AArch64: Add isfinite expander [PR 66462]

AArch64: Add isfinite expander [PR 66462]

Add an expander for isfinite using integer arithmetic.  This is
typically faster and avoids generating spurious exceptions on
signaling NaNs.  This fixes part of PR66462.

int isfinite1 (float x) { return __builtin_isfinite (x); }

Before:
	fabs    s0, s0
	mov     w0, 2139095039
	fmov    s31, w0
	fcmp    s0, s31
	cset    w0, hi
	eor     w0, w0, 1
	ret

After:
	fmov    w1, s0
	mov     w0, -16777216
	cmp     w0, w1, lsl 1
	cset    w0, hi
	ret

gcc:
	PR middle-end/66462
	* config/aarch64/aarch64.md (isfinite<mode>2): Add new expander.

gcc/testsuite:
	PR middle-end/66462
	* gcc.target/aarch64/pr66462.c: Add tests for isfinite.