Syntax

              .ifcondition

             [.elseifcondition]

             [.else]

             .endif

Description

The .if directive marks the beginning of a conditional block. The condition is required.

• If the expression evaluates to true (nonzero), the assembler assembles the code that follows the expression (up to a .elseif, .else, or .endif).
• If the expression evaluates to false (0), the assembler assembles code that follows a .elseif (if present), .else (if present), or .endif (if no .elseif or .else is present).

The .elseif directive identifies a block of code to be assembled when the .if expression is false (0) and the .elseif expression is true (nonzero). When the .elseif expression is false, the assembler continues to the next .elseif (if present), .else (if present), or .endif (if no .elseif or .else is present). The .elseif is optional in a conditional block, and more than one .elseif can be used. If an expression is false and there is no .elseif, the assembler continues with the code that follows a .else (if present) or a .endif.

The .else directive identifies code the assembler assembles when the .if expression and all .elseif expressions are false (0). The .else directive is optional; if an expression is false and there is no .else statement, the assembler continues with the code that follows the .endif. The .elseif and .else directives can be used in the same conditional block.

The .endif directive terminates a conditional block.

See Section 5.10.2 for information about relational operators.

Example

This example shows conditional assembly:

       1        0001  SYM1   .set    1
       2        0002  SYM2   .set    2
       3        0003  SYM3   .set    3
       4        0004  SYM4   .set    4
       5              
       6              If_4:  .if     SYM4 = SYM2 * SYM2
       7 000000 0004         .byte   SYM4       ; Equal values
       8                     .else
       9                     .byte   SYM2 * SYM2 ; Unequal values
      10                    .endif
      11              
      12              If_5:  .if     SYM1 <= 10
      13 000001 000A         .byte   10       ; Less than / equal
      14                     .else
      15                     .byte   SYM1     ; Greater than
      16                     .endif
      17              
      18              If_6:  .if     SYM3 * SYM2 != SYM4 + SYM2
      19                     .byte   SYM3 * SYM2  ; Unequal value
      20                     .else
      21 000002 0008         .byte   SYM4 + SYM4  ; Equal values
      22                     .endif
      23              
      24              If_7:  .if SYM1 = 2
      25                     .byte   SYM1
      26                     .elseif SYM2 + SYM3 = 5
      27 000003 0005         .byte   SYM2 + SYM3
      28                     .endif