,
    pub isize_ty: &'ll Type,

    pub dbg_cx: Option<debuginfo::CrateDebugContext<'ll, 'tcx>>,

    eh_personality: Cell<Option<&'ll Value>>,
    eh_unwind_resume: Cell<Option<&'ll Value>>,
    pub rust_try_fn: Cell<Option<&'ll Value>>,

    intrinsics: RefCell<FxHashMap<&'static str, &'ll Value>>,

    /// A counter that is used for generating local symbol names
    local_gen_sym_counter: Cell<usize>,
}

impl<'ll, 'tcx> DepGraphSafe for CodegenCx<'ll, 'tcx> {}

pub fn get_reloc_model(sess: &Session) -> llvm::RelocMode {
    let reloc_model_arg = match sess.opts.cg.relocation_model {
        Some(ref s) => &s[..],
        None => &sess.target.target.options.relocation_model[..],
    };

    match ::back::write::RELOC_MODEL_ARGS.iter().find(
        |&&arg| arg.0 == reloc_model_arg) {
        Some(x) => x.1,
        _ => {
            sess.err(&format!("{:?} is not a valid relocation mode",
                              reloc_model_arg));
            sess.abort_if_errors();
            bug!();
        }
    }
}

fn get_tls_model(sess: &Session) -> llvm::ThreadLocalMode {
    let tls_model_arg = match sess.opts.debugging_opts.tls_model {
        Some(ref s) => &s[..],
        None => &sess.target.target.options.tls_model[..],
    };

    match ::back::write::TLS_MODEL_ARGS.iter().find(
        |&&arg| arg.0 == tls_model_arg) {
        Some(x) => x.1,
        _ => {
            sess.err(&format!("{:?} is not a valid TLS model",
                              tls_model_arg));
            sess.abort_if_errors();
            bug!();
        }
    }
}

fn is_any_library(sess: &Session) -> bool {
    sess.crate_types.borrow().iter().any(|ty| {
        *ty != config::CrateType::Executable
    })
}

pub fn is_pie_binary(sess: &Session) -> bool {
    !is_any_library(sess) && get_reloc_model(sess) == llvm::RelocMode::PIC
}

pub unsafe fn create_module(
    sess: &Session,
    llcx: &'ll llvm::Context,
    mod_name: &str,
) -> &'ll llvm::Module {
    let mod_name = SmallCStr::new(mod_name);
    let llmod = llvm::LLVMModuleCreateWithNameInContext(mod_name.as_ptr(), llcx);

    // Ensure the data-layout values hardcoded remain the defaults.
    if sess.target.target.options.is_builtin {
        let tm = ::back::write::create_target_machine(sess, false);
        llvm::LLVMRustSetDataLayoutFromTargetMachine(llmod, tm);
        llvm::LLVMRustDisposeTargetMachine(tm);

        let data_layout = llvm::LLVMGetDataLayout(llmod);
        let data_layout = str::from_utf8(CStr::from_ptr(data_layout).to_bytes())
            .ok().expect("got a non-UTF8 data-layout from LLVM");

        // Unfortunately LLVM target specs change over time, and right now we
        // don't have proper support to work with any more than one
        // `data_layout` than the one that is in the rust-lang/rust repo. If
        // this compiler is configured against a custom LLVM, we may have a
        // differing data layout, even though we should update our own to use
        // that one.
        //
        // As an interim hack, if CFG_LLVM_ROOT is not an empty string then we
        // disable this check entirely as we may be configured with something
        // that has a different target layout.
        //
        // Unsure if this will actually cause breakage when rustc is configured
        // as such.
        //
        // FIXME(#34960)
        let cfg_llvm_root = option_env!("CFG_LLVM_ROOT").unwrap_or("");
        let custom_llvm_used = cfg_llvm_root.trim() != "";

        if !custom_llvm_used && sess.target.target.data_layout != data_layout {
            bug!("data-layout for builtin `{}` target, `{}`, \
                  differs from LLVM default, `{}`",
                 sess.target.target.llvm_target,
                 sess.target.target.data_layout,
                 data_layout);
        }
    }

    let data_layout = SmallCStr::new(&sess.target.target.data_layout);
    llvm::LLVMSetDataLayout(llmod, data_layout.as_ptr());

    let llvm_target = SmallCStr::new(&sess.target.target.llvm_target);
    llvm::LLVMRustSetNormalizedTarget(llmod, llvm_target.as_ptr());

