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RealView Assembler User's Guide
Preface Introduction Writing ARM Assembly Language Assembler Reference Command syntax
Obtaining a list of available options Specifying command‑line options with an environm AAPCS Floating‑point model Memory access attributes Pre‑executing a SET directive Splitting long LDMs and STMs Listing output to a file Project template options Controlling the output of diagnostic messages Controlling exception table generation Format of source lines Predefined register and coprocessor names Predeclared register names Predeclared extension register names Predeclared coprocessor names Built‑in variables and constants Symbols Symbol naming rules Variables Numeric constants Assembly time substitution of variables Labels Local labels Expressions, literals, and operators String expressions String literals Numeric expressions Numeric literals Floating‑point literals Register‑relative and program‑relative express Logical expressions Logical literals Operator precedence Unary operators Binary operators Diagnostic messages Interlocks IT block generation Thumb branch target alignment Using the C preprocessor ARM and Thumb Instructions Directives ReferenceOperator precedence
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| Home > Assembler Reference > Expressions, literals, and operators > Operator precedence | |||
The assembler includes an extensive set of operators for use in expressions. Many of the operators resemble their counterparts in high‑level languages such as C (see Unary operators and Binary operators).
There is a strict order of precedence in their evaluation:
Expressions in parentheses are evaluated first.
Operators are applied in precedence order.
Adjacent unary operators are evaluated from right to left.
Binary operators of equal precedence are evaluated from left to right.
The assembler order of precedence is not exactly the same as in C.
For example, (1 + 2 :SHR: 3) evaluates as (1 + (2 :SHR: 3)) = 1 in armasm. The equivalent expression in C evaluates as ((1 + 2) >> 3) = 0.
You are recommended to use brackets to make the precedence explicit.
If your code contains an expression that would parse differently in C, and you are not using the --unsafe option, armasm normally gives a warning:
A1466W: Operator precedence means that expression would evaluate differently in C
Table 3.4 shows the order of precedence of operators in armasm, and a comparison with the order in C (see Table 3.5).
From these tables:
The highest precedence operators are at the top of the list.
The highest precedence operators are evaluated first.
Operators of equal precedence are evaluated from left to right.
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