[PATCH, IRA]: Fix PR 48927 - Issues with "enable" attribute and IRA register preferences

[Uros Bizjak <ubizjak at gmail dot com>]

Hello!

Attached patch fixes changed register allocation where "enabled"
attribute is used. The core of the problem was with IRA, where IRA
does not look at "enabled" attribute when scanning through
alternatives string to perform various tasks (including register
allocation preferences).

Attached patch teaches IRA to handle "enabled" attribute. In effect,
the patch skips current alternative in the same way as when "#"
character is found.

2011-05-08  Uros Bizjak  <ubizjak@gmail.com>

	PR rtl-optimization/48927
	* ira-conflicts.c (commutative_constraint_p): Use
	recog_data.alternative_enabled_p to disable alternatives where
	"enabled" attribute is false.
	(get_dup_num): Ditto.
	* ira-lives.c (single_reg_class): Ditto.
	(ira_implicitly_set_insn_hard_regs): Ditto.

Patch was bootstrapped and regression tested on x86_64-pc-linux-gnu
{,-m32} with and without -with-fpmath=avx. Also, the patch fixes both
i386 scan-asm failures when the patch to merge *vec_concatv4si_1_avx
and *vec_concatv4si_1 patterns is applied (please see the PR [1] for
details).

OK for mainline?

[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48927

Uros.

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