233 lines
8.2 KiB
Rust
233 lines
8.2 KiB
Rust
// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Set and unset common attributes on LLVM values.
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use std::ffi::{CStr, CString};
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use std::rc::Rc;
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use rustc::hir::Unsafety;
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use rustc::hir::def_id::{DefId, LOCAL_CRATE};
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use rustc::session::config::Sanitizer;
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use rustc::ty::TyCtxt;
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use rustc::ty::maps::Providers;
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use rustc_data_structures::fx::FxHashSet;
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use llvm::{self, Attribute, ValueRef};
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use llvm::AttributePlace::Function;
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use llvm_util;
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pub use syntax::attr::{self, InlineAttr};
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use syntax::ast;
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use context::CodegenCx;
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/// Mark LLVM function to use provided inline heuristic.
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#[inline]
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pub fn inline(val: ValueRef, inline: InlineAttr) {
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use self::InlineAttr::*;
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match inline {
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Hint => Attribute::InlineHint.apply_llfn(Function, val),
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Always => Attribute::AlwaysInline.apply_llfn(Function, val),
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Never => Attribute::NoInline.apply_llfn(Function, val),
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None => {
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Attribute::InlineHint.unapply_llfn(Function, val);
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Attribute::AlwaysInline.unapply_llfn(Function, val);
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Attribute::NoInline.unapply_llfn(Function, val);
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},
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};
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}
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/// Tell LLVM to emit or not emit the information necessary to unwind the stack for the function.
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#[inline]
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pub fn emit_uwtable(val: ValueRef, emit: bool) {
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Attribute::UWTable.toggle_llfn(Function, val, emit);
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}
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/// Tell LLVM whether the function can or cannot unwind.
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#[inline]
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pub fn unwind(val: ValueRef, can_unwind: bool) {
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Attribute::NoUnwind.toggle_llfn(Function, val, !can_unwind);
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}
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/// Tell LLVM whether it should optimize function for size.
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#[inline]
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#[allow(dead_code)] // possibly useful function
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pub fn set_optimize_for_size(val: ValueRef, optimize: bool) {
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Attribute::OptimizeForSize.toggle_llfn(Function, val, optimize);
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}
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/// Tell LLVM if this function should be 'naked', i.e. skip the epilogue and prologue.
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#[inline]
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pub fn naked(val: ValueRef, is_naked: bool) {
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Attribute::Naked.toggle_llfn(Function, val, is_naked);
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}
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pub fn set_frame_pointer_elimination(ccx: &CodegenCx, llfn: ValueRef) {
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// FIXME: #11906: Omitting frame pointers breaks retrieving the value of a
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// parameter.
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if ccx.sess().must_not_eliminate_frame_pointers() {
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llvm::AddFunctionAttrStringValue(
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llfn, llvm::AttributePlace::Function,
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cstr("no-frame-pointer-elim\0"), cstr("true\0"));
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}
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}
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pub fn set_probestack(ccx: &CodegenCx, llfn: ValueRef) {
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// Only use stack probes if the target specification indicates that we
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// should be using stack probes
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if !ccx.sess().target.target.options.stack_probes {
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return
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}
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// Currently stack probes seem somewhat incompatible with the address
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// sanitizer. With asan we're already protected from stack overflow anyway
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// so we don't really need stack probes regardless.
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match ccx.sess().opts.debugging_opts.sanitizer {
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Some(Sanitizer::Address) => return,
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_ => {}
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}
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// Flag our internal `__rust_probestack` function as the stack probe symbol.
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// This is defined in the `compiler-builtins` crate for each architecture.
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llvm::AddFunctionAttrStringValue(
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llfn, llvm::AttributePlace::Function,
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cstr("probe-stack\0"), cstr("__rust_probestack\0"));
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}
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/// Composite function which sets LLVM attributes for function depending on its AST (#[attribute])
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/// attributes.
