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add back noalias to &mut T pointer parameters #13935

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Merged
merged 1 commit into from
May 5, 2014
Merged

add back noalias to &mut T pointer parameters #13935

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22 changes: 11 additions & 11 deletions src/librustc/middle/trans/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -186,8 +186,6 @@ fn decl_fn(llmod: ModuleRef, name: &str, cc: lib::llvm::CallConv,
}
}
// `~` pointer return values never alias because ownership is transferred
// FIXME #6750 ~Trait cannot be directly marked as
// noalias because the actual object pointer is nested.
ty::ty_uniq(..) // | ty::ty_trait(_, _, ty::UniqTraitStore, _, _)
=> {
unsafe {
Expand Down Expand Up @@ -258,23 +256,25 @@ pub fn decl_rust_fn(ccx: &CrateContext, has_env: bool,
let llarg = unsafe { llvm::LLVMGetParam(llfn, (offset + i) as c_uint) };
match ty::get(arg_ty).sty {
// `~` pointer parameters never alias because ownership is transferred
// FIXME #6750 ~Trait cannot be directly marked as
// noalias because the actual object pointer is nested.
ty::ty_uniq(..) | // ty::ty_trait(_, _, ty::UniqTraitStore, _, _) |
ty::ty_closure(~ty::ClosureTy {store: ty::UniqTraitStore, ..}) => {
ty::ty_uniq(..) => {
unsafe {
llvm::LLVMAddAttribute(llarg, lib::llvm::NoAliasAttribute as c_uint);
}
},
// When a reference in an argument has no named lifetime, it's
// impossible for that reference to escape this function(ie, be
// returned).
}
// `&mut` pointer parameters never alias other parameters, or mutable global data
ty::ty_rptr(_, mt) if mt.mutbl == ast::MutMutable => {
unsafe {
llvm::LLVMAddAttribute(llarg, lib::llvm::NoAliasAttribute as c_uint);
}
}
// 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::ty_rptr(ReLateBound(_, BrAnon(_)), _) => {
debug!("marking argument of {} as nocapture because of anonymous lifetime", name);
unsafe {
llvm::LLVMAddAttribute(llarg, lib::llvm::NoCaptureAttribute as c_uint);
}
},
}
_ => {
// For non-immediate arguments the callee gets its own copy of
// the value on the stack, so there are no aliases
Expand Down