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)

#include "gen/llvm.h"
#include "gen/tollvm.h"
#include "gen/irstate.h"
#include "ir/irmodule.h"

IrModule::IrModule(Module* module, const char* srcfilename)
{
    M = module;

    LLConstant* slice = DtoConstString(srcfilename);
    fileName = new llvm::GlobalVariable(
        slice->getType(), true, LLGlobalValue::InternalLinkage, slice, ".modulefilename", gIR->module);
}

IrModule::~IrModule()
{
}