MULH

Multiply High Signed

MULH rd, rs1, rs2

Performs a signed multiplication and stores the upper bits of the result.

Encoding

Binary Layout

0000001

31:25

rs2

24:20

rs1

19:15

001

14:12

rd

11:7

0110011

6:0

 

Format R-Type

Opcode 0x02001033

Extension M

Operands

• rd
  Dest (Upper Bits)
• rs1
  Source register 1 (integer)
• rs2
  Source register 2 (integer)

Example

MULH x5, x6, x7

// Get upper bits of signed multiplication.

Related

Across architectures

Integer Multiply : how x86, ARM, RISC-V, and PowerISA each do this.

More in M

Reference

View in RISC-V Unprivileged ISA Specification ↗ RISC-V ISA Manual

Description

MULH multiplies rs1 and rs2 as signed values and writes the upper XLEN bits of the 2×XLEN-bit product to rd.

Operation

R[rd] = (sext(R[rs1]) * sext(R[rs2])) >> XLEN;