7 files changed, 36 insertions, 23 deletions
diff --git a/compiler/rustc_codegen_gcc/src/abi.rs b/compiler/rustc_codegen_gcc/src/abi.rs
index 2c796d0f69e..0ed3e1fbe93 100644
--- a/compiler/rustc_codegen_gcc/src/abi.rs
+++ b/compiler/rustc_codegen_gcc/src/abi.rs
@@ -1,6 +1,6 @@
 use gccjit::{ToLValue, ToRValue, Type};
 use rustc_codegen_ssa::traits::{AbiBuilderMethods, BaseTypeMethods};
-use rustc_data_structures::stable_set::FxHashSet;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::bug;
 use rustc_middle::ty::Ty;
 use rustc_target::abi::call::{CastTarget, FnAbi, PassMode, Reg, RegKind};
diff --git a/compiler/rustc_codegen_gcc/src/allocator.rs b/compiler/rustc_codegen_gcc/src/allocator.rs
index c761e5aabd1..58efb81e800 100644
--- a/compiler/rustc_codegen_gcc/src/allocator.rs
+++ b/compiler/rustc_codegen_gcc/src/allocator.rs
@@ -117,7 +117,7 @@ pub(crate) unsafe fn codegen(tcx: TyCtxt<'_>, mods: &mut GccContext, _module_nam
 
     let name = OomStrategy::SYMBOL.to_string();
     let global = context.new_global(None, GlobalKind::Exported, i8, name);
-    let value = tcx.sess.opts.debugging_opts.oom.should_panic();
+    let value = tcx.sess.opts.unstable_opts.oom.should_panic();
     let value = context.new_rvalue_from_int(i8, value as i32);
     global.global_set_initializer_rvalue(value);
 }
diff --git a/compiler/rustc_codegen_gcc/src/base.rs b/compiler/rustc_codegen_gcc/src/base.rs
index e4ecbd46f0c..8f9f6f98faf 100644
--- a/compiler/rustc_codegen_gcc/src/base.rs
+++ b/compiler/rustc_codegen_gcc/src/base.rs
@@ -96,7 +96,7 @@ pub fn compile_codegen_unit<'tcx>(tcx: TyCtxt<'tcx>, cgu_name: Symbol, supports_
         // NOTE: Rust relies on LLVM not doing TBAA (https://github.com/rust-lang/unsafe-code-guidelines/issues/292).
         context.add_command_line_option("-fno-strict-aliasing");
 
-        if tcx.sess.opts.debugging_opts.function_sections.unwrap_or(tcx.sess.target.function_sections) {
+        if tcx.sess.opts.unstable_opts.function_sections.unwrap_or(tcx.sess.target.function_sections) {
             context.add_command_line_option("-ffunction-sections");
             context.add_command_line_option("-fdata-sections");
         }
diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs
index 5df59438c90..4d40dd0994d 100644
--- a/compiler/rustc_codegen_gcc/src/builder.rs
+++ b/compiler/rustc_codegen_gcc/src/builder.rs
@@ -30,7 +30,7 @@ use rustc_codegen_ssa::traits::{
     OverflowOp,
     StaticBuilderMethods,
 };
-use rustc_data_structures::stable_set::FxHashSet;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
 use rustc_middle::ty::layout::{FnAbiError, FnAbiOfHelpers, FnAbiRequest, HasParamEnv, HasTyCtxt, LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_span::Span;
diff --git a/compiler/rustc_codegen_gcc/src/common.rs b/compiler/rustc_codegen_gcc/src/common.rs
index ce341406eaf..ccb6cbbc2c8 100644
--- a/compiler/rustc_codegen_gcc/src/common.rs
+++ b/compiler/rustc_codegen_gcc/src/common.rs
@@ -9,10 +9,8 @@ use rustc_codegen_ssa::traits::{
     StaticMethods,
 };
 use rustc_middle::mir::Mutability;
-use rustc_middle::ty::ScalarInt;
 use rustc_middle::ty::layout::{TyAndLayout, LayoutOf};
 use rustc_middle::mir::interpret::{ConstAllocation, GlobalAlloc, Scalar};
-use rustc_span::Symbol;
 use rustc_target::abi::{self, HasDataLayout, Pointer, Size};
 
 use crate::consts::const_alloc_to_gcc;
@@ -125,12 +123,15 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         self.context.new_rvalue_from_double(typ, val)
     }
 
