Datasheet

121
11011B–ATARM–21-Feb-12
SAM3N
10.14.2 UMULL, UMLAL, SMULL, and SMLAL
Signed and Unsigned Long Multiply, with optional Accumulate, using 32-bit operands and pro-
ducing a 64-bit result.
10.14.2.1 Syntax
op{cond} RdLo, RdHi, Rn, Rm
where:
op is one of:
UMULL Unsigned Long Multiply.
UMLAL Unsigned Long Multiply, with Accumulate.
SMULL Signed Long Multiply.
SMLAL Signed Long Multiply, with Accumulate.
cond is an optional condition code, see “Conditional execution” on page 84.
RdHi, RdLo are the destination registers.
For UMLAL and SMLAL they also hold the accumulating value.
Rn, Rm are registers holding the operands.
10.14.2.2 Operation
The UMULL instruction interprets the values from Rn and Rm as unsigned integers. It multiplies
these integers and places the least significant 32 bits of the result in RdLo, and the most signifi-
cant 32 bits of the result in RdHi.
The UMLAL instruction interprets the values from Rn and Rm as unsigned integers. It multiplies
these integers, adds the 64-bit result to the 64-bit unsigned integer contained in RdHi and RdLo,
and writes the result back to RdHi and RdLo.
The SMULL instruction interprets the values from Rn and Rm as two’s complement signed inte-
gers. It multiplies these integers and places the least significant 32 bits of the result in RdLo, and
the most significant 32 bits of the result in RdHi.
The SMLAL instruction interprets the values from Rn and Rm as two’s complement signed inte-
gers. It multiplies these integers, adds the 64-bit result to the 64-bit signed integer contained in
RdHi and RdLo, and writes the result back to RdHi and RdLo.
10.14.2.3 Restrictions
In these instructions:
• do not use SP and do not use PC
• RdHi and RdLo must be different registers.
10.14.2.4 Condition flags
These instructions do not affect the condition code flags.
10.14.2.5 Examples
UMULL R0, R4, R5, R6 ; Unsigned (R4,R0) = R5 x R6
SMLAL R4, R5, R3, R8 ; Signed (R5,R4) = (R5,R4) + R3 x R8