The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the __builtin_darn intrinsic into a single call, thus reducing the entropy of the random number generator. This occurred because a volatile operation was not specified. For example, within a single execution of a program, the output of every __builtin_darn() call may be the same.
The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Gcc | Gnu | * | 7.5.0 (excluding) |
| Gcc | Gnu | 8.0 (including) | 8.4.0 (excluding) |
| Gcc | Gnu | 9.0 (including) | 9.3.0 (excluding) |
| Gcc | Gnu | 10.0 (including) | 10.1.0 (excluding) |