diff options
| -rw-r--r-- | llvm/include/llvm/Target/TargetRegisterInfo.h | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/llvm/include/llvm/Target/TargetRegisterInfo.h b/llvm/include/llvm/Target/TargetRegisterInfo.h index ff5147e6f1b..4a5db1288d8 100644 --- a/llvm/include/llvm/Target/TargetRegisterInfo.h +++ b/llvm/include/llvm/Target/TargetRegisterInfo.h @@ -161,8 +161,21 @@ public: } /// Returns a bit vector of subclasses, including this one. - /// The vector is indexed by class IDs, see hasSubClassEq() above for how to - /// use it. + /// The vector is indexed by class IDs. + /// + /// To use it, consider the returned array as a chunk of memory that + /// contains an array of bits of size NumRegClasses. Each 32-bit chunk + /// contains a bitset of the ID of the subclasses in big-endian style. + + /// I.e., the representation of the memory from left to right at the + /// bit level looks like: + /// [31 30 ... 1 0] [ 63 62 ... 33 32] ... + /// [ XXX NumRegClasses NumRegClasses - 1 ... ] + /// Where the number represents the class ID and XXX bits that + /// should be ignored. + /// + /// See the implementation of hasSubClassEq for an example of how it + /// can be used. const uint32_t *getSubClassMask() const { return SubClassMask; } |