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pub fn from_fn_attrs(ccx: &CodegenCx, llfn: ValueRef, id: DefId) {
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use syntax::attr::*;
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let attrs = ccx.tcx.get_attrs(id);
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inline(llfn, find_inline_attr(Some(ccx.sess().diagnostic()), &attrs));
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set_frame_pointer_elimination(ccx, llfn);
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set_probestack(ccx, llfn);
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for attr in attrs.iter() {
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if attr.check_name("cold") {
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Attribute::Cold.apply_llfn(Function, llfn);
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} else if attr.check_name("naked") {
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naked(llfn, true);
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} else if attr.check_name("allocator") {
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Attribute::NoAlias.apply_llfn(
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llvm::AttributePlace::ReturnValue, llfn);
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} else if attr.check_name("unwind") {
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unwind(llfn, true);
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} else if attr.check_name("rustc_allocator_nounwind") {
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unwind(llfn, false);
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}
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}
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let target_features = ccx.tcx.target_features_enabled(id);
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if !target_features.is_empty() {
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let val = CString::new(target_features.join(",")).unwrap();
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llvm::AddFunctionAttrStringValue(
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llfn, llvm::AttributePlace::Function,
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cstr("target-features\0"), &val);
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}
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}
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fn cstr(s: &'static str) -> &CStr {
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CStr::from_bytes_with_nul(s.as_bytes()).expect("null-terminated string")
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}
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pub fn provide(providers: &mut Providers) {
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providers.target_features_whitelist = |tcx, cnum| {
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assert_eq!(cnum, LOCAL_CRATE);
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Rc::new(llvm_util::target_feature_whitelist(tcx.sess)
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.iter()
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.map(|c| c.to_str().unwrap().to_string())
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.collect())
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};
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providers.target_features_enabled = |tcx, id| {
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let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
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let mut target_features = Vec::new();
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for attr in tcx.get_attrs(id).iter() {
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if !attr.check_name("target_feature") {
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continue
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}
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if let Some(val) = attr.value_str() {
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for feat in val.as_str().split(",").map(|f| f.trim()) {
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if !feat.is_empty() && !feat.contains('\0') {
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target_features.push(feat.to_string());
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}
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}
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let msg = "#[target_feature = \"..\"] is deprecated and will \
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eventually be removed, use \
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#[target_feature(enable = \"..\")] instead";
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tcx.sess.span_warn(attr.span, &msg);
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continue
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}
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if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
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let msg = "#[target_feature(..)] can only be applied to \
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`unsafe` function";
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tcx.sess.span_err(attr.span, msg);
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}
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from_target_feature(tcx, attr, &whitelist, &mut target_features);
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}
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Rc::new(target_features)
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};
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}
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fn from_target_feature(
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tcx: TyCtxt,
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attr: &ast::Attribute,
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whitelist: &FxHashSet<String>,
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target_features: &mut Vec<String>,
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) {
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let list = match attr.meta_item_list() {
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Some(list) => list,
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None => {
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let msg = "#[target_feature] attribute must be of the form \
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#[target_feature(..)]";
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tcx.sess.span_err(attr.span, &msg);
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return
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}
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};
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for item in list {
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if !item.check_name("enable") {
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let msg = "#[target_feature(..)] only accepts sub-keys of `enable` \
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currently";
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tcx.sess.span_err(item.span, &msg);
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continue
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}
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let value = match item.value_str() {
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Some(list) => list,
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None => {
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let msg = "#[target_feature] attribute must be of the form \
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#[target_feature(enable = \"..\")]";
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tcx.sess.span_err(item.span, &msg);
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continue
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}
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};
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let value = value.as_str();
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for feature in value.split(',') {
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if whitelist.contains(feature) {
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target_features.push(format!("+{}", feature));
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continue
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}
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let msg = format!("the feature named `{}` is not valid for \
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this target", feature);
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let mut err = tcx.sess.struct_span_err(item.span, &msg);
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if feature.starts_with("+") {
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let valid = whitelist.contains(&feature[1..]);
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if valid {
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err.help("consider removing the leading `+` in the feature name");
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}
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}
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err.emit();
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}
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}
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}
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