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4–110 Alpha Architecture Handbook
4.10.5 VAX Floating Add
Format:
Operation:
Fc ← Fav + Fbv
Exceptions:
Instruction mnemonics:
Qualifiers:
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.
ADDx Fa.rx,Fb.rx,Fc.wx
!Floating-point Operate format
Invalid Operation
Overflow
Underflow
ADDF Add F_floating
ADDG Add G_floating
Rounding: Chopped (/C)
Trapping: Exception Completion (/S)
Underflow Enable (/U)