Count the sret register as well when keeping track of how many integer registers are available for extern(C) functions on x86-64. Interestingly, llvm-g++ seems to have a very similar bug: http://llvm.org/pr4242 (So this breaks ABI-compatibility with llvm-gcc for this corner case, but gains it with gcc...) To clarify, this is about code like this: {{{ struct S { void*[3] data; } struct T { void*[2] data; } // The T should be passed in memory, and p in the last int register. extern(C) S fail(int, int, int, int, T t, void* p) { S s; s.data[0] = t.data[0]; s.data[1] = t.data[1]; s.data[2] = p; return s; } }}} which should generate code functionally equivalent to this: {{{ extern(C) S* succeed(S* s, int, int, int, int, T t, void* p) { s.data[0] = t.data[0]; s.data[1] = t.data[1]; s.data[2] = p; return s; } }}} (with the same definitions for S and T)

#ifndef LDC_IR_IRVAR_H
#define LDC_IR_IRVAR_H

#include "ir/ir.h"
#include "llvm/Type.h"

struct IrVar : IrBase
{
    IrVar(VarDeclaration* var);

    VarDeclaration* V;
    llvm::Value* value;
};

// represents a global variable
struct IrGlobal : IrVar
{
    IrGlobal(VarDeclaration* v);

    llvm::PATypeHolder type;
    llvm::Constant* constInit;
};

// represents a local variable variable
struct IrLocal : IrVar
{
    IrLocal(VarDeclaration* v);

    bool byref;         // Not used for -nested-ctx=array
    int nestedDepth;    // ditto
    int nestedIndex;
};

// represents an aggregate field variable
struct IrField : IrVar
{
    IrField(VarDeclaration* v);

    unsigned index;
    unsigned unionOffset;

    llvm::Constant* getDefaultInit();

protected:
    /// FIXME: only used for StructLiteralsExps
    llvm::Constant* constInit;
};

#endif