Simplify multiple-of-element size access to arrays

[tautschnig]

Array operations may fall back to byte_extract or byte_update expressions in parts of the code base. Simplify this to index or WITH expressions, respectively, when the offset is known to be a multiple of the array-element size.

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[codecov]

Codecov Report

Attention: Patch coverage is 92.76316% with 11 lines in your changes missing coverage. Please review.

Project coverage is 80.38%. Comparing base (3c915eb) to head (ba35ebf).

Files with missing lines	Patch %	Lines
src/util/simplify_expr.cpp	93.93%	6 Missing ⚠️
src/util/pointer_offset_size.cpp	90.56%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #8627    +/-   ##
=========================================
  Coverage    80.37%   80.38%            
=========================================
  Files         1686     1686            
  Lines       206885   207022   +137     
  Branches        73       73            
=========================================
+ Hits        166276   166405   +129     
- Misses       40609    40617     +8     

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[remi-delmas-3000]

Is there a way to share some of the pattern matching conditions between the array-read and array-write cases ?

[remi-delmas-3000]

Seems like we should also be able to pattern match an access to a member of a struct in an array of structs like a[i].m, the offset would be of the form i*sizeof(T) + offset(T,m) and turn that into a functional update as well ?

[tautschnig]

Seems like we should also be able to pattern match an access to a member of a struct in an array of structs like a[i].m, the offset would be of the form i*sizeof(T) + offset(T,m) and turn that into a functional update as well ?

Done.