Add 'compiler/rustc_codegen_gcc/' from commit 'afae271d5d3719eeb92c18bc004bb6d1965a5f3f'

git-subtree-dir: compiler/rustc_codegen_gcc
git-subtree-mainline: ae90dcf0207c57c3034f00b07048d63f8b2363c8
git-subtree-split: afae271d5d3719eeb92c18bc004bb6d1965a5f3f

1 files changed, 527 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_gcc/src/consts.rs b/compiler/rustc_codegen_gcc/src/consts.rs
new file mode 100644
index 00000000000..2cdd7fcab8b
--- /dev/null
+++ b/compiler/rustc_codegen_gcc/src/consts.rs
@@ -0,0 +1,527 @@
+use gccjit::{RValue, Type};
+use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods, DerivedTypeMethods, StaticMethods};
+use rustc_hir as hir;
+use rustc_hir::Node;
+use rustc_middle::{bug, span_bug};
+use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
+use rustc_middle::mir::mono::MonoItem;
+use rustc_middle::ty::{self, Instance, Ty};
+use rustc_mir::interpret::{self, Allocation, ErrorHandled, Scalar as InterpScalar, read_target_uint};
+use rustc_span::Span;
+use rustc_span::def_id::DefId;
+use rustc_target::abi::{self, Align, HasDataLayout, LayoutOf, Primitive, Size};
+
+use crate::base;
+use crate::context::CodegenCx;
+use crate::mangled_std_symbols::{ARGC, ARGV, ARGV_INIT_ARRAY};
+use crate::type_of::LayoutGccExt;
+
+impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
+    pub fn const_bitcast(&self, value: RValue<'gcc>, typ: Type<'gcc>) -> RValue<'gcc> {
+        if value.get_type() == self.bool_type.make_pointer() {
+            if let Some(pointee) = typ.get_pointee() {
+                if pointee.is_vector().is_some() {
+                    panic!()
+                }
+            }
+        }
+        self.context.new_bitcast(None, value, typ)
+    }
+}
+
+impl<'gcc, 'tcx> StaticMethods for CodegenCx<'gcc, 'tcx> {
+    fn static_addr_of(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
+        if let Some(global_value) = self.const_globals.borrow().get(&cv) {
+            // TODO
+            /*unsafe {
+                // Upgrade the alignment in cases where the same constant is used with different
+                // alignment requirements
+                let llalign = align.bytes() as u32;
+                if llalign > llvm::LLVMGetAlignment(gv) {
+                    llvm::LLVMSetAlignment(gv, llalign);
+                }
+            }*/
+            return *global_value;
+        }
+        let global_value = self.static_addr_of_mut(cv, align, kind);
+        // TODO
+        /*unsafe {
+            llvm::LLVMSetGlobalConstant(global_value, True);
+        }*/
+        self.const_globals.borrow_mut().insert(cv, global_value);
+        global_value
+    }
+
+    fn codegen_static(&self, def_id: DefId, is_mutable: bool) {
+        let attrs = self.tcx.codegen_fn_attrs(def_id);
+
+        let instance = Instance::mono(self.tcx, def_id);
+        let name = &*self.tcx.symbol_name(instance).name;
+
+        let (value, alloc) =
+            match codegen_static_initializer(&self, def_id) {
+                Ok(value) => value,
+                // Error has already been reported
+                Err(_) => return,
+            };
+
+        let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
+        let global = self.get_static(def_id);
+
+        // boolean SSA values are i1, but they have to be stored in i8 slots,
+        // otherwise some LLVM optimization passes don't work as expected
+        let val_llty = self.val_ty(value);
+        let value =
+            if val_llty == self.type_i1() {
+                //val_llty = self.type_i8();
+                unimplemented!();
+                //llvm::LLVMConstZExt(value, val_llty)
+            }
+            else {
+                value
+            };
+
+        let instance = Instance::mono(self.tcx, def_id);
+        let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
+        let gcc_type = self.layout_of(ty).gcc_type(self, true);
+
+        let global =
+            if val_llty == gcc_type {
+                global
+            }
+            else {
+                // If we created the global with the wrong type,
+                // correct the type.
