ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Assembler syntax
SMMLS{R} , , ,
where:
R If R is present, the multiplication is rounded.
If the R is omitted, the multiplication is truncated.
See Standard assembler syntax fields on page A8-7.
The destination register.
The register that contains the first multiply operand.
The register that contains the second multiply operand.
The register that contains the accumulate value.
Operation
if ConditionPassed() then
EncodingSpecificOperations();
result = (SInt(R[a])