[LLVMdev] Is there any llvm neon intrinsic that maps to vmla.f32 instruction ?

[Sebastien DELDON-GNB]

Hi David,

Your point is correct, I guess then vmlx-forwarding attribute needs to be revisited, since it is on by default for Cortex-A9. So far on codes I'm looking at (not only MILC), it always a win to disable it for Cortex-A9. In any case, I'm speaking about scalar (not vector) fp (not integer) operations, that's why I would like a way to selectively enable it for such kind of operations only.

Best Regards
Seb

From: David Tweed [mailto:david.tweed at arm.com]
Sent: Monday, February 11, 2013 5:46 PM
To: 'Renato Golin'; Sebastien DELDON-GNB
Cc: llvmdev at cs.uiuc.edu
Subject: RE: [LLVMdev] Is there any llvm neon intrinsic that maps to vmla.f32 instruction ?

Hi,

| If we find that this optimization produces worse code in more cases than not, than we should leave it disable by default and let the user enable when necessary. I'll let Bob follow up on that, since I don't know what benchmarks he used.

Note that it may well be the case that the most "generally performant" default may vary between different ARM cores as well as various types of code. It would certainly be as well to try benchmarking on different cores. as theoretical discussion of which code sequence is better is often add odds with empirically observed results.

Cheers,
Dave
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130211/41b9f6ed/attachment.html>