+                /*let name = llvm::get_value_name(global).to_vec();
+                llvm::set_value_name(global, b"");
+
+                let linkage = llvm::LLVMRustGetLinkage(global);
+                let visibility = llvm::LLVMRustGetVisibility(global);*/
+
+                let new_global = self.get_or_insert_global(&name, val_llty, is_tls, attrs.link_section);
+
+                /*llvm::LLVMRustSetLinkage(new_global, linkage);
+                  llvm::LLVMRustSetVisibility(new_global, visibility);*/
+
+                // To avoid breaking any invariants, we leave around the old
+                // global for the moment; we'll replace all references to it
+                // with the new global later. (See base::codegen_backend.)
+                //self.statics_to_rauw.borrow_mut().push((global, new_global));
+                new_global
+            };
+        // TODO
+        //set_global_alignment(&self, global, self.align_of(ty));
+        //llvm::LLVMSetInitializer(global, value);
+        let value = self.rvalue_as_lvalue(value);
+        let value = value.get_address(None);
+        let dest_typ = global.get_type();
+        let value = self.context.new_cast(None, value, dest_typ);
+
+        // NOTE: do not init the variables related to argc/argv because it seems we cannot
+        // overwrite those variables.
+        // FIXME: correctly support global variable initialization.
+        let skip_init = [
+            ARGV_INIT_ARRAY,
+            ARGC,
+            ARGV,
+        ];
+        if !skip_init.iter().any(|symbol_name| name.starts_with(symbol_name)) {
+            // TODO: switch to set_initializer when libgccjit supports that.
+            let memcpy = self.context.get_builtin_function("memcpy");
+            let dst = self.context.new_cast(None, global, self.type_i8p());
+            let src = self.context.new_cast(None, value, self.type_ptr_to(self.type_void()));
+            let size = self.context.new_rvalue_from_long(self.sizet_type, alloc.size().bytes() as i64);
+            self.global_init_block.add_eval(None, self.context.new_call(None, memcpy, &[dst, src, size]));
+        }
+
+        // As an optimization, all shared statics which do not have interior
+        // mutability are placed into read-only memory.
+        if !is_mutable {
+            if self.type_is_freeze(ty) {
+                // TODO
+                //llvm::LLVMSetGlobalConstant(global, llvm::True);
+            }
+        }
+
+        //debuginfo::create_global_var_metadata(&self, def_id, global);
+
+        if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
+            // Do not allow LLVM to change the alignment of a TLS on macOS.
+            //
+            // By default a global's alignment can be freely increased.
+            // This allows LLVM to generate more performant instructions
+            // e.g., using load-aligned into a SIMD register.
+            //
+            // However, on macOS 10.10 or below, the dynamic linker does not
+            // respect any alignment given on the TLS (radar 24221680).
+            // This will violate the alignment assumption, and causing segfault at runtime.
+            //
+            // This bug is very easy to trigger. In `println!` and `panic!`,
+            // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
+            // which the values would be `mem::replace`d on initialization.
+            // The implementation of `mem::replace` will use SIMD
+            // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
+            // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
+            // which macOS's dyld disregarded and causing crashes
+            // (see issues #51794, #51758, #50867, #48866 and #44056).
+            //
+            // To workaround the bug, we trick LLVM into not increasing
+            // the global's alignment by explicitly assigning a section to it
+            // (equivalent to automatically generating a `#[link_section]` attribute).
+            // See the comment in the `GlobalValue::canIncreaseAlignment()` function
+            // of `lib/IR/Globals.cpp` for why this works.
+            //
+            // When the alignment is not increased, the optimized `mem::replace`
+            // will use load-unaligned instructions instead, and thus avoiding the crash.
+            //
+            // We could remove this hack whenever we decide to drop macOS 10.10 support.
+            if self.tcx.sess.target.options.is_like_osx {
+                // The `inspect` method is okay here because we checked relocations, and
+                // because we are doing this access to inspect the final interpreter state
+                // (not as part of the interpreter execution).
+                //
+                // FIXME: This check requires that the (arbitrary) value of undefined bytes
+                // happens to be zero. Instead, we should only check the value of defined bytes
+                // and set all undefined bytes to zero if this allocation is headed for the
+                // BSS.
+                /*let all_bytes_are_zero = alloc.relocations().is_empty()
+                    && alloc
+                        .inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len())
+                        .iter()
+                        .all(|&byte| byte == 0);
+
+                let sect_name = if all_bytes_are_zero {
+                    CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_bss\0")
+                } else {
+                    CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_data\0")
+                };*/
+                unimplemented!();
+                //llvm::LLVMSetSection(global, sect_name.as_ptr());
+            }
+        }
+
+        // Wasm statics with custom link sections get special treatment as they
+        // go into custom sections of the wasm executable.
