At the call graph level, only sibling SCCs can be parallelized. Clangs BackendUtil.cpp shows examples of a frontend adding (mostly [llvm-stress] Remove dependency to legacy pass manager. AMDGPUTargetMachine::registerPassBuilderCallbacks() is an example of a References assert(), N, and llvm::PMTopLevelManager::PassManagers. To do so, the pass manager must cache results and recompute them when they are invalidated by transforms. By inheriting this class we allow the entire module to be analyzed at once. A related limitation is that outer level IR analyses When the PassManager is destroyed, the pass will be destroyed as well, so there is no need to delete the pass. llvm::legacy::PassManagerImpl::PassManagerImpl, void llvm::legacy::PassManagerImpl::getAnalysisUsage, MPPassManager* llvm::legacy::PassManagerImpl::getContainedManager, char llvm::legacy::PassManagerImpl::ID = 0. LoopStandardAnalysisResults parameter. manager that only provides function-level analyses. Definition at line 484 of file LegacyPassManager.cpp. For example. the result is still valid, it will return that. Create first pass manager. inner pass manager finishes, so accessing mutable analyses would give invalid This is a great entry point into LLVM, please ask on llvm-dev for more information if youre interested. For example, frontends may want to add instrumentation, and target Users of a pass manager builder can add plugins that register parsing callbacks to handle custom out-of-tree passes. The legacy PM has been in use for a very long time and did its job fairly well. infrastructure to cache analyses and reuse them when possible. The backend codegen pipeline still works only with the legacy PM, mostly because most codegen passes dont work on LLVM IR, but rather machine IR (MIR), and nobody has yet put in the time to create the new PM infrastructure for MIR passes and to migrate all of the backends to use the new PM. This will be removed once the legacy pass manager is deprecated and removed for However, the typical use case is to run a predetermined pass pipeline. Common up the -debug-pass-manager option between LTOCodeGenerator, llvm-lto (which uses LTOCodeGenerator), and llvm-lto2 (which does not use LTOCodeGenerator but uses libLLVMLTO). FunctionAnalysisManager from a CGSCCAnalysisManager, you can call, and use FAM as a typical FunctionAnalysisManager that a function pass of optimization. In contrast. example, a FunctionPassManager is a function pass, meaning it can be simply forwards the invalidation to the inner analysis manager. For example, when we invalidate all analyses in a module pass, on. add . DomTreeUpdater for a DominatorTree. // This one corresponds to a typical -O2 optimization pipeline. Each pass is responsible for assigning a pass manager to itself. C++ source code API documentation for LLVM. This works for many In this case I've dropped the use-new-pm option entirely, as I don't think this is considered part of the public interface. Some passes only use analyses if they are cached, so parallelization can cause non-determinism since a module analysis may or may not exist based on other parallel pipelines. module. managers created by that PassBuilder. A pass manager is also responsible for managing analysis results. complete with a makefile. To use the legacy pass manager with opt, pass the -enable-new-pm=0 flag to all opt invocations. This implies that all passes MUST be allocated with 'new'. TargetPassConfig::addCodeGenPrepare(). This should generally only be used when This has the downside of needing to make sure that certain higher-level analyses are present before running a lower-level pipeline, e.g. Say we first visit foo, then visit bar and remove the dead call. GlobalsAA is the only module-level alias analysis and it generally is not Closed Public. IR passes can result in quadratic compile time behavior. HelloWorld.cpp: However, the legacy CGSCC pass manager only stored the functions in the current SCC in memory and did not have a persistent call graph data structure to use as keys to cache analyses. // Clear the entry in the analysis manager for function F2 if we've completely removed it from the module. For example, an SCC pass may want to look at function Pass Manager itself does not invalidate any analysis info. This discounts future concurrency over separate loops in a function, but Many passes hadnt yet been ported to the new PM and some opt features didnt work with the new PM. A CGSCC pass runs on a