OpenChess

I am using 2d array of structures
{
uint8 flags;
uint8 delta;
}attack_t;
for attack detection,indexed by [sq][target]. What puzzles me is the intel IA32's translation.
It appears that if I don't use an auxiliary array of pointers, it will be referenced BYTE PTR [_attack_vector+edi+ebp*2],
when the purpose is BYTE PTR [esi+ecx*2]. Every other compiler I tried, including the intel's x64, MSVC 32;64, and so on, made it without ptr array. To be more clearly, here is what I mean in practice.
After reversing the direction in the attack_vector (-dir), I am able to use the reverse indexing [target][sq], since 'sq' is the only dynamically updated value of both.
&attack_t *a = &attack_vector[target][0]; - as a local pointer.
Then 'a[sq].flags, a[sq].delta' is my way to reference the array trough the local pointer. Every other compiler with Od, O2, O3 and so on translate this into BYTE PTR [esi+ecx*2] except intel x86.
The use of auxiliary array of pointers to the attack vector rows, eliminates this issue and the code is equivalent for all compilers. Any ideas? Thanks.

In C &attack_vector[0] and attack_vector are equivalent attack_t* expressions. No need to declare and initialize an explicit array of pointers for that, you have that implicit whithout the need of an additional indirection. If "sq" varies more than "target" and is power of two range, it makes indeed sense to use "sq" as least significant index.

What the compiler makes out of this is another question, but you need to post a bit more assembly (and associated C code) to recognice the content of the registers. There are several equivalent x86 addressing modes and expressions to build an effective address, AGU versus ALU.

Gerd