+        if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
+            if let Some(_section) = attrs.link_section {
+                unimplemented!();
+                /*let section = llvm::LLVMMDStringInContext(
+                    self.llcx,
+                    section.as_str().as_ptr().cast(),
+                    section.as_str().len() as c_uint,
+                );
+                assert!(alloc.relocations().is_empty());
+
+                // The `inspect` method is okay here because we checked relocations, and
+                // because we are doing this access to inspect the final interpreter state (not
+                // as part of the interpreter execution).
+                let bytes =
+                    alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len());
+                let alloc = llvm::LLVMMDStringInContext(
+                    self.llcx,
+                    bytes.as_ptr().cast(),
+                    bytes.len() as c_uint,
+                );
+                let data = [section, alloc];
+                let meta = llvm::LLVMMDNodeInContext(self.llcx, data.as_ptr(), 2);
+                llvm::LLVMAddNamedMetadataOperand(
+                    self.llmod,
+                    "wasm.custom_sections\0".as_ptr().cast(),
+                    meta,
+                );*/
+            }
+        } else {
+            // TODO
+            //base::set_link_section(global, &attrs);
+        }
+
+        if attrs.flags.contains(CodegenFnAttrFlags::USED) {
+            self.add_used_global(global);
+        }
+    }
+
+    /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
+    fn add_used_global(&self, _global: RValue<'gcc>) {
+        // TODO
+        //let cast = self.context.new_cast(None, global, self.type_i8p());
+        //self.used_statics.borrow_mut().push(cast);
+    }
+}
+
+impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
+    pub fn static_addr_of_mut(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
+        let (name, gv) =
+            match kind {
+                Some(kind) if !self.tcx.sess.fewer_names() => {
+                    let name = self.generate_local_symbol_name(kind);
+                    // TODO: check if it's okay that TLS is off here.
+                    // TODO: check if it's okay that link_section is None here.
+                    // TODO: set alignment here as well.
+                    let gv = self.define_global(&name[..], self.val_ty(cv), false, None).unwrap_or_else(|| {
+                        bug!("symbol `{}` is already defined", name);
+                    });
+                    //llvm::LLVMRustSetLinkage(gv, llvm::Linkage::PrivateLinkage);
+                    (name, gv)
+                }
+                _ => {
+                    let index = self.global_gen_sym_counter.get();
+                    let name = format!("global_{}_{}", index, self.codegen_unit.name());
+                    let typ = self.val_ty(cv).get_aligned(align.bytes());
+                    let global = self.define_private_global(typ);
+                    (name, global)
+                },
+            };
+        // FIXME: I think the name coming from generate_local_symbol_name() above cannot be used
+        // globally.
+        // NOTE: global seems to only be global in a module. So save the name instead of the value
+        // to import it later.
+        self.global_names.borrow_mut().insert(cv, name);
+        self.global_init_block.add_assignment(None, gv.dereference(None), cv);
+        //llvm::SetUnnamedAddress(gv, llvm::UnnamedAddr::Global);
+        gv
+    }
+
+    pub fn get_static(&self, def_id: DefId) -> RValue<'gcc> {
+        let instance = Instance::mono(self.tcx, def_id);
+        let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
+        if let Some(&global) = self.instances.borrow().get(&instance) {
+            /*let attrs = self.tcx.codegen_fn_attrs(def_id);
+            let name = &*self.tcx.symbol_name(instance).name;
+            let name =
+                if let Some(linkage) = attrs.linkage {
+                    // This is to match what happens in check_and_apply_linkage.
