[LLVMdev] Add support for ldr pseudo instruction in ARM integrated assembler

[David Peixotto]

>From all the discussion so far I would conclude that the community is ok
with adding this feature for arm as long as it comes with sufficient test
cases. Please speak up if you feel I have misinterpreted anything.

 

I will file a bug for this feature with the details of what we need to
implement and then ask back on the list for pointers/suggestions on the best
way to implement it.

 

-- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
by The Linux Foundation

 

 

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Renato Golin
Sent: Saturday, October 26, 2013 10:58 PM
To: Chris Lattner
Cc: Sean Silva; LLVM Dev
Subject: Re: [LLVMdev] Add support for ldr pseudo instruction in ARM
integrated assembler

 

So, it seems there are enough people on the plus side, I just wanted to make
sure we evaluate all sides before taking a decision to add syntactic sugar
to LLVM assembler.

 

My main concern is still the same as earlier this year: the integrated
assembler for ARM is still not complete, and the more extensions we add to
the back-end, the harder it'll be to get it into production quality.

 

That said...

 

 

On 27 October 2013 01:02, Chris Lattner <clattner at apple.com> wrote:

I agree.  These pseudo instructions seem like pure syntactic sugar that
should never be produced by the disassembler.  That doesn't make them bad,
in fact it makes them simpler to implement and reason about.

 

 

I agree with this line of thought, though it's not necessarily simple to
implement this specific one, because of the constant pools. You have to pay
attention if there aren't many pools next to each other, or where is the
best placement (due to proximity, relocations, alignment), etc. I'm not sure
we've got all that logic already in, so this patch might end up a lot bigger
than just adding a few parser lines.

 

Ultimately, I'm not against it, but I'd be a lot more comfortable if I saw
lots of tests and lots of people looking at it (from different angles), just
to make sure we're not missing anything obvious and introducing major
regressions because of syntactic sugar.

 

cheers,

--renato

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