Move a big attribute fn into trans::attributes

Author: nagisa

src/librustc_trans/trans/attributes.rs

@@ -9,13 +9,17 @@
 // except according to those terms.
 //! Set and unset common attributes on LLVM values.
 
+use libc::{c_uint, c_ulonglong};
 use llvm::{self, ValueRef, AttrHelper};
+use middle::ty::{self, ClosureTyper};
+use syntax::abi;
 use syntax::ast;
-use syntax::attr::InlineAttr;
-pub use syntax::attr::InlineAttr::*;
+pub use syntax::attr::InlineAttr;
+use trans::base;
+use trans::common;
 use trans::context::CrateContext;
-
-use libc::{c_uint, c_ulonglong};
+use trans::machine;
+use trans::type_of;
 
 /// Mark LLVM function to use split stack.
 #[inline]
@@ -33,11 +37,12 @@ pub fn split_stack(val: ValueRef, set: bool) {
 /// Mark LLVM function to use provided inline heuristic.
 #[inline]
 pub fn inline(val: ValueRef, inline: InlineAttr) {
+    use self::InlineAttr::*;
     match inline {
-        InlineHint   => llvm::SetFunctionAttribute(val, llvm::InlineHintAttribute),
-        InlineAlways => llvm::SetFunctionAttribute(val, llvm::AlwaysInlineAttribute),
-        InlineNever  => llvm::SetFunctionAttribute(val, llvm::NoInlineAttribute),
-        InlineNone   => {
+        Hint   => llvm::SetFunctionAttribute(val, llvm::InlineHintAttribute),
+        Always => llvm::SetFunctionAttribute(val, llvm::AlwaysInlineAttribute),
+        Never  => llvm::SetFunctionAttribute(val, llvm::NoInlineAttribute),
+        None   => {
             let attr = llvm::InlineHintAttribute |
                        llvm::AlwaysInlineAttribute |
                        llvm::NoInlineAttribute;
@@ -88,7 +93,7 @@ pub fn set_optimize_for_size(val: ValueRef, optimize: bool) {
 
 /// Composite function which sets LLVM attributes for function depending on its AST (#[attribute])
 /// attributes.
-pub fn convert_fn_attrs_to_llvm(ccx: &CrateContext, attrs: &[ast::Attribute], llfn: ValueRef) {
+pub fn from_fn_attrs(ccx: &CrateContext, attrs: &[ast::Attribute], llfn: ValueRef) {
     use syntax::attr::*;
     inline(llfn, find_inline_attr(Some(ccx.sess().diagnostic()), attrs));
 
