re PR target/20421 (387 mode switching clobbers flags)

	PR target/20421
	* config/i386/i386.md (frndintxf2_floor, frndintxf2_ceil)
	(frndintxf2_trunc, frndintxf2_mask_pm): Add FLAGS_REG clobber.
	Allocate local stack slots here.  Set ix86_optimize_mode_switching.
	flag here. Implement using define_insn_and_split.
	(frndintxf2_floor_i387, frndintxf2_ceil_i387, frndintxf2_trunc_i387)
	(frndintxf2_mask_pm_i387): New insn patterns.
	(floorsf2, floordf2, floorxf2): Remove local stack slot allocations.
	Do not set ix86_optimize_mode_switching flag.
	(ceilsf2, ceildf2, ceilxf2): Same.
	(btruncsf2, btruncdf2, btruncxf2): Same.
	(nearbyintsf2, nearbyintdf2, nearbyintxf2): Same.

From-SVN: r97604