Separately gate each target_feature feature

Use an explicit whitelist for what features are actually stable and can be
enabled.

Author: alexcrichton

.gitmodules

@@ -49,7 +49,7 @@
 	url = https://github.com/rust-lang/llvm
 [submodule "src/stdsimd"]
 	path = src/stdsimd
-	url = https://github.com/alexcrichton/stdsimd
+	url = https://github.com/rust-lang-nursery/stdsimd
 [submodule "src/tools/lld"]
 	path = src/tools/lld
 	url = https://github.com/rust-lang/lld.git

src/libcore/lib.rs

@@ -99,6 +99,14 @@
 #![feature(untagged_unions)]
 #![feature(unwind_attributes)]
 
+#![cfg_attr(not(stage0), feature(mmx_target_feature))]
+#![cfg_attr(not(stage0), feature(tbm_target_feature))]
+#![cfg_attr(not(stage0), feature(sse4a_target_feature))]
+#![cfg_attr(not(stage0), feature(arm_target_feature))]
+#![cfg_attr(not(stage0), feature(powerpc_target_feature))]
+#![cfg_attr(not(stage0), feature(mips_target_feature))]
+#![cfg_attr(not(stage0), feature(aarch64_target_feature))]
+
 #![cfg_attr(stage0, feature(target_feature))]
 #![cfg_attr(stage0, feature(cfg_target_feature))]
 

src/librustc/ty/maps/mod.rs

@@ -437,7 +437,7 @@ define_maps! { <'tcx>
         substitute_normalize_and_test_predicates_node((DefId, &'tcx Substs<'tcx>)) -> bool,
 
     [] fn target_features_whitelist:
-        target_features_whitelist_node(CrateNum) -> Lrc<FxHashSet<String>>,
+        target_features_whitelist_node(CrateNum) -> Lrc<FxHashMap<String, Option<String>>>,
 
     // Get an estimate of the size of an InstanceDef based on its MIR for CGU partitioning.
     [] fn instance_def_size_estimate: instance_def_size_estimate_dep_node(ty::InstanceDef<'tcx>)

src/librustc_trans/attributes.rs

@@ -174,12 +174,12 @@ pub fn provide(providers: &mut Providers) {
             // rustdoc needs to be able to document functions that use all the features, so
             // whitelist them all
             Lrc::new(llvm_util::all_known_features()
-                .map(|c| c.to_string())
+                .map(|(a, b)| (a.to_string(), b.map(|s| s.to_string())))
                 .collect())
         } else {
             Lrc::new(llvm_util::target_feature_whitelist(tcx.sess)
                 .iter()
-                .map(|c| c.to_string())
+                .map(|&(a, b)| (a.to_string(), b.map(|s| s.to_string())))
                 .collect())
         }
     };

src/librustc_trans/llvm_util.rs

@@ -15,6 +15,7 @@ use rustc::session::Session;
 use rustc::session::config::PrintRequest;
 use libc::c_int;
 use std::ffi::CString;
+use syntax::feature_gate::UnstableFeatures;
 
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Once;
@@ -82,40 +83,95 @@ unsafe fn configure_llvm(sess: &Session) {
 // to LLVM or the feature detection code will walk past the end of the feature
 // array, leading to crashes.
 
