How to align objects on stack?

Clemens Eisserer

Hi,

I am using CGT-7.4.8 for C66x and would like to align objects allocated on stack, so I can use intrinsics for aligned memory access. I tried to use the same synthax as for global objects:

void function() {
int someArray[10];
#pragma DATA_ALIGN (someArray, 8);
}

However, in this case I get the warning, that the DATA_ALIGN pragma can only be applied to file-level symbols.
Is there any way to make sure, local variables/arrays are aligned to double-word addresses?

Thank you in advance, Clemens

over 11 years ago

0 George Mock over 11 years ago

TI__Guru**** 251230 points

The compiler automatically aligns all arrays, even function local arrays, so that the aligned memory access instructions can be used. Please see the section titled Base Address of an Array in the C6000 compiler manual.

Thanks and regards,

-George

0 Alberto Chessa over 11 years ago

Mastermind 6670 points

Hi,

See compiler manual § Data Type storage, there is a note about array:

For C6400,C6400+,C6740,andC6600,aligned to a 64-bit boundary [...]

So maybe your array i s already aligned. Anyway, the __attribute__((aligned(64))) should work (enable gcc exetension in compiler option)

0 Clemens Eisserer over 11 years ago in reply to Alberto Chessa

Expert 2430 points

> The compiler automatically aligns all arrays, even function local arrays,
> so that the aligned memory access instructions can be used.

Thanks a lot for the clarification :)

> So maybe your array i s already aligned.

I always thought it simply worked by accident, glad to know this is guaranteed by the compiler.

Thanks & best regards, Clemens

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How to align objects on stack?