[LLVMdev] [cfe-dev] Integrated ARM assembler

[Greg Fitzgerald]

>> The assembly parser does not parse the ARM-ELF directives.
> Is this for inline asm?

Yep


>> $ echo "void a(){}" | clang -target arm-none-linux-gnueabi -mllvm
-arm-enable-ehabi -integrated-as -c -xc -
>>Not implemented yet
> Seems to work for me... ;)

I see this just recently changed.  I just confirmed the issue is in the
'release_32' branch, but not in 'master'.


>> There are -Wa options that the integrated assembler does not recognize.
> That's not really a problem and will *always* be that way.

What I'd prefer to see is if the integrated-as doesn't recognize the
option, clang should report a warning and switch to the 'no-integrated-as'
path.  Thoughts?


> I think the key question is over the directives LLVM itself decides to
generate as a result of
Clang invocations

I agree that's the more important question, but shouldn't we be able to
throw hand-written assembly files at clang too?

It'd be nice to assert that clang can consume its own generated
assembly.  Check
this out (for brevity, assumes arm target is the default):

$ echo "void a(){}" | clang -x c -S - -o - | clang -x assembler -c -
-integrated-as
<stdin>:2:2: error: unknown directive
.eabi_attribute 6, 2


> Does anyone know of actual clang regressions that would be triggered?

I haven't seen any serious issues.  Just little things like getting
"unsupported argument" if you throw it: "-Wa,-mimplicit-it=always".


> I'd like to see integrated-as enabled as soon as it reasonably can be

I agree, but if you do it today, some builds will certainly choke at
compile-time.  Chromium serves as a nice big workload that currently builds
with a very recent version of Clang.  As is, that build will go down if you
switched the default on them.

Thanks,
Greg


On Tue, Feb 5, 2013 at 1:56 PM, Tim Northover <t.p.northover at gmail.com>wrote:

> Hi Greg,
>
> I'd also like to see the integrated assembler enabled, though I'm only
> very weakly connected to the 32-bit backend.
>
> > 1) The assembly parser does not parse the ARM-ELF directives.
>
> Renato asked about inline assembly here, but I think the key question
> is over the directives LLVM itself decides to generate as a result of
> Clang invocations. I had a very brief encounter last year which
> suggested this path was in place.
>
> Is there anything you're aware of that's missing along that route? If
> there is, I think there's a good chance we can invest some time in
> fixing it.
>
> In general terms, I'd like to see integrated-as enabled as soon as it
> reasonably can be. Relying on gas is icky. Does anyone know of actual
> clang regressions that would be triggered?
>
> Cheers.
>
> Tim
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130205/781a112a/attachment.html>