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Tree CONSTRUCTORs and Ada array indices


Hi,

I'm having fun with arrays in Ada ;) and wondering if anyone can tell me what's right here.

Ada ACATS c64106a contains code with an array type whose indices run from -1 to 1. (That is, three elements.)

In GCC this gets represented as an ARRAY_TYPE, whose TYPE_DOMAIN is a 32-bit signed integer type; the TYPE_MAX_VALUE of this is 1 (as a size_int), the TYPE_MIN_VALUE of this is -1 as a size_int, i.e. 4294967295. I believe using (unsigned 32-bit) size_int for min/max is correct (?) despite the domain being a signed type.

An array of this type is then initialized with a CONSTRUCTOR. The CONSTRUCTOR has three elements, with INTEGER_CST indices, being in order 2^32-1, 0, 1 (all of sizetype).

I substitute the CONSTRUCTOR into an ARRAY_REF <blah>[4294967295]{lb: 4294967295 sz: 2}, i.e. that picks the element with index (sizetype)2^32-1.

fold() in fold-const.c then fails to fold, because it does binary search for 2^32-1 through the constructor elements, and first checks against the middle CONSTRUCTOR_ELT, which has index 0.

So, where's the bug here? Should all these indices have sizetype? Should fold-const.c's binary search respect the TYPE_DOMAIN of the type of the CONSTRUCTOR being searched? (Lots of build_int_cst to reinterpret the CONSTRUCTOR_ELT indices, and/or the index being searched for, in said TYPE_DOMAIN ?)

Advice appreciated!

Thanks, Alan


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