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)

#!/bin/bash

HOST_TARGET=$1

[ "$HOST_TARGET" = "" ] && exit 1

REST=`echo $HOST_TARGET   | sed -e 's/[a-zA-Z0-9_]*\(\-.*\)/\1/'`
X86=`echo $HOST_TARGET    | sed -e 's/\(i[3-9]86\)\-.*/\1/'`
X86_64=`echo $HOST_TARGET | sed -e 's/\(x86_64\)\-.*/\1/'`

ALT=
if [ "$X86_64" != "$HOST_TARGET" ]; then
    ALT="i686$REST"

elif [ "$X86" != "$HOST_TARGET" ]; then
    ALT="x86_64$REST"
fi

echo $ALT