Figure 1. mulh
Description
Multiplies the contents of registers rA and rB and puts the result in register rD. This is a 32-bit by 32-bit signed multiplication that will produce a 64-bit result. The most significant word of this value is placed in rD. The least significant word is discarded.
Pseudocode
(rD) ← MSW( (rA) × (rB) ), signed
Registers Altered
- rD
Latency
- 1 cycle with
C_AREA_OPTIMIZED
=0 or 2 - 3 cycles with
C_AREA_OPTIMIZED
=1
Notes
- This instruction is only valid if the target architecture has multiplier
primitives, and if present, the MicroBlaze parameter
C_USE_HW_MUL
is set to 2 (Mul64). - When MULH is used, bit 30 and 31 in the MUL instruction must be zero to distinguish between the two instructions. In previous versions of MicroBlaze, these bits were defined as zero, but the actual values were not relevant.