Texas Instruments TMS320C54x, User Manual

Page: 190 / 469

Macro Parameters/Substitution Symbols
5-10
Example 5–5 shows built-in substitution symbol functions.
Example 5–5. Using Built-In Substitution Symbol Functions
.asg label, ADDR ; ADDR = label
.if ($symcmp(ADDR,”label”) = 0); evaluates to true
SUB ADDR, A
.endif
.asg
”x,y,z” , list ; list = x,y,z
.if ($ismember(ADDR,list)) ; addr = x, list = y,z
SUB ADDRA, A ; sub x
.endif
5.3.4 Recursive Substitution Symbols
When the assembler encounters a substitution symbol, it attempts to
substitute the corresponding character string. If that string is also a substitution
symbol, the assembler performs substitution again. The assembler continues
doing this until it encounters a token that is not a substitution symbol or until
it encounters a substitution symbol that it has already encountered during this
evaluation.
In Example 5–6, the x is substituted for z; z is substituted for y; and y is
substituted for x. The assembler recognizes this as infinite recursion and
ceases substitution.
Example 5–6. Recursive Substitution
.asg ”x”,z ; declare z and assign z = ”x”
.asg ”z”,y ; declare y and assign y = ”z”
.asg ”y”,x ; declare x and assign x = ”y”
add x, A
* add x, A ; recursive expansion