[cfe-dev] GNU-style target triple and -m32 modifier

[Eli Friedman]

On Mon, May 16, 2011 at 12:23 AM, Joerg Sonnenberger
<joerg at britannica.bec.de> wrote:
> On Sun, May 15, 2011 at 03:22:24PM -0700, Eli Friedman wrote:
>> If I'm understanding correctly, passing -m32 to clang targeting
>> x86_64--netbsd is supposed to make executables targeting
>> i486--netbsdelf, but is incorrectly trying to use tools for
>> i486--netbsd.  You're trying to fix this by keeping around the
>> original target triple, and pretending that a i486--netbsd triple is
>> actually i486--netbsdelf if the original triple is x86_64--netbsd.  It
>> seems like it would be much more straightforward to just fix the
>> triple-handling code so that passing in -m32 figures out the correct
>> triple.
>
> Not exactly. Passing -m32 should have two results: *compile* for the
> equivalent of i386--netbsdelf and call as/ld with the correct 32bit
> flags. My problem here is that the original triple is "lost", so it
> tries to call the wrong cross-compile as/ld and uses the wrong arguments
> for those. E.g. correct behavior is to either call a x86_64 as with --32
> or a i386 as without, but currently neither happens.
>
> The patch contains this in the NetBSD specific targets, but I believe
> that the problem of distinguishing -m32 from "native" 32bit compilation
> might be a bit more popular to duplicate all the code.

I can see why the distinction is useful.

Given that you're only touching the NetBSD-specific code, whatever you
think is appropriate is probably close enough. You might be taking a
substantial perf hit from eliminating the cache, though.

-Eli