+                    Cow::from(format!("_rust_extern_with_linkage_{}", name))
+                }
+                else {
+                    Cow::from(name)
+                };
+            let global = self.context.new_global(None, GlobalKind::Imported, global.get_type(), &name)
+                .get_address(None);
+            self.global_names.borrow_mut().insert(global, name.to_string());*/
+            return global;
+        }
+
+        let defined_in_current_codegen_unit =
+            self.codegen_unit.items().contains_key(&MonoItem::Static(def_id));
+        assert!(
+            !defined_in_current_codegen_unit,
+            "consts::get_static() should always hit the cache for \
+                 statics defined in the same CGU, but did not for `{:?}`",
+            def_id
+        );
+
+        let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
+        let sym = self.tcx.symbol_name(instance).name;
+
+        //debug!("get_static: sym={} instance={:?}", sym, instance);
+
+        let global =
+            if let Some(def_id) = def_id.as_local() {
+                let id = self.tcx.hir().local_def_id_to_hir_id(def_id);
+                let llty = self.layout_of(ty).gcc_type(self, true);
+                // FIXME: refactor this to work without accessing the HIR
+                let global = match self.tcx.hir().get(id) {
+                    Node::Item(&hir::Item { span, kind: hir::ItemKind::Static(..), .. }) => {
+                        if let Some(global) = self.get_declared_value(&sym) {
+                            if self.val_ty(global) != self.type_ptr_to(llty) {
+                                span_bug!(span, "Conflicting types for static");
+                            }
+                        }
+
+                        let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
+                        let global = self.declare_global(&sym, llty, is_tls, fn_attrs.link_section);
+
+                        if !self.tcx.is_reachable_non_generic(def_id) {
+                            /*unsafe {
+                              llvm::LLVMRustSetVisibility(global, llvm::Visibility::Hidden);
+                              }*/
+                        }
+
+                        global
+                    }
+
+                    Node::ForeignItem(&hir::ForeignItem {
+                        span,
+                        kind: hir::ForeignItemKind::Static(..),
+                        ..
+                    }) => {
+                        let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
+                        check_and_apply_linkage(&self, &fn_attrs, ty, sym, span)
+                    }
+
+                    item => bug!("get_static: expected static, found {:?}", item),
+                };
+
+                //debug!("get_static: sym={} attrs={:?}", sym, attrs);
+
+                global
+            }
+            else {
+                // FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
+                //debug!("get_static: sym={} item_attr={:?}", sym, self.tcx.item_attrs(def_id));
+
+                let attrs = self.tcx.codegen_fn_attrs(def_id);
+                let span = self.tcx.def_span(def_id);
+                let global = check_and_apply_linkage(&self, &attrs, ty, sym, span);
+
+                let needs_dll_storage_attr = false; /*self.use_dll_storage_attrs && !self.tcx.is_foreign_item(def_id) &&
+                // ThinLTO can't handle this workaround in all cases, so we don't
+                // emit the attrs. Instead we make them unnecessary by disallowing
+                // dynamic linking when linker plugin based LTO is enabled.
+                !self.tcx.sess.opts.cg.linker_plugin_lto.enabled();*/
+
+                // If this assertion triggers, there's something wrong with commandline
+                // argument validation.
+                debug_assert!(
+                    !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
+                        && self.tcx.sess.target.options.is_like_msvc
+                        && self.tcx.sess.opts.cg.prefer_dynamic)
+                );
+
+                if needs_dll_storage_attr {
+                    // This item is external but not foreign, i.e., it originates from an external Rust
+                    // crate. Since we don't know whether this crate will be linked dynamically or
+                    // statically in the final application, we always mark such symbols as 'dllimport'.
+                    // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
+                    // to make things work.
+                    //
+                    // However, in some scenarios we defer emission of statics to downstream
+                    // crates, so there are cases where a static with an upstream DefId
+                    // is actually present in the current crate. We can find out via the
+                    // is_codegened_item query.
+                    if !self.tcx.is_codegened_item(def_id) {
+                        unimplemented!();
+                        /*unsafe {
+                            llvm::LLVMSetDLLStorageClass(global, llvm::DLLStorageClass::DllImport);
+                        }*/
+                    }
+                }
+                global
+            };
+
+        /*if self.use_dll_storage_attrs && self.tcx.is_dllimport_foreign_item(def_id) {
+            // For foreign (native) libs we know the exact storage type to use.
+            unsafe {
+                llvm::LLVMSetDLLStorageClass(global, llvm::DLLStorageClass::DllImport);
+            }
+        }*/
+
+        self.instances.borrow_mut().insert(instance, global);
+        global
+    }
+}
+
+pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: &Allocation) -> RValue<'gcc> {
+    let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1);
+    let dl = cx.data_layout();
+    let pointer_size = dl.pointer_size.bytes() as usize;
+
+    let mut next_offset = 0;
+    for &(offset, alloc_id) in alloc.relocations().iter() {
+        let offset = offset.bytes();
+        assert_eq!(offset as usize as u64, offset);
+        let offset = offset as usize;
+        if offset > next_offset {
+            // This `inspect` is okay since we have checked that it is not within a relocation, it
+            // is within the bounds of the allocation, and it doesn't affect interpreter execution
+            // (we inspect the result after interpreter execution). Any undef byte is replaced with
+            // some arbitrary byte value.
