Generate an architecturally undefined instruction. An attempt to execute an undefined instruction causes the Undefined instruction exception. Architecturally undefined instructions are expected to remain undefined.
SyntaxUND{cond}{.W} {#expr}
where:
condis an optional condition code.
.Wis an optional instruction width specifier.
exprevaluates to a numeric value. Table 13 shows the range and encoding of
exprexprIf
exprTable 13. Range and encoding of
exprInstruction
Encoding
Number of bits for
exprRange
ARM
0xV7FYYYFY
16
0-65535
32-bit Thumb
0xF7FYAYFY
12
0-4095
16-bit Thumb
0xDEYY
8
0-255
You can use the .W width specifier to force UND to
generate a 32-bit instruction in Thumb code on ARMv6T2 and above
processors. UND.W always generates a 32-bit instruction,
even if expr
- Reference:
PDF version