-const ARM_WHITELIST: &'static [&'static str] = &["neon", "v7", "vfp2", "vfp3", "vfp4"];
-
-const AARCH64_WHITELIST: &'static [&'static str] = &["fp", "neon", "sve", "crc", "crypto",
-                                                     "ras", "lse", "rdm", "fp16", "rcpc",
-                                                     "dotprod", "v8.1a", "v8.2a", "v8.3a"];
-
-const X86_WHITELIST: &'static [&'static str] = &["aes", "avx", "avx2", "avx512bw",
-                                                 "avx512cd", "avx512dq", "avx512er",
-                                                 "avx512f", "avx512ifma", "avx512pf",
-                                                 "avx512vbmi", "avx512vl", "avx512vpopcntdq",
-                                                 "bmi1", "bmi2", "fma", "fxsr",
-                                                 "lzcnt", "mmx", "pclmulqdq",
-                                                 "popcnt", "rdrand", "rdseed",
-                                                 "sha",
-                                                 "sse", "sse2", "sse3", "sse4.1",
-                                                 "sse4.2", "sse4a", "ssse3",
-                                                 "tbm", "xsave", "xsavec",
-                                                 "xsaveopt", "xsaves"];
-
-const HEXAGON_WHITELIST: &'static [&'static str] = &["hvx", "hvx-double"];
-
-const POWERPC_WHITELIST: &'static [&'static str] = &["altivec",
-                                                     "power8-altivec", "power9-altivec",
-                                                     "power8-vector", "power9-vector",
-                                                     "vsx"];
-
-const MIPS_WHITELIST: &'static [&'static str] = &["fp64", "msa"];
+const ARM_WHITELIST: &[(&str, Option<&str>)] = &[
+    ("neon", Some("arm_target_feature")),
+    ("v7", Some("arm_target_feature")),
+    ("vfp2", Some("arm_target_feature")),
+    ("vfp3", Some("arm_target_feature")),
+    ("vfp4", Some("arm_target_feature")),
+];
+
+const AARCH64_WHITELIST: &[(&str, Option<&str>)] = &[
+    ("fp", Some("aarch64_target_feature")),
+    ("neon", Some("aarch64_target_feature")),
+    ("sve", Some("aarch64_target_feature")),
+    ("crc", Some("aarch64_target_feature")),
+    ("crypto", Some("aarch64_target_feature")),
+    ("ras", Some("aarch64_target_feature")),
+    ("lse", Some("aarch64_target_feature")),
+    ("rdm", Some("aarch64_target_feature")),
+    ("fp16", Some("aarch64_target_feature")),
+    ("rcpc", Some("aarch64_target_feature")),
+    ("dotprod", Some("aarch64_target_feature")),
+    ("v8.1a", Some("aarch64_target_feature")),
+    ("v8.2a", Some("aarch64_target_feature")),
+    ("v8.3a", Some("aarch64_target_feature")),
+];
+
+const X86_WHITELIST: &[(&str, Option<&str>)] = &[
+    ("aes", None),
+    ("avx", None),
+    ("avx2", None),
+    ("avx512bw", Some("avx512_target_feature")),
+    ("avx512cd", Some("avx512_target_feature")),
+    ("avx512dq", Some("avx512_target_feature")),
+    ("avx512er", Some("avx512_target_feature")),
+    ("avx512f", Some("avx512_target_feature")),
+    ("avx512ifma", Some("avx512_target_feature")),
+    ("avx512pf", Some("avx512_target_feature")),
+    ("avx512vbmi", Some("avx512_target_feature")),
+    ("avx512vl", Some("avx512_target_feature")),
+    ("avx512vpopcntdq", Some("avx512_target_feature")),
+    ("bmi1", None),
+    ("bmi2", None),
+    ("fma", None),
+    ("fxsr", None),
+    ("lzcnt", None),
+    ("mmx", Some("mmx_target_feature")),
+    ("pclmulqdq", None),
+    ("popcnt", None),
+    ("rdrand", None),
+    ("rdseed", None),
+    ("sha", None),
+    ("sse", None),
+    ("sse2", None),
+    ("sse3", None),
+    ("sse4.1", None),
+    ("sse4.2", None),
+    ("sse4a", Some("sse4a_target_feature")),
+    ("ssse3", None),
+    ("tbm", Some("tbm_target_feature")),
+    ("xsave", None),
+    ("xsavec", None),
+    ("xsaveopt", None),
+    ("xsaves", None),
+];
+
+const HEXAGON_WHITELIST: &[(&str, Option<&str>)] = &[
+    ("hvx", Some("hexagon_target_feature")),
+    ("hvx-double", Some("hexagon_target_feature")),
+];
+
+const POWERPC_WHITELIST: &[(&str, Option<&str>)] = &[
+    ("altivec", Some("powerpc_target_feature")),
+    ("power8-altivec", Some("powerpc_target_feature")),
+    ("power9-altivec", Some("powerpc_target_feature")),
+    ("power8-vector", Some("powerpc_target_feature")),
+    ("power9-vector", Some("powerpc_target_feature")),
+    ("vsx", Some("powerpc_target_feature")),
+];
+
+const MIPS_WHITELIST: &[(&str, Option<&str>)] = &[
+    ("fp64", Some("mips_target_feature")),
+    ("msa", Some("mips_target_feature")),
+];
 
