[Patch ARM] Fix probe_stack constraint.

[Patch ARM] Fix probe_stack constraint.

The probe_stack pattern uses r0 as a fixed register. This can cause issues if we have auto-increment instructions coming out that have r0 as the base register.

Tested with a bootstrap and regression run. richi reports that the original issue was fixed in the run. I did consider whether probe_stack_range was affected but it all comes back to probe_stack pattern so I think we are ok.

I don't have a testcase that seems to provoke this but it seems to be default on most distributions so I'm expecting the testcoverage to come from there.

Applied.

Ramana

PR target/82248

* config/arm/arm.md (probe_stack) : Use the 'o' constraint.

From-SVN: r255428