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Deduplicate linkage checking code for statics
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Signed-off-by: Gabriel Smith <ga29smith@gmail.com>
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@yodaldevoid
yodaldevoid committed Jul 25, 2018
1 parent a20262c commit 0bcbe91
Showing 1 changed file with 69 additions and 85 deletions.
154 changes: 69 additions & 85 deletions src/librustc_codegen_llvm/consts.rs
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Expand Up @@ -20,12 +20,14 @@ use monomorphize::MonoItem;
use common::{CodegenCx, val_ty};
use declare;
use monomorphize::Instance;
use syntax_pos::Span;
use syntax_pos::symbol::LocalInternedString;
use type_::Type;
use type_of::LayoutLlvmExt;
use rustc::ty;
use rustc::ty::{self, Ty};
use rustc::ty::layout::{Align, LayoutOf};

use rustc::hir::{self, CodegenFnAttrFlags};
use rustc::hir::{self, CodegenFnAttrs, CodegenFnAttrFlags};

use std::ffi::{CStr, CString};

Expand Down Expand Up @@ -146,47 +148,8 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
hir_map::NodeForeignItem(&hir::ForeignItem {
ref attrs, span, node: hir::ForeignItemKind::Static(..), ..
}) => {
let g = if let Some(linkage) = cx.tcx.codegen_fn_attrs(def_id).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 = match ty.sty {
ty::TyRawPtr(ref mt) => cx.layout_of(mt.ty).llvm_type(cx),
_ => {
cx.sess().span_fatal(span, "must have type `*const T` or `*mut T`");
}
};
unsafe {
// Declare a symbol `foo` with the desired linkage.
let g1 = declare::declare_global(cx, &sym, llty2);
llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(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 g2 = declare::define_global(cx, &real_name, llty).unwrap_or_else(||{
cx.sess().span_fatal(span,
&format!("symbol `{}` is already defined", &sym))
});
llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage);
llvm::LLVMSetInitializer(g2, g1);
g2
}
} else {
// Generate an external declaration.
declare::declare_global(cx, &sym, llty)
};

(g, attrs)
let fn_attrs = cx.tcx.codegen_fn_attrs(def_id);
(check_and_apply_linkage(cx, &fn_attrs, ty, sym, Some(span)), attrs)
}

item => bug!("get_static: expected static, found {:?}", item)
Expand All @@ -205,55 +168,16 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
// FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
debug!("get_static: sym={} item_attr={:?}", sym, cx.tcx.item_attrs(def_id));

let codegen_fn_attrs = cx.tcx.codegen_fn_attrs(def_id);
let llty = cx.layout_of(ty).llvm_type(cx);
let g = if let Some(linkage) = codegen_fn_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 = match ty.sty {
ty::TyRawPtr(ref mt) => cx.layout_of(mt.ty).llvm_type(cx),
_ => {
bug!("must have type `*const T` or `*mut T`")
}
};
unsafe {
// Declare a symbol `foo` with the desired linkage.
let g1 = declare::declare_global(cx, &sym, llty2);
llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(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 g2 = declare::define_global(cx, &real_name, llty).unwrap_or_else(||{
bug!("symbol `{}` is already defined", &sym)
});
llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage);
llvm::LLVMSetInitializer(g2, g1);
g2
}
} else {
// Generate an external declaration.
// FIXME(nagisa): investigate whether it can be changed into define_global
declare::declare_global(cx, &sym, llty)
};
let attrs = cx.tcx.codegen_fn_attrs(def_id);
let g = check_and_apply_linkage(cx, &attrs, ty, sym, None);

// 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.
if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
llvm::set_thread_local_mode(g, cx.tls_model);
}

Expand Down Expand Up @@ -289,6 +213,66 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
g
}

fn check_and_apply_linkage<'tcx>(
cx: &CodegenCx<'_, 'tcx>,
attrs: &CodegenFnAttrs,
ty: Ty<'tcx>,
sym: LocalInternedString,
span: Option<Span>
) -> ValueRef {
let llty = cx.layout_of(ty).llvm_type(cx);
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 = match ty.sty {
ty::TyRawPtr(ref mt) => cx.layout_of(mt.ty).llvm_type(cx),
_ => {
if span.is_some() {
cx.sess().span_fatal(span.unwrap(), "must have type `*const T` or `*mut T`")
} else {
bug!("must have type `*const T` or `*mut T`")
}
}
};
unsafe {
// Declare a symbol `foo` with the desired linkage.
let g1 = declare::declare_global(cx, &sym, llty2);
llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(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 g2 = declare::define_global(cx, &real_name, llty).unwrap_or_else(||{
if span.is_some() {
cx.sess().span_fatal(
span.unwrap(),
&format!("symbol `{}` is already defined", &sym)
)
} else {
bug!("symbol `{}` is already defined", &sym)
}
});
llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage);
llvm::LLVMSetInitializer(g2, g1);
g2
}
} else {
// Generate an external declaration.
// FIXME(nagisa): investigate whether it can be changed into define_global
declare::declare_global(cx, &sym, llty)
}
}

pub fn codegen_static<'a, 'tcx>(
cx: &CodegenCx<'a, 'tcx>,
def_id: DefId,
Expand Down

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