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

State Accepted Answer
Locked Locked
Replies 4 replies
Answers 1 answer
Subscribers 349 subscribers
Views 5189 views
Users 0 members are here

2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options

How was your experience today?

This discussion has been locked.

You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Why thumb code can only access r0-r7?

Wenchuan2018 over 6 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

Top replies

42Bastian Schick over 6 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.

Parents

0 Wenchuan2018 over 6 years ago in reply to ramarao91

Thanks.

I only concern about Thumb-2. As Bastian said it supports full access. So...
Cancel
Vote up 0 Vote down

Cancel

Reply

0 Wenchuan2018 over 6 years ago in reply to ramarao91

Thanks.

I only concern about Thumb-2. As Bastian said it supports full access. So...
Cancel
Vote up 0 Vote down

Cancel

Children

No data