 /// When rustdoc is running, provide a list of all known features so that all their respective
 /// primtives may be documented.
 ///
 /// IMPORTANT: If you're adding another whitelist to the above lists, make sure to add it to this
 /// iterator!
-pub fn all_known_features() -> impl Iterator<Item=&'static str> {
+pub fn all_known_features() -> impl Iterator<Item=(&'static str, Option<&'static str>)> {
     ARM_WHITELIST.iter().cloned()
         .chain(AARCH64_WHITELIST.iter().cloned())
         .chain(X86_WHITELIST.iter().cloned())
@@ -144,6 +200,13 @@ pub fn target_features(sess: &Session) -> Vec<Symbol> {
     let target_machine = create_target_machine(sess, true);
     target_feature_whitelist(sess)
         .iter()
+        .filter_map(|&(feature, gate)| {
+            if UnstableFeatures::from_environment().is_nightly_build() || gate.is_none() {
+                Some(feature)
+            } else {
+                None
+            }
+        })
         .filter(|feature| {
             let llvm_feature = to_llvm_feature(sess, feature);
             let cstr = CString::new(llvm_feature).unwrap();
@@ -152,7 +215,9 @@ pub fn target_features(sess: &Session) -> Vec<Symbol> {
         .map(|feature| Symbol::intern(feature)).collect()
 }
 
-pub fn target_feature_whitelist(sess: &Session) -> &'static [&'static str] {
+pub fn target_feature_whitelist(sess: &Session)
+    -> &'static [(&'static str, Option<&'static str>)]
+{
     match &*sess.target.target.arch {
         "arm" => ARM_WHITELIST,
         "aarch64" => AARCH64_WHITELIST,

src/librustc_trans_utils/trans_crate.rs

@@ -44,7 +44,7 @@ use rustc::middle::cstore::EncodedMetadata;
 use rustc::middle::cstore::MetadataLoader;
 use rustc::dep_graph::DepGraph;
 use rustc_back::target::Target;
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxHashMap;
 use rustc_mir::monomorphize::collector;
 use link::{build_link_meta, out_filename};
 
@@ -203,7 +203,7 @@ impl TransCrate for MetadataOnlyTransCrate {
         ::symbol_names::provide(providers);
 
         providers.target_features_whitelist = |_tcx, _cnum| {
-            Lrc::new(FxHashSet()) // Just a dummy
+            Lrc::new(FxHashMap()) // Just a dummy
         };
     }
     fn provide_extern(&self, _providers: &mut Providers) {}

src/librustc_typeck/collect.rs

@@ -37,13 +37,14 @@ use rustc::ty::maps::Providers;
 use rustc::ty::util::IntTypeExt;
 use rustc::ty::util::Discr;
 use rustc::util::captures::Captures;
-use rustc::util::nodemap::{FxHashSet, FxHashMap};
+use rustc::util::nodemap::FxHashMap;
 
 use syntax::{abi, ast};
 use syntax::ast::MetaItemKind;
 use syntax::attr::{InlineAttr, list_contains_name, mark_used};
 use syntax::codemap::Spanned;
 use syntax::symbol::{Symbol, keywords};
+use syntax::feature_gate;
 use syntax_pos::{Span, DUMMY_SP};
 
 use rustc::hir::{self, map as hir_map, TransFnAttrs, TransFnAttrFlags, Unsafety};
@@ -1682,7 +1683,7 @@ fn is_foreign_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 fn from_target_feature(
     tcx: TyCtxt,
     attr: &ast::Attribute,
-    whitelist: &FxHashSet<String>,
+    whitelist: &FxHashMap<String, Option<String>>,
     target_features: &mut Vec<Symbol>,
 ) {
     let list = match attr.meta_item_list() {
@@ -1694,41 +1695,75 @@ fn from_target_feature(
             return
         }
     };
-
+    let rust_features = tcx.features();
     for item in list {
+        // Only `enable = ...` is accepted in the meta item list
         if !item.check_name("enable") {
             let msg = "#[target_feature(..)] only accepts sub-keys of `enable` \
                        currently";
             tcx.sess.span_err(item.span, &msg);
             continue
         }
+
+        // Must be of the form `enable = "..."` ( a string)
         let value = match item.value_str() {
-            Some(list) => list,
+            Some(value) => value,
             None => {
                 let msg = "#[target_feature] attribute must be of the form \
                            #[target_feature(enable = \"..\")]";
                 tcx.sess.span_err(item.span, &msg);
                 continue
             }
         };
-        let value = value.as_str();
-        for feature in value.split(',') {
-            if whitelist.contains(feature) {
-                target_features.push(Symbol::intern(feature));
-                continue
-            }
-
-            let msg = format!("the feature named `{}` is not valid for \
-                               this target", feature);
-            let mut err = tcx.sess.struct_span_err(item.span, &msg);
 
