add some notes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45854 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index ac56a7d488a42d4f6fba6d871fe0ee1333b7a6f9..f39d8b2a244bf2af89f180d6699d1e12692fec9d 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -595,3 +595,21 @@ to make it so the scheduler doesn't need to hold all the loads in regs at
 once.
 
 //===---------------------------------------------------------------------===//
+
+We should extend parameter attributes to capture more information about
+pointer parameters for alias analysis.  Some ideas:
+
+1. Add a "nocapture" attribute, which indicates that the callee does not store
+   the address of the parameter into a global or any other memory location
+   visible to the callee.  This can be used to make basicaa and other analyses
+   more powerful.  It is true for things like memcpy, strcat, and many other
+   things, including structs passed by value, most C++ references, etc.
+2. Generalize readonly to be set on parameters.  This is important mod/ref 
+   info for the function, which is important for basicaa and others.  It can
+   also be used by the inliner to avoid inserting a memcpy for byval 
+   arguments when the function is inlined.
+
+These functions can be inferred by various analysis passes such as the 
+globalsmodrefaa pass.
+
+//===---------------------------------------------------------------------===//