    if is_pie_binary(sess) {
        llvm::LLVMRustSetModulePIELevel(llmod);
    }

    // If skipping the PLT is enabled, we need to add some module metadata
    // to ensure intrinsic calls don't use it.
    if !sess.needs_plt() {
        let avoid_plt = "RtLibUseGOT\0".as_ptr() as *const _;
        llvm::LLVMRustAddModuleFlag(llmod, avoid_plt, 1);
    }

    llmod
}

impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
    crate fn new(tcx: TyCtxt<'ll, 'tcx, 'tcx>,
                 codegen_unit: Arc<CodegenUnit<'tcx>>,
                 llvm_module: &'ll ::ModuleLlvm)
                 -> Self {
        // An interesting part of Windows which MSVC forces our hand on (and
        // apparently MinGW didn't) is the usage of `dllimport` and `dllexport`
        // attributes in LLVM IR as well as native dependencies (in C these
        // correspond to `__declspec(dllimport)`).
        //
        // Whenever a dynamic library is built by MSVC it must have its public
        // interface specified by functions tagged with `dllexport` or otherwise
        // they're not available to be linked against. This poses a few problems
        // for the compiler, some of which are somewhat fundamental, but we use
        // the `use_dll_storage_attrs` variable below to attach the `dllexport`
        // attribute to all LLVM functions that are exported e.g., they're
        // already tagged with external linkage). This is suboptimal for a few
        // reasons:
        //
        // * If an object file will never be included in a dynamic library,
        //   there's no need to attach the dllexport attribute. Most object
        //   files in Rust are not destined to become part of a dll as binaries
        //   are statically linked by default.
        // * If the compiler is emitting both an rlib and a dylib, the same
        //   source object file is currently used but with MSVC this may be less
        //   feasible. The compiler may be able to get around this, but it may
        //   involve some invasive changes to deal with this.
        //
        // The flipside of this situation is that whenever you link to a dll and
        // you import a function from it, the import should be tagged with
        // `dllimport`. At this time, however, the compiler does not emit
        // `dllimport` for any declarations other than constants (where it is
        // required), which is again suboptimal for even more reasons!
        //
        // * Calling a function imported from another dll without using
        //   `dllimport` causes the linker/compiler to have extra overhead (one
        //   `jmp` instruction on x86) when calling the function.
        // * The same object file may be used in different circumstances, so a
        //   function may be imported from a dll if the object is linked into a
        //   dll, but it may be just linked against if linked into an rlib.
        // * The compiler has no knowledge about whether native functions should
        //   be tagged dllimport or not.
        //
        // For now the compiler takes the perf hit (I do not have any numbers to
        // this effect) by marking very little as `dllimport` and praying the
        // linker will take care of everything. Fixing this problem will likely
        // require adding a few attributes to Rust itself (feature gated at the
        // start) and then strongly recommending static linkage on MSVC!
        let use_dll_storage_attrs = tcx.sess.target.target.options.is_like_msvc;

        let check_overflow = tcx.sess.overflow_checks();

        let tls_model = get_tls_model(&tcx.sess);

        let (llcx, llmod) = (&*llvm_module.llcx, llvm_module.llmod());

        let dbg_cx = if tcx.sess.opts.debuginfo != DebugInfo::None {
            let dctx = debuginfo::CrateDebugContext::new(llmod);
            debuginfo::metadata::compile_unit_metadata(tcx,
                                                       &codegen_unit.name().as_str(),
                                                       &dctx);
            Some(dctx)
        } else {
            None
        };

        let isize_ty = Type::ix_llcx(llcx, tcx.data_layout.pointer_size.bits());

        CodegenCx {
            tcx,
            check_overflow,
            use_dll_storage_attrs,
            tls_model,
            llmod,
            llcx,
            stats: RefCell::new(Stats::default()),
            codegen_unit,
            instances: Default::default(),
            vtables: Default::default(),
            const_cstr_cache: Default::default(),
            const_unsized: Default::default(),
            const_globals: Default::default(),
            statics_to_rauw: RefCell::new(Vec::new()),
            used_statics: RefCell::new(Vec::new()),
            lltypes: Default::default(),
            scalar_lltypes: Default::default(),
            pointee_infos: Default::default(),
            isize_ty,
            dbg_cx,
            eh_personality: Cell::new(None),
            eh_unwind_resume: Cell::new(None),
            rust_try_fn: Cell::new(None),
            intrinsics: Default::default(),
            local_gen_sym_counter: Cell::new(0),
        }
    }

    crate fn statics_to_rauw(&self) -> &RefCell<Vec<(&'ll Value, &'ll Value)>> {
        &self.statics_to_rauw
    }
}

impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
    fn vtables(&self) -> &RefCell<FxHashMap<(Ty<'tcx>,
                                ty::PolyExistentialTraitRef<'tcx>), &'ll Value>>
    {
        &self.vtables
    }

    fn instances(&self) -> &RefCell<FxHashMap<Instance<'tcx>, &'ll Value>> {
        &self.instances
    }

    fn get_fn(&self, instance: Instance<'tcx>) -> &'ll Value {
        get_fn(self, instance)
    }

    fn get_param(&self, llfn: &'ll Value, index: c_uint) -> &'ll Value {
        llvm::get_param(llfn, index)
    }

    fn eh_personality(&self) -> &'ll Value {
        // The exception handling personality function.
        //
        // If our compilation unit has the `eh_personality` lang item somewhere
        // within it, then we just need to codegen that. Otherwise, we're
        // building an rlib which will depend on some upstream implementation of
        // this function, so we just codegen a generic reference to it. We don't
        // specify any of the types for the function, we just make it a symbol
        // that LLVM can later use.
        //
        // Note that MSVC is a little special here in that we don't use the
        // `eh_personality` lang item at all. Currently LLVM has support for
        // both Dwarf and SEH unwind mechanisms for MSVC targets and uses the
        // *name of the personality function* to decide what kind of unwind side
        // tables/landing pads to emit. It looks like Dwarf is used by default,
        // injecting a dependency on the `_Unwind_Resume` symbol for resuming
        // an "exception", but for MSVC we want to force SEH. This means that we
        // can't actually have the personality function be our standard
        // `rust_eh_personality` function, but rather we wired it up to the
        // CRT's custom personality function, which forces LLVM to consider
        // landing pads as "landing pads for SEH".
        if let Some(llpersonality) = self.eh_personality.get() {
            return llpersonality
        }
        let tcx = self.tcx;
        let llfn = match tcx.lang_items().eh_personality() {
            Some(def_id) if !wants_msvc_seh(self.sess()) => {
                resolve_and_get_fn(self, def_id, tcx.intern_substs(&[]))
            }
            _ => {
                let name = if wants_msvc_seh(self.sess()) {
                    "__CxxFrameHandler3"
                } else {
                    "rust_eh_personality"
                };
                let fty = self.type_variadic_func(&[], self.type_i32());
                self.declare_cfn(name, fty)
            }
        };
        attributes::apply_target_cpu_attr(self, llfn);
        self.eh_personality.set(Some(llfn));
        llfn
    }

    // Returns a Value of the "eh_unwind_resume" lang item if one is defined,
    // otherwise declares it as an external function.
    fn eh_unwind_resume(&self) -> &'ll Value {
        use attributes;
        let unwresume = &self.eh_unwind_resume;
        if let Some(llfn) = unwresume.get() {
            return llfn;
        }

        let tcx = self.tcx;
        assert!(self.sess().target.target.options.custom_unwind_resume);
        if let Some(def_id) = tcx.lang_items().eh_unwind_resume() {
            let llfn = resolve_and_get_fn(self, def_id, tcx.intern_substs(&[]));
            unwresume.set(Some(llfn));
            return llfn;
        }

        let sig = ty::Binder::bind(tcx.mk_fn_sig(
            iter::once(tcx.mk_mut_ptr(tcx.types.u8)),
            tcx.types.never,
            false,
            hir::Unsafety::Unsafe,
            Abi::C
        ));

        let llfn = self.declare_fn("rust_eh_unwind_resume", sig);
        attributes::apply_target_cpu_attr(self, llfn);
        unwresume.set(Some(llfn));
        llfn
    }

    fn sess(&self) -> &Session {
        &self.tcx.sess
    }

    fn check_overflow(&self) -> bool {
        self.check_overflow
    }

    fn stats(&self) -> &RefCell<Stats> {
        &self.stats
    }

    fn consume_stats(self) -> RefCell<Stats> {
        self.stats
    }

    fn codegen_unit(&self) -> &Arc<CodegenUnit<'tcx>> {
        &self.codegen_unit
    }

    fn used_statics(&self) -> &RefCell<Vec<&'ll Value>> {
        &self.used_statics
    }

    fn set_frame_pointer_elimination(&self, llfn: &'ll Value) {
        attributes::set_frame_pointer_elimination(self, llfn)
    }

    fn apply_target_cpu_attr(&self, llfn: &'ll Value) {
        attributes::apply_target_cpu_attr(self, llfn)
    }

    fn closure_env_needs_indirect_debuginfo(&self) -> bool {
        llvm_util::get_major_version() < 6
    }

    fn create_used_variable(&self) {
        let name = const_cstr!("llvm.used");
        let section = const_cstr!("llvm.metadata");
        let array = self.const_array(
            &self.type_ptr_to(self.type_i8()),
            &*self.used_statics.borrow()
        );

        unsafe {
            let g = llvm::LLVMAddGlobal(self.llmod,
                                        self.val_ty(array),
                                        name.as_ptr());
            llvm::LLVMSetInitializer(g, array);
            llvm::LLVMRustSetLinkage(g, llvm::Linkage::AppendingLinkage);
            llvm::LLVMSetSection(g, section.as_ptr());
        }
    }
}

impl CodegenCx<'b, 'tcx> {
    crate fn get_intrinsic(&self, key: &str) -> &'b Value {
        if let Some(v) = self.intrinsics.borrow().get(key).cloned() {
            return v;
        }

        self.declare_intrinsic(key).unwrap_or_else(|| bug!("unknown intrinsic '{}'", key))
    }

    fn declare_intrinsic(
        &self,
        key: &str
    ) -> Option<&'b Value> {
        macro_rules! ifn {
            ($name:expr, fn() -> $ret:expr) => (
                if key == $name {
                    let f = self.declare_cfn($name, self.type_func(&[], $ret));
                    llvm::SetUnnamedAddr(f, false);
                    self.intrinsics.borrow_mut().insert($name, f.clone());
                    return Some(f);
                }
            );
            ($name:expr, fn(...) -> $ret:expr) => (
                if key == $name {
                    let f = self.declare_cfn($name, self.type_variadic_func(&[], $ret));
                    llvm::SetUnnamedAddr(f, false);
                    self.intrinsics.borrow_mut().insert($name, f.clone());
                    return Some(f);
                }
            );
            ($name:expr, fn($($arg:expr),*) -> $ret:expr) => (
                if key == $name {
                    let f = self.declare_cfn($name, self.type_func(&[$($arg),*], $ret));
                    llvm::SetUnnamedAddr(f, false);
                    self.intrinsics.borrow_mut().insert($name, f.clone());
                    return Some(f);
                }
            );
        }
        macro_rules! mk_struct {
            ($($field_ty:expr),*) => (self.type_struct( &[$($field_ty),*], false))
        }

        let i8p = self.type_i8p();
        let void = self.type_void();
        let i1 = self.type_i1();
        let t_i8 = self.type_i8();
        let t_i16 = self.type_i16();
        let t_i32 = self.type_i32();
        let t_i64 = self.type_i64();
        let t_i128 = self.type_i128();
        let t_f32 = self.type_f32();
        let t_f64 = self.type_f64();

        let t_v2f32 = self.type_vector(t_f32, 2);
        let t_v4f32 = self.type_vector(t_f32, 4);
        let t_v8f32 = self.type_vector(t_f32, 8);
        let t_v16f32 = self.type_vector(t_f32, 16);

        let t_v2f64 = self.type_vector(t_f64, 2);
        let t_v4f64 = self.type_vector(t_f64, 4);
        let t_v8f64 = self.type_vector(t_f64, 8);

        ifn!("llvm.memset.p0i8.i16", fn(i8p, t_i8, t_i16, t_i32, i1) -> void);
        ifn!("llvm.memset.p0i8.i32", fn(i8p, t_i8, t_i32, t_i32, i1) -> void);
        ifn!("llvm.memset.p0i8.i64", fn(i8p, t_i8, t_i64, t_i32, i1) -> void);

        ifn!("llvm.trap", fn() -> void);
        ifn!("llvm.debugtrap", fn() -> void);
        ifn!("llvm.frameaddress", fn(t_i32) -> i8p);

