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UMULH

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

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10011011110Rm0(1)(1)(1)(1)(1)RnRd
URa

64-bit

UMULH <Xd>, <Xn>, <Xm>

integer d = UInt(Rd);
integer n = UInt(Rn);
integer m = UInt(Rm);
integer a = UInt(Ra);           // ignored by UMULH/SMULH
integer destsize = 64;
integer datasize = destsize;
boolean unsigned = (U == '1');

Assembler Symbols

<Xd>

Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field.

<Xn>

Is the 64-bit name of the first general-purpose source register holding the multiplicand, encoded in the "Rn" field.

<Xm>

Is the 64-bit name of the second general-purpose source register holding the multiplier, encoded in the "Rm" field.

Operation

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

integer result;

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

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

Operational information

If PSTATE.DIT is 1:

  • The execution time of this instruction is independent of:
    • The values of the data supplied in any of its registers.
    • The values of the NZCV flags.
  • The response of this instruction to asynchronous exceptions does not vary based on:
    • The values of the data supplied in any of its registers.
    • The values of the NZCV flags.