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Use a single match arm for all TyRef variants when deducing function argument attributes

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This makes it a lot easier to later add attributes for fat pointers.
This commit is contained in:
Björn Steinbrink 2015-06-18 14:23:19 +02:00
parent 4b42cbd5eb
commit f862da5bb8
1 changed files with 19 additions and 25 deletions
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44
src/librustc_trans/trans/attributes.rs
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@ -262,41 +262,35 @@ pub fn from_fn_type<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, fn_type: ty::Ty<'tcx
.arg(idx, llvm::DereferenceableAttribute(llsz));
}
// `&mut` pointer parameters never alias other parameters, or mutable global data
//
// `&T` where `T` contains no `UnsafeCell<U>` is immutable, and can be marked as both
// `readonly` and `noalias`, as LLVM's definition of `noalias` is based solely on
// memory dependencies rather than pointer equality
ty::TyRef(b, mt) if mt.mutbl == ast::MutMutable ||
!ty::type_contents(ccx.tcx(), mt.ty).interior_unsafe() => {
ty::TyRef(b, mt) => {
// `&mut` pointer parameters never alias other parameters, or mutable global data
//
// `&T` where `T` contains no `UnsafeCell<U>` is immutable, and can be marked as
// both `readonly` and `noalias`, as LLVM's definition of `noalias` is based solely
// on memory dependencies rather than pointer equality
let interior_unsafe = ty::type_contents(ccx.tcx(), mt.ty).interior_unsafe();
let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, mt.ty));
attrs.arg(idx, llvm::Attribute::NoAlias)
.arg(idx, llvm::DereferenceableAttribute(llsz));
if mt.mutbl == ast::MutMutable || !interior_unsafe {
attrs.arg(idx, llvm::Attribute::NoAlias);
}
if mt.mutbl == ast::MutImmutable {
if mt.mutbl == ast::MutImmutable && !interior_unsafe {
attrs.arg(idx, llvm::Attribute::ReadOnly);
}
// & pointer parameters are also never null and we know exactly
// how many bytes we can dereference
let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, mt.ty));
attrs.arg(idx, llvm::DereferenceableAttribute(llsz));
// When a reference in an argument has no named lifetime, it's
// impossible for that reference to escape this function
// (returned or stored beyond the call by a closure).
if let ReLateBound(_, BrAnon(_)) = *b {
attrs.arg(idx, llvm::Attribute::NoCapture);
}
}
// When a reference in an argument has no named lifetime, it's impossible for that
// reference to escape this function (returned or stored beyond the call by a closure).
ty::TyRef(&ReLateBound(_, BrAnon(_)), mt) => {
let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, mt.ty));
attrs.arg(idx, llvm::Attribute::NoCapture)
.arg(idx, llvm::DereferenceableAttribute(llsz));
}
// & pointer parameters are also never null and we know exactly how
// many bytes we can dereference
ty::TyRef(_, mt) => {
let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, mt.ty));
attrs.arg(idx, llvm::DereferenceableAttribute(llsz));
}
_ => ()
}
}