I would like to echo Sun's comments. Please write a
design document that describes your enhancement
and send it out.
Also, today is the last day for unrestricted checkins
before we enter "only bug fixes" mode in preparation
for the 4.2.4 release. So, I would suggest either
waiting to checkin your change or to checkin into
a branch.
- Suneel
On Sun, Jan 30, 2011 at 9:48 PM, Sun Chan <sun.c...@gmail.com> wrote:
> this change is quite large. Other than the obvious cosmetic issues
> like "random spacing", bad variable names like "sentive", there is not
> much a gatekeeper can do. Also, the IPA already does call site
> specific inlining, and you are introducing a new term context
> sensitive inlining, not sure what you meant. Please clarify.
> I suggest (if you haven't done so already) a code/design review
> instead of this code review request
> Sun
>
> On Mon, Jan 31, 2011 at 12:38 PM, Hui Shi <kalin....@gmail.com> wrote:
>> Hi folks,
>>
>>
>>
>> This is a patch for nystrom alias analysis, solve points to when inline
>> happens.
>>
>> Can gatekeeper help check this patch?
>>
>>
>>
>> Current nystrom points to analysis is context insensitive, field sensitive
>> and performed before inline during IPA.
>>
>> (nystrom is supposed to context sensitive finally)
>>
>> The problem found in following example is, after inline bar into foo1 and
>> foo2, p, q's copy in both foo1 and foo2 still points to both a and b.
>>
>>
>>
>> int a, b;
>>
>> int c;
>>
>>
>>
>> int foo1()
>>
>> {
>>
>> int *m;
>>
>> bar(m, &a);
>>
>> *m += a;
>>
>> *m += b;
>>
>> return *m;
>>
>> }
>>
>>
>>
>> int foo2()
>>
>> {
>>
>> int *n;
>>
>> bar(n, &b);
>>
>> *n += a;
>>
>> *n += b;
>>
>> return *n;
>>
>> }
>>
>>
>>
>> void bar(int *p, int *q)
>>
>> {
>>
>> *q = c;
>>
>> *p = q;
>>
>> }
>>
>>
>>
>> Because nystrom happens before inline, in bar function, p and q’s cg node
>> still points to both a and b.
>>
>> After inline bar into foo1 and foo2, p and q's dereference WN node's
>> constraint graph node still points to both a and b.
>>
>> They needs to be updated accordingly to get better points to accuracy.
>>
>> This patch add context sensitive inline to handle this problem.
>>
>> 1. When inline process formals, check if actual's points to set is
>> accurate than formal's points to set. If so, clone formal's cg node in
>> caller, update with actual's point to set.
>>
>> 2. After finish processing all formals, solve the nodes in callee
>> constraint graph , the initial work set is all formals updated in step1.
>>
>> No need propagate the updated points to back to caller (like propagate p
>> points to a, back to m only points to a), because nystrom context sensitive
>> will handle this.
>>
>>
>>
>> In context insensitive analysis (current implementation), m and n’s
>> constraint graph node in foo1 and foo2 will points to a and b, because in
>> bar p is assigned both a and b.
>>
>> Context sensitive analysis will summarize bar’s side effect <*p = q>, *q = c
>> is not pointer update, will not affect the points to info.
>>
>> when analyze foo1 and foo2 use this summary, foo1 knows m points to a, in
>> foo2, knows n points2 to b.
>>
>> But context sensitive can't solve this problem.
>>
>>
>>
>> Best Regards
>>
>> Shi, Hui
>>
>>
>>
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>>
>
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