-            if feature.starts_with("+") {
-                let valid = whitelist.contains(&feature[1..]);
-                if valid {
-                    err.help("consider removing the leading `+` in the feature name");
+        // We allow comma separation to enable multiple features
+        for feature in value.as_str().split(',') {
+
+            // Only allow whitelisted features per platform
+            let feature_gate = match whitelist.get(feature) {
+                Some(g) => g,
+                None => {
+                    let msg = format!("the feature named `{}` is not valid for \
+                                       this target", feature);
+                    let mut err = tcx.sess.struct_span_err(item.span, &msg);
+
+                    if feature.starts_with("+") {
+                        let valid = whitelist.contains_key(&feature[1..]);
+                        if valid {
+                            err.help("consider removing the leading `+` in the feature name");
+                        }
+                    }
+                    err.emit();
+                    continue
                 }
+            };
+
+            // Only allow features whose feature gates have been enabled
+            let allowed = match feature_gate.as_ref().map(|s| &**s) {
+                Some("arm_target_feature") => rust_features.arm_target_feature,
+                Some("aarch64_target_feature") => rust_features.aarch64_target_feature,
+                Some("hexagon_target_feature") => rust_features.hexagon_target_feature,
+                Some("powerpc_target_feature") => rust_features.powerpc_target_feature,
+                Some("mips_target_feature") => rust_features.mips_target_feature,
+                Some("avx512_target_feature") => rust_features.avx512_target_feature,
+                Some("mmx_target_feature") => rust_features.mmx_target_feature,
+                Some("sse4a_target_feature") => rust_features.sse4a_target_feature,
+                Some("tbm_target_feature") => rust_features.tbm_target_feature,
+                Some(name) => bug!("unknown target feature gate {}", name),
+                None => true,
+            };
+            if !allowed {
+                feature_gate::emit_feature_err(
+                    &tcx.sess.parse_sess,
+                    feature_gate.as_ref().unwrap(),
+                    item.span,
+                    feature_gate::GateIssue::Language,
+                    &format!("the target feature `{}` is currently unstable",
+                             feature),
+                );
+                continue
             }
-            err.emit();
+            target_features.push(Symbol::intern(feature));
         }
     }
 }
@@ -1835,20 +1870,6 @@ fn trans_fn_attrs<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, id: DefId) -> TransFnAt
                     .emit();
             }
         } else if attr.check_name("target_feature") {
-            // handle deprecated #[target_feature = "..."]
-            if let Some(val) = attr.value_str() {
-                for feat in val.as_str().split(",").map(|f| f.trim()) {
-                    if !feat.is_empty() && !feat.contains('\0') {
-                        trans_fn_attrs.target_features.push(Symbol::intern(feat));
-                    }
-                }
-                let msg = "#[target_feature = \"..\"] is deprecated and will \
-                           eventually be removed, use \
-                           #[target_feature(enable = \"..\")] instead";
-                tcx.sess.span_warn(attr.span, &msg);
-                continue
-            }
-
             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
                 let msg = "#[target_feature(..)] can only be applied to \
                            `unsafe` function";

src/libsyntax/feature_gate.rs

@@ -446,6 +446,17 @@ declare_features! (
 
     // Allows macro invocations in `extern {}` blocks
     (active, macros_in_extern, "1.27.0", Some(49476), None),
+
+    // unstable #[target_feature] directives
+    (active, arm_target_feature, "1.27.0", None, None),
+    (active, aarch64_target_feature, "1.27.0", None, None),
+    (active, hexagon_target_feature, "1.27.0", None, None),
+    (active, powerpc_target_feature, "1.27.0", None, None),
+    (active, mips_target_feature, "1.27.0", None, None),
+    (active, avx512_target_feature, "1.27.0", None, None),
+    (active, mmx_target_feature, "1.27.0", None, None),
+    (active, sse4a_target_feature, "1.27.0", None, None),
+    (active, tbm_target_feature, "1.27.0", None, None),
 );
 
 declare_features! (

src/stdsimd

@@ -11,6 +11,7 @@
 // ignore-emscripten
 
 #![feature(repr_simd, target_feature, cfg_target_feature)]
+#![feature(avx512_target_feature)]
 
 use std::process::{Command, ExitStatus};
 use std::env;