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RFC: linker placement attribute proposed implementation #13661

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RFC: linker placement attribute proposed implementation #13661

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ef4ec38
Added support for #[unsafe_override_address]
Apr 21, 2014
54ed4b3
Removed unused override_reach
Apr 21, 2014
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109 changes: 62 additions & 47 deletions src/librustc/middle/trans/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1851,62 +1851,77 @@ pub fn get_item_val(ccx: &CrateContext, id: ast::NodeId) -> ValueRef {

// We need the translated value here, because for enums the
// LLVM type is not fully determined by the Rust type.
let (v, inlineable) = consts::const_expr(ccx, expr, is_local);
let (v, inlineable) = if attr::contains_name(i.attrs.as_slice(),
"unsafe_override_address") {
let (addrconst, _) = consts::const_expr(ccx, expr, is_local);
let llptrty = type_of(ccx, ty).ptr_to().to_ref();
let ptr = unsafe { llvm::LLVMConstIntToPtr(addrconst, llptrty) };

(ptr, true)
} else {
consts::const_expr(ccx, expr, is_local)
};
ccx.const_values.borrow_mut().insert(id, v);
let mut inlineable = inlineable;

unsafe {
let llty = llvm::LLVMTypeOf(v);
let g = sym.with_c_str(|buf| {
llvm::LLVMAddGlobal(ccx.llmod, llty, buf)
});
if attr::contains_name(i.attrs.as_slice(), "unsafe_override_address") {
ccx.item_symbols.borrow_mut().insert(i.id, sym);
foreign = true;
v
} else {
unsafe {
let llty = llvm::LLVMTypeOf(v);
let g = sym.with_c_str(|buf| {
llvm::LLVMAddGlobal(ccx.llmod, llty, buf)
});

if !ccx.reachable.contains(&id) {
lib::llvm::SetLinkage(g, lib::llvm::InternalLinkage);
}

if !ccx.reachable.contains(&id) {
lib::llvm::SetLinkage(g, lib::llvm::InternalLinkage);
}
// Apply the `unnamed_addr` attribute if
// requested
if attr::contains_name(i.attrs.as_slice(),
"address_insignificant") {
if ccx.reachable.contains(&id) {
ccx.sess().span_bug(i.span,
"insignificant static is reachable");
}
lib::llvm::SetUnnamedAddr(g, true);

// This is a curious case where we must make
// all of these statics inlineable. If a
// global is tagged as
// address_insignificant, then LLVM won't
// coalesce globals unless they have an
// internal linkage type. This means that
// external crates cannot use this global.
// This is a problem for things like inner
// statics in generic functions, because the
// function will be inlined into another
// crate and then attempt to link to the
// static in the original crate, only to
// find that it's not there. On the other
// side of inlininig, the crates knows to
// not declare this static as
// available_externally (because it isn't)
inlineable = true;
}

// Apply the `unnamed_addr` attribute if
// requested
if attr::contains_name(i.attrs.as_slice(),
"address_insignificant") {
if ccx.reachable.contains(&id) {
ccx.sess().span_bug(i.span,
"insignificant static is reachable");
if attr::contains_name(i.attrs.as_slice(),
"thread_local") {
lib::llvm::set_thread_local(g, true);
}
lib::llvm::SetUnnamedAddr(g, true);

// This is a curious case where we must make
// all of these statics inlineable. If a
// global is tagged as
// address_insignificant, then LLVM won't
// coalesce globals unless they have an
// internal linkage type. This means that
// external crates cannot use this global.
// This is a problem for things like inner
// statics in generic functions, because the
// function will be inlined into another
// crate and then attempt to link to the
// static in the original crate, only to
// find that it's not there. On the other
// side of inlininig, the crates knows to
// not declare this static as
// available_externally (because it isn't)
inlineable = true;
}

if attr::contains_name(i.attrs.as_slice(),
"thread_local") {
lib::llvm::set_thread_local(g, true);
}
if !inlineable {
debug!("{} not inlined", sym);
ccx.non_inlineable_statics.borrow_mut()
.insert(id);
}

if !inlineable {
debug!("{} not inlined", sym);
ccx.non_inlineable_statics.borrow_mut()
.insert(id);
ccx.item_symbols.borrow_mut().insert(i.id, sym);
g
}

ccx.item_symbols.borrow_mut().insert(i.id, sym);
g
}
}

Expand Down
22 changes: 16 additions & 6 deletions src/librustc/middle/trans/consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,8 @@ use std::c_str::ToCStr;
use std::slice;
use std::vec::Vec;
use libc::c_uint;
use syntax::{ast, ast_util};
use syntax::{ast, ast_util, ast_map, attr};


pub fn const_lit(cx: &CrateContext, e: &ast::Expr, lit: ast::Lit)
-> ValueRef {
Expand Down Expand Up @@ -683,13 +684,22 @@ pub fn trans_const(ccx: &CrateContext, m: ast::Mutability, id: ast::NodeId) {
unsafe {
let _icx = push_ctxt("trans_const");
let g = base::get_item_val(ccx, id);
let item = ccx.tcx.map.get(id);
let isglobal = match item {
ast_map::NodeItem(i) =>
if attr::contains_name(i.attrs.as_slice(),
"unsafe_override_address") {false} else {true},
_ => true,
};
// At this point, get_item_val has already translated the
// constant's initializer to determine its LLVM type.
let v = ccx.const_values.borrow().get_copy(&id);
llvm::LLVMSetInitializer(g, v);
if m != ast::MutMutable {
llvm::LLVMSetGlobalConstant(g, True);
if isglobal {
let v = ccx.const_values.borrow().get_copy(&id);
llvm::LLVMSetInitializer(g, v);
if m != ast::MutMutable {
llvm::LLVMSetGlobalConstant(g, True);
}
debuginfo::create_global_var_metadata(ccx, id, g);
}
debuginfo::create_global_var_metadata(ccx, id, g);
}
}
18 changes: 15 additions & 3 deletions src/librustc/middle/typeck/check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -585,7 +585,15 @@ pub fn check_item(ccx: &CrateCtxt, it: &ast::Item) {
let _indenter = indenter();

match it.node {
ast::ItemStatic(_, _, e) => check_const(ccx, it.span, e, it.id),
ast::ItemStatic(_, _, e) => {
// override type to uint if it's unsafe_override_address, to make things
// like static t: T = 123 work.
if attr::contains_name(it.attrs.as_slice(), "unsafe_override_address") {
check_const(ccx, it.span, e, it.id, Some(ty::mk_u32()));
} else {
check_const(ccx, it.span, e, it.id, None);
}
}
ast::ItemEnum(ref enum_definition, _) => {
check_enum_variants(ccx,
it.span,
Expand Down Expand Up @@ -3407,11 +3415,15 @@ pub fn check_block_with_expected(fcx: &FnCtxt,
pub fn check_const(ccx: &CrateCtxt,
sp: Span,
e: &ast::Expr,
id: ast::NodeId) {
id: ast::NodeId,
override_ty: Option<ty::t>) {
let inh = blank_inherited_fields(ccx);
let rty = ty::node_id_to_type(ccx.tcx, id);
let fcx = blank_fn_ctxt(ccx, &inh, rty, e.id);
let declty = fcx.ccx.tcx.tcache.borrow().get(&local_def(id)).ty;
let declty = match override_ty {
Some(t) => t,
None => fcx.ccx.tcx.tcache.borrow().get(&local_def(id)).ty,
};
check_const_with_ty(&fcx, sp, e, declty);
}

Expand Down