        ifn!("llvm.powi.f32", fn(t_f32, t_i32) -> t_f32);
        ifn!("llvm.powi.v2f32", fn(t_v2f32, t_i32) -> t_v2f32);
        ifn!("llvm.powi.v4f32", fn(t_v4f32, t_i32) -> t_v4f32);
        ifn!("llvm.powi.v8f32", fn(t_v8f32, t_i32) -> t_v8f32);
        ifn!("llvm.powi.v16f32", fn(t_v16f32, t_i32) -> t_v16f32);
        ifn!("llvm.powi.f64", fn(t_f64, t_i32) -> t_f64);
        ifn!("llvm.powi.v2f64", fn(t_v2f64, t_i32) -> t_v2f64);
        ifn!("llvm.powi.v4f64", fn(t_v4f64, t_i32) -> t_v4f64);
        ifn!("llvm.powi.v8f64", fn(t_v8f64, t_i32) -> t_v8f64);

        ifn!("llvm.pow.f32", fn(t_f32, t_f32) -> t_f32);
        ifn!("llvm.pow.v2f32", fn(t_v2f32, t_v2f32) -> t_v2f32);
        ifn!("llvm.pow.v4f32", fn(t_v4f32, t_v4f32) -> t_v4f32);
        ifn!("llvm.pow.v8f32", fn(t_v8f32, t_v8f32) -> t_v8f32);
        ifn!("llvm.pow.v16f32", fn(t_v16f32, t_v16f32) -> t_v16f32);
        ifn!("llvm.pow.f64", fn(t_f64, t_f64) -> t_f64);
        ifn!("llvm.pow.v2f64", fn(t_v2f64, t_v2f64) -> t_v2f64);
        ifn!("llvm.pow.v4f64", fn(t_v4f64, t_v4f64) -> t_v4f64);
        ifn!("llvm.pow.v8f64", fn(t_v8f64, t_v8f64) -> t_v8f64);

        ifn!("llvm.sqrt.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.sqrt.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.sqrt.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.sqrt.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.sqrt.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.sqrt.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.sqrt.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.sqrt.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.sqrt.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.sin.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.sin.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.sin.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.sin.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.sin.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.sin.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.sin.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.sin.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.sin.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.cos.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.cos.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.cos.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.cos.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.cos.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.cos.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.cos.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.cos.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.cos.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.exp.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.exp.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.exp.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.exp.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.exp.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.exp.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.exp.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.exp.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.exp.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.exp2.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.exp2.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.exp2.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.exp2.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.exp2.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.exp2.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.exp2.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.exp2.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.exp2.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.log.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.log.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.log.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.log.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.log.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.log.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.log.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.log.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.log.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.log10.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.log10.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.log10.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.log10.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.log10.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.log10.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.log10.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.log10.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.log10.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.log2.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.log2.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.log2.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.log2.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.log2.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.log2.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.log2.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.log2.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.log2.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.fma.f32", fn(t_f32, t_f32, t_f32) -> t_f32);
        ifn!("llvm.fma.v2f32", fn(t_v2f32, t_v2f32, t_v2f32) -> t_v2f32);
        ifn!("llvm.fma.v4f32", fn(t_v4f32, t_v4f32, t_v4f32) -> t_v4f32);
        ifn!("llvm.fma.v8f32", fn(t_v8f32, t_v8f32, t_v8f32) -> t_v8f32);
        ifn!("llvm.fma.v16f32", fn(t_v16f32, t_v16f32, t_v16f32) -> t_v16f32);
        ifn!("llvm.fma.f64", fn(t_f64, t_f64, t_f64) -> t_f64);
        ifn!("llvm.fma.v2f64", fn(t_v2f64, t_v2f64, t_v2f64) -> t_v2f64);
        ifn!("llvm.fma.v4f64", fn(t_v4f64, t_v4f64, t_v4f64) -> t_v4f64);
        ifn!("llvm.fma.v8f64", fn(t_v8f64, t_v8f64, t_v8f64) -> t_v8f64);

