9.2.3.2 Compound Lvalues

Currently compound lvalues involving array and structure field references are not broken down; an expression like a.b[2] = 42 is not reduced any further (though complex array subscripts are). This restriction is a workaround for limitations in later optimizers; if we were to convert this to

       T1 = &a.b;
       T1[2] = 42;

alias analysis would not remember that the reference to T1[2] came by way of a.b, so it would think that the assignment could alias another member of a; this broke struct-alias-1.c. Future optimizer improvements may make this limitation unnecessary.