Using the coprocessor

In this section:

• Introduction
• The execution environment
• The CODE/EDOC facility
• Mixing of Intel 32-bit Assembler and Fortran
• Labels
• Referencing Fortran variables
• Literals
• Halfword and byte forms of instructions
• Using the coprocessor
• Instruction prefixes
• Other assembler facilities
• Other machine-level facilities
• Error messages
• 64-bit assembler

Coprocessor stack operands are referred to using the following notation:

    ST(0) ;Stack top
    ST(1) ;Next to stack top
    etc.

Stack reference instructions use the short real form of the mnemonic (for example, FADD) but the actual calculations are performed to the full precision of the coprocessor. The coprocessor stack must be returned empty and with the control word unchanged. Coprocessor instructions do not contain an implied WAIT. WAIT instructions are only necessary after results are returned to the 32-bit Intel chip (FSTP, or FSTSWAX for example), and even then only if the result will be used before another coprocessor instruction is started.

If you are writing code that might be used in an another environment, you should ensure that any coprocessor mnemonics you use are appropriate to that environment.