stfdx
Store Floating-Point Double Indexed - 7C 00 00 5C
stfdx
Instruction Syntax
| Mnemonic | Format | Flags |
| stfdx | frS,rA,rB | None |
Instruction Encoding
0
1
1
1
1
1
S
S
S
S
S
A
A
A
A
A
B
B
B
B
B
0
0
0
0
0
0
0
0
0
0
0
| Field | Bits | Description |
| Primary Opcode | 0-5 | 011111 (0x1F) |
| frS | 6-10 | Source floating-point register |
| rA | 11-15 | Base register |
| rB | 16-20 | Index register |
| Reserved | 21-29 | 000000000 |
| Reserved | 30-31 | 00 |
Operation
EA ← (rA) + (rB) (EA) ← (frS)
The effective address is calculated by adding the base register to the index register. The double-precision floating-point value in the source register is stored at the effective address.
Note: The stfdx instruction stores a 64-bit double-precision floating-point value to memory using indexed addressing. The address must be aligned to an 8-byte boundary.
Affected Registers
Memory
- Double-precision floating-point value at effective address (EA)
Examples
Basic Store Floating-Point Double Indexed
# Store double-precision value using indexed addressing stfdx fr1, r3, r4 # Store fr1 at address r3 + r4
Array of Doubles with Dynamic Index
# Store double in array using dynamic index li r3, array # Load array base address li r4, 16 # Index = 16 (2 * 8 bytes) stfdx fr1, r3, r4 # Store double at array[2]
Dynamic Addressing
# Store double using dynamic index calculation li r3, base_addr # Load base address add r4, r5, r6 # Calculate index dynamically stfdx fr1, r3, r4 # Store double at base_addr + index