The war of symbol and symbol (the PR dedicated to duplicate symbols breaking rustc in unexpected ways)

src/librustc_llvm/lib.rs

@@ -157,7 +157,7 @@ bitflags! {
 #[derive(Copy, Clone)]
 pub enum OtherAttribute {
     // The following are not really exposed in
-    // the LLVM c api so instead to add these
+    // the LLVM C api so instead to add these
     // we call a wrapper function in RustWrapper
     // that uses the C++ api.
     SanitizeAddressAttribute = 1 << 32,
@@ -912,6 +912,7 @@ extern {
                                        AddressSpace: c_uint)
                                        -> ValueRef;
     pub fn LLVMGetNamedGlobal(M: ModuleRef, Name: *const c_char) -> ValueRef;
+    pub fn LLVMGetOrInsertGlobal(M: ModuleRef, Name: *const c_char, T: TypeRef) -> ValueRef;
     pub fn LLVMGetFirstGlobal(M: ModuleRef) -> ValueRef;
     pub fn LLVMGetLastGlobal(M: ModuleRef) -> ValueRef;
     pub fn LLVMGetNextGlobal(GlobalVar: ValueRef) -> ValueRef;
@@ -924,6 +925,7 @@ extern {
     pub fn LLVMSetThreadLocal(GlobalVar: ValueRef, IsThreadLocal: Bool);
     pub fn LLVMIsGlobalConstant(GlobalVar: ValueRef) -> Bool;
     pub fn LLVMSetGlobalConstant(GlobalVar: ValueRef, IsConstant: Bool);
+    pub fn LLVMGetNamedValue(M: ModuleRef, Name: *const c_char) -> ValueRef;
 
     /* Operations on aliases */
     pub fn LLVMAddAlias(M: ModuleRef,
@@ -957,6 +959,7 @@ extern {
     pub fn LLVMAddFunctionAttrString(Fn: ValueRef, index: c_uint, Name: *const c_char);
     pub fn LLVMRemoveFunctionAttrString(Fn: ValueRef, index: c_uint, Name: *const c_char);
     pub fn LLVMGetFunctionAttr(Fn: ValueRef) -> c_ulonglong;
+    pub fn LLVMRemoveFunctionAttr(Fn: ValueRef, val: c_ulonglong);
 
     /* Operations on parameters */
     pub fn LLVMCountParams(Fn: ValueRef) -> c_uint;

src/librustc_trans/trans/attributes.rs

@@ -0,0 +1,281 @@
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// 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;
+pub use syntax::attr::InlineAttr;
+use trans::base;
+use trans::common;
+use trans::context::CrateContext;
+use trans::machine;
+use trans::type_of;
+
+/// Mark LLVM function to use split stack.
+#[inline]
+pub fn split_stack(val: ValueRef, set: bool) {
+    unsafe {
+        let attr = "split-stack\0".as_ptr() as *const _;
+        if set {
+            llvm::LLVMAddFunctionAttrString(val, llvm::FunctionIndex as c_uint, attr);
+        } else {
+            llvm::LLVMRemoveFunctionAttrString(val, llvm::FunctionIndex as c_uint, attr);
+        }
+    }
+}
+
+/// Mark LLVM function to use provided inline heuristic.
+#[inline]
+pub fn inline(val: ValueRef, inline: InlineAttr) {
+    use self::InlineAttr::*;
+    match inline {
+        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;
+            unsafe {
+                llvm::LLVMRemoveFunctionAttr(val, attr.bits() as c_ulonglong)
+            }
+        },
+    };
+}
+
+/// Tell LLVM to emit or not emit the information necessary to unwind the stack for the function.
+#[inline]
+pub fn emit_uwtable(val: ValueRef, emit: bool) {
+    if emit {
+        llvm::SetFunctionAttribute(val, llvm::UWTableAttribute);
+    } else {
+        unsafe {
+            llvm::LLVMRemoveFunctionAttr(val, llvm::UWTableAttribute.bits() as c_ulonglong);
+        }
+    }
+}
+
+/// Tell LLVM whether the function can or cannot unwind.
+#[inline]
+#[allow(dead_code)] // possibly useful function
+pub fn unwind(val: ValueRef, can_unwind: bool) {
+    if can_unwind {
+        unsafe {
+            llvm::LLVMRemoveFunctionAttr(val, llvm::NoUnwindAttribute.bits() as c_ulonglong);
+        }
+    } else {
+        llvm::SetFunctionAttribute(val, llvm::NoUnwindAttribute);
+    }
+}
+
+/// Tell LLVM whether it should optimise function for size.
+#[inline]
+#[allow(dead_code)] // possibly useful function
+pub fn set_optimize_for_size(val: ValueRef, optimize: bool) {
+    if optimize {
+        llvm::SetFunctionAttribute(val, llvm::OptimizeForSizeAttribute);
+    } else {
+        unsafe {
+            llvm::LLVMRemoveFunctionAttr(val, llvm::OptimizeForSizeAttribute.bits() as c_ulonglong);
+        }
+    }
+}
+
+/// Composite function which sets LLVM attributes for function depending on its AST (#[attribute])
+/// attributes.
+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));
+
+    for attr in attrs {
+        if attr.check_name("no_stack_check") {
+            split_stack(llfn, false);
+        } else if attr.check_name("cold") {
+            unsafe {
+                llvm::LLVMAddFunctionAttribute(llfn,
+                                               llvm::FunctionIndex as c_uint,
+                                               llvm::ColdAttribute as u64)
+            }
+        } else if attr.check_name("allocator") {
+            llvm::NoAliasAttribute.apply_llfn(llvm::ReturnIndex as c_uint, llfn);
+        }
+    }
+}
+
+/// 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) => {
+                    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_rptr(_, ty::mt { ty: inner, .. })
+                | ty::ty_uniq(inner) if common::type_is_sized(ccx.tcx(), 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
+}