[Patch ARM] Fix probe_stack constraint.

[Ramana Radhakrishnan <ramana dot radhakrishnan at foss dot arm dot com>]

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 to trunk.

Ramana

PR target/82248

* config/arm/arm.md (probe_stack) : Change to using the 'o' constraint.

Attachment: probe-stack.txt
Description: Text document