llvm dev - Jul 2014 - [LLVMdev] JIT on armhf, again

On 7/23/14, 1:20 PM, Tim Northover wrote:
[...]
> You should probably be specifying a triple directly, and making it an
> AAPCS-VFP one for good measure: "armv7-linux-gnueabihf" for
example,
> or "thumbv7-none-eabihf". You shouldn't even need to set
FloatABI for
> those two.
How do I do this? (I can't find any examples, and the API is decidedly
unclear...)

-- 
┌─── ｄｇ＠ｃｏｗｌａｒｋ．ｃｏｍ ───── http://www.cowlark.com ─────
│ "Feminism encourages women to leave their husbands, kill their
│ children, practice withcraft, destroy capitalism and become lesbians."
│ --- Rev. Pat Robertson

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 876 bytes
Desc: OpenPGP digital signature
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20140723/797a8e41/attachment.sig>

>> You should probably be specifying a triple directly, and making it an
>> AAPCS-VFP one for good measure: "armv7-linux-gnueabihf" for
example,
>> or "thumbv7-none-eabihf". You shouldn't even need to set
FloatABI for
>> those two.
>
> How do I do this? (I can't find any examples, and the API is decidedly
> unclear...)
It looks like it's a case of calling Module::setTargetTriple. As with
most JIT setup questions, though, often the best way to find out is to
get something working in lli and then look at what it does
(tools/lli/lli.cpp).

Cheers.

Tim.

On 7/23/14, 3:30 PM, Tim Northover wrote:
[...]
> It looks like it's a case of calling Module::setTargetTriple. As with
> most JIT setup questions, though, often the best way to find out is to
> get something working in lli and then look at what it does
> (tools/lli/lli.cpp).
Well, it's *almost* working --- hardfloat code is now being generated,
and it even seems to be right most of the time!

Unfortunately it looks like it's getting calling conventions wrong. This
IR code:

define void @Entrypoint(float %in, float* %out) {
  store float %in, float* %out
}

...gets compiled to this:

  STRi12 %R0<kill>, %R1<kill>, 0, pred:14, pred:%noreg;
mem:ST4[%out]
  BX_RET pred:14, pred:%noreg

(typed by hand, so may contain typos).

So it looks like it's assuming that float parameters are being passed in
integer registers, which isn't the case on armhf.

Could it be under the impression that I'm running on an armel system? In
which case the above code is correct. This would explain why the default
setting appears to generate armel code. Is this controllable?

-- 
┌─── ｄｇ＠ｃｏｗｌａｒｋ．ｃｏｍ ───── http://www.cowlark.com ─────
│ "Feminism encourages women to leave their husbands, kill their
│ children, practice withcraft, destroy capitalism and become lesbians."
│ --- Rev. Pat Robertson

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 876 bytes
Desc: OpenPGP digital signature
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20140723/f824b31c/attachment.sig>