How to write/read tree contains ssa_name in lto

[Richard Biener]

On Tue, Oct 14, 2025 at 2:51 PM ywgrit <yw987194828@gmail.com> wrote:
>
>
>
> Richard Biener <richard.guenther@gmail.com> 于2025年10月14日周二 20:31写道：
>>
>> On Tue, Oct 14, 2025 at 2:22 PM ywgrit <yw987194828@gmail.com> wrote:
>> >
>> > A program may consist of multiple compilation units, and multiple array access operations may exist within the program.
>> > In SIMPLE_IPA_PASS, I want to check whether the index is consistent during two array accesses: During the first pass through all functions, traverse all gimples, record each array access operation, and store its corresponding {Function *, index} into a hash_set. During the second pass through all functions, when encountering the array access operation we wish to process, search for {Function *, index} in the hash_set.
>> > Converting SIMPLE_IPA_PASS to IPA_PASS presents challenges.
>> > Since Function * is a pointer, direct transfer is meaningless. index is an ssa_name, so direct transfer is also impossible. My question is: Since the above approach fails, if I encounter an array access operation during the wpa phase, how should I determine whether there exists another array access operation within the same function that shares the same index?
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>> You have to split the pass into local analysis pre-WPA which would
>> need to compute this (while it has access
>> to the body of the function) a "merge" operation during WPA and a
>> transform during LTRANS.
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>  Is pre-WPA the generate phase?

LGEN, yes.

>> Note
>> that comparing SSA names itself between functions is meaningless,
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>  Is this because ssa_name is bound to the function? i.e., function->gimple_df->ssaname.

Because they are function-local entities, yes.

>> I'm
>> guessing you want to
>> compute the array access index based on function parameters?
>>
> When I encounter an array access, assuming this array access occurs within function func_a, I want to know if there are other array accesses with the same index within func_a.

OK, but how does IPA come into play here?  You can do this fully
local, for example
as said during LGEN.

Richard.

>>
>> Richard,
>>
>> > Thanks.
>> >
>> > ywgrit.
>> >
>> > Richard Biener <richard.guenther@gmail.com> 于2025年10月13日周一 14:42写道：
>> >>
>> >> On Sat, Oct 11, 2025 at 10:32 AM ywgrit via Gcc <gcc@gcc.gnu.org> wrote:
>> >> >
>> >> > I used the functions stream_write_tree/stream_read_tree in lto. If tree
>> >> > contains ssa_name, then stream_read_tree will generate ice: cfun is null in
>> >> > wpa, so (*SSANAMES (cfun))[ix] will break the program. How to write/read
>> >> > tree contains ssa_name in lto, e.g., wpa phase?
>> >>
>> >> You shouldn't - you have to abstract from this somehow as during WPA phase
>> >> a SSA name doesn't make "sense".  That said, you have to elaborate a bit on
>> >> what you are trying to do.
>> >>
>> >> Richard.
>> >>
>> >> > Thanks.
>> >> >
>> >> > ywgrit.
>
> Thanks.
>
> ywgrit.