Floating Point

All 80387 floating point types except packed BCD are supported. (BCD support may be added without much difficulty). These data types are 16-, 32-, and 64- bit integers, and single (32-bit), double (64-bit), and extended (80-bit) precision floating point. Each supported type has an opcode suffix and a constructor associated with it. Opcode suffixes specify operand's data types. Constructors build these data types into memory.

• Floating point constructors are `.float' or `.single', `.double', and `.tfloat' for 32-, 64-, and 80-bit formats. These correspond to opcode suffixes `s', `l', and `t'. `t' stands for temporary real, and that the 80387 only supports this format via the `fldt' (load temporary real to stack top) and `fstpt' (store temporary real and pop stack) instructions.
• Integer constructors are `.word', `.long' or `.int', and `.quad' for the 16-, 32-, and 64-bit integer formats. The corresponding opcode suffixes are `s' (single), `l' (long), and `q' (quad). As with the temporary real format the 64-bit `q' format is only present in the `fildq' (load quad integer to stack top) and `fistpq' (store quad integer and pop stack) instructions.

Register to register operations do not require opcode suffixes, so that `fst %st, %st(1)' is equivalent to `fstl %st, %st(1)'.

Since the 80387 automatically synchronizes with the 80386 `fwait' instructions are almost never needed (this is not the case for the 80286/80287 and 8086/8087 combinations). Therefore, as suppresses the `fwait' instruction whenever it is implicitly selected by one of the `fn...' instructions. For example, `fsave' and `fnsave' are treated identically. In general, all the `fn...' instructions are made equivalent to `f...' instructions. If `fwait' is desired it must be explicitly coded.