[all-commits] [llvm/llvm-project] c53c20: Cache uwnind frame headers as they are found.

[Sterling-Augustine via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: c53c2058ffb8ff877702bb2dded31c85c1dfe66d
      https://github.com/llvm/llvm-project/commit/c53c2058ffb8ff877702bb2dded31c85c1dfe66d
  Author: Sterling Augustine <saugustine at google.com>
  Date:   2020-03-12 (Thu, 12 Mar 2020)

  Changed paths:
    M libunwind/src/AddressSpace.hpp
    A libunwind/src/FrameHeaderCache.hpp
    A libunwind/test/frameheadercache_test.pass.cpp

  Log Message:
  -----------
  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