ARM汇编语言程序设计总结

Rotate Right Extended (RRX)

Rotate right extended is encoded with RRX in the Op2 field. The value of the Carry flag (C) is shifted into bit 31. The shifted out bit 0 is written to C.

Binary operators

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Home > Assembler Reference > Expressions, literals, and operators > Binary operators Binary operators are written between the pair of subexpressions they operate on.

Binary operators have lower precedence than unary operators. Binary operators appear in this section in order of precedence.

Note

The order of precedence is not the same as in C, see Operator precedence in armasm and C.

Multiplicative operators

Multiplicative operators have the highest precedence of all binary operators. They act only on numeric expressions.

Table 3.9 shows the multiplicative operators. Table 3.9. Multiplicative operators

Operator Alias Usage Explanation Multiply Divide A modulo B * / :MOD: A*B A/B A:MOD:B % String manipulation operators

Table 3.10 shows the string manipulation operators. In CC, both A and B must be strings. In the slicing operators LEFT and RIGHT:

A must be a string

? B must be a numeric expression.

?

Table 3.10. String manipulation operators

Operator Usage Explanation B concatenated onto the end of A The left-most B characters of A The right-most B characters of A :CC: :LEFT: A:CC:B A:LEFT:B :RIGHT: A:RIGHT:B

Shift operators

Shift operators act on numeric expressions, shifting or rotating the first operand by the amount specified by the second. Table 3.11 shows the shift operators. Table 3.11. Shift operators

Operator Alias Usage Explanation Rotate A left by B bits Rotate A right by B bits Shift A left by B bits Shift A right by B bits :ROL: :ROR: :SHL: :SHR: A:ROL:B A:ROR:B A:SHL:B A:SHR:B << >> Note

SHR is a logical shift and does not propagate the sign bit.

Addition, subtraction, and logical operators

Addition and subtraction operators act on numeric expressions.

Logical operators act on numeric expressions. The operation is performed bitwise, that is, independently on each bit of the operands to produce the result. Table 3.12 shows addition, subtraction, and logical operators. Table 3.12. Addition, subtraction, and logical operators

Operator Alias Usage Explanation Add A to B Subtract B from A Bitwise AND of A and B Bitwise Exclusive OR of A and B Bitwise OR of A and B + - :AND: :EOR: :OR:

A+B A-B A:AND:B A:EOR:B A:OR:B & ^ | Relational operators

Table 3.13 shows the relational operators. These act on two operands of the same type to produce a logical value. The operands can be one of:

? ? ? ?

numeric

program-relative register-relative strings.

Strings are sorted using ASCII ordering. String A is less than string B if it is a leading substring of string B, or if the left-most character in which the two strings differ is less in string A than in string B.

Arithmetic values are unsigned, so the value of 0>-1 is {FALSE}. Table 3.13. Relational operators

Operator Alias Usage Explanation = > >= < <= /=

== A=B A>B A>=B A != A/=B Boolean operators

These are the operators with the lowest precedence. They perform the standard logical operations on their operands.

In all three cases both A and B must be expressions that evaluate to either {TRUE} or

{FALSE}.

Table 3.14 shows the Boolean operators. Table 3.14. Boolean operators

Operator Alias Usage Explanation Logical AND of A and B Logical Exclusive OR of A and B Logical OR of A and B :LAND: && :LEOR: :LOR:

A:LAND:B A:LEOR:B A:LOR:B ||