[m-dev.] MSVC and --no-smart-indexing

[Zoltan Somogyi]

On Mon, 9 Feb 2015 10:32:12 +1100, Paul Bone <paul at bone.id.au> wrote:
> > I don't have any convenient way to test cross-compilation between
> > 32 and 64 bit systems, but if someone does, I could generate diffs
> > for them to test.
> 
> I can test this.

I have had a look at the code that does smart indexing for both
the LLDS and MLDS backends, and the only things I could find
that depended on word size were (a) string hash switches,
where the hash function would use the full word size of the host
machine, and (b) bit vector checks, which used the configured
word size, i.e. the value of the bits_per_word compiler option.
I fixed (a) last week, and as far as I can tell, (b) has been
handled properly for a while, if only for the special case of creating
the source distribution, by the code in handle_options.m
that handles the pregenerated_dist option. Therefore I think
we can now remove the workaround of specifying --no-smart-indexing
in tools/build_srcdirst.

Paul, will you please try this out?

As for non-pregen applications of cross-compilation, I can change
the indexing methods that use bit vectors to use 32 bit words
even on platforms with bigger words, but I don't think that would
solve the bigger problem. The bigger problem is shown by these
scenarios:

machine A: 64 bit
machine B: 32 bit
machine C: 64 bit

a program has two modules: mod1 and mod2.

scenario (i)
on machine A: generate mod1.c with --cross-compiling
on machine B: generate mod2.c natively
on machine B: generate mod1.o, mod2.o and the executable

scenario (Ii)
on machine A: generate mod1.c with --cross-compiling
on machine C: generate mod2.c natively
on machine C: generate mod1.o, mod2.o and the executable

The $64k question: how many tag bits does machine A use
when creating mod1.c? Scenario (i) requires the answer to be 2;
scenario (ii) requires it to be 3.

(The pregen grade solves the problem by requiring the use
of 2 tag bits on all machines, even 64 bit, even *without*
--cross-compiling.)

Can anyone see a flaw in my reasoning?

Zoltan.