Cache uwnind frame headers as they are found.

Summary:
This improves unwind performance quite substantially, and follows
a somewhat similar approach used in libgcc_s as described in the
thread here:

https://gcc.gnu.org/ml/gcc/2005-02/msg00625.html

On certain extremely exception heavy internal tests, the time
drops from about 80 minutes to about five minutes.

Subscribers: libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D75954

GitOrigin-RevId: c53c2058ffb8ff877702bb2dded31c85c1dfe66d
3 files changed
tree: 5babb6ff1c8c55072a31fb8c811cf6527aa4cc4a
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT