Re-implement caching for the linkage calculation of declarations.
My previous attempt at solving the compile-time problem with many
redeclarations of the same entity cached both linkage and visibility,
while this patch only tackles linkage. There are several reasons for
this difference:
- Linkage is a language concept, and is evaluated many times during
semantic analysis and codegen, while visibility is only a
code-generation concept that is evaluated only once per (unique)
declaration. Hence, we *must* optimize linkage calculations but
don't need to optimize visibility computation.
- Once we know the linkage of a declaration, subsequent
redeclarations can't change that linkage. Hence, cache
invalidation is far simpler than for visibility, where a later
redeclaration can completely change the visibility.
- We have 3 spare bits in Decl to store the linkage cache, so the
cache doesn't increase the size of declarations. With the
visibility+linkage cache, NamedDecl got larger.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@121023 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed