| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
As with all type optimizations, MinimizeRecGroups only changes private
types, which are the only types that are safe to modify. However, it is
important for correctness that MinimimizeRecGroups maintain separate
type identities for all types, whether public or private, to ensure that
casts that should differentiate two types cannot change behavior.
Previously the pass worked exclusively on private types, so there was
nothing preventing it from constructing a minimial rec group that
happened to have the same shape, and therefore type identity, as a
public rec group. #6886 exhibits a fuzzer test case where this happens
and changes the behavior of the program.
Fix the bug by recording all public rec group shapes and resolve
conflicts with these shapes by updating the shape of the conflicting
non-public type.
Fixes #6886.
|
|
|
Most of our type optimization passes emit all non-public types as a
single large rec group, which trivially ensures that different types
remain different, even if they are optimized to have the same structure.
Usually emitting a single large rec group is fine, but it also means
that if the module is split, all of the types will need to be repeated
in all of the split modules. To better support this use case, add a pass
that can split the large rec group back into minimal rec groups, taking
care to preserve separate type identities by emitting different
permutations of the same group where possible or by inserting unused
brand types to differentiate them.
|
