https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
Pat Haugen changed:
What|Removed |Added
Status|NEW |RESOLVED
Resolution|---
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #12 from Pat Haugen ---
Testcase fix was committed in r236672. Does this pr need to be left open for
the subreg discussion or can it be closed?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #11 from Segher Boessenkool ---
No, please go ahead, I couldn't find an easy way out. The generic
code is hell-bent on using a subreg of the DF reg.
The backend won't necessarily use any nop here btw, but the testcase
should be pret
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #10 from Bill Schmidt ---
Great, thanks, Pat! Let's hold off for now, as Segher is checking out some
ideas.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #9 from Pat Haugen ---
(In reply to Bill Schmidt from comment #8)
> The test is verifying that we force some nops in between a store and load
> when we know they alias, to mitigate the cost of the stall while the load
> tries to get t
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #8 from Bill Schmidt ---
Even this test case isn't truly horrible for real-world code (it looks nastier
than it is, as stack stores tend to have minimal real cost). This is an issue
only on "older" processors; it's just that a lot of
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #7 from Richard Biener ---
Apart from this testcase do you see any negative impact in real-world code?
That said, the positive impact on real-world code will likely be detecting
some more byte-shuffling code plus lowpart-subregs plus
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #6 from Bill Schmidt ---
Yes, I see your point -- even if you query the RTX cost of the subreg, we're
just going to tell you it's one insn since the true expense doesn't show up
until reload. Seems like some invention will be require
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
Richard Biener changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #4 from rguenther at suse dot de ---
On May 11, 2016 3:52:43 PM GMT+02:00, "wschmidt at gcc dot gnu.org"
wrote:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
>
>--- Comment #3 from Bill Schmidt ---
>Sorry, accidentally saved b
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
--- Comment #3 from Bill Schmidt ---
Sorry, accidentally saved before finishing my thoughts.
How do we "inform" the middle-end that a DI subreg of a DF is very expensive?
This differs wildly by processor for us. We "can" always do the subreg,
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
Bill Schmidt changed:
What|Removed |Added
CC||dje at gcc dot gnu.org,
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71050
Richard Biener changed:
What|Removed |Added
Keywords||missed-optimization
Target Milestone|
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