specific strongly connected component (SCC) of the call graph. References llvm::PMDataManager::setTopLevelManager(). Harbormaster completed remote builds in B124736: Diff 373689. PassBuilder::buildPerModuleDefaultPipeline() which creates a typical backend adding passes to various parts of the pipeline. The inner proxys invalidate() first checks For example, opt rG0ef404a9f993: [llvm-stress] Remove dependency to legacy pass manager. Currently there are efforts to make the codegen pipeline work with the new Creating SCCs on demand makes it hard to find sibling SCCs. Then hopefully at some point we can start to remove parts of the optimization pipeline that are legacy PM-specific. ( #include "llvm/IR/LegacyPassManager.h") llvm::PassManager is actually a class template. includes anything added via TargetPassConfig hooks, e.g. runOnFunction for DominatorTree is called by pass manager before returning a reference to . cases, PassBuilder exposes callbacks that allow injecting passes into The specific motivating use case was that the inliner wanted to look at the profile data of callees recursively, especially in regards to deferred inlining where the inliner wants to look through simple wrapper functions. I suspect that my group is not the only ones trying to stay in sync with the upstream LLVM main branch and keep using the legacy pass manager, and I anticipate the only long-term remedy for. (PAC.preserved() || PAC.preservedSet>()); // Check whether the analysis has been explicitly invalidated. // Invalidate all analysis results for function F1. For more details, see Writing an LLVM Pass and Using the New Pass Manager. transformation, or tell the analysis manager that analyses are no longer Loop passes often use function analyses such For things like functions and loops, we have persistent data structures for those to use as keys. llvm::legacy::PassManagerImpl Class Reference. When the PassManager is destroyed, the pass will be destroyed as well, so there is no need to delete the pass. However, smaller applications with tiny hotspots likely wont see much benefit from the new PM since the improvements brought on by the new PM tend to be more relevant to large codebases. Although there has been work to start making the codegen pipeline work with the new PM, it is still very far from being usable. Other mutable function analyses are PassManager manages ModulePassManagers. cached/invalidated, you can mark the analysis manager proxy as preserved, This is better for cache locality around LLVM data structures. PassManager llvm-project\llvm\include\llvm\IR\LegacyPassManager.h This also removes the ability to run arbitrary sets of passes. In order for a pass to communicate that analyses have been invalidated, it returns which analyses it has preserved. Not sure if this functionality is used, but it doesn't seem to be tested. Clang dropped legacy PM support . they are LLVM IR passes (whereas all MIR passes are codegen passes). analyses are also invalidated. later loop to be able to be optimized more than if each loop pass were run adaptor that goes through all the loops in the function and runs the loop To add a pass to a new PM pass manager, the important thing is to match the // Invalidate all analysis results across the entire module. References llvm::PMTopLevelManager::dumpArguments(), llvm::PMTopLevelManager::dumpPasses(), getContainedManager(), llvm::PMTopLevelManager::getImmutablePasses(), llvm::PMTopLevelManager::getNumContainedManagers(), Index, llvm::PMTopLevelManager::initializeAllAnalysisInfo(), and M. Referenced by llvm::legacy::PassManager::run(). possible for some inner analysis to depend on some outer analysis, and when You can also ask the analysis manager to only return an analysis if its LLVM distinguishes between analysis and transformation passes. Keep track of whether any of the passes modifies the module, and if so, return true. getPassID - Return the PassID number that corresponds to this pass. getAdjustedAnalysisPointer - This method is used when a pass implements an analysis interface through multiple inheritance. we have to make sure that we also invalidate function analyses accessible via Inheritance diagram for llvm::legacy::PassManagerImpl: Collaboration diagram for llvm::legacy::PassManagerImpl: llvm::PMTopLevelManager::getImmutablePasses(), llvm::PMTopLevelManager::getNumContainedManagers(), llvm::PMTopLevelManager::initializeAllAnalysisInfo(). But we need some way for a pass manager builder to be aware of all passes for testing purposes. It turns out that the new PM CGSCC infrastructure didnt support extracting parts of a function into another (aka outlining) in a CGSCC pass. If an analysis is stateless and generally shouldnt be invalidated, use the We ported passes and features that made sense to port to the new PM, and pinned tests using legacy PM features that didnt make sense to port to the new PM. as described below). certain parts of the pipeline. 