Finding a relevant place for a custom GCC pass

[Sandeep K Chaudhary <babbusandy2006@gmail.com>]

Hi guys,

I want to write a pass which can find the calculations performed on
the right hand side of each statement. In the below example -

        VAR1 = 1;
        VAR1++;
        VAR1 = VAR1 + 5;

I want to be able to capture the equivalent statements i.e.

VAR1 = 1;
VAR1 = 2;
VAR1 = 7;

To achieve this, I dumped various intermediate files using
"-fdump-tree-all'. I looked at all of them manually and found that
either the statements are non-evaluated (during initial stages) or
they are completely optimized, hence losing the intermediate
assignment calculations (during later stages). There is no pass which
generates dumps related to the intermediate assignment calculations.

I am not able to understand where I should aim to place my pass in
order to achieve the above mentioned functionality. Initially, I had
thought of writing IPA pass but I looked at 'copyprop' and 'forwprop'
dumps and saw that everything is optimized to the last statement. I am
not able to understand how a pass should be placed between GIMPLE
stage and later stages so that intermediate calculations such as the
ones mentioned above in the example, can be captured. Please provide
suggestions and help regarding this.

Thanks a lot in advance !

Regards,
Sandeep Chaudhary.