[Windows] Use information from the PE32 exceptions directory to construct…

Authored by aleksandr.urakov on Oct 11 2019, 2:03 AM.


[Windows] Use information from the PE32 exceptions directory to construct unwind plans

This patch adds an implementation of unwinding using PE EH info. It allows to
get almost ideal call stacks on 64-bit Windows systems (except some epilogue
cases, but I believe that they can be fixed with unwind plan disassembly
augmentation in the future).

To achieve the goal the CallFrameInfo abstraction was made. It is based on the
DWARFCallFrameInfo class interface with a few changes to make it less

To implement the new interface for PECOFF object files the class PECallFrameInfo
was written. It uses the next helper classes:

  • UnwindCodesIterator helps to iterate through UnwindCode structures (and processes chained infos transparently);
  • EHProgramBuilder with the use of UnwindCodesIterator constructs EHProgram;
  • EHProgram is, by fact, a vector of EHInstructions. It creates an abstraction over the low-level unwind codes and simplifies work with them. It contains only the information that is relevant to unwinding in the unified form. Also the required unwind codes are read from the object file only once with it;
  • EHProgramRange allows to take a range of EHProgram and to build an unwind row for it.

So, PECallFrameInfo builds the EHProgram with EHProgramBuilder, takes the ranges
corresponding to every offset in prologue and builds the rows of the resulted
unwind plan. The resulted plan covers the whole range of the function except the

Reviewers: jasonmolenda, asmith, amccarth, clayborg, JDevlieghere, stella.stamenova, labath, espindola

Reviewed By: jasonmolenda

Subscribers: leonid.mashinskiy, emaste, mgorny, aprantl, arichardson, MaskRay, lldb-commits, llvm-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D67347

llvm-svn: 374528