The current code treats floating-point constant as integer
and does not treat fcmp/fcmpe as the comparison instrucitons
that requires special handling.

The fix corrects the type of immediate arguments and adds fcmp/fcmpe
in the special handing.

Uncomment the fcmp/fcmpe cases.

Fixes #21567
Change-Id: I6782520e2770f6ce70270b667dd5e68f71e2d5ad
Reviewed-on: https://go-review.googlesource.com/57852
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>