[LLVMdev] PBQP spilling

Arnaud A. de Grandmaison arnaud.degrandmaison at arm.com
Wed Mar 4 06:42:48 PST 2015

Yes, for now the spilling is done in the most basic way, i.e. it's
functionally correct --- but not efficient. The focus was on the allocator
itself, not on the spilling. As you noticed, the work still to be done in
this area is live range splitting, and smarter spill code insertion. Another
area is improving the reduction order, to make the allocator less sensitive
to the reduction order.


There is no official plan; we started to discuss that with Lang some time
ago, but none of us had time to dive into it yet. Any help appreciated there





From: Jonas Paulsson [mailto:jonas.paulsson at ericsson.com] 
Sent: 04 March 2015 13:51
To: Lang Hames; Arnaud De Grandmaison
Cc: llvmdev at cs.uiuc.edu
Subject: PBQP spilling




I would like to ask about PBQPs use of InlineSpiller. The code output when
using PBQP gets a lot bigger compared to when using RegAllocGreedy. PBQP
does not split the live intervals, and a lot more (often redundant) reload
instructions are emitted as a result, it seems. I wonder why this is, and if
there are any plans to improve on this point? 


/Jonas Paulsson

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