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Restoring Resister Values

Note: This was originally posted on 17th March 2011 at http://forums.arm.com

Hi,
I am working with Cortex M3 and I wrote a program in which I am calling a C function that is implemented in Assembly language. Four parameters are passed to the function, which are assigned to the Registers R0-R3. After performing some calculations on R0-R3 in the subroutine implemented in assembly language, when I return back to the C function the values of the R0-R3 are not the same as at the function's entry point rather R0-R3 contain results of the calculations performed in the subroutines. How can I get the same values back as they were at the starting point of the function call?
Looking forward for some useful hint.
Thanks and Regards

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Etienne SOBOLE over 12 years ago

Note: This was originally posted on 17th March 2011 at http://forums.arm.com

PUSH {r4,lr} ;// Preserve return address (r4 also pushed to maintain SP alignment)

Interesting.
Is it really usefull.
I assume that the alignment is usefull to push double (for example) on the next call.

I'll have a look at what gcc do...
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Etienne SOBOLE over 12 years ago

Note: This was originally posted on 17th March 2011 at http://forums.arm.com

PUSH {r4,lr} ;// Preserve return address (r4 also pushed to maintain SP alignment)

Interesting.
Is it really usefull.
I assume that the alignment is usefull to push double (for example) on the next call.

I'll have a look at what gcc do...
Cancel
Vote up 0 Vote down

Cancel

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