Fun with parameter attributes: For several of the "synthetic" parameters added to D functions, we can apply noalias and nocapture. They are sret parameters, 'nest' pointers passed to nested functions, and _argptr: Nocapture: - Sret and nest are nocapture because they don't represent D-level variables, and thus the callee can't (validly) obtain a pointer to them, let alone keep it around after it returns. - _argptr is nocapture because although the callee has access to it as a pointer, that pointer is invalidated when it returns. All three are noalias because they're function-local variables - Sret and _argptr are noalias because they're freshly alloca'd memory only used for a single function call that's not allowed to keep an aliasing pointer to it around (since the parameter is nocapture). - 'Nest' is noalias because the callee only ever has access to one such pointer per parent function, and every parent function has a different one. This commit also ensures attributes set on sret, _arguments and _argptr are propagated to calls to such functions. It also adds one exception to the general rule that attributes on function types should propagate to calls: the type of a delegate's function pointer has a 'nest' parameter, but this can either be a true 'nest' (for delegates to nested functions) or a 'this' (for delegates to member functions). Since 'this' is neither noalias nor nocapture, and there's generally no way to tell which one it is, we remove these attributes at the call site if the callee is a delegate.

#ifndef __LDC_GEN_ABI_H__
#define __LDC_GEN_ABI_H__

#include <vector>

struct Type;
struct IrFuncTyArg;
struct DValue;

namespace llvm
{
    class Type;
    class Value;
}

// return rewrite rule
struct ABIRewrite
{
    /// get a rewritten value back to its original form
    virtual LLValue* get(Type* dty, DValue* v) = 0;

    /// get a rewritten value back to its original form and store result in provided lvalue
    /// this one is optional and defaults to calling the one above
    virtual void getL(Type* dty, DValue* v, llvm::Value* lval);

    /// put out rewritten value
    virtual LLValue* put(Type* dty, DValue* v) = 0;

    /// should return the transformed type for this rewrite
    virtual const LLType* type(Type* dty, const LLType* t) = 0;
};

// interface called by codegen
struct TargetABI
{
    static TargetABI* getTarget();

    virtual void newFunctionType(TypeFunction* tf) {}
    virtual bool returnInArg(TypeFunction* tf) = 0;
    virtual bool passByVal(Type* t) = 0;
    virtual void doneWithFunctionType() {}

    virtual void rewriteFunctionType(TypeFunction* t) = 0;
};

#endif