The Mitsubishi D30V version of as has a few machine dependent options.
The D30V can often execute two sub-instructions in parallel. When this option is used, as will attempt to optimize its output by detecting when instructions can be executed in parallel.
When this option is used, as will issue a warning every time it adds a nop instruction.
When this option is used, as will issue a warning if it needs to insert a nop after a 32-bit multiply before a load or 16-bit multiply instruction.