[llvm-commits] Fixing Bug 13662: paired register for inline asm with 64-bit data on ARM

[Weiming Zhao]

Hi Jakob,

 

Thanks for your reviewing.

Are you suggesting to first fix the DAG framework to let it support untyped
nodes, and then in ARM inline asm, we use copyToReg/CopyFromReg instead of
creating virtual regs?

 

Thanks,

Weiming

 

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

 

From: Jakob Stoklund Olesen [mailto:stoklund at 2pi.dk] 
Sent: Tuesday, December 04, 2012 10:19 AM
To: weimingz at codeaurora.org; Zhao
Cc: Evan Cheng; llvm-commits at cs.uiuc.edu; grosbach at apple.com
Subject: Re: [llvm-commits] Fixing Bug 13662: paired register for inline asm
with 64-bit data on ARM

 

 

On Dec 4, 2012, at 9:04 AM, Weiming Zhao <weimingz at codeaurora.org> wrote:

 

I have to change CodeGen/SelectionDAG/InstrEmitter.cpp a litte bit because:
for the inline asm nodes, I have to put a virtual reg instead of a value
node.

 

Hi Weiming,

 

I'm a bit concerned about this change. A RegisterSDNode doesn't include any
kind of dependency edges, so you have a 50/50 chance of you virtual register
def coming before your use. I don't think you can use virtual registers in
the SelectionDAG that way.

 

And due to "untyped" type, I can't insert CopyFromReg or CopyToReg as the
framework won't find the GPRPairReg class.

So I have to directly connect ExtractSubReg, RegSequence with a Register
SDNode.

 

An 'untyped' SelectionDAG edge only works when InstrEmitter can derive its
register class from the defining node. That currently works for REG_SEQUENCE
nodes - you probably need to make it work for INLINEASM nodes as well.

 

It would also be a good idea to break your patch in two: One part for
providing the target-independent framework needed, and one part that fixes
the ARM target.

 

/jakob

 

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