i386.md: Comments on fma4 instruction selection reflect requirement on register press...

i386.md: Comments on fma4 instruction selection reflect requirement on register pressure...

2012-09-12  Ganesh Gopalasubramanian  <Ganesh.Gopalasubramanian@amd.com>

	* config/i386/i386.md : Comments on fma4 instruction
	selection reflect requirement on register pressure based
	cost model.

	* config/i386/driver-i386.c (host_detect_local_cpu): fma4
	flag is set-reset as informed by the cpuid flag.

	* config/i386/i386.c (processor_alias_table): fma4
	flag is enabled for bdver2.

From-SVN: r191226