        ifn!("llvm.fabs.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.fabs.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.fabs.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.fabs.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.fabs.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.fabs.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.fabs.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.fabs.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.fabs.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.floor.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.floor.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.floor.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.floor.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.floor.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.floor.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.floor.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.floor.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.floor.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.ceil.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.ceil.v2f32", fn(t_v2f32) -> t_v2f32);
        ifn!("llvm.ceil.v4f32", fn(t_v4f32) -> t_v4f32);
        ifn!("llvm.ceil.v8f32", fn(t_v8f32) -> t_v8f32);
        ifn!("llvm.ceil.v16f32", fn(t_v16f32) -> t_v16f32);
        ifn!("llvm.ceil.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.ceil.v2f64", fn(t_v2f64) -> t_v2f64);
        ifn!("llvm.ceil.v4f64", fn(t_v4f64) -> t_v4f64);
        ifn!("llvm.ceil.v8f64", fn(t_v8f64) -> t_v8f64);

        ifn!("llvm.trunc.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.trunc.f64", fn(t_f64) -> t_f64);

        ifn!("llvm.copysign.f32", fn(t_f32, t_f32) -> t_f32);
        ifn!("llvm.copysign.f64", fn(t_f64, t_f64) -> t_f64);
        ifn!("llvm.round.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.round.f64", fn(t_f64) -> t_f64);

        ifn!("llvm.rint.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.rint.f64", fn(t_f64) -> t_f64);
        ifn!("llvm.nearbyint.f32", fn(t_f32) -> t_f32);
        ifn!("llvm.nearbyint.f64", fn(t_f64) -> t_f64);

        ifn!("llvm.ctpop.i8", fn(t_i8) -> t_i8);
        ifn!("llvm.ctpop.i16", fn(t_i16) -> t_i16);
        ifn!("llvm.ctpop.i32", fn(t_i32) -> t_i32);
        ifn!("llvm.ctpop.i64", fn(t_i64) -> t_i64);
        ifn!("llvm.ctpop.i128", fn(t_i128) -> t_i128);

        ifn!("llvm.ctlz.i8", fn(t_i8 , i1) -> t_i8);
        ifn!("llvm.ctlz.i16", fn(t_i16, i1) -> t_i16);
        ifn!("llvm.ctlz.i32", fn(t_i32, i1) -> t_i32);
        ifn!("llvm.ctlz.i64", fn(t_i64, i1) -> t_i64);
        ifn!("llvm.ctlz.i128", fn(t_i128, i1) -> t_i128);

        ifn!("llvm.cttz.i8", fn(t_i8 , i1) -> t_i8);
        ifn!("llvm.cttz.i16", fn(t_i16, i1) -> t_i16);
        ifn!("llvm.cttz.i32", fn(t_i32, i1) -> t_i32);
        ifn!("llvm.cttz.i64", fn(t_i64, i1) -> t_i64);
        ifn!("llvm.cttz.i128", fn(t_i128, i1) -> t_i128);

        ifn!("llvm.bswap.i16", fn(t_i16) -> t_i16);
        ifn!("llvm.bswap.i32", fn(t_i32) -> t_i32);
        ifn!("llvm.bswap.i64", fn(t_i64) -> t_i64);
        ifn!("llvm.bswap.i128", fn(t_i128) -> t_i128);

        ifn!("llvm.bitreverse.i8", fn(t_i8) -> t_i8);
        ifn!("llvm.bitreverse.i16", fn(t_i16) -> t_i16);
        ifn!("llvm.bitreverse.i32", fn(t_i32) -> t_i32);
        ifn!("llvm.bitreverse.i64", fn(t_i64) -> t_i64);
        ifn!("llvm.bitreverse.i128", fn(t_i128) -> t_i128);

        ifn!("llvm.fshl.i8", fn(t_i8, t_i8, t_i8) -> t_i8);
        ifn!("llvm.fshl.i16", fn(t_i16, t_i16, t_i16) -> t_i16);
        ifn!("llvm.fshl.i32", fn(t_i32, t_i32, t_i32) -> t_i32);
        ifn!("llvm.fshl.i64", fn(t_i64, t_i64, t_i64) -> t_i64);
        ifn!("llvm.fshl.i128", fn(t_i128, t_i128, t_i128) -> t_i128);

        ifn!("llvm.fshr.i8", fn(t_i8, t_i8, t_i8) -> t_i8);
        ifn!("llvm.fshr.i16", fn(t_i16, t_i16, t_i16) -> t_i16);
        ifn!("llvm.fshr.i32", fn(t_i32, t_i32, t_i32) -> t_i32);
        ifn!("llvm.fshr.i64", fn(t_i64, t_i64, t_i64) -> t_i64);
        ifn!("llvm.fshr.i128", fn(t_i128, t_i128, t_i128) -> t_i128);

