Dynamically loaded plugins for the new pass manager are initialised by
calling llvmGetPassPluginInfo. This is defined as a weak symbol so that
it is continually redefined by each plugin that is loaded. When loading
a plugin from a shared library, the intention is that
llvmGetPassPluginInfo will be resolved to the definition in the most
recent plugin. However, using a global search for this resolution can
fail in situations where multiple plugins are loaded.
Currently:
* If a plugin does not define llvmGetPassPluginInfo, then it will be
silently resolved to the previous plugin's definition.
* If loading the same plugin twice with another in between, e.g. plugin
A/plugin B/plugin A, then the second load of plugin A will resolve to
llvmGetPassPluginInfo in plugin B.
* The previous case can also occur when a dynamic library defines both
NPM and legacy plugins; the legacy plugins are loaded first and then
with `-fplugin=A -fpass-plugin=B -fpass-plugin=A`: A will be loaded as
a legacy plugin and define llvmGetPassPluginInfo; B will be loaded
and redefine it; and finally when A is loaded as an NPM plugin it will
be resolved to the definition from B.
Instead of searching globally, restrict the symbol lookup to the library
that is currently being loaded.
Differential Revision: https://reviews.llvm.org/D104916
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
Add a new plugin API. This closes the gap between pass registration and out-of-tree passes for the new PassManager.
Unlike with the existing API, interaction with a plugin is always
initiated from the tools perspective. I.e., when a plugin is loaded, it
resolves and calls a well-known symbol `llvmGetPassPluginInfo` to obtain
details about the plugin. The fundamental motivation is to get rid of as
many global constructors as possible. The API exposed by the plugin
info is kept intentionally minimal.
Reviewers: chandlerc
Reviewed By: chandlerc
Subscribers: bollu, grosser, lksbhm, mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D35258
llvm-svn: 329273
