https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80283
Michael_S <already5chosen at yahoo dot com> changed:
What |Removed |Added
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CC| |already5chosen at yahoo dot com
--- Comment #8 from Michael_S <already5chosen at yahoo dot com> ---
Hi
I am person that originated the issue. I didn't want to take part in the
discussion, but Markus convinced me.
I want to add a couple of point:
1. It seems to me that the issue is not specific to x64. It is more general and
could happen on any machine with 16 SIMD registers.
2. Here is a demonstration of the issue on ARMv7 Neon.
https://godbolt.org/g/e9A5Yi
As an example of proper code generation you can look (on the same Godbolt) at
code, generated by Visual C.
3. Markus argues that ARMv7 Neon issue differs from x64. He appears to think
so, because x64 issue is cured by -fno-tree-ter and ARMv7 issue is not.
I disagree. According to my understanding tree-ter processing is just a trigger
of the problem, not the cause of it. The cause has to be a broken optimizer
heuristics.
4. To prove my point that relationship between the problem and the tree-ter on
x64 is incidental, I reformatted an original code in slightly different manner
(was I imitating tree-ter ? May be. But I didn't look at tree-ter source
code).
Here is a variant that makes an issue to show on x64 with -fno-tree-ter.
https://godbolt.org/g/mSLiRZ
Best regards,
Michael