+            //
+            // FIXME: relay undef bytes to codegen as undef const bytes
+            let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(next_offset..offset);
+            llvals.push(cx.const_bytes(bytes));
+        }
+        let ptr_offset =
+            read_target_uint( dl.endian,
+                // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
+                // affect interpreter execution (we inspect the result after interpreter execution),
+                // and we properly interpret the relocation as a relocation pointer offset.
+                alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
+            )
+            .expect("const_alloc_to_llvm: could not read relocation pointer")
+            as u64;
+        llvals.push(cx.scalar_to_backend(
+            InterpScalar::from_pointer(
+                interpret::Pointer::new(alloc_id, Size::from_bytes(ptr_offset)),
+                &cx.tcx,
+            ),
+            &abi::Scalar { value: Primitive::Pointer, valid_range: 0..=!0 },
+            cx.type_i8p(),
+        ));
+        next_offset = offset + pointer_size;
+    }
+    if alloc.len() >= next_offset {
+        let range = next_offset..alloc.len();
+        // This `inspect` is okay since we have check that it is after all relocations, it is
+        // within the bounds of the allocation, and it doesn't affect interpreter execution (we
+        // inspect the result after interpreter execution). Any undef byte is replaced with some
+        // arbitrary byte value.
+        //
+        // FIXME: relay undef bytes to codegen as undef const bytes
+        let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range);
+        llvals.push(cx.const_bytes(bytes));
+    }
+
+    cx.const_struct(&llvals, true)
+}
+
+pub fn codegen_static_initializer<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, def_id: DefId) -> Result<(RValue<'gcc>, &'tcx Allocation), ErrorHandled> {
+    let alloc = cx.tcx.eval_static_initializer(def_id)?;
+    Ok((const_alloc_to_gcc(cx, alloc), alloc))
+}
+
+fn check_and_apply_linkage<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, attrs: &CodegenFnAttrs, ty: Ty<'tcx>, sym: &str, span: Span) -> RValue<'gcc> {
+    let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
+    let llty = cx.layout_of(ty).gcc_type(cx, true);
+    if let Some(linkage) = attrs.linkage {
+        //debug!("get_static: sym={} linkage={:?}", sym, linkage);
+
+        // If this is a static with a linkage specified, then we need to handle
+        // it a little specially. The typesystem prevents things like &T and
+        // extern "C" fn() from being non-null, so we can't just declare a
+        // static and call it a day. Some linkages (like weak) will make it such
+        // that the static actually has a null value.
+        let llty2 =
+            if let ty::RawPtr(ref mt) = ty.kind() {
+                cx.layout_of(mt.ty).gcc_type(cx, true)
+            }
+            else {
+                cx.sess().span_fatal(
+                    span,
+                    "must have type `*const T` or `*mut T` due to `#[linkage]` attribute",
+                )
+            };
+        // Declare a symbol `foo` with the desired linkage.
+        let global1 = cx.declare_global_with_linkage(&sym, llty2, base::global_linkage_to_gcc(linkage));
+
+        // Declare an internal global `extern_with_linkage_foo` which
+        // is initialized with the address of `foo`.  If `foo` is
+        // discarded during linking (for example, if `foo` has weak
+        // linkage and there are no definitions), then
+        // `extern_with_linkage_foo` will instead be initialized to
+        // zero.
+        let mut real_name = "_rust_extern_with_linkage_".to_string();
+        real_name.push_str(&sym);
+        let global2 =
+            cx.define_global(&real_name, llty, is_tls, attrs.link_section).unwrap_or_else(|| {
+                cx.sess().span_fatal(span, &format!("symbol `{}` is already defined", &sym))
+            });
+        //llvm::LLVMRustSetLinkage(global2, llvm::Linkage::InternalLinkage);
+        let lvalue = global2.dereference(None);
+        cx.global_init_block.add_assignment(None, lvalue, global1);
+        //llvm::LLVMSetInitializer(global2, global1);
+        global2
+    }
+    else {
+        // Generate an external declaration.
+        // FIXME(nagisa): investigate whether it can be changed into define_global
+
+        // Thread-local statics in some other crate need to *always* be linked
+        // against in a thread-local fashion, so we need to be sure to apply the
+        // thread-local attribute locally if it was present remotely. If we
+        // don't do this then linker errors can be generated where the linker
+        // complains that one object files has a thread local version of the
+        // symbol and another one doesn't.
+        cx.declare_global(&sym, llty, is_tls, attrs.link_section)
+    }
+}