Attached is the patch which does the following scheduler related changes. * re-models bdver3 decoder. * It enables lookahead with value 8 for all BD architectures. The patch doesn't consider if reloading is completed or not (an area that needs to be worked on). * The issue rate for BD architectures are set to 4.
I see the following performance improvements on bdver3 machine.
* GemsFDTD improves by 6-7% with lookahead value changed to 8.
* Hmmer improves by 9% when issue rate when set to 4 .
I have considered the following hardware details for the model.
* There are four decoders inside a hardware decoder block.
* These four independent decoders can execute in parallel. (They can take 8B
from four different instructions and decode).
* These four decoders are pipelined 4 cycles deep and are non-stalling.
* Each decoder takes 8B of instruction data every cycle and tries decoding it.
* Issue rate is 4.
Is it OK for upstream?
Changelog
========
2013-10-24 Ganesh Gopalasubramanian <ganesh.gopalasubraman...@amd.com>
* config/i386/bdver3.md : Added two additional decoder units
to support issue rate of 4 and remodeled vector unit.
* config/i386/i386.c (ix86_issue_rate): Issue rate for BD
architectures is set to 4.
* config/i386/i386.c (ia32_multipass_dfa_lookahead): DFA
lookahead is set to 8 for BD architectures.
Regards
Ganesh
bdver3_issue_rate_lookahead.patch
Description: bdver3_issue_rate_lookahead.patch