2022-05-12 :: Neil Henning. This passes ownership of the Pass to the PassManager. FunctionPass2 on each function in the module. 3. what the pass runs on. Some of the more interesting issues with the new PM uncovered with -enable-new-pm: Various projects/companies have already been using the new PM for performance reasons for many years. Currently the new PM applies only to the middle-end optimization pipeline working with LLVM IR. Find the pass that implements Analysis AID. Alias analysis is a function-level analysis, but there are passes which work on a fixed scope. Passes can run on an entire module, a single function, or something more abstract such as a strongly connected component (SCC) in a call graph or a loop inside of a function. deleted IR. Inheritance diagram for llvm::legacy::PassManagerBase: llvm::TargetPassConfig::addCheckDebugPass(), llvm::TargetPassConfig::addDebugifyPass(), llvm::DirectXTargetMachine::addPassesToEmitFile(), llvm::LLVMTargetMachine::addPassesToEmitFile(), llvm::LLVMTargetMachine::addPassesToEmitMC(), llvm::TargetPassConfig::addStripDebugPass(), llvm::HexagonTargetMachine::adjustPassManager(), llvm::BPFTargetMachine::adjustPassManager(), llvm::AMDGPUTargetMachine::adjustPassManager(), llvm::NVPTXTargetMachine::adjustPassManager(), legacy::PassManagerBase::~PassManagerBase, virtual void llvm::legacy::PassManagerBase::add. Self-updating analyses that gracefully degrade also handle Major differences: and they block potential future concurrency. This pass is also subject to proper nesting. (. manually within the pass: One thing to note when accessing inner level IR analyses is cached results for invalidated so this is not so much of a concern. All Required analyses should be available to the pass as it runs! Add a pass to the queue of passes to run. if the proxy itself should be invalidated. separately. llvm/lib/IR/LegacyPassManager.cpp Go to file Go to fileT Go to lineL Copy path Copy permalink Cannot retrieve contributors at this time 2057 lines (1702 sloc) 67 KB Raw Blame Open with Desktop View raw View blame Migrating to the new PM for the codegen pipeline likely wont unlock performance gains since there are almost no interprocedural codegen passes. Definition at line 39 of file LegacyPassManager.h. different ways of loading dynamic pass plugins. 2,613 5 30 27. It should be llvm::legacy::PassManager instead of just llvm::PassManager. For example, a module results. pass on each one. Requiring the CGSCC nesting was considered to simplify things, but the extra runtime overhead of building the call graph and the extra code for proper nesting to run function passes was enough to make the CGSCC nesting optional. Referenced by codegen(), llvm::MCJIT::emitObject(), llvm::lintModule(), and llvm::orc::SimpleCompiler::operator()(). Populate UsedPasses with analysis pass that are used or required by pass P and are available. This works for LLVM 6 which is pretty recent (march 2018). This is the complete list of members for llvm::legacy::PassManagerImpl, including all inherited members. Definition at line 502 of file LegacyPassManager.cpp. These invalidations happen after the dominator tree) should be shared between passes whenever possible for efficiency reasons, since recomputing analyses can be expensive. For example, a function pass receives an analysis // Register all the basic analyses with the managers. When referring to "legacy PM" and "new PM", this includes all of the surrounding infrastructure, not just the entity that manages passes. will add FooPass near the very beginning of the pipeline for pass The typical way to invalidate analysis results is for a pass to declare what added to a ModulePassManager: Generally you want to group CGSCC/function/loop passes together in a pass Does the <value> here mean built-in pass names like `dce`/`mem2reg`, The LLVM compiler infrastructure (https://llvm.org/) provides all means to write custom compiler passes.
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