What does `Simple_Compare` mean in type info flags?

Explain
1

Self explanatory. One of the enumerations in Type_Info_Flag is Simple_Compare. What does this signify, and how is it different from Comparable?

How come this flag being not present makes Odin runtime set equal_proc in Type_Info_Struct and Type_Info_Union be set?

2

Simple_Compare is set for types that the CPU can directly compare, if you take a peek into the compiler source these types are:

// types.cpp
enum BasicFlag {
    // ...
    BasicFlag_SimpleCompare  = BasicFlag_Boolean | BasicFlag_Numeric | BasicFlag_Pointer | BasicFlag_Rune,
};

For all other types it requires to do the equivalent of core:mem’s mem.compare_ptrs(&value1, &value2, size_of(value1)) == 0 when you test for equality.

Comparable is valid for both simple types (Simple_Compare) and for types for which all elements/members are comparable.

E.g. a struct { x, y: int} is comparable because

  • all members are ints which are themselves comparable
  • int is comparable because they are Simple_Compare

If you wanna explore in more detail check for bool is_type_comparable(Type *t) in the compiler source types.cpp.

Note: unlikely that names will change, but this is from commit 3229f4668df.