Compiler: Assembly conditional compilation for ARM Cortex M4

Guy Mardiks

Genius 4135 points

Tool/software: TI C/C++ Compiler

Hello,

What is to proper syntax in assembly (TI ARM tools) to achieve the same result as:

#if defined(AAA) || defined(BBB)

for single check the following seem to work

.if $$defined(AAA)

but i did not find how to do the OR operation (similar syntax as in C above did not work)

Thanks

Guy

over 7 years ago

0 Guy Mardiks over 7 years ago

Genius 4135 points

Hi,
It seems that for Assembly it works if doing it with only one | (binary or between both defined - each interpreted as 0 or 1.

0 George Mock over 7 years ago in reply to Guy Mardiks

TI__Guru**** 249260 points

You are correct. But I want to clarify one thing. Note that || evaluation stops if the first operand is true. With |, both operands are always evaluated. In this particular context, this distinction rarely makes a meaningful difference. But I thought I would point it out anyway.

Thanks and regards,

-George

0 Guy Mardiks over 7 years ago in reply to George Mock

Genius 4135 points

Hi, Thanks a lot for your comment.
Do you know if there is syntax to achieve the || (logical) "effect" in assembly?

Thanks
Guy

0 George Mock over 7 years ago in reply to Guy Mardiks

TI__Guru**** 249260 points

Guy Mardiks said:
if there is syntax to achieve the || (logical) "effect" in assembly?

Unfortunately, no.

Thanks and regards,

-George

0 Archaeologist over 7 years ago in reply to George Mock

TI__Guru* 84285 points

The "defined" operator is guaranteed to return a 0 or 1, and can't have any side effects, so for this particular expression, the | operator is exactly equivalent to a hypothetical || operator. This is true for many assembly preprpocessor expressions; if all of the subexpressions are either 0 or 1, and you don't have any side effects, bitwise | is equivalent to logical ||

0 Guy Mardiks over 7 years ago in reply to Archaeologist

Genius 4135 points

Thanks you.

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Compiler: Assembly conditional compilation for ARM Cortex M4