Architectures and Processors forum Why thumb code can only access r0-r7?

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Why thumb code can only access r0-r7?

Wenchuan2018 over 7 years ago

Hi Sir,

I want to know why thumb code can only access r0-r7, which described in ATPCS?

Thanks and best regards,

Wenchuan

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42Bastian Schick over 7 years ago +1 verified

Because the ISA is defined like this. Take a change to read the ARM Architecure Reference Manual (ARM ARM) BTW: Only the Original Thumb and ARMv6-M, Thumb-2 allows full access.

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0 Wenchuan2018 over 7 years ago in reply to ramarao91

Thanks.

I only concern about Thumb-2. As Bastian said it supports full access. So...
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0 Wenchuan2018 over 7 years ago in reply to ramarao91

Thanks.

I only concern about Thumb-2. As Bastian said it supports full access. So...
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