Propeller Manual

SUBSX – Assembly Language Reference
SUBSX
Instruction: Subtract signed value plus C from another signed value.
SUBSX SValue1, 〈#〉 SValue2
Result: Difference of signed SValue1, and signed SValue2 plus C flag, is stored in SValue1.
•
SValue1 (d-field) is the register containing the value to subtract SValue2 plus C from,
and is the destination in which to write the result.
•
SValue2 (s-field) is a register or a 9-bit literal whose value plus C is subtracted from
SValue1.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
110111 001i 1111 ddddddddd sssssssss
Z & (D–(S+C) = 0) Signed Overflow Written 4
Concise Truth Table:
In Out
Destination Source Z C Effects Destination Z C
$0000_0001; 1 $0000_0001; 1 0 0
wz wc
$0000_0000; 0 0 0
$0000_0001; 1 $0000_0001; 1 1 0
wz wc
$0000_0000; 0 1 0
$0000_0001; 1 $0000_0001; 1 x 1
wz wc
$FFFF_FFFF; -1 0 0
$FFFF_FFFF; -1 $FFFF_FFFF; -1 0 0
wz wc
$0000_0000; 0 0 0
$FFFF_FFFF; -1 $FFFF_FFFF; -1 1 0
wz wc
$0000_0000; 0 1 0
$FFFF_FFFF; -1 $FFFF_FFFF; -1 x 1
wz wc
$FFFF_FFFF; -1 0 0
$8000_0001; -2,147,483,647 $0000_0001; 1 x 0
wz wc
$8000_0000; -2,147,483,648 0 0
$8000_0001; -2,147,483,647 $0000_0001; 1 x 1
wz wc
$7FFF_FFFF; 2,147,483,647 0 1
$7FFF_FFFF; 2,147,483,647 $FFFF_FFFF; -1 x 0
wz wc
$8000_0000; -2,147,483,648 0 1
$7FFF_FFFF; 2,147,483,647 $FFFF_FFFF; -1 x 1
wz wc
$7FFF_FFFF; 2,147,483,647 0 0
Explanation
SUBSX (Subtract Signed, Extended) subtracts the signed value of SValue2 plus C from
SValue1, and stores the result into the SValue1 register. The
SUBSX instruction is used to
perform signed multi-long subtraction; 64-bit subtractions, for example.
In a signed multi-long operation, the first instruction is unsigned (ex:
SUB), any middle
instructions are unsigned, extended (ex:
SUBX), and the last instruction is signed, extended
Page 352 · Propeller Manual v1.1