[PM] Edit comments in PassManager.h.
Summary:
This covers most of PassManager.h, up to the introduction of inner/outer
analysis proxies.
If there's a theme to these changes, it's simplifying the language. For
example:
* PreservedAnalyses is a "set of analyses", not an "abstract set".
"Abstract" doesn't have any particular meaning here.
* "Build types for the concept types" becomes "define the concept types".
* Instead of "data structures optimized for pointer-like types using
the alignment-provided low bits", say "data structures that use the
low bits of pointers."
* "Clear the map pointing into the results list" becomes
"Delete the map entries that point into the results list."
This patch also fixes a few places where we referred to "function" and
"module" pass/analysis managers, instead of the more abstract "IRUnitT"
PM/AMs we have now.
Subscribers: mehdi_amini
Differential Revision: https://reviews.llvm.org/D27367
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291040
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