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Date: Sun, 21 Jun 2015 07:47:42 +0530
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From: Nicolas Ojeda Bar <n.oje.bar@gmail.com>
To: caml-list@inria.fr
Content-Type: text/plain; charset=UTF-8
Subject: [Caml-list] mips32 backend without floating point hardware

Hello list,

I am trying to get the mips o32 backend (from 1.*, ~17 years ago!)
working again on machines without *any* floating point hardware.

As suggested in the comments of selectgen.ml I overloaded

method regs_for : Cmm.machtype -> Reg.t array

to store float regs in pairs of int regs.  This works well for the
OCaml side of things, but the C abi dictates that float args should be
passed in even-odd pairs of int registers (i.e., either a0-a1 or
a2-a3).  Unfortunately I lost the Int/Float distinction after
overloading regs_for, so I can't enforce this constraint in
Proc.loc_external_arguments.  Similarly it is not possible to 8-align
extra floats in the stack since the type information is lost.

Any ideas/suggestions how to fit this situation to the existing
backend infrastructure ?

Thanks!

Best wishes,
Nicolas