stfdux

Store Floating-Point Double with Update Indexed

stfdux FRS,RA,RB

Stores the contents of a floating-point register into memory and updates the base address register.

Details

The contents of register FRS are stored into the double-word in storage addressed by EA. The effective address (EA) is the sum of the contents of registers RA and RB. If RA=0, the instruction form is invalid. EA is placed back into register RA.

Pseudocode Operation

if RA = 0 then
    b ← 0
else
    b ← (RA)
EA ← b + (RB)
MEM(EA, 8) ← (FRS)
RA ← EA

Programming Note

The base register (RA) is updated with the effective address after the memory access. RA must not be 0 and must differ from the destination register; violating this constraint produces undefined results.

Example

stfdux f1, r4, r5

Encoding

Binary Layout
0
0
FRS
6
RA
11
RB
16
 
Format X-form
Opcode 0x7C0005EE
Extension Floating-Point
Registers Altered FPSCR

Operands

  • FRS
    Floating-Point Register Source
  • RA
    General Purpose Register Address
  • RB
    General Purpose Register Index