-    fn const_str(&self, s: Symbol) -> (RValue<'gcc>, RValue<'gcc>) {
-        let s_str = s.as_str();
-        let str_global = *self.const_str_cache.borrow_mut().entry(s).or_insert_with(|| {
-            self.global_string(s_str)
-        });
-        let len = s_str.len();
+    fn const_str(&self, s: &str) -> (RValue<'gcc>, RValue<'gcc>) {
+        let str_global = *self
+            .const_str_cache
+            .borrow_mut()
+            .raw_entry_mut()
+            .from_key(s)
+            .or_insert_with(|| (s.to_owned(), self.global_string(s)))
+            .1;
+        let len = s.len();
         let cs = self.const_ptrcast(str_global.get_address(None),
             self.type_ptr_to(self.layout_of(self.tcx.types.str_).gcc_type(self, true)),
         );
@@ -157,13 +158,13 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         None
     }
 
+    fn zst_to_backend(&self, _ty: Type<'gcc>) -> RValue<'gcc> {
+        self.const_undef(self.type_ix(0))
+    }
+
     fn scalar_to_backend(&self, cv: Scalar, layout: abi::Scalar, ty: Type<'gcc>) -> RValue<'gcc> {
         let bitsize = if layout.is_bool() { 1 } else { layout.size(self).bits() };
         match cv {
-            Scalar::Int(ScalarInt::ZST) => {
-                assert_eq!(0, layout.size(self).bytes());
-                self.const_undef(self.type_ix(0))
-            }
             Scalar::Int(int) => {
                 let data = int.assert_bits(layout.size(self));
 
@@ -200,6 +201,11 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
                         GlobalAlloc::Function(fn_instance) => {
                             self.get_fn_addr(fn_instance)
                         },
+                        GlobalAlloc::VTable(ty, trait_ref) => {
+                            let alloc = self.tcx.global_alloc(self.tcx.vtable_allocation((ty, trait_ref))).unwrap_memory();
+                            let init = const_alloc_to_gcc(self, alloc);
+                            self.static_addr_of(init, alloc.inner().align, None)
+                        }
                         GlobalAlloc::Static(def_id) => {
                             assert!(self.tcx.is_static(def_id));
                             self.get_static(def_id).get_address(None)
diff --git a/compiler/rustc_codegen_gcc/src/context.rs b/compiler/rustc_codegen_gcc/src/context.rs
index 44f36cfa4ca..478f6d893dd 100644
--- a/compiler/rustc_codegen_gcc/src/context.rs
+++ b/compiler/rustc_codegen_gcc/src/context.rs
@@ -13,7 +13,7 @@ use rustc_middle::mir::mono::CodegenUnit;
 use rustc_middle::ty::{self, Instance, ParamEnv, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_middle::ty::layout::{FnAbiError, FnAbiOfHelpers, FnAbiRequest, HasParamEnv, HasTyCtxt, LayoutError, TyAndLayout, LayoutOfHelpers};
 use rustc_session::Session;
-use rustc_span::{Span, Symbol};
+use rustc_span::Span;
 use rustc_target::abi::{call::FnAbi, HasDataLayout, PointeeInfo, Size, TargetDataLayout, VariantIdx};
 use rustc_target::spec::{HasTargetSpec, Target, TlsModel};
 
@@ -101,7 +101,7 @@ pub struct CodegenCx<'gcc, 'tcx> {
     pub global_lvalues: RefCell<FxHashMap<RValue<'gcc>, LValue<'gcc>>>,
 
     /// Cache of constant strings,
-    pub const_str_cache: RefCell<FxHashMap<Symbol, LValue<'gcc>>>,
+    pub const_str_cache: RefCell<FxHashMap<String, LValue<'gcc>>>,
 
     /// Cache of globals.
     pub globals: RefCell<FxHashMap<String, RValue<'gcc>>>,
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index 5bfdeb8b93a..c21e0c5a35b 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -6,7 +6,14 @@
  * TODO(antoyo): remove the patches.
  */
 
-#![feature(rustc_private, decl_macro, associated_type_bounds, never_type, trusted_len)]
+#![feature(
+    rustc_private,
+    decl_macro,
+    associated_type_bounds,
+    never_type,
+    trusted_len,
+    hash_raw_entry
+)]
 #![allow(broken_intra_doc_links)]
 #![recursion_limit="256"]
 #![warn(rust_2018_idioms)]
@@ -133,8 +140,8 @@ impl CodegenBackend for GccCodegenBackend {
         )
     }
 
-    fn target_features(&self, sess: &Session) -> Vec<Symbol> {
-        target_features(sess)
+    fn target_features(&self, sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
+        target_features(sess, allow_unstable)
     }
 }
 
@@ -291,12 +298,12 @@ pub fn target_cpu(sess: &Session) -> &str {
     }
 }
 
-pub fn target_features(sess: &Session) -> Vec<Symbol> {
+pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
     supported_target_features(sess)
         .iter()
         .filter_map(
             |&(feature, gate)| {
-                if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None }
+                if sess.is_nightly_build() || allow_unstable || gate.is_none() { Some(feature) } else { None }
             },
         )
         .filter(|_feature| {