add support for closure calls

Compiling languages with closures often requires passing
an extra environment parameter to the called function.

One solution is to use a convention, and reserve, say,
the first argument for that purpose.   However, that
makes binding to C a little less smooth.

Alternatively, QBE now provides a way to remain fully
ABI compatible with C by having a "hidden" environment
argument (marked with the keyword 'env').  Calling a
function expecting an environment from C will make the
contents of the environment undefined, but the normal
arguments will be passed without alteration.  Conversely,
calling a C function like it is a closure by passing
it an environemnt will work smoothly.

0 files changed, 0 insertions, 0 deletions