Peter Collingbourne e6909c8e8b Introduce bitset metadata format and bitset lowering pass. ... This patch introduces a new mechanism that allows IR modules to co-operatively build pointer sets corresponding to addresses within a given set of globals. One particular use case for this is to allow a C++ program to efficiently verify (at each call site) that a vtable pointer is in the set of valid vtable pointers for the class or its derived classes. One way of doing this is for a toolchain component to build, for each class, a bit set that maps to the memory region allocated for the vtables, such that each 1 bit in the bit set maps to a valid vtable for that class, and lay out the vtables next to each other, to minimize the total size of the bit sets. The patch introduces a metadata format for representing pointer sets, an '@llvm.bitset.test' intrinsic and an LTO lowering pass that lays out the globals and builds the bitsets, and documents the new feature. Differential Revision: http://reviews.llvm.org/D7288 llvm-svn: 230054		2015-02-20 20:30:47 +00:00
..
llvm	Introduce bitset metadata format and bitset lowering pass.	2015-02-20 20:30:47 +00:00
llvm-c	[BDCE] Add a bit-tracking DCE pass	2015-02-17 01:36:59 +00:00