[PATCH] D24039: Fixed spill stack objects are mutable

Philip Reames via llvm-commits llvm-commits at lists.llvm.org
Tue Aug 30 16:04:10 PDT 2016

reames added a comment.

In https://reviews.llvm.org/D24039#529494, @hfinkel wrote:

> In https://reviews.llvm.org/D24039#529406, @reames wrote:
> > At least per documentation, spill slots should be created via CreateSpillStackObject.  I think you may be fixing the wrong bug.  Even if not silently disabling all optimization for existing callers is not acceptable.
> I'm not quite sure that's right: Some ABIs have fixed-offset spill slots (e.g. PowerPC). Calling a spill slot immutable seems odd anyway, given that, by definition, you store into it. Also, they have isAliased == false regardless.

Hal, I think we have a terminology problem here.  To me a "spill slot" is one created by the register allocator when spilling vregs.  Are you saying that PowerPC has preassigned offsets which the register allocator must use?  Or are you referring to something else entirely?



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