diff options
| -rw-r--r-- | lib/Analysis/TypeBasedAliasAnalysis.cpp | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp index 5994ffd702..1cc743a382 100644 --- a/lib/Analysis/TypeBasedAliasAnalysis.cpp +++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp @@ -21,9 +21,29 @@ // This is a work-in-progress. It doesn't work yet, and the metadata // format isn't stable. // -// TODO: getModRefBehavior. The AliasAnalysis infrastructure will need to -// be extended. -// TODO: struct fields +// The current metadata format is very simple. MDNodes have up to three +// fields, e.g.: +// !0 = metadata !{ !"name", !1, 0 } +// The first field is an identity field. It can be any MDString which +// uniquely identifies the type. The second field identifies the type's +// parent node in the tree, or is null or omitted for a root node. +// If the third field is present, it's an integer which if equal to 1 +// indicates that the type is "constant". +// +// TODO: The current metadata encoding scheme doesn't support struct +// fields. For example: +// struct X { +// double d; +// int i; +// }; +// void foo(struct X *x, struct X *y, double *p) { +// *x = *y; +// *p = 0.0; +// } +// Struct X has a double member, so the store to *x can alias the store to *p. +// Currently it's not possible to precisely describe all the things struct X +// aliases, so struct assignments must use conservative TBAA nodes. There's +// no scheme for attaching metadata to @llvm.memcpy yet either. // //===----------------------------------------------------------------------===// |