smulh

Signed Multiply High

SMULH <Xd>, <Xn>, <Xm>

Multiplies two 64-bit registers, keeps high 64 bits.

Pseudocode Operation

result ← Xn * Xm
Xd ← result[127:64]
N ← unchanged
Z ← unchanged
C ← unchanged
V ← unchanged

Example

SMULH x0, x1, x2

Encoding

Binary Layout

1

31

00

30:29

11011

28:24

0

23

10

22:21

Rm

20:16

0

15

11111

14:10

Rn

9:5

Rd

4:0

 

Format Data Processing

Opcode 0x9B407C00

Extension Base

Operands

• Xd
  Destination 64-bit integer register
• Xn
  First source / base 64-bit integer register
• Xm
  Second source / offset 64-bit integer register

Related

More in Base

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x9B407C00	SMULH <Xd>, <Xn>, <Xm>		A64		1 | 00 | 11011 | 0 | 10 | Rm | 0 | 11111 | Rn | Rd
0x04120000	SMULH <Zdn>.<T>, <Pg>/M, <Zdn>.<T>, <Zm>.<T>		A64		00000100 | size | 0100 | 1 | 0 | 000 | Pg | Zm | Zdn
0x04206800	SMULH <Zd>.<T>, <Zn>.<T>, <Zm>.<T>		A64		00000100 | size | 1 | Zm | 0110 | 1 | 0 | Zn | Zd

Description

Signed Multiply High multiplies two 64-bit register values, and writes bits[127:64] of the 128-bit result to the 64-bit destination register.

Operation

bits(64) operand1 = X[n, 64];
bits(64) operand2 = X[m, 64];

integer result;

result = Int(operand1, FALSE) * Int(operand2, FALSE);

X[d, 64] = result<127:64>;