Bug 486223

=Comment: #0=================================================
Hans-Georg Markgraf <mgrf.com> - 
1. Feature Overview:
Feature Id:	[201837]
a. Name of Feature:	Exploit byte swap instructions lrv, lrvg

b. Feature Description
Provides exploitation for the hardware instructions in System z architecture for performing byte
swap operations on memory and register operands. In order to make use of it the instructions have to
be integrated in the GCC back end machine description file. The instruction then is used for
implementing the GCC specific bswap family of builtins. That way programmers can directly trigger
usage of the instruction. Although this is useful for programmers aware of these builtins a better
way is to enable GCC to be able to recognized "manual" byte swapping implementations as well. In
order to do so GCC has to deal with combinations of shift and or operations which appear when
someone implements byte swapping "by hand". The item also covers the GCC enhancement which are
necessary to recognized these patterns and map it to a hardware byte swapping implementation.

2. Feature Details:
Sponsor:	zSeries
Architectures:
s390x

Arch Specificity: Purely Arch Specific Code
Affects Toolchain: Yes
Delivery Mechanism: Backport
Category:	Toolchain
Request Type:	Toolchain - Enhancement from IBM
Documentation work: yes

d. Upstream Acceptance:	Submitted
Sponsor Priority	1
f. Severity: High
IBM Confidential:	no
Code Contribution:	IBM code
g. Component Version Target:	gcc 4.5

3. Business Case
This feature provides improved performance by using a HW instruction for commonly used task, not
only manually triggered by the programmed, but also automatically when the compiler sense the pattern.

4. Primary contact at Red Hat: 
John Jarvis
jjarvis

5. Primary contacts at Partner:
Project Management Contact:
Hans-Georg Markgraf, mgrf.com, Boeblingen 49-7031-16-3978

Technical contact(s):
Gonzalo Muelas Serrano, gmuelas.com

IBM Manager:
Thomas Schwarz, t.schwarz.com