        ifn!("llvm.sadd.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
        ifn!("llvm.sadd.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
        ifn!("llvm.sadd.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});
        ifn!("llvm.sadd.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
        ifn!("llvm.sadd.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});

        ifn!("llvm.uadd.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
        ifn!("llvm.uadd.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
        ifn!("llvm.uadd.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});
        ifn!("llvm.uadd.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
        ifn!("llvm.uadd.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});

        ifn!("llvm.ssub.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
        ifn!("llvm.ssub.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
        ifn!("llvm.ssub.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});
        ifn!("llvm.ssub.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
        ifn!("llvm.ssub.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});

        ifn!("llvm.usub.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
        ifn!("llvm.usub.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
        ifn!("llvm.usub.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});
        ifn!("llvm.usub.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
        ifn!("llvm.usub.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});

        ifn!("llvm.smul.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
        ifn!("llvm.smul.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
        ifn!("llvm.smul.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});
        ifn!("llvm.smul.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
        ifn!("llvm.smul.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});

        ifn!("llvm.umul.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
        ifn!("llvm.umul.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
        ifn!("llvm.umul.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});
        ifn!("llvm.umul.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
        ifn!("llvm.umul.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});

        ifn!("llvm.lifetime.start", fn(t_i64,i8p) -> void);
        ifn!("llvm.lifetime.end", fn(t_i64, i8p) -> void);

        ifn!("llvm.expect.i1", fn(i1, i1) -> i1);
        ifn!("llvm.eh.typeid.for", fn(i8p) -> t_i32);
        ifn!("llvm.localescape", fn(...) -> void);
        ifn!("llvm.localrecover", fn(i8p, i8p, t_i32) -> i8p);
        ifn!("llvm.x86.seh.recoverfp", fn(i8p, i8p) -> i8p);

        ifn!("llvm.assume", fn(i1) -> void);
        ifn!("llvm.prefetch", fn(i8p, t_i32, t_i32, t_i32) -> void);

        // variadic intrinsics
        ifn!("llvm.va_start", fn(i8p) -> void);
        ifn!("llvm.va_end", fn(i8p) -> void);
        ifn!("llvm.va_copy", fn(i8p, i8p) -> void);

        if self.sess().opts.debuginfo != DebugInfo::None {
            ifn!("llvm.dbg.declare", fn(self.type_metadata(), self.type_metadata()) -> void);
            ifn!("llvm.dbg.value", fn(self.type_metadata(), t_i64, self.type_metadata()) -> void);
        }
        return None;
    }
}

impl<'b, 'tcx> CodegenCx<'b, 'tcx> {
    /// Generate a new symbol name with the given prefix. This symbol name must
    /// only be used for definitions with `internal` or `private` linkage.
    pub fn generate_local_symbol_name(&self, prefix: &str) -> String {
        let idx = self.local_gen_sym_counter.get();
        self.local_gen_sym_counter.set(idx + 1);
        // Include a '.' character, so there can be no accidental conflicts with
        // user defined names
        let mut name = String::with_capacity(prefix.len() + 6);
        name.push_str(prefix);
        name.push_str(".");
        base_n::push_str(idx as u128, base_n::ALPHANUMERIC_ONLY, &mut name);
        name
    }
}

impl ty::layout::HasDataLayout for CodegenCx<'ll, 'tcx> {
    fn data_layout(&self) -> &ty::layout::TargetDataLayout {
        &self.tcx.data_layout
    }
}

impl HasTargetSpec for CodegenCx<'ll, 'tcx> {
    fn target_spec(&self) -> &Target {
        &self.tcx.sess.target.target
    }
}

impl ty::layout::HasTyCtxt<'tcx> for CodegenCx<'ll, 'tcx> {
    fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx> {
        self.tcx
    }
}

impl LayoutOf for CodegenCx<'ll, 'tcx> {
    type Ty = Ty<'tcx>;
    type TyLayout = TyLayout<'tcx>;

    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
        self.tcx.layout_of(ty::ParamEnv::reveal_all().and(ty))
            .unwrap_or_else(|e| if let LayoutError::SizeOverflow(_) = e {
                self.sess().fatal(&e.to_string())
            } else {
                bug!("failed to get layout for `{}`: {}", ty, e)
            })
    }
}