[PATCH, rs6000] Fix alias set of link reg save MEM

Segher Boessenkool segher@kernel.crashing.org
Wed Jun 2 14:19:55 GMT 2021


On Wed, Jun 02, 2021 at 08:23:48AM -0500, Pat Haugen wrote:
> On 6/2/21 7:01 AM, Richard Biener wrote:
> > So did you check the RTL (and alias-sets) produced by
> > __builtin_return_address?  Test coverage might
> > be low here and w/o scheduling opportunities to break things.
> 
> __builtin_return_address creates it's own copy of the link reg to a pseudo upon function entry. It doesn't appear to try and "reuse" any LR copy/save location that might be generated via the prolog code. References to __builtin_return_address will then refer to that pseudo. So I don't see any connection between the prolog save code and __builtin_return_address.

That is for __builtin_return_address(0), the simple (and always working)
one.  It is harder for non-zero arguments (although I don't see why
those would not work, even with inlining).


Segher


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