0004-Model-Core-2-i7-decoder-bottleneck

[Maxim Kuvyrkov <maxim at codesourcery dot com>]

This patch makes the scheduler aware of decoder restrictions on Core 
2/i7.  It adds new hooks to multipass scheduling that allow the target 
to filter the search space from instructions that should not be tried in 
current [partial] solution of multipass scheduling.

The primary motivation of this patch is to model limited-size buffers, 
such as decoder fetch blocks, and, more generally, CPU pipeline features 
that are difficult to express in a DFA model.  For Core 2/i7 we need to 
model a 16-byte decoder buffer filled with variable-length instructions. 
 When the modelled buffer becomes nearly full the hooks remove 
instructions that would not fit the rest of the buffer from multipass 
scheduler consideration.

The patch does not affect behavior of targets that do not define the new 
hooks.

The patch touches both i386 backend and the haifa scheduler; the i386 
part is at the beginning of the patch and the target-independent changes 
are in the second part of the patch.

Tested by bootstrapping on i686-pc-linux-gnu, an earlier version was 
successfully regtested.  The patch shows 0.1-0.25% performance 
improvement on SPEC2000.  I'm now rerunning the SPEC2000 and SPEC2006 
benchmarks and will post the final results in a day or so.

Your approvals and comments are welcome.

OK to commit?

Thank you,

--
Maxim Kuvyrkov
CodeSourcery
maxim@codesourcery.com
(650) 331-3385 x724

Attachment: 0004-Model-Core-2-i7-decoder-bottleneck.ChangeLog
Description: Text document

Attachment: 0004-Model-Core-2-i7-decoder-bottleneck.patch
Description: Text document