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<u>Local labels</u><br /><br />A local label is a number in the range 0-99, optionally followed by a name. The same number can be used for more than one local label in an ELF section.<br /><br />Local labels are typically used for loops and conditional code within a routine, or for small subroutines that are only used locally. They are particularly useful in macros.<br /><br />You can use the same number for more than one local label even within the same scope.<br /><br />By default, the assembler links a local label reference to:<br />. the most recent local label of the same number, if there is one within the scope<br />. the next following local label of the same number, if there is not a preceding one within the scope.<br /><br />Use the optional parameters to modify this search pattern if required.<br /><br /><b>Syntax</b><br /><br />The syntax of a <u>local label</u> is:<br /><i>n{routname}</i><br />The syntax of a <u>reference to a local label</u> is:<br /><i>%{F|B}{A|T}n{routname}</i><br /><br />where:<br /><br />n is the <u>number</u> of the local label.<br />routname is the <u>name</u> of the current scope.<br />% introduces the reference.<br />F instructs the assembler to search <u>forwards</u> only.<br />B instructs the assembler to search <u>backwards</u> only.<br />A instructs the assembler to search <u>all</u> macro levels.<br />T instructs the assembler to look at <u>this</u> macro level only.<br /><br />If neither F or B is specified, the assembler searches backwards first, then forwards.<br />If neither A or T is specified, the assembler searches all macros from the current level to the top level, but does not search lower level macros.<br /><br />从你给出的代码：<br /> ldr r4 , =0xff<br />01 subs r4 , r4 , #0x01<br /> bne %b01<br />%b01的意思恐怕是向backwark搜索标号01
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