Re: [gc-improv] Permanent vs function RTL obstack fix

[Jeff Law <law@redhat.com>]

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On 04/08/11 08:39, Richard Guenther wrote:
> On Fri, Apr 8, 2011 at 4:36 PM, Jeff Law <law@redhat.com> wrote:
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>> On 04/08/11 07:21, Laurynas Biveinis wrote:
>>> 2011/4/8 Steven Bosscher <stevenb.gcc@gmail.com>:
>>>>>        * stmt.c (label_rtx): Allocate RTX in permanent RTL memory.
>>>>
>>>> That looks strange, labels should be function specific, except
>>>> non-local labels. Maybe you can get away with allocating DECL_NONLOCAL
>>>> labels on the permanent rtl obstack?
>>>
>>> That's a good idea, I will try it once things are stable on the branch.
>>>
>>>> Perhaps a third, per-translation-unit obstack is necessary?
>>>
>>> Perhaps. After I finish with permanent rtl obstack, I will measure how
>>> large it gets and if it's worthwhile to split out
>>> per-translation-obstack out of it.
>> And then you'll want a per-statement obstack, then per-expression
>> obstack, and before you know it, GCC looks much like it did 20 years ago.
>>
>> Sigh.
> 
> I remember it was fast at that time though ;)
Yea, fast to segfault dereferencing a dangling pointer due to placing an
object on the wrong obstack.  And fast because we didn't have a good way
to keep most expressions beyond the lifetime of a single statement thus
preventing any kind of higher level analysis and optimization.

Jeff
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