Index

MSUBPT

Multiply-Subtract checked pointer multiplies two register values, subtracts the product from a third register value, and writes the result to the destination register. The intermediate product is treated as the offset.

If the operation would have generated a result where the most significant 8 bits of the result register differ from the most significant 8 bits of the base register, then the result is modified such that it is likely to be non-canonical when used as an address.

If the intermediate product cannot be correctly represented as a 64-bit two's complement value, then the result is modified such that it is likely to be non-canonical when used as an address.

Integer
(FEAT_CPA)

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 0 0 1 1 0 1 1 0 1 1 Rm 1 Ra Rn Rd
o0

MSUBPT <Xd>, <Xn>, <Xm>, <Xa>

if !IsFeatureImplemented(FEAT_CPA) then UNDEFINED;
integer d = UInt(Rd);
integer n = UInt(Rn);
integer m = UInt(Rm);
integer a = UInt(Ra);

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.
<Xa>

Is the 64-bit name of the third general-purpose source register holding the minuend, encoded in the "Ra" field.

Operation

bits(64) operand1 = X[n, 64];
bits(64) operand2 = X[m, 64];
bits(64) operand3 = X[a, 64];

bits(64) result;

integer product = SInt(operand1) * SInt(operand2);

// Signed and unsigned twos complement arithmetic are equivalent if only a
// fixed number of bits are considered.
result = operand3 - product<63:0>;
boolean overflow = (product != SInt(product<63:0>));
result = PointerMultiplyAddCheck(result, operand3, overflow);

X[d, 64] = result;