AVR: Speed up IEEE double comparisons.

AVR: Speed up IEEE double comparisons.

IEEE double can be compared without first converting them to
the internal representation.

libgcc/config/avr/libf7/
	* libf7-common.mk (g_xdd_cmp): Remove le, lt, ge, gt, ne, eq, unord.
	(F7_ASM_PARTS): Add D_cmp, D_eq, D_ne, D_ge, D_gt, D_le, D_lt, D_unord.
	* libf7-asm.sx (D_cmp, D_eq, D_ne, D_ge, D_gt, D_le, D_lt, D_unord):
	New modules.
	* f7-wraps.h: Rebuild.

gcc/testsuite/
	* gcc.target/avr/cmpdi-1.c: New test.