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Re: basic asm and memory clobbers


On Mon, Nov 23, 2015 at 09:48:42PM -0700, Jeff Law wrote:
> On 11/23/2015 07:22 PM, Segher Boessenkool wrote:
> >
> >Here is a test that shows that on at least PowerPC the basic asm is
> >identical to the extended asm without clobber (compile with -O2 -S and
> >-fno-ipa-icf if you want to have it easier to read).  In this case,
> >the basic asm is treated as not clobbering memory at the tree level
> >already, before expanding to RTL.
> And that IMHO, ought to be considered a bug.

I agree.  Almost everyone does, as far as I can see.

The question is if we want to retain this functionality.  No one has
depended on this in a long time -- they couldn't, it has been broken
since forever -- and there is another mechanism that does reliably
give this functionality (extended asm).

The first pass that goes wrong for this testcase is fre2, fwiw.


Segher


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