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AIX Version 4.3 Assembler Language Reference

fneg (Floating Negate) Instruction


Negates the contents of a floating-point register and places the result into another floating-point register.


fneg FRT,FRB
fneg. FRT,FRB


The fneg instruction places the negated contents of floating-point register FRB into the target FPR FRT.

The fneg instruction has two syntax forms. Each syntax form has a different effect on Condition Register Field 1.

Syntax Form Floating-Point Status and Control Register Record Bit (Rc) Condition Register Field 1
fneg None 0 None
fneg. None 1 FX,FEX,VX,OX

The two syntax forms of the fneg instruction never affect the Floating-Point Status and Control Register. If the syntax form sets the Record (Rc) bit to 1, the instruction affects the Floating-Point Exception (FX), Floating-Point Enabled Exception (FEX), Floating-Point Invalid Operation Exception (VX), and Floating-Point Overflow Exception (OX) bits in Condition Register Field 1.


FRT Specifies target floating-point register for operation.
FRB Specifies source floating-point register for operation.


  1. The following code negates the contents of FPR 5 and places the result into FPR 6:
    # Assume FPR 5 contains 0x400C 0000 0000 0000.
    fneg 6,5
    # FPR 6 now contains 0xC00C 0000 0000 0000.
  2. The following code negates the contents of FPR 4, places the result into FPR 6, and sets Condition Register Field 1 to reflect the result of the operation:
    # Assume FPR 4 contains 0xC053 4000 0000 0000.
    fneg. 6,4
    # FPR 6 now contains 0x4053 4000 0000 0000.
    # CR now contains 0x0000 0000.

Related Information

Floating-Point Processor.

Floating-Point Move Instructions.

Interpreting the Contents of a Floating-Point Register.

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