4.10.5 VAX Floating Add

Format:

ADDxFa.rx,Fb.rx,Fc.wx!Floating-point Operate format

Operation:

Fc Fav + Fbv

Exceptions:

Invalid Operation

Overflow

Underflow

Instruction mnemonics:

ADDF

Add F_floating

ADDG

Add G_floating

Qualifiers:

Rounding:

Chopped (/C)

Trapping:

Exception Completion (/S)

 

Underflow Enable (/U)

Description:

Register Fa is added to register Fb, and the sum is written to register Fc.

The sum is rounded or chopped to the specified precision, and then the corresponding range is checked for overflow/underflow. The single-precision operation on canonical single-precision values produces a canonical single-precision result.

An invalid operation trap is signaled if either operand has exp=0 and is not a true zero (that is, VAX reserved operands and dirty zeros trap). The contents of Fc are UNPREDICTABLE if this occurs. See Section 4.7.7 for details of the stored result on overflow or underflow.

4–110Alpha Architecture Handbook

Page 166
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Compaq ECQD2KCTE manual VAX Floating Add, Addf