re PR target/39228 (387 optimised __builtin_isinf() gives incorrect result)

	PR target/39228
	* config/i386/i386.md (isinfxf2): Split from isinf<mode>2.
	(UNSPEC_FXAM_MEM): New unspec.
	(fxam<mode>2_i387_with_temp): New insn and split pattern.
	(isinf<mode>2): Use MODEF mode iterator.  Force operand[1] through
	memory using fxam<mode>2_i387_with_temp to remove excess precision.

testsuite/ChangeLog:

	PR target/39228
	* gcc.c-torture/execute/pr39228.c: New test.

From-SVN: r144293