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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117048 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-10-21 19:01:22 +00:00
parent 1e93466c3a
commit de38897cfc
1 changed files with 23 additions and 3 deletions
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26
lib/Analysis/TypeBasedAliasAnalysis.cpp
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@ -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.
//
//===----------------------------------------------------------------------===//