@@ -110,3 +115,173 @@ pub fn convert_fn_attrs_to_llvm(ccx: &CrateContext, attrs: &[ast::Attribute], ll
         }
     }
 }
+
+/// Composite function which converts function type into LLVM attributes for the function.
+pub fn from_fn_type<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, fn_type: ty::Ty<'tcx>)
+                              -> llvm::AttrBuilder {
+    use middle::ty::{BrAnon, ReLateBound};
+
+    let function_type;
+    let (fn_sig, abi, env_ty) = match fn_type.sty {
+        ty::ty_bare_fn(_, ref f) => (&f.sig, f.abi, None),
+        ty::ty_closure(closure_did, substs) => {
+            let typer = common::NormalizingClosureTyper::new(ccx.tcx());
+            function_type = typer.closure_type(closure_did, substs);
+            let self_type = base::self_type_for_closure(ccx, closure_did, fn_type);
+            (&function_type.sig, abi::RustCall, Some(self_type))
+        }
+        _ => ccx.sess().bug("expected closure or function.")
+    };
+
+    let fn_sig = ty::erase_late_bound_regions(ccx.tcx(), fn_sig);
+
+    let mut attrs = llvm::AttrBuilder::new();
+    let ret_ty = fn_sig.output;
+
+    // These have an odd calling convention, so we need to manually
+    // unpack the input ty's
+    let input_tys = match fn_type.sty {
+        ty::ty_closure(..) => {
+            assert!(abi == abi::RustCall);
+
+            match fn_sig.inputs[0].sty {
+                ty::ty_tup(ref inputs) => {
+                    let mut full_inputs = vec![env_ty.expect("Missing closure environment")];
+                    full_inputs.push_all(inputs);
+                    full_inputs
+                }
+                _ => ccx.sess().bug("expected tuple'd inputs")
+            }
+        },
+        ty::ty_bare_fn(..) if abi == abi::RustCall => {
+            let mut inputs = vec![fn_sig.inputs[0]];
+
+            match fn_sig.inputs[1].sty {
+                ty::ty_tup(ref t_in) => {
+                    inputs.push_all(&t_in[..]);
+                    inputs
+                }
+                _ => ccx.sess().bug("expected tuple'd inputs")
+            }
+        }
+        _ => fn_sig.inputs.clone()
+    };
+
+    // Index 0 is the return value of the llvm func, so we start at 1
+    let mut first_arg_offset = 1;
+    if let ty::FnConverging(ret_ty) = ret_ty {
+        // A function pointer is called without the declaration
+        // available, so we have to apply any attributes with ABI
+        // implications directly to the call instruction. Right now,
+        // the only attribute we need to worry about is `sret`.
+        if type_of::return_uses_outptr(ccx, ret_ty) {
+            let llret_sz = machine::llsize_of_real(ccx, type_of::type_of(ccx, ret_ty));
+
+            // The outptr can be noalias and nocapture because it's entirely
+            // invisible to the program. We also know it's nonnull as well
+            // as how many bytes we can dereference
+            attrs.arg(1, llvm::StructRetAttribute)
+                 .arg(1, llvm::NoAliasAttribute)
+                 .arg(1, llvm::NoCaptureAttribute)
+                 .arg(1, llvm::DereferenceableAttribute(llret_sz));
+
+            // Add one more since there's an outptr
+            first_arg_offset += 1;
+        } else {
+            // The `noalias` attribute on the return value is useful to a
+            // function ptr caller.
+            match ret_ty.sty {
+                // `~` pointer return values never alias because ownership
+                // is transferred
+                ty::ty_uniq(it) if !common::type_is_sized(ccx.tcx(), it) => {}
+                ty::ty_uniq(_) => {
+                    attrs.ret(llvm::NoAliasAttribute);
+                }
+                _ => {}
+            }
+
+            // We can also mark the return value as `dereferenceable` in certain cases
+            match ret_ty.sty {
+                // These are not really pointers but pairs, (pointer, len)
+                ty::ty_uniq(it) |
+                ty::ty_rptr(_, ty::mt { ty: it, .. }) if !common::type_is_sized(ccx.tcx(), it) => {}
+                ty::ty_uniq(inner) | ty::ty_rptr(_, ty::mt { ty: inner, .. }) => {
+                    let llret_sz = machine::llsize_of_real(ccx, type_of::type_of(ccx, inner));
+                    attrs.ret(llvm::DereferenceableAttribute(llret_sz));
+                }
+                _ => {}
+            }
+
+            if let ty::ty_bool = ret_ty.sty {
+                attrs.ret(llvm::ZExtAttribute);
+            }
+        }
+    }
+
+    for (idx, &t) in input_tys.iter().enumerate().map(|(i, v)| (i + first_arg_offset, v)) {
+        match t.sty {
+            // this needs to be first to prevent fat pointers from falling through
+            _ if !common::type_is_immediate(ccx, t) => {
+                let llarg_sz = machine::llsize_of_real(ccx, type_of::type_of(ccx, t));
+
+                // For non-immediate arguments the callee gets its own copy of
+                // the value on the stack, so there are no aliases. It's also
+                // program-invisible so can't possibly capture
+                attrs.arg(idx, llvm::NoAliasAttribute)
+                     .arg(idx, llvm::NoCaptureAttribute)
+                     .arg(idx, llvm::DereferenceableAttribute(llarg_sz));
+            }
+
+            ty::ty_bool => {
+                attrs.arg(idx, llvm::ZExtAttribute);
+            }
+
+            // `~` pointer parameters never alias because ownership is transferred
+            ty::ty_uniq(inner) => {
+                let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, inner));
+
+                attrs.arg(idx, llvm::NoAliasAttribute)
+                     .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::ty_rptr(b, mt) if mt.mutbl == ast::MutMutable ||
+                                  !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::NoAliasAttribute)
+                     .arg(idx, llvm::DereferenceableAttribute(llsz));
+
+                if mt.mutbl == ast::MutImmutable {
+                    attrs.arg(idx, llvm::ReadOnlyAttribute);
+                }
+
+                if let ReLateBound(_, BrAnon(_)) = *b {
+                    attrs.arg(idx, llvm::NoCaptureAttribute);
+                }
+            }
+
+            // 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(_)), mt) => {
+                let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, mt.ty));
+                attrs.arg(idx, llvm::NoCaptureAttribute)
+                     .arg(idx, llvm::DereferenceableAttribute(llsz));
+            }
+
+            // & pointer parameters are also never null and we know exactly how
+            // many bytes we can dereference
+            ty::ty_rptr(_, mt) => {
+                let llsz = machine::llsize_of_real(ccx, type_of::type_of(ccx, mt.ty));
+                attrs.arg(idx, llvm::DereferenceableAttribute(llsz));
+            }
+            _ => ()
+        }
+